An apparatus for testing the parallelism of two gratings

Abstract

The application is a device for testing parallelism of two gratings, which comprises a first grating, a second grating, a laser, a pinhole diaphragm, a half-transmission half-reflection prism, a pentagonal prism and an observation screen arranged on the same optical axis, and comprises two parts of adjusting grating surface parallelism and adjusting grating line parallelism. Two light spots on the observation screen are in the same horizontal straight line by adjusting the deflection angle of the first grating and the second grating through mirror reflection of the first grating and the second grating, so that the grating surface parallelism of the two gratings is adjusted. Two light spots on the observation screen are in the same vertical straight line by adjusting the rotation angle of the first grating and the second grating rotating around the horizontal direction through the diffraction effect of the first grating and the second grating, so that the grating line parallelism of the two gratings is adjusted. The application has simple structure, easy-to-understand principle and convenient operation.

Description

Technical Field

[0001] This invention relates to a grating measurement system, and in particular discloses a device for verifying the parallelism of two gratings, belonging to the field of optical metrology technology. Background Technology

[0002] Precision displacement measurement technology is an indispensable supporting technology in modern manufacturing and scientific research. The measurement range and accuracy determine the dimensions and precision of the manufactured product. The period of a grating serves as the measurement benchmark for a grating displacement measurement system, and achieving accurate calibration of the grating period is a core aspect of improving the accuracy of the displacement measurement system. In the process of calibrating ordinary gratings using national standard material gratings, the synchronization of the displacements of the two gratings is crucial to the accuracy of the calibration results. Grating period calibration requires equal displacements of the two gratings; however, differences in the initial yaw angles and rotation angles of the two gratings will lead to deviations in the displacement during subsequent calibration, thus causing calibration errors in the grating period.

[0003] Current methods for verifying the parallelism of two gratings involve checking whether the grating surfaces are parallel, without considering the displacement measurement error caused by the rotation of the grating lines. Therefore, finding a simple and accurate method to verify whether there are angular errors in the two gratings in the yaw and rotation directions is of great significance in the field of grating spacing calibration. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art by designing a device for verifying the parallelism of two gratings. This device verifies the parallelism of the two gratings and ensures the synchronous displacement of the two gratings during the periodic calibration process, thereby improving the measurement accuracy and reducing measurement errors during the grating calibration process.

[0005] This invention is implemented as follows: A device for verifying the parallelism of two gratings, characterized in that it comprises a first grating, a second grating, a laser, a pinhole aperture, a semi-transparent and semi-reflective prism, a pentagonal prism, and an observation screen arranged coaxially. The first grating and the second grating are placed face-to-face in grating adjustment frames for adjusting the grating orientation. The laser is used to emit a laser source. The optical path of the device is as follows: the laser emitted by the laser is incident perpendicularly to the semi-transparent and semi-reflective prism. The transmitted light from the semi-transparent and semi-reflective prism is incident on the surface of the first grating and undergoes specular reflection and diffraction. The reflected light from the semi-transparent and semi-reflective prism forms a spot on the observation screen. The transmitted light and reflected light from the semi-transparent and semi-reflective prism form a 90° angle. The reflected light and diffracted light from the first grating... After being incident on the surface of the second grating, the light also undergoes specular reflection and diffraction. The reflected and diffracted light from the second grating are incident perpendicularly to the pentagonal prism in stages. After being refracted by the pentagonal prism, they form outgoing light. The incident light from the pentagonal prism and the outgoing light after refraction also form a 90° angle. The outgoing light from the pentagonal prism is then emitted to the semi-transparent and semi-reflective prism, and finally transmitted through the semi-transparent and semi-reflective prism to the observation screen to form a light spot. The two grating surfaces are determined to be parallel by the fact that the light spots formed on the observation screen by the reflected light from the semi-transparent and semi-reflective prism and the specular reflection of the outgoing light from the pentagonal prism are on the same horizontal straight line. The two grating lines are determined to be parallel by the fact that the light spots formed on the observation screen by the reflected light from the semi-transparent and semi-reflective prism and the diffraction effect of the pentagonal prism are on the same vertical straight line.

[0006] The device adjusts the reflected light from the semi-transparent prism and the emitted light from the pentagonal prism in the mirror reflection path by horizontally shifting the position of the pentagonal prism and simultaneously adjusting the tilt angle of the first and second gratings, so that the two light spots formed on the observation screen are aligned on the same horizontal straight line, thus achieving parallel adjustment of the two grating surfaces. The device also adjusts the reflected light from the semi-transparent prism and the emitted light from the pentagonal prism in the diffraction effect path by horizontally shifting the position of the pentagonal prism and adjusting the rotation angle of the second grating around the horizontal direction, so that the two light spots formed on the observation screen are aligned on the same vertical straight line, thus achieving parallel adjustment of the two grating lines.

[0007] Based on geometric optics, this invention utilizes the principle of light path transformation of a prism to determine whether two gratings are parallel by observing whether the two beams of light overlap, thus ensuring that the grating surfaces and grating lines of the two gratings are in a parallel state.

[0008] The beneficial effects of this invention are as follows: Compared with the prior art, the principle of this invention is simple and easy to understand. It applies geometric optics and utilizes the light path reversal principle of a prism to transform the parallelism judgment of two gratings into the judgment of the parallelism of two light beams, effectively solving the problem of the complex operation of grating parallelism judgment. This invention can simultaneously determine whether the grating surfaces and grating lines of two gratings are parallel, effectively verifying whether the two gratings are parallel in terms of tilt angle and rotation angle, reducing displacement error when the two gratings move synchronously, and ensuring that the two gratings move synchronously along the grating vector direction. The device of this invention has a simple structure and does not require changes to the optical path arrangement of the original measuring device, making it widely applicable and cost-effective. Attached Figure Description

[0009] Figure 1 This is a schematic diagram showing the positional relationship of each component when the present invention is in operation.

[0010] Figure 2 This is a simplified schematic diagram of the optical path during the operation of this invention.

[0011] In the diagram: 1. Laser; 2. Pinhole aperture; 3. Observation screen; 4. Semi-transparent and semi-reflective prism; 5. First grating; 6. Pentagonal prism; 7. Second grating. Detailed Implementation

[0012] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0013] Example 1:

[0014] According to the appendix Figure 1 and attached Figure 2 The present invention is a device for verifying the parallelism of two gratings, comprising a first grating 5, a second grating 7, a laser 1, a pinhole aperture 2, a semi-transparent and semi-reflective prism 4, a pentagonal prism 6, and an observation screen 3 arranged coaxially. The first grating 5 and the second grating 7 are placed face to face in a grating adjustment frame for adjusting the grating orientation. The laser 1 is used to emit a laser light source.

[0015] The reflected light path of the device is as follows: the laser emitted by the laser 1 passes through the pinhole aperture 2 and is perpendicularly incident on the semi-transparent and semi-reflective prism 4. The transmitted light from the semi-transparent and semi-reflective prism 4 is incident on the surface of the first grating 5 and undergoes specular reflection. The reflected light from the semi-transparent and semi-reflective prism 4 forms a light spot on the observation screen 3. The transmitted light and reflected light from the semi-transparent and semi-reflective prism 4 form a 90° angle. The reflected light from the specular reflection of the first grating 5 is incident on the surface of the second grating 7 and also undergoes specular reflection, perpendicularly... The incident light is refracted by the pentagonal prism 6 to form the outgoing light of the pentagonal prism 6, which continues to be emitted to the semi-transparent and semi-reflective prism 4, and finally transmitted through the semi-transparent and semi-reflective prism 4 to the observation screen 3 to form a light spot. The incident light of the pentagonal prism 6 and the outgoing light after refraction also form a 90° angle. The parallelism of the two grating surfaces is determined by the fact that the light spots formed on the observation screen 3 by the reflected light of the semi-transparent and semi-reflective prism 4 and the outgoing light of the pentagonal prism 6 are on the same horizontal straight line.

[0016] The diffraction path of the device is as follows: when the transmitted light from the semi-transparent and semi-reflective prism 4 is incident on the surface of the first grating 5, a diffraction effect occurs. The first-order diffracted light from the first grating 5 is incident on the surface of the second grating 7 and also undergoes a diffraction effect. It is then incident perpendicularly on the pentagonal prism 6, refracted by the pentagonal prism 6 to form the outgoing light of the pentagonal prism 6, which continues to be emitted to the semi-transparent and semi-reflective prism 4. Finally, it is transmitted through the semi-transparent and semi-reflective prism 4 to the observation screen 3 to form a light spot. The incident light from the pentagonal prism 6 and its refracted outgoing light form a 90° angle. The parallelism of the two grating lines is determined by the fact that the light spots formed on the observation screen 3 by the reflected light from the semi-transparent and semi-reflective prism 4 and the outgoing light from the pentagonal prism 6 are on the same vertical straight line.

[0017] The device adjusts the reflected light from the semi-transparent and semi-reflective prism 4 and the emitted light from the pentagonal prism 6 in the reflected light path so that the two light spots formed on the observation screen 3 are on the same horizontal straight line by adjusting the position of the horizontally displaced pentagonal prism and adjusting the tilt angle of the first grating and the second grating, and adjusts the two gratings to be arranged with parallel grating surfaces.

[0018] The device adjusts the reflected light from the semi-transparent and semi-reflective prism 4 and the emitted light from the pentagonal prism 6 in the diffraction path so that the two light spots formed on the observation screen 3 are on the same vertical straight line by adjusting the position of the horizontally displaced pentagonal prism and adjusting the rotation angle of the second grating around the horizontal direction, and adjusts the two gratings so that the grating lines are arranged in parallel.

[0019] During the parallelism verification of the two gratings, the first and second gratings have specular reflection and diffraction effects. At the same time, it is also necessary to ensure that the laser light is strictly perpendicularly incident on the semi-transparent and semi-reflective prism, the transmitted light and reflected light of the semi-transparent and semi-reflective prism are strictly perpendicular, the laser light is strictly perpendicularly incident on the pentagonal prism, and the outgoing light of the pentagonal prism is strictly perpendicular to the incident light.

[0020] In this embodiment, a laser diode with a center wavelength of 405nm is used as the light source to perform parallelism verification of the two gratings. The specific operation steps are as follows:

[0021] (1) Turn on the laser 1 and adjust the incident angle of the laser source so that the laser emitted by the laser 1 passes through the aperture 2 and is incident vertically into the semi-transparent and semi-reflective prism 4.

[0022] (2) Adjust the position of the observation screen 3 so that the reflected light from the semi-transparent and semi-reflective prism 4 is emitted onto the observation screen 3.

[0023] (3) Adjust the position of the first grating 5 so that the transmitted light from the semi-transparent and semi-reflective prism 4 is incident on the surface of the first grating 5 at a certain angle, and the specular reflection phenomenon and diffraction effect occur, forming reflected light and first-order diffracted light respectively.

[0024] (4) Adjust the position of the second grating 7 so that the reflected light from the first grating 5 is incident on the surface of the second grating 7 at a certain angle. At the same time, the second grating 7 continues to exhibit specular reflection and diffraction effects, and also forms corresponding reflected light and diffracted light respectively.

[0025] (5) Adjust the angle of the pentagonal prism 6 so that the reflected light reflected by the mirror of the second grating 7 is perpendicularly incident into the interior of the pentagonal prism 6.

[0026] (6) Adjust the position of the pentagonal prism 6 so that the outgoing light refracted by the pentagonal prism 6 passes through the semi-transparent and semi-reflective prism 4 and then enters the observation screen 3.

[0027] (7) Observe whether the light spot formed on the observation screen by the outgoing light refracted by the pentagonal prism and the light spot formed on the observation screen by the reflected light of the semi-transparent and semi-reflective prism are on the same horizontal straight line. If the two light spots are not on the same horizontal straight line, adjust the tilt angle of the second grating 7 until the two light spots are on the same horizontal line. This indicates that the tilt angles of the first grating 5 and the second grating 7 are consistent, that is, the grating surfaces of the first grating 5 and the second grating 7 are parallel.

[0028] (8) Adjust the angle of the pentagonal prism 6 so that the first-order diffracted light of the first grating 5 is incident on the surface of the second grating 7 and the diffracted light of the second grating 7 is incident perpendicularly into the interior of the pentagonal prism 6.

[0029] (9) Adjust the position of the pentagonal prism 6 so that the outgoing light refracted by the pentagonal prism 6 passes through the semi-transparent and semi-reflective prism 4 and then enters the observation screen 3.

[0030] (10) Observe whether the light spots formed on the observation screen by the outgoing light refracted by the pentagonal prism and the light spots formed on the observation screen by the reflected light of the semi-transparent and semi-reflective prism are on the same vertical straight line. If the two light spots are not on the same vertical straight line, adjust the rotation angle of the second grating 7 around the horizontal direction until the two light spots are on the same vertical straight line. This indicates that the grating lines of the first grating 5 and the second grating 7 are at the same angle with the horizontal direction, that is, the grating lines of the first grating 5 and the second grating 7 are parallel.

[0031] Based on the principle of geometric optics, this invention utilizes the light path reversal effect of a semi-transparent and semi-reflective prism and a pentagonal prism. By observing the positional relationship of the two light spots formed on the observation screen by the reflected light from the semi-transparent and semi-reflective prism and the emitted light from the pentagonal prism in the horizontal and vertical directions respectively through the reflected light path and the diffraction light path, it is possible to determine whether the grating surfaces and grating lines of the two gratings are parallel.

[0032] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. An apparatus for testing the parallelism of two gratings, characterized by: The device comprises first grating, second grating, laser, pinhole diaphragm, half-transmission half-reflection prism, pentagonal prism and observation screen arranged on the same optical axis, the first grating and the second grating are placed face to face in grating adjusting frame for adjusting the attitude of the grating, The optical path of the device is as follows: the laser emitted by the laser vertically enters the half-transmission half-reflection prism after passing through the pinhole diaphragm, the transmission light of the half-transmission half-reflection prism is incident on the surface of the first grating and mirror reflection and diffraction effect occurs, the reflected light of the half-transmission half-reflection prism forms a light spot on the observation screen, the reflected light and the diffraction light of the first grating are incident on the surface of the second grating and mirror reflection and diffraction effect also occurs, the reflected light and the diffraction light of the second grating are vertically incident on the pentagonal prism in turns, the emergent light of the pentagonal prism is refracted and forms the exit light, the exit light of the pentagonal prism is emitted to the half-transmission half-reflection prism, and finally the transmission light of the half-transmission half-reflection prism is transmitted to the observation screen to form a light spot, the light spots formed by the reflected light of the half-transmission half-reflection prism and the exit light of the pentagonal prism in the mirror reflection on the observation screen are in the same horizontal straight line to determine that the two grating surfaces are parallel, the light spots formed by the reflected light of the half-transmission half-reflection prism and the exit light of the pentagonal prism in the diffraction effect on the observation screen are in the same vertical direction straight line to determine that the two grating lines are parallel, The device adjusts the reflected light of the half-transmission half-reflection prism and the exit light of the pentagonal prism in the mirror reflection to form two light spots on the observation screen in the same horizontal straight line by horizontally displacing the pentagonal prism and adjusting the deflection angle of the first grating and the second grating, thereby completing the parallel adjustment of the two grating surfaces, Meanwhile, the device adjusts the reflected light of the half-transmission half-reflection prism and the exit light of the pentagonal prism in the diffraction effect to form two light spots on the observation screen in the same vertical direction straight line by horizontally displacing the pentagonal prism and adjusting the rotation angle of the second grating around the horizontal direction, thereby completing the parallel adjustment of the two grating lines.

2. A device for testing the parallelism of two gratings according to claim 1, characterized in that: The transmission light and the reflected light of the half-transmission half-reflection prism form a 90° angle, and the incident light and the exit light of the pentagonal prism after refraction also form a 90° angle.

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