A large-aperture infrared dual-band target detection optical system

Abstract

This invention discloses a large-aperture infrared dual-band target detection optical system, comprising: a scanning mirror, an aperture stop, a first mirror, a second mirror, a first folding mirror, a third mirror, a fourth mirror, a fifth mirror, a second folding mirror, a third folding mirror, a mid-wave infrared image plane, and a long-wave infrared image plane. Mid-wave and long-wave infrared light emitted by the target sequentially passes through the scanning mirror, aperture stop, first mirror, second mirror, first folding mirror, third mirror, fourth mirror, and fifth mirror. The mid-wave infrared light converges onto the mid-wave infrared image plane after passing through the second folding mirror, and the long-wave infrared light converges onto the long-wave infrared image plane after passing through the third folding mirror. This invention can simultaneously achieve mid-wave and long-wave infrared dual-band imaging, and has advantages such as large aperture, large scanning angle, compact size, good imaging quality, and high image-side telecentricity. It can be used in fields such as high-resolution infrared imaging in space optical remote sensors and high-sensitivity target detection.

Description

Technical Field

[0001] This invention belongs to the field of space optical remote sensing imaging technology, and particularly relates to a large-aperture infrared dual-spectral target detection optical system. Background Technology

[0002] The infrared spectrum possesses all-weather remote sensing capabilities and has broad application prospects in fields such as environmental protection, fire monitoring, and camouflaged target detection. Currently, infrared optical systems used for space remote sensing suffer from several major problems that severely limit their role in the field: First, existing infrared optical systems have small apertures, failing to achieve high spatial resolution and high temperature sensitivity imaging; second, existing infrared optical systems have small field of view and narrow imaging swaths, failing to achieve high temporal resolution imaging; third, existing infrared optical systems suffer from large imaging distortion, failing to achieve high-precision target detection; and fourth, existing infrared optical systems have poor image-side telecentricity and low image plane illumination at the edges of the field of view, failing to achieve consistent imaging over a large field of view. Summary of the Invention

[0003] The technical problem solved by this invention is to overcome the shortcomings of the prior art and provide a large-aperture infrared dual-band target detection optical system with advantages such as large aperture, large scanning angle, compact size, good imaging quality, and high image telecentricity. It can be used in fields such as high-resolution infrared imaging of space optical remote sensors and high-sensitivity target detection.

[0004] The objective of this invention is achieved through the following technical solution: a large-aperture infrared dual-band target detection optical system, comprising: a scanning mirror, an aperture stop, a first mirror, a second mirror, a first folding mirror, a third mirror, a fourth mirror, a fifth mirror, a second folding mirror, and a third folding mirror; mid-wave and long-wave infrared light emitted by the target passes sequentially through the scanning mirror, the aperture stop, the first mirror, the second mirror, the first folding mirror, the third mirror, the fourth mirror, and the fifth mirror; the mid-wave infrared light is converged onto the mid-wave infrared image plane after passing through the second folding mirror, and the long-wave infrared light is converged onto the long-wave infrared image plane after passing through the third folding mirror.

[0005] The scanning mirror is placed at a 45° angle around the X-axis, and the distance between the center of the scanning mirror and the center of the aperture stop is 350 mm; the scanning angle range of the scanning mirror around the X-axis is 45°±15°; the aperture stop is placed perpendicular to the Z-axis and has a diameter of 376 mm; the X-axis is perpendicular to the paper plane; the Z-axis is the incident direction of light, i.e., from the scanning mirror to the image plane.

[0006] The first, second, third, fourth, and fifth reflecting mirrors are all off-axis reflecting mirrors; among them, the first, third, and fifth reflecting mirrors are concave reflecting mirrors; and the second and fourth reflecting mirrors are convex reflecting mirrors.

[0007] The off-axis distance of the first reflector is 382.1 mm, the off-axis distance of the second reflector is 135 mm, the off-axis distance of the third reflector is 138.5 mm, the off-axis distance of the fourth reflector is 61.2 mm, and the off-axis distance of the fifth reflector is 120.9 mm.

[0008] The first, second, and third folding mirrors are all plane mirrors, wherein:

[0009] The first folding mirror refracts the mid-wave infrared and long-wave infrared light onto the third reflecting mirror, the second folding mirror refracts the mid-wave infrared light onto the mid-wave infrared image plane, and the third folding mirror refracts the long-wave infrared light onto the long-wave infrared image plane.

[0010] The third and fifth reflecting mirrors are sixth-order XY polynomial freeform surfaces.

[0011] The operating spectral range of the large-aperture infrared dual-band target detection optical system is mid-wave infrared (3μm~5μm) and long-wave infrared (8μm~12μm). The field of view in the X direction, i.e., the direction perpendicular to the paper, is 7.32°, and the field of view in the Y direction, i.e., the direction parallel to the paper, is 1°.

[0012] The scanning mirror, the first mirror, the second mirror, the first folding mirror, the third mirror, the fourth mirror, and the fifth mirror are all coated with anti-reflection films, and the reflectivity is greater than 0.97 in the 3μm~5μm and 8μm~12μm spectral ranges.

[0013] The second folding mirror is coated with an anti-reflection film, and its reflectivity is greater than 0.98 in the 3μm to 5μm spectral range; the third folding mirror is coated with an anti-reflection film, and its reflectivity is greater than 0.98 in the 8μm to 12μm spectral range.

[0014] The field of view in the Y direction for the mid-wave infrared (3μm~5μm) band is -0.5°, and the field of view in the Y direction for the long-wave infrared (8μm~12μm) band is 0.5°.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] (1) The system of the present invention has the ability to simultaneously image in two infrared bands. The working bands include mid-wave infrared (3μm~5μm) and long-wave infrared (8μm~12μm), which has the advantage of all-weather remote sensing detection and can be used in fields such as environmental protection, fire monitoring, and detection of camouflaged targets.

[0017] (2) The system of the present invention has a large field of view imaging capability. The field of view angle in the X direction is 7.32° and the field of view angle in the Y direction is 1°. The optical system has a scanning mirror with a scanning angle range of 45°±15°, which further increases the imaging field of view and helps to solve the problem of the small field of view of existing detection.

[0018] (3) The system of the present invention has low distortion imaging capability, with a maximum relative distortion of less than 0.44% within a field of view of 7.32°×1°, which is beneficial to improving the detection accuracy of infrared spatial remote sensing.

[0019] (4) The system of the present invention has the feature of high image-side telecentricity. The incident angle of the principal ray from the edge field of view to the image plane is less than 0.35°, thereby increasing the image plane illumination of the edge field of view to 100%, which is beneficial to improving the imaging consistency in a large field of view.

[0020] (5) The off-axis distance of the first reflecting mirror of the present invention is 382.1 mm, the off-axis distance of the second reflecting mirror is 135 mm, the off-axis distance of the third reflecting mirror is 138.5 mm, the off-axis distance of the fourth reflecting mirror is 61.2 mm, and the off-axis distance of the fifth reflecting mirror is 120.9 mm, which can achieve the high imaging quality requirements of the optical system.

[0021] (6) The scanning mirror, first mirror, second mirror, first folding mirror, third mirror, fourth mirror, and fifth mirror of the system of the present invention, after being coated with anti-reflective films, have a reflectivity greater than 0.97 in the 3μm-5μm and 8μm-12μm spectral ranges; the second folding mirror, after being coated with an anti-reflective film, has a reflectivity greater than 0.98 in the 3μm-5μm spectral range; and the third folding mirror, after being coated with an anti-reflective film, has a reflectivity greater than 0.98 in the 8μm-12μm spectral range. This system exhibits high energy efficiency, which is beneficial for achieving a high signal-to-noise ratio and meeting various application requirements.

[0022] (7) The field of view of the mid-wave infrared (3μm~5μm) spectral band of the system of the present invention is -0.5° in the Y direction, and the field of view of the long-wave infrared (8μm~12μm) spectral band is 0.5° in the Y direction. The image plane of the two spectral bands is 20mm apart, ensuring that there is no interference between the image planes of the two spectral bands. Attached Figure Description

[0023] Figure 1 This is a diagram of a large-aperture infrared dual-band target detection optical system according to the present invention; wherein, Figure 1 (a) is a diagram of the optical system in the non-scanning state of the scanning mirror; Figure 1 (b) is a diagram of the optical system under the scanning reflector scanning +15° state; Figure 1 (c) is a diagram of the optical system when the scanning mirror is scanning at -15°.

[0024] Figure 2 The diagram shows the modulation transfer function curves of the optical system of the present invention in various fields of view. Figure 2 (a) is a graph of the modulation transfer function of the optical system in each field of view in the mid-infrared band; Figure 2 (b) is a graph of the modulation transfer function of the optical system in each field of view in the long-wave infrared band;

[0025] Figure 3 This is a grid distortion diagram of the optical system of the present invention;

[0026] Figure 4 This is the image plane illuminance curve of the optical system of the present invention;

[0027] Figure 5 This is the image-side telecentricity curve of the optical system of the present invention. Detailed Implementation

[0028] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0029] Figure 1 This is a diagram of a large-aperture infrared dual-spectral target detection optical system according to the present invention.

[0030] like Figure 1 As shown, the working spectral range of the optical system is mid-wave infrared (3μm~5μm) and long-wave infrared (8μm~12μm), with a field of view of 7.32° in the X direction and 1° in the Y direction.

[0031] The system includes a scanning mirror SM, an aperture stop STOP, a first mirror M1, a second mirror M2, a first folding mirror FM1, a third mirror M3, a fourth mirror M4, a fifth mirror M5, a second folding mirror FM2, a third folding mirror FM3, a mid-wave infrared (MWIR) image plane, and a long-wave infrared (LWIR) image plane; such as Figure 1 As shown in (a), the scanning mirror SM is tilted at 45° around the X-axis in the non-scanning state, and the distance between the center of the scanning mirror SM and the center of the aperture stop STOP is 350 mm; the scanning angle range of the scanning mirror SM around the X-axis is 45°±15°, as shown in (a). Figure 1As shown in (b), when the scanning mirror SM scans +15°, the scanning mirror SM is tilted 30° around the X-axis; as Figure 1 As shown in (c), when the scanning mirror SM scans -15°, the scanning mirror SM is tilted 60° around the X-axis.

[0032] The mid-wave and long-wave infrared rays radiated by the target pass sequentially through the scanning mirror SM, the aperture stop STOP, the first mirror M1, the second mirror M2, the first folding mirror FM1, the third mirror M3, the fourth mirror M4, and the fifth mirror M5. The mid-wave infrared rays converge onto the mid-wave infrared image plane MWIR Image after passing through the second folding mirror FM2, and the long-wave infrared rays converge onto the long-wave infrared image plane LWIR Image after passing through the third folding mirror.

[0033] The aperture stop of the optical system is placed perpendicular to the Z-axis and has a diameter of 376mm; the first mirror M1, the second mirror M2, the third mirror M3, the fourth mirror M4, and the fifth mirror M5 are all off-axis mirrors; the first mirror M1, the third mirror M3, and the fifth mirror M5 are concave mirrors; the second mirror M2 and the fourth mirror M4 are convex mirrors.

[0034] The surfaces of the scanning mirror SM, the first mirror M1, the second mirror M2, the first folding mirror FM1, the third mirror M3, the fourth mirror M4, and the fifth mirror M5 are all coated with anti-reflection films, and the reflectivity is greater than 0.97 in the spectral ranges of 3μm to 5μm and 8μm to 12μm.

[0035] The second folding mirror FM2 has an anti-reflection coating on its surface, with a reflectance greater than 0.98 in the 3μm to 5μm spectral range; the third folding mirror FM3 has an anti-reflection coating on its surface, with a reflectance greater than 0.98 in the 8μm to 12μm spectral range.

[0036] The off-axis distance of the first reflector M1 is 382.1 mm, the off-axis distance of the second reflector M2 is 135 mm, the off-axis distance of the third reflector M3 is 138.5 mm, the off-axis distance of the fourth reflector M4 is 61.2 mm, and the off-axis distance of the fifth reflector M5 is 120.9 mm.

[0037] The third reflecting mirror M3 and the fifth reflecting mirror M5 are sixth-order XY polynomial freeform surfaces without rotational symmetry; the surface shape expression is as follows, and they are machined using a single-point diamond lathe and surface shape is detected using a high-precision profilometer.

[0038]

[0039] Where z(x,y) on the left side of the equation represents the freeform surface elevation at different coordinate positions; the right side of the equation represents the specific calculation expression for the freeform surface elevation; x is the coordinate of the freeform surface along the X-axis; y is the coordinate of the freeform surface along the Y-axis; c is the reciprocal of the radius of curvature at the vertex of the freeform surface; k is the quadratic surface coefficient of the freeform surface; C1, C2…C 27 Let x, y, x' be the coefficients of the XY polynomial. 2 、xy…y 6 For the expansion of the XY polynomial.

[0040] like Figure 2 As shown, the modulation transfer function of each field of view of the optical system is close to the diffraction limit, resulting in good imaging quality.

[0041] like Figure 3 As shown, the maximum absolute value of the relative distortion of the optical system is less than 0.44%.

[0042] like Figure 4 As shown, the image plane illuminance of the optical system is 100% within the field of view.

[0043] like Figure 5 As shown, the angle at which the principal ray of the edge field of view of the optical system is incident on the image plane is less than 0.35°, and it has good image-side telecentrism.

[0044] Table 1 Parameters of Freeform Surface

[0045]

[0046]

[0047] This invention's system features simultaneous dual-band infrared imaging capability, with working bands including mid-wave infrared (3μm~5μm) and long-wave infrared (8μm~12μm), providing all-weather remote sensing advantages and applicable to fields such as environmental protection, fire monitoring, and camouflaged target detection. It also boasts a large field-of-view imaging capability, with a field of view of 7.32° in the X direction and 1° in the Y direction. The optical system includes a scanning mirror with a scanning angle range of 45°±15°, further increasing the imaging field of view and addressing the problem of limited field of view in existing systems. Furthermore, it exhibits low distortion imaging capability, with a maximum relative distortion of less than 0.44% within a 7.32°×1° field of view, improving the detection accuracy of infrared spatial remote sensing. Finally, it features high image-side telecentrism, with the incident angle of the principal ray at the edge of the field of view to the image plane less than 0.35°, thereby increasing the image plane illumination at the edge of the field of view to 100%, which enhances imaging consistency across a large field of view.

[0048] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A large-aperture infrared dual-band target detection optical system, characterized in that... include: The system consists of a scanning mirror, an aperture stop, a first mirror, a second mirror, a first folding mirror, a third mirror, a fourth mirror, a fifth mirror, a second folding mirror, and a third folding mirror. Mid-wave and long-wave infrared rays radiated by the target pass sequentially through these mirrors. The mid-wave infrared rays converge onto the mid-wave infrared image plane after passing through the second folding mirror, and the long-wave infrared rays converge onto the long-wave infrared image plane after passing through the third folding mirror. The scanning mirror is placed at a 45° angle around the X-axis, and the distance between the center of the scanning mirror and the center of the aperture stop is 350 mm; the scanning angle range of the scanning mirror around the X-axis is 45°±15°; the aperture stop is placed perpendicular to the Z-axis and has a diameter of 376 mm; the X-axis is perpendicular to the paper plane; the Z-axis is the direction of light incident, i.e., from the scanning mirror to the image plane; The working spectral range of the large-aperture infrared dual-band target detection optical system is mid-wave infrared (3μm~5μm) and long-wave infrared (8μm~12μm). The field of view in the X direction, i.e., the direction perpendicular to the paper, is 7.32°, and the field of view in the Y direction, i.e., the direction parallel to the paper, is 1°. The field of view in the Y direction for the mid-wave infrared (3μm~5μm) band is -0.5°, and the field of view in the Y direction for the long-wave infrared (8μm~12μm) band is 0.5°.

2. The large-aperture infrared dual-band target detection optical system according to claim 1, characterized in that: The first, second, third, fourth, and fifth reflecting mirrors are all off-axis reflecting mirrors; among them, the first, third, and fifth reflecting mirrors are concave reflecting mirrors; and the second and fourth reflecting mirrors are convex reflecting mirrors.

3. The large-aperture infrared dual-band target detection optical system according to claim 2, characterized in that: The off-axis distance of the first reflector is 382.1 mm, the off-axis distance of the second reflector is 135 mm, the off-axis distance of the third reflector is 138.5 mm, the off-axis distance of the fourth reflector is 61.2 mm, and the off-axis distance of the fifth reflector is 120.9 mm.

4. The large-aperture infrared dual-band target detection optical system according to claim 1, characterized in that: The first, second, and third folding mirrors are all plane mirrors, wherein: The first folding mirror refracts the mid-wave infrared and long-wave infrared light onto the third reflecting mirror, the second folding mirror refracts the mid-wave infrared light onto the mid-wave infrared image plane, and the third folding mirror refracts the long-wave infrared light onto the long-wave infrared image plane.

5. The large-aperture infrared dual-band target detection optical system according to claim 2, characterized in that: The third and fifth reflecting mirrors are sixth-order XY polynomial freeform surfaces.

6. The large-aperture infrared dual-band target detection optical system according to claim 1, characterized in that: The scanning mirror, the first mirror, the second mirror, the first folding mirror, the third mirror, the fourth mirror, and the fifth mirror are all coated with anti-reflection films, and the reflectivity is greater than 0.97 in the 3μm~5μm and 8μm~12μm spectral ranges.

7. The large-aperture infrared dual-band target detection optical system according to claim 1, characterized in that: The second folding mirror is coated with an anti-reflection film, and its reflectivity is greater than 0.98 in the 3μm to 5μm spectral range; the third folding mirror is coated with an anti-reflection film, and its reflectivity is greater than 0.98 in the 8μm to 12μm spectral range.

Images