Focal plane compensation method and focal plane compensation system of multispectral imaging system

Abstract

The invention provides a focal plane compensation method and system for a multispectral imaging system, and the method comprises the steps: designing the multispectral imaging system according to optical parameters, and obtaining an initial structure; optical filters of different imaging wavebands are designed according to the imaging spectral range; the thicknesses of the optical filters of different imaging wavebands are designed according to the refractive indexes of the optical filters corresponding to the imaging wavebands; splicing the optical filters of different wave bands; and the spliced optical filter is installed at the front end of a detector of the multispectral imaging system according to the distance parameter of the initial structure design, and multispectral focal plane compensation is completed. Different optical filter thicknesses are designed according to optical filters of different imaging wavebands, chromatic aberration compensation of different wavebands can be completed, the optimal imaging effect of each waveband is obtained, only the thickness of the optical filter needs to be changed, more components do not need to be added according to the design result, different multispectral imaging systems can be suitable, the application range is wide, and the cost is low. And the influence on the volume, weight and cost of the whole system is small.

Description

Technical Field

[0001] The invention relates to the technical field of optical imaging, and in particular to a focal plane compensation method for a spectral imaging system and a focal plane compensation system for a multi-spectral imaging system. Background Art

[0002] With the development of remote sensing technology, multispectral imaging systems are widely used in agriculture, environmental monitoring, medical diagnosis and other fields because of their ability to capture light of different wavelengths.

[0003] However, due to the dispersion characteristics of optical components, the focusing positions of light of different wavelengths in the imaging system may deviate, resulting in a decrease in imaging quality.

[0004] In related technologies, multispectral imaging is often achieved through achromatization at the optical system design level. Achromatization may require more lenses, more aspherical surfaces, and more different materials than conventional designs, which increases the volume, weight, and cost of the optical system to a certain extent. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a focal plane compensation method for a multi-spectral imaging system.

[0006] The invention also provides a focal plane compensation system for the multi-spectral imaging system.

[0007] The technical solution adopted by the present invention is as follows:

[0008] The first aspect of the present invention proposes a focal plane compensation method for a multispectral imaging system, comprising the following steps: designing a multispectral imaging system according to optical parameters to obtain an initial structure, wherein the multispectral imaging system comprises: an optical convergence unit, a filter and a detector; designing filters of different imaging bands according to the imaging spectral range; designing the thickness of filters of different imaging bands according to the refractive index of the filters corresponding to the imaging bands; splicing filters of different bands; installing the spliced ​​filters at the front end of the detector of the multispectral imaging system according to the distance parameters of the initial structure design to complete the multispectral focal plane compensation.

[0009] The focal plane compensation method of the multispectral imaging system proposed in the present invention also has the following additional technical features:

[0010] According to one embodiment of the present invention, the thickness of filters for different imaging bands is designed according to the refractive index of the imaging band corresponding to the filter, specifically including: calculating the translation distance of the filter image point position according to the refractive index of the imaging band corresponding to the filter and the filter thickness; and obtaining the thickness of the filters for different imaging bands based on the criterion of the smallest translation position.

[0011] According to one embodiment of the present invention, the translation distance of the filter image point position is calculated according to the following formula: Where, ΔL ′ is the translation distance of the filter image point position, d is the filter thickness, and n is the refractive index of the filter.

[0012] According to an embodiment of the present invention, the focal plane compensation method of the multi-spectral imaging system further includes: stitching imaging of each band through push-scan imaging to achieve multi-spectral imaging.

[0013] The second aspect of the present invention proposes a focal plane compensation system for a multi-spectral imaging system, including: a first design module, the first design module is used to design the multi-spectral imaging system according to optical parameters to obtain an initial structure, the multi-spectral imaging system includes: an optical convergence unit, a filter and a detector; a second design module, the second design module is used to design filters of different imaging bands according to the imaging spectral range; a third design module, the third design module is used to design the thickness of filters of different imaging bands according to the refractive index of the filter corresponding to the imaging band; a splicing module, the splicing module is used to splice filters of different bands; a compensation module, the compensation module is used to install the spliced ​​filters at the front end of the detector of the multi-spectral imaging system according to the distance parameters of the initial structure design to complete the multi-spectral focal plane compensation.

[0014] The focal plane compensation system of the multispectral imaging system of the present invention also has the following additional technical features:

[0015] According to one embodiment of the present invention, the third design module is specifically used to: calculate the translation distance of the filter image point position based on the refractive index of the filter corresponding to the imaging band and the filter thickness; and obtain the thickness of the filter of the different imaging bands based on the criterion of the smallest translation position.

[0016] According to an embodiment of the present invention, the third design module calculates the translation distance of the filter image point position according to the following formula: Where, ΔL ′ is the translation distance of the filter image point position, d is the filter thickness, and n is the refractive index of the filter.

[0017] According to an embodiment of the present invention, the focal plane compensation system of the multispectral imaging system further includes: an imaging module, which is used to stitch imaging of each band through push-scan imaging to achieve multispectral imaging.

[0018] The present invention has the following beneficial effects:

[0019] The present invention designs different filter thicknesses for filters of different imaging bands, which can complete chromatic aberration compensation for different bands, so that the transfer functions of medium waves and long waves can be very close to the diffraction limit, and the best imaging effect of each band is obtained. Moreover, the design result only requires changing the filter thickness without adding more components, and different multi-spectral imaging systems can be applicable. Not only does it have a wide range of applications, but it also has little impact on the volume, weight and cost of the entire system. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a flow chart of a focal plane compensation method for a multi-spectral imaging system according to an embodiment of the present invention;

[0021] Figure 2 is a schematic structural diagram of a multispectral imaging system according to an embodiment of the present invention;

[0022] Figure 3 It is a schematic diagram of the deviation of the imaging position of the medium wave and the long wave during imaging of the multi-spectral imaging system;

[0023] Figure 4 It is a schematic diagram of the translation of the filter image point position when the multi-spectral imaging system is imaging;

[0024] Figure 5 is the optical transfer function curve of the medium wave without focal plane compensation;

[0025] Figure 6 is the optical transfer function curve of long wave without focal plane compensation;

[0026] Figure 7 It is the optical transfer function curve of the medium wave for focal plane compensation;

[0027] Figure 8 It is the optical transfer function curve of long wave for focal plane compensation;

[0028] Fig. 9 4 is a block diagram of a focal plane compensation system of a multi-spectral imaging system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only 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.

[0030] The following is a description of a focal plane compensation method for a multi-spectral imaging system provided in an embodiment of the present invention in conjunction with the accompanying drawings.

[0031] Figure 1 is a flow chart of a focal plane compensation method for a multi-spectral imaging system according to an embodiment of the present invention. Figure 1 As shown, the method comprises the following steps:

[0032] S1, designing a multispectral imaging system according to optical parameters to obtain an initial structure. The multispectral imaging system includes: an optical converging unit, a filter, and a detector.

[0033] Specifically, Figure 2 As shown, the multi-spectral imaging system includes: an optical converging unit 1, a filter 2 and a detector 3. The optical converging unit 1 includes: a lens, a reflector or a scanning mirror and other components. The optical converging unit 1 is used to adjust the direction of light in different fields of view and focus the light beam, and then amplify and incident on the filter 2. The filter 2 divides the light into multiple different bands, and the light of each band is then received by the detector 3.

[0034] S2, designs filters of different imaging bands according to the imaging spectral range.

[0035] Specifically, the bands required for imaging can be obtained according to actual needs, and the band and width of the band filter can be selected according to the range of imaging required for each band and combined with the field of view and focal length of the optical system, so that different areas of the detector have different imaging bands, thus realizing multispectral imaging.

[0036] S3, designing the thickness of filters for different imaging bands according to the refractive index of the filters corresponding to the imaging bands.

[0037] Specifically, Figure 3 As shown in the figure, due to the different imaging bands of the filters, the corresponding refractive indices are also different, and there is chromatic aberration between the medium-wave and long-wave spectral bands. Figure 3 ΔL in is the deviation between the imaging positions of medium wave and long wave. It is difficult to completely correct ΔL, which results in that the imaging quality of the two bands cannot reach the optimal state at the same time, and a trade-off needs to be made. The wavelength of medium wave is generally 3-5 μm, and the wavelength of long wave is generally 7-14 μm. In the present invention, different filter thicknesses are designed according to different imaging bands for correction.

[0038] Specifically, further, according to an embodiment of the present invention, the thickness of filters for different imaging bands is designed according to the refractive index of the filter corresponding to the imaging band, specifically including: calculating the translation distance of the filter image point position according to the refractive index of the filter corresponding to the imaging band and the filter thickness; and obtaining the thickness of filters for different imaging bands based on the criterion of the smallest translation position.

[0039] Specifically, the filter can be regarded as a parallel plate during actual imaging, such as Figure 4 As shown in the figure, when parallel plates are used for imaging, the position of the image points will change. Figure 4 In, ΔL′ That is, the translation distance of the filter image point position when the multispectral imaging system is imaging.

[0040] In a specific embodiment of the present invention, the translation distance of the filter image point position is calculated according to the following formula:

[0041]

[0042] Where, ΔL ′ is the translation distance of the filter image point position, d is the filter thickness, and n is the refractive index of the filter.

[0043] Therefore, according to the refractive index n of the filter, ΔL ′ The design filter thickness is ΔL with a target of 0. ′ The smaller the better. By changing the filter thickness through the parallel plate imaging characteristics of the filter, chromatic aberration compensation in different bands can be completed, focal plane compensation can be performed, and the image quality of medium wave and long wave at the same image plane can meet the requirements.

[0044] S4, stitching filters of different bands.

[0045] After the filters are designed according to the above method, the filters of different bands are spliced.

[0046] S5, installing the spliced ​​filter at the front end of the detector of the multi-spectral imaging system according to the distance parameter of the initial structure design to complete the multi-spectral focal plane compensation.

[0047] Specifically, according to the distance parameter between the filter and the detector designed in the initial structure in S1, the distance parameter is kept unchanged, and the spliced ​​filter is installed to complete the focal plane compensation of the multispectral imaging system and improve the imaging quality.

[0048] The focal plane compensation method of the multi-spectral imaging system of the present invention further comprises: stitching imaging of each waveband by push-scan imaging to realize multi-spectral imaging.

[0049] In order to verify the effect of the focal plane compensation method of the present invention, the inventors conducted relevant experiments. Figure 5 is the optical transfer function curve of the medium wave without focal plane compensation. Figure 6 It is the optical transfer function curve of long wave without focal plane compensation. Figure 7 It is the optical transfer function curve of the medium wave for focal plane compensation; Figure 8 is the optical transfer function curve of the long wave for focal plane compensation. Figure 7 and Figure 8 It can be seen from the optical transfer function curve that by adopting the compensation method of the present invention, the medium and long wave transfer functions can be very close to the diffraction limit, completing the multi-spectral confocal surface design. Figure 5-Figure 8 In the figure, the horizontal axis is the spatial frequency, and the vertical axis is the OTF (Optical Transfer Function) modulus.

[0050] In summary, according to the focal plane compensation method of the multispectral imaging system of the embodiment of the present invention, different filter thicknesses are designed for filters of different imaging bands, which can complete the chromatic aberration compensation of different bands, so that the transfer functions of medium wave and long wave can be very close to the diffraction limit, and the best imaging effect of each band is obtained. Moreover, the design result only needs to change the filter thickness without adding more components. Different multispectral imaging systems can be applicable, which not only has a wide range of applications, but also has little impact on the volume, weight and cost of the entire system.

[0051] Corresponding to the focus plane compensation method of the multi-spectral imaging system described above, the present invention also provides a focus plane compensation system for the multi-spectral imaging system. Since the system embodiment of the present invention corresponds to the method embodiment described above, for details not disclosed in the system embodiment, reference can be made to the method embodiment described above, and no further description will be given in the present invention.

[0052] Fig. 9 is a block diagram of a focal plane compensation system of a multi-spectral imaging system according to an embodiment of the present invention. Fig. 9 As shown, the focal plane compensation system includes: a first design module 100 , a second design module 200 , a third design module 300 , a splicing module 400 and a compensation module 500 .

[0053] The first design module 100 is used to design a multispectral imaging system according to optical parameters to obtain an initial structure. The multispectral imaging system includes: an optical convergence unit, a filter and a detector; the second design module 200 is used to design filters of different imaging bands according to the imaging spectral range; the third design module 300 is used to design the thickness of filters of different imaging bands according to the refractive index of the filter corresponding to the imaging band; the splicing module 400 is used to splice filters of different bands; the compensation module 500 is used to install the spliced ​​filters at the front end of the detector of the multispectral imaging system according to the distance parameters of the initial structure design to complete the focal plane compensation of the multispectrum.

[0054] According to one embodiment of the present invention, the third design module 300 is specifically used to: calculate the translation distance of the filter image point position based on the refractive index of the filter corresponding to the imaging band and the filter thickness; and obtain the thickness of the filter in different imaging bands based on the criterion of small translation position.

[0055] According to an embodiment of the present invention, the third design module 300 specifically calculates the translation distance of the filter image point position according to the following formula: Where, ΔL ′is the translation distance of the filter image point position, d is the filter thickness, and n is the refractive index of the filter.

[0056] According to an embodiment of the present invention, the focal plane compensation system of the multispectral imaging system further includes: an imaging module, the imaging module being used to stitch imaging of each band through push-scan imaging to achieve multispectral imaging.

[0057] In summary, according to the focal plane compensation system of the multispectral imaging system of the embodiment of the present invention, different filter thicknesses are designed for filters of different imaging bands, which can complete the chromatic aberration compensation of different bands, so that the transfer functions of medium wave and long wave can be very close to the diffraction limit, and the best imaging effect of each band is obtained. Moreover, the design result only needs to change the filter thickness without adding more components. Different multispectral imaging systems can be applicable, which not only has a wide range of applications, but also has little impact on the volume, weight and cost of the entire system.

[0058] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. "Multiple" means two or more, unless otherwise clearly and specifically defined.

[0059] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0060] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code comprising one or more executable instructions for implementing the steps of a custom logical function or process, and the scope of the preferred embodiments of the present invention includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present invention belong.

[0061] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in combination with these instruction execution systems, devices or apparatuses. For the purpose of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in combination with these instruction execution systems, devices or apparatuses. More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk box (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), a fiber optic device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium and then editing, interpreting or processing in other suitable ways if necessary, and then stored in a computer memory.

[0062] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0063] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0064] In addition, each functional unit in each embodiment of the present invention may be integrated into a processing module, or each unit may exist physically separately, or two or more units may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. If the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium.

[0065] The storage medium mentioned above can be a read-only memory, a magnetic disk or an optical disk, etc.

[0066] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A focal plane compensation method for a multispectral imaging system, characterized in that: The following steps are involved: Designing a multi-spectral imaging system according to optical parameters to obtain an initial structure, wherein the multi-spectral imaging system includes: an optical converging unit, a filter, and a detector; Design filters of different imaging bands according to the imaging spectral range; The thickness of filters for different imaging bands is designed according to the refractive index of the filters corresponding to the imaging bands; Splice filters of different wavelength bands; The spliced ​​filter is installed at the front end of the detector of the multi-spectral imaging system according to the distance parameters of the initial structure design to complete the multi-spectral focal plane compensation.

2. The focal plane compensation method of the multispectral imaging system according to claim 1, characterized in that: The thickness of filters for different imaging bands is designed according to the refractive index of the filters corresponding to the imaging bands, including: The translation distance of the filter image point position is calculated according to the refractive index of the filter corresponding to the imaging band and the filter thickness; The thickness of the filters of the different imaging bands is obtained based on the principle that the translation position is small.

3. The focal plane compensation method of the multispectral imaging system according to claim 2, characterized in that: Specifically, the translation distance of the filter image point position is calculated according to the following formula: Where, ΔL ′ is the translation distance of the filter image point position, d is the filter thickness, and n is the refractive index of the filter.

4. The focal plane compensation method of the multispectral imaging system according to claim 1, characterized in that: Also includes: Push-broom imaging is used to stitch images of various bands to achieve multispectral imaging.

5. A focal plane compensation system for a multispectral imaging system, characterized in that: include: A first design module, the first design module is used to design a multi-spectral imaging system according to optical parameters to obtain an initial structure, the multi-spectral imaging system comprising: an optical converging unit, a filter and a detector; A second design module, the second design module is used to design filters of different imaging bands according to the imaging spectral range; A third design module, the third design module is used to design the thickness of filters of different imaging bands according to the refractive index of the filters corresponding to the imaging bands; A splicing module, which is used to splice filters of different wavelength bands; The compensation module is used to install the spliced ​​filter at the front end of the detector of the multi-spectral imaging system according to the distance parameters of the initial structure design to complete the multi-spectral focal plane compensation.

6. The focal plane compensation system of the multi-spectral imaging system according to claim 5, characterized in that: The third design module is specifically used for: The translation distance of the filter image point position is calculated according to the refractive index of the filter corresponding to the imaging band and the filter thickness; The thickness of the filters of the different imaging bands is obtained based on the principle that the translation position is small.

7. The focal plane compensation system of the multi-spectral imaging system according to claim 6, characterized in that: The third design module specifically calculates the translation distance of the filter image point position according to the following formula: Where, ΔL ′ is the translation distance of the filter image point position, d is the filter thickness, and n is the refractive index of the filter.

8. The focal plane compensation system of the multi-spectral imaging system according to claim 5, characterized in that: Also includes: An imaging module is used to stitch imaging of each band through push-scan imaging to achieve multi-spectral imaging.

Images