Method for scanning and calibrating focal plane of large-aperture objective with small-aperture light beam

Abstract

The application discloses a method for scanning and calibrating a focal plane of a large-aperture objective lens by using a small-aperture light beam, and aims at solving the problems of high economic cost, inconvenient operation and small application range in the focal plane calibration process of a large-aperture objective lens used in a field or a large-aperture objective lens used on line in the prior art. In the application, a small-aperture parallel light source is driven by a reflecting mirror to scan a large-aperture objective lens to be measured, and the position of a detector is determined according to the state of a light spot on the detector, so that the focal plane of the objective lens to be measured is determined. Compared with the method for directly measuring the focal plane of a large-aperture objective lens to be measured by using a large-aperture parallel light pipe and a large-aperture plane mirror in the prior art, the method provided by the application is more economical, portable and convenient to operate, and has a wide application range and can be applied to the focal plane calibration of large-aperture objective lenses in various environments.

Description

Technical Field

[0001] This invention relates to a method for determining the focal plane of an objective lens, and more specifically to a method for calibrating the focal plane of a large-aperture objective lens using a small-aperture beam scanning. Background Technology

[0002] In existing technologies, determining the focal plane of large-aperture objectives (especially those with a light transmission diameter ≥ 400mm × 400mm) typically requires at least a large-aperture standard collimator with equivalent aperture and focal length. This is feasible for laboratory equipment. However, for large-aperture objectives used in the field or online, providing a large-aperture collimator and simultaneously connecting it to the device under test requires not only a large-aperture collimator but also a large beam bending space. This makes the focal plane calibration of large-aperture objectives very costly, and the calibration equipment is not portable, while the calibration process is complex.

[0003] In summary, the focal plane calibration of large-aperture objectives used in the field or online in the prior art has the disadvantages of high economic cost, inconvenient operation, and limited applicability. Summary of the Invention

[0004] The purpose of this invention is to solve the problems of high economic cost, inconvenient operation, and limited applicability in the focal plane calibration process of large-aperture objectives used in the field or online in the prior art. The invention provides a method for calibrating the focal plane of large-aperture objectives by scanning with a small-aperture beam.

[0005] The technical solution adopted in this invention is:

[0006] A method for calibrating the focal plane of a large-aperture objective lens using a small-aperture beam scanning is characterized by the following steps:

[0007] Step 1: Set up the calibration system;

[0008] The calibration system includes a small-aperture parallel light source and a reflector;

[0009] The reflector is positioned on the side of the objective lens to be tested away from the detector, and the center of the reflector coincides with the central axis of the objective lens to be tested. The direction of the emitted light from the small-aperture parallel light source is perpendicular to the central axis of the objective lens to be tested, and the reflector is located within the emitted light range of the small-aperture parallel light source.

[0010] Step 2: Guide the light emitted from the small-aperture parallel light source onto the reflector, adjust the orientation of the reflector so that the angle between the incident light and the reflected light is 90°, and make the center beam of the reflected light coincide with the optical axis of the objective lens under test. Use a detector to receive the light spot formed after refraction by the objective lens under test.

[0011] Step 3: Move the reflector along or in the opposite direction of the emitted light from the small-diameter parallel light source;

[0012] Step 4: Determine the state of the light spot on the detector and determine the current position of the detector. If the light spot does not move on the detector when the reflector moves in a straight line, the detector is at the focal plane, and the focal plane calibration is completed. Otherwise, adjust the position of the detector and return to Step 3 until the detector is at the focal plane, and the focal plane calibration is completed.

[0013] Furthermore, in step four, the adjustment of the detector's position is carried out according to the following rules:

[0014] a) When the direction of the light spot movement is the same as the direction of the mirror movement, increase the distance between the detector and the objective lens under test.

[0015] b) When the direction of the light spot movement is opposite to the direction of the mirror movement, reduce the distance between the detector and the objective lens under test.

[0016] Furthermore, in step one, the calibration system also includes a translation stage, on which the reflector is mounted. The translation stage moves in the direction of emission of the small-aperture parallel light source or in the opposite direction. The range of movement of the translation stage with the reflector can cover the aperture of the objective lens under test.

[0017] In step three, a translation stage is used to move the reflector along or in the opposite direction of the emitted light from the small-aperture parallel light source.

[0018] Furthermore, the translation stage is an electric translation stage.

[0019] Furthermore, in step one, the reflector is mounted on a support, which is mounted on a translation platform, and the azimuth and pitch angles of the reflector are adjusted by the support.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] This invention uses a moving mirror to drive the light emitted from a small-aperture parallel light source, after reflection, to scan a large-aperture objective lens under test. The position of the detector is determined based on the state of the light spot on the detector, thereby determining the focal plane of the objective lens under test. Compared with methods that use large-aperture collimators and large-aperture plane mirrors to directly measure the focal plane of a large-aperture objective lens under test, the method provided by this invention is more economical, portable, and easy to operate. It also has a wider range of applications and can be used for focal plane calibration of large-aperture objective lenses in various environments. Attached Figure Description

[0022] Figure 1 This is a schematic diagram illustrating the working principle of a method for calibrating the focal plane of a large-aperture objective lens using a small-aperture beam scanning according to the present invention.

[0023] Figure 2 This is a schematic diagram illustrating the detector position determination principle in a method for calibrating the focal plane of a large-aperture objective lens using a small-aperture beam scanning according to the present invention.

[0024] In the figure, 1-small aperture parallel light source, 2-reflector, 3-translation stage, 4-objective lens to be tested, 5-detector. Detailed Implementation

[0025] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0026] It should be noted that in this embodiment, the up, down, left, and right directions are all defined by... Figure 1 The orientation within the paper is described with reference to the orientation within the paper.

[0027] To address the inconvenience of calibrating the focal plane of large-aperture objectives using existing field equipment or online applications, this invention provides a method for calibrating the focal plane of large-aperture objectives using a small-aperture beam scanning. The focal plane calibration of large-aperture objectives can be completed using a small-aperture parallel light source and a small-aperture plane mirror.

[0028] The device under test in this invention includes a large-aperture objective lens 4 and a detector 5. The objective lens 4 is arranged in the vertical direction, and the detector 5 is located on the right side of the objective lens 4 to receive the refracted light from the objective lens 4.

[0029] like Figure 1 As shown, the present invention provides a method for calibrating the focal plane of a large-aperture objective lens using a small-aperture beam scanning, which is implemented according to the following steps:

[0030] Step 1: Set up the calibration system;

[0031] The calibration system includes a small-aperture parallel light source 1, a reflector 2 capable of two-dimensional angle adjustment for azimuth and pitch, and an electric translation stage 3 capable of covering the light-transmitting aperture of the objective lens 4 under test.

[0032] The reflector 2 is mounted on the translation stage 3. The emitting mirror 2 is a plane reflector. The translation stage 3, with the reflector 2 moving within its range, can cover the aperture of the objective lens 4 under test. The reflector 2 is positioned on the side of the objective lens 4 under test away from the detector 5 (i.e., the reflector 2 and the detector 5 are respectively positioned on the left and right sides of the objective lens 4 under test). In the initial state, the center of the reflector 2, the center of the objective lens 4 under test, and the center of the detector 5 coincide. The emission direction of the small-aperture parallel light source 1 and the movement direction of the translation stage 3 are the same (both along the up and down direction). The reflector 2 is located within the emission light range of the small-aperture parallel light source 1 and can completely reflect the parallel light beam emitted by the small-aperture parallel light source 1 onto the objective lens 4 under test.

[0033] Step 2: Guide the beam emitted from the small-aperture parallel light source 1 onto the reflector 2, adjust the orientation and pitch angle of the reflector 2 so that the angle between the incident light and the reflected light of the reflector 2 is 90° (i.e., the incident light of the reflector 2 is along the vertical direction, and the reflected light is along the horizontal direction), and make the center beam of the reflected light coincide with the optical axis of the objective lens 4 under test. Then, use the detector 5 to receive the light spot formed after refraction by the objective lens 4 under test.

[0034] Step 3: Move the mirror 2 linearly (i.e., along the vertical direction) by the translation stage 3 to achieve the purpose of scanning the reflected light through the mirror 2 along the vertical direction of the objective lens 4 under test.

[0035] Step 4: Determine the state of the light spot on detector 5 (there are three possible states: 1. The light spot moves in the same direction as the mirror 2; 2. The light spot moves in the opposite direction to the mirror 2; 3. The light spot does not move with the mirror 2), and determine the current position of detector 5; Figure 2 As shown, position S is the focal plane position (i.e., the target position of detector 5), position S1 is the front focal position, and position S2 is the back focal position. If the light spot does not move on detector 5 when mirror 2 moves in a straight line, then detector 5 is at the focal plane, and focal plane calibration is completed. Otherwise, adjust the position of detector 5 according to the following adjustment rules: a) When the movement direction of the light spot is the same as the movement direction of mirror 2, increase the distance between detector 5 and the objective lens 4 under test; b) When the movement direction of the light spot is opposite to the movement direction of mirror 2, decrease the distance between detector 5 and the objective lens 4 under test. Then return to step three until detector 5 is at the focal plane, and focal plane calibration is completed.

[0036] Furthermore, in step one, the reflector 2 is mounted on the support, which is mounted on the translation stage 3, and the orientation and pitch angle of the reflector 2 are adjusted through the support.

[0037] This invention uses a moving reflector 2 to drive the light emitted from a small-aperture parallel light source 1 after reflection by the reflector 2 to scan a large-aperture objective lens 4 under test. The position of the detector 5 is determined based on the state of the light spot on the detector 5, thereby determining the focal plane of the objective lens 4 under test. Compared with the method of directly measuring the focal plane of a large-aperture objective lens 4 using a large-aperture parallel light source and a large-aperture plane mirror, the method provided by this invention is more economical, portable, and easy to operate. At the same time, it has a wider range of applications and can be used for the focal plane calibration of large-aperture objective lenses in various environments.

Claims

1. A method for calibrating the focal plane of a large-aperture objective lens using a small-aperture beam scanning, characterized in that, Follow these steps: Step 1: Set up the calibration system; The calibration system includes a small-aperture parallel light source (1) and a reflector (2); The reflector (2) is located on the side of the objective lens (4) away from the detector (5), the center of the reflector (2) coincides with the central axis of the objective lens (4), the direction of the emitted light from the small-aperture parallel light source (1) is perpendicular to the central axis of the objective lens (4), and the reflector (2) is located within the emitted light range of the small-aperture parallel light source (1). Step 2: Guide the light emitted from the small-aperture parallel light source (1) onto the reflector (2), adjust the orientation of the reflector (2) so that the angle between the incident light and the reflected light is 90°, and make the center beam of the reflected light coincide with the optical axis of the objective lens (4) under test, and use the detector (5) to receive the light spot formed after refraction by the objective lens (4) under test; Step 3: Move the reflector (2) along or in the opposite direction of the emitted light from the small-diameter parallel light source (1); Step 4: Determine the state of the light spot on the detector (5) and determine the current position of the detector (5); if the light spot does not move on the detector (5) when the reflector (2) moves in a straight line, then the detector (5) is at the focal plane and the focal plane calibration is completed; otherwise, adjust the position of the detector (5) and return to step 3 until the detector (5) is at the focal plane and the focal plane calibration is completed.

2. The method for calibrating the focal plane of a large-aperture objective lens using a small-aperture beam scanning according to claim 1, characterized in that, In step four, the position of the detector (5) is determined according to the following rules: a) When the direction of movement of the light spot is the same as the direction of movement of the reflector (2), increase the distance between the detector (5) and the objective lens (4) to be tested. b) When the direction of movement of the light spot is opposite to the direction of movement of the reflector (2), reduce the distance between the detector (5) and the objective lens (4) under test.

3. The method for calibrating the focal plane of a large-aperture objective lens using a small-aperture beam scanning according to claim 2, characterized in that: In step one, the calibration system also includes a translation stage (3), the reflector (2) is mounted on the translation stage (3), the movement direction of the translation stage (3) is set along or opposite to the emission direction of the small-aperture parallel light source (1), and the movement range of the translation stage (3) with the reflector (2) can cover the light transmission aperture of the objective lens (4) under test. In step three, the translation stage (3) is used to move the reflector (2) along the direction of the emitted light from the small-diameter parallel light source (1) or in the opposite direction.

4. The method for calibrating the focal plane of a large-aperture objective lens using a small-aperture beam scanning according to claim 3, characterized in that: The translation stage (3) is an electric translation stage (3).

5. The method for calibrating the focal plane of a large-aperture objective lens using a small-aperture beam scanning according to claim 4, characterized in that: In step one, the reflector (2) is set on the bracket, and the bracket is set on the translation stage (3). The azimuth and pitch angle of the reflector (2) are adjusted by the bracket.

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