Optical relay system

Abstract

A spectral shearing optical relay system is proposed, which is composed of two halves arranged symmetrically around an aperture stop S, where each half has a plurality of rotationally symmetric optical elements forming an objective lens and a compound prism composed of a plurality of dispersive prisms. The compound prism is arranged between the objective lens and the aperture stop. An imaging device including such an optical relay system has also been proposed.

Description

[Technical Field]

[0001] This application claims priority to U.S. Patent Application No. 17 / 118,900, filed on 11 December 2020. The disclosures of U.S. Patent Application No. 17 / 118,900 are incorporated herein by reference in their entirety.

[0002] This invention relates to an optical relay system. [Background technology]

[0003] A coded aperture snapshot spectral imager (CASSI) is a computational imaging system that acquires a three-dimensional (3D) spectral data cube through one or more two-dimensional (2D) measurements.

[0004] A typical overall optical architecture includes an imaging lens that frames the scene onto a mask, a relay optical system with a dispersion element that relays the masked image through the dispersion element, and sensors for detecting the masked and sheared images. The original data cube is reconstructed by an algorithm from the sensor input.

[0005] The use of relay lenses and dispersion prisms in CASSI instruments is well known. The dispersion element may be a composite prism. The "pixels" on the mask are matched to the pixels (or 2x2 bins) of the sensor. The use of regular prisms will reduce the sharpness of the image, which will result in undesirable optical effects such as anomalous image distortion and lateral chromatic aberration, leading to relatively difficult and nonlinear reconstruction.

[0006] Conventional relay systems used in spectroscopy are adequately compensated for relaying slit-shaped signals. However, especially in the case of relayed image corners, little information is found to relay and distribute the quality of rectangular (image) shaped signals.

[0007] In the reference "Ashwin A Wagadarikar, Nikos P Pitsianis, Xiaobai Sun, and David J Brady, “Video rate spectral imaging using a coded aperture snapshot spectral imager,” Optics express, 17(8):6368-6388, 2009", Schott From (Registered Trademark) Company N-SK2 and N-SK4 glass are used.

[0008] A series of publications by Hagen and Tkaczyk, titled “Compound prism design principles, I,” Applied Optics, 50, 24, 4998-5011, “Compound prism design principles, II: triplet and Janssen prisms,” Applied Optics, 50, 24, 5012-5022, and “Compound prism design principles, III: linear-in-wavenumber and optical coherence tomography prisms,” Applied Optics, 50, 25, 5023-5030, describe the design of dispersion prisms useful in these systems.

[0009] The current system's shortcomings are the spatial aberrations introduced by the reflection system and the expenditure on transmission systems such as prism-photon-prism (PGP) systems. The current system's optical throughput is insufficient.

[0010] Most coded aperture hyperspectral imaging systems have asymmetric relay systems that are largely dominated by axial chromatic aberration or rely on gratings for dispersion, which significantly compromises optical throughput. [Overview of the Initiative]

Problems to be Solved by the Invention

[0011] One object of the present invention is to propose an optical relay system suitable for image relay or encoding apertures adapted to correct, in particular, "smile" and / or "keystone" distortion along a plane.

[0012] One object of the present invention is to overcome or at least mitigate the drawbacks associated with known shear optical relay systems.

Means for Solving the Problems

[0013] The present invention proposes a relay system according to claim 1 and an imaging device having such a relay system.

[0014] According to a first aspect of the present disclosure, a spectral shear optical relay system is provided, the relay system being composed of two halves symmetrically arranged about an aperture stop S, where each half has a plurality of rotationally symmetric optical elements forming an objective lens and a composite prism composed of a plurality of dispersive prisms. The composite prism is arranged between the objective lens and the aperture stop.

[0015] Such a relay system provides a bright aperture and improved image sharpness, which is particularly interesting when used in an imaging device such as an encoding aperture spectrometer. By constraining the entire optical system to be approximately symmetric about the aperture stop, many aberrations are reduced to approximately zero.

[0016] The dispersive prism is designed to simultaneously provide the required spectral shear and allow the optical aberrations generated by the prism to be corrected by the rotationally symmetric optical components, thereby providing a properly spectrally sheared image with high sharpness.

[0017] In one embodiment, the light beam incident on the composite prism is collimated. The advantage is that the collimated light beam introduces negligible amounts of spherical aberration and coma into the design, resulting in a relatively good overall design correction for sharpness.

[0018] In another embodiment, at least one of the following conditions is satisfied: the composite prism exhibits a virtually zero deviation of the axial principal rays at the central wavelength, and the principal rays at the endpoints of the spectral range deviate in such a way that they spectrally shear the image.

[0019] In yet another embodiment, at least one of the following conditions is satisfied: the multiple prisms forming the composite prism have a small difference in refractive index at the central wavelength, specifically, the difference in refractive index at the central wavelength is <0.001; and the multiple prisms have a relatively large difference in refractive index at the endpoint of the spectral range, specifically, the difference in refractive index between the endpoint of the spectral range and the central wavelength is 0.003 to 0.007.

[0020] The use of glass with anomalous partial dispersion allows for a high degree of chromatic aberration correction.

[0021] The outer surface of the composite prism can be perpendicular to the optical axis, and preferably, in this case, the outer surface of the composite prism is perpendicular to the optical axis within 0.1°. By constraining the shape and material of each prism in the system to appear as a nearly plain parallel plate with a constant refractive index at the central wavelength, a high degree of monochromatic aberration correction by the rotationally symmetric optical component is permitted.

[0022] In one embodiment, the objective lens is composed of five rotationally symmetric lens elements, in which the first and second lens elements form a first doublet, and the third and fourth lens elements form a second doublet, in which the first and second doublets house a single glass having anomalous partial dispersion, and the fifth lens is a positive singlet.

[0023] The fifth lens may have a weak aspherical surface. The aspherical surface allows for a relatively brighter image.

[0024] The use of rotationally symmetric optical components reduces manufacturing costs.

[0025] In one embodiment, the relay optics system provides a diffraction-limited relay over the range of 400 to 1000 nm. The composite prism is corrected for use in the 400 nm to 1000 nm range, and in this case, the composite prism is - Schott for external prism elements From (Registered Trademark) Company Schott for N-SK4 and internal prism elements From (Registered Trademark) Company Equivalent glass from N-KzFS4 or other manufacturers, - Schott for external prism elements From (Registered Trademark) Company Schott for N-BAF51 and internal prism elements From (Registered Trademark) Company Transparent glass from N-KzFS5 or other manufacturers, or - Schott for external prism elements From (Registered Trademark) Company Schott for N-BK10 and internal prism elements From (Registered Trademark) Company Equivalent glass from N-PK52A or other manufacturers, It consists of an external prism element and an internal prism element manufactured from one of the following combinations.

[0026] In a further embodiment where the system is designed for use in the 400nm-1000nm range, the two measures of refractive index dispersion are: v700=(n700-1) / (n400-n700), P700 = (n400 - n700) / (n400 - n1000) It can be defined as follows, in which case n400, n700, and n1000 are the refractive indices at 400nm, 700nm, and 1000nm, and the objective lens is -1.73 < ΦD1 / Φobjective < -1.57 0.92 < ΦD2 / Φobjective < 1.01 0.89 < ΦL5 / Φobjective < 0.98 n700 for L1 > 1.85 |ΔP700 / Δν700| < 0.007 for D1 |ΔP700 / Δν700| < 0.0001 in the case of D2 v700>24 for L5 It is possible to satisfy this expression, in which case Φobjective is the refractive power of the objective lens, ΦD1 is the refractive power of the first doublet (D1), ΦD2 is the refractive power of the second doublet (D2), ΦL5 is the refractive power of the singlet (L5), and the ΔP700 / Δν700 of the doublet is the difference in P700 obtained by dividing by the difference in v700 of the two glasses having the doublet.

[0027] A spectral shear relay system can be telecentric on both the subject and the image.

[0028] In another embodiment, the relay optics system provides diffraction-limited relay over the short-wave infrared range, corrected for use in the 900–1700 nm range. In this range, the composite prism is a Schott for the external prism element. From (Registered Trademark) Company Schott for N-SF66 and internal prism elements From (Registered Trademark) Company It can be composed of external and internal prism elements made from N-LASF31A or equivalent glass from other manufacturers.

[0029] The relay optics system allows for high-resolution, high-brightness, spectral shear relay systems that can be manufactured at a relatively low cost. The relay optics system consists of custom-designed lenses and prisms and includes two (identical) aspherical surfaces, thereby avoiding shape distortion and lateral chromatic aberration.

[0030] Furthermore, the present invention proposes an imaging device having such an optical relay system. Such an imaging device may be a tomography imager or an encoded aperture imaging device.

[0031] Features of any aspect (including optional features) may be combined with any other aspect as appropriate.

[0032] An illustrative embodiment will be described with reference only to the following drawings. [Brief explanation of the drawing]

[0033] [Figure 1] Figure 1 is a schematic diagram of an imaging device according to one embodiment.

[0034] [Figure 2] Figure 2 is a schematic diagram of a relay device according to one embodiment in a spectral shear plane.

[0035] [Figure 3] Figure 3 is a schematic diagram of the apparatus shown in Figure 2 in one embodiment for a non-spectral shear plane.

[0036] [Figure 4] Figure 4 shows the shear direction dispersion for the axial subject point in the apparatus of Figures 2 and 3 according to one embodiment.

[0037] [Figure 5] Figure 5 is a spot diagram at multiple wavelengths showing the effect of residual transverse color on spectral shear using the apparatus shown in Figures 2 and 3 according to one embodiment.

[0038] [Figure 6] Figure 6 shows the strain performance at multiple wavelengths associated with the apparatus shown in Figures 2 and 3 according to one embodiment.

[0039] [Figure 7A] Figure 7A shows the sharpness performance at multiple wavelengths as MTF (Modulation Transfer Function) for the apparatus shown in Figures 2 and 3. [Figure 7B] Figure 7B shows the sharpness performance at multiple wavelengths as MTF (Modulation Transfer Function) for the apparatus shown in Figures 2 and 3. [Figure 7C] Figure 7C shows the sharpness performance at multiple wavelengths as MTF (Modulation Transfer Function) for the apparatus shown in Figures 2 and 3. [Figure 7D] Figure 7D shows the sharpness performance at multiple wavelengths as MTF (Modulation Transfer Function) for the apparatus shown in Figures 2 and 3.

[0040] [Figure 8] Figure 8 shows the refractive index properties of prism materials that can be used in the relays of Figures 2 and 3. [Modes for carrying out the invention]

[0041] Please note that the figures are schematic and not to scale. Generally, the same reference numerals are used to mean corresponding or similar features in modified and different embodiments.

[0042] Figure 1 shows an imaging device 1 according to one embodiment.

[0043] The imaging device 1 may be a hyperspectral imaging device, in which case the coding aperture plate 2 forms the subject to be relayed by the optical relay 10 to the image in the detector 4.

[0044] The optical relay 10 is adapted to spectrally shear the image in one orientation across the detector, in which case the detector has a sufficiently broad spectral response for all sheared wavelengths.

[0045] The optical relay is an optical spectral shearing system, as shown in Figures 2 and 3.

[0046] According to one embodiment of the present invention, Figure 2 shows the optical spectral shear relay system 10 in a spectral shear plane, and Figure 3 shows the optical spectral shear relay system 10 in a non-spectral shear plane.

[0047] The optical spectral shear relay system 10 shown in Figures 2 and 3 comprises a plurality of composite prisms 31 and a plurality of rotationally symmetric lens elements L1, L2, L3, L4, and L5, each of which is used twice and arranged symmetrically around the aperture diaphragm S.

[0048] In other words, the optical spectral shearing system 10 has two halves arranged symmetrically around the aperture diaphragm S.

[0049] Each half consists of an objective lens 21 and a composite prism 31, and its design is described in detail below.

[0050] The composite prism 31 is a joined composite prism formed by an external prism element P1 on the objective lens side and an internal prism element P2 on the aperture diaphragm side.

[0051] The outer surface 22 of the composite prism 31 is almost perpendicular to the optical axis. Therefore, at the central wavelength of the spectral band, the composite prism has an appearance almost identical to that of plain parallel plates formed from the same material and arranged symmetrically around the aperture.

[0052] Specifically, the external prism surface on the external prism element P1 is tilted from the perpendicular to the optical axis by less than 0.1°, preferably less than 0.05°, which allows for good correction of residual aberrations by a rotationally symmetric optical element elsewhere in the system.

[0053] Having a relatively large external prism surface tilt affects aberration correction. For example, the combination of N-BAF51 and N-KzFS5 requires approximately twice the external prism surface tilt, and this combination also results in relatively low dispersion. The combination of N-BK10 and N-PK52A has relatively low external prism surface tilt, but results in minimal total dispersion.

[0054] Furthermore, the external prism surface of the internal prism element P2 is inclined by less than 0.1°, preferably less than 0.05°, from perpendicular to the optical axis. Preferably, the external prism surface of the internal prism element P2 is perpendicular to the optical axis.

[0055] The symmetrical arrangement of lens elements, including a plane parallel plate centered around the aperture, automatically corrects coma, distortion, and lateral color in the optical system. Therefore, at the central wavelength, the optical system exhibits negligible amounts of coma and distortion.

[0056] The desired spectral shear in one dimension is generated by the dispersion action of the prism and is equivalent to the transverse color in only one dimension. The rotationally symmetric transverse color contributed by other components of the design is small and insignificant in relation to the spectral shear by the prism.

[0057] The remaining aberrations can be corrected by rotationally symmetric lens elements manufactured using techniques well known in the field of optical design and by conventional optical manufacturing methods.

[0058] In the embodiments shown in Figures 2 and 3, the composite prism is designed such that there is essentially no deviation of the principal ray of the axial flux at the central wavelength, and there is a deviation of approximately 0.7° of the principal ray of the axial flux between the shorter and longer wavelengths.

[0059] The range and profile of the refractive index determine the dispersion and linearity of the dispersion that the prism provides to the optical system.

[0060] The composite prism 31 is composed of multiple materials. The difference in refractive index between the materials of the outer prism element P1 and the inner prism element P2 at the central wavelength of the spectral band is small between the materials. The difference in refractive index increases with deviation from the central wavelength of the spectral band. For example, a small difference in refractive index between two prism materials is less than 0.001 at the central wavelength and 0.003 to 0.007 at the end of the overall spectral range from 400 nm to 1000 nm.

[0061] In the embodiments shown in Figures 2 and 3, the small difference in refractive index between the external prism element P1 and the internal prism element P2 at the central wavelength is due to the Schott for P1. From (Registered Trademark) Company Schott for N-SK4 and P2 From (Registered Trademark) Company This is obtained using N-KzFS4. Schott for P1 From (Registered Trademark) Company Schott for N-KZFS4 and P2 From (Registered Trademark) Company Using N-SK4 yields equally good results. Other good Schott materials for similar composite prisms. From (Registered Trademark) CompanyGlass options include N-BAF51+N-KzFS5 and N-BK10+N-PK52A. Furthermore, as is well known to those skilled in the art of optical design, glasses from other glass manufacturers with similar refractive index profiles in the 400–1000 nm range can also be used with good results. Figure 8 summarizes some of the refractive index properties of these materials. All of these combinations exhibit small differences in refractive index at a central wavelength of 700 nm, preferably less than 0.001.

[0062] The combination of N-Sk4 and N-KzFS4 has been found to be a good option for satisfying the design criteria for the combined prism spectral range of 400nm to 1000nm.

[0063] Furthermore, this combination of N-Sk4 and N-KzFS4 prism glass imparts most of the dispersion and, therefore, the maximum number of spectral channels within a fixed optical system length. The difference in refractive index between the two glasses across the spectral range (0.003–0.007 at the edges of the overall spectral range from 400nm to 1000nm) was also small enough to maintain the prism in a state that closely resembled a plain parallel plate, allowing for good aberration correction by a rotationally symmetric optical element elsewhere in the system.

[0064] The internal prism angle between the external prism element P1 and the internal prism element P2 can be small enough to keep the overall prism size reasonably compact. A small angle can be defined as being within 60 degrees from the perpendicular P1 / P2 surface. As the prism increases in size, it becomes longer than its height, resulting in a further increase in the optical path length.

[0065] The embodiments in Figures 2 and 3 operate in the 400 nm to 1000 nm range. The dispersion in the shear direction is 240 μm, which allows for 50 spectral channels by using a 4.8 μm × 4.8 μm detection element in detection. This operates with an effective F-number of f / 4.2 over a 4.92 × 4.92 mm subject-side field of view. Figure 4 shows the dispersion in the image in the shear direction for an axial subject point. Figure 5 is a spot diagram at multiple wavelengths showing the effect of residual transverse color on spectral shear. Figure 6 shows the distortion performance at multiple wavelengths.

[0066] Figures 7A to 7D show the sharpness performance as Modulation Transfer Function (MTF) at multiple wavelengths, including diffraction-limited performance for comparison. In addition to sharpness, high MTF minimizes spectral crosstalk between detector elements. The combination of spectral shear performance, low distortion, and high MTF allows subsequent signal processing to extract high-quality hyperspectral images.

[0067] In one embodiment, a relay system operating in the short-wavelength infrared range of 900 to 1700 nm has also been proposed. In this operating range, the prism composite preferably uses Schott for the external prism element. From (Registered Trademark) Company Schott for N-SF66 and internal prism elements From (Registered Trademark) Company It is manufactured from N-LASF31A or equivalent glass from other manufacturers. It should be noted that within this operating SWIR range, the required dispersion necessitates a very large angle between the two glass elements of the composite prism, resulting in relatively long outer and inner prisms. The internal transmittance of the prisms at these lengths drives the low overall system transmittance. Transmittance cannot be improved by coating.

[0068] The conventional relay systems between coding aperture plates and detectors, as shown in the prior art, do not have an external prism surface nearly perpendicular to the optical axis when the refractive indices of the prism elements are matched at the central wavelength of the spectral band, or they utilize the principle of symmetry in optical design. The present system invention provides improvements in aperture, field of view, and sharpness compared to the prior art.

[0069] The objective lens 21 is composed of five rotationally symmetric lens elements L1, L2, L3, L4, and L5. The objective lens 21 has a negative doublet D1 made from the first and second lens elements L1 and L2, a positive doublet D2 made from the third and fourth lens elements L3 and L4, and the fifth lens element L5 is a positive singlet.

[0070] A positive singlet has a surface opposite the prism, which may be aspherical. The aspherical surface allows for a relatively brighter image, which helps correct for spherical aberration. In addition, this reduces the size of the relay system.

[0071] It should be noted that aspherical surfaces for singlet elements are preferred in the range of 400 to 900 nm, and optional in the range of 900 to 1700 nm.

[0072] By joining the first and second lens elements L1 and L2 and the third and fourth lens elements L3 and L4 to form a doublet, strict precision requirements can be avoided, and the number of air-glass interfaces for the AR coating is reduced.

[0073] Each doublet, D1 and D2, contains one glass element exhibiting anomalous partial dispersion.

[0074] The objective lens 21 supplies a collimated beam to the prism 31 from various field points. The advantage is that the collimated beam introduces negligible amounts of spherical aberration and coma into the design, resulting in relatively good overall design correction for sharpness. In fact, as shown in some prior art, spherical aberration and coma are introduced into the image by placing a prism in a converged beam within an object or image space. Correcting these aberrations to achieve equivalent sharpness in the embodiments shown in Figures 2 and 3 would otherwise require a significantly more complex and costly optical design. Failure to correct them would result in a degradation of sharpness.

[0075] Furthermore, the aperture diaphragm S is positioned in relation to the base point of the objective lens 21 to provide a nearly telecentric system in both the subject and image space. The advantage of double telecentricity is that, when used in a CASSI system such as the hyperspectral imaging device 1, the magnification of the optical system spectral shear system 1 is not sensitive to the longitudinal shift of the coding aperture plate 2 or the detector 3. This is helpful for the assembly and calibration of the entire system.

[0076] Note that windows in image space can be replaced by thicknesses equivalent to air, and therefore do not have a significant impact on symmetry.

[0077] The symmetrical arrangement of lens elements, including a plane parallel plate centered around the aperture, automatically corrects coma, distortion, and lateral color in the optical system. Therefore, at the central wavelength, the optical system exhibits negligible amounts of coma and distortion.

[0078] The use of rotationally symmetric optical components reduces manufacturing costs.

[0079] Correction of chromatic aberration over a wide wavelength range of 400 nm to 1000 nm can be obtained when the design of the objective lens 21 satisfies specific conditions. Two measures of refractive index dispersion are v , 700 , L5 , , 700 , D1 , objective , 1000 , , objective , 400 , , objective , 700 , 700 , , 700 , 700 , 700 , 700 , , L5 , D2 , D2 , objective , , D1 , 700 , ,

[0080] =(n 700 -1) / (n 400 -n 700 ), P 700 =(n 400 -n 700 ) / (n 400 -n 1000 ) and are defined as such, where n 400 , n 700 , and n 1000 are the refractive indices at 400 nm, 700 nm, and 1000 nm.

[0080] [[ID=​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​700 |<0.0001 v for L5 700 >24

[0081] Lens L5 has a weak aspherical surface to assist in correcting spherical aberration. Relays with relatively low numerical aperture or relatively low sharpness requirements do not require this aspherical surface.

[0082] In short, for systems operating in the 400-1000 nm range, the objective lens is preferably a Schott lens for the first lens element L1 for the first doublet. From (Registered Trademark) Company Schott for N-LASF46B and second lens element From (Registered Trademark) Company Equivalent glass from N-KZFS4 or other manufacturers, Schott for the third lens element L3 for the second doublet D2. From (Registered Trademark) Company Schott for N-PK51 and fourth lens element L4 From (Registered Trademark) Company Equivalent glass from N-KZFS11 or other manufacturers, Schott for lens element L5. From (Registered Trademark) Company It has glass equivalent to NPK51 or other manufacturers' glass.

[0083] Prism combinations for systems operating in the 400-1000 nm range preferably include Schott prisms for the external prism elements. From (Registered Trademark) Company Schott for N-SK4 and internal prism elements From (Registered Trademark) Company Equivalent glass from N-KzFS4 or other manufacturers, Schott for external prism elements. From (Registered Trademark) Company Schott for N-BAF51 and internal prism elements From (Registered Trademark) Company Equivalent glass from N-KzFS5 or other manufacturers, and Schott glass for external prism elements. From (Registered Trademark) Company N-BK10 and Schott internal prism elements From (Registered Trademark) Company It is selected from one of the following combinations: N-PK52A or equivalent glass from other manufacturers.

[0084] In short, the spectral shear relay system can have an optical configuration of L1:N-LASF46B, L2:N-KZFS4, L3:N-PK51, L4:N-KZFS11, L5:N-PK51, equivalent glass, and one of the prism combinations described above.

[0085] The relay design, which operates in the 400-1000nm range, is compact, and in this case, the distance between the subject and the image is 99mm.

[0086] In another embodiment, the alternative relay system is designed to operate in a short infrared system of 900–1700 nm, in which case the distance between the subject and the image is approximately 277 mm. In fact, within this range, the required dispersion requires a very large angle between the two glass panes of the composite prism, resulting in relatively long outer and inner prisms.

[0087] For relay systems operating in the 900-1700 nm range, the objective lens is preferably a Schott lens for the first lens element L1. From (Registered Trademark) Company Schott for N-LASF31A and second lens element (L2) From (Registered Trademark) Company N-KZFS4 (Doublet 1), Schott L3 third lens element From (Registered Trademark) Company Schott for N-FK51A and fourth lens element L4 From (Registered Trademark) Company Schott for N-KZFS11 (Doublet 2) and the 5th lens element L5 From (Registered Trademark) Company It has glass called N-FK51A (singlet). The prism composite preferably has Schott glass for the external prism element. From (Registered Trademark) Company Schott for N-FS66 and internal prism elements From (Registered Trademark) Company It is manufactured from N-LASF31A or equivalent glass from other manufacturers.

[0088] In short, the present invention proposes a shear optical system having rotationally symmetric lens elements and composite prisms that form not only a sharp image but also a spectrally sheared image in one direction. It operates at 1x magnification and, due to its double telecentricity, the magnification is insensitive to longitudinal shifts of the subject or image during assembly. The effect of the window on the overall performance is not significant. This is to support the assembly and calibration of the entire system.

[0089] Further references include the following: ·Wagadarikar, John, Willet, and Brady, “Single disperser design for coded aperture snap-shot”, Applied Optics, 47, 10, B44-B51 (2008) ·Kittle, Cho, Wagadarikar, and Brady, “Multiframe image estimation for coded aperture snapshot spectral imagers”, Applied Optics, 49, 36, 6824-6833 (2010) ·Kester, Bedard, Gao, Tkacyzk, “Real-time snapshot hyperspectral imaging endoscope”, Journal of Biomedical Optics, 16, 5, 056005-1-12 (2011), and ·Arce, Brady, Carin, Arguello, Kittle, Compressive Coded Aperture Spectral Imaging, IEEE Signal Processing Magazine, 105-115 (2014)

[0090] The above description relating to preferred embodiments of the present invention is provided for illustrative and explanatory purposes only. It is not intended to exhaust the entirety of the present invention or to limit it to the disclosed form, and in view of the above teachings, modifications and variations are possible or can be obtained from the practice of the present invention. The embodiments are selected and described to illustrate the principles of the present invention and their practical applications in order to enable those skilled in the art to utilize the present invention in various embodiments suitable for specific uses envisioned. The scope of the present invention is intended to be defined by the appended claims and their equivalents. Each of the above-mentioned documents is incorporated herein by reference in its entirety. The inventions disclosed herein include the following: [Aspect 1] A spectral shear optical relay system, wherein the optical relay system is composed of two halves arranged symmetrically around an aperture diaphragm, and each of the two halves has a composite prism composed of a plurality of rotationally symmetric optical elements forming an objective lens and a plurality of dispersion prisms. The composite prism is positioned between the objective lens and the aperture diaphragm in the system. [Aspect 2] The spectral shear light relay system according to embodiment 1, wherein the light beam incident on the composite prism is collimated. [Aspect 3] The composite prism exhibits essentially zero deviation of the axial principal rays at the central wavelength, and, The principal ray at the end of the spectral range deviates in a way that causes spectral shearing of the image. A spectral shear light relay system according to embodiment 1, wherein at least one of the following conditions is satisfied. [Aspect 4] The plurality of prisms forming the composite prism have a small difference in refractive index at the central wavelength, specifically, the difference in refractive index at the central wavelength is <0.001, and The aforementioned plurality of prisms have a relatively large difference in refractive index at the end of the spectral range. A spectral shear light relay system according to embodiment 1, wherein at least one of the following conditions is satisfied. [Aspect 5] The spectral shear optical relay system according to embodiment 4, wherein the difference in refractive index between the endpoint of the spectral range and the center wavelength is 0.003 to 0.007. [Aspect 6] The spectral shear optical relay system according to embodiment 1, wherein the outer surface of the composite prism is perpendicular to the optical axis. [Aspect 7] The spectral shear optical relay system according to embodiment 6, wherein the outer surface of the composite prism is substantially perpendicular to the optical axis within 0.1°. [Aspect 8] The spectral shear optical relay system according to Embodiment 1, wherein the objective lens is composed of five rotationally symmetric lens elements (L1, L2, L3, L4, L5), the first and second lens elements (L1, L2) form a first doublet (D1), the third and fourth lens elements (L3, L4) form a second doublet (D2), the first and second doublets (D1, D2) each have a glass having anomalous partial dispersion, and the fifth lens element is a positive singlet. [Aspect 9] The spectral shear light relay system according to embodiment 8, wherein the fifth lens element has a weak aspherical surface. [Aspect 10] The composite prism is corrected for use in the 400nm to 1000nm range, and the composite prism is, - N-SK4 from Schott® for external prism elements and N-KzFS4 from Schott® or equivalent glass from other manufacturers for internal prism elements. - N-BAF51 from Schott® for the external prism element and N-KzFS5 from Schott® for the internal prism element or equivalent glass from other manufacturers, - N-BK10 from chott® for the external prism element and N-PK52A from chott® or equivalent glass from other manufacturers for the internal prism element. A spectral shear light relay system according to Embodiment 1, comprising the external prism element and the internal prism element manufactured from one of the combinations thereof. [Aspect 11] The two measures of refractive index dispersion are: v700=(n700-1) / (n400-n700), P700 = (n400 - n700) / (n400 - n1000) Defined as, where n400, n700, and n1000 are the refractive indices at 400 nm, 700 nm, and 1000 nm, and in this case, the objective lens is, -1.73<Φ D1 / Φ objective <-1.57 0.92<Φ D2 / Φ objective <1.01 0.89<Φ L5 / Φ objective <0.98 n for L1 700 >1.85、 |Δ in the case of D1 P700 / Δv 700 |<0.007 |ΔP in the case of D2 700 / Δv 700 |<0.0001 v for L5 700 >24 This expression satisfies the condition, and in this case, Φ objective Φ is the refractive power of the objective lens. D1 Φ is the refractive power of the first doublet (D1), and D2 Φ is the refractive power of the second doublet (D2), and L5 This is the refractive power of the singlet (L5), and also ΔP for the doublet. 700 / Δv 700 The v for the two glasses having the doublet 700 The P divided by the difference 700 The spectral shear optical relay system described in Embodiment 4, which is the difference. [Aspect 12] The spectral shear light relay system according to embodiment 1, wherein the spectral shear light relay system is telecentric on both the subject side and the image side. [Aspect 13] A spectral shear optical relay system according to embodiment 1, corrected for use in the 900-1700 nm range. [Aspect 14] The spectral shear light relay system according to embodiment 13, wherein the composite prism comprises the external prism element and the internal prism element, which are manufactured from N-SF66 from chott® for the external prism element and N-LASF31A from chott® or equivalent glass from other manufacturers for the internal prism element. [Aspect 15] An imaging apparatus having an optical relay system, wherein the optical relay system has two halves arranged symmetrically around an aperture diaphragm, each of the two halves having a composite prism composed of a plurality of rotationally symmetric optical elements forming an objective lens and a plurality of dispersion prisms, and the composite prism is positioned between the objective lens and the aperture diaphragm.

Claims

1. A spectral shear optical relay system, wherein the spectral shear optical relay system is composed of two halves arranged symmetrically around an aperture diaphragm, and each of the two halves has a composite prism composed of a plurality of rotationally symmetric optical elements forming an objective lens and a plurality of dispersion prisms. The composite prism is positioned between the objective lens and the aperture diaphragm. The plurality of dispersion prisms forming the composite prism have a difference in refractive index at the central wavelength, and the difference in refractive index at the central wavelength is <0.001, and The plurality of dispersion prisms have a difference in refractive index between one of the endpoints of the spectral range and the central wavelength, and the difference in refractive index between one of the endpoints of the spectral range and the central wavelength is 0.003 to 0.

007. At least one of the following conditions is met: The objective lens is composed of five rotationally symmetric lens elements (L1, L2, L3, L4, L5), where the first lens element (L1) manufactured from the first glass and the second lens element (L2) manufactured from the second glass form a first doublet (D1), the third lens element (L3) manufactured from the third glass and the fourth lens element (L4) manufactured from the fourth glass form a second doublet (D2), and the fifth lens element is a positive singlet (L5). The two measures of refractive index dispersion are: v700=(n700-1) / (n400-n700), P700=(n400-n700) / (n400-n1000) Defined as, where n400, n700, and n1000 are the refractive indices at 400 nm, 700 nm, and 1000 nm, and in this case, the objective lens is, -1.73<Φ Ｄ１ / F ｏｂｊｅｃｔｉｖｅ <-1.57 0.92<Φ Ｄ２ / F ｏｂｊｅｃｔｉｖｅ <1.01 0.89<Φ Ｌ５ / F ｏｂｊｅｃｔｉｖｅ <0.98 n for L1 ７００ > 1.85, |Δ in the case of D1 Ｐ７００ / Δv ７００ | < 0.007 |ΔP in the case of D2 ７００ / Δv ７００ | < 0.0001 v for L5 ７００ >24 This expression satisfies the condition, and in this case, Φ ｏｂｊｅｃｔｉｖｅ Φ is the refractive power of the objective lens, Ｄ１ Φ is the refractive power of the first doublet (D1), and Ｄ２ Φ is the refractive power of the second doublet (D2), Ｌ５ This is the refractive power of the positive singlet (L5), and ΔP for the first doublet (D1). ７００ / Δv ７００ The v for the first glass of the first lens element (L1) and the second glass of the second lens element (L2) ７００ The P divided by the difference ７００ A spectral shear optical relay system, wherein the difference is and the ΔP 700 / Δv 700 for the second doublet (D2) is the difference of P 700 divided by the difference of v 700 for the third glass of the third lens element (L3) and the fourth glass of the fourth lens element (L4).

2. The spectral shear light relay system according to claim 1, wherein the light beam incident on the composite prism is collimated.

3. The composite prism exhibits essentially zero deviation of the axial principal rays at the central wavelength, and, The principal ray at the end of the spectral range deviates in a way that causes spectral shearing of the image. The spectral shear optical relay system according to claim 1, wherein at least one of the following conditions is satisfied.

4. The spectral shear optical relay system according to claim 1, wherein the outer surface of the composite prism is perpendicular to the optical axis.

5. The spectral shear optical relay system according to claim 4, wherein the outer surface of the composite prism is substantially perpendicular to the optical axis within 0.1°.

6. The spectral shear optical relay system according to claim 1, wherein the first glass of the first lens element (L1) or the second glass of the second lens element (L2) has anomalous partial dispersion, and the third glass of the third lens element (L3) or the fourth glass of the fourth lens element (L4) has anomalous partial dispersion.

7. The spectral shear light relay system according to claim 6, wherein the fifth lens element has a weak aspherical surface.

8. The composite prism is corrected for use in the range of 400 nm to 1000 nm, and the composite prism is composed of an external dispersion prism and an internal dispersion prism, and the external dispersion prism and the internal dispersion prism are - N-SK4 from Schott® for the external dispersion prism and N-KzFS4 from Schott® for the internal dispersion prism or equivalent glass from other manufacturers, - N-BAF51 from Schott® for the external dispersion prism and N-KzFS5 from Schott® for the internal dispersion prism or equivalent glass from other manufacturers, - N-BK10 from Schott® for the external dispersion prism and N-PK52A from Schott® for the internal dispersion prism or equivalent glass from other manufacturers, A spectral shear optical relay system according to claim 1, manufactured from one of the following combinations.

9. The spectral shear light relay system according to claim 1, wherein the spectral shear light relay system is telecentric on the subject side and the image side.

10. The spectral shear optical relay system according to claim 1, which is corrected for use in the range of 900 to 1700 nm.

11. The spectral shear optical relay system according to claim 10, wherein the composite prism comprises an external dispersion prism and an internal dispersion prism, and the external dispersion prism and the internal dispersion prism are manufactured from Schott® N-SF66 for the external dispersion prism, Schott® N-LASF31A for the internal dispersion prism, or equivalent glass from another manufacturer.

12. An imaging device having an optical relay system, wherein the optical relay system has two halves arranged symmetrically around an aperture diaphragm, each of the two halves having a composite prism composed of a plurality of rotationally symmetric optical elements forming an objective lens and a plurality of dispersion prisms, and the composite prism is positioned between the objective lens and the aperture diaphragm. The plurality of dispersion prisms forming the composite prism have a difference in refractive index at the central wavelength, and the difference in refractive index at the central wavelength is <0.001, and The plurality of dispersion prisms have a difference in refractive index between one of the endpoints of the spectral range and the central wavelength, and the difference in refractive index between one of the endpoints of the spectral range and the central wavelength is 0.003 to 0.

007. At least one of the following conditions is met: The objective lens is composed of five rotationally symmetric lens elements (L1, L2, L3, L4, L5), where the first lens element (L1) manufactured from the first glass and the second lens element (L2) manufactured from the second glass form a first doublet (D1), the third lens element (L3) manufactured from the third glass and the fourth lens element (L4) manufactured from the fourth glass form a second doublet (D2), and the fifth lens element is a positive singlet (L5). The two measures of refractive index dispersion are: v700=(n700-1) / (n400-n700), P700=(n400-n700) / (n400-n1000) Defined as, where n400, n700, and n1000 are the refractive indices at 400 nm, 700 nm, and 1000 nm, and in this case, the objective lens is, -1.73<Φ Ｄ１ / F ｏｂｊｅｃｔｉｖｅ <-1.57 0.92<Φ Ｄ２ / F ｏｂｊｅｃｔｉｖｅ <1.01 0.89<Φ Ｌ５ / F ｏｂｊｅｃｔｉｖｅ <0.98 n for L1 ７００ > 1.85, |Δ in the case of D1 Ｐ７００ / Δv ７００ | < 0.007 |ΔP in the case of D2 ７００ / Δv ７００ | < 0.0001 v for L5 ７００ >24 This expression satisfies the condition, and in this case, Φ ｏｂｊｅｃｔｉｖｅ Φ is the refractive power of the objective lens, Ｄ１ Φ is the refractive power of the first doublet (D1), and Ｄ２ Φ is the refractive power of the second doublet (D2), Ｌ５ This is the refractive power of the positive singlet (L5), and ΔP for the first doublet (D1). ７００ / Δv ７００ The v for the first glass of the first lens element (L1) and the second glass of the second lens element (L2) ７００ The P divided by the difference ７００ An imaging device in which the difference is and the ΔP 700 / Δv 700 for the second doublet (D2) is the difference of P 700 divided by the difference of v 700 for the third glass of the third lens element (L3) and the fourth glass of the fourth lens element (L4).

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