Field of Invention
The present invention relates to an optical device for measuring angular
deviations/dispositions of an object such as a platform and the like. The angle of
inclination measured is the slope or gradient when the reference plane is the horizontal
plane. It is the tilt when the reference plane is the vertical plane. It is the relative slope
between two planes when the reference plane chosen is another arbitrary plane.
The description of the known art
It is presently known to use various gadgets/systems means for measuring of such angle
of inclination. Such gadgets/systems in use includes the following :
(A) Indirect qualitative methods :
(i) Using the principle of gravity where a water bubble is adapted to coincide
with middle point inside a tube when the surface is perfectly horizontal. Spirit
Level is used for leveling the platform base.
(ii) Optical methods including the principle that ray of light, which is reflected
back from the mirror along path of incidence must be horizontal.
(B) Direct methods : These are devices/gadgets used for direct measurement of
inclination which include :
(i) Clinometers:
A clinometer is light and compact hand instrument for measuring vertical angles, finding
out the slope of the ground and locating contours. These are used only in
rough survey where quick completion of the work is the deciding factor not the
accuracy.
(ii) Gyroscope:
These are commonly used in inertial navigation systems (aerospace and aircraft
vehicles) for sensing the absolute angular motion of the vehicle. There are tow types
of gyroscopic devices:
1. Free gyros, and
2. Restrained gyros.
Draw backs of the known art
However, although such varied devices/gadgets are known for use in measurement of angle of
inclination and the like such known/existing devices suffer from some inherent disadvantages
or drawbacks as discussed hereunder :
(a) Clinometers are used only on rough survey, as it is not accurate. Moreover, dynamic
measurement is not possible with these instruments. Since it is manually operated,
serious error can appear. It is a delicate instrument, proper handling is required i.e.
in lifting the instrument from the box there is a possibility of strain. If the locking
nut of the head is fixed too tightly, then certain forms are easily jammed. Little oil
need to be applied on leveling and tangential screws, when this part is exposed
collects dust over it. There is also a possibility of overturning by wind.
(b) Gyroscope suffers from various complications/problems which include apparent
drift, real drift, transport wander, gimbal lock, gimbal error and error due to
acceleration and turning.
Object of the invention
It is thus the basic object of the present invention to provide a simple and cost effective
optical device for measurement of angle of deviation or slope of a platform under static
or dynamic conditions.
Another object is directed to provide an optical de\ ice for measurement of angle of
inclination adapted to generate direct digital output that can be made compatible v\ith
microprocessor/other digital devices or display system.
Yet another object is to provide an optical device for measurement of angle of inclination
which would be accurate and of impro\ed resolution.
Yet further object is direct to provide an optical de\ ice for measurement at angle of
inclination which would be simple to obtain and can be miniaturized and thus portable
and easy to handle.
Yet further object is directed to provide optical device adapted to automatically measure
the angle of inclination under static or dynamic (from a moving platform) conditions
including measuring angle between any two planes.
Summary of the invention
Thus according to the present invention there is provided an optical device for measuring
angular deviations/dispositions of a subject such as a platform and the like comprising :
at least one light source and at least one corresponding light detection means ;
said light source and light detection means spaced and maintained in alignment
with one another such that light emitting from said source in the absence of any
obstacle in between is detected by said light detector:
an encoder means disposed there between said light source and the light detector having
perforation/slots therein such that on a plane surface the light from said light source
passes through said perforation/slots and received by said light detector while on an
inclined/sloped surface due to relative angular shift of the said light source and detector
with respect to said encoder the light path there between the said light source and the
detector is obstructed indicative of an inclined/sloped disposition.
According to one aspect the optical device of the invention comprises
a base member comprising a container having a base and peripheral side walls, said
light source and said light detector means rigidly fixed with respect to said base and/or
side walls of said container such that the light source and the corresponding detector are
spaced and face one another and are mutually aligned with respect to one another ;
said container containing fluid with said encoder means freely disposed therebetween
the light source and the detector means and adapted to float such that it always assumes
a vertical disposition irrespective of whether the container is placed on a plane or
inclined surface;
said encoder having selectively formed perforations/slots such that when said container
is on a plane surface, the encoder perforations/slots allow passage of the light from said
light source there through and are received by the detector means and when said
container is disposed on an inclined surface, due to the relative shift of the position of
the light source and said detector rigidly secured to said container with respect to the
freely vertically disposed encoder, light from said light source get obstructed by the
opaque portion of the encoder indicating a sloped/angular disposition of said container.
According to another aspect the optical device of the invention comprises
said encoder having selectively formed perforations/slots such that when said container
is on a plane surface, the encoder perforations/slots allow passage of the light from said
light source there through and arc received by the detector means and when said
container is disposed on an inclined surface, due to the relative shift of the position of
the light source and said detector rigidly secured to said container with respect to the
freely vertically disposed encoder, light from said light source get obstructed by the
opaque portion of the encoder indicating a sloped/angular disposition of said container.
According to another aspect the optical device of the present invention comprises
a base member having a substantially centrally positioned cut-out portion, said light
source having plurality of light sources and said light detector having plurality of
detector corresponding to the number of said light sources spaced and rigidly secured to
said base member, a vertically disposed rod passing there through said cut-out portions
of the base member supporting said encoder at the top and a bob/mass at its lower end
freely suspended with respect to said base platform.
According to another aspect the optical device of the present invention comprises
said base member having rigidly secured thereto said light source and said light
detector, said base member with said light source and light detector adapted to freely
swing and maintain constant vertical position of said light source and light detector;
said encoder supported by a rod with respect to a base which is adapted to be
placed/secured on the inclined surface whose inclination is to be detected, said encoder
positioned there between said light source and said light detector and held freely with
respect to said base member to assume corresponding inclined disposition based on the
angle of inclination of the surface to be detected with respect to the said vertically
disposed light source and light detector.
Thus the above-disclosed device of the invention advantageously utilizes the relative
displacement between the encoder plane and the axial plane of the source-detector assembly-
such that the displacement corresponds to the angle of inclination of the measuring plane with
respect to a reference plane.
The device basically involves the use of encoder, light sources (single source, multiple sources
or single source with segmented slot in front) and detectors (with or without lenses or slots in
front) wherein the light source and the light detector are placed on a base member selected from
container, base plate, rod, strip and the like.
Preferably, the device for measuring inclination of the invention involves arrangement for
creation of relative displacement between encoder plane and the axial plane of the source-
detector assembly comprising a float and fluid, a suspension system (with or without bearing,
pivot, slot), or the encoder along with the bob (mass) attached to the rod fitted to the encoder,
the suspension system such that the encoder system swings in air or in a fluid, free to swing or
fixed with a damper or a restraining string or source detector assembly with suspension system
held in position with bob attached to the base member /or means to float such that the source
detector system swings freely in air or in a fluid by means of the suspension system.
The details of the invention its objects and advantages are explained hereunder in greater detail
in relation to non-limiting exemplary illustrations as per the accompanying figures wherein :
Fig. 1 is a schematic illustration of an embodiment of the optical device of the invention ;
Fig. 2 is an illustration of the encoded disk (encoder) used in the device of the invention ;
Fig. 3 schematically illustrations of the disposition of the device of Fig. 1 when placed on an
inclined plane;
Fig. 4 is an illustration of another embodiment of the optical device in accordance with the
present invention.
Fig. 5 is an illustration of another embodiment of the optical device in accordance with the
present invention.
Reference is first invited to Fig. 1 which shows the device comprising a base member (BP) in
the form of a container having a base and peripheral walls (PW) containing a fluid (FD). An
encoder (KN) placed in between two strips (ST) holding respectively the light source (LS)
comprising an array of light sources and the detector means (DM) comprising array of equal
number of light detectors. Each light source is aligned with a light detector. In this embodiment
the encoder (1:.N) is kept vertically disposed by supporting the same with respect to a rod (RD)
the lower end of which is provided with a iloat (FT). The two strips are rigidly fixed with
respect to the base member (BP) such that in the absence of the encoder the light sources and
the detectors are just opposite to each other. The light sources can be fitted with lenses and/or a
slit such that the light emitted from each source is considered to be parallel and non-divergent.
Same arrangement can be made in front of the detector strip. The slit may be a long one or
vertically segmented so that light from one detector can be incident only on the light detector,
which is aligned with it. The minimum gap between the two strips (source and detector) should
be such that the encoder can swing through the gap without touching any of the strips.
Reference is now invited to accompanying Fig. 2 which illustrates the encoder means used in
the device of the invention. As illustrated in the said figure, the encoder is basically a
perforated sheet of metal or plastic or paper or any other hard material with perforations or
holes (PR) on it defining opening for transmitting (TR) light through and opaque regions (OR)
blocking such light. The encoder is preferably developed based, in accordance with a specific
binary code like BCD (Binary to Decimal), GRAY, Pseudo-Random, or other codes. It can be
in the form of a sector or circular or any other geometric pattern-shaped. The dimensions of the
light sources and the range of measurement are based on the dimensions of the encoder. The
number of tracks (TKS) on it also depend on number of bits used in the encoding, the range of
measurement and the resolution of the measurement. Additional tracks can be provided on the
encoder with respect to the plane passing through the axes of the two strips and to provide
parity check or other flexibility in measurement. The number of light sources and the light
detectors fitted on the strips depend on the number of tracks on the encoder.
Reference is now invited to accompanying Fig. 3 which illustrates the disposition of the device
on an inclined/sloped surface.
The crux of the measurement using the device lies in generation of a relative movement
between the two strips (housing light sources and detectors, which are fixed in position with
respect to each other) and the encoder. The relative displacement is equal to the angle of
inclination between the two planes (measuring and reference), the encoder is fitted in such a
way that its axis always remains vertical. For this a rod is attached to the encoder disc. Other
side of the rod is attached to a float placed in a liquid in a container of the measuring device
unit, which also serves as the base for fixation of the source and detector strips.
Reference is now invited to accompanying fig. 4 which shows another embodiment of the
optical device in accordance with the invention. In the embodiment the device comprises of a
base plate (BP) having a cutout (CO). The light source (LS) having the array of the light
sources and the light detector (DM) having corresponding numbers of light detectors are rigidly
fixed to the base plate (BP) on opposite sides thereof. The encoder means (EN) is supported on
a vertically disposed rod (RD) with the other end of the rod fixed with a bob (mass) (MA) and
the assembly suspended vertically by using a pin or spindle (PN) with or without a bearing
fixed to the base plate (which also holds the source and detector strips). As the base plate or the
container top surface is tilted in accordance with the measuring plane, the encoder adapts to
remain vertical and a relative displacement equal to the angle of tilt between the encoder and
the base plane takes place. This changes the positions of the perforation or holes on the encoder
and light from certain sources fall on their corresponding detectors provided the encoder holes
appear in the path of the rays. If instead of holes the opaque segment of the encoder blocks the
path, the corresponding detectors remain dark. Thus corresponding to each relative position of
the encoder and the source and detector strips there will be a definite number of detectors,
which accordingly turn on, or off. The pattern usually depends on the binary code adopted. For
better performance in dynamic measurement of angle of inclination, the encoder system can be
provided with a damper or restraining spring attached to the rod. One method of damping can
be providing a heavy viscosity fluid in which the float or the bob is immersed.
Reference is now invited to accompanying fig. 5 which shows another embodiment of the
optical device in accordance with the invention. In this embodiment the device comprises of a
base plate (BP) as a base member supporting two planes (ST) namely source plane with light
source (LS) and detector plane with light detector (DM). The light source (LS) having the array
of the light sources and the light detector (DM) having corresponding numbers of light
detectors are rigidly fixed to the base plate (BP) on opposite sides thereof and are vertical to it.
The encoder means (EN) is supported on a vertically disposed rod (RD) with the other end of
the rod secured on the encoder base (EB). The said base plate is fixed with a bob (mass) (MA)
and the assembly is suspended by means of pivot (PV), with respect to the encoder. When the
encoder base is placed on the inclined surface the encoder assumes the angle of inclination of
the surface while the source-detector assembly swings freely to always maintain a vertical
disposition. As a result a relative displacement equal to the angle of tilt occurs between the
encoder and the plane of source and detector. This changes the position of the perforation or
holes on the encoder and light from certain sources fall on their corresponding detectors
provided the encoder holes appear in the path of the rays. If instead of holes the opaque
segment of the encoder blocks the path, the corresponding detectors remain dark. Thus
corresponding to each relative position of the encoder and the source and detector strips there
will be a definite number of detectors, which accordingly turn on, or off. The pattern usually
depends on the binary code adopted.
The output of the device is electrical signal in binary code form (direct digital form). It is fed to
a display unit or an electronic processing unit for further use.
The device is best used under conditions of static measurements. For dynamic measurement the
damper is provided or the averaging of the readings for a fixed period can be done to get the
mean, as the unit is likely to be affected by vibration of the moving platform.
In case of measurement of inclination between two arbitrary planes, two measurements are
taken i.e. measurement of inclination of each plane with respect to the horizontal plane and
then taking the difference of the two readings.
For measurement of angle of tilt of a plane with respect to the vertical axis care has to be taken
that fluid, if used, should not ooze out of the container. The encoder system with the bob
moving in air is recommended. To get a direct reading of the angle of tilt with respect to the
vertical plane, a shift of 90° in the coding pattern or a bias to the output processing will suffice.
The device of the invention can alternatively have the base plate with fixed source and detector
strips adapted to swing and maintain a constant position in the vertical direction with the help
of a bob or a float in a fluid, while the encoder is kept fixed with the frame. In this case the
encoder along with the device frame assumes the inclination of the measuring plane and
detector strip assemblies maintain the vertical position.
Thus, the above-disclosed device of the invention provides a simple, cost-effective and accurate
measurement of angle of inclination. The device can be adapted for various uses of
measurement of inclination/slopes including areas such as in aeronautic field where the flight
pitch angle and roll angle has to be monitored continuously, for surveying and leveling, in
industry for fitting of machine tools requiring perfect horizontal base, geological applications
for measurement of slope or tilt of rocky plane is a major concern, in civil construction,
roadways and earth sciences inclination measurement is also required, in automobile industry
the performance of a car on inclined roads is tested, even for mounting of solar collectors the
performance of which depend on the mounting angle and also in railways where desired
gradient of the rail track is required to be maintained.
WE CLAIM :
1. An optical device for measuring angular deviations dispositions of a subject such as a
platlorm and the like comprising :
at least one light source and at least one corresponding light detection means :
said liuht source and light detection means spaced and maintained in alignment
with one another so that light emitting from said source in the absence ol any
obstacle in between is detected bv said light detector;
an encoder means disposed there between said liuht source and the light detector f
having selectively made perforation, slots therein such thahon a plane surface the
light from said light source passes through said perforation slots and received by
> said light detector.while on an inclined/sloped surface due to relative angular shift
of the said light source and detector with respect to said encoder the light path
there between the said light source and the detector is obstructed indicative of an
inclined/sloped disposition.
, An optical device as claimed in claim 1 comprising
S a container having a base plate and peripheral side walls, said light source and
said light detector means riuidlv fixed with respect to said base plate and/or side
. [ walls ol said container stteh- that the light source and the corresponding detector
are spaced and face one another and are mutually aligned with respect to one
another;
said container containing lluid with said encoder means freely disposed there
between the light source and the detector means and adapted to float so it
always assumes a vertical disposition irrespective of whether the container is
placed on a plane or inclined surface :

said encoder having selectively formed perforations/slots that when said
container is on a plane surface, the encoder perforations/slots allow passage of the
light from said light source there through and are received b\ the detector means
and when said
container is disposed on an inclined surface, due to the relative shift of the position of
the light source and said detector rigidly secured to said container with respect to the
freely and vertically disposed encoder, light from said light source get obstructed by the
opaque portion of the encoder indicating a sloped/angular disposition of said container.
3. An optical device'as claimed in claim 2, wherein the space therebetween said light source
$pJ and the light detector is-sach-thatjthe encoder is allowed to freely swing therebetween the
said source and the detector.
4. An optical device as claimed in claim 1 comprising
a base member having rigidly fixed thereto said light source and said light detector, said
base plate with said light source and light detector adapted to freely swing and maintain
constant vertical position of said light source and light detector,
a frame member having fixed thereto an encoder disposed there between and said light

source and the light detector means so that when placed on an inclined/slope surface,
the encoder fixed to the frame adapted to assume corresponding inclined disposition
with respect to the constant vertical disposition of the light source and the detector
means.
5. An optical device as claimed in anyone of claims 1 to 4 wherein said light source comprises
plurality of light sources as an array of light and said detector means comprising plurality of
detectors as an array of detectors, each said light source having a corresponding detector.
6. An optical devide as claimed in anyone of claims 1 to 5, wherein said light source is fitted
with lenses and/or slot so that the light emitted from each source is parallel and non-
divergent.
7. An optical device as claimed in anyone of claims 1 to 6, wherein said detector means is
fitted with lenses and/or slot so that the light is received parallel and non-divergent.
8. An optica] device as claimed in anyone of claims 1 to 7, wherein said perforations/slots are
selected to be long and/or vertically segmented adapted such that light from one source is
incident only on one light detector.
9. An optical deVice as claimed in anyone of claims 1 to 8, wherein said encoder comprises a
perforated slot.
10. An optical device as claimed in claim 9, wherein said perforated slot is obtained of metal,
plastics, paper or any other suitable hard material.
11. An optical devifce as claimed in anyone of claims 1 to 10, wherein said perforations/slots
are provided in said encoder in accordance with specific binary code preferably BCD
(Binary to Decimal), GRAY, Pseudo-Random or other codes.
12. An optical device as claimed in anyone of claims 1 to 11, wherein the dimensions of the
light sources and the range of measurement are selected based on the dimensions of the
encoder.
n-r........
13. An optical devic£ as claimed in anyone of claims 1 to 12, wherein said encoder comprises
of tracks provided with said slots/perforations, the number of tracks being based on the
number of bits used in the encoding, the range of measurement and the resolution of the
measurement.
14. An optical dfevice as claimed in anyone of claims 1 to 13 comprising additional tracks on
said encoder with respect to the plane passing through the axes of the two strips and to
provide check on other flexibility measurement.
15. An optical device as claimed in anyone of claims 1 to 14, wherein the number of light
sources and the light detectors on the strips depend on the number of tracks on the encoder.
16. An optical device as claimed in anyone of claims 1 to 15, wherein the said light source
comprise a single source of light and said encoder comprises of a strip having plurality of
holes/ slits with or without lenses and said light detector comprises plurality of detector
means corresponding to the number of slits/ holes.
17. An optical device as claimed in anyone of claims 1 to 14, wherein the encoder axis is
always maintained vertical.
18. An optical device as claimed in claim 16, wherein the encoder is supported on a vertical rod
with the lower end of the rod attached to a float placed in a liquid in said container.
19. An optical device as claimed in anyone of claims 1 to 17, comprising
a base member having rigidly secured thereto and spaced apart said light source and said
light detectors;
said encoder supported by a vertically disposed rod suspended freely with respect to the
base plate.
20. An optical device as claimed in claim 18, wherein said encoder is suspended by a rod
means the lower end of which is provided with a bob /mass with said rod freely suspended
So «°£>-----
wtth respect to said base platform by means of a suspension means sueh-tfiat when said base
is placed on a flat platform, the encoder slot/perforations are in alignment with the light
source and the light detector and when the base is disposed on an inclined/sloped surface,
an angular disposition of said light source and detector fixed to the base member with
respect to the freely vertically disposed encoder take place whereby depending upon the
angular displacement, the light from the light source is obstructed by the opaque portion of
the encoder.
21. An optical device as claimed in anyone of claims 4 to 17. comprising
said base member having rigidly secured thereto said light source and said light detector,
said base member with said light source and light detector adapted to freely swing and
maintain constant vertical position of said light source and light detector;
said encoder supported by a rod with respect to a base which is adapted to be
placed/secured on the inclined surface whose inclination is to be detected, said encoder
positioned there between said light source and said light detector and held freely with
respect to said base member to assume corresponding inclined disposition based on the
angle of inclination of the surface to be detected with respect to the said vertically disposed
light source and light detector.
22. An optical device as claimed in claim 21 wherein the said base member with said light
source and light detector means is held in position by a means selected from bob /mass or
float in a fluid filled container.
23. An optical devicjd as claimed in claim 21 -22 wherein the said base member with said light
source and light detector means is adapted to freely swing by a means selected from pivot,
bearing and slot in order to maintain constant vertical position of said light source and light
detector.
24. An optical device as claimed in any one of claims 1-23, wherein the base member with said
light source and light detector is selected from container, base plate, strip and rod.
25. An optical device as claimed in anyone of claims 1 to 24, comprising damper/restraining
spring attached to said encoder means.
26. An optical device as claimed in claim 25, wherein said damper comprises heavy viscosity
fluid in which the float or the bob is immersed.
27. An optical device as claimed in anyone of claims 1 to 26. comprising an output means
indicative of the angle of inclination as an electrical signal.
v\ 28.i