A method for measuring the angles of multiple targets using a single optical radar photo

Abstract

The present invention provides a method for measuring the angles of multiple targets with a single optical radar photo, comprising the following steps: ① adjusting the lens state: adjusting the focusing state of the imaging lens composition; ② obtaining parameters: obtaining the imaging geometric distance; ③ calculating the angle: calculating the angle of the point light source target relative to the main optical axis according to the imaging geometric distance. The present invention does not require multiple snapshots and can obtain the pitch angle and azimuth angle of multiple targets on the object focal plane through a single photo, and is particularly suitable for optical radars, such as passive radars, staring laser radars, and rotating line scanning laser radars.

Description

Technical Field

[0001] The invention relates to a method for measuring multi-target angles using a single optical radar photo. Background Art

[0002] With the development of optical radar technologies such as infrared passive radar, single photon detection technology, high-power pulsed laser, 1550 nm high-power laser, and laser line scanning, traditional microwave radar angle measurement methods, such as the MUSIC algorithm, require multiple snapshots of the signal to extract the direction of arrival (DOA) azimuth of multiple targets. This method, which is suitable for microwave radar to obtain target azimuth and elevation angles, is inconvenient for optical radar to obtain target azimuth and elevation angles. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a method for measuring the angles of multiple targets with a single optical radar photo. The method does not require multiple snapshots and can obtain the pitch angles and azimuth angles of multiple targets on the object focal plane through a single photo. It is particularly suitable for optical radars, such as passive radars, staring laser radars, and rotating line scanning laser radars.

[0004] The present invention is achieved through the following technical solutions.

[0005] The present invention provides a method for measuring multiple target angles using a single optical radar photo, comprising the following steps:

[0006] ① Adjust the lens state: adjust the focus state of the imaging lens composition;

[0007] ② Obtain parameters: obtain imaging geometric distance;

[0008] ③ Calculate the angle: According to the imaging geometric distance, calculate the angle of the point light source target relative to the main optical axis.

[0009] The imaging lens group includes an objective lens and an eyepiece.

[0010] The imaging geometric distance includes the distance between lenses, the height of the light spot imaged by the photosensitive plane array, the distance between the photosensitive plane array and the eyepiece, the focal length of the objective lens, and the focal length of the eyepiece.

[0011] The angle of the point light source target relative to the principal optical axis is calculated by calculating the distance P1 of the point light source target and the height H1 relative to the principal optical axis of the lens group, thereby obtaining the angle θ1 of the point light source target relative to the principal optical axis tanθ1=H1 / P1.

[0012] The distance P1 of the point light source target and the height H1 relative to the main optical axis of the lens group are obtained by the following formula:

[0013]

[0014]

[0015]

[0016] Wherein: L is the distance between lenses, P2 is the distance between the photosensitive plane array and the eyepiece, F1 is the focal length of the objective lens, F2 is the focal length of the eyepiece, P is the object focal length of the objective lens, and H2 is the height of the imaging light spot of the photosensitive plane array.

[0017] The focusing state is that the image formed by the lens group and the image-side focal plane fall on the photosensitive plane array.

[0018] Also includes the steps:

[0019] ④ Verify distance: Compare and verify the calculated distance of the point light source target with the distance of the point light source target obtained by the ranging radar.

[0020] The adjusting of the imaging lens group refers to adjusting the focal length.

[0021] The beneficial effect of the present invention is that the pitch angle and azimuth angle of multiple targets on the object focal plane can be obtained through a single photo without taking multiple snapshots, and is particularly suitable for optical radars, such as passive radars, staring laser radars, and rotating line scanning laser radars. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a cross-sectional view in the longitudinal direction through the main optical axis of the optical radar. DETAILED DESCRIPTION

[0023] The technical solution of the present invention is further described below, but the scope of protection claimed is not limited to the description.

[0024] Example 1

[0025] like Figure 1 As shown, the present invention provides a method for measuring multiple target angles using a single optical radar photo, comprising the following steps:

[0026] ① Adjust the lens state: adjust the focus state of the imaging lens composition;

[0027] ② Obtain parameters: obtain imaging geometric distance;

[0028] ③ Calculate the angle: According to the imaging geometric distance, calculate the angle of the point light source target relative to the main optical axis.

[0029] Example 2

[0030] Based on Embodiment 1, the imaging lens group includes an objective lens and an eyepiece lens.

[0031] Example 3

[0032] Based on Example 1, the imaging geometric distance includes the distance between lenses, the height of the light spot imaged by the photosensitive plane array, the distance between the photosensitive plane array and the eyepiece, the focal length of the objective lens, and the focal length of the eyepiece.

[0033] Example 4

[0034] Based on Example 1, the angle of the point light source target relative to the main optical axis is calculated by calculating the distance P1 of the point light source target and the height H1 relative to the main optical axis of the lens group, thereby obtaining the angle θ1 of the point light source target relative to the main optical axis tanθ1=H1 / P1.

[0035] Example 5

[0036] Based on Example 1, the distance P1 of the point light source target and the height H1 relative to the main optical axis of the lens group are obtained by the following formula:

[0037]

[0038]

[0039]

[0040] Wherein: L is the distance between lenses, P2 is the distance between the photosensitive plane array and the eyepiece, F1 is the focal length of the objective lens, F2 is the focal length of the eyepiece, P is the object focal length of the objective lens, and H2 is the height of the imaging light spot of the photosensitive plane array.

[0041] Example 6

[0042] Based on Example 1, the focusing state is that the image formed by the lens group and the image-side focal plane fall on the photosensitive plane array.

[0043] Example 7

[0044] Based on Example 1, the method further comprises the following steps:

[0045] ④ Verify distance: Compare and verify the calculated distance of the point light source target with the distance of the point light source target obtained by the ranging radar.

[0046] Example 8

[0047] Based on Example 1, adjusting the imaging lens group refers to adjusting the focal length.

[0048] Example 9

[0049] Based on the above embodiment, after the imaging lens group composed of the objective lens and the eyepiece is adjusted to the focusing state (the image formed by the lens group, the image focal plane, just falls on the photosensitive plane array, such as the EM-CCD or single photon avalanche diode SPAD array), based on the distance L between the two lenses, the height H2 of the imaging light spot of the photosensitive plane array, the distance P2 between the photosensitive plane array and the eyepiece, and the focal lengths F1 and F2 of the objective lens and the eyepiece, the distance P1 of the point light source target and the height H1 relative to the main optical axis of the lens group are calculated, thereby calculating the angle θ1=H1 / P1 of the point light source target relative to the main optical axis.

[0050] Here we take the longitudinal direction as an example. After the lens group focuses on the point light source target (focusing is often achieved by adjusting the distance L between the two lenses), the following formula is satisfied:

[0051]

[0052]

[0053]

[0054] These three linearly independent formulas are combined to form a set of equations. When the distance L between the two lenses, the height H2 of the imaging light spot of the photosensitive plane array, the distance P2 between the photosensitive plane array and the eyepiece, and the focal lengths F1 and F2 of the objective lens and eyepiece are known, the three unknowns of the object focal length P of the objective lens, the distance P1 of the point light source target relative to the lens group (optical radar), and the height H1 relative to the main optical axis of the lens group can be calculated. The angle of the point light source target relative to the main optical axis can be read as:

[0055]

[0056] The elevation angle of the point light source target can be read as:

[0057] θ=θ0+θ1

[0058] Here θ0 is the angle between the main optical axis and the horizontal line. A similar analysis of the horizontal direction can read out the azimuth angle of the point light source target. This method is also applicable to multiple targets on a plane perpendicular to the main optical axis with a relative lens group distance of P1. Therefore, this method can be used to read out the pitch angle and azimuth angle of multiple targets on a plane perpendicular to the main optical axis with a relative lens group distance of P1 based on a single photo. The distance of the point light source target relative to the optical radar calculated by this method can be verified and compared with the distance of the point light source target obtained by the ranging radar to improve the measurement accuracy. The cross-sectional area (size) of the target can be calculated based on the number of pixels occupied by the target in the image and the known conditions.

[0059] For a point light source target that is not on the object focal plane, it is necessary to focus the image again so that the point light source target is on the object focal plane, and then read out the pitch angle and azimuth angle of the point light source target.

[0060] Example 10

[0061] Based on the above embodiment, for a laser radar with single photon sensitivity based on a SPAD array, the SPAD array pixel is 256*320, of which 320 pixels are in the longitudinal direction, and the spacing between pixels is 50μm. The maximum laser divergence angle of the optical radar is 45°, and the cross-sectional area is 1m 2 The maximum target detection distance is 12km. The distance L between the objective lens and the eyepiece of the adjustable focus lens group is adjustable, the distance between the eyepiece and the SPAD array is P2, and the focal lengths F1 and F2 of the objective lens and the eyepiece are 300mm and 34.80mm respectively. Here we require that the point light source target on the upper edge of the optical radar field of view is imaged just on the upper edge pixel point. From these data, the corresponding relationship between the relative pitch angle of the point light source target and the main optical axis and the pixel point position on the plane at a distance of 12km can be calculated as shown in Table 1:

[0062] Table 1: Correspondence between the relative pitch angle of the point light source target and the main optical axis and the pixel position on the plane at a distance of 12 km from P1

[0063]

[0064]

Claims

1. A method for measuring the angles of multiple targets using a single optical radar photo, characterized in that: The steps include: ① Adjust the lens state: adjust the focus state of the imaging lens composition; ② Obtain parameters: obtain imaging geometric distance; ③ Calculate the angle: According to the imaging geometric distance, calculate the angle of the point light source target relative to the main optical axis; The imaging lens group includes an objective lens and an eyepiece; The imaging geometric distance includes the distance between lenses, the height of the light spot imaged by the photosensitive plane array, the distance between the photosensitive plane array and the eyepiece, the focal length of the objective lens, and the focal length of the eyepiece; The angle of the point light source target relative to the main optical axis is obtained by calculating the distance P1 of the point light source target and the height H1 relative to the main optical axis of the lens group, thereby obtaining the angle θ1 of the point light source target relative to the main optical axis tanθ1=H1 / P1; The distance P1 of the point light source target and the height H1 relative to the main optical axis of the lens group are obtained by the following formula: Wherein: L is the distance between lenses, P2 is the distance between the photosensitive plane array and the eyepiece, F1 is the focal length of the objective lens, F2 is the focal length of the eyepiece, P is the object focal length of the objective lens, and H2 is the height of the imaging light spot of the photosensitive plane array.

2. The optical radar single photo multi-target angle measurement method according to claim 1, characterized in that: The focusing state is that the image formed by the lens group and the image-side focal plane fall on the photosensitive plane array.

3. The optical radar single photo multi-target angle measurement method according to claim 1, characterized in that: Also includes the steps: ④ Verify distance: Compare and verify the calculated distance of the point light source target with the distance of the point light source target obtained by the ranging radar.

4. The optical radar single photo multi-target angle measurement method as claimed in claim 1, characterized in that: The adjusting of the imaging lens group refers to adjusting the focal length.

Images