A method for controlling the optical axis by polishing the surface of a cemented lens

Abstract

The application discloses a method for controlling optical axes by polishing the surface of cemented lenses, which comprises the following steps: placing the cemented lens group on a rotating platform, measuring the reference lens, adjusting the rotating platform to make its radial runout tend to zero, and determining the mechanical center axis; measuring the cemented lens to obtain the inclination data of each optical axis, setting the optical axis of the reference lens as the reference axis, i.e. the angle between the reference axis and the mechanical center axis is zero; checking the inclination values of the optical axes of other lenses and marking the directions thereof; using a grinding tool to polish the corresponding positions of the lens surface, and reducing the angle between the optical axes of the remaining lenses and the optical axis of the reference lens / mechanical center axis by controlling the lens surface, so as to meet the inclination index requirements. The cemented lens cementing precision index is measured by using a high-precision centering instrument, if the optical axis inclination is out of tolerance, the inclination direction is marked, the lens surface is polished, and the surface shape is controlled by using a sample lens, and the optical axis inclination data is reduced to meet the cementing precision requirements.

Description

Technical Field

[0001] This invention belongs to the field of precision optical lens processing and inspection. It is mainly applicable to repairing and polishing lens surfaces in specific directions to change the optical axis tilt, and is particularly suitable for repairing and polishing multi-cemented lenses. Background Technology

[0002] In optical system design, cemented lenses are used to minimize or eliminate chromatic aberration and also help to minimize spherical aberration. The manufacturing process of cemented lenses involves cementing two or more lenses together. With the development of modern optical technology, cemented lenses are increasingly widely used in optical systems due to their superior optical performance. Cemented lenses are composed of multiple individual lenses cemented together. The optical performance of multi-cemented lenses is mainly evaluated based on the accuracy of the cemented optical axis (e.g., eccentricity better than 5μm, tilt better than 15 arcseconds) and coaxiality better than 5μm (by using one lens as a reference and measuring the coaxiality of the other lenses with respect to the reference lens). Existing processes can achieve the eccentricity and coaxiality requirements. However, because the curved surfaces of the lenses slide relative to each other during the cementing process, it can be considered that the cemented surface of the lens deflects around the center at a specific angle in the cemented area. In particular, lenses with different surface shapes have different sensitivities to sliding. Therefore, when high cementing performance is required (e.g., tilt values ​​are required to be better than 10 arcseconds), the tilt caused by the relative sliding of the lenses often exceeds the tolerance. There are generally two methods for representing the optical axis of a cemented lens: 1) One method is to approximate the optical axis of the cemented lens with the optical axes of the individual lenses it composes, which requires the use of an algorithm for fitting; 2) Another method is to set the optical axis of a certain lens as the reference zero position, that is, it coincides with the rotation axis (the included angle is zero), and measure the tilt data of the optical axes of the other lenses to see if they meet the cementing accuracy index of the cemented lens.

[0003] Currently, the measurement of cemented lenses faces the following problems:

[0004] 1) Regardless of the measurement method used for the optical axis of the cemented lens (fitting the equivalent optical axis / setting a certain optical axis as the reference zero point and measuring the tilt data of the other optical axes), there is a risk of the cementing accuracy being out of tolerance.

[0005] 2) When the tilt measurement data of the cemented lens is out of tolerance, the general solution is to de-glue it at high temperature and then re-glue it. This not only reduces work efficiency (re-glueing takes more than 12 hours), but also poses a risk of edge chipping and breakage of the lens during the high-temperature de-glueing process (especially in the edge area of ​​the cemented surface).

[0006] 3) After re-gluing, the optical axis data of the glued lens needs to be measured again, and there is still a possibility of out-of-tolerance.

[0007] In summary, the bonding accuracy should be maximized during gluing. If the measured value exceeds the tolerance, other methods should be used to reduce the optical axis tilt value. Summary of the Invention

[0008] To overcome the problems existing in the prior art, namely the problem of out-of-tolerance optical axis tilt data of multi-cemented lenses, the present invention provides a method for controlling the optical axis by repairing and polishing the surface of the cemented lens.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] A method for controlling the optical axis by polishing the surface of a cemented lens includes:

[0011] Step 1: Place the cemented lens assembly on a rotating platform, measure the outer circle and horizontal end face of the reference lens in the cemented lens assembly, adjust the rotating platform so that its radial runout tends to 0μm, and determine the mechanical center axis;

[0012] Step 2: Measure the cemented lens to obtain the tilt data of each optical axis, and set the optical axis of the reference lens as the reference axis, that is, the angle between the reference lens and the mechanical center axis is zero;

[0013] Step 3: Check the tilt values ​​of the optical axes of other lenses and mark their directions;

[0014] Step 4: Use a polishing tool to polish the corresponding positions on the lens surface. By controlling the lens surface, the angle between the optical axis of the other lenses and the optical axis of the reference lens / mechanical center axis is reduced to meet the tilt index requirements.

[0015] Furthermore, in step 1, a roundness meter is used to measure the radial runout of the outer circle of the lens and the platform is adjusted to make its value zero.

[0016] Furthermore, in step 2, a high-precision centering instrument is used to measure the cemented lenses, and one of the lenses is designated as the reference lens. The angle between the optical axis of the remaining lenses and the optical axis of the reference lens is measured.

[0017] Furthermore, in step 3, check the tilt values ​​of the optical axes of other lenses. If they are out of tolerance, mark the tilt direction.

[0018] Furthermore, step 4 specifically includes:

[0019] Step 4-1: Using drawing software, slide the lens on the cemented surface at the corresponding angle according to the optical axis tilt angle, and then calculate the edge thickness difference;

[0020] If the thickness difference is too large, that is, the sliding angle is too large, it means that the amount of polishing is huge and the amount of thickness removal in the center is too large and exceeds the tolerance, so the glue is re-glued; if the amount of polishing is within the tolerance range, the polishing tool is used to polish the inclined direction, and the amount of polishing is the edge thickness difference, and the aperture number is controlled by the template mirror to control the surface shape.

[0021] Step 4-2: After polishing, use a high-precision centering instrument to repeatedly measure the optical axis tilt data. If it exceeds the tolerance, return to step 2. If it meets the bonding index requirements, then finish polishing.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] This invention discloses a method for controlling the optical axis by polishing the surface of a cemented lens. The method involves using a high-precision centering instrument to measure the cementing accuracy indicators (coaxiality, eccentricity, and optical axis tilt) of the cemented lens. If the optical axis tilt exceeds the tolerance, the tilt direction is marked, the lens surface is polished, and a template mirror is used to control the surface shape, thereby reducing the optical axis tilt data to meet the cementing accuracy requirements. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the optical axis of an ideal lens;

[0025] Figure 2 yes Figure 1 A schematic diagram showing the relative sliding of the first lens on the cemented surface;

[0026] Figure 3 yes Figure 2 Enlarged schematic diagram of the tilted optical axis;

[0027] Figure 4 This is a flowchart of the polishing method of the present invention.

[0028] Markings in the diagram: 1-First lens; 2-Second lens; 3-Third lens; 4-Optical axis of the first lens; 5-Optical axis of the second lens. Detailed Implementation

[0029] The present invention will now be described in further detail with reference to the accompanying drawings.

[0030] Cemented lenses have the following bonding parameters: 1) coaxiality, 2) eccentricity, and 3) optical axis tilt. Coaxiality and eccentricity are generally required to be within 5μm (coaxiality is measured by determining the reference lens; a roundness meter is used to measure the radial runout of the reference lens's outer circle, and the platform is adjusted to zero; the roundness meter is then used to measure whether the radial runout of the outer circles of the other lenses is within 5μm). Existing bonding processes ensure the accuracy requirements for coaxiality and eccentricity, while the optical axis tilt requirement for cemented lenses is generally within 5μm. ‘’ ~20 ‘’However, multi-cemented lenses are prone to out-of-tolerance issues after cementation (the theoretical analysis of out-of-tolerance will be given in subsequent illustrations). The traditional method to solve the out-of-tolerance problem is to de-glu the cemented lens at high temperature and re-glu it. This will lead to the following problems: 1) Delayed delivery cycle and reduced work efficiency; 2) Risk of cracking during high-temperature de-gluing; 3) Re-gluing requires recalibration and cannot guarantee that the accuracy indicators will meet the requirements. This invention uses a high-precision centering instrument to measure the cementation accuracy indicators of cemented lenses (1) coaxiality, 2) eccentricity, and 3) optical axis tilt. If the optical axis tilt exceeds the tolerance, the tilt direction is marked, the lens surface is repaired and polished, and the surface shape is controlled by a template mirror to reduce the optical axis tilt data to meet the cementation accuracy requirements.

[0031] The optical axis is defined as the line connecting the centers and focal points of two spheres. In a gel-type ideal lens, since the thickness difference and coaxiality of the lens are both zero, all the centers of the spheres should be located on the mechanical central axis, and the line connecting them (the optical axis) should coincide with the mechanical central axis.

[0032] The method of this invention is particularly suitable for repairing and polishing cemented lenses; therefore, the following embodiments use a three-cemented lens as an example. The three-cemented lens of this embodiment includes a first lens 1, a second lens 2, and a third lens 3. The ideal optical axis of this three-cemented lens is as follows: Figure 1 As shown.

[0033] However, in practice, the lenses may slip relative to each other during the bonding process. In this embodiment, the second lens 2 is selected as the reference lens, and it is assumed that the lens that slips relative to each other is the first lens 1. Figure 2 Using the second lens 2 as the reference lens, the first lens 1 and the third lens 3 are cemented together with the second lens 2. The optical axis 5 of the second lens is set as the reference axis (i.e., the optical axis of the reference lens / the axis of mechanical rotation) that coincides with the mechanical center axis. During the cementing process, due to relative sliding, it is difficult for the outer circles of the upper and lower lenses to be completely concentric, that is, the coaxiality cannot be completely zero. For example, after the first lens 1 slides relative to the second lens 2 on the cementing surface, the optical axis 4 of the first lens will tilt. The tilt value is related to the angle of sliding (e.g., ...). Figure 2 (See enlarged diagram) Figure 3 As shown.

[0034] This embodiment describes a method for controlling the optical axis by polishing the surface of a cemented lens, as follows: Figure 4 As shown,

[0035] 1) Place the cemented lens on the rotating platform, use a roundness tester to measure the radial runout of the lens's outer circle, and adjust the platform to make its value zero, thus determining the mechanical center axis;

[0036] 2) Use a high-precision centering instrument to measure the cemented lens, and position one of the lenses as a reference lens, and measure the angle between the optical axis of the remaining lenses and the optical axis of the reference lens;

[0037] 3) Check the tilt value; if it exceeds the tolerance, mark the tilt direction.

[0038] 4) Using drawing software, slide the lens on the cemented surface at the corresponding angle (i.e., the optical axis tilt angle a, in this embodiment, a = 0.0163°) and calculate the edge thickness difference △h (△h = |h1 - h2|, in this embodiment, h1 = 15.40255 mm, h2 = 15.40615 mm, and the thickness difference is 3.6 micrometers);

[0039] If the thickness difference is too large, that is, the sliding angle is too large, it means that the amount of polishing is huge and the amount of thickness removal at the center is too large, exceeding the tolerance, and then it is necessary to re-glu the material.

[0040] If the grinding amount is within the tolerance range after analysis, this method can be used to grind the inclined direction with a grinding tool (the grinding amount is the edge thickness difference; to be on the safe side, the grinding amount can be set to half of the thickness difference), and the template mirror is used to control the aperture number and thus control the surface shape.

[0041] 5) After polishing, use a high-precision centering instrument to repeatedly measure the optical axis tilt data. If it exceeds the tolerance, return to step 2. If it meets the bonding index requirements, then finish polishing.

[0042] 6) Confirm surface accuracy, smoothness, and other indicators before coating.

[0043] In summary, this invention provides a method for controlling the optical axis by polishing the surface of a cemented lens. The steps include: placing the cemented lens assembly on a rotating platform; measuring the outer circle and horizontal end face of the reference lens in the cemented lens assembly; adjusting the rotating platform to make its radial runout approach 0 μm; determining the mechanical central axis; measuring the cemented lens using a high-precision centering instrument to obtain the tilt data of each optical axis; setting the optical axis of the reference lens as the reference axis (i.e., the angle between it and the mechanical central axis is zero); checking the tilt values ​​of the optical axes of other lenses and calibrating their directions; polishing the corresponding positions of the lens surfaces using a grinding wheel; and controlling the lens surfaces to reduce the angle between the optical axes of the remaining lenses and the optical axis of the reference lens / mechanical central axis, thus meeting the tilt index requirements. Using this method, the surface of a cemented lens can be appropriately polished to reduce the tilt values ​​of each optical axis.

[0044] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method of controlling the optical axis by polishing the surface of a cemented lens, characterized by, include: Step 1: Place the cemented lens set on a rotary stage, measure the outer circle and the horizontal end face of the reference lens in the cemented lens set, adjust the rotary stage to make its radial runout tend to , determine the mechanical center axis; Step 2: Measure the cemented lens to obtain the tilt data of each optical axis, designate one of the lenses as the reference lens, and set the optical axis of the reference lens as the reference axis, that is, the angle between the reference lens and the mechanical center axis is zero. Step 3: Check the tilt values ​​of the optical axes of other lenses and mark their directions; Step 4: Use a polishing tool to polish the corresponding positions on the lens surface. By controlling the lens surface, the angle between the optical axis of the other lenses and the optical axis of the reference lens / mechanical center axis is reduced to meet the tilt index requirements.

2. A method of controlling the optical axis by polishing the surface of a cemented lens according to claim 1, wherein In step 1, a roundness meter is used to measure the radial runout of the outer circle of the lens and the platform is adjusted to make its value zero.

3. A method of controlling the optical axis by polishing the surface of a cemented lens according to claim 1, wherein In step 2, a high-precision centering instrument is used to measure the cemented lens, and one of the lenses is designated as the reference lens. The angle between the optical axis of the remaining lenses and the optical axis of the reference lens is measured.

4. The method of claim 1, wherein the method is used to control the optical axis of a glued lens by polishing the surface of the glued lens. In step 3, check the tilt values ​​of the optical axes of other lenses. If they are out of tolerance, mark the tilt direction.

5. The method of claim 1, wherein the method is used to control the optical axis of a glued lens by polishing the surface of the glued lens. Step 4 specifically includes: Step 4-1: Using drawing software, slide the lens on the cemented surface at the corresponding angle according to the optical axis tilt angle, and then calculate the edge thickness difference; If the thickness difference is too large, that is, the sliding angle is too large, it means that the amount of polishing is huge and the amount of thickness removal in the center is too large and exceeds the tolerance, so the glue is re-glued; if the amount of polishing is within the tolerance range, the polishing tool is used to polish the inclined direction, and the amount of polishing is the edge thickness difference, and the aperture number is controlled by the template mirror to control the surface shape. Step 4-2: After polishing, use a high-precision centering instrument to repeatedly measure the optical axis tilt data. If it exceeds the tolerance, return to step 2. If it meets the bonding index requirements, then finish polishing.

Images