A method for evaluating area measurement errors of a multi-band photoelectric imaging system

Abstract

The application discloses a kind of multi-band photoelectric imaging system area measurement error evaluation methods.In the distance far from photoelectric imaging system working distance, array type is arranged with a certain interval multi-band radiation source, to be used as observation target to carry out photoelectric imaging system area measurement error evaluation test, to observe the projection area of target on the vertical plane of imaging system optical axis as target area true value, compared with the area measurement value of photoelectric imaging system target, evaluates system area measurement error.Can according to the characteristics that photoelectric imaging system working distance is far, observation area is big, adjusts radiation source layout interval, lays out large size target array, constructs and imaging system working distance matching measurable target area true value, carries out effective evaluation, target radiation source cost is low, test is easy to operate;Through reasonable layout multi-band array radiation source, can satisfy the area measurement error evaluation under the demand of multi-band multi-resolution detection, universality is very strong, has important significance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of target photoelectric characteristic measurement, and particularly relates to a multi-waveband photoelectric imaging system area measurement error evaluation method. BACKGROUND

[0002] Target area measurement evaluation is an important content of photoelectric imaging system data measurement and analysis, and is related to target index measurement such as a shielding area, and is also an important basis for non-cooperative target authenticity discrimination and target classification in the photoelectric detection field.

[0003] No literature has been found to elaborate on the photoelectric imaging system area measurement error evaluation method: Li Yong et al. pointed out that the target area can be converted by extracting the target radiation region, but did not elaborate on the system area measurement error evaluation; Li Xin et al. mentioned that the target area index can be determined based on the total number of pixel points N, but did not involve area index error evaluation (CN 118761211A); and the target shielding area evaluation patents (CN 116187036A and CN 115219460A) did not elaborate on the evaluation method of the system area measurement error.

[0004] Comparison between the theoretical true value and the measured value is an important evaluation method of measurement error. For photoelectric imaging system area measurement error evaluation, the theoretical area true value can be calculated based on the shape of the observed object, and then compared with the area measured value to calculate the error.

[0005] Under this idea, in order to realize the photoelectric imaging system area measurement error evaluation, a shape regular surface source can be introduced as an observation object to compare the target area true value with the measured value and obtain the area measurement error. However, the working distance of the photoelectric imaging system is far, the observation area range is large, it is difficult and costly to prepare a corresponding large-area size surface source, and the photoelectric imaging system often covers multiple working wavebands such as visible light, short wave, medium wave and long wave.

[0006] To solve the above problems, it is urgent to research an easy-to-implement, low-cost area measurement error evaluation method suitable for multi-waveband and long-distance working photoelectric imaging system, which provides an important reference for photoelectric system performance evaluation and detection application. SUMMARY

[0007] The application discloses a multi-waveband photoelectric imaging system area measurement error evaluation method, which solves the technical problems existing in the prior art. The evaluation method is easy to implement, low in cost, and suitable for multi-waveband and long-distance working photoelectric imaging system area measurement error evaluation, which provides an important reference for photoelectric system performance evaluation and detection application.

[0008] The application adopts the following technical scheme:

[0009] A multi-band photoelectric imaging system area measurement error evaluation method, at a far distance from the working distance of the photoelectric imaging system, a certain interval of multi-band radiation sources is arranged in an array, which is used as an observation target to carry out photoelectric imaging system area measurement error evaluation test, the projection area of the observation target on the vertical plane of the imaging system optical axis is taken as the true value of the target area, and the photoelectric imaging system target area measurement value is compared to evaluate the system area measurement error.

[0010] Further, the specific steps include the following steps:

[0011] (1) According to the field of view angle α (°) and the working distance R (m) of the photoelectric imaging system, the linear field of view L FOV (m) at the working distance R is determined; the calculation formula is as follows:

[0012] L FOV = 2R x tand (α / 2) (formula 1)

[0013] Wherein, tand is the tangent function;

[0014] (2) Select the test site;

[0015] (3) Determine the radiation source arrangement interval ΔL (m) and the array specification;

[0016] (4) Perform imaging test and record imaging data;

[0017] (5) Select the radiation source array target, calculate the photoelectric imaging system area measurement value S * ;

[0018] (6) Calculate the projection area S of the radiation source array target selected in step (5) on the vertical plane of the imaging system optical axis;

[0019] (7) Calculate the area measurement error ε:

[0020] ε = |S-S * | / S (formula 7);

[0021] (8) Select different radiation source array targets, repeat steps (5) to (7) 3 to 5 times, take the average value of the area measurement error as the final area measurement error of the photoelectric imaging system at this working wavelength;

[0022] (9) For multi-band photoelectric imaging system, combined with the imaging resolution of each working wavelength, select appropriate radiation source array target, repeat steps (5) to (8), get the area measurement error of each working wavelength of the photoelectric imaging system.

[0023] Further, the specific operation method of step (2) is as follows:

[0024] Select two ground surfaces or a ground surface and an inclined surface with a distance of not less than the working distance R(m); one of the ground surfaces is used to place the photoelectric imaging system to be evaluated, and the other ground surface or inclined surface is used to arrange the radiation sources; the ground surface or inclined surface for arranging the radiation sources has a width of not less than γL FOV (m), where γ is a proportionality coefficient of the radiation sources occupying the image plane in the horizontal direction, and γ is in the interval [1 / 3, 4 / 5]; let the inclination angle of the plane for arranging the radiation sources and the ground surface be β(°), and β ∈ [0°, 90°]; if the radiation sources are arranged on a horizontal ground surface, then β = 0°; if the radiation sources are arranged on a vertical lifting rod, then β = 90°; and if the radiation sources are arranged on an inclined surface, then β ∈ (0°, 90°).

[0025] Further, the specific operation method of step (3) is as follows:

[0026] The radiation sources are arranged in an n × n array, and n can be 3, 5, 7, 9, etc.; and the radiation source arrangement interval ΔL is determined according to the following formula:

[0027] ΔL = γ × L FOV / (n-1) (Formula 2)

[0028] For a multi-band imaging photoelectric system, the linear field of view L FOV of each band at the working distance R is integrated, the radiation source array specification n is reasonably selected, and the radiation source arrangement interval ΔL is determined, so that the area measurement error evaluation under the multi-band multi-resolution detection requirement can be met; if the linear field of view L FOV of different working bands of the multi-band imaging photoelectric system is different, the corresponding γ value will also be different, and it is necessary to avoid the case that the γ value is too large or too small; γ is in the interval [1 / 3, 4 / 5], when the γ value is greater than 4 / 5, it is considered that the γ value is too large, and when the γ value is less than 1 / 3, it is considered that the γ value is too small.

[0029] Further, the specific steps of step (4) are as follows:

[0030] (4.1) According to the radiation source arrangement interval and array specification determined in step (3), arrange the radiation source array in the test site selected in step (2), and erect the photoelectric imaging system;

[0031] (4.2) Set the working field of view angle of the photoelectric imaging system, adjust the system turntable or tripod support pitch angle θ(°), so that the photoelectric imaging system is in clear imaging with the radiation sources, ensure that the same row of radiation sources is located on the same row of image planes of the system, and save the imaging data, where θ is based on the horizontal plane, and θ ∈ [-90°, 90°].

[0032] Further, the specific steps of step (5) are as follows:

[0033] (5.1) In the single waveband image plane of the photoelectric imaging system, select a suitable m x m radiation source array target, where m≤n;

[0034] (5.2) Record the four imaging positions of the m x m radiation source array target in the image plane of the radiation source, i.e. the upper left (X LT ,Y LT ), the upper right (X RT ,Y RT ), the lower left (X LD ,Y LD ), and the lower right (X RD ,Y RD );

[0035] (5.3) Calculate the number of image elements N of the radiation source in the image plane of the photoelectric imaging system, and the calculation formula is as follows:

[0036] N = {(X RT -X LT ) + (X RD -X LD )} x (Y LD -Y LT ) / 2 (Formula 3);

[0037] (5.4) Calculate the area measurement value S * (m 2 ) of the region surrounded by the edge line of the radiation source array target selected in step (5.1) in the photoelectric imaging system:

[0038]

[0039] Further, the specific steps of step (6) are as follows:

[0040] (6.1) Calculate the area S0(m 2 ) of the radiation source array target in the layout plane:

[0041] S0 = ((m-1) x ΔL) 2 = (γ x L FOV x (m-1) / (n-1)) 2 (Formula 5);

[0042] (6.2) Calculate the projection area S(m 2 ) of the radiation source array target in the vertical plane of the imaging system optical axis:

[0043] S = S0 x cosd(θ+β) (Formula 6)

[0044] where cosd is the cosine function.

[0045] The beneficial effects of the present application are that according to the characteristics of long working distance and large observation area of the photoelectric imaging system, the radiation source layout interval can be adjusted, the large-size target array can be laid out, the measurable target area true value matching the working distance of the imaging system can be constructed, and the effective evaluation can be carried out, and the target radiation source cost is low and the test is easy to operate; through reasonable layout of the multi-band n*n array radiation source, the area measurement error evaluation under the multi-band multi-resolution detection demand can be met, the universality is very strong, and important reference basis can be provided for photoelectric system performance evaluation and detection application. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 It is a test principle block diagram of the area measurement error evaluation of the multi-band long-distance photoelectric imaging system of the present application. In the figure, 1 represents the photoelectric imaging system to be evaluated; 2 is the ground on which the photoelectric imaging system is placed; 3 is a multi-band radiation source, which is apart from the photoelectric imaging system by R(m); 4 is an inclined plane on which the radiation source array is placed, which can form a certain inclination angle β with the ground; 5 is the direction of the optical axis of the photoelectric imaging system to be evaluated, which can form a certain inclination angle θ with the ground; 6 is the projection position of the upper left corner radiation source of the radiation source array on the vertical plane of the optical axis of the photoelectric system at this place, which corresponds to the upper left (X LT ,Y LT ) imaging position of the radiation source array target on the image plane; 7 is the projection position of the upper right corner radiation source of the radiation source array on the vertical plane of the optical axis of the photoelectric system at this place, which corresponds to the upper right (X RT ,Y RT ) imaging position of the radiation source array target on the image plane; 8 is the projection position of the lower left corner radiation source of the radiation source array on the vertical plane of the optical axis of the photoelectric system at this place, which corresponds to the lower left (X LD ,Y LD ) imaging position of the radiation source array target on the image plane; 9 is the projection position of the lower right corner radiation source of the radiation source array on the vertical plane of the optical axis of the photoelectric system at this place, which corresponds to the lower right (X RD ,Y RD ) imaging position of the radiation source array target on the image plane.

[0047] Figure 2 The multi-band photoelectric imaging system is imaged on the radiation source array target, and from left to right, the imaging diagrams are visible light imaging diagram (night imaging), short-wave imaging diagram, medium-wave imaging diagram and long-wave imaging diagram. In the figure, the radiation source array specification is 3*5. Through the imaging experiment on a certain specification of the radiation source array target, the multi-band radiation source array target image as shown in the figure is obtained, and by using the method of the present application, the area measurement error of each working band of the multi-band photoelectric imaging system can be evaluated. DETAILED DESCRIPTION

[0048] The specific implementation work of the present application will be further described in detail in combination with the drawings:

[0049] The application provides a multi-band photoelectric imaging system area measurement error evaluation method, at a far distance of a working distance of a photoelectric imaging system, a plurality of multi-band radiation sources arranged at intervals are arranged in an array, and the plurality of multi-band radiation sources are used as observation targets to carry out a photoelectric imaging system area measurement error evaluation test, a projection area of the observation targets on a vertical plane of an optical axis of the photoelectric imaging system is used as a target area true value, and the target area true value is compared with a photoelectric imaging system target area measurement value to evaluate system area measurement error.

[0050] Figure 1 The application provides a multi-band photoelectric imaging system area measurement error evaluation method, at a far distance of a working distance of a photoelectric imaging system, a plurality of multi-band radiation sources arranged at intervals are arranged in an array, and the plurality of multi-band radiation sources are used as observation targets to carry out a photoelectric imaging system area measurement error evaluation test, a projection area of the observation targets on a vertical plane of an optical axis of the photoelectric imaging system is used as a target area true value, and the target area true value is compared with a photoelectric imaging system target area measurement value to evaluate system area measurement error.

[0051] (1) According to a field of view angle α (°) and a working distance R (m) of the photoelectric imaging system, a linear field of view L FOV (m) of the photoelectric imaging system at the working distance R is determined.

[0052] L FOV = 2R × tand (α / 2) (Formula 1)

[0053] Wherein, tand is a tangent function.

[0054] (2) A test site is selected. The specific operation method is as follows:

[0055] Two ground surfaces or a ground surface and an inclined surface with a distance not less than the working distance R (m) are selected as the test site. One of the ground surfaces is used to place the photoelectric imaging system to be evaluated, and the other ground surface or the inclined surface is used to arrange the radiation sources. The width of the ground surface or the inclined surface used to arrange the radiation sources is not less than γL FOV (m), wherein γ is a proportion coefficient of the radiation sources occupying an image plane in the horizontal direction, and is taken as a value in the interval [1 / 3, 4 / 5]. The inclination angle of the radiation source arrangement plane and the ground surface is denoted as β (°), and β ∈ [0°, 90°]. If the radiation sources are arranged on a horizontal ground surface, β = 0°. If the radiation sources are arranged on a vertical ground surface, β = 90°. If the radiation sources are arranged on an inclined surface, β ∈ (0°, 90°).

[0056] (3) The radiation source arrangement interval ΔL (m) and the array specification are determined. The specific operation method is as follows:

[0057] The radiation sources are arranged in an n × n array, and n can be 3, 5, 7, 9, etc. The radiation source arrangement interval ΔL is confirmed according to the following formula:

[0058] ΔL = γ × L FOV / (n-1) (Formula 2)

[0059] For a multi-band imaging photoelectric system, the linear field of view LFOV , the radiation source array specification n is reasonably selected, and the radiation source layout interval AL is determined, so that the area measurement error evaluation under the multi-waveband multi-resolution detection requirement can be met. If the line fields of view L FOV are different, the corresponding γ values are also different, and the cases of too large or too small γ values should be avoided; γ is taken in the interval [1 / 3, 4 / 5], and when the γ value is greater than 4 / 5, it is considered that the γ value is too large, and when the γ value is less than 1 / 3, it is considered that the γ value is too small.

[0060] (4) Imaging test is performed, and imaging data is recorded. The specific steps are as follows:

[0061] (4.1) According to the radiation source layout interval and array specification determined in step (3), the radiation source array is laid out in the test site selected in step (2), and the photoelectric imaging system is erected;

[0062] (4.2) The working field of view angle of the photoelectric imaging system is set, the system turntable or tripod support pitch angle θ (°) is adjusted, the photoelectric imaging system is aligned to clearly image the radiation source, it is ensured that the same row of radiation sources are located on the same row of image planes of the system, and the imaging data is saved, wherein θ is based on the horizontal plane, and θ ∈ [-90°, 90°].

[0063] (5) The area measurement value S * of the photoelectric imaging system is calculated. The specific steps are as follows:

[0064] (5.1) In the n×n radiation source array image on the single waveband image plane of the photoelectric imaging system, a suitable m×m radiation source array target is selected, wherein m≤n;

[0065] (5.2) The left upper (X LT ,Y LT ), right upper (X RT ,Y RT ), left lower (X LD ,Y LD ), and right lower (X RD ,Y RD ) imaging positions of the m×m radiation source array target on the radiation source image plane are recorded;

[0066] (5.3) The number of image elements N of the radiation source on the image plane of the photoelectric imaging system is calculated, and the calculation formula is as follows:

[0067] N = {(X RT -X LT ) + (X RD -X LD )} × (Y LD -Y LT ) / 2 (Formula 3);

[0068] (5.4) Calculate the area measurement value S of the region surrounded by the edge line of the selected radiation source array target in step (5.1) by the photoelectric imaging system * (m 2 ):

[0069]

[0070] (6) Calculate the projected area S of the selected radiation source array target in step (5.1) on the vertical plane of the optical axis of the imaging system. The specific steps are as follows:

[0071] (6.1) Calculate the area S0(m 2 ) of the radiation source array target on the layout plane:

[0072] S0= ((m-1) x ΔL) 2 = (γ x L FOV x (m-1) / (n-1)) 2 (Formula 5);

[0073] (6.2) Calculate the projected area S(m 2 ) of the radiation source array target on the vertical plane of the optical axis of the imaging system:

[0074] S = S0 x cosd(θ + β) (Formula 6)

[0075] Where cosd is the cosine function.

[0076] (7) Calculate the area measurement error ε.

[0077] ε = |S - S * | / S (Formula 7).

[0078] (8) Select different radiation source array targets, repeat steps (5) to (7) 3 to 5 times, take the average value of the area measurement error as the final area measurement error of the photoelectric imaging system in the working waveband.

[0079] (9) For a multi-waveband photoelectric imaging system, combined with the imaging resolution of each working waveband, select appropriate radiation source array targets, repeat steps (5) to (8), and obtain the area measurement error of the photoelectric imaging system in each working waveband.

Claims

1. A method for evaluating area measurement errors in a multi-band electro-optical imaging system, the method comprising: At a long distance from the working distance of the photoelectric imaging system, a plurality of multi-band radiation sources arranged in an array with a certain interval are used as observation targets to carry out area measurement error evaluation tests of the photoelectric imaging system, the projected area of the observation target on the vertical plane of the optical axis of the imaging system is taken as the true value of the target area, and the area measurement value of the photoelectric imaging system is compared to evaluate the area measurement error of the system; Specifically comprising the following steps: (1) According to the field angle α of the photoelectric imaging system and the working distance R, determine its linear field of view L at the working distance R FOV ; The calculation formula is as follows: L FOV = 2R x tand(a / 2) (Equation 1) Where tand is the tangent function; (2) Select a test site; (3) Determine the radiation source arrangement interval ΔL and the array specification; (4) Perform imaging tests and record imaging data; (5) Selecting the radiation source array target, calculating the area measurement value S of the photoelectric imaging system * ; (6) Calculate the projected area S of the radiation source array target selected in step (5) on the vertical plane of the optical axis of the imaging system; (7) Calculate the area measurement error ε: ε = |S - S * | / S (Equation 7); (8) Select different radiation source array targets, repeat steps (5) to (7) 3 to 5 times, take the average of the area measurement errors, and take it as the final area measurement error of the photoelectric imaging system for the working waveband; (9) For a multi-band photoelectric imaging system, select appropriate radiation source array targets according to the imaging resolution of each working waveband, and repeat steps (5) to (8) to obtain the area measurement error of each working waveband of the photoelectric imaging system.

2. The method of claim 1, wherein: The specific operation method of step (2) is as follows: Select two test sites with a distance not less than the working distance R; one of which is used to place the evaluated photoelectric imaging system, and the other is used to lay the radiation source; the width of the ground or slope used to lay the radiation source is not less than γL FOV wherein γ is the proportionality coefficient of the radiation source occupying the image plane in the horizontal direction, and γ ∈ [1 / 3, 4 / 5]; let the inclination angle of the radiation source laying plane and the ground be β, β ∈ [0°, 90°], if the radiation source is laid on the horizontal ground, then β = 0°; if the radiation source is laid on the vertical ground lifting rod, then β = 90°, if the radiation source is laid on the slope, then β ∈ (0°, 90°).

3. The method of claim 1, wherein: The specific operation method of step (3) is as follows: The radiation sources are arranged in an n×n array, n can be 3, 5, 7, 9, etc., and the radiation source arrangement interval ΔL is determined according to the following formula: ΔL = γ x L FOV (n-1) (Equation 2) For a multi-band imaging optoelectronic system, the combined linear field of view L at the working distance R of each band is considered. FOV By rationally selecting the radiation source array specification n and determining the radiation source placement interval ΔL, the area measurement error assessment under the requirements of multi-band and multi-resolution detection can be satisfied; if the line field of view L of the multi-band imaging optoelectronic system in different working bands is different... FOV Different values ​​will result in different γ values, and it is necessary to avoid γ values ​​that are too large or too small. γ takes values ​​in the range of [1 / 3, 4 / 5]. When the γ value is greater than 4 / 5, it is considered that the γ value is too large, and when the γ value is less than 1 / 3, it is considered that the γ value is too small.

4. The method of claim 1, wherein: The specific steps of step (4) are as follows: (4.1) According to the radiation source arrangement interval and array specification determined in step (3), arrange the radiation source array in the test site selected in step (2), and set up the photoelectric imaging system; (4.2) Set the working field angle of the photoelectric imaging system, adjust the pitch angle θ of the system turntable or tripod support, make the photoelectric imaging system focus on the radiation source, ensure that the same row of radiation sources are located on the same row of image planes, save the imaging data, and θ is based on the horizontal plane, θ ∈ [-90°, 90°].

5. The method of claim 1, wherein: The specific steps of step (5) are as follows: (5.1) In the n×n radiation source array image on the single waveband image plane of the photoelectric imaging system, select a suitable m×m radiation source array target, where m ≤ n; (5.2) recording the four imaging positions of the m x m radiation source array target upper left (X LT ,Y LT ), upper right (X RT ,Y RT ), lower left (X LD ,Y LD ), lower right (X RD ,Y RD ) in the radiation source image plane; (5.3) Calculate the number of pixels N of the radiation source on the image plane of the photoelectric imaging system, and the calculation formula is as follows: N = {(X RT - X LT )+(X RD - X LD )} x (Y LD - Y LT ) / 2 (Equation 3); (5.4) calculating the area measure S of the region enclosed by the edge line of the array of radiation sources selected in step (5.1) by the opto-electronic imaging system * :

6. The method of claim 1, wherein: The specific steps of step (6) are as follows: (6.1) Calculate the area S0 of the radiation source array target on the arrangement plane: S0 = ((m - 1) x ΔL) 2 = (γ x L FOV x (m - 1) / (n - 1)) 2 (Equation 5); (6.2) Calculate the projected area S of the radiation source array target on the vertical plane of the optical axis of the imaging system: S = S0×cosd(θ+β) (Formula 6) Where cosd is the cosine function.

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