Non-uniform correction sheet and correction method

Abstract

The invention provides a non-uniform correction sheet, and relates to the technical field of infrared thermal imaging, the non-uniform correction sheet comprises an infrared optical material and antireflection films uniformly plated on the upper and lower surfaces of the infrared optical material, and the infrared optical material adopts a random phase plate form or a micro lens array form. The non-uniformity correction sheet has extremely high transmittance and thus is basically not affected by internal heat radiation. Compared with a traditional separation blade correction mode, the method can be applied to a system which is highly closed, large in internal temperature change and high in temperature, and a good correction effect can still be achieved.

Description

Technical Field

[0001] The invention relates to the technical field of infrared thermal imaging, and in particular provides a non-uniform correction sheet and a correction method. Background Art

[0002] Infrared imaging equipment is affected by the drift of infrared detector response characteristics and changes in internal thermal radiation, and requires regular non-uniformity correction to ensure clear imaging.

[0003] At present, infrared imaging equipment generally uses a non-uniform correction sheet with high emissivity and uniform radiation to be inserted into the system as a reference for non-uniform correction. This method does not have a good effect on non-uniform correction because the radiation of the sheet does not reflect the radiation of the real background, and the residual reflection of the optical elements between the sheet insertion position and the outside scene cannot be taken into account. At the same time, since the sheet temperature changes with the internal temperature, its radiation characteristics will also change significantly, so this correction method has a poor correction effect. At the same time, as the internal temperature of the product rises, the non-uniformity of the image changes significantly.

[0004] In view of the above problems, the scene-based non-uniform correction method can be used to improve the non-uniformity of the image plane, but there are problems such as complex algorithm, high requirements for algorithm hardware, long convergence time, high requirements for scene changes, and the correction effect is greatly affected by external scene characteristics. Currently, it is rarely used in engineering. There is also a method of using defocus to perform non-uniform correction, but it has the problem of complex mechanism and poor correction effect. Summary of the invention

[0005] The purpose of the present application is to provide a non-uniform correction plate based on a uniform light diffuser to solve the above-mentioned problem.

[0006] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a non-uniform correction plate, which includes an infrared optical material and an anti-reflection film uniformly coated on the upper and lower surfaces of the infrared optical material, and the infrared optical material is in the form of a random phase plate or a microlens array.

[0007] The non-uniform correction plate provided by the present invention also has the following technical feature: the infrared optical material comprises a material selected from zinc sulfide, zinc selenide, silicon or germanium.

[0008] The non-uniform correction plate provided by the present invention also has the following technical features: when the infrared optical material is in the form of a random phase plate, the structural parameters of the non-uniform correction plate are used to simulate and design the optical system composed of the non-uniform correction plate and the infrared imaging system through simulation software.

[0009] The non-uniform correction film provided by the present invention also has the following technical features: during the simulation design, the image plane illumination uniformity and the geometric spot size at the image plane are used as evaluation functions, the image plane illumination uniformity is set to 1, the optimization target of the geometric spot size at the image plane is set to be equal to the diagonal size of the detector focal plane, and the image plane illumination is higher than 99%, and the geometric spot size at the image plane is larger than the diagonal size of the detector focal plane and smaller than 1.05 times the diagonal size of the detector focal plane as optimization termination conditions for simulation design.

[0010] The non-uniform correction sheet provided by the present invention also has the following technical features: when the infrared optical material is in the form of a microlens array, the structural parameters of the non-uniform correction sheet are used to simulate and design the optical system composed of the non-uniform correction sheet and the infrared imaging system through simulation software, and the simulation process optimizes the microlens focal length, microlens spacing and microlens layout until the image plane illumination is higher than 99% and the geometric spot size at the image plane is larger than the diagonal size of the detector focal plane and smaller than 1.05 times the diagonal size of the detector focal plane.

[0011] The non-uniform correction film provided by the present invention also has the following technical feature: the microlens array is arranged in a regular hexagonal close-packed form.

[0012] The non-uniform correction sheet provided by the present invention also has the following technical feature: the aperture of a single microlens in the microlens array is determined according to the convergence degree of the light beam reaching the microlens.

[0013] The non-uniform correction sheet provided by the present invention also has the technical feature that the viewing angle of the microlenses in the microlens array is greater than the maximum incident angle of light incident on the microlenses.

[0014] The non-uniform correction sheet provided by the present invention also has the following technical feature: the focal length-aperture ratio of the microlenses in the microlens array is determined by observing the geometric spot size of the light beam reaching the image plane after passing through a single microlens.

[0015] Another object of the present invention is to provide a non-uniformity correction method, the correction method is based on the non-uniformity correction sheet as described in any one of the above, comprising:

[0016] S1: Test and calibrate the effect of temperature change inside the infrared imaging system on image plane non-uniformity. When the image plane non-uniformity change exceeds 1‰, a non-uniformity correction is required.

[0017] S2: After the infrared imaging system is powered on and reaches the temperature, a non-uniformity correction sheet is inserted at the designed position to perform a non-uniformity correction and record the temperature recorded by the current temperature sensor;

[0018] S3: Read the temperature recorded by the temperature sensor in real time, and determine whether non-uniformity correction is needed based on table lookup or temperature difference judgment. When the time from the last non-uniformity correction exceeds the set value or non-uniformity correction is needed based on the temperature, insert the non-uniformity correction sheet to perform a non-uniformity correction.

[0019] Beneficial Effects

[0020] The non-uniform correction sheet provided by the present invention has extremely high transmittance and is therefore substantially unaffected by internal thermal radiation. Compared with the traditional baffle correction method, it can be used in highly enclosed systems with large internal temperature variations and high temperatures, and still achieves a better correction effect. DETAILED DESCRIPTION

[0021] The present application is further described in detail below in conjunction with examples, but it should be noted that these implementations are not limitations of the present application, and any equivalent transformations or substitutions in functions, methods, or structures made by ordinary technicians in the field based on these implementations are all within the scope of protection of the present application.

[0022] In the description of the embodiments of the present application, it needs to be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships, which are only for the convenience of describing the creation of the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the creation of the present application.

[0023] In addition, the terms "first", "second", "third", etc. 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. Thus, a feature defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the invention of this application, unless otherwise specified, the meaning of "plurality" is two or more.

[0024] The terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the invention of this application can be understood by specific circumstances.

[0025] The embodiment of the present application provides a non-uniform correction sheet, which is applied to an infrared imaging system. A temperature sensor is provided in the infrared imaging system to monitor the internal temperature of the infrared system in real time. The non-uniform correction sheet includes an infrared optical material and an anti-reflection film uniformly plated on the upper and lower surfaces of the infrared optical material. The infrared optical material is in the form of a random phase plate or a microlens array. The anti-reflection film is used to achieve high transmittance in the infrared band, and the transmittance is not less than 99%. The non-uniform correction sheet can be inserted into any position between the optical system and the detector according to the space constraints during use.

[0026] In some embodiments, the infrared optical material includes a material selected from zinc sulfide, zinc selenide, silicon or germanium. Other materials with high transmittance in the infrared band may also be used.

[0027] In some embodiments, when the infrared optical material is in the form of a random phase plate, the structural parameters of the non-uniform correction plate are used to simulate and design the optical system composed of the non-uniform correction plate and the infrared imaging system through simulation software. The simulation software can be commercial optical design simulation software such as CODEV, ZEMAX, TRACEPRO, etc. Through the phase plane design of the phase plate, the coherence of the incident light in all directions is significantly destroyed, so that the light beams of parallel light in all directions reaching the image plane evenly cover the entire image plane.

[0028] In some embodiments, during the simulation design, the image plane illumination uniformity and the geometric spot size at the image plane are used as evaluation functions, the image plane illumination uniformity is set to 1, the optimization target of the geometric spot size at the image plane is set to be equal to the diagonal size of the detector focal plane, and the image plane illumination is higher than 99%, and the geometric spot size at the image plane is larger than the diagonal size of the detector focal plane and less than 1.05 times the diagonal size of the detector focal plane as optimization termination conditions for simulation design.

[0029] In some embodiments, when the infrared optical material is in the form of a microlens array, the structural parameters of the non-uniform correction sheet are simulated and designed by simulation software for an optical system composed of the non-uniform correction sheet and the infrared imaging system, and the microlens focal length, microlens spacing and microlens layout are optimized during the simulation process until the image plane illumination is higher than 99% and the geometric spot size at the image plane is larger than the diagonal size of the detector focal plane and smaller than 1.05 times the diagonal size of the detector focal plane. The microlens array is composed of a plurality of closely arranged microlenses.

[0030] In some embodiments, the microlens array is arranged in a regular hexagonal close-packed form, that is, each microlens in each microlens array 5 is in a hexagonal form, and the microlenses are closely packed by sharing edges, and finally the microlens array forms a honeycomb shape, thereby reducing light leakage from the microlens gaps.

[0031] In some embodiments, the aperture selection of a single microlens in the microlens array is determined according to the degree of convergence of the light beam reaching the microlens. The specific aperture design method and process are as follows: insert the microlens array 5 into the infrared imaging system 2, and for each microlens in the microlens array 5, first give an initial value of the microlens aperture based on experience, and use commercial optical design simulation software such as CODEV, ZEMAX, TRACEPRO, etc. to simulate the optical system 3 composed of the microlens array 5 and the infrared imaging system 2, analyze the light spot 6 formed by each microlens at the image plane in each field of view direction, and compare it with the light spot 7 formed on the image plane when parallel light enters the microlens. If the ratio is greater than 1.01 or less than 0.99, reduce the size of the microlens. If the ratio is less than 1.01 and greater than 0.99, increase the size of the microlens until the ratio is equal to 1.01 or equal to 0.99 through multiple rounds of continuous changes in the size of the microlens.

[0032] In some embodiments, the viewing angle of a microlens in the microlens array is greater than the maximum incident angle of light incident on the microlens.

[0033] In some embodiments, the focal length-aperture ratio of the microlenses in the microlens array is determined by observing the geometric spot size of the light beam reaching the image plane after passing through a single microlens. In order to ensure the uniform light effect, the diameter of the light spot reaching the image plane should be 1 / 10 of the diagonal length of the image plane. The focal length-aperture ratio of the microlens is designed. The parameter design method and process are as follows: insert the microlens array 5 into the infrared imaging system 2, and use commercial optical design simulation software such as CODEV, ZEMAX, TRACEPRO, etc. to simulate the optical system 3 composed of the microlens array 5 and the infrared imaging system 2. In the design, the diameter of the light spot reaching the image plane after the light passes through the microlens is used as an evaluation function, and the diameter of the light spot reaching the image plane is set to 1 / 10 of the diagonal length of the image plane. After the above settings are completed, the optical design simulation software is automatically iterated and optimized.

[0034] In some embodiments, a non-uniformity correction method is provided. The correction method is based on the non-uniformity correction sheet as described in any one of the above items, and includes:

[0035] S1: Test and calibrate the effect of temperature change inside the infrared imaging system on image plane non-uniformity. When the image plane non-uniformity change exceeds 1‰, a non-uniformity correction is required.

[0036] S2: After the infrared imaging system is powered on and reaches the temperature, a non-uniformity correction sheet is inserted at the designed position to perform a non-uniformity correction and record the temperature recorded by the current temperature sensor;

[0037] S3: Read the temperature recorded by the temperature sensor in real time, and determine whether non-uniformity correction is needed based on table lookup or temperature difference judgment. When the time from the last non-uniformity correction exceeds the set value or non-uniformity correction is needed based on the temperature, insert the non-uniformity correction sheet to perform a non-uniformity correction.

[0038] In the above-mentioned embodiment, by inserting a non-uniform correction sheet based on a uniform light diffuser into the infrared imaging system, the real radiation from the outside world is detected in the image plane, thereby realizing a true scene-based non-uniform correction, and the correction effect is significantly better than the traditional sheet correction. The non-uniform correction sheet used is designed in conjunction with the optical system to achieve targeted optimization for different imaging devices, ensuring that it can be applied to various types of infrared sensors. The non-uniform correction cycle that provides a comprehensive internal temperature change and time interval ensures that the infrared imaging device always has good non-uniformity, and also reduces the problem of interruption of the infrared imaging device due to frequent non-uniform correction, which is relatively friendly to infrared detection equipment that requires continuous monitoring.

[0039] The above is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application. The above is only a preferred implementation of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and variations can be made without departing from the technical principles of the present application, and these improvements and variations should also be regarded as the protection scope of the present application.

Claims

1. A non-uniform correction sheet, characterized in that: The non-uniform correction plate comprises an infrared optical material and an anti-reflection film uniformly plated on the upper and lower surfaces of the infrared optical material. The infrared optical material is in the form of a random phase plate or a microlens array.

2. The non-uniform correction sheet according to claim 1, characterized in that: The infrared optical material includes a material selected from zinc sulfide, zinc selenide, silicon or germanium.

3. The non-uniform correction sheet according to claim 1, characterized in that: When the infrared optical material is in the form of a random phase plate, the structural parameters of the non-uniform correction plate are simulated and designed by simulation software for an optical system composed of the non-uniform correction plate and the infrared imaging system.

4. The non-uniform correction sheet according to claim 3, characterized in that: During the simulation design, the image plane illumination uniformity and the geometric spot size at the image plane are used as evaluation functions, the image plane illumination uniformity is set to 1, the optimization target of the geometric spot size at the image plane is set to be equal to the diagonal size of the detector focal plane, and the simulation design is performed with the image plane illumination being higher than 99% and the geometric spot size at the image plane being larger than the diagonal size of the detector focal plane and smaller than 1.05 times the diagonal size of the detector focal plane as optimization termination conditions.

5. The non-uniform correction sheet according to claim 1, characterized in that: When the infrared optical material is in the form of a microlens array, the structural parameters of the non-uniform correction sheet are simulated and designed by simulation software for an optical system composed of the non-uniform correction sheet and the infrared imaging system. During the simulation process, the microlens focal length, microlens spacing and microlens layout are optimized until the image plane illumination is higher than 99% and the geometric spot size at the image plane is larger than the diagonal size of the detector focal plane and smaller than 1.05 times the diagonal size of the detector focal plane.

6. The non-uniform correction sheet according to claim 5, characterized in that: The microlens array is arranged in a regular hexagonal close-packed form.

7. The non-uniform correction sheet according to claim 5, characterized in that: The aperture of a single microlens in the microlens array is determined according to the convergence degree of the light beam reaching the microlens.

8. The non-uniform correction sheet according to claim 5, characterized in that: The viewing angle of the microlenses in the microlens array is greater than the maximum incident angle of light incident on the microlenses.

9. The non-uniform correction sheet according to claim 5, characterized in that: The focal length-to-aperture ratio of the microlenses in the microlens array is determined by observing the geometric spot size of the light beam reaching the image plane after passing through a single microlens.

10. A non-uniform correction method, characterized in that: The correction method is based on the non-uniform correction sheet according to any one of claims 1 to 9, comprising: S1: Test and calibrate the effect of temperature change inside the infrared imaging system on the image plane non-uniformity. When the image plane non-uniformity change exceeds 1‰, a non-uniformity correction is required. S2: After the infrared imaging system is powered on and reaches the temperature, a non-uniformity correction sheet is inserted at the designed position to perform a non-uniformity correction and record the temperature recorded by the current temperature sensor; S3: Read the temperature recorded by the temperature sensor in real time, and determine whether non-uniformity correction is needed based on table lookup or temperature difference judgment. When the time from the last non-uniformity correction exceeds the set value or non-uniformity correction is needed based on the temperature, insert the non-uniformity correction sheet to perform a non-uniformity correction.