CN1545221A - A laser receiving device for laser zone plate collimation system - Google Patents

Abstract

A receiving device for a laser zone plate collimation system, which belongs to the technical field of optics, photoelectric detection and geometric position measurement, is characterized in that it is composed of a converging mirror, a zoom lens, a camera and a calibration mechanism, and solves the problem of using an area array camera wave The strip plate collimation system has different requirements on the distance from the measuring point to the receiving device and different spatial resolution of the receiver, and also solves the calibration problem of the system. The effects and benefits of the present invention are that the video camera is used as the photoelectric receiving device, and there are many photosensitive units, the output image is convenient for computer digital image processing, and the measurement accuracy and reliability are improved due to the realization of the variable measurement range and spatial resolution . Since there is no two-dimensional scanning mechanism in the device, the structure of the receiving device is simple and compact, and it is convenient for sealing installation. Since the device does not need to perform two-dimensional point-by-point scanning, the measurement time is reduced and the measurement speed is improved.

Description

A laser receiving device for laser zone plate collimation system

technical field

The invention belongs to the technical fields of optics, photoelectric detection and geometric position measurement, and relates to a laser receiving device used in a laser zone plate collimation system.

Background technique

The laser zone plate collimation system is composed of a laser light source, a zone plate and a laser receiving device arranged in sequence on a straight line. The laser beam emitted by the laser light source shoots to the wave zone plate, and under the action of the wave zone plate, a light spot will be formed on the laser receiving device. Under ideal conditions, the center of the laser light source, the center of the wave zone plate and the center of the light spot are in a line On a straight line, using this principle can achieve high-precision alignment and displacement measurement. Usually, the laser light source and the laser receiving device are installed on two reference points, and the zone plate is fixed on the measured point in between. When the measured point is displaced, the position of the light spot on the receiver will change. By measuring the change of the position of the light spot, the displacement of the measured point can be measured. The laser zone plate collimation system is often used to realize high-precision dam deformation observation.

In the laser zone plate collimation system, the role of the laser receiving device is to convert the position information of the light spot into an electrical signal. Most of the existing laser receiving devices use a two-dimensional translation scanning mechanism to drive a photoelectric receiving head to perform two-dimensional scanning in the receiving area to find and determine the position of the center of the light spot. The photoelectric receiving head is usually a four-quadrant photocell (or combination of four lenses and four photocells), since the detection of the position of the light spot is completed by scanning, the measurement speed is relatively slow. inspection, which makes it difficult for the automation of inspection.

There are also receiving heads that use the photosensitive surface of an area array camera to directly replace the four-quadrant photocell. Since there are more photosensitive units in the camera, and computer image processing technology can be used to analyze and process the received image, it can eliminate the influence of flickering and shaking of the light spot. Compared with The use of four-quadrant photocells has certain advantages.

However, since the moving range of the light spot is much larger than the photosensitive surface of the camera, the camera cannot directly use the camera to image the entire moving area of the light spot. It is still necessary to install the camera on a two-dimensional translation scanning mechanism to search for the position of the light spot.

If a general camera with a lens is directly used, since the direction of the light point light is close to parallel light, only the light within the entrance pupil range of the lens can enter the camera, and even if it enters the camera, the light points at different positions will converge to the focal point of the lens On the surface, it cannot image, so it cannot directly use a general camera with a lens, and a special optical system needs to be designed for the laser receiving device.

In addition, since the measurement point is close to the laser light source and far away from the receiver, the light point is large, and the displacement of the light point relative to the measurement point is large, requiring a large measurement range and relatively low spatial resolution. When measuring When the point is far away from the laser light source and close to the receiver, the light point is small, and the displacement of the light point relative to the measurement point is small. At this time, the camera is required to have a small measurement range and high spatial resolution, which requires the receiving device A variable measurement range and spatial resolution can be provided.

Since the laser receiving device is used to accurately measure the displacement of the light spot, the device must be able to calibrate itself so that the measurement result will not be affected by the optical parameters of the device.

Contents of the invention

The object of the present invention is to provide a laser receiving device for the laser zone plate collimation system, which can accurately detect the position of the light spot without performing two-dimensional scanning by using a camera with a fixed position and a corresponding optical mechanism. And it is easy to calibrate, which can meet the requirements of the laser zone plate collimation system for different resolutions and measurement ranges of the laser receiving device, and achieve the purpose of simplifying the system structure, improving the measurement accuracy and reducing the measurement time.

The technical solution of the present invention is to adopt a laser receiving device composed of five parts such as a converging lens, a camera, an imaging lens, a semi-transparent mirror, and a calibration plate, so that the position of the light spot can be accurately detected without performing two-dimensional scanning. And it is convenient for calibration, and at the same time solves the requirements of the laser zone plate collimation system on the different resolutions and measurement ranges of the laser receiving device, so as to achieve the purpose of the present invention.

The relative positions of these five parts are as follows: the converging lens 1 is the light entrance of the laser receiving device, the left side of the converging lens 1 is a half-mirror 4, and below the half-mirror 4 is a calibration plate 5, and on the calibration plate 5 There are light-emitting points at intervals, on the left side of the half-mirror 4 is the imaging lens 2, the imaging lens 2 is a zoom lens or a combination lens that can change multiple focal lengths, on the left side of the imaging lens 2 is camera3. The focal plane F of the converging lens 1 coincides with the entrance pupil of the imaging lens 2, the object plane of the imaging lens 2 coincides with the main plane U of the converging lens 1, and the image plane V of the imaging lens 2 coincides with the photosensitive surface of the video camera 3, from Viewed from the direction of the camera 3, the image formed by the calibration plate 5 passing through the half-mirror 4 coincides with the principal plane U of the converging lens 1 .

The working principle of the laser receiving device is as follows: after the light enters the receiving device, it first reaches the main plane U of the converging lens 1 to form a light point a, and after the light changes direction through the converging lens 1, it converges on the entrance pupil F of the imaging lens 2, and enters the Imaging lens 2, since the principal plane U of converging lens 1 is also the object plane of imaging lens 2, and its image plane V is the photosensitive surface of camera 3, so light spot a will form an image point b on the photosensitive surface of camera 3. When the position of the light point a changes, the position of the image point b will change accordingly, and its interrelationship is determined by the optical parameters of the imaging lens 2. Using the camera to output and process the image of the image point b, the light can be calculated by the computer. the position of point a.

The calibration of the device is realized through the half-mirror 4 and the calibration plate 5. There are light-emitting lattices with a certain spacing on the calibration plate 5. The light-emitting lattices of the calibration plate 5 pass through the half-mirror 4 and are imaged on the converging lens. 1 On the main plane U, a reference coordinate system is formed on the main plane U with these light-emitting lattices as coordinates. Camera 3 can determine the relative coordinate position of luminous point a in this reference coordinate system by measuring the position of each point of these luminous lattices, and comparing the position of luminous point a with the positions of these luminous lattices. The coordinate values will not change due to the change of the optical parameters of the imaging lens 2 .

In places where the measurement accuracy is not high, a flat scattering screen can be placed at the position of the main plane U of the converging lens 1 to replace the converging lens 1, which also plays the role of changing the direction of the incident light, but the utilization rate of the light is low, and at the same time it is affected by The influence of speckle caused by the plane scattering screen reduces the measurement accuracy, and the distance from the imaging lens 2 to the plane scattering screen is 2 to 8 times the size of the largest measurement area.

By changing the focal length of the imaging lens 2, the optical magnification of the imaging lens 2 can be changed. Since the size of the photosensitive surface of the camera 3 is fixed, the change of the optical magnification will be located at the size of the main plane U measurement area of the converging lens 1 and Spatial resolution for relative coordinates. In this way, the laser receiving device can achieve the best measurement range and spatial resolution by adjusting the focal length of the imaging lens 2 .

The effect and the benefit of the present invention are owing to adopt video camera as photoelectric receiving device, there are many photosensitive units, the image of its output is convenient to carry out computer digital image processing, and because can change measuring range and spatial resolution, make it reach optimal value, and have Calibration function, thus improving measurement accuracy and reliability. Since there is no two-dimensional scanning mechanism in the device, the structure of the receiving device is simple and compact, and it is convenient for sealing installation. Since the device does not need to perform two-dimensional point-by-point scanning, the measurement time is reduced and the measurement speed is improved.

Description of drawings

The figure is a structural schematic diagram of the laser receiving device of the laser alignment measurement system provided by the present invention.

In the figure: 1 converging lens, 2 imaging lens, 3 area array camera, 4 half mirror and 5 calibration plate.

U is the principal plane of the converging lens 1, F is the entrance pupil of the imaging lens 2 and the focal plane of the converging lens 1, and V is the photosensitive surface of the camera 3. a is the incident light point, b is the position of the image point of light point a on the photosensitive surface of the camera.

Detailed ways

The invention will be described in further detail below in conjunction with examples of implementation:

Converging lens 1, imaging lens 2, area camera 3, half-mirror 4 and calibration plate 5 in the laser receiving device can choose the following parameters: converging lens 1 is a diameter of 200 mm and a focal length of 1000 mm lens. The imaging lens 2 is an electric zoom lens with a focal length of 32-160mm. Video camera 3 is a 1/2 inch CCD black-and-white video camera, and its photosensitive surface size is 7.95 millimeters * 6.45 millimeters, and image pixel is 795 (H) * 596 (V). Half mirror 4 adopts a piece of 200 millimeters * 300 millimeters, the flat glass of thick 5 millimeters, only utilizes its lower reflection surface imaging. Calibration plate 5 is a 220 mm x 220 mm metal plate with a thickness of 0.3 mm, with a matrix of small holes with a diameter of 0.5 mm evenly distributed on it, the vertical and horizontal distances between the small holes are 10.00 mm, and there are light-emitting diodes behind the small holes as The light source can form a light-emitting lattice.

The above five parts are arranged and adjusted in the following manner: the converging lens 1 is arranged on the far right, and its main plane U is the light incident surface of the laser receiving device. The imaging lens 2 is about 1000 mm to the left of the converging lens 1, and the position of the imaging lens 2 is adjusted so that the entrance pupil coincides with the back focal plane F of the converging lens 1. The camera 3 is fixed on the left side of the imaging lens 2, the relative position between the camera 3 and the imaging lens 2 is adjusted and the focus of the imaging lens 2 is adjusted so that the light spot on the main plane U of the converging lens 1 can pass through the imaging lens 2 in A clear image is formed on the photosensitive surface V of the camera 3 . The half mirror 4 is arranged between the converging lens 1 and the imaging lens, and its center is about 150 millimeters away from the converging lens 1, fixed at an angle of 45 degrees from the upper left to the lower right, and its center coincides with the main axis of the converging lens 1. The calibration plate 5 is fixed directly below the half-mirror 4 in a horizontal manner, about 150 millimeters away from the half-mirror 4, and carefully adjusts the positions of the calibration plate 5 and the half-mirror 4 so that when viewed from the camera direction, The image formed by the small hole matrix on the calibration plate 5 through the semi-transparent mirror 4 coincides with the main plane U of the converging lens 1, and the center of the image is aligned with the center of the converging lens 1. When these light-emitting lattice points on the calibration plate 5 When it is on, a light-emitting lattice with a pitch of 10 mm can be formed on the light-receiving surface of the laser receiving device as a reference coordinate system.

When measuring, first light up the luminous dot matrix on the calibration plate 5, and measure the position of each luminous point. Due to the standard spacing of these light points, these light points can be used as reference coordinates to calculate optical parameters and correct the system optical image. Difference. Then turn off the light-emitting lattice on the calibration plate 5, measure and calculate the relative position of the laser point entering the receiving surface relative to these light-emitting lattices, and then the accurate coordinates of the laser point in the reference coordinate system can be obtained.

In the above system, when the focal length of the zoom lens is adjusted to the shortest 32mm, the measurement area of the device reaches the maximum, about 200mm, and the resolution is the lowest, about 0.33mm/pixel, collimated in the laser band plate In the system, it is suitable for the situation where the measurement point is far away from the laser receiving device. When the focal length of the zoom lens is adjusted to a maximum of 160mm, the measurement area of the device is the smallest, about 40mm, but the resolution reaches the highest, about 0.06mm/pixel. In the laser zone plate collimation system, it is suitable When the measurement point is close to the laser receiving device.

Claims (2)

1. A laser receiving device for a laser zone plate collimation system uses a video camera (3) as a receiving device, and the laser receiving device consists of a converging lens (1), a video camera (3), an imaging lens (2), and a semi-transparent A half mirror (4) is combined with a calibration plate (5), and is characterized in that: a) the entrance pupil of the imaging lens (2) is located at the back focal plane (F) of the converging lens; b) the object plane (U) of the imaging lens (2) coincides with the principal plane of the converging lens (1); c) the image plane (V) of the imaging lens (2) coincides with the photosensitive surface of the camera; d) The half mirror (4) is placed so that the image of the calibration plate (5) coincides with the main plane (U) of the converging lens (1). 2. A kind of laser receiving device for laser zone plate collimation system according to claim 1, is characterized in that can be placed on the position of main plane (U) of converging lens (1) with plane scattering screen, replaces converging The lens (1), the distance from the imaging lens 2 to the plane scattering screen is 2 to 8 times the size of the largest measurement area.

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