A method for detecting the parfocality and eccentricity of a microscope objective lens

Abstract

The invention discloses a device and method for detecting the parfocality and eccentricity of a microscope objective lens. By arranging a standard grid plate on a stage that can move up and down and an objective lens holder that can rotate around an optical axis, the parfocality and eccentricity of the objective lens can be detected simultaneously without disassembling the objective lens multiple times, and the detection efficiency and detection accuracy are greatly improved. The time for detecting the parfocality and eccentricity of an objective lens is reduced from about 40 seconds to about 20 seconds. According to the GRR repeatability analysis, the repeatability is 19.8%, which is 30% of the repeatability of a manual parfocality device, and the detection accuracy is also greatly improved.

Description

Technical Field

[0001] The invention relates to error detection of a microscope objective lens, and in particular to a method for detecting parfocality and eccentricity of a microscope objective lens. Background Art

[0002] The eccentricity and parfocality of microscope objective lenses are one of the key quality indicators of microscopes. It requires that the optical axes of each objective lens should coincide and the imaging should be consistent. Moreover, the objective lenses of the same model should be interchangeable. However, due to manufacturing errors, the conjugate distances between the images of each objective lens cannot be absolutely equal, and there will always be some deviations.

[0003] The typical device for existing parfocality detection is a transmissive optical path. The light source passes through a condenser and is focused on the cross-reticle plate on the stage. The image is formed in the human eye through a standard objective lens and a standard eyepiece to determine the parfocal position at this time. Then, a lever-type micrometer pointer is placed on the stage and the reading is reset to zero. Then, at the same hole position, another objective lens is replaced and adjusted to a clear state. The micrometer reading is read again, which is the parfocality error. Due to the error of the human eye, the parfocality error detected by this method is not particularly high.

[0004] The existing method for detecting the eccentricity of the objective lens is to use an eccentricometer to detect it. The objective lens to be tested is placed on a special tooling, and the working distance is adjusted so that the cross-reticle plate below the eccentricometer is imaged on the CCD lens. The motor of the eccentricometer drives the tooling and the objective lens to rotate, and the cross-reticle plate will rotate along with the rotation of the objective lens to be tested. At this time, the corresponding rotation radius can be read, and then the eccentricity value of the objective lens to be tested can be calculated based on the magnification. Due to the different weights of objective lenses of different specifications, the motor may not be able to drive it. At this time, the employee needs to manually rotate the objective lens to be tested. Due to the uneven manual rotation force, the trajectory of the cross-reticle plate movement will drift, affecting the judgment of the eccentricity value.

[0005] At present, when performing the parfocality and eccentricity detection of the objective lens, the minimum grid value of the cross-reticle plate used is different at different magnifications. Only by using a matching cross-reticle plate can the best effect be obtained. The observer needs to switch the cross-reticle plate when detecting the objective lenses of different magnifications. And each time the cross-reticle plate is switched, the observer needs to find the cross-cross position before observation. The current cross-reticle plate is prone to blurring, aberration and other problems when observing with a high-power objective lens, which affects the observer's judgment. In addition, the existing detection devices all detect the parfocality or eccentricity of the objective lens separately. During the detection process, the objective lens needs to be disassembled many times, which is inconvenient to operate. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method for detecting the parfocality and eccentricity of a microscope objective lens, which can simultaneously detect the parfocality and eccentricity of the objective lens without disassembling the objective lens multiple times, avoids the error of the human eye, and has greatly improved detection efficiency and detection accuracy.

[0007] The technical solution adopted by the present invention to solve the above technical problems is: a device for detecting the focus and eccentricity of a microscope objective lens, comprising a frame and a control device, the frame comprising a base at a lower part and a detection platform at an upper part, the base being provided with a light source, a detection seat being fixedly provided on the detection platform, an image receiving device being provided on the detection seat, the image receiving device being connected to the control device for processing an image signal sent by the image receiving device, a stage being provided between the base and the detection platform, a detection hole being provided on the stage, a standard grid plate being provided on the detection hole, a lifting drive device being provided on the stage, the lifting drive device being controlled by the control device to drive the stage to move up and down, an objective lens holder capable of rotating around an optical axis being provided in the detection seat, the objective lens holder being provided with a rotation drive device, the rotation drive device being controlled by the control device to drive the objective lens holder to rotate around the optical axis, the light emitted by the light source passing through the detection hole and the objective lens on the objective lens holder sends the image of the standard grid plate to the image receiving device.

[0008] The detection method using the above-mentioned microscope objective lens parfocality and eccentricity detection device comprises the following steps:

[0009] Step 1: Adjust the light source to evenly illuminate the standard grid plate;

[0010] Step 2: according to the specification parameters of the objective lens to be inspected, a reference objective lens is mounted on the objective lens holder, so that the light source passes through the standard grid plate and then passes through the reference objective lens, and the image receiving device receives the standard image of the standard grid plate;

[0011] Step 3: The control device controls the lifting drive device to move the stage up and down so that the image receiving device obtains the clearest standard image of the standard grid plate, and records the position of the stage corresponding to the clearest standard image;

[0012] Step 4: Replace the reference objective lens with the objective lens to be inspected, and control the lifting drive device by the control device to move the stage up and down so that the image receiving device can obtain the clearest inspection image of the standard grid plate, and move the stage to the position corresponding to the clearest inspection image by the control device;

[0013] Step 5: Compare the position of the stage corresponding to the clearest detection image with the position of the stage corresponding to the clearest standard image to obtain the parfocal error of the objective lens to be inspected;

[0014] Step 6: When the stage is located at the position corresponding to the clearest detection image, the control device controls the rotation drive device to make the objective lens holder rotate one circle around the optical axis to obtain the eccentricity error of the objective lens to be tested.

[0015] Compared with the prior art, the advantage of the present invention is that the structure is simple. By setting a standard grid plate on a stage that can move up and down and an objective lens holder that can rotate around the optical axis, the objective lens can be simultaneously detected for parfocality and eccentricity without disassembling the objective lens multiple times, and the detection efficiency and detection accuracy are greatly improved. The time for detecting the parfocality and eccentricity of an objective lens is reduced from about 40 seconds to about 20 seconds. According to the GRR (Gauge Repeatability and Reproducibility measurement system repeatability and reproducibility) repeatability analysis, the repeatability is 19.8%, which is 30% higher than the repeatability of the manual parfocality device, and the detection accuracy is also greatly improved.

[0016] The detection device of the present invention is simple to operate and easy to use, does not require complicated training, and the test time varies with the proficiency of the user, which can greatly improve the efficiency.

[0017] Preferably, the rotation driving device comprises a motor fixedly mounted on the detection platform, a synchronous pulley is arranged on the rotating shaft of the motor, and a belt is arranged on the synchronous pulley for connecting with the objective lens holder to drive the objective lens holder to rotate.

[0018] Preferably, the image receiving device comprises a CCD camera fixedly mounted on the detection seat, and an imaging lens is arranged in front of the CCD camera. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the three-dimensional structure of the detection device according to an embodiment of the present invention;

[0020] Figure 2 It is a schematic diagram of the planar structure of the rotation driving device in the detection device according to an embodiment of the present invention;

[0021] Figure 3 It is a schematic diagram of the three-dimensional structure of the base and the stage in the detection device according to the embodiment of the present invention;

[0022] Figure 4 A schematic diagram of the optical path of a detection device according to an embodiment of the present invention;

[0023] Figure 5 Schematic diagram of a clear image plane determined by software in step three and step four of the detection method according to an embodiment of the present invention;

[0024] Figure 6 The figure is a judgment function curve diagram of the clarity judgment by the software in step 3 and step 4 of the detection method according to the embodiment of the present invention;

[0025] Figure 7 This is a flowchart of the clarity calculation of step three and step four in the detection method of an embodiment of the present invention;

[0026] Figure 8 This is a flow chart of eccentricity calculation in step six of the detection method according to an embodiment of the present invention.

[0027] Numbers in the figure: 1-frame, 11-base, 12-detection platform, 13-light source; 2-detection seat; 3-image receiving device, 31-CCD camera; 4-stage, 41-detection hole; 5-standard grid plate; 6-objective lens holder; 7-rotation drive device, 71-motor, 72-synchronous pulley, 73-belt; 8-objective lens; 9-imaging lens. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below with reference to the accompanying drawings.

[0029] Example: Figure 1~Figure 4As shown, a device for detecting the focus and eccentricity of a microscope objective lens comprises a frame 1 and a control device (not shown in the figure), the frame 1 comprises a base 11 at the bottom and a detection platform 12 at the top, the base 11 is provided with a light source 13, a detection seat 2 is fixedly provided on the detection platform 12, an image receiving device 3 is provided on the detection seat 2, the image receiving device 3 comprises a CCD camera 31 fixedly provided on the detection seat 2 and an imaging lens 9 provided in the detection seat 2 and located in front of the CCD camera 31, the control device is connected to the CCD camera 31 for processing the image signal sent by the CCD camera 31, and the base 11 and the detection platform 12 are connected. A stage 4 is provided, a detection hole 41 is provided on the stage 4, a standard grid plate 5 is provided on the detection hole 41, a lifting drive device (not shown) is provided on the stage 4, and the lifting drive device is controlled by a control device to drive the stage 4 to move up and down. An objective lens holder 6 capable of rotating around an optical axis is provided in the detection seat 2, and the objective lens holder 6 is provided with a rotation drive device 7, and the rotation drive device 7 includes a motor 71 fixedly provided on the detection platform 12, and a synchronous pulley 72 is provided on the rotating shaft of the motor 71, and a belt 73 for connecting with the objective lens holder 6 to drive the objective lens holder 6 to rotate is provided on the synchronous pulley 72. The motor 71 is controlled by the control device to drive the objective lens holder 6 to rotate around the optical axis, and the light emitted by the light source 13 passes through the detection hole 41 and the objective lens 8 on the objective lens holder 6 to transmit the image of the standard grid plate 5 to the CCD camera 31.

[0030] The method for detecting the parfocality and eccentricity of a microscope objective lens using the detection device of this embodiment specifically comprises the following steps:

[0031] Step 1: Make sure the device is in working state, and adjust the light source 13 to evenly illuminate the standard grid plate 5;

[0032] Step 2: According to the specification parameters of the objective lens to be inspected, a reference objective lens is installed on the objective lens holder 6, that is, the objective lens 8 at this time is the reference objective lens, and the light from the light source 13 passes through the standard grid plate 5, and then passes through the reference objective lens and the imaging lens 9, so that the standard image of the standard grid plate 5 is imaged on the chip surface of the CCD camera 31;

[0033] Step 3: The control device controls the lifting drive device to move the stage 4 downward away from the reference objective lens, or to move it all the way to the lowest position that can be reached, and then the control device controls the lifting drive device to move the stage 4 upward according to a preset moving range, or to move it all the way to the highest position that can be reached. During the movement, a series of images are captured by the CCD camera 31 and sent to the control device. The software in the control device automatically calculates and obtains the clearest standard image of the standard grid plate 5 according to the algorithm, and records the position of the stage corresponding to the clearest standard image, and obtains the coordinate data of the position;

[0034] Step 4: Replace the reference objective lens with the objective lens to be inspected. At this time, the objective lens 8 is the objective lens to be inspected. The control device controls the lifting drive device to move the stage 4 downward away from the objective lens to be inspected, or it can be moved all the way to the lowest position that can be reached. Then the control device controls the lifting drive device to move the stage 4 upward according to the preset moving range, or it can be moved all the way to the highest position that can be reached. During the movement, a series of images are captured by the CCD camera 31 and sent to the control device. The software in the control device automatically calculates and obtains the clearest detection image of the standard grid plate 5 according to the algorithm, and the control device moves the stage 4 to the position corresponding to the clearest detection image, and records the position of the stage 4 corresponding to the clearest detection image to obtain the coordinate data of the position.

[0035] Step 5: The software in the control device automatically compares the position coordinate data of the stage 4 corresponding to the clearest detection image with the position coordinate data of the stage 4 corresponding to the clearest standard image, thereby obtaining the parfocal error of the objective lens to be inspected;

[0036] Step six: When the stage 4 is located at the position corresponding to the clearest detection image, the control device controls the motor 71 to rotate so that the objective lens holder 6 rotates one circle around the optical axis. During the rotation, a series of images are captured by the CCD camera 31 and sent to the control device. The software in the control device automatically calculates the eccentricity error of the objective lens to be inspected according to the algorithm.

[0037] The software and algorithms in the control device in each step of the above method can utilize the software and algorithms used in the microscope surface imaging system in the prior art.

[0038] The following is a simple example for this embodiment. Figure 5 This is a schematic diagram of the software judging the clear image plane. Figure 6 This embodiment is to judge the clarity by judging the image clarity and aligning the focal distance. When the image is in the clearest state, it must correspond to the focal plane position of the objective lens. The clarity of the image is judged by a specific algorithm to complete the judgment of the best image plane.

[0039] Figure 7 is the clarity calculation flow chart. First, obtain a set of images, a total of N1 images, denoted as image set I. The serial number of each image is I k , k ∈[1,N1]. Then, calculate the clarity of each image, denoted as F k . Find the maximum resolution, recorded as F k _ max , the focal plane corresponding to the image at this clarity is the optimal focal plane, denoted as Z best. The expression for calculation using the Laplace operator is In the formula I k Represents the sequence number of the picture. h Represents the height of the image. w Represents the width of the image, which is composed of several pixels. In addition, i Represents the row number of the pixel in the image, j Represents the column number of the pixel in the image. F k At maximum, the image is clearest.

[0040] Figure 8 This is a flow chart of eccentricity calculation. Based on the definition calculation, the center point of the image is obtained. The motor 71 is used to control the rotation of the objective lens to be tested, and the center point of the cross image will move accordingly. When the center point moves, the position of each center point is recorded, and the motion trajectory is fitted into a circle. The distance from the center of the circle to the edge of the circle can be obtained using the least squares method.

[0041] The standard grid plate 5 is a grid graticule plate with dark field bright lines. When measuring the parfocality of objective lenses of different magnifications, the observer only needs to ensure that there is only one cross line in the field of view to perform the measurement. When performing high-magnification observation, the imaging edge of the dark field bright line slice is sharper than that of the ordinary slice, and the imaging is relatively clear, which is convenient for algorithm judgment.

Claims

1. A method for detecting the parfocality and eccentricity of a microscope objective lens, wherein the detection device used comprises a frame and a control device, wherein the frame comprises a base at a lower portion and a detection platform at an upper portion, wherein the base is provided with a light source, a detection seat is fixedly provided on the detection platform, an image receiving device is provided on the detection seat, the control device is connected to the image receiving device for processing an image signal sent by the image receiving device, a stage is provided between the base and the detection platform, a detection hole is provided on the stage, a standard grid plate is provided on the detection hole, a lifting drive device is provided on the stage, the lifting drive device is controlled by the control device to drive the stage to move up and down, an objective lens holder capable of rotating around an optical axis is provided in the detection seat, the objective lens holder is provided with a rotation drive device, the rotation drive device is controlled by the control device to drive the objective lens holder to rotate around the optical axis, the light emitted by the light source passes through the detection hole and the objective lens provided on the objective lens holder to send the image of the standard grid plate to the image receiving device, characterized in that The following steps are involved: Step 1: Adjust the light source to evenly illuminate the standard grid plate; Step 2: according to the specification parameters of the objective lens to be inspected, a reference objective lens is mounted on the objective lens holder, so that the light from the light source passes through the standard grid plate and then passes through the reference objective lens, and the image receiving device receives the standard image of the standard grid plate; Step 3: The control device controls the lifting drive device to drive the stage to move up and down, so that the image receiving device obtains the clearest standard image of the standard grid plate, and records the position of the stage corresponding to the clearest standard image; Step 4: Replace the reference objective lens with the objective lens to be inspected and install it on the objective lens holder, and control the lifting drive device to drive the stage to move up and down, so that the image receiving device obtains the clearest inspection image of the standard grid plate, and the control device moves the stage to the position corresponding to the clearest inspection image; Step 5: Compare the position of the stage corresponding to the clearest detection image with the position of the stage corresponding to the clearest standard image to obtain the parfocal error of the objective lens to be inspected; Step 6: When the stage is located at the position corresponding to the clearest detection image, the control device controls the rotation drive device to make the objective lens holder rotate one circle around the optical axis to obtain the eccentricity error of the objective lens to be tested.

2. A method for detecting parfocality and eccentricity of a microscope objective lens as claimed in claim 1, characterized in that: The rotation driving device comprises a motor fixedly arranged on the detection platform, a synchronous pulley is arranged on the rotating shaft of the motor, and a belt for connecting with the objective lens holder to drive the objective lens holder to rotate is arranged on the synchronous pulley.

3. A method for detecting parfocality and eccentricity of a microscope objective lens as claimed in claim 1, characterized in that: The image receiving device comprises a CCD camera fixedly arranged on the detection seat, and an imaging lens is arranged in front of the CCD camera.

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