Method for measuring surface type of weak-rigidity free-form surface resin lens

Abstract

The invention belongs to the technical field of optical measurement, and particularly relates to a method for measuring the surface type of a weak-rigidity free-form surface resin lens, compared with the existing contact measurement technology, the method utilizes a white light sensor to obtain the surface height information of the free-form surface resin lens, avoids the deviation caused by contact measurement and the scratch to the surface of the resin lens, and improves the measurement accuracy. Automatic measurement is controlled through a program, batch detection of the free-form surface resin lens is achieved, the measurement period is shortened, and the problems that a traditional measurement method is prone to deformation and low in measurement precision are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of optical measurement, and in particular relates to a method for measuring the surface shape of a free-form surface resin lens with weak rigidity. Background Art

[0002] Helmet-mounted displays are information display terminals in modern military aircraft. Pilots need to obtain aircraft flight information and battlefield situation information through this display interface throughout the entire combat and flight process. Display goggles are an important component in the helmet aiming display system. Their surface shape directly affects the product imaging accuracy, which in turn affects the pilot's attack aiming accuracy.

[0003] The material of display goggles is polycarbonate (PC), which is made by one-piece injection molding. The injection molded parts have low rigidity and poor surface shape. Contact measurement will scratch the parts, and contact deformation will cause measurement errors. The fixed-length goggles interfere with the spherometer and cannot measure the spherical diameter. The goggles have a poor surface shape and cannot be measured by laser interferometer. At present, it is difficult to perform high-precision surface measurement on goggles, which seriously restricts the high-precision processing of display goggles.

[0004] In summary, it is of great significance to study the measurement of the surface shape of free-form resin lenses with weak stiffness. Summary of the invention

[0005] In view of this, the present invention provides a method for measuring the surface shape of a free-form resin lens with weak rigidity, which relies on a three-dimensional coordinate measuring machine and uses a non-contact probe to achieve automated and high-precision measurement of the surface shape of a free-form resin lens with weak rigidity by programming and planning the measurement path.

[0006] The technical solution of the present invention:

[0007] A method for measuring the surface shape of a free-form surface resin lens with weak rigidity comprises the following steps:

[0008] Step 1: Probe calibration: calibrate the main probe, based on the main probe positioning standard ball, obtain the diameter and position of the main probe; calibrate the working probe, obtain the diameter of the working probe tip, make radius compensation for the probe, and obtain the position relationship between the working probe and the main probe and the probe rod length relationship;

[0009] Step 2: Define the storage rack and set up automatic probe replacement;

[0010] Step 3: Establishing the detection coordinate system and establishing a safety plane: Based on the working probe, contact point marking is performed on the surface of the tooling where the lens is clamped, and a point, line and surface relationship on the outer surface of the tooling is established to determine the detection coordinate system; a safety plane is established to protect the probe from collision;

[0011] Step 4: Prepare the measurement process: plan the measurement path, determine the position and number of the nominal points to be measured on the part surface, consider the measurement edge effect, and set the distance between the nominal point and the part edge;

[0012] Step 5: Calibrate the probe: Set the working angle of the DotScan probe to measure the surface of the part in different areas. Calibrate the DotScan probe for each additional angle. If the working angle of the DotScan probe increases or there is an error in the non-contact measurement of the part surface, use a matte ball to recalibrate the DotScan probe at the working angle.

[0013] Step 6: Measurement: Measure the surface shape of the weak-rigidity free-form surface resin lens based on the defined measurement process.

[0014] Furthermore, before executing step 5, the following steps are also included: performing dark balance on the DotScan probe; and between step 4 and step 5, the following steps are also included: calibrating the DotScan probe based on a sub-photosphere.

[0015] Furthermore, in step 4, the method for defining the nominal points is:

[0016] Define the number of nominal points in the U and V directions for the face area and generate all the nominal points in the face area;

[0017] or,

[0018] The theoretical model of the lens is imported, and the surface of the theoretical model of the lens is sectioned according to a preset interval to form multiple intersection lines, and multiple sampling points are defined on the intersection lines, and each sampling point is used as a nominal point.

[0019] Furthermore, the surface shape measurement method of the free-form surface resin lens with weak rigidity also includes step 7: surface shape evaluation:

[0020] In step 6, the detection coordinate system obtained in step 3 is used to obtain a first surface error result, and in step 6, the detection coordinate system obtained in step 3 is not used to obtain a second surface error result;

[0021] The surface shape of the lens is jointly evaluated based on the first surface shape error result and the second surface shape error result.

[0022] Furthermore, in step 6, the switching between the contact probe and the non-contact probe is controlled by a program, and the automatic measurement of the lens is achieved according to a preset measurement trajectory.

[0023] Furthermore, in step 6, the scanning measurement rate of the DotScan probe is greater than 800 points / second; the resolution of the DotScan probe is better than 50nm;

[0024] The unidirectional length measurement error of the DotScan probe is better than 2.0+L / 350μm, where L is the longest dimension of the part.

[0025] Beneficial effects of the present invention:

[0026] The present invention utilizes a white light ranging sensor to obtain surface height information of a free-form surface resin lens, thereby avoiding deviations caused by contact measurement and scratches on the surface of the resin lens. By controlling automated measurement through a program, batch detection of free-form surface resin lenses is achieved, thereby shortening the measurement cycle and overcoming the problems of easy deformation and low measurement accuracy of traditional measurement methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0028] Figure 1 It is a schematic diagram of the measurement process of the present invention;

[0029] Figure 2 It is a schematic diagram of measuring the free-form surface resin lens of the goggles according to an embodiment of the present invention;

[0030] Figure 3 Schematic diagram of surface shape results of an embodiment of the present invention. DETAILED DESCRIPTION

[0031] The embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.

[0032] The following describes the embodiments of the present disclosure through specific examples, and those skilled in the art can easily understand other advantages and effects of the present disclosure from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all of the embodiments. The present disclosure can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present disclosure. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present disclosure.

[0033] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on the present disclosure, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects described herein can be used to implement the device and / or practice the method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this device and / or practice this method.

[0034] It should also be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present disclosure. The illustrations only show components related to the present disclosure rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0035] Additionally, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, it will be understood by those skilled in the art that the aspects described may be practiced without these specific details.

[0036] In one embodiment of the present invention, a method for measuring the surface shape of a free-form surface resin lens with weak rigidity is provided. Figure 1 As shown, the following steps are included:

[0037] Step 1: Probe calibration: calibrate the main probe, based on the main probe positioning standard ball, obtain the diameter and position of the main probe; calibrate the working probe, obtain the diameter of the working probe tip, make radius compensation for the probe, and obtain the position relationship between the working probe and the main probe and the probe rod length relationship;

[0038] Step 2: Define the storage rack and set up automatic probe replacement;

[0039] Step 3: Establishing the detection coordinate system and establishing a safety plane: Based on the working probe, contact point marking is performed on the surface of the tooling where the lens is clamped, and a point, line and surface relationship on the outer surface of the tooling is established to determine the detection coordinate system; a safety plane is established to protect the probe from collision;

[0040] Step 4: Prepare the measurement process: plan the measurement path, determine the position and number of the nominal points to be measured on the part surface, consider the measurement edge effect, and set the distance between the nominal point and the part edge;

[0041] Step 5: Calibrate the probe: Set the working angle of the DotScan probe to measure the surface of the part in different areas. Calibrate the DotScan probe for each additional angle. If the working angle of the DotScan probe increases or there is an error in the non-contact measurement of the part surface, use a matte ball to recalibrate the DotScan probe at the working angle.

[0042] Step 6: Measurement: Measure the surface shape of the weak-rigidity free-form surface resin lens based on the defined measurement process.

[0043] In this embodiment, before executing step 5, the following steps are also included: performing dark balance on the DotScan probe; and between step 4 and step 5, the following steps are also included: calibrating the DotScan probe based on a sub-photosphere.

[0044] In this embodiment, in step 4, the method of defining the nominal points is:

[0045] Define the number of nominal points in the U and V directions for the face area and generate all the nominal points in the face area;

[0046] or,

[0047] The theoretical model of the lens is imported, and the surface of the theoretical model of the lens is sectioned according to a preset interval to form multiple intersection lines, and multiple sampling points are defined on the intersection lines, and each sampling point is used as a nominal point.

[0048] In this embodiment, the method for measuring the surface shape of a free-form surface resin lens with weak rigidity further includes step 7: surface shape evaluation

[0049] In step 6, the detection coordinate system obtained in step 3 is used to obtain a first surface error result, and in step 6, the detection coordinate system obtained in step 3 is not used to obtain a second surface error result;

[0050] The surface shape of the lens is jointly evaluated based on the first surface shape error result and the second surface shape error result.

[0051] In this embodiment, in step 6, the switching between the contact probe and the non-contact probe is controlled by a program, and the automatic measurement of the lens is achieved according to a preset measurement trajectory.

[0052] In this embodiment, in step 6, the scanning measurement rate of the DotScan probe is greater than 800 points / second; the resolution of the DotScan probe is better than 50nm;

[0053] The unidirectional length measurement error of the DotScan probe is better than 2.0+L / 350μm, where L is the longest dimension of the part.

[0054] This embodiment can be described as follows:

[0055] Step 1: Calibrate the main probe and the working probe. Position the main probe with the standard ball to obtain the diameter and position of the main probe (set the zero position and use it as a reference for the working probe), that is, (X:0, Y:0, Z:0). The main probe is not used for measurement, but only for calibration. Reference ball 1, i.e., the matte ball, is used to calibrate the Dotscan probe, and reference ball 2 is used to calibrate the working probe. Create a working probe, calibrate the working probe with the standard ball, obtain the diameter of the working probe, and make radius compensation for the probe; obtain the relationship between the probe and the main probe (including position, probe rod length, etc.);

[0056] Step 2: Define the storage rack: Define the storage rack for automatic replacement between probes;

[0057] Step 3: Establish the detection coordinate system and safety plane. The establishment of the coordinate system should comply with the right-hand rule. The simplest method is to determine the coordinate system by plane, point, and line. The plane is determined by 4 points on the first plane, the line is determined by 2 points on the second plane, and the point is determined by a single point on the third plane. When establishing the coordinate system, try to make the coordinate system you establish consistent with the machine coordinate system in direction. The purpose of establishing the safety plane is to enable the measuring machine to move the probe around the workpiece in the CNC state without collision, and to protect the probe from collision;

[0058] Step 4: Prepare the measurement program: Plan the measurement path, use the surface generation point or cross-section line definition point method to determine the position and number of the nominal points to be measured on the part surface, consider the edge effect of the measurement, and set the distance between the nominal point and the part edge. Surface generation point method: Click the model surface to be measured, select the number of rows and columns to generate nominal points, define the distance between the nominal edge point and the part edge, and create points. You can manually modify the number of points and the order of points later to determine the nominal points; cross-section method: Select a certain direction plane to intercept the surface of the part to be measured, generate a cross-section, define the number of cross-section points and the distance between the edge point and the part edge, and create points. Repeat this method to create multiple cross-sections to determine the nominal points, and retrieve the cross-section data through the surface to evaluate the surface shape data of the part.

[0059] Step 5: Calibrate the probe: 1) The probe is dark balanced in an environment without a physical object to be measured. The purpose is to measure the error caused by the reflected light in the filter environment during the formal part process.

[0060] 2) Using a matte ball, the light emitted by the probe is diffusely reflected on the surface of the matte ball, and the DotScan probe is calibrated by receiving the reflected light. At the same time, according to the shape of different parts, ensure that the probe can receive the reflected light from the surface of the part;

[0061] 3) The DotScan probe is set to work at different angles to measure the surface of the part. Each time an angle is added, the DotScan probe must be calibrated at each angle to ensure the accuracy of the measurement at each angle. If the working angle is increased or some points are reported as errors and cannot be measured during the non-contact measurement of the part surface, the DotScan probe at the working angle needs to be recalibrated using a matte ball;

[0062] Step 6: Measurement: Automatic measurement of the free-form surface of the resin lens with weak rigidity is achieved through program control.

[0063] A 236*125*215mm weak rigidity free-form surface resin lens is selected for measurement experiment. The weak rigidity free-form surface resin lens described in this embodiment has a shape as follows: Figure 2 As shown, the surface accuracy requirement is PV≤80μm.

[0064] Follow the steps below Figure 1 The embodiment is measured by the steps of:

[0065] Step 1: Calibrate the probe:

[0066] 1) The main probe is positioned on the standard ball to obtain the diameter and position of the main probe (set the zero position to serve as a reference for the working probe), i.e. (X:0, Y:0, Z:0). The main probe is not used for measurement, but only for calibration;

[0067] 2) Reference ball 1, i.e., the matte ball, is used to calibrate the Dotscan probe, and reference ball 2 is used to calibrate the working probe. The working probe is calibrated with the standard ball to obtain the probe diameter, and the probe is compensated for the radius; the relationship between the probe and the main probe (including position, probe rod length, etc.) is obtained;

[0068] Step 2: Define the storage location:

[0069] Define the storage rack and set the contact probe and non-contact DotScan probe storage locations;

[0070] Step 3: Establish the detection coordinate system and create a safety plane:

[0071] 1) The establishment of the coordinate system should comply with the right-hand rule. The simplest method is to determine the coordinate system by surface, point, and line. The working contact probe touches the detection surface to make points. Surface 1 makes 4 points to determine the surface, surface 2 makes 2 points to determine the line, and surface 3 makes 1 point to determine the point. The detection coordinate system is determined by points, lines, and surfaces. Try to make the coordinate system you establish consistent with the machine coordinate system in direction;

[0072] 2) Add a certain distance outward from the parts and the inspection tooling to establish a safety plane, so that the measuring machine can move the probe around the workpiece in the CNC state without collision, protecting the probe from collision;

[0073] Step 4: Establish the detection coordinate system:

[0074] Step 4: Prepare the measurement process:

[0075] Six working angles are set for the measured viewing area, and the surface generation point or cross-section line definition point method is adopted to determine the position and number of the nominal points to be measured on the surface of the part. In the embodiment, 50 lines are set with a line spacing of 5 mm, a total of 1068 nominal points are set with a point spacing of 2 mm. Considering the measurement edge effect, the distance between the nominal point and the edge of the part is set to 4 mm;

[0076] Step 5: Calibrate the probe:

[0077] 1) The probe is dark balanced in an environment without a physical object to be measured;

[0078] 2) Using a matte sphere, the light emitted by the probe is diffusely reflected on the surface of the matte sphere, and the DotScan probe is calibrated by receiving the reflected light.

[0079] 3) The DotScan probe is calibrated at 6 angles to ensure the accuracy of measurement at each angle. If the working angle is increased or some points are reported as errors and cannot be measured during the non-contact measurement of the part surface, the DotScan probe at the working angle needs to be recalibrated using a matte ball;

[0080] Step 6: Measurement: Automatic measurement of the free-form surface of the resin lens with weak rigidity is achieved through program control.

[0081] The above is only a specific implementation of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present disclosure should be included in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be based on the protection scope of the claims.

Claims

1. A method for measuring the surface shape of a free-form surface resin lens with weak rigidity, characterized in that: The steps include: Step 1: Probe calibration: calibrate the main probe, based on the main probe positioning standard ball, obtain the diameter and position of the main probe; calibrate the working probe, obtain the diameter of the working probe tip, make radius compensation for the probe, and obtain the position relationship between the working probe and the main probe and the probe rod length relationship; Step 2: Define the storage rack and set up automatic probe replacement; Step 3: Establishing a detection coordinate system and a safety plane: Based on the working probe, contact point marking is performed on the surface of the tooling where the lens is clamped, and a point, line and surface relationship on the outer surface of the tooling is established to determine the detection coordinate system; Establish a safety plane to protect the probe from collision; Step 4: Prepare the measurement process: plan the measurement path, determine the position and number of the nominal points to be measured on the part surface, consider the measurement edge effect, and set the distance between the nominal point and the part edge; Step 5: Calibrate the probe: Set the working angle based on the DotScan (white light confocal / white light ranging sensor) probe to measure the part surface in different areas. Calibrate the DotScan probe for each additional angle. If the working angle of the DotScan probe increases or there is an error in the non-contact measurement of the part surface, use a sub-light ball to recalibrate the DotScan probe at the working angle. Step 6: Measurement: Measure the surface shape of the weak-rigidity free-form surface resin lens based on the defined measurement process.

2. The method for measuring the surface shape of a free-form surface resin lens with weak rigidity according to claim 1, characterized in that: Before executing step 5, the method further includes the following steps: performing dark balance on the DotScan probe; and between step 4 and step 5, the method further includes the following steps: calibrating the DotScan probe based on a sub-photosphere.

3. The method for measuring the surface shape of a free-form surface resin lens with weak rigidity according to claim 2, characterized in that: In step 4, the method of defining the nominal points is: Define the number of nominal points in the U and V directions for the face area and generate all the nominal points in the face area; or, The theoretical model of the lens is imported, and the surface of the theoretical model of the lens is sectioned according to a preset interval to form multiple intersection lines, and multiple sampling points are defined on the intersection lines, and each sampling point is used as a nominal point.

4. The method for measuring the surface shape of a free-form surface resin lens with weak rigidity according to claim 3, characterized in that: The surface shape measurement method of the weak-rigidity free-form surface resin lens also includes step 7: surface shape evaluation: In step 6, the detection coordinate system obtained in step 3 is used to obtain a first surface error result, and in step 6, the detection coordinate system obtained in step 3 is not used to obtain a second surface error result; The surface shape of the lens is jointly evaluated based on the first surface shape error result and the second surface shape error result.

5. The method for measuring the surface shape of a free-form surface resin lens with weak rigidity according to claim 4, characterized in that: In step 6, the switching between the contact probe and the non-contact probe is controlled by a program, and the automatic measurement of the lens is achieved according to a preset measurement trajectory.

6. The method for measuring the surface shape of a free-form surface resin lens with weak rigidity according to claim 5, characterized in that: In step 6, the scanning measurement rate of the DotScan probe is greater than 800 points / second; the resolution of the DotScan probe is better than 50nm; The unidirectional length measurement error of the DotScan probe is better than 2.0+L / 350μm, where L is the longest dimension of the part.

Images