Claims:We Claim:

1. An holographic weapon sight and method of preparing the optical elements therein, an apparatus comprising:
a laser diode (110), wherein a source for the laser beam emitting at 650 nm wavelength (115), is disposed perpendicularly to a reflective diffraction grating plate (125);
at least two holographic optical elements, which includes the reflective diffraction grating plate (125) and a transmission reticle hologram plate (130), wherein the said both holographic optical elements, further comprises of a transparent substrate, whereon coated with a silver halide holographic emulsion of thickness about 7-10 µm, whereby using a method holographic laser interference;
the said reflective diffraction grating plate (125), collimates and diffracts the incident laser beam from the laser diode (120), towards the transmission reticle hologram plate (130) at a desired degree of angular deviation;
the said transmission reticle hologram plate (130), is mounted parallel to the path of laser beam diffracted from the said reflective diffraction grating plate (125), wherein to receive the collimated laser beam (120) for the purpose of reconstruction, thereby illuminating a holographic reticle image (155) that is already recorded on the transmission reticle hologram plate (130);
the said holographic reticle image, further includes a substantially large outer circle (210) with four quadrant ticks (220), and a centre dot (230), wherein the centre dot (230) having the values of 1MOA/2 MOA for precise long range aiming for about 300 meters and the said outer circle (210) having a value of 65 MOA for short distance aiming purpose, thereby increasing the field of view and supporting the two eye open aiming;
a mechanical holder (140), wherein supports the reflective diffraction grating plate (125) by means of adjusting mechanism with at least two adjustable screws (145) to move in the x axis and y axis direction (145), so as to shift the laser beam in desired direction to control the holographic reticle image (155) position for the purpose of zeroing;
a tooth wheeler (150), wherein supports the laser diode (110) by means of slidable adjusting mechanism to move the laser diode (110) forward and backward on the same plane, so as to dispose the laser diode (110) at the focal point of the reflective diffraction grating plate (125) for the purpose of correcting the parallax error.

2. An holographic weapon sight and method of preparing the optical elements therein, as claimed in claim 1, wherein the steps for recording the holographic reticle image (155) on the transmission reticle hologram plate (130) includes:
splitting the laser beam of wavelength of 650nm (410), into two beams by a means of beam splitter (415), wherein one beam is a transmission reticle object beam (420) and another beam is a transmission reticle reference beam (425), wherein further transmitting the transmission reticle object beam (420) farther in a same direction to a first mirror (430), and redirecting the transmission reticle reference beam (425) to a second mirror (435);
reflecting the transmission reticle object beam (420) by first mirror (430) to the transmission reticle hologram plate (130), whereby passing through a first spatial filter (440), a reticle mask (450), and an imaging lens (455), wherein the said transmission reticle object beam (420) is spatially cleaned, expanded and carries the spatial information of the holographic reticle image (155);
reflecting the transmission reticle reference beam (425) by second mirror (435) at an angle 56 degree to the said transmission reticle hologram plate (130), whereby passing through a second spatial filter (445) and collimating lens, wherein the said transmission reticle reference beam (425) is spatially cleaned, expanded and collimated as a parallel beam;
recording the holographic image of a reticle (155) on the transmission reticle hologram plate (130), whereby exposing the transmission reticle object beam (420) that is passed from the reticle mask (450) and exposing the collimated transmission reticle reference beam on the transmission reticle hologram plate (130);
controlling the exposure time of the transmission reticle object beam (420) and transmission reticle reference beam (425) by means of an electronic shutter;

developing the exposed transmission reticle hologram plate (130) by a wet chemical process;
treating the chemically processed transmission reticle hologram plate (130) with 1% of potassium iodide solution for 10 minutes such as to provide a print-out free transmission reticle hologram plate (130); and
drying the treated transmission reticle hologram plate (130) at an ambient temperature.

3. An holographic weapon sight and method of preparing the optical elements therein, as claimed in claim 1, wherein the steps for recording the reflective diffraction grating plate, comprises of :
splitting the laser beam of wavelength of 650nm (505), into two beams by a means of beam splitter (510), wherein one beam is a diffraction grating object beam (515) and another beam is a diffraction grating reference beam (520), wherein further transmitting the diffraction grating object beam (515) farther to a first mirror (525) and redirecting the diffraction grating reference beam (520) to a second mirror (530);
reflecting the diffraction grating object beam (515) by first mirror (525) at an angle 56 degree to a reflective diffraction grating plate (125), whereby passing through a first spatial filter (535), wherein the said diffraction grating object beam (515) is spatially cleaned, and expanded;
collimating the diffracting grating object beam from the first mirror by means of the collimator (555), wherein the said diffraction grating object beam is incident on the opposite side of the reflective diffraction grating plate (550);
reflecting the diffraction grating reference beam (520) by second mirror (530) towards the front side of the reflective diffraction grating plate (545), whereon coated with the said holographic silver halide emulsion;
transmitting the reflected diffraction grating reference beam (520) to incident on the front side of reflective diffraction grating plate (545), whereby passing through a second spatial filter (540), wherein the said diffraction grating reference beam (520) is spatially cleaned, expanded, or diverged;
controlling the exposure time of the diffraction grating object beam (515) and diffraction grating reference beam (520) by means of an electronic shutter on the front side of the reflective diffraction grating plate (545) provided with silver halide emulsion;
developing the exposed reflective diffraction grating plate (125), by a wet chemical process;
treating the chemically processed reflective diffraction grating plate (125) with 1% of potassium iodide solution for 10minutes such as to provide a print-out free reflective diffraction grating plate (125); and
drying the treated reflective diffraction grating plate (125) at an ambient temperature.

4. An holographic weapon sight and method of preparing the optical element therein, as claimed in claim 1, wherein the silver halide hologram emulsion is provided with a substantially high resolution of 20000 lines/mm and the grain size of 4nm, being for recording the sharp holographic reticle image (155) on the transmission reticle hologram plate (130) and recording the interference of beam on one front side of reflective diffraction grating plate (545).

5. An holographic weapon sight and method of preparing the optical element therein, as claimed in claim 1, wherein the said reticle mask (450) is composed of chrome plate with substantially high density OD 5 and provided with the lines maintained at the micron level accuracy, wherein further the said transmission reticle object beam (420) passing through the reticle mask (450) records sharp and clear holographic reticle image (155) on the transmission reticle hologram plate (130).

6. An holographic weapon sight and method of preparing the optical elements therein, the apparatus as claimed in claim 1, wherein, the said laser light beam at 650nm wavelength (115) from the said laser diode (110) incident on front side of the reflective diffraction grating plate (125), is further collimated and diffracted at 560 angular deviation (120) towards the transmission reticle hologram plate (130) by the means of reflective diffraction grating plate (125), for the purpose of reconstructing, or illuminating the recorded reticle image (155) therein.

7. An holographic weapon sight and method of preparing the optical elements therein, the apparatus as claimed in claim 1, wherein the focal length of the said reflective diffraction grating plate (125) is 50 mm, and the laser diode (110) is disposed exactly at the focal point of the reflective diffraction grating plate (125).

8. An holographic weapon sight and method of preparing the optical elements therein, the apparatus as claimed in claim 1, wherein,
the holographic reticle image (155) shift is caused due to at least two factors, wherein the first factor is usage of at least two different wavelength of laser beam for the purpose of recording and reconstruction of the holographic material, and the second factor is an external temperature variation that shrinks or swells the silver halide emulsion coated transparent substrate of the holographic material;
so as to avoid the reticle hologram image (155) shift, the same holographic material, wherein includes the said transparent substrate coated with same silver halide, is used for recording the both transmission reticle hologram plate (130) and reflective diffraction grating plate (125); and
the laser beam with the wavelength of 650nm (410), (505) is used for recording both the holographic optical elements, and similar laser beam of wavelength 650nm(115) is used in the apparatus to reconstruct the reticle hologram image (155).

9. An holographic weapon sight and method of preparing the optical elements therein, the apparatus as claimed in claim 1, wherein the said transmission reticle hologram plate has a dual property, characterized as transparent view finder window (135) for viewing the target and superimposing the holographic reticle image (155) in the view finder window (135) being for of aiming the target.

10. An holographic weapon sight and method of preparing the optical elements therein, as claimed in claim 1, wherein, the said holographic elements are configured with a protecting glass for having high visible transmission of about 95%, wherein the said protecting glass are composed of an anti-reflective coating, wherein the said protecting glass wavelength is about 300nm to 700 nm.

11. An holographic weapon sight and method of preparing the optical elements therein, as claimed in claim 1, wherein the diffraction efficiency of transmission reticle hologram plate (130) is about 1% to 5%

12. An holographic weapon sight and method of preparing the optical elements therein, as claimed in claim 1, wherein the diffraction efficiency of reflective diffraction grating plate (125) is at least 60%.
, Description:Description

TITLE: An holographic weapon sight and method of preparing the optical elements, therein.
FIELD OF THE INVENTION
The present invention in general relates to holographic sighting devices and in particular, it relates to at least two holographic optical elements that shall be used on small firearms, bows, telescopes, and other applications where accurate aiming is necessary.
BACKGROUND OF THE INVENTION
Nowadays, there are several types of sights available in the market to enable a user of optical devices or weapons such as rifles, shotguns, handguns, and submachine guns to aim these weapons. Examples of such sighting devices include laser sights, holographic sights, “reflex,” or “red dot” sights etc. Some of the available sights have a laser as their light source. The light may be used to create an image of a reflex or red dot. However, these images are susceptible to drift due to a change in the output wavelength of the laser source because of changing environmental conditions and may introduce error in aiming a weapon/optical device.
Recently, laser diodes are used in a wide variety of applications that require a narrow spectral width. However, the wavelength of the light produced by the laser diode (LD) varies depending on a number of factors, including the shift in image position that happens because of using different wavelength for recording and reconstruction. This shift in wavelength will cause the holographic gun sight to be inaccurate.
In typical holographic gun sight, a holographic optical element (HOE) is illuminated by a reconstruction beam, from a laser diode, and reconstructs an image of a reticle as an object beam. The reconstruction beam typically does not illuminate the HOE perpendicular to the surface but instead is angled at a beam angle. Depending on how the HOE is made or recorded, the object beam is also at an angle to perpendicular. These angles are typically not equal (on opposite sides of perpendicular). In such a case, the actual object beam angle will vary depending on the wavelength of the reconstruction beam. As the wavelength of the reconstruction beam shifts, the diffraction angle from a holographic element will change, which will result in movement of the reconstructed holographic image and give an inaccurate reticle position relative to the target. To correct for this change in wavelength, some sights are configured such that the system of holographic optical elements form an achromatic to compensate for changes in wavelength.

EP3314196B1 – The hybrid holographic sight includes a light source operable to project a light beam along a path and a holographic optical element (HOE) disposed in the path of the light beam. The HOE reconstructs an image of a reticle and a non-diffraction element reflects the image of the reticle, whereby a user may view a reflection of the reconstructed reticle in the non-diffraction element (NDE), wherein in this existing prior art, four conventional optical elements are used as intermediate optics.

Another optical system of holographic sight is disclosed in the patent US20060164704. The system consists of a convex lens, a prism, a hologram and a grating. The system has relatively low height but has too long horizontal length. Moreover, the image position will vary with drifting laser wavelength.
The patent US6490060 describes a more complicated optical system wherein, the system consists of an LD (Laser diode), a reflector, an off-axis concave reflector, a holographic reflective grating and a hologram. The laser beam emitted by an LD is collimated by the concave reflector. The grating is used to filter the laser beam. This is a relatively successful system and has achieved practical application. However some elements present in this optical system is difficult to fabricate and expensive. Moreover, since the diffraction angles of reflective gratings are sensitive to temperature and moisture, the change of image position can hardly be completely eliminated.

US20110228366A1 – The optical system includes a laser diode, two mirrors, a holographic optical element (HOE) and a hologram, wherein additionally two conventional optics are added along with two holographic optical elements. Hence there is need of simple and compact design of holographic weapon sight, in which optical system that can collimate and filter a laser beam, can generate a clear and parallax-free holographic virtual reticle image, and can eliminate the displacement of the image so as to guarantee accurate aiming.
OBJECTIVE OF THE INVENTION
1. The primary objective of the present invention is to provide simple and compact design of holographic weapon sight for accurate aiming and firing of the target.
2. It is another objective of the present invention is to reduce design complexity of holographic weapon sight.
3. It is yet another objective of the present invention is to minimize the distance; travelling beam distance without using more number of optical elements.
4. It is another objective of the present invention is to reduce the size of the holographic weapon sight.
5. It is another objective of the present invention is to provide parallax-free holographic virtual image
6. It is another objective of the present invention is to avoid print-out free transmission reticle hologram.
7. It is another objective of the present invention is to provide holographic weapon sight with a feature of magnification of the image for long distance firing.
8. It is another objective of the present invention is to provide holographic weapon sight with reticle centre dot for long range distance accurate aiming.
9. It is another objective of the present invention is to provide holographic weapon view finder sight with circle with quadrant ticks for close combat firing.
10. It is another objective of the present invention is to provide holographic weapon sight with easy target aiming by means of sufficiently sized transmission reticle hologram.
12. It is another objective of the present invention is to provide holographic weapon sight to relieve from eye constraint, so that firing shall be operated with both eyes open.
13. It is yet another objective of the present invention is to eliminate displacement of reticle image that happens due to shift in wavelength and change in temperature.
14. It is another objective of the present invention is to fabricate holographic optical element by using same substrate material and grain silver halide emulsion coating thereon.
15. It is another objective of the present invention is to provide same wavelength of laser diode for recording and reconstruction of hologram.
16. It is another objective of the present invention is to avoid mismatching of reconstruction of wavelength in holographic weapon sight.
17. It is another objective of the present invention is to provide clear and sharp reticle image without speckle noise on the target plane.
18. It is another objective of the present invention is to use only holographic for collimating purpose.
19. It is another objective of the present invention is to make cost effective holographic weapon sight.
SUMMARY OF THE INVENTION
It will be understood that this disclosure is not limited to the particular methodologies described, as there can be multiple possible embodiments of the present disclosure which are not expressly illustrated in the present disclosure. It is also to be understood that the terminology used in the description is for the purpose of describing the particular versions or embodiments only, and is not intended to limit the scope of the present disclosure.
The present invention relates to the fabrication of a simple and compact holographic weapon sight for the purpose of accurate aiming and firing of the target that is capable of being used for close combat and long range firing.
In the preferred embodiment, an apparatus that is holographic weapon sight comprises of a laser diode and at least two holographic optical elements (HOE). Wherein, the holographic optical elements, includes a reflective diffraction grating plate and a transmission reticle hologram.
One aspect of the present invention, a laser diode being a source for the laser beam emitting at 650 nm wavelength that is disposed perpendicularly to a reflective diffraction grating plate.
It is another aspect of the present invention, wherein the said both the holographic optical elements, comprises of a transparent substrate, whereon coated with a silver halide holographic emulsion of thickness about 7-10µm, using a method holographic laser interference.
It is another aspect of the present invention, wherein the reflective diffraction grating plate, collimates and diffracts the incident laser beam from the laser diode, towards the transmission reticle hologram plate at a 560 of angular deviation.
It is another aspect of the present invention, wherein the transmission reticle hologram plate, is mounted parallel to the path of laser beam diffracted at an off axis 560 from the said reflective diffraction grating plate. Herein it is noted that the reflective diffraction grating collimates the incident beam to a collimated parallel laser beam.
The transmission reticle hologram plate, receives the collimated laser beam for the purpose of reconstruction, to illuminate a reticle image that is already recorded on the transmission reticle hologram.
It is another aspect of the present invention, wherein the said reticle image including a substantially large outer circle with four quadrant ticks, and a centre dot. It is further noted herein, that the centre dot is configured with the values of 1MOA/2 MOA for precise long range aiming about 300 meters and the said outer circle having a value of 65 MOA for short distance aiming purpose, thereby increasing the field of view and supporting the two eye open aiming.
It is yet another aspect of the present invention is a mechanical holder, which supports the reflective diffraction grating plate by means of adjusting mechanism with at least two adjustable screws (145) to move in the x axis and y axis direction, so as to shift the laser beam in desired direction to control the reticle image positioning for the purpose of zeroing.
It is yet another aspect of the present invention is a tooth wheeler, wherein supports the laser diode by means of slidable adjusting mechanism to move the laser diode forward and backward on the same plane, so as to dispose the laser diode at the focal point of the reflective diffraction grating plate for the purpose of correcting the parallax error.
In the preferred embodiment of the present invention, the apparatus holographic weapon sight comprises of at least two holographic elements such as transmission reticle hologram plate and reflective diffraction grating plate. Herein it is noted that the fabrication or recording of the two holographic elements are done using the same strength of laser beam having the wavelength of 650nm but with different methodology.
Herein it is further noted that the steps for recording the reticle hologram image on the transmission reticle hologram plate includes,
I. splitting the laser beam of wavelength of 650nm, into two beams by a means of beam splitter, wherein one beam is a transmission reticle object beam and another beam is a transmission reticle reference beam, wherein further transmitting the transmission reticle object beam farther in a same direction to a first mirror, and redirecting the transmission reticle reference beam to a second mirror;
II. reflecting the transmission reticle object beam by first mirror to the transmission reticle hologram plate, whereby passing through a first spatial filter, a reticle mask, and an imaging lens, wherein the said transmission reticle object beam is spatially cleaned, expanded and carries the spatial information of the reticle image;
III. reflecting the transmission reticle reference beam by second mirror at an angle 56 degree to the said transmission reticle hologram plate, whereby passing through a second spatial filter and collimating lens, wherein the said transmission reticle reference beam is spatially cleaned, expanded and collimated as a parallel beam;
IV. recording the holographic image of a reticle on the transmission reticle hologram plate, whereby exposing the transmission reticle object beam that is passed from the reticle mask and exposing the collimated transmission reticle reference beam on transmission reticle hologram plate;
V. controlling the exposure time of the transmission reticle object beam and transmission reticle reference beam by means of an electronic shutter;
VI. developing the exposed transmission reticle hologram plate by a wet chemical process;
VII. treating the chemically processed transmission reticle hologram plate with 1% of Potassium Iodide solution for 10minutes such as to provide a print-out free transmission reticle hologram plate; and
VIII. drying the treated transmission reticle hologram plate at an ambient temperature.
Herein it is noted, that the steps for recording reflective diffraction grating plate includes,
I. splitting the laser beam of wavelength of 650nm, into two beams by a means of beam splitter, wherein one beam is a diffraction grating object beam and another beam is a diffraction grating reference beam, wherein further transmitting the diffraction grating object beam farther to a first mirror and redirecting the diffraction grating reference beam to a second mirror;
II. reflecting the diffraction grating object beam by first mirror at an angle 56 degree to a reflective diffraction grating plate, whereby passing through a first spatial filter, wherein the said diffraction grating object beam is spatially cleaned, and expanded;
III. collimating the diffracting grating object beam from the first mirror by means of the collimator, wherein the said diffraction grating object beam is incident on the opposite side of the reflective diffraction grating plate;
IV. reflecting the diffraction grating reference beam by second mirror towards the front side of the reflective diffraction grating plate, whereon coated with the said holographic silver halide emulsion;
V. transmitting the reflected diffraction grating reference beam to incident on the front side of reflective diffraction grating plate, whereby passing through a second spatial filter, wherein the said diffraction grating reference beam is spatially cleaned, expanded, or diverged;
VI. controlling the exposure time of the diffraction grating object beam and diffraction grating reference beam by means of an electronic shutter on the front side of the reflective diffraction grating plate provided with silver halide emulsion;
VII. developing the exposed reflective diffraction grating plate, by a wet chemical process;
VIII. treating the chemically processed reflective diffraction grating plate with 1% of Potassium Iodide solution for 10minutes such as to provide a print-out free reflective diffraction grating plate; and
IX. drying the treated reflective diffraction grating plate at an ambient temperature.
Herein it is noted that the silver halide hologram emulsion is provided with a substantially high resolution of 20000 lines/mm and the grain size of 4nm, being for recording the sharp reticle image on the transmission reticle hologram plate and recording the interference of beam on one side of reflective diffraction grating plate.
It is also noted, that the said reticle mask is composed of chrome plate with substantially high density OD 5 and provided with the lines maintained at the micron level accuracy. The said transmission reticle object beam passing through the reticle mask records sharp and clear reticle image on the transmission reticle hologram plate.
It is further noted herein, that the said laser light beam at 650nm wavelength from the said laser diode incidents on front side of the reflective diffraction grating plate. The incident laser light beam is further collimated and diffracted at 560 angular deviations towards the transmission reticle hologram plate by the means of reflective diffraction grating plate, for the purpose of reconstructing, or illuminating the recorded reticle image therein.
The focal length of the said reflective diffraction grating plate is 50mm, and the laser diode is disposed exactly at the focal point of the diffraction grating plate.
Herein it is noted that the said silver halide emulsion shrinks or swells due to external temperature variation, thereby causing the reticle hologram image recorded thereon to shift, if different wavelength of laser beam is used for recording and reconstruction, so as to avoid the reticle hologram image shift, the laser beam with the wavelength of 650nm is used for recording both the holographic optical elements, and the same laser beam with the wavelength of 650nm is used in the apparatus to reconstruct the reticle hologram image.
It is further noted herein that the transmission reticle hologram plate has a dual property, such as transparent view finder window for viewing the target and superimposed the holographic reticle image in the view finder window for the purpose of aiming the target. The said transmission reticle hologram plate are configured with a protecting glass for having high visible transmission of about 95%, wherein the said protecting glass are made up of anti-reflective coating, wherein the said protecting glass wavelength is about 300nm to 700 nm. Further the diffraction efficiency of transmission reticle hologram plate is about 1% to 5% and the diffraction efficiency of holographic reflection grating is atleast 60%.
BRIEF DESCRIPTION OF DRAWINGS:
For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which:
Figure 100 illustrates isometric view of holographic weapon sight apparatus.
Figure 200 illustrates the reticle hologram image
Figure 300 illustrates the inside view of the holographic weapon sight apparatus
Figure 400 illustrates the schematic representation, showing the steps for recording the of transmission reticle hologram plate.
Figure 500 illustrates the schematic representation showing the steps for recording of reflective diffraction grating plate.
DETAILED DESCRIPTION OF THE INVENTION WITH RESPECT TO DRAWING:
For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the examples, sometimes referred to as embodiments, illustrated and/or described herein. Those are mere examples. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Such alterations and further modifications in the described process, systems or devices, any further applications of the principles of the invention as described herein, are contemplated as would normally occur to one skilled in the art to which the invention relates, now and /or in the future in light of this document.
In the disclosure herein, consideration or use of a particular element number in a given FIGURE or corresponding descriptive material can encompass the same, an equivalent, or an analogous element number identified in another FIGURE or descriptive material corresponding thereto Referring now to the drawings,
Figure (100), illustrates isometric view of holographic weapon sight apparatus, comprising of a laser diode (110), laser beam emitting at 650 nm wavelength (115) from the laser diode, reconstruction- collimated beam diffracted at 560 angular deviation (120), reflective diffraction grating plate (125), transmission reticle hologram plate (130), transparent view finder window (135), a mechanical holder (140), adjustable screws to move in the x axis and y axis (145), a tooth wheeler (150), reticle hologram image (155)
Figure (200), illustrates the reticle hologram image, wherein showing the substantially bigger outer circle (210), four quadrant tick (220), centre dot (230)
Figure (300), illustrates the inside view working principle of the holographic weapon sight apparatus, wherein comprises of laser diode (110), laser beam emitting at 650 nm wavelength (115) from the laser diode, reconstruction- collimated beam diffracted at 560 angular deviation (120), reflective diffraction grating plate (125), transmission reticle hologram plate (130), reticle hologram image
Figure (400), illustrates the schematic representation showing the steps for recording the of transmission reticle hologram plate, wherein comprises of transmission reticle hologram plate (130), laser beam with the wavelength of 650nm (410), beam splitter (415), transmission reticle object beam (420), transmission reticle reference beam (425), a first mirror (430), a second mirror (435), a first spatial filter (440), a second spatial filter (445), a reticle mask (450), an imaging lens (455).
Figure (500), illustrates the schematic representation showing the steps for recording of reflective diffraction grating plate, wherein comprises of laser beam with the wavelength of 650nm (410), a beam splitter (510), a diffraction grating object beam (515), a diffraction grating reference beam (520), a first mirror (525), a second mirror (530), a first spatial filter (535), a second spatial filter (540), front side of the reflective diffraction grating plate coated with silver halide (545), opposite side of the reflective diffraction grating plate devoid of silver halide coat (550), collimated diffraction grating object beam to the non-silver halide coated side of reflective diffraction grating plate (555), reflected diffraction grating reference beam to incident on the front side of reflective diffraction grating plate (560).
Some embodiments of this invention, illustrating all its features, will now be discussed in detail. The words "comprising," "having," "containing," and "including," and other forms thereof, are intended to be equivalent in meaning and be open ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items.
It must also be noted that as used herein and in the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Although any systems and methods similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present invention, the preferred, systems and methods are now described.
Some embodiments may be described using the expression “one embodiment” or “an embodiment” along with their derivatives. These terms mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment.
The present invention is described in detail below with reference to several embodiments and some examples. These illustrations and discussions are for the purpose of demonstration only. For the one with art and skill as well as expertise it will be apparent that these examples can be modified within the scope and spirit of this invention and also set forth in claims.
An apparatus disclosed in the present invention relates to simple and compact holographic weapon sight for accurate aiming and firing of the target, capable of being used for close combat and long range firing. The alternative application of the holographic weapon sight includes, but not limited to telescopes, mono or binoculars, camera, any aiming devices or any combination thereof.
In a preferred embodiment, holographic weapon sight comprises a laser diode (115) and holographic optical elements disposed at an appropriate placement for the purpose of reconstructing the hologram reticle image in the path of the view finder of the viewing window (135) and a collimated laser beam to illuminate it.
An advantage to holographic weapon sight is that they eliminate the parallax problem of some optical collimator based sights (such as the red dot sight) where the spherical mirror used induces spherical aberration that can cause the reticle to skew off the sight's optical axis.
It is further noted that the reticle image pattern of preferred embodiment includes a substantially large outer circle with four quadrant ticks, and a centre dot, wherein the centre dot having the values of 1MOA/2 MOA for precise long range aiming about 300 meters and the said outer circle having a value of 65 MOA for short distance aiming purpose, thereby increasing the field of view and supporting the two eye open aiming.
As an alternative embodiment, any possible pattern of holographic reticle image shall be used either for a specific application mentioned in preferred embodiment, or to the any possible applications aforementioned.
It is also noted herein, the term holographic optical element is a general or a common representations for the optical elements used in this present invention. Further, the aforementioned holographic optical elements include the reflective diffraction grating plate (125) and a transmission reticle hologram plate.
In the preferred embodiment, the laser diode (110) is the source for emitting laser beam at the specific wavelength of 650 nm with maximum power of 5mW and it is being connected to 3V power supply. Further, the laser intensity and on/off operations are controlled by the controller unit. The laser diode (110) in the holographic weapon sight is disposed perpendicularly to the front side of the reflective diffraction grating plate.
As an alternative embodiment, the laser beam of wavelength 635nm, or, 645nm or 649nm, or any possible wavelength shall be used, whereby altering and providing the appropriate optical elements with respective substrates and coating material thereon.
In a preferred embodiment of the present invention, reflective diffraction grating plate (125) is being disposed in the path of the laser beam from the laser diode (110), by means of adjusting mechanism to diffract and direct the laser beam, whereby converting the inline diverging laser beam from laser diode (110) into collimated laser beam with off axis 56° (120) output in the reflected direction. The transmission reticle hologram plate is disposed in the path parallel to the laser beam diffracted at an angular deviation of 560 (120) from the reflective diffraction grating plate.
Herein, it is noted that the transmission reticle hologram plate provides at least two functions, wherein the prime function is to reconstruct the parallax free holographic reticle image; another function is a transparent view finder window (135) for the purpose of viewing the target. Further the holographic reticle image aids in precise aiming of the target.
The mechanical holder (140) is provided in the present invention to support the reflective diffraction grating plate (125) by means of adjusting mechanism with at least two adjustable screws (145) to move reflective diffraction grating plate (125) in the x axis and y axis direction, so as to shift the laser beam in desired direction, thereby controlling the reticle image position for the purpose of zeroing.
The term zeroing, herein is defined as a process to adjust a sight of the user so the projectile of the bullet or shell may be placed at a predictable position within the sight picture. The principle, herein is to shift the line of aim so it intersects the parabolic projectile trajectory at a designated point, known as a zero, so the gun will repeatably hit where it aims at the distance of that zero.
Another attachment, a tooth wheeler (150), aids in supporting the laser diode (110) by means of slidable adjusting mechanism to move the laser diode (110) forward and backward on the same plane. For the experimental purpose the said tooth wheeler (150) shall move 2mm in forward direction and 2mm in backward direction, in total moving 4mm on the same plane. The adjustment of the tooth wheeler (150) allows the user to shift the laser diode (110) to set the laser diode (110) at the exact focal point of the reflective diffraction grating plate (125) for the purpose of correcting the parallax error. It is noted herein, that the mentioned reflective diffraction grating plate (125) being a type of optical element is provided with the focal length of 50mm in the preferred embodiment.
In a preferred embodiment, transmission reticle hologram plate (130) and reflective diffraction grating plate (125) is placed to parallel to each other inside the apparatus. Further, the collimated laser beam (120) is being directed to fall on the emulsion side of transmission reticle hologram (130), so that the reticle holographic image (155) of circle with four quadrant ticks and centre dot can be seen through the transmission reticle hologram plate (130) without parallax error. This reticle holographic image (155) is overlapped with the target for accurate firing.
In a preferred embodiment, the laser diode (110) with same wavelength 650nm (115) is used for recording and reconstruction of transmission reticle hologram image (155), so as to avoid image shift caused by using different wavelengths.
In a preferred embodiment, the reconstruction beam is collimated and diffracted the beam at 56° (120) in the same direction, so as the direct the beam to fall in silver halide emulsion side of transmission reticle hologram plate (130).
In a preferred embodiment, the said holographic elements are being protected by means of protecting glass wherein having a visible transmission of at least 95%., wherein further the mentioned protecting glass is composed of anti-reflective coating and permits only the wavelength in the range about 300nm and 700 nm.
In the present invention the holographic optical elements such as are specifically transmission reticle hologram plate (130) and reflective diffraction grating plate (125) are designed as per the apparatus requirements and method of fabrication of the same is disclosed herein.
In the preferred embodiment, the holographic optical elements; such as reflective diffraction grating plate (125), and transmission reticle hologram plate (130) are fabricated independently and these fabricated holographic optical elements are utilized in the apparatus – holographic weapon sight. Herein the recording of reticle image on the transmission reticle hologram plate (130) and recording of the grating pattern in the reflective diffraction grating plate (125) is termed as fabrication. Wherein further, similar laser of beam of wavelength of 650 nm (410) is used for fabrication of aforementioned holographic optical elements.
In reference to Figure 400, the present invention teaches the steps for recording the reticle hologram image in the transmission reticle hologram plate.
The laser emitting wavelength of 650nm (410) is split into two beams by means of a variable density beam splitter (BS) (415) also referred as Beam splitter. Herein, one beam is transmitted to the first mirror (M1) (430), wherein the laser beam is reflected towards transmission reticle hologram plate (130). Herein the beam from the first mirror (430) termed as transmission reticle object beam (420). Herein the transmission reticle object beam passes through the following elements such as first spatial filter SP1 (440), wherein the beam is expanded spatially and cleaned. Following the first spatial filter (440), the laser beam penetrates through the reticle mask (450) and imaging lens L1 (455).
It is also noted herein, that another beam termed as transmission reticle reference beam (425) from beam splitter (415) is redirected to the second mirror M2 (435) through second spatial filter (SP2) (445). Furthermore the transmission reticle reference beam (425) is reflected at the desired angle (56°) by second mirror M2 (435) towards the transmission reticle hologram plate (130), wherein the transmission reticle reference beam (425) is cleaned and expanded by SP2 (445) and collimated by lens (not shown in figure).
An electronic shutter means is used to control the exposure time of the laser beams on the transmission reticle hologram plate (130) that is composed of a light sensitive silver halide coating. Herein the laser beam includes the transmission reticle object beam (420) and reference beam (425). Further, the calculated exposure time and laser power is useful for the laser exposure on the silver halide holographic emulsion such as to record the transmission reticle hologram image (155) on the transmission reticle hologram plate (130).
After laser exposure, the silver halide coated glass plate is undergone for wet chemical process. Herein the chemical process as similar to the photographic development process, then chemically treated silver halide coated transmission reticle hologram plate (130) is dried at ambient temperature.
In the preferred embodiment, another holographic optical lens that is reflective diffraction grating plate (125) is independently prepared similar to transmission reticle hologram plate.
In reference to Figure 500, the present invention discloses the method of recording the reflective diffraction grating plate (125).
The laser emitting wavelength of 650nm (505) is split into two laser beams by means of a variable density beam splitter (BS) (510) and one of the laser beams is transmitted to a first mirror M1 (525). Herein, it is termed as diffraction grating object beam (515).
The diffraction grating object beam (515) is reflected by means of first mirror (525) at an angle 56 degree, towards the reflective diffraction grating plate (125), whereby passing through a first spatial filter (SP1) (535), wherein the said diffraction grating object beam (515) is spatially cleaned, expanded. Further the spatially cleaned diffraction grating object beam (515) is collimated and diffracted by collimator (not shown in the figure), wherein the diffraction grating objects beam (515) is incident on the opposite side of the reflective diffraction grating plate (550).
Another beam, termed as diffraction grating reference beam (520) from the beam splitter (510) is redirected by second mirror (M2) (530) and passed through the second spatial filter (SP2) (540). The diverging laser beam more specifically diffraction grating reference (520) beam from SP2 (540) incidents to the front side of the silver halide coated reflective diffraction grating plate (545).
Electronic shutter is used to control and calculate the exposure time on the silver halide holographic emulsion in order to fabricate reflective diffraction grating plate. An electronic shutter means is used to control the exposure time of the laser beams on the coated reflective diffraction grating plate (545) that is again composed of a light sensitive silver halide coating on the front side and devoid of silver halide emulsion coating on the other side (550) of the coated reflective diffraction grating plate. Herein the laser beam includes the diffraction grating object beam and reference beam. Further, the calculated exposure time and laser power is useful for the laser exposure on the front side provided with silver halide holographic emulsion such as to record the laser interference on the reflective diffraction grating plate.
After laser exposure, the silver halide coated glass plate is undergone for wet chemical process. Herein the chemical process is as similar to the photographic development process, then chemically treated silver halide coated reflective diffraction grating plate is dried at ambient temperature.
Herein it is noted that in a preferred embodiment, both the transmission reticle hologram plate and reflective diffraction grating plate are fabricated with the common materials such as silver halide emulsion coated on the transparent substrate. It is further noted that the mentioned silver halide emulsion is specifically prepared for recording the laser beam of wavelength 650nm (410) & (505). The silver halide emulsion material is composed of substantially high resolution (20000 lines/mm) and the grain size of 4nm.