DESC:4. DESCRIPTION
Technical Field of the Invention

The present invention pertains to the field of optical system to miniaturized telescope-based imaging systems for satellites, drones or any aerial platform. More specifically, it focuses on improving image quality while making the system compact, lightweight, and efficient for use in aerospace and satellite imaging applications.

Background of the Invention

In recent years, miniaturized satellite platforms, particularly CubeSats, have revolutionized the field of space technology and Earth observation. CubeSats are standardized nanosatellites typically built in multiples of 10×10×10 cm units (1U), offering a cost-effective, compact, and highly modular alternative to traditional large-scale satellites. Their small size, reduced launch costs, and rapid development cycles make them ideal for applications in low Earth orbit (LEO), such as environmental monitoring, disaster response, and scientific research.

Despite their compactness, CubeSats are increasingly expected to perform complex tasks, including high-resolution imaging and remote sensing. This creates a significant demand for miniaturized, lightweight optical systems that can deliver performance comparable to larger satellite payloads. However, integrating high-precision optical components within the limited volume and power budget of CubeSats remains an engineering challenge. Their small form factor restricts the use of large aperture telescopes and requires innovative solutions for thermal stability, stray light management, and sensor integration.

To address these constraints, researchers have explored various compact optical payloads, including foldable telescopes, off-axis mirrors, and deployable lens assemblies. Although these developments have demonstrated the feasibility of advanced optics on CubeSats, they often come with trade-offs in complexity, alignment sensitivity, structural robustness, and imaging quality. As CubeSat missions move toward more demanding operational goals, there is a growing need for optical systems that are not only miniaturized but also reliable, easy to assemble, and capable of multi-spectral high-resolution imaging.

Historically, traditional space telescope architectures rely on large, bulky systems with deployable or segmented mirrors to achieve sufficient focal length and aperture. These systems involve complex deployment mechanisms, high-tolerance alignment systems, and significant power and volume requirements, making them unsuitable for nanosatellite platforms. Moreover, off-axis telescope configurations often require intricate mirror arrangements and precise opto-mechanical tuning, which are vulnerable to misalignment under dynamic space conditions.

Other miniaturized designs have attempted to replicate traditional optics in smaller footprints, often at the cost of increased optical aberrations, poor stray light suppression, or limited spectral range. Systems using simple spherical lenses or mirrors suffer from chromatic and spherical aberrations, degrading image quality, especially over wide fields of view (FOV). Furthermore, conventional image sensors paired with low-grade optics struggle to deliver consistent performance in both day and night scenarios, reducing their effectiveness in continuous Earth monitoring missions.

The present invention overcomes these drawbacks by introducing a compact, integrated telescope-based imaging system tailored for CubeSat dimensions. It uses aspheric convex and concave reflective surfaces to significantly shorten the optical path while maintaining high resolution. Integrated stray light baffles, optimized correction lenses, and high-performance sensor arrays ensure diffraction-limited imaging across visible and infrared spectrums. The design eliminates the need for complex alignments and deployment mechanisms, offering a rugged, easy-to-manufacture optical system ideal for next-generation miniature satellite missions.

Brief Summary of the Invention

The following presents a simplified summary of the disclosure to provide a basic understanding to the reader. This summary is not an extensive overview of the disclosure, nor does it identify key or critical elements of the invention or delineate its scope. Its sole purpose is to present some concepts disclosed herein in a simplified form as a prelude to the more detailed description that follows.
A primary objective of the invention is to provide a compact and lightweight telescope-based imaging system suitable for integration into miniature satellites, such as CubeSats, without compromising optical performance.
Another objective of the invention is to incorporate aspheric convex and concave reflector surfaces within a monolithic optics piece to achieve a shortened and stable optical path, enhancing image quality and reducing system complexity.
Yet another objective of the invention is to enable multi-spectral imaging by integrating visible and infrared sensor arrays, including CMOS and InGaAs detectors, for high-resolution image capture across varying lighting conditions.
A further objective of the invention is to minimize stray light interference using a precision-engineered baffle system, improving image contrast and clarity, particularly in high-glare environments such as space.
According to an aspect of the present invention, a miniaturized telescope-based imaging system is disclosed. The system comprises a monolithic optics piece, an aspheric convex reflector on the first surface, a correction lens, a doublet field lens, a baffle, a primary aspheric convex mirror, a secondary aspheric concave mirror, and an image sensor system.
In accordance with this aspect, the miniaturized telescope-based imaging system is designed for use in compact satellite platforms, particularly CubeSats. The system achieves high-resolution imaging performance within a confined volume by utilizing a monolithic optics piece formed from materials such as BK7, fused silica, or infrared-transparent substrates like germanium or zinc selenide. This optics piece integrates a first aspheric convex reflector surface and a second aspheric concave reflector surface, which collaborate to fold the optical path and minimize the telescope’s physical length while maintaining optical stability.
In accordance with this aspect, the optical configuration ensures precise light collection and redirection. The convex reflector on the first surface receives incoming light across a wide field of view (FOV), while the concave reflector on the second surface redirects this light through a correction lens followed by a doublet field lens. The correction lens, made from N-BK7 or chalcogenide glass depending on the spectral application, corrects spherical and chromatic aberrations to within 0.2% distortion. The doublet field lens, an additional optical element, enhances field flattening and ensures uniform focus across the sensor plane, enabling diffraction-limited performance.
In accordance with this aspect, an image sensor system is positioned at the focal plane, comprising visible (CMOS) and infrared (InGaAs or microbolometer) detectors. These sensors are optimized for different spectral ranges, including visible (400–700 nm) and mid-wave infrared (MWIR, 3–5 µm). The system supports frame rates up to 60 fps for visible imaging and 30 fps for MWIR, with high dynamic ranges (>70 dB and >65 dB, respectively). Image clarity is further improved through on-chip correlated double sampling (CDS) and post-processing by a digital processing unit (DPU).
In accordance with this aspect, the optical system incorporates a baffle assembly integrated into a cylindrical groove near the concave reflector surface. Constructed from aerospace-grade aluminum with black anodized or IR-absorptive coatings, the baffle suppresses more than 95% of stray light from angles beyond ±15°, significantly improving contrast and reducing background noise. Precision-aligned ridges within the baffle further attenuate off-axis reflections, enhancing overall image fidelity.
In accordance with this aspect, the entire system is optimized for manufacturing and alignment using advanced techniques such as CNC grinding, diamond turning, and laser interferometry. The optical components are aligned within tight tolerances (±10 µm axial, <0.01° tilt) and bonded for structural rigidity using aerospace-grade adhesives. Coatings, such as broadband anti-reflective (AR) for visible optics and diamond-like carbon (DLC) or gold for MWIR elements, ensure reflectance below 1%. The result is a rugged, miniaturized optical system capable of delivering space-grade imaging performance without requiring deployable components or complex mechanical adjustments.
Further scope of applicability of the present invention will become apparent from the detailed description provided hereinafter. However, the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration along with the complete specification.

Brief Summary of the Drawings

The invention will be further understood from the following detailed description of a preferred embodiment taken in conjunction with an appended drawing, in which:

Fig. 1 illustrates the block diagram representing the component hierarchy of the miniaturized telescope-based imaging system (100), in accordance with the exemplary embodiment of the present invention.

Fig. 2 illustrates the internal ray propagation and stray light suppression mechanism within the optics piece (102) of the miniaturized telescope-based imaging system (100), in accordance with the exemplary embodiment of the present invention.

Fig. 3 illustrates the extended optical configuration of the miniaturized telescope-based imaging system (100) including external mirrors and sensor placement, in accordance with the exemplary embodiment of the present invention.

Fig. 4 illustrates example spectral configurations of the miniaturized telescope-based imaging system (100), in accordance with the exemplary embodiment of the present invention.

Fig. 5 illustrates the Modulation Transfer Function (MTF) curves, in accordance with the exemplary embodiment of the present invention.

Fig. 6a illustrates the field curvature characteristics of the miniaturized telescope-based imaging system (100) across tangential and sagittal planes, and Fig. 6b illustrates its distortion profile based on F-Tan(Theta) analysis, in accordance with the exemplary embodiment of the present invention.

Detailed Description of the Invention

The present disclosure emphasizes that its application is not limited to the specific details of construction and component arrangement as illustrated in the accompanying drawings. The invention is adaptable to various embodiments and implementations. The phraseology and terminology used herein are for descriptive purposes and should not be construed as limiting.
The terms "including," "comprising," or "having" and their variations are intended to encompass the listed items, their equivalents, and additional items. The terms "a" and "an" signify the presence of at least one of the referenced items without denoting quantity limitations. Terms such as "first," "second," and "third" are used to distinguish elements without implying order, quantity, or importance.
According to an exemplary embodiment of the present invention, the miniaturized telescope-based imaging system (100) comprises a monolithic optics piece (102), an aspheric convex reflector (104) on the first surface, a correction lens (106), a doublet field lens (116), a baffle (110), a primary aspheric convex mirror (112), a secondary aspheric concave mirror (114), and an image sensor system (108).
In accordance with the exemplary embodiment of the present invention, the miniaturized telescope-based imaging system (100) includes a monolithic optics piece (102) formed of a transparent optical material, such as BK7 or fused silica for visible light applications, or germanium (Ge) or zinc selenide (ZnSe) for mid-wave infrared (MWIR) applications, selected for their high optical clarity and spectral transmission properties.
In accordance with the exemplary embodiment of the present invention, the optics piece (102) incorporates two optically active surfaces. The first surface features an aspheric convex reflector surface (104) located within a central region, surrounded by a peripheral ring-shaped region. This convex reflector captures incoming light across a wide field of view (FOV) and directs it internally toward the second surface. The second surface of the optics piece includes an aspheric concave reflector surface formed around a central cylindrical groove, which redirects light toward the focal plane, creating a compact folded optical path approximately one-third the length of conventional telescope systems.
In accordance with the exemplary embodiment of the present invention, a correction lens (106) is positioned adjacent to the cylindrical groove of the second surface. This lens, which may be an aspheric single element or a cemented doublet made of N-BK7 for visible light or chalcogenide glass for MWIR applications, is precisely aligned to correct spherical and chromatic aberrations, ensuring image distortion remains below 0.2% across the full FOV. A doublet field lens (116), comprising two optical elements made of materials such as N-BK7 or chalcogenide glass, is placed downstream of the correction lens to enhance field flattening and ensure uniform focus across the sensor plane, enabling diffraction-limited performance.
In accordance with the exemplary embodiment of the present invention, an image sensor system (108) is fixed at the focal plane relative to the second surface of the optics piece. The sensor system includes a visible light CMOS sensor array with a resolution of 12 megapixels and a pixel size of 3.45 µm, and an MWIR detector, such as an InGaAs or microbolometer array, with a resolution of 640×512 pixels and a pixel size of 15 µm. These sensors are selected based on mission-specific spectral requirements and are capable of operating at frame rates up to 60 fps for visible light and 30 fps for MWIR.
In accordance with the exemplary embodiment of the present invention, a baffle (110) is integrated into the cylindrical groove to suppress stray light and background reflections.
In accordance with the exemplary embodiment of the present invention, the system further includes a primary aspheric convex mirror surface (112) with a hyperbolic surface profile, positioned to collect and converge incoming light. A secondary aspheric concave mirror surface (114), also with a hyperbolic surface profile, is placed downstream to reflect and relay the focused light toward the correction lens, doublet field lens, and ultimately to the image sensor system. These mirrors surface are fabricated using high-precision CNC grinding and diamond turning processes and are mounted on a lightweight structural frame made of composite materials to ensure minimal mass and high thermal stability.
In accordance with the exemplary embodiment of the present invention, the manufacturing and assembly process of the optical system prioritizes high precision and structural integrity. Optical surfaces are coated with broadband anti-reflective coatings (reflectance < 0.5% for visible light) or diamond-like carbon (DLC) or gold coatings for MWIR optics (reflectance < 1%). System alignment is achieved using laser interferometry and autocollimation techniques, with axial tolerances of ±10 µm and angular tilt tolerances of less than 0.01°, followed by bonding with aerospace-grade epoxy for ruggedization and thermal stability.
In accordance with the exemplary embodiment of the present invention, the complete imaging system (100) is designed for compatibility with compact satellite platforms, such as 1U or 3U CubeSats. For MWIR sensor configurations requiring cooling, optional thermoelectric coolers (TEC) or Stirling cycle coolers are employed to maintain sensor temperatures near 80 K. The system enables reliable, high-resolution, multi-spectral imaging from space without the need for deployable optics or external alignment, making it ideally suited for modern remote sensing and space-based Earth observation missions.
Now referring to the figures, Fig. 1 illustrates the component hierarchy of the miniaturized telescope-based imaging system (100) as disclosed in the present invention. The system comprises an integrated monolithic optics piece (102) with a first surface featuring an aspheric convex reflector (104) and a second surface incorporating a cylindrical groove with an aspheric concave reflector, supporting a correction lens (106), a doublet field lens (116), and a baffle (110) for optical alignment and stray light suppression. The system further includes a primary aspheric convex mirror (112) and a secondary aspheric concave mirror (114) that direct the focused light to the image sensor system (108). This arrangement enables compact, high-performance imaging suited for CubeSat platforms.
Fig. 2 illustrates the internal ray propagation and stray light suppression mechanism within the miniaturized telescope-based imaging system (100). The system includes an optics piece (102) featuring a convex aspheric reflector surface (104) that collects incident light and redirects it through the folded optical path. The concave reflector surface and cylindrical groove guide the rays toward the correction lens (106) and doublet field lens (116), which perform aberration correction and field flattening, respectively. A baffle (110) integrated near the groove effectively absorbs off-axis stray light, minimizing background noise and enhancing image contrast. The optical path is compact and optimized to maintain image fidelity across the field.
Fig. 3 illustrates the extended optical configuration of the miniaturized telescope-based imaging system (100), showcasing the role of external mirrors in enhancing focus and alignment. A primary aspheric convex mirror (112) collects and directs incoming light into the optics piece (102), where it is further refined by the internal optics and redirected toward the secondary aspheric concave mirror (114). The light then passes through the correction lens (106) and doublet field lens (116) and is captured by the image sensor system (108). This configuration improves image resolution and contrast while maintaining system compactness.
Fig. 4 illustrates example configurations of the telescope-based imaging system (100) optimized for both visible light and mid-wave infrared (MWIR) applications. The figure demonstrates how different material selections are made based on the spectral range required by the satellite’s mission. For visible light applications, optical materials transparent to visible wavelengths are used, while for MWIR applications, materials with suitable infrared transmission properties are selected. This configuration flexibility allows the system to be tailored to meet the specific needs of various imaging tasks, from high-resolution visible light photography to infrared sensing, supporting a wide range of satellite missions.
Fig. 5 illustrates the Modulation Transfer Function (MTF) performance of the miniaturized telescope-based imaging system (100), plotted as a function of spatial frequency in cycles per millimeter. The graph shows MTF curves for both tangential and sagittal orientations at field positions of 0.0°, 0.75°, and 1.5°. The MTF values demonstrate high image fidelity across a wide spatial frequency range, with minimal degradation at higher frequencies. The curves remain close to the diffraction limit, confirming the system’s ability to maintain high contrast and resolution across the entire field of view.
Fig. 6a presents field curvature and distortion analysis for the optical system. The left plot shows field curvature in millimeters along the +Y axis for various off-axis field points in both tangential and sagittal planes. The minimal deviation across the field confirms excellent image plane flatness. Fig. 6b displays F-Tan(Theta) distortion as a percentage, indicating low and nearly linear distortion characteristics across the field, with values remaining well below 2%, which is desirable for precision imaging and minimal geometric aberration.
,CLAIMS:5. CLAIMS
I/We Claim:
1. A miniaturized telescope-based imaging system (100) for miniature satellites, comprising:
a. an optics piece (102) formed of a transparent optical material selected from BK7, fused silica, germanium (Ge), or zinc selenide (ZnSe), the optics piece including:
i. a first surface having an aspheric convex reflector surface (104) within a central region and a peripheral ring-shaped region surrounding the central region for receiving input light over a wide field of view (FOV);
ii. a second surface including a cylindrical groove and an aspheric concave reflector surface surrounding the groove for directing the reflected light toward a focal plane;
b. a correction lens (106) located adjacent to the cylindrical groove of the second surface, configured as an aspheric single element or cemented doublet made of N-BK7 or chalcogenide glass for correcting spherical and chromatic aberrations to less than 0.2% distortion;
c. a baffle (110) positioned within the cylindrical groove, constructed of aerospace-grade aluminum (6061-T6), having a matte black anodized or IR-absorptive coating to reduce stray light by more than 95% for angles beyond ±15°, and including internal ridges for angular attenuation;
d. an image sensor system (108) fixed relative to the second surface at the focal plane of the optical system, the image sensor system including:
i. a CMOS sensor array for visible imaging;
ii. an InGaAs or microbolometer sensor array for SWIR and MWIR imaging;
e. a primary aspheric convex mirror (112) having a hyperbolic surface configured to collect and focus incoming light from the optics piece;
f. a secondary aspheric concave mirror (114) configured to reflect light from the primary mirror towards the image sensor and the secondary mirror being mounted in a lightweight structural frame;

2. The system (100) as claimed in claim 1, wherein the optics piece (102) has a diameter of approximately 70 mm and a thickness of 10 mm, with a central thickness tolerance of ±0.05 mm, and is optimized for visible (400–700 nm) or MWIR (3–5 µm) spectral ranges.

3. The system (100) as claimed in claim 1, wherein the correction lens (106) is an aspheric lens made of N-BK7 (visible variant) or chalcogenide glass (MWIR variant), having a refractive index of approximately 1.5168 at 587.6 nm or 2.4 at 4 µm respectively.

4. The system (100) as claimed in claim 1, wherein the baffle (110) is treated with black anodizing for visible applications and IR-absorptive coatings such as Acktar Metal Velvet for infrared applications, and includes internal ridges spaced to block light entering at critical angles.

5. The system (100) as claimed in claim 1, wherein the image sensor system (108) includes a 12 MP CMOS sensor with a pixel size of 3.45 µm for visible imaging, and a 640×512 InGaAs or microbolometer sensor array with 15 µm pixel size for MWIR imaging.

6. The system (100) as claimed in claim 1, wherein the primary aspheric convex mirror (112) and secondary concave mirror (114) both have hyperbolic reflective profiles, fabricated using CNC grinding and diamond turning techniques, and coated with AR or DLC coatings for spectral compatibility.

7. The system (100) as claimed in claim 1, wherein the optical system alignment is performed using laser interferometry and autocollimation techniques, with an axial tolerance of ±10 microns and a tilt tolerance of less than 0.01 degrees.

8. The system (100) as claimed in claim 1, wherein the optical surfaces are coated with broadband anti-reflective coating having reflectance less than 0.5% for visible applications and diamond-like carbon (DLC) or gold coating for MWIR applications with reflectance below 1%.

9. The system (100) as claimed in claim 1, wherein the system is configured for integration into 1U or 3U CubeSat form factors, with thermal management for MWIR sensors optionally provided using thermoelectric cooling (TEC) or a Stirling cooler to maintain a target sensor temperature near 80K.