A laser range finder collimation system employing a CCD matrix

Abstract

The present application relates to the technical field of optical axis calibration, and particularly relates to a laser range finder collimation system using a CCD matrix, which comprises a hollow corner reflector, an off-axis parabolic metal reflector, a rotating reflector, a first diagonal beam-splitting reflector, a second diagonal beam-splitting reflector, a laser radiation imaging instrument, a CCD matrix, a computer and an LED emitter. The present application solves the problem of high-precision alignment of the laser emission channel and the laser receiving channel of the laser range finder, and can be applied to the optical axis calibration of most photoelectric devices and lasers, quickly aligns the channels in different spectral ranges, and can use continuous and pulsed lasers for operation. The present application can solve the problem of spatial position coordination of focusing on a single component and the channel axis, and can realize optical axis calibration through the configuration of the hollow corner reflector and the rotating reflector, and can realize optical axis offset visualization and quantification through the cooperation of the laser radiation imaging instrument and the CCD matrix, thereby simplifying the collimation process and improving the precision of the device collimation axis.

Description

Technical Field

[0001] This invention relates to the field of optical axis calibration technology, and in particular to a laser rangefinder collimation system using a CCD matrix. Background Technology

[0002] Laser rangefinders measure distance using laser beams. Due to their advantages such as high angular resolution, high measurement accuracy, strong anti-interference capability, ease of operation, and small size, they are increasingly used in industrial measurement and military fields. Because of the functional and specialized nature of laser rangefinder applications, the requirements for ranging accuracy and lateral resolution are extremely stringent. The measurement accuracy and effective range of a laser rangefinder are primarily ensured by the parallelism of the three optical axes: the laser emission axis, the laser receiving axis, and the aiming axis. Therefore, the collimation process of a laser rangefinder mainly involves calibrating the parallelism of the system's three optical axes.

[0003] Currently, there are two main types of systems for calibrating the three optical axes of laser rangefinders: one using an eccentric ring (frame) structure, and the other using a double optical wedge structure. The former moves optical elements perpendicular to the optical axis to change the direction of that axis, making it parallel to the other axes. However, this method has drawbacks such as large component size and high calibration difficulty. The latter adjusts the relative rotation angle of the double optical wedge system to change the laser emission direction, thereby achieving three-axis parallelism calibration. Traditional detection and calibration methods include collimator methods and concave mirror reflection methods. However, these methods can only qualitatively determine the deviation in three-axis parallelism, and cannot quantitatively analyze the specific offset angle for more precise adjustments. Traditional detection and calibration methods often require trained and experienced professionals, and the process is cumbersome. In industrial measurements, real-time detection is often required, leading to low efficiency in detection and calibration, and the reliability of the device cannot be guaranteed on time. Summary of the Invention

[0004] This invention provides a laser rangefinder collimation system using a CCD matrix, which can quantify the degree of laser optical axis offset and thereby perform visual calibration of the parallelism of the three optical axes, simplifying the calibration process and reducing the difficulty of operation.

[0005] To achieve the objectives of this invention, the technical solution adopted is: a laser rangefinder collimation system using a CCD matrix, comprising a hollow corner reflector, an off-axis parabolic metal mirror, a rotating reflector, a first diagonal beam-splitting mirror, a second diagonal beam-splitting mirror, a laser radiation imaging device, a CCD matrix, a computer, and an LED emitter. The off-axis parabolic metal mirror, rotating reflector, first diagonal beam-splitting mirror, second diagonal beam-splitting mirror, laser radiation imaging device, and CCD matrix constitute the aiming optical axis. The hollow corner reflector is used for adjustment. The angular deviation of the laser receiving optical axis is addressed by an off-axis parabolic metal reflector used to connect the laser receiving optical axis to the aiming optical axis, a rotating reflector used to adjust the positional deviation of the laser receiving optical axis, a first diagonal beam-splitting reflector used to reflect the light emitted by the LED emitter into the aiming optical axis, and the laser receiving optical axis is calibrated by the off-axis parabolic metal reflector; the second diagonal beam-splitting reflector used to reflect the light in the visible light band emitted by the laser radiation imaging instrument to the CCD matrix, and the CCD matrix, in conjunction with the computer, realizes the visualization and quantization of the laser beam optical axis.

[0006] As an optimized embodiment of the present invention, the laser radiation imaging device is located on the focal plane of the off-axis parabolic metal mirror, and the center point of the laser radiation imaging device is conjugate with the position of the LED emitter.

[0007] As an optimized embodiment of the present invention, the collimation system of the laser rangefinder using a CCD matrix further includes a protective filter and a cylindrical prism. The protective filter and the cylindrical prism are sequentially arranged between the second diagonal beam-splitting mirror and the CCD matrix. The protective filter is used to prevent stray light from being generated in front of the CCD matrix, and the cylindrical prism is used to focus the light passing through the protective filter at the center of the CCD matrix.

[0008] As an optimized embodiment of the present invention, the collimation system of the laser rangefinder using a CCD matrix further includes an aperture, which is positioned in front of the LED emitter and is used to adjust the illuminance and depth of field.

[0009] As an optimized solution of the present invention, the collimation system of the laser rangefinder using a CCD matrix further includes an infrared spectral emitter. The LED emitter and the infrared spectral emitter serve as the light source for the collimated beam, forming a collimated optical axis. After being reflected by an off-axis parabolic metal mirror, the collimated optical axis is parallel to the collimated axis of the laser receiving optical axis.

[0010] As an optimized embodiment of the present invention, the laser optical axis azimuth angle formed by the laser rangefinder is:

[0011]

[0012] In Formula 1: θ b y represents the divergence of the laser beam. sf represents the size of the laser spot in a horizontal direction within the focal plane of an off-axis parabolic metal mirror. p Let be the focal length of the off-axis parabolic metal mirror.

[0013] As an optimized embodiment of the present invention, the laser beam diverges from zero position along the x-axis by an angle θ. x,b The laser beam diverges from zero on the y-axis at an angle θ. y,b They are respectively:

[0014]

[0015]

[0016] In formulas 2 and 3, x s It is the x-coordinate of the laser spot energy center on the focal plane of the laser radiation imaging instrument along the x-axis; y s It is the y-coordinate of the laser spot energy center on the focal plane of the laser radiation imaging instrument.

[0017] The present invention has the following positive effects: 1) In order to simplify the operation process and reduce the error caused by unnecessary component movement, the present invention installs a hollow corner reflector and a rotating reflector on the laser receiving optical axis and the aiming optical axis of the collimation system respectively to control the conjugate of the laser receiving optical axis and the aiming optical axis.

[0018] 2) To detect the parallelism of the three optical axes of the laser rangefinder and to perform optical axis calibration using mechanical devices such as reflectors, this invention introduces a CCD matrix and a matching computer digital image processing system. The center of the CCD matrix is ​​set as the coordinate zero point. Digital images acquired by the CCD matrix are transmitted to the computer to obtain the offset of the laser spot, from which the deviation of the optical axis can be calculated.

[0019] 3) To ensure operator safety, the laser in the collimation system uses a safe radiation wavelength of 1.54 μm. However, due to the limited spectral sensitivity of some CCD matrices to the 1.1 μm long wavelength range, the alignment process between the CCD matrix and the laser beam has a relatively large error. To address the current problem of CCD matrices not easily aligning perfectly with the laser beam, this invention introduces a laser radiation imaging device to replace the CCD in displaying the laser spot, thus visualizing the optical axis calibration process and ensuring the performance of the CCD matrix.

[0020] 4) This invention successfully solves the problem of high-precision (accuracy up to 5-10 arcseconds) alignment of the collimation axes of the laser emission and receiving channels in laser rangefinders. Furthermore, this collimation system is applicable to the optical axis calibration of most optoelectronic devices and lasers, enabling rapid alignment of channels across different spectral ranges, and can be operated using both continuous and pulsed lasers. When calibrating optoelectronic devices, this invention solves the problem of focusing on individual components and coordinating the spatial position of the channel axes. This invention uses hollow corner reflectors and rotating reflectors for optical axis calibration, and, in conjunction with a laser radiation imaging system and a CCD matrix, achieves visualization and quantification of optical axis offset, simplifying the collimation process and improving the accuracy of the device's collimation axis and the calibration efficiency for operators. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0023] Figure 2 This is a schematic diagram showing the result of the image processing algorithm error of the present invention with the number of snapshot experiments.

[0024] The components include: 1. Laser receiving optical axis; 2. Hollow corner reflector; 3. Off-axis parabolic metal reflector; 4. Rotating reflector; 5. First diagonal beam splitter reflector; 6. Second diagonal beam splitter reflector; 7. Laser radiation imager; 8. Protective filter; 9. Cylindrical prism; 10. CCD matrix; 11. Computer; 12. Aperture; 13. LED emitter; and 14. Infrared spectral emitter. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0026] Figure 1This is a schematic diagram of a collimation system for a laser rangefinder using a CCD matrix. It includes a hollow corner reflector 2, an off-axis parabolic metal mirror 3, a rotating reflector 4, a first diagonal beam-splitting mirror 5, a second diagonal beam-splitting mirror 6, a laser radiation imager 7, a protective filter 8, a cylindrical prism 9, a CCD matrix 10, a computer 11, an aperture 12, an LED emitter 13, and an infrared spectral emitter 14. The off-axis parabolic metal mirror 3, rotating reflector 4, first diagonal beam-splitting mirror 5, second diagonal beam-splitting mirror 6, laser radiation imager 7, protective filter 8, cylindrical prism 9, and CCD matrix 10 constitute the aiming optical axis.

[0027] Hollow corner reflector 2 and rotating reflector 4 can be used to adjust the deviation angle and position of the laser receiving optical axis 1. Rotating reflector 4 connects the laser emitting optical axis with the collimating optical axis. Hollow corner reflector 2 has a diameter of 50.8 mm and an accuracy error of less than 1″. Off-axis parabolic metal mirror 3 has an optical path of 306 mm and a focal length of 1540 mm. Off-axis parabolic metal mirror 3 is used to connect the laser receiving optical axis 1 of different channels to the aiming optical axis. Through the reflection effect of off-axis parabolic metal mirror 3, the space utilization of the collimation system is improved and the volume is reduced.

[0028] The first diagonal beam splitter 5 and the second diagonal beam splitter 6 are used to split the incident beam into two beams, one transmitted and one reflected, with a certain intensity ratio. The first diagonal beam splitter 5 is used to reflect the light emitted by the LED emitter 13 into the aiming optical axis, and then calibrate the laser receiving optical axis 1 via the off-axis parabolic metal reflector 3; the second diagonal beam splitter 6 is used to reflect the light in the visible light band emitted by the laser radiation imaging instrument 7 to the CCD matrix 10.

[0029] The laser radiation imager 7 is a device that can display an image of a laser beam and emit visible light under the influence of laser radiation. It is set on the focal plane of the off-axis parabolic metal mirror 3 and is used to convert the laser light into a CCD matrix 10 for visualization and quantization. The laser radiation imager 7 is extremely sensitive to the safe radiation wavelength of 1.54 μm and has an emission band of 510–570 nm.

[0030] The protective filter 8 utilizes the principle of light interference to achieve spectral transmission, which is equivalent to a pre-filter, preventing stray light from being generated in front of the CCD matrix 10 and thus protecting the CCD matrix 10.

[0031] The cylindrical prism 9 changes the direction of light propagation through the protective filter 8, focusing it at the center of the CCD matrix 10.

[0032] The CCD matrix 10 is used to collect light signals focused on its center and transmit them to the computer 11 for display and recording in the form of digital images. The CCD matrix 10 has a resolution of 782×582 pixels and an element size of 8.3×8.3μm2.

[0033] The LED emitter 13 and the infrared spectral emitter 14 serve as the light source for the collimated beam, forming a collimated beam axis that passes through the off-axis parabolic metal reflector 3 and is parallel to the collimated axis of the laser receiving optical axis 1. The aperture 12 is used to adjust the illuminance and depth of field to optimize the imaging effect of the light source. The infrared spectral emitter 14 is adaptively set according to the rotation angle of the rotating reflector 4.

[0034] First, the laser radiation imager 7 is positioned on the focal plane of the off-axis parabolic metal mirror 3, with its center point conjugate to the positions of the LED emitter 13 and the infrared spectral emitter 14, which serve as light sources. The center of the CCD matrix 10 is set as the zero point. During the alignment process of the laser receiving optical axis 1, the laser channel (laser receiving optical axis 1) can be rotated using components such as the hollow corner reflector 2 to set the laser spot image on the matrix to the zero coordinate position.

[0035] The laser emitted by the laser emitter of the laser rangefinder is incident on an off-axis parabolic metal mirror, reflected, and focused onto the focal plane of the laser radiation imager 7. Under the influence of the laser radiation, the laser radiation imager 7 generates emitted light in the visible light spectrum, which is recorded by the CCD matrix 10 connected to the computer 11. Image processing, size, and position estimation are performed on the computer 11. The size of the image focused on the laser radiation imager 10 characterizes the divergence of the laser beam, and its actual coordinates describe the angular deviation between the laser beam axis and the collimating optical axis. This angular deviation can be reduced to an acceptable value by rotating the laser emitter during alignment.

[0036] The collimation axis of photoelectric devices such as laser rangefinders that receive light emission should be parallel to the collimation optical axis from the off-axis parabolic metal mirror 3. The collimated beam can be formed by various light sources in the system. In this collimation system, an infrared spectral emitter 14 and an LED emitter 13 are respectively positioned at the focal point of the off-axis parabolic metal mirror 3, which is conjugate with the rotating reflector 4 and the diagonal beam-splitting mirror, as emission light sources. The angular orientation of the collimation optical axis coincides with the axis passing through the focal point and node of the off-axis parabolic metal mirror 3, and the light source is activated within a specified time. After reflection from the off-axis parabolic metal mirror 3, each light source reflected from the off-axis parabolic metal mirror 3 emits a signal as a signal source on the laser emission optical axis. The angle θ between the beam emitted by the light source and the collimation optical axis can be expressed as:

[0037]

[0038] Where: y is the linear dimension from the light source to the collimating optical axis, f p Let f be the focal length of the parabolic reflector. When y = 0.1–0.2 mm, f p When the radius is 1540mm, θ can be obtained from the formula as 0.2″~0.400″. For many laser-guided tasks, this value is comparable to the angle of a real object.

[0039] The light source image is recorded at the receiving nodes of the optoelectronic device (diagonal beam-splitting mirror and off-axis parabolic metal mirror). The image is then aligned with the collimating optical axis of the collimating system using diagonal beam-splitting mirrors (first diagonal beam-splitting mirror 5 and second diagonal beam-splitting mirror 6). A laser radiation imaging device 7 displays the image on the collimating optical axis of the laser channel (laser receiving optical axis 1) to align the nodes. This process is repeated for all receiving nodes until the collimating optical axes of all nodes are parallel to each other.

[0040] In a laser rangefinder collimation system using a CCD matrix, the collimating optical axis is selected as the reference axis, and the laser channel is parallel to the collimating optical axis. The laser rangefinder is mounted on a bracket, and its positioning method involves first placing the LED emitter 13, observing the image in the laser radiation imager 7, and finally positioning the light source image onto the collimating optical axis of the laser channel. Next, a diagonal beam-splitting mirror is placed in the optical path using a simulated laser beam light source. The simulated laser beam light source can generate short light pulses of 10–30 ns at the ranging emission wavelength. The receiving channel (laser receiving optical axis) with a single-light receiving device performs reflected laser reception, directionally receiving the signal from the LED emitter 13, and further refining the direction to the position where the light source can record the maximum signal level.

[0041] After ensuring that the direction of the collimated optical axis at all receiving nodes is parallel to the axis passing through the focal point and the off-axis parabolic metal mirror 3, the laser optical axis azimuth angle formed by the laser rangefinder is detected and collimated.

[0042]

[0043] In Formula 1: θ b y represents the divergence of the laser beam. s f represents the size of the laser spot in a horizontal direction within the focal plane of the off-axis parabolic metal mirror 3. p Let be the focal length of the off-axis parabolic metal mirror 3.

[0044] The laser beam diverges from zero position along the x-axis at an angle θ. x,b The laser beam diverges from zero on the y-axis at an angle θ. y,b They are respectively:

[0045]

[0046]

[0047] In Formula 2, x s It is the x-coordinate of the laser spot energy center on the focal plane of the laser radiation imaging instrument; y s This is the y-coordinate of the laser spot energy center on the focal plane of the laser radiation imaging instrument 7. The above calculations are performed by computer 11.

[0048] This invention utilizes CCD matrix and digital image processing technology to enable real-time display and quantification of laser optical axis deviation on a computer. Combined with a laser radiation imaging system, it visualizes the divergence and offset angle of the laser beam when detecting the parallelism of the three optical axes of a laser rangefinder, making the collimation system easier to operate and thus improving calibration efficiency.

[0049] The coordinate error of the registered image of the laser spot on CCD matrix 10 is greatly affected. In order to estimate the error of the CCD image acquisition processing algorithm, 10 sets of repeated detection experiments were conducted, each set of repeated experiments containing 100 snapshot experiments. Figure 2 The image processing algorithm error results are shown in the figure, with a standard deviation of 0.07 pixels. Therefore, the error in calculating the laser spot center is 0.21 pixels, or approximately 0.1″, which meets the practical application requirements for the image acquisition device in the collimation system.

[0050] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A laser rangefinder collimation system using a CCD matrix, characterized in that: The system includes a hollow corner reflector (2), an off-axis parabolic metal mirror (3), a rotating reflector (4), a first diagonal beam splitter (5), a second diagonal beam splitter (6), a laser radiation imaging device (7), a CCD matrix (10), a computer (11), and an LED emitter (13). The off-axis parabolic metal mirror (3), rotating reflector (4), first diagonal beam splitter (5), second diagonal beam splitter (6), laser radiation imaging device (7), and CCD matrix (10) form the aiming optical axis. The hollow corner reflector (2) is used to adjust the angular deviation of the laser receiving optical axis (1). The object surface metal reflector (3) is used to connect the laser receiving optical axis (1) with the aiming optical axis. The rotating reflector (4) is used to adjust the position deviation of the laser receiving optical axis (1). The first diagonal beam splitter (5) is used to reflect the light emitted by the LED emitter (13) into the aiming optical axis. The laser receiving optical axis (1) is calibrated by the off-axis parabolic metal reflector (3). The second diagonal beam splitter (6) is used to reflect the light in the visible light band emitted by the laser radiation imaging instrument (7) to the CCD matrix (10). The CCD matrix (10) works with the computer (11) to realize the visualization and quantization of the laser beam optical axis. The laser radiation imaging device (7) is located on the focal plane of the off-axis parabolic metal mirror (3), and the center point of the laser radiation imaging device (7) is conjugate with the position of the LED emitter (13). The laser rangefinder collimation system using a CCD matrix also includes an infrared spectral emitter (14). The LED emitter (13) and the infrared spectral emitter (14) serve as the light source for the collimated beam, forming a collimated optical axis. The collimated optical axis is parallel to the collimated axis of the laser receiving optical axis (1) after being reflected by an off-axis parabolic metal mirror (3).

2. The laser rangefinder collimation system using a CCD matrix according to claim 1, characterized in that: The collimation system of the laser rangefinder using a CCD matrix also includes a protective filter (8) and a cylindrical prism (9). The protective filter (8) and the cylindrical prism (9) are arranged sequentially between the second diagonal beam splitter mirror (6) and the CCD matrix (10). The protective filter (8) is used to avoid stray light in front of the CCD matrix (10), and the cylindrical prism (9) is used to focus the light passing through the protective filter (8) at the center of the CCD matrix (10).

3. The laser rangefinder collimation system using a CCD matrix according to claim 1, characterized in that: The collimation system of the laser rangefinder using a CCD matrix also includes an aperture (12), which is located in front of the LED emitter (13). The aperture (12) is used to adjust the light intensity and depth of field.

4. The laser rangefinder collimation system using a CCD matrix according to claim 1, characterized in that: The laser optical axis azimuth angle formed by the laser rangefinder is: ； In Formula 1: θ b y represents the divergence of the laser beam. s f represents the size of the laser spot in a horizontal direction within the focal plane of the off-axis parabolic metal mirror (3). p is the focal length of the off-axis parabolic metal mirror (3).

5. A laser rangefinder collimation system using a CCD matrix according to claim 4, characterized in that: The laser beam diverges from zero position along the x-axis at an angle θ. x,b The laser beam diverges from zero on the y-axis at an angle θ. y,b They are respectively: ; In formulas 2 and 3, x s It is the x-axis coordinate of the laser spot energy center on the focal plane of the laser radiation imaging instrument (7); y s It is the coordinate of the laser spot energy center on the y-axis of the focal plane of the laser radiation imaging instrument (7).

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