CN104154882B - Dual-beam device for detecting parallelism and method based on differential confocal measurement - Google Patents

Abstract

The dual-beam parallelism detection device and method based on differential defocus measurement belongs to optical detection technology; the double-beam to be measured is incident on the beam-splitting prism after passing through the collimating objective lens, and is divided into a beam of reflected light and a beam of light on the beam-splitting surface of the beam-splitting prism. Transmitted light, the transmitted light beam and the reflected light beam of the double beam to be measured are respectively completely incident on the transmission and reflection image acquisition surfaces of the high-precision image acquisition device in the transmission and reflection directions. The image acquisition surface of the high-precision image acquisition device is relative to the focal plane of the collimating objective lens Differential defocus arrangement can simultaneously obtain two transmitted beams and two reflected beams of the two beams to be measured, a total of four spots and their centroid positions, and the angle between the two beams to be measured can be calculated through the defocus distance and the spot centroid distance The included angle represents the parallelism of the two beams to be measured. The invention not only can detect the parallelism of the beams when the parallelism of the two beams to be measured is good, but also is not affected by the off-axis error of the incident light.

Description

Dual-beam parallelism detection device and method based on differential defocus measurement

technical field

The invention belongs to optical detection technology, and mainly relates to a detection device and method for the parallelism of two or more light beams based on the principle of differential defocus measurement.

Background technique

Combined with a multi-axis beamsplitter, laser interferometers can be used for angle measurement. When using a laser interferometer to measure angles, the parallelism of the outgoing beam of the beam splitter group is closely related to the measurement accuracy of the laser interferometer, and the parallelism of the outgoing beam largely determines the measurement accuracy of the laser interferometer. For this reason, it is necessary to detect the parallelism of the beam emitted by the beam splitter group.

Zhang Lei and others from Changchun University of Science and Technology proposed a device for detecting the parallelism of two parallel beams, using two pentagonal prisms and an optical wedge to convert the two beams of light that are farther away into two beams of light that are closer together. Furthermore, a small-diameter self-collimating collimator can be used to focus and measure the converted two beams of light [A device for detecting parallelism of two parallel beams, publication number: CN100504289C]. The focus of the design of this device is to use a small-caliber self-collimating collimator to measure the parallelism of two incident light beams at a long distance, so as to reduce the production cost of the collimator. However, when the parallelism of the measured double beams is good, the After the two beams are focused, two mostly overlapping spots will be formed on the focal plane. At this time, it is difficult for the focusing measurement method to obtain the parallelism information of the two parallel beams to be measured.

Zhang Lei and others from Changchun University of Science and Technology then proposed a wide-distance beam parallelism detection device. The white light spectrum is extended to the laser and infrared light spectrum, becoming a multi-spectral optical system [Wide-distance beam parallelism detection device, publication number: CN101408413B]. However, it is still difficult for the detection device to obtain information on the parallelism of the beams to be measured when the parallelism of the two beams to be measured is relatively good.

Zhu Qing and others from the Shanghai Institute of Optics and Fine Mechanics of the Chinese Academy of Sciences proposed a device for measuring the parallelism of laser beams. The beam is composed of an aperture, a converging lens, a half mirror, two cylindrical lenses, and two four-quadrant detectors. The parallelism detector detects the parallelism of the light beam based on the focus error detection of the astigmatism method [the device for measuring the parallelism of the laser beam, publication number: CN2847219Y]. However, the measurement focus of this device is aimed at the detection of the divergence angle of a beam of laser light, rather than the detection of the parallelism between two or more beams of parallel light.

Cui Yanmei and others from the Beijing Great Wall Metrology and Testing Technology Institute of Aerospace Science and Industry Corporation proposed a detection method for beam parallelism and aiming error. The beam to be measured is injected into the theodolite through a pentaprism, and the parallelism of the beam to be measured is read out by the theodolite [A detection method for beam parallelism and aiming error, publication number: CN101261119B]. The advantage of this measurement method is that it is relatively direct, and its accuracy is mainly determined by the theodolite, and the accuracy of the entire system can reach 2″. However, the measurement speed of this method is slow, and it is difficult to measure when the measured beam has good parallelism.

To sum up, the main problem of the current methods for measuring the parallelism of beams is that the overlap of spots during focusing measurement affects the measurement accuracy, especially when the measured beams have good parallelism, it is difficult to achieve parallelism of double or multiple beams. measure of sex.

Contents of the invention

In order to solve the defects in the above-mentioned background technology, the present invention proposes a dual-beam parallelism detection device and method based on the principle of differential defocus measurement. The parallelism of the beam is characterized by the specific value of the quantized beam angle, and the measurement accuracy is high. , especially when the parallelism of the two beams to be measured is relatively good, high-precision detection of the parallelism of the measured beams can still be achieved.

The purpose of the present invention is achieved like this:

A dual-beam parallelism detection device based on differential defocus measurement, in which two beams to be measured are arranged in the incident direction of the optical axis of the collimating objective lens, and a beam splitter and a transmission direction are sequentially arranged in the outgoing direction of the optical axis of the collimating objective lens A high-precision image acquisition device, the high-precision image acquisition device for transmitted light beams is connected to a computer equipped with image acquisition software, the double beams to be measured are incident on the beam splitting prism after passing through the collimating objective lens, and are split on the beam splitting surface of the beam splitting prism It is a transmitted beam and a reflected beam, and the transmitted beam of the double beam to be measured is completely incident on the transmitted beam image acquisition surface of the high-precision image acquisition device in the transmission direction; A high-precision image acquisition device in the reflection direction is arranged on the beam optical path, and the reflected beams of the double beams to be measured are completely incident on the reflected beam image acquisition surface of the high-precision image acquisition device in the reflection direction; the high-precision image acquisition device in the reflection direction is connected with the device There is a computer connection with image acquisition software; the collimating objective lens has a transmission focal plane and a reflection focal plane respectively in the transmission direction and the reflection direction of the dichroic prism, and the transmission focal plane does not coincide with the transmission beam image collection surface, and the reflection focal plane The plane does not coincide with the reflected beam image acquisition surface, and when the transmitted beam image acquisition surface of the high-precision image acquisition device in the transmission direction is located in front of the transmission focal plane of the collimating objective lens, the reflected beam image acquisition surface of the high-precision image acquisition device in the reflection direction Located at the rear of the reflection focal plane of the collimating objective lens; or when the transmitted beam image acquisition surface of the high-precision image acquisition device in the transmission direction is located at the rear of the transmission focal plane of the collimation objective lens, the reflected beam image acquisition of the high-precision image acquisition device in the reflection direction The plane is located in front of the reflective focal plane of the collimating objective.

A method for detecting parallelism of two light beams based on differential defocus measurement, comprising the following steps:

1. After the double beams to be tested are incident on the collimating objective lens, adjust the position of the high-precision image acquisition device in the transmission and reflection directions to ensure that the image acquisition surfaces of the transmission and reflection beams of the high-precision image acquisition device in the transmission and reflection directions are respectively in the position of the collimation objective lens. The front part of the transmission focal plane and the rear part of the reflection focal plane, or the transmission and reflection beam image collection surfaces are respectively at the transmission focal plane rear part and the reflection focal plane front part of the collimating objective lens, and the transmission and reflection beam image collection surfaces are adjusted to the transmission, reflection The reflection focal plane distance makes it possible to see two completely separated complete spots in the images collected by the high-precision image acquisition device in the transmission and reflection directions;

2. Use the image acquisition software in the computer to obtain the spot images of the two transmitted light beams in the high-precision image acquisition device, and obtain the corresponding two spot centroid positions (x ₁₁ , y ₁₁ ) and (x ₁₂ , y ₁₂ ) through image processing , the centroid distance d ₁ of the two light spots is ((x ₁₁ -x ₁₂ ) ² +(y ₁₁ -y ₁₂ ) ² ) ^0.5 , similarly, the centroid distance d of the two reflected light beams in the reflective high-precision image acquisition device is obtained ₂ , the angle between the directions of the two beams to be measured is Where f is the focal length of the collimating objective lens, and β is used to describe the parallelism of the double beams to be measured.

The present invention has following characteristics and good effect:

1. The device proposed in the present invention is based on the principle of defocus measurement, which can simultaneously collect the spot centroid position information of two light beams, and can still realize the detection of double beams when the parallelism of the two beams to be measured is good (even the two beams are completely parallel). The synchronous acquisition of the centroid position of the beam spot avoids the spot overlap problem of the focusing measurement method when the parallelism of the two beams to be measured is good, and greatly reduces the influence of environmental factors such as light source beating and air disturbance on the parallelism measurement. One of the main innovation points that the present invention is different from the prior art.

2. The device proposed by the present invention, the positions of its two groups of high-precision image acquisition devices are respectively located in front of the focal plane and behind the focal plane of the collimating objective lens, that is, the device and method adopt differential defocus measurement. The use of differential defocus measurement can not only realize the simultaneous acquisition of the centroid position of the double beam spot when the parallelism of the two beams to be measured is good (even the two beams are completely parallel), but also can eliminate the detection error caused by the off-axis of the incident light , which is two of the main innovation points that the present invention is different from the prior art.

Description of drawings

Figure 1 is a schematic diagram of the structure of a dual-beam parallelism detection device based on differential defocus measurement

Figure 2 is a schematic diagram of the spots and centroid positions of the two transmitted beams on the image acquisition surface

Part number description in the figure: 1. Double beams to be tested, 2. Collimating objective lens, 3. Splitter prism, 4a. High-precision image acquisition device in the transmission direction, 4b. High-precision image acquisition device in the reflection direction, 5. Computer, 6a. Transmitted focal plane, 6b. Reflected focal plane, 7a. Transmitted beam image collection surface, 7b. Reflected beam image collection surface, 8a 8b. Spots of two transmitted beams

detailed description

Embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings.

A double-beam parallelism detection device based on differential defocus measurement, in which a double-beam 1 to be measured is arranged on the incident direction of the optical axis of the collimating objective lens 2, and beam splitting prisms are sequentially arranged on the outgoing direction of the optical axis of the collimating objective lens 2 3 and the transmission direction high-precision image acquisition device 4a, the transmission direction high-precision image acquisition device 4a is connected with the computer 5 equipped with image acquisition software, the double light beam 1 to be measured is incident on the beam splitting prism 3 after passing through the collimating objective lens 2, On the beam-splitting surface of the beam-splitting prism 3, it is divided into a transmitted beam and a reflected beam, and the transmitted beam of the double beam 1 to be measured is completely incident on the transmitted beam image acquisition surface 7a of the high-precision image acquisition device 4a in the transmission direction. Above: on the optical path of the reflected beam of the double beam 1 to be measured through the dichroic prism 3, a high-precision image acquisition device 4b in the reflection direction is arranged, and the reflected beam of the double beam 1 to be measured is completely incident on the high-precision image acquisition device 4b in the reflection direction On the reflected light beam image acquisition surface 7b; the reflection direction high-precision image acquisition device 4b is connected with the computer 5 equipped with image acquisition software; plane 6a and reflection focal plane 6b, the transmission focal plane 6a does not coincide with the transmission beam image collection surface 7a, the reflection focal plane 6b does not coincide with the reflection beam image collection surface 7b, and the high-precision image collection device 4a in the transmission direction When the transmitted light beam image collection surface 7a is located at the front portion of the transmission focal plane 6a of the collimating objective lens 2, the reflected light beam image collection surface 7b of the high-precision image collection device 4b in the reflection direction is located at the rear portion of the reflection focal plane 6b of the collimating objective lens 2; or When the transmitted beam image acquisition surface 7a of the high-precision image acquisition device 4a in the transmission direction is located at the rear of the transmission focal plane 6a of the collimating objective lens 2, the reflected beam image acquisition surface 7b of the high-precision image acquisition device 4b in the reflection direction is located at the collimation objective lens 2 The reflective focal plane 6b front.

The distance a1 between the transmitted beam image acquisition surface 7a of the high-precision image acquisition device 4a in the transmission direction and the transmission focal plane 6a of the collimating objective lens 2 is such that the transmitted beam of the double beam ₁ to be measured is completely incident on the transmitted beam image acquisition surface 7a , and the two light beams are completely separated so that the image acquisition device 4a in the transmission direction collects two complete and completely separated spots; The distance a ₂ is such that the reflected beam of the double beam 1 to be measured is completely incident on the reflected beam image collection surface 7b, and the two beams are completely separated so that the high-precision image collection device 4b in the reflection direction collects two complete and completely separated spots.

The method for detecting parallelism of two light beams based on differential defocus measurement comprises the following steps:

1. After the double beams to be tested are incident on the collimating objective lens, adjust the position of the high-precision image acquisition device in the transmission and reflection directions to ensure that the image acquisition surfaces of the transmission and reflection beams of the high-precision image acquisition device in the transmission and reflection directions are respectively in the position of the collimation objective lens. The front part of the transmission focal plane and the rear part of the reflection focal plane, or the transmission and reflection beam image collection surfaces are respectively at the transmission focal plane rear part and the reflection focal plane front part of the collimating objective lens, and the transmission and reflection beam image collection surfaces are adjusted to the transmission, reflection The reflection focal plane distance makes it possible to see two completely separated complete spots in the images collected by the high-precision image acquisition device in the transmission and reflection directions;

2. Use the image acquisition software in the computer to obtain the spot images of the two transmitted light beams in the high-precision image acquisition device, and obtain the corresponding two spot centroid positions (x ₁₁ , y ₁₁ ) and (x ₁₂ , y ₁₂ ) through image processing , the centroid distance d ₁ of the two light spots is ((x ₁₁ -x ₁₂ ) ² +(y ₁₁ -y ₁₂ ) ² ) ^0.5 , similarly, the centroid distance d of the two reflected light beams in the reflective high-precision image acquisition device is obtained ₂ , the angle between the directions of the two beams to be measured is Where f is the focal length of the collimating objective lens, and β is used to describe the parallelism of the double beams to be measured.

When using the above-mentioned dual-beam parallelism detection device and method based on differential defocus measurement to measure the parallelism of the double-beams to be tested, two sets of high-precision image acquisition devices simultaneously collect images, and at the same time acquire the reflected beams of the double-beams to be measured passing through the beam splitter The image and the position information of the center of mass of the two spots of the two spots of the transmitted beam and the two spots of the transmitted beam not only avoids the spot overlap problem when the parallelism of the two beams to be measured is good, but also greatly reduces environmental factors such as light source beating and air disturbance Effects on parallelism measurements.

The dichroic prism 3 in the present invention can also be replaced by other spectroscopic components; and the device and method of the present invention are not limited to the double beams produced by the beam splitter group, and can also be used for multiple parallel beams produced in other ways The measurement of parallelism, that is, the parallelism between any two beams in the multi-beams can be measured by the method of the present invention.

Claims (1)

1. A double-beam parallelism detection method based on differential defocus measurement, on the incident direction of the optical axis of the collimating objective lens (2), a double-beam beam (1) to be measured is provided, and the light beam of the collimating objective lens (2) A beamsplitter prism (3) and a high-precision image acquisition device (4a) in the transmission direction are sequentially arranged on the axis exit direction, and the high-precision image acquisition device (4a) in the transmission direction is connected with a computer (5) equipped with image acquisition software, to be tested The double light beam (1) is incident on the beam splitting prism (3) after passing through the collimating objective lens (2), and is divided into a beam of transmitted beam and a beam of reflected beam on the beam splitting surface of the beam splitting prism (3). The transmitted beam of the double beam (1) is completely incident on the transmitted beam image acquisition surface (7a) of the high-precision image acquisition device (4a) in the transmission direction; A high-precision image acquisition device (4b) in the reflection direction is arranged on the beam optical path, and the reflected beams of the double beams (1) to be measured are completely incident on the reflection beam image acquisition surface (7b) of the high-precision image acquisition device (4b) in the reflection direction Described reflective direction high precision image acquisition device (4b) is connected with the computer (5) that image acquisition software is housed; Described collimating objective lens (2) has transmission focal point respectively in the transmission direction and reflection direction of dichroic prism (3) plane (6a) and reflection focal plane (6b), described transmission focal plane (6a) does not coincide with transmission beam image collection surface (7a), described reflection focal plane (6b) and reflection beam image collection surface (7b) do not coincide overlap, and when the transmitted light beam image acquisition surface (7a) of the high-precision image acquisition device (4a) in the transmission direction is located at the front of the transmission focal plane (6a) of the collimating objective lens (2), the high-precision image acquisition device (4b) in the reflection direction ) is located at the back of the reflective focal plane (6b) of the collimating objective lens (2); or the transmitted beam image acquisition surface (7a) of the high-precision image acquisition device (4a) is located at When the rear part of the transmission focal plane (6a) of the straight objective lens (2), the reflected light beam image acquisition surface (7b) of the high-precision image acquisition device (4b) in the reflection direction is located in front of the reflection focal plane (6b) of the collimating objective lens (2) Department, it is characterized in that: the method comprises the following steps: 1. After the double beams to be tested are incident on the collimating objective lens, adjust the positions of the high-precision image acquisition device in the transmission direction and the high-precision image acquisition device in the reflection direction to ensure the transmission of the high-precision image acquisition device in the transmission direction and the high-precision image acquisition device in the reflection direction. The image collection surface of the beam and the image collection surface of the reflected beam are respectively in front of the transmission focal plane and the rear of the reflection focal plane of the collimating objective lens, or the image collection surface of the transmitted beam and the image collection surface of the reflected beam are respectively behind the transmission focal plane of the collimation objective lens and the front part of the reflective focal plane, and adjust the distance between the transmitted beam image collection surface and the transmitted focal plane, and adjust the distance between the reflected beam image collection surface and the reflective focal plane at the same time, so that the high-precision image acquisition device in the transmission direction and the high-precision image acquisition in the reflection direction In the images collected by the device, two completely separated complete light spots can be seen; 2. Use the image acquisition software in the computer to obtain the spot images of the two transmitted light beams in the high-precision image acquisition device, and obtain the corresponding two spot centroid positions (x ₁₁ , y ₁₁ ) and (x ₁₂ , y ₁₂ ) through image processing , the centroid distance d ₁ of the two light spots is ((x ₁₁ -x ₁₂ ) ² +(y ₁₁ -y ₁₂ ) ² ) ^0.5 , similarly, the centroid distance d of the two reflected light beams in the reflective high-precision image acquisition device is obtained ₂ , the angle between the directions of the two beams to be measured is Wherein f is the focal length of the collimating objective lens, and β is used to describe the parallelism of the double beams to be measured. In the formula, a ₁ is the transmission beam image acquisition surface (7a) of the high-precision image acquisition device (4a) in the transmission direction and the collimating objective lens ( 2) the distance of the transmission focal plane (6a), a ₂ is the distance of the reflection beam image acquisition surface (7b) of the reflection direction high-precision image acquisition device (4b) and the reflection focal plane (6b) of the collimating objective lens (2) .