Novel architecture of high-contrast star simulator

Abstract

The invention discloses a novel architecture of a high-contrast star simulator, and particularly belongs to the technical field of spacecraft ground simulation and calibration. The architecture comprises an exit pupil external collimation optical system, a depolarization optical engine and a computer control and data processing system. The optical engine is subjected to depolarization treatment, two 1 / 4 wave plates are arranged at the front end of the LCOS so as to restrain dark-state light leakage of the LCOS, the polarization stray light power is reduced to 4.62 * 10 <-5 > W from 2.5 * 10 <-4 > W by 5.41 times through arrangement of the depolarization beam splitter prism, and experimental results show that the polarization stray light power of the LCOS is greatly improved. Compared with an existing fixed star simulator, the high-contrast fixed star simulator has the advantages that the contrast is increased from 16.46: 1 to 93.41: 1, so that the depolarization optical engine can effectively inhibit stray light, and the contrast of a simulated star map is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of spacecraft ground simulation and calibration, and in particular to a novel architecture of a high-contrast star simulator. Background Art

[0002] At present, the micro-display devices of dynamic star simulators mainly include liquid crystal light valve (LCD), digital micromirror device (DMD) and liquid crystal on silicon (LCOS). Compared with LCD and DMD, LCOS has the characteristics of high resolution and fast response speed, and has become a commonly used dynamic star map display device. The existing dynamic star simulator uses an optical engine composed of LCOS, polarizing beam splitter (PBS), and illumination optical system, and cooperates with the exit pupil external collimation optical system to realize the dynamic simulation of star map.

[0003] The internal structure of LCOS is mainly composed of protective glass, electrodes and liquid crystal. After the silicon substrate is flattened by a special process, an aluminum film is coated on it as a reflector to form a CMOS substrate. The substrate is bonded to the protective glass containing a transparent electrode and injected into the liquid crystal package. The working principle of LCOS is: when no voltage is applied to both ends of the LCOS, the liquid crystal molecules in the LCOS do not deflect, and can be equivalent to an ideal plane mirror. When voltage is applied to both ends of the LCOS, the deflection angle of the liquid crystal molecules will gradually increase, realizing phase modulation of the incident light. Since the control electrode can be integrated into a very small silicon substrate, the pixel size of LCOS is much smaller than that of a transmissive spatial light modulator. Under the condition of the same volume, LCOS has a large resolution, few bad pixels, and a large filling factor. At the same time, it can make the light path reflect twice, and the thickness of the liquid crystal layer is smaller than that of the transmissive type, so the response speed of the liquid crystal is faster. However, in the actual application of LCOS, there is still a dark state leakage phenomenon, so it is necessary to establish the LCOS Jones matrix and derive the mathematical model of the LCOS dark state leakage amount and the incident wavelength. The dark state leakage amount R of the incident light after LCOS modulation can be expressed as

[0004] (1)

[0005] Where α is the angle between the transmission axis of the polarizer and the direction of the liquid crystal molecules at the incident point, (cosα, sinα) T is the Jones vector of the incident light, M is the Jones matrix of the LCOS liquid crystal molecule, and X is an intermediate variable.

[0006] X and M can be expressed as

[0007] ; (2)

[0008] ; (3)

[0009] Where φ1 is the twist angle of liquid crystal molecules.

[0010] Therefore, the dark state light leakage after the incident light is modulated by LCOS can be expressed as

[0011] ; (4)

[0012] When actually calculating the amount of dark state light leakage, the influence of different wavelengths should also be considered. Therefore, the human eye visual function is added to formula (1). At this time, the amount of LCOS dark state light leakage R lum It can be expressed as

[0013] ; (5)

[0014] Where f(λ) is the visual function of the human eye, and D(λ) is the spectral distribution of the light source.

[0015] The curve of the wavelength of LCOS reflected light and the amount of dark-state light leakage can be obtained from equation (5) when no compensation is added. Since LCOS has different response capabilities to incident light of different wavelengths, the amount of dark-state light leakage of LCOS is different for incident light of different wavelengths when it is in the dark state. Therefore, some light is still reflected by LCOS into the collimating optical system to form stray light. Therefore, in order to ensure that the dark-state light leakage of LCOS is fully suppressed, the phase of the LCOS reflected light needs to be compensated.

[0016] For the polarizing beam splitter (PBS), it can be seen from the Fresnel formula that when the light beam is reflected at the interface of two media, a phase difference will occur between the p component and the s component of the light wave. For the imaging optical system, the phase difference will undoubtedly have an adverse effect. Due to the existence of the phase difference, the reflected light gradually changes from linear polarized light to elliptically polarized light with increasing ellipticity. Compared with the polarization state of the incident light, it can be seen that the polarization state of the outgoing light changes significantly with the change of the incident angle. For the star simulator, this changing polarized light will cause the generation of image plane stray light after being emitted by the PBS, resulting in a layer of uneven stray light on the detector image plane, reducing the contrast of the image plane and affecting the imaging quality of the system.

[0017] The polarization beam splitter film plays a major role when PBS is working. Therefore, based on the working principle of the polarization beam splitter film, the mechanism of PBS stray light generation is studied. Under ideal conditions, the incident light of the existing star simulator PBS is polarized and split by the polarization beam splitter film and then incident on the LCOS. At this time, there is only P light in the transmission light path and only S light in the reflection light path. After being reflected by the LCOS, it is emitted from the polarization beam splitter film again.

[0018] After the light with a certain aperture angle is incident on the LCOS through the polarization splitter film, assuming that the transmittances of S light and P light are Tp and Ts respectively, and the reflectances are Rp and Rs respectively, the light reflected by the LCOS is mainly divided into the following two categories: one is the light reflected by the dark-state LCOS mainly composed of Ts and Rp, and the other is the light reflected by the bright-state LCOS mainly composed of Tp and Rs. The reflected light of the dark-state LCOS will form an image together with the reflected light of the bright-state LCOS to produce stray light.

[0019] Although the cause of stray light caused by the spectroscopic film can be analyzed in a broad sense, it is not intuitive at the mathematical level. Therefore, for the convenience of research, the Pauli matrix is ​​introduced here, as shown in the following formula:

[0020] ; (6)

[0021] In the formula, each item in the σ0~σ3 matrix can be associated with a certain characteristic state of polarization. The first item of the Pauli matrix represents the non-polarization item, that is, the geometric aberration part; the second item represents the S light and P light part; the third item represents the ±45° linear polarized light part; the fourth item represents the left-handed and right-handed circular polarization parts.

[0022] The Jones matrix J can be expressed as

[0023] ; (7)

[0024] In the formula, J xx , J xy , J yx , J yy is an intermediate parameter representing each item in the film Jones matrix.

[0025] Through the matrices σ0~σ3, the Jones matrix J can also be expressed as

[0026] ; (8)

[0027] By matching the coefficients of the Jones matrix with the coefficients of the Pauli matrix one by one, we can get that each item of the Pauli matrix is

[0028] ; (9)

[0029] ; (10)

[0030] ; (11)

[0031] ; (12)

[0032] The Jones matrix J1 of the film can be expressed as

[0033] ; (13)

[0034] Where A=(Tp) 1 / 2 exp(-iδ / 2), B=(Ts) 1 / 2 exp(iδ / 2), φ(0≤φ≤2π) is the aperture angle of the incident light, Tp and Ts are the transmittances of P and S light in the transmitted light field, Δ=(Δs+Δp) / 2 is the average phase, and δ=Δs-Δp is the phase difference.

[0035] Substituting formulas (9) to (12) into (13), Taylor expansion yields

[0036] ; (14)

[0037] ; (15)

[0038] ; (16)

[0039] ; (17)

[0040] In the formula, the real part of a0 represents the amplitude fluctuation caused by oblique incidence on the film, and the imaginary part represents the wavefront difference. a1 and a2 represent the vector aberration part, where the real part and imaginary part represent the transmittance attenuation and phase difference in the vector aberration respectively.

[0041] Therefore, when the incident light has a certain aperture angle, a1 and a2 are no longer 0, and the imaginary part of a0 is not 0. Therefore, after passing through the PBS, the polarization state of the outgoing light becomes elliptically polarized light whose amplitude phase changes with the radial coordinates of the pupil, resulting in the PBS containing both imaging polarized light and polarized stray light, which reduces the stray light suppression capability of the PBS and makes the existing PBS unable to match LCOS. Moreover, the mismatch between the outgoing light divergence angle of the illumination optical system and the PBS further promotes the conversion of elliptically polarized light. Therefore, the main research direction for suppressing PBS stray light is to suppress the generation of polarized stray light in the PBS.

[0042] Therefore, the present application has developed a new architecture of a high-contrast star simulator to solve the above problems. Summary of the invention

[0043] The object of the present invention is to provide a novel architecture of a high-contrast star simulator capable of suppressing dark-state light leakage and polarized stray light.

[0044] In order to achieve the above object, the present invention provides the following technical solutions:

[0045] A novel architecture of a high-contrast star simulator is characterized in that the architecture includes an exit pupil external collimating optical system, a depolarizing optical engine, and a computer control and data processing system.

[0046] Specifically, the exit pupil external collimating optical system includes a distortion-free eyepiece.

[0047] Specifically, the lens and the lens barrel of the distortion-free eyepiece are plated with an anti-reflection film and sprayed with matte paint.

[0048] Specifically, the depolarization optical engine includes three parts: an illumination optical system, two LCOS, two 1 / 4 wave plates and their splicing structure, and a depolarization beam splitter (NPBS). The two LCOS and their splicing structure are composed of LCOS, a pressing block, an LCOS groove, an adjustment ring and a focusing tube. The LCOS and the 1 / 4 wave plate are fixed together by using the pressing block and the LCOS groove; the illumination optical system mainly includes a light source, a compound parabolic concentrator (CPC), a relay optical system and a compound eye lens.

[0049] Specifically, the NPBS is provided with a 0° polarizer and a 90° polarizer at the light inlet and light outlet, respectively.

[0050] Specifically, the LCOS adopts an LCOS splicing structure to perform optical splicing, and the main steps of LCOS optical splicing can be divided into vertical axis movement of the adjustment ring and axial alignment of the focusing tube.

[0051] Specifically, the computer control and data processing system includes a star map display module; the star map display module is composed of a star point position simulation error partition correction module for star traversal, coordinate transformation, sub-pixel grayscale reconstruction, and a star map output module.

[0052] Specifically, the illumination optical system of the present application adopts the design of Kohler illumination. The beneficial effects of the present invention are:

[0053] In summary, the present invention sets two 1 / 4 wave plates at the front end of LCOS in the optical engine to suppress the dark state light leakage of LCOS, and sets a depolarization optical engine to reduce the polarization stray light power from 2.5×10 -4 W decreased to 4.62×10 -5W, decreased by 5.41 times. The experimental results show that the contrast of the high-contrast star simulator studied in this application is improved from 16.46:1 to 93.41:1 compared with the existing star simulator. It can be seen that the depolarization optical engine can effectively suppress the generation of polarized stray light. Improve the contrast of the star map.

[0054] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 A diagram showing the relationship between the components of a high contrast star simulator according to an embodiment of the present invention;

[0056] Figure 2 This is a general architecture diagram of a high contrast star simulator shown in one embodiment of the present invention;

[0057] Figure 3 This is a working principle diagram of an exit pupil external collimating optical system shown in an embodiment of the present invention;

[0058] Figure 4 This is a schematic diagram of an optical splicing principle shown in an embodiment of the present invention;

[0059] Figure 5 A block diagram of the main components of an illumination optical system shown in one embodiment of the present invention;

[0060] Figure 6 A schematic diagram of Kohler illumination according to an embodiment of the present invention;

[0061] Figure 7 The depolarization optical engine theoretical model PST shown in one embodiment of the present invention;

[0062] Figure 8 A graph showing a change in polarized stray light power with incident angle according to an embodiment of the present invention;

[0063] Fig. 9 A graph showing the variation of PST of a conventional optical engine with incident angle according to an embodiment of the present invention;

[0064] Fig.10 A sampling point contrast test diagram shown in an embodiment of the present invention;

[0065] Fig.11 This is a real-shot image effect diagram of a high-contrast star simulator shown in an embodiment of the present invention;

[0066] Fig.12 This is a real-shot image effect diagram of an existing star simulator shown in an embodiment of the present invention; DETAILED DESCRIPTION

[0067] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without creative work belong to the scope of protection of the present invention. In the description of the present invention, it should be noted that the orientation or position relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be the internal connection of two elements. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood in specific situations. In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0068] See also Figure 1~Figure 2 The present invention provides a novel architecture of a high-contrast star simulator, including an exit pupil external collimating optical system, a depolarizing optical engine, and a computer control and data processing system.

[0069] Specifically, the exit pupil external collimating optical system includes a distortion-free eyepiece.

[0070] For details, see Figure 3 The working principle of the exit pupil external collimation optical system is as follows: two LCOS are located at the focal plane of the optical system. After the incident light is modulated by the LCOS, it is transmitted to the exit pupil external collimation optical system to realize the simulation of the approximately infinite star point.

[0071] Specifically, the depolarization optical engine consists of three parts: the illumination optical system, two LCOS and their splicing structure, and the depolarization beam splitter (NPBS). The two LCOS, two 1 / 4 wave plates and their splicing structure are composed of LCOS, a pressure block, an LCOS groove, an adjustment ring and a focusing tube. The LCOS is fixed by using the pressure block and the LCOS groove. The adjustment ring can make the LCOS move along the axis of the focusing tube and rotate along the axis, thereby realizing the LCOS alignment and focusing function. Please refer to Figure 5 The illumination optical system mainly includes light source, compound parabolic concentrator (CPC), relay optical system and compound eye lens.

[0072] Specifically, since LCOS requires polarized light illumination, a 0° polarizer and a 90° polarizer need to be added to the light inlet and the light outlet when using NPBS. The 0° polarizer absorbs polarized light that is opposite to its optical axis, and polarizes the incident light into linear polarized light with a single vibration direction. NPBS splits the incident linear polarized light according to a certain ratio, and maintains the original polarization state of the incident light, thereby suppressing the occurrence of polarization stray light doping. The 90° polarizer filters out polarized light that is opposite to the optical axis of the polarizer, and only passes polarized light that is parallel to the optical axis. In high-contrast star simulators, this is reflected in the reduction of stray light that is opposite to the vibration direction of the simulated star point.

[0073] Specifically, two 1 / 4 wave plates are used to suppress LCOS dark state light leakage, and an LCOS splicing structure is used to optically splice the LCOS to increase the resolution.

[0074] Specifically, the main steps of LCOS optical splicing can be divided into vertical axis movement of the adjustment ring and axial alignment of the focusing tube. The main idea of ​​splicing is to use the beam combining characteristics of the beam splitter prism, take a column of pixels at the edge of the LCOS1 image and a row of pixels in the center as the splicing reference, and make a column of pixels at the edge of the LCOS2 image and a row of center pixels overlap by rotating and translating the focusing tube at a small angle until the center pixels of LCOS1 and LCOS2 are in a straight line.

[0075] See also Figure 4 The splicing principle of the two LCOS mainly uses NPBS to form a pair of conjugate planes with equal optical paths. The two LCOS are installed on the equivalent focal plane positions of the upper surface and the right surface of the prism respectively. The outgoing light of the light source is incident on the NPBS after passing through the 0° polarizer and is divided into two light paths 2 and 3. The dotted line 3 is the light path of LCOS2, and the solid line 2 is the light path of LCOS1. After modulation by the two LCOS, the outgoing light 2 and 3 from the upper end of LCOS1 and the left end of LCOS2 coincide, realizing the splicing of the two LOCS.

[0076] Specifically, the computer control and data processing system includes a star map display module, which is composed of a star traversal, coordinate transformation, a sub-pixel grayscale reconstruction star point position simulation error partition correction module and a star map output module. The star traversal module completes the query of the star catalog database and sends the information to the coordinate transformation module; the coordinate transformation module processes the star point position information of the star traversal module by using the star map display algorithm; the sub-pixel grayscale reconstruction star point position error partition correction module realizes the star point position simulation error correction, and displays the star point in real time through the star map output module.

[0077] See also Figure 6 The illumination optical system of the present application adopts the design of Kohler illumination. The light emitted by the light source first passes through a front lens L1 and is imaged on the variable aperture J2 in front of the condenser. The condenser L2 then forms the image of the light source on the entrance pupil plane of the objective lens. Therefore, the image of the light source is located at the position of J2, avoiding interference from the image of the light source. By adjusting the aperture J2, the illumination system can be matched with different numerical apertures.

[0078] The main reason why the existing PBS generates stray light is that the polarization state of the output light of the PBS is unstable, which causes part of the imaging polarized light to be converted into polarized stray light. Therefore, the Jones matrix of the polarizing film is established to analyze the factors that affect the polarization state of the output light of the polarizing film. The Jones matrix J of the film can be expressed as

[0079] ; (18)

[0080] Where φ (0≤φ≤2π) is the incident light aperture angle, T p With T s is the transmittance of P and S light in the transmitted light field, Δ=(Δs+Δp) / 2 is the average phase, and δ=Δs-Δp is the phase difference.

[0081] Assuming that the vibration direction of the incident light is along the x-axis, the polarization state of the outgoing light after passing through the film can be expressed as

[0082] ; (19)

[0083] In the formula, all variables are related to the incident angle. By comparing the polarization state of the incident light, it can be seen that the polarization state of the outgoing light changes significantly with the change of the incident angle φ. It can be seen that oblique incidence will cause changes in the film phase difference and transmittance attenuation, thereby generating imaging stray light.

[0084] The following will analyze the polarization characteristics of the outgoing light based on the two factors of phase difference and transmittance attenuation. If only the phase difference is considered, then T = Ts = Tp, and formula (19) can be simplified to

[0085] ; (20)

[0086] From the above formula, we can see that the transmittance T will not change the polarization state of the outgoing light, but the phase difference and the incident angle φ in the matrix will change the polarization state of the outgoing light, and φ is a system parameter that cannot be changed. When δ is closer to 0, the polarization state of the outgoing light is closer to the polarization state of the incident light, which will effectively suppress the change in polarization state caused by oblique incidence.

[0087] If δ=0, only the effect of transmittance on the polarization state of the outgoing light is considered, then formula (19) is simplified to

[0088] ; (twenty one)

[0089] It can be seen from the above formula that when the difference between Tp and Ts is larger, the transmittance attenuation (Tp-Ts) / (Tp+Ts) is larger, and the polarization state of the outgoing light will inevitably change dramatically. For obliquely incident light, if Tp=Ts, the polarization state of the outgoing light will be closer to the polarization state of the incident light.

[0090] Therefore, when correcting the stray light of the optical engine caused by oblique incidence, the first condition is to satisfy the conditions of any incidence, δ = 0 and (Tp-Ts) / (Tp+Ts) = 0.

[0091] Since the film needs to satisfy δ=0, the depolarization theory is used to design the PBS in the optical engine. At this time, the polarization state of the outgoing light remains constant and the stray light is completely suppressed.

[0092] Under actual conditions, since the change of the incident angle will inevitably change the corrected admittance and thus change the polarization state of the outgoing light, it is necessary to derive the NPBS optimization stop condition based on this ideal goal to achieve the optimization of NPBS under actual conditions.

[0093] The calculation of the magnitude detection capability mainly comes from SNR. By treating stray light as a kind of noise and substituting the PST parameters of the star simulator into the signal-to-noise ratio calculation process, the association between the star simulator PST and the detector SNR can be established.

[0094] When the detector receives the light beam, the number of electrons N generated o It can be expressed as

[0095] ; (twenty two)

[0096] In the formula, h is Planck's constant, c is the speed of light in a vacuum, the entrance pupil diameter of the optical system is D, and the irradiance is E t , the detector exposure time is t0, the optical system transmittance is τ0, λ is the center wavelength, and the spectral efficiency of the detector is η1.

[0097] The magnitude m can be used to represent the target illumination E0=2.51 m×2.65×10 -6 lx. At this time, the number of electrons generated by the target on the detector is N e The relationship with the magnitude m can be expressed as

[0098] ; (twenty three)

[0099] The optical noise of the system is related to the number of electrons n generated by the detector es It can be expressed as

[0100] ; (twenty four)

[0101] Where, dB0=0.25×π×D 2 ×τ×I(θ i ´,Φ i )×PST(θ i ´,Φ i ), dB0 is the background stray light intensity, I(θ i ´,Φ i ) is the incident light intensity, θ i ´ is the incident azimuth, Φ i The incident spatial angle, PST(θ i ´,Φ i ) is the point source transmittance.

[0102] System noise equivalent electron number N n for

[0103] ; (25)

[0104] Where n b represents the detector dark current noise.

[0105] Therefore, the signal-to-noise ratio (SNR) of the star simulator under different azimuth and spatial angle conditions can be expressed as:

[0106] ; (26)

[0107] Taking the 6th magnitude star as an example, when SNR=6.5, the star sensor can identify the 6th magnitude star, and the corresponding star simulator optical engine PST should be 9.41×10 -5 .

[0108] The existing PBS film layer uses ZrO2 and MgF2 as high and low refractive index materials, and the film layer expression is (HL) ^10 (HL) ^10 (L) ^15 .

[0109] The existing PBS film layer is used as the initial structure, δ=0 and (Tp-Ts) / (Tp+Ts)=0 are used as the optimization target conditions, and the PST of the simulated 6th magnitude star is used as the stop condition. At the same time, in order to match the collimating optical system, the last glass plate material ZF52 of the collimating optical system is used as the prism substrate, and the optical thickness of each film layer is optimized, and its critical incident angle is determined. If the PST within the critical incident angle is less than the PST of the simulated 6th magnitude star, the optimization stops. The depolarization spectroscopic film system after the PBS optimization design is shown in Table 1.

[0110]

[0111] Determination of critical incident angle of NPBS and comparison of polarized stray light power Figure 7~Figure 8 As shown in the figure, the light source is idealized as a uniform beam that meets the NPBS critical incident angle, a depolarization optical engine theoretical model is established, and the corresponding PST size and polarization stray light power are calculated when the incident angle changes from 0° to 20°. -5 When the NPBS critical incident angle is 10.2°, the maximum phase difference is 0.13° and the maximum transmittance attenuation is 3%, the corresponding polarization stray light power is 4.62×10 -5 W, when the incident angle is greater than the critical incident angle, the polarized stray light power of the optical engine will continue to increase, which will cause the optical engine's stray light suppression ability to decrease. Therefore, the output light divergence angle of the illumination optical system should match the NPBS critical incident angle. The calculation shows that the PST of the existing optical engine changes with the incident angle as follows: Fig. 9 shown.

[0112] Depend on Fig. 9 It can be seen that when the incident angle is less than 3.2°, the PST changes more slowly, and the corresponding PST is 5.01×10 -4 When the incident angle is greater than 3.2°, PST has a clear upward trend and the stray light increases significantly. Therefore, the maximum critical incident angle of the existing optical engine is 3.2°, corresponding to the polarized stray light power of 2.5×10 -4 ,The parameters of the existing optical engine stray light suppression capability are summarized in Table 2.

[0113]

[0114] The comparison results of polarization stray light power of the existing optical engine and the depolarization optical engine under ideal light source conditions are shown in Table 3.

[0115]

[0116] The polarization stray light power of the existing optical engine is compared with that of the depolarization optical engine under ideal light source conditions. It can be seen from Table 3 that after the depolarization optical engine is used, the polarization stray light power is reduced from 2.5×10 -4 W decreased to 4.62×10 -5 W, decreased by 5.41 times, which shows that the depolarization optical engine can effectively suppress stray light.

[0117] The contrast test experimental device built mainly consists of a high-contrast star simulator, a computer control and data processing system, a six-dimensional adjustment stage and an irradiator. Among them, the high-contrast star simulator consists of a collimating optical system, a depolarizing optical engine, a computer control and data processing system.

[0118] The star simulator contrast test method is as follows:

[0119] (1) Fix the radiometer test probe on the six-dimensional stage and adjust the six-dimensional stage until the photosensitive surface of the probe coincides with the light outlet of the star simulator.

[0120] (2) Select 9 contrast test sampling points, including 0 field of view, 0.707 field of view and full field of view. The sampling point size is 50 pixel × 50 pixel, including 1 sampling point of 0 field of view (serial number 1), 4 sampling points of 0.707 field of view (serial numbers 2 to 5) and 4 sampling points of full field of view (serial numbers 6 to 9). Fig.10 As shown, each sampling point is turned on and off in sequence according to the figure, and the irradiance of each sampling point after lighting and extinguishing is measured respectively. The contrast C of each field of view is calculated using formula (1-10), and the minimum value is taken as the contrast of the star simulator.

[0121] ; (27)

[0122] Where E is the irradiance measured when each sampling point is on, and E' is the irradiance measured when each sampling point is off.

[0123] (3) Using the above method, first test the contrast of the high-contrast star simulator studied in this application; then replace the high-contrast star simulator with an existing star simulator, and use the above method to measure the contrast of the existing star simulator again.

[0124] The contrast test results of the high-contrast star simulator studied in this application and the existing star simulator are shown in Table 4.

[0125]

[0126] From the results in Table 4, it can be seen that the contrast ratios of the high-contrast star simulator studied in this application are 102.45:1, 99.09:1 and 93.41:1 at 0 field of view, 0.707 field of view and full field of view, respectively, and the minimum contrast ratio is 93.41:1; the contrast ratios of the existing star simulators are 25.01:1, 19.39:1 and 16.46:1 at 0 field of view, 0.707 field of view and full field of view, respectively, and the minimum contrast ratio is 16.46:1. Compared with the existing star simulators, the contrast ratio of the high-contrast star simulator studied in this application is increased from 16.46:1 to 93.41:1, which is 5.67 times higher.

[0127] In order to further verify the effectiveness of the high-contrast star simulator studied by this paper, a CCD camera was used to take real photos of the same cross image output by the high-contrast star simulator and the existing star simulator. The real-shot image effects of the two star simulators are as follows: Figure 11~Figure 12 shown.

[0128] Depend on Figure 11~Figure 12 It can be seen that the contrast of the high-contrast star simulator studied in this application is significantly better than that of existing star simulators.

[0129] In summary, the present invention sets two 1 / 4 wave plates at the front end of LCOS in the optical engine to suppress the dark state light leakage of LCOS, and sets a depolarization optical engine to reduce the polarization stray light power from 2.5×10 -4 W decreased to 4.62×10 -5 W, decreased by 5.41 times. The experimental results show that the contrast of the high-contrast star simulator studied in this application is improved from 16.46:1 to 93.41:1 compared with the existing star simulator. It can be seen that the depolarization optical engine can effectively suppress the generation of stray light. Improve the contrast of the star map.

[0130] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0131] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A novel architecture of a high contrast star simulator, characterized in that: The architecture includes an exit pupil external collimating optical system, a depolarizing optical engine, and a computer control and data processing system.

2. A novel high contrast star simulator architecture as claimed in claim 1, characterized in that: The exit pupil external collimating optical system includes a distortion-free eyepiece.

3. A novel high contrast star simulator architecture as claimed in claim 1, characterized in that: The depolarizing optical engine includes an illumination optical system, two LCOS, two 1 / 4 wave plates and their splicing structure, and a depolarizing beam splitter (NPBS). The two LCOS, two 1 / 4 wave plates and their splicing structure are composed of LCOS, a pressing block, an LCOS groove, an adjustment ring and a focusing tube. The LCOS and the 1 / 4 wave plate are fixed together by using the pressing block and the LCOS groove; the illumination optical system mainly includes a light source, a compound parabolic concentrator (CPC), a relay optical system and a compound eye lens.

4. A novel high contrast star simulator architecture as claimed in claim 1, characterized in that: The NPBS is provided with a 0° polarizer and a 90° polarizer at the light inlet and light outlet, respectively.

5. A novel high contrast star simulator architecture as claimed in claim 1, characterized in that: The LCOS adopts an LCOS splicing structure to perform optical splicing; the main steps of the LCOS optical splicing can be divided into vertical axis movement of the adjustment ring and axial alignment of the focusing tube.

6. A novel high contrast star simulator architecture as claimed in claim 1, characterized in that: The computer control and data processing system comprises a star map display module; the star map display module is composed of a star point position simulation error partition correction module for star traversal, coordinate transformation, sub-pixel grayscale reconstruction, and a star map output module.

7. A novel high contrast star simulator architecture as claimed in claim 1, characterized in that: The illumination optical system adopts the design method of Kohler illumination.

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