CN110927854A - Large-depth-of-field observation receiving system based on non-rotational-symmetry phase plate - Google Patents
Large-depth-of-field observation receiving system based on non-rotational-symmetry phase plate Download PDFInfo
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- CN110927854A CN110927854A CN201911078119.XA CN201911078119A CN110927854A CN 110927854 A CN110927854 A CN 110927854A CN 201911078119 A CN201911078119 A CN 201911078119A CN 110927854 A CN110927854 A CN 110927854A
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/30—Polarising elements
- G02B5/3083—Birefringent or phase retarding elements
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/0012—Optical design, e.g. procedures, algorithms, optimisation routines
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
- H04N23/50—Constructional details
- H04N23/55—Optical parts specially adapted for electronic image sensors; Mounting thereof
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Abstract
The invention belongs to the field of optics, and aims to effectively reduce the defocusing sensitivity of an imaging system on the premise of not sacrificing resolution and light transmission quantity so as to expand the depth of field of the system. Therefore, the technical scheme adopted by the invention is that the large-depth-of-field observation receiving system based on the non-rotational-symmetry phase plate comprises an imaging lens, the phase plate and a detection decoding unit; the phase plate and the imaging lens are arranged separately and are positioned on the same optical axis; the phase plate is used as a diaphragm of an imaging system to realize wavefront coding; the output signal of the detector passes through a video decoding unit, and the encoded blurred image is restored by using a decoding algorithm. The method is mainly applied to the occasions of video detection and field depth processing.
Description
Technical Field
The invention belongs to the field of optics, relates to a phase plate and an imaging system based on the phase plate, and particularly relates to a non-rotational symmetric phase plate for expanding the depth of field of an optical system and a large-depth-of-field observation receiving system using the phase plate.
Background
To improve the range and fineness of observation, imaging systems are generally required to have both higher resolution and greater depth of field. The effect of expanding the depth of field can be achieved by reducing the relative aperture of the imaging system, but the resolution and the illumination of the system are reduced; the multi-defocus image synthesis method increases the hardware volume and takes a long time, and cannot be applied to a small-volume imaging system.
The wavefront coding technology combines image processing and optical design, and adds a phase mask plate at the aperture of an optical system, so as to code the wavefront and make the system insensitive to defocusing. And the intermediate blurred image is decoded by combining with a proper digital filtering processing technology, so that a defocused clear image can be obtained, and the depth of field of the imaging system is effectively expanded on the premise of not sacrificing the resolution and the light transmission quantity of the system. At present, no report related to the mature technology exists.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide a non-rotational-symmetry phase plate and a method for expanding the depth of field of an imaging system based on the phase plate. The method can effectively reduce the defocusing sensitivity of the imaging system on the premise of not sacrificing the resolution and the light transmission amount, thereby expanding the depth of field of the system. Therefore, the technical scheme adopted by the invention is that the large-depth-of-field observation receiving system based on the non-rotational-symmetry phase plate comprises an imaging lens, the phase plate and a detection decoding unit; the phase plate and the imaging lens are arranged separately and are positioned on the same optical axis; the phase plate is used as a diaphragm of an imaging system to realize wavefront coding; the output signal of the detector passes through a video decoding unit, and the encoded blurred image is restored by using a decoding algorithm.
The phase plate is a non-rotational symmetry type phase plate formed by superposing quadratic, cubic and quintic power functions, and the phase distribution function expression of the phase plate is as follows:
f(x,y)＝α(x2+y2)+β(x3+y3)+γ(x5+y5)
wherein α and gamma are parameters of quadratic term, cubic term and quintic term in phase distribution function of the phase plate, x and y are two-dimensional aperture normalization coordinates with value range of [ -1,1 ].
The invention has the characteristics and beneficial effects that:
(1) on the premise of not sacrificing the resolution, the depth of field of the imaging system is increased by one order of magnitude, the imaging system has a larger imaging space, and more information of an object can be acquired, so that the observation range of the imaging system is greatly enlarged;
(2) the depth of field can be greatly increased, various aberrations caused by defocusing, such as spherical aberration, chromatic aberration, astigmatism, Petzian field curvature, defocusing caused by installation errors and temperature change and the like, can be corrected, and the imaging performance of the system is more excellent;
(3) the depth of field is expanded by utilizing the wavefront coding technology, and the number of optical elements can be reduced, so that the size and the weight of an imaging system are reduced, and the cost is reduced.
(4) The fuzzy images under different defocusing amounts can be decoded by using the same digital filtering algorithm, and the decoding algorithm is simple and efficient.
(5) Compared with a classical cubic phase plate, the non-rotational symmetry type phase plate with the superposed quadratic, cubic and quintic power functions can effectively reduce the defocusing sensitivity of the system, has a larger field depth expansion range and has lower optimization calculation burden;
(6) compared with a sinusoidal phase plate and an exponential phase plate, the phase plate has smaller PSF offset effect; the MTF level is higher and thus the quality and contrast of the intermediate image is higher and the recoverability of the image is better.
(7) The sine function and the exponential function are sensitive to parameters, so that the requirement on the precision of the phase plate is higher, and the processing difficulty is increased. In the invention, the surface type fluctuation of the phase plate superposed by the quadratic, cubic and quintic power functions is small and monotonous, and the requirement on the processing precision is not high.
Description of the drawings:
fig. 1 is a diagram illustrating an exemplary structure of extending the depth of field of an imaging system based on a non-rotational-symmetric phase plate according to the present invention.
FIG. 2 is a phase distribution diagram of a non-rotationally symmetric phase plate according to the present invention.
Fig. 3 is a plot of MTF curves for different defocus for the observation receiving system without the introduction of a phase plate in accordance with the present invention.
Fig. 4 shows MTF curve clusters of the present invention under different defocus amounts when a non-rotation-symmetric phase plate is introduced.
Detailed Description
In order to solve the technical problem in the prior art, the invention provides a non-rotational-symmetry phase plate and a method for expanding the depth of field of an imaging system based on the phase plate. The method can effectively reduce the defocusing sensitivity of the imaging system on the premise of not sacrificing the resolution and the light transmission amount, thereby expanding the depth of field of the system.
In order to achieve the purpose, the invention adopts the technical scheme that: the large-depth-of-field observation receiving system comprises an imaging lens, a phase plate and a detection decoding unit; the phase plate and the imaging lens are arranged separately and are positioned on the same optical axis; the phase plate is used as a diaphragm of an imaging system to realize wavefront coding; the output signal of the detector passes through a video decoding unit, and the encoded blurred image is restored by using a decoding algorithm.
The invention provides a non-rotational symmetry phase plate formed by superposing quadratic, cubic and quintic power functions on the basis of a classical cubic phase plate, wherein the phase plate has a phase distribution function expression as follows:
f(x,y)＝α(x2+y2)+β(x3+y3)+γ(x5+y5)
wherein α and gamma are parameters of quadratic term, cubic term and quintic term in phase distribution function of the phase plate, x and y are two-dimensional aperture normalization coordinates with value range of [ -1,1 ].
Compared with a cubic phase plate, the phase plate has better performance, the phase plate realizes that the defocusing insensitivity of the system is realized by changing the surface type through the complementary assistance of α and gamma three variable parameters, the optimization degree of freedom is higher, the field depth expansion range of the system is larger, the number of the variable parameters is relatively less, and the burden of optimization calculation is lower.
Compared with an exponential phase plate, the phase plate has lower sensitivity to the optimized initial search position and is simpler to optimize.
Compared with a sine phase plate, the phase plate can realize defocusing invariance without very large phase modulation intensity, and is beneficial to processing.
The receiving part of the large-depth-of-field observation receiving system consists of a detector and a decoding unit. The output signal of the detector passes through a video decoding unit, and the encoded blurred image is restored by using a decoding algorithm, so that a final clear image is obtained.
Because the consistency of the MTF under different defocusing amounts and parameters such as the point charts is selected as the phase plate evaluation index, the method can utilize the same digital filtering algorithm to decode the blurred images under different defocusing amounts, and greatly simplifies the decoding algorithm while ensuring the image recoverability.
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
Fig. 1 is a diagram illustrating an example of extending the depth of field of an imaging system based on a non-rotational symmetric phase plate, and the specific structure of the diagram is shown in the figure.
The original observation system without the phase plate consists of 4 pieces of 3 groups of lenses, can only form clear images in a smaller depth of field range, and has a limited observation range.
The invention adds a non-rotation symmetrical phase plate superposed by quadratic, cubic and quintic power functions at the aperture of the common imaging system, the phase distribution function of the phase plate is shown in figure 2, and the expression of the phase distribution function is as follows:
f(x,y)＝α(x2+y2)+β(x3+y3)+γ(x5+y5)
wherein α and gamma are parameters of quadratic term, cubic term and quintic term in phase distribution function of the phase plate, x and y are two-dimensional aperture normalization coordinates with value range of [ -1,1 ].
The parameters of the surface type of the phase plate needing to be optimized and determined comprise α, β, gamma and 4 parameters of the normalized radius, and the final phase plate is obtained by carrying out parameter optimization on consistency constraints of imaging results at different defocusing positions.
The optimized non-rotation symmetrical phase plate can encode the wave front of an imaging system, so that the system is insensitive to defocusing. As shown in fig. 3 and 4, in the effective spatial frequency range, although the amplitude of the MTF curve of the system introduced with the phase plate is reduced, no zero point exists, which indicates that information beyond the range of the depth of field of the original system is not lost, i.e., the depth of field of the imaging system is expanded.
The phase plate and the imaging lens are arranged separately, and imaging information can be directly received by the detector without the phase plate; when the phase plate is added, namely a wavefront coding system, the intermediate blurred image received by the detector needs to be decoded, so that the final required clear image can be obtained. As the phase plate parameters take MTF consistency of the defocusing system under different defocusing amounts as an optimization standard, digital images under different defocusing amounts can be decoded through the same digital filter, so that clear images in a large depth-of-field range are obtained, the observation receiving range of the imaging system is enlarged, and the practicability of the system is improved.
Claims (2)
1. A large depth of field observation receiving system based on a non-rotational symmetry type phase plate is characterized by comprising an imaging lens, a phase plate and a detection decoding unit; the phase plate and the imaging lens are arranged separately and are positioned on the same optical axis; the phase plate is used as a diaphragm of an imaging system to realize wavefront coding; the output signal of the detector passes through a video decoding unit, and the encoded blurred image is restored by using a decoding algorithm.
2. The system according to claim 1, wherein the phase plate is a non-rotational symmetric phase plate formed by stacking quadratic, cubic and quintic power functions, and the phase plate has a phase distribution function represented by:
f(x,y)＝α(x2+y2)+β(x3+y3)+γ(x5+y5)
wherein α and gamma are parameters of quadratic term, cubic term and quintic term in phase distribution function of the phase plate, x and y are two-dimensional aperture normalization coordinates with value range of [ -1,1 ].
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| CN201911078119.XA CN110927854A (en) | 2019-11-06 | 2019-11-06 | Large-depth-of-field observation receiving system based on non-rotational-symmetry phase plate |
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| CN201911078119.XA CN110927854A (en) | 2019-11-06 | 2019-11-06 | Large-depth-of-field observation receiving system based on non-rotational-symmetry phase plate |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114488524A (en) * | 2022-02-19 | 2022-05-13 | 复旦大学 | Wavefront coding imaging system based on high-order polynomial free-form surface phase plate |
| CN114911036A (en) * | 2022-05-18 | 2022-08-16 | Oppo广东移动通信有限公司 | Lens and electronic equipment |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102169201A (en) * | 2011-06-03 | 2011-08-31 | 中国科学院西安光学精密机械研究所 | Sinusoidal phase plate and field depth expansion imaging system based on same |
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2019
- 2019-11-06 CN CN201911078119.XA patent/CN110927854A/en active Pending
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102169201A (en) * | 2011-06-03 | 2011-08-31 | 中国科学院西安光学精密机械研究所 | Sinusoidal phase plate and field depth expansion imaging system based on same |
Non-Patent Citations (1)
| Title |
|---|
| HONGBO XIE ET AL.: ""Athermalization of infrared optical system through wavefront coding"", 《OPTICS COMMUNICATION》 * |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114488524A (en) * | 2022-02-19 | 2022-05-13 | 复旦大学 | Wavefront coding imaging system based on high-order polynomial free-form surface phase plate |
| CN114488524B (en) * | 2022-02-19 | 2024-07-02 | 复旦大学 | Wavefront coding imaging system based on high-order polynomial free-form surface phase plate |
| CN114911036A (en) * | 2022-05-18 | 2022-08-16 | Oppo广东移动通信有限公司 | Lens and electronic equipment |
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