Multiband distance simulation zoom system

Abstract

The invention relates to a multiband distance simulation zoom system, which relates to the field of measurement systems, and comprises a main optical system and a distance zoom simulation system, and is characterized in that an object space telecentric light path is adopted in the main optical system to enable parallel incident object space light to reach an image plane for imaging; a mechanical compensation zooming system is arranged in the distance zooming simulation system so as to carry out distance simulation on a fixed distance scaling simulation measured object and simulate equivalent simulation of the measured object from far to near and from a point source to a surface source. The device has the advantages that optical characteristics of the measured object in the movement process from far to near can be obtained in a laboratory; and quantitative simulation of the multi-band dynamic imaging process of the measured object is realized.

Description

Technical Field

[0001] The invention relates to the technical field of measurement systems, and in particular to a multi-band distance simulation zoom system. Background Art

[0002] Optical measurement is a non-contact measurement technology that uses some basic properties of light, such as reflection, interference, and scattering, to perform relevant precise measurements. The main principle is to use the physical properties of light to detect the measured object, and different measurement methods utilize different properties.

[0003] Optical measurement is widely used in various fields such as industry, medicine, environmental science, physics, agriculture and military, and has achieved many major results, but there are still some challenges, such as how to improve measurement accuracy, how to process large amounts of data, and how to achieve fast measurement.

[0004] Therefore, in view of the above shortcomings, it is necessary to provide a multi-band distance simulation zoom system. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] The technical problem to be solved by the present invention is to solve the problem of how to realize quantitative simulation of the multi-band dynamic imaging process of the measured object.

[0007] (II) Technical solution

[0008] In order to solve the above technical problems, the present invention provides a multi-band distance simulation zoom system, including a main optical system and a distance zoom simulation system. The main optical system adopts an object-side telecentric optical path to allow parallel incident object-side light to reach the image plane for imaging; the distance zoom simulation system has a built-in mechanical compensation zoom system to perform distance simulation on a fixed-distance scaled simulated object to be measured and to simulate the equivalent simulation of the object to be measured from far to near and from point source to surface source.

[0009] As a further illustration of the present invention, preferably, the main optical system includes a primary mirror, a secondary mirror, a third mirror and a fourth mirror, the primary mirror is mounted on the side close to the simulated target, the secondary mirror is located at the reflection end of the primary mirror, the third mirror is located at the reflection end of the secondary mirror, and the fourth mirror is located at the reflection end of the third mirror; the primary mirror and the secondary mirror, the third mirror and the fourth mirror respectively form a 10x zoom 4f system so that the size of the simulated target on the image plane is independent of its distance from the main optical system.

[0010] As a further illustration of the present invention, preferably, the primary mirror is a 2.2m off-axis spherical mirror, the secondary mirror and the third mirror are off-axis hyperbolic mirrors, and the fourth mirror is a parabolic reflector.

[0011] As a further illustration of the present invention, preferably, two folding plane mirrors are provided between the primary mirror and the secondary mirror to fold the optical path and correct the tilt aberration.

[0012] As a further illustration of the present invention, preferably, the off-axis angle of the four mirrors is greater than the off-axis angle of the main mirror so as to deviate the reflected light beam from the main optical path.

[0013] As a further illustration of the present invention, preferably, the mechanical compensation zoom system includes a front fixed group, a magnification group, a compensation group and a rear fixed group, the positions of the front fixed group and the rear fixed group remain unchanged, the magnification group and the compensation group are movable structures, and a filter or aperture is provided in front of the front fixed group.

[0014] As a further illustration of the present invention, preferably, when measuring visible light, the front fixed group adopts a single-single-double structure, wherein the first piece is made of CaF material, and the tail piece adopts a HZLAF and HZK double-cemented lens; the zoom group adopts HZF88 as the positive lens and HFK as the negative lens; the compensation group adopts a telephoto structure.

[0015] As a further illustration of the present invention, preferably, when measuring near-infrared, the front fixed group consists of three single lenses and one cemented lens, the magnification group consists of two single lenses and one cemented lens, the compensation group consists of two single lenses and one cemented lens, and the rear fixed group consists of three single lenses and one cemented lens.

[0016] As a further illustration of the present invention, preferably, when measuring mid-wave infrared, the front fixing group is made of silicon material, the zoom group is made of germanium material with negative optical power, and the compensation group is made of silicon material with a double separation structure.

[0017] As a further illustration of the present invention, preferably, when measuring long-wave infrared, the mechanical compensation zoom system is made of two materials: germanium and zinc selenide.

[0018] (III) Beneficial effects

[0019] The above technical solution of the present invention has the following advantages:

[0020] The present invention provides a novel multi-band distance simulation zoom system, which can obtain the optical characteristics of the measured object during the movement from a long distance to a close distance in a laboratory, and realize the quantitative simulation of the multi-band dynamic imaging process of the measured object. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the overall design structure of the present invention;

[0022] Figure 2 is a modulation transfer function diagram of the main optical system of the present invention;

[0023] Figure 3 is a field curvature / distortion diagram of the main optical system of the present invention;

[0024] Figure 4It is an optical principle diagram of the mechanical positive group compensation zoom system of the present invention;

[0025] Figure 5 is a schematic structural diagram of the visible light zoom system of the present invention;

[0026] Figure 6 is a MTF curve diagram of the visible light zoom system of the present invention;

[0027] Figure 7 It is a schematic diagram of the structure of the near-infrared zoom system of the present invention;

[0028] Figure 8 is a MTF curve diagram of the near-infrared zoom system of the present invention;

[0029] Fig. 9 It is a schematic diagram of the structure of the mid-infrared zoom system of the present invention;

[0030] Fig.10 is a MTF curve diagram of the mid-infrared zoom system of the present invention;

[0031] Fig.11 It is a schematic diagram of the structure of the long-wave infrared zoom system of the present invention;

[0032] Fig.12 It is the MTF curve diagram of the long-wave infrared zoom system of the present invention.

[0033] In the figure: 1. Main optical system; 11. Simulated target; 12. Primary mirror; 13. Secondary mirror; 14. Third mirror; 15. Fourth mirror; 2. Distance zoom simulation system; 21. Visible light detector; 22. Near-infrared detector; 23. Medium-wave infrared detector; 24. Long-wave infrared detector; 25. Filter; 26. Aperture; 3. Mechanical compensation zoom system; 31. Front fixed group; 32. Zoom group; 33. Compensation group; 34. Rear fixed group. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. 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 this field without creative work are within the scope of protection of the present invention.

[0035] A multi-band distance simulation zoom system, such as Figure 1As shown, it includes a main optical system 1 and a distance zoom simulation system 2. The main optical system 1 adopts an object-side telecentric optical path to allow parallel incident object-side light to reach the image plane for imaging; the distance zoom simulation system 2 has a built-in mechanical compensation zoom system 3 to perform distance simulation on a fixed distance scaled simulated object and to simulate the equivalent simulation of the object from far to near and from a point source to a surface source.

[0036] In order to truly simulate the scattered light characteristics of the object under test, it is necessary to minimize the scattering angle error and ensure that the light collected from each point on the object under test is parallel to the central axis of the system. At the same time, it is required that the simulated distance change between the object under test and the receiving lens does not affect the image magnification, that is, the simulated forward and backward movement caused by the movement of the object under test does not affect its image size. Therefore, choosing the object telecentric optical path as the receiving optical system can ensure that only parallel incident object light reaches the image plane for imaging, meeting the above requirements. The setting of the cone angle of a single object point in the design will comprehensively consider the receiving energy, speckle angle size and system resolution.

[0037] Combination Figure 2 , Figure 3 , the imaging quality of the system is characterized by parameters such as modulation transfer function, field curvature / distortion and relative illumination. As can be seen from the figure, the modulation transfer function of all fields of view of the system is greater than 0.7 at 1LP / mm, which meets the target feature identification requirement that the system resolution must reach 16 line pairs / 50mm, and reserves sufficient image quality space for the subsequent optical system; the maximum distortion is 0.1368%, and the meridian / sagittal field curvature is 0.8113mm and 0.5304mm respectively, which meets the imaging requirements. The lowest edge illumination appears in the +y axis, which is 98.74% of the center illumination, indicating that the system illumination is uniform and there is no obvious dark corner.

[0038] like Figure 1As shown, the main optical system 1 includes a primary mirror 12, a secondary mirror 13, a third mirror 14 and a fourth mirror 15. The primary mirror 12 is set up near the simulated target 11, the secondary mirror 13 is located at the reflection end of the primary mirror 12, the third mirror 14 is located at the reflection end of the secondary mirror 13, and the fourth mirror 15 is located at the reflection end of the third mirror 14. The primary optical system 1 adopts a double 4f structure, and the primary mirror 12, the secondary mirror 13 and the third mirror 14, the fourth mirror 15 respectively form a 10 times zoom 4f system. At the same time, since the system adopts an object-side telecentric optical path, within a certain range, the size of the target on the image plane is independent of its distance to the primary optical system, so that the target size can be accurately measured. Among them, the primary mirror 12 adopts a 2.2m off-axis spherical mirror design, and two reversing plane mirrors are added between the primary mirror 12 and the secondary mirror 13, which are used to fold the optical path and correct the tilt aberration, so that the optical system after the primary mirror 12 can be arranged in a smaller space, which is more compact, and cooperates with the primary mirror 12 to achieve alignment between the optical path and the target. The secondary mirror 13 and the third mirror 14 are both designed with off-axis hyperboloids to correct the spherical aberration of the primary mirror 12. The fourth mirror 15 is a parabolic reflector, and its off-axis angle is slightly larger than that of the primary mirror 12, so as to deviate its reflected light beam from the main light path as much as possible to avoid obstruction, and to appropriately increase the object cone angle, thereby increasing the light energy entering the subsequent incoherent imaging optical system.

[0039] The zoom system is an optical structure that can continuously change the focal length while maintaining the position and quality of the image stable. However, when the focal length of the lens is adjusted by changing the lens gap, the image plane will be offset. In order to solve this problem, most people choose the following two zoom compensation methods: optical compensation and mechanical compensation. The present invention uses mechanical compensation to achieve this. Figure 4 As shown, the mechanical compensation zoom system 3 consists of four parts: a front fixed group 31, a zoom group 32, a compensation group 33, and a rear fixed group 34. Mechanical compensation is divided into positive group compensation and negative group compensation according to the positive and negative optical focal length. When the positive group compensation zoom system moves from the short focal end to the long focal end, the zoom group 32 and the compensation group 33 will move in opposite directions; however, the zoom group 32 and the compensation group 33 of the negative group compensation zoom system will first move in opposite directions, and then move to the right together, causing the compensation curve of the system to become more curved. When zooming continuously, the movement points of the relative positions of the zoom group 32 and the compensation group 33 during the movement process need to be defined. During the movement, the zoom group 32 moves at a uniform speed, and at the same time, the compensation group 33 changes speed according to the optical design point.

[0040] By setting the parameters of the optical system and the object to be measured, the distance simulation of the object to be measured with a fixed distance scale is carried out. By adjusting the effective focal length of the zoom system, the image size of the object to be measured on the detector target surface is changed, thereby simulating the equivalent simulation of the object to be measured from far to near, from point source to surface source. The simulation parameters are shown in the following table:

[0041]

[0042]

[0043] In order to realize quantitative simulation of the multi-band dynamic imaging process of the measured object, the present invention provides four bands for simulation experiments, namely, the visible light band, the near infrared band, the medium-wave red band and the long-wave infrared band.

[0044] 1) Visible light band

[0045] Combination Figure 1 , Figure 5 For the zoom system, the secondary spectrum of each focal length segment changes with the change of focal length, and the maximum value of the secondary spectrum appears at the telephoto end. Since the on-axis light at the telephoto end and the off-axis light at the short focal end are both at a higher height than the front fixed group 31, the front fixed group 31 is mainly used to correct the spherical aberration, sine difference, field curvature and distortion at the telephoto end, and can also correct the astigmatism, distortion and off-axis spherical aberration at the short focal end. At the same time, it also contributes to most of the secondary spectrum of the system. Therefore, the system adopts a more complex single, single and double structure with negative, negative and positive focal powers. Among them, the first piece of the front fixed group 31 adopts CaF material, and the tail piece adopts HZLAF and HZK double cemented lens to balance chromatic aberration and secondary spectrum. The zoom group 32 undertakes the zoom function of the entire optical system. It adopts HZF88 with strong dispersion ability as positive lens and HFK as negative lens to correct chromatic aberration, so as to ensure that the entire zoom group 32 has a small residual chromatic aberration. The compensation group 33 is close to the aperture 26, so that the off-axis light height is reduced, and the off-axis aberrations such as astigmatism and distortion are small, focusing on the correction of the spherical aberration, sine aberration and its higher-order aberrations on the axis. In order to shorten the system length, the structure of the compensation group 33 is determined to be a telephoto structure. The rear fixed group 34 can ensure that the system focal length remains unchanged, compensate for the residual aberrations of the previous components, especially the residual secondary spectrum, and is responsible for collimating the light beam to facilitate the installation of other optical components.

[0046] like Figure 6 As shown, the imaging quality of the optical system is usually evaluated by the optical transfer function (MTF). The area enclosed by the MTF curve and the coordinate axis is generally used to represent the imaging quality. The larger the area, the better the imaging quality. The larger the MTF value at the cutoff frequency, the better the imaging quality. The measurement is performed by a visible light detector 21, such as Figure 6 As shown in the figure, the MTF of the system at any focal length is close to the diffraction limit in the on-axis field of view, and the imaging quality is good.

[0047] 2) Near infrared band

[0048] Combination Figure 1 , Figure 7, the entire system for measuring this band is composed of 18 spherical lenses and color filters. Within the full focal length range, the aperture 26 remains fixed. Similar to the design concept of the visible light zoom system, the near-infrared zoom lens is a four-element positive group compensation structure, in which the front fixed group 31 is composed of three single lenses and one cemented lens. Three pieces of ultra-low dispersion glass are used, which effectively reduces the secondary spectrum and plays a great role in improving the image quality of the long focal length segment. When the temperature changes and the working distance changes, it can also be used as the focusing structure of the system. The zoom group 32 is composed of two single lenses and one cemented lens. In the system, it not only undertakes the zoom function, but also plays a great role in improving the image quality of the short focal length segment. The compensation group 33 is composed of two single lenses and one cemented lens, with positive focal power, which is used to compensate for the image plane movement caused by the movement of the zoom group 32, and plays a great role in improving the image quality of the medium focal length segment. The rear fixed group 34 is composed of three single lenses and one cemented lens, and is used to correct the residual aberration of the system, and plays an important role in the aberration balance of different focal length segments of the system.

[0049] Combination Figure 1 , Figure 8 , measured by the near-infrared detector 22, when the spatial frequency is 33LP / mm, the central field MTF of a randomly selected focal length segment is greater than 0.7, and the edge field MTF is greater than 0.5, which is sufficient to meet the system imaging quality requirements.

[0050] 3) Mid-wave infrared band

[0051] Combination Figure 1 , Fig. 9 The structure for measuring this band adopts a composite zoom structure to achieve continuous zoom, which is composed of a two-stage zoom structure of a front zoom lens group and a relay magnifying lens group connected in series. When the focal length is short, the front zoom lens group takes on the main role of zooming, and the image plane offset is compensated by moving the relay moving group forward and backward; when the focal length is long, the two have opposite effects. In addition, the defocus caused by changes in temperature, air pressure, etc. can be compensated by moving the relay moving group forward and backward. The system contains a total of eight lenses and two reflectors, and only two infrared materials, germanium and silicon, are used. The system size is better than 200mm×200mm×200mm. Among them, the front fixed group 31 uses high-refractive-index, low-dispersion silicon material, which bears the main optical power. The zoom group 32 has a negative optical power, uses high-dispersion, high-refractive-index germanium material, and uses an aspherical surface on the front surface to correct off-axis aberrations at different focal lengths. The compensation group 33 adopts a double-separation structure, both of which are made of silicon material, and cooperates with the rear fixed group to correct the primary aberration of the front zoom lens group; the relay lens group adopts a typical dual-field system structure, and the dynamic group uses low-dispersion, high-refractive-index silicon material, which cooperates with the fixed group to achieve focal length magnification of the front group while correcting the system's residual chromatic aberration and other advanced aberrations.

[0052] Combination Figure 1 , Fig.10 , measured by the medium-wave infrared detector 23, the MTF values ​​of the central field of view at each zoom position of the system at the cutoff frequency of 33LP / mm are all around 0.3, close to the diffraction limit, and the MTF of each off-axis field of view is reasonably distributed, indicating that the system has good imaging quality.

[0053] 4) Long-wave infrared band

[0054] Combination Figure 1 , Fig.11 The system structure for measuring this band consists of a traditional continuous zoom section and a two-step zoom section in series. The two-step zoom section consists of a variable magnification group 32 and a rear fixed group 34. The zoom system consists of 6 lens groups and 9 lenses in total. The optical system uses only two infrared materials, germanium and zinc selenide. The aperture 26 is located at the 9th surface of the system, which is conducive to correcting the chromatic aberration of the system at the telephoto end. During the entire zoom process, the image plane position of the system remains unchanged.

[0055] Combination Figure 1 , Fig.12 , measured by a long-wave infrared detector, the modulation transfer function at each field of view is close to the diffraction limit and is greater than 0.6 at the cutoff frequency of 16.7LP / mm.

[0056] like Figure 1 As shown, in order to simulate the energy change process from long-distance to close-up movement, the system uses a filter 25 and an aperture 26 to achieve the change of the received light energy. The filter 25 and the aperture 26 are important components for regulating and controlling the transmission of light energy in the optical system. They can adjust the energy distribution and spectral composition in the detection or imaging system.

[0057] The aperture 26 is an opening or obstacle in the optical path, which is used to limit the size or shape of the light beam passing through the system. The principle of adjusting the energy is based on the principle of geometric optics, and the total amount of energy is controlled by reducing the diameter of the light beam entering the detector. A smaller aperture 26 can reduce the entry of stray light and light from non-interested areas, thereby improving image contrast and signal-to-noise ratio.

[0058] The filter 25 adjusts energy through a selective transmission mechanism. It allows light of a specific wavelength range to pass through, while blocking or attenuating light of other wavelengths. This function is based on the absorption, reflection or transmission characteristics of a substance to different wavelengths of light. In detection applications, by using filters, unwanted background light or interfering spectra can be filtered out.

[0059] In the present invention, the filter 25 and the aperture 26 are provided to adjust and optimize the energy distribution in the detection system from the spatial dimension and the spectral dimension respectively by limiting the light beam size and controlling the spectral composition, so as to improve the detection efficiency, accuracy and specificity.

[0060] In summary, the present invention provides a novel multi-band distance simulation zoom system, which can obtain the optical characteristics of the object under test during the movement from a long distance to a close distance in the laboratory, and realize the quantitative simulation of the multi-band dynamic imaging process of the object under test.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multi-band distance simulation zoom system, characterized in that: The invention comprises a main optical system (1) and a distance zoom simulation system (2). The main optical system (1) adopts an object telecentric optical path to allow parallel incident object light to reach an image plane to form an image. The distance zoom simulation system (2) is equipped with a mechanical compensation zoom system (3) to simulate the distance of a fixed distance scaled object to be measured and to simulate the equivalent of the object to be measured from far to near and from a point source to a surface source.

2. The multi-band distance simulation zoom system according to claim 1, characterized in that: The main optical system (1) comprises a main mirror (12), a secondary mirror (13), a third mirror (14) and a fourth mirror (15); the main mirror (12) is mounted on a side close to a simulated target (11); the secondary mirror (13) is located at a reflection end of the main mirror (12); the third mirror (14) is located at a reflection end of the secondary mirror (13); and the fourth mirror (15) is located at a reflection end of the third mirror (14); the main mirror (12) and the secondary mirror (13), the third mirror (14) and the fourth mirror (15) respectively form a 10-fold zoom 4f system so that the size of the simulated target (11) on the image plane is independent of its distance from the main optical system (1).

3. The multi-band distance simulation zoom system according to claim 2, characterized in that: The primary mirror (12) is a 2.2m off-axis spherical mirror, the secondary mirror (13) and the third mirror (14) are off-axis hyperbolic mirrors, and the fourth mirror (15) is a parabolic reflector.

4. The multi-band distance simulation zoom system according to claim 3, characterized in that: Two folding plane mirrors are arranged between the primary mirror (12) and the secondary mirror (13) to fold the optical path and correct the tilt aberration.

5. The multi-band distance simulation zoom system according to claim 4, characterized in that: The off-axis angle of the quad mirror (15) is greater than the off-axis angle of the primary mirror (12) so as to deviate the reflected light beam from the primary light path.

6. The multi-band distance simulation zoom system according to claim 5, characterized in that: The mechanical compensation zoom system (3) comprises a front fixed group (31), a zoom group (32), a compensation group (33) and a rear fixed group (34); the front fixed group (31) and the rear fixed group (34) remain in fixed positions; the zoom group (32) and the compensation group (33) are movable structures; and a filter (25) or an aperture (26) is arranged in front of the front fixed group (31).

7. The multi-band distance simulation zoom system according to claim 6, characterized in that: When measuring visible light, the front fixed group (31) adopts a single-single-double structure, wherein the first piece is made of CaF material, and the tail piece adopts HZLAF and HZK double-cemented lenses; the zoom group (32) adopts HZF88 as a positive lens and HFK as a negative lens; the compensation group (33) adopts a telephoto structure.

8. The multi-band distance simulation zoom system according to claim 6, characterized in that: When measuring near infrared, the front fixed group (31) is composed of three single lenses and one cemented lens, the zoom group (32) is composed of two single lenses and one cemented lens, the compensation group (33) is composed of two single lenses and one cemented lens, and the rear fixed group (34) is composed of three single lenses and one cemented lens.

9. The multi-band distance simulation zoom system according to claim 6, characterized in that: When measuring mid-wave infrared, the front fixing group (31) is made of silicon material, the variable power group (32) is made of germanium material with negative optical power, and the compensation group (22) is made of silicon material to form a double separation structure.

10. The multi-band distance simulation zoom system according to claim 6, characterized in that: When measuring long-wave infrared, the mechanical compensation zoom system is made of two materials: germanium and zinc selenide.

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