A method and system for fold axis alignment for off-axis optical paths

Abstract

The application discloses a folding axis system alignment method and system for off-axis optical path, and belongs to the technical field of optical mechanical adjustment. First, the optical axis of an inner focusing telescope is made to coincide with the center axis of a first lens frame by using the inner focusing telescope and a first centering mirror tool. Then, an accurate alpha angle folding optical path is established by using an isosceles prism with a top angle of alpha and a second centering mirror tool. The placement position of the isosceles prism and the mounting position of a second lens frame are finely adjusted, so that the optical axis of the inner focusing telescope coincides with the center axis of the second lens frame after being folded by the alpha angle. Thus, the accurate alignment of the center axes of the first lens frame and the second lens frame is realized. The method applies the good linearity of the optical axis of the inner focusing telescope and the easy folding characteristics of the optical path to the accurate alignment of the folding axis system. By switching the isosceles folding prisms with different top angles, the accurate alignment of the folding axis system with different folding angles can be realized. The equipment cost is controlled while the alignment precision is ensured, and the structure is simple and easy to operate.

Description

Technical Field

[0001] This invention belongs to the field of optomechanical assembly and adjustment technology, specifically relating to a method and system for aligning a folding axis system for off-axis optical paths. Background Technology

[0002] In precision optomechanical products, optical elements often need to be mounted off-axis to achieve optical path folding. To ensure image quality, the optical axes of off-axis mounted optical elements must be precisely aligned to reduce aberrations introduced by installation errors. In some precision optomechanical products, due to the large spacing between the mounting axes of the optical elements and the small axial dimensions of the axes, integrated machining of the axes cannot meet the requirements for assembly and adjustment accuracy. Furthermore, due to the deflection of the optical axis, it is difficult to achieve precise alignment of the optical elements directly using optical centering methods. In engineering practice, it is often necessary to first ensure that the optical axis of the optical element coincides with the central axis of the mounting axis system, and then indirectly achieve the alignment of the optical axis by aligning the central axis of the axis system.

[0003] To achieve alignment of the central axes of the folding and rotating shaft system, a coordinate measuring machine (CMM) is typically used to inspect the two shaft systems separately, providing their spatial relationship and thus determining whether they are aligned. However, due to the small axial dimensions and large spatial distance of the folding and rotating shaft system, the error in the central axis of the shaft system measured and fitted by the CMM is magnified exponentially after spatial extension, failing to meet the accuracy requirements for aligning the optical axes of optical components. This results in poor imaging quality of the assembled optical system. Therefore, a method to achieve precise alignment of the folding and rotating shaft system is needed. Summary of the Invention

[0004] The technical problem to be solved:

[0005] To avoid the shortcomings of the prior art, the present invention provides a method and system for aligning the folding axis system for off-axis optical paths. The method and system use an internal focusing telescope to achieve accurate alignment of the central axes of the first lens mount and the second lens mount, providing an accurate installation reference for the off-axis assembly of optical components.

[0006] The technical solution of this invention is: a method for aligning a folding axis system for off-axis optical paths, the specific steps of which are as follows:

[0007] Step 1: Install the first lens mount onto one end of the optical engine housing;

[0008] Step 2: Install the first centering mirror fixture containing the plane mirror into the first lens frame, and set a crosshair at its center to ensure that the plane mirror in the first centering mirror fixture is coaxial with the first lens frame;

[0009] Step 3: Place the internal focusing telescope on the outside of the optical engine housing, with its output optical path opposite to the first centering mirror fixture; adjust the position, angle, and focal length of the internal focusing telescope to make its optical axis coincide with the central axis of the first lens mount; then remove the first centering mirror fixture from the first lens mount.

[0010] Step 4: Install the second lens mount on the other end of the off-axis optical path of the optical engine housing, but do not tighten it completely;

[0011] Step 5: Place the isosceles prism with apex angle α at the intersection of the central axes of the first lens frame and the second lens frame; adjust the focal length of the internal focusing telescope to infinity, and at the same time adjust the placement angle of the isosceles prism so that the internal focusing telescope is autocollimated relative to the isosceles surface of the isosceles prism; at this time, the optical axis of the internal focusing telescope is deflected by an angle α after being reflected by the isosceles prism with apex angle α.

[0012] Step 6: Install the second centering mirror fixture containing the plane mirror into the second lens frame, and set a crosshair at its center to ensure that the plane mirror in the second centering mirror fixture is coaxial with the second lens frame;

[0013] Step 7: By adjusting the focal length of the internal focusing telescope, the position of the isosceles prism, and the position of the second lens mount, the optical axis of the internal focusing telescope is aligned with the central axis of the second lens mount. That is, the optical axis of the internal focusing telescope is aligned with the central axis of the second lens mount after being rotated by an angle α. Then, the second centering mirror fixture is removed from the second lens mount, and the second lens mount is fully secured. This completes the alignment of the off-axis optical path's rotation axis system.

[0014] A further technical solution of the present invention is: in step 1, the first lens frame is positioned on the mounting surface of the optical engine housing by a pin and fixed to the optical engine housing by fasteners.

[0015] A further technical solution of the present invention is: in step 2, the plane normal at the intersection of the center of the cross lines coincides with the central axis of the first lens frame.

[0016] A further technical solution of the present invention is: in step 3, the internal focusing telescope is installed on the four-dimensional adjustment mechanism, and the optical path angle of the internal focusing telescope is precisely adjusted by the four-dimensional adjustment mechanism.

[0017] A further technical solution of the present invention is as follows: In step 3, firstly, the focal length of the internal focusing telescope is adjusted to infinity, and its placement angle is adjusted to autoalign with the plane mirror of the first centering mirror fixture; then, the focal length of the internal focusing telescope is adjusted so that the crosshairs of the first centering mirror fixture are clearly imaged in the internal focusing telescope; finally, while maintaining the placement angle of the internal focusing telescope, the position of the internal focusing telescope is adjusted in a plane perpendicular to the optical axis of the internal focusing telescope so that the crosshairs of the first centering mirror fixture coincide with the center of the reticle of the internal focusing telescope, that is, the optical axis of the internal focusing telescope coincides with the central axis of the first lens mount.

[0018] A further technical solution of the present invention is: in step 5, the isosceles prism is installed on the three-dimensional adjustment mechanism, and the position and angle of the isosceles prism are adjusted by the three-dimensional adjustment mechanism; so that the isosceles surface on one side of the isosceles prism is perpendicular to the optical axis of the internal focusing telescope, and the apex is located between the first lens frame and the second lens frame.

[0019] A further technical solution of the present invention is: in step 6, the plane normal at the intersection of the center of the cross lines coincides with the central axis of the second lens frame.

[0020] A further technical solution of the present invention is as follows: In step 7, firstly, the focal length of the internal focusing telescope is adjusted to infinity and autocollimated with the plane mirror of the second centering mirror fixture; then, the focal length of the internal focusing telescope is adjusted so that the image of the central crosshair of the second centering mirror fixture can be observed in its field of view; finally, the installation position of the second lens mount is adjusted in a plane perpendicular to the central axis of the second lens mount so that the crosshair of the second centering mirror fixture coincides with the center of the dividing plate of the internal focusing telescope, that is, the optical axis of the internal focusing telescope coincides with the central axis of the second lens mount after being rotated by an angle α.

[0021] A further technical solution of the present invention is: when the plane mirror of the second centering mirror fixture is self-aligned, if the internal focusing telescope cannot observe the reflected image of the second centering mirror fixture, copper foil shims are added or removed on the mounting surface of the second lens frame to adjust the angle of the second centering mirror fixture so that the internal focusing telescope is self-aligned relative to the centering mirror fixture.

[0022] A further technical solution of the present invention is: if the image of the crosshairs of the second centering mirror fixture cannot be observed in the field of view of the internal focusing telescope, the isosceles prism is adjusted in the plane containing the isosceles surface facing the internal focusing telescope by a three-dimensional adjustment mechanism so that the crosshairs of the second centering mirror fixture appear in the field of view of the internal focusing telescope.

[0023] A folding axis alignment system for off-axis optical paths includes an internal focusing telescope, an optical engine housing, a first centering mirror fixture, a first lens mount, an isosceles prism, a second lens mount, and a second centering mirror fixture. The first lens mount and the second lens mount are respectively installed on both sides of the optical engine housing. The first centering mirror fixture and the second centering mirror fixture, which are equipped with plane mirrors, are coaxially installed in the first lens mount and the second lens mount, respectively.

[0024] The isosceles prism has an apex angle of α and is set inside the optical engine housing by a three-dimensional adjustment mechanism. The isosceles prism is located at the intersection of the central axes of the first lens frame and the second lens frame.

[0025] The internal focusing telescope is mounted on the outside of the optical engine housing via a four-dimensional adjustment mechanism, and its output light path is positioned opposite to the first centering mirror fixture; it can achieve off-axis light path deflection at angle α.

[0026] Beneficial effects

[0027] The beneficial effects of this invention are as follows: This invention is an assembly and adjustment method for establishing a folding optical path using an internal focusing telescope, a centering fixture, and an isosceles prism. First, the optical axis of the internal focusing telescope is aligned with the central axis of the first lens mount using the internal focusing telescope and the first centering mirror fixture. Then, an accurate folding optical path at angle α is established using an isosceles prism with a vertices of α and the second centering mirror fixture. By finely adjusting the placement of the isosceles prism and the installation position of the second lens mount, the optical axis of the internal focusing telescope, after being folded by angle α, is aligned with the central axis of the second lens mount, thus achieving accurate alignment of the central axes of the first and second lens mounts. This method applies the good linearity of the internal focusing telescope's optical axis and the easy folding characteristics of its optical path to the accurate alignment of the folding axis system. By switching isosceles folding prisms with different vertices, accurate alignment of axis systems with different folding angles can be achieved. It controls equipment costs while ensuring alignment accuracy, and the structure is simple and easy to operate.

[0028] The folding axis alignment method proposed in this invention requires simple equipment and conditions, and is low in cost. It does not require strict control of ambient temperature and humidity, and can meet the alignment requirements of folding axis systems for large-size optomechanical products. The established alignment accuracy can reach 0.02 to 0.04 mm. Furthermore, by changing isosceles prisms with different apex angles, alignment of folding axis systems with different folding angles can be achieved, which has practical engineering value. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of a folding axis system for off-axis optical paths according to the present invention.

[0030] Explanation of reference numerals in the attached drawings: 1-Four-dimensional adjustment mechanism, 2-Internal focusing telescope, 3-First centering mirror fixture, 4-First lens frame, 5-Optical engine housing, 6-Three-dimensional adjustment mechanism, 7-Isosceles prism, 8-Second lens frame, 9-Second centering mirror fixture. Detailed Implementation

[0031] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0032] Reference Figure 1 As shown, this embodiment discloses a folding axis alignment system for off-axis optical paths, including an internal focusing telescope 2, an optical engine housing 5, a first centering mirror fixture 3, a first lens mount 4, an isosceles prism 7, a second lens mount 8, and a second centering mirror fixture 9. The first lens mount 4 and the second lens mount 8 are respectively mounted on both sides of the optical engine housing 5. The first centering mirror fixture 3 and the second centering mirror fixture 9, each equipped with a plane mirror, are coaxially mounted in the first lens mount 4 and the second lens mount 8, respectively. The isosceles prism 7 has an apex angle of α and is positioned within the optical engine housing 5 via a three-dimensional adjustment mechanism 6, with the isosceles prism 7 located at the intersection of the central axes of the first lens mount 4 and the second lens mount 8. The internal focusing telescope 2 is mounted on the outside of the optical engine housing 5 via a four-dimensional adjustment mechanism 1, and its outgoing optical path is positioned opposite to the first centering mirror fixture 3. This system enables off-axis optical path folding at an angle α.

[0033] The specific steps of the method for aligning the folding axis system for off-axis optical paths in this embodiment are as follows:

[0034] Step 1: Assemble the first lens frame 4 onto the optical engine housing 5, and use pins and fasteners to position and secure it;

[0035] Step 2: Install the first centering mirror fixture 3, which contains the plane mirror, into the first lens holder 4. The centering mirror fixture 3 has a crosshair engraved at its center, which is about 0.02 mm wide. Through the precise mechanical fit between the centering mirror fixture 3 and the first lens holder 4, it can be ensured that the plane normal at the intersection of the crosshair centers coincides with the central axis of the first lens holder 4.

[0036] Step 3: Place the internal focusing telescope 2 onto the four-dimensional adjustment mechanism 1, with the outgoing light path roughly aligned with the first centering mirror fixture 3. Adjust the focal length of the internal focusing telescope 2 to infinity, and adjust the placement angle of the internal focusing telescope 2 through the four-dimensional adjustment mechanism 1 so that the internal focusing telescope 2 is self-aligned with the plane mirror of the first centering mirror fixture 3;

[0037] Step 4: Adjust the focal length of the internal focusing telescope 2 so that the crosshairs at the center of the centering mirror fixture 3 are clearly imaged in the internal focusing telescope 2.

[0038] Step 5: Maintaining the placement angle of the internal focusing telescope 2, adjust the position of the internal focusing telescope 2 using the four-dimensional adjustment mechanism 1 in a plane perpendicular to the optical axis of the internal focusing telescope 2, so that the crosshair at the center of the first centering mirror fixture 3 coincides with the center of the reticle of the internal focusing telescope 2. At this time, the optical axis of the internal focusing telescope 2 coincides with the central axis of the first lens mount 4. Remove the first centering mirror fixture 3 from the first lens mount 4.

[0039] Step 6: Assemble the second lens mount onto the other side of the optical engine housing 5, but do not tighten it completely; place the three-dimensional adjustment mechanism 6 at approximately the intersection of the central axes of the first lens mount 4 and the second lens mount 8, and then place an isosceles prism 7 with a apex angle of α on the three-dimensional adjustment mechanism 6, with one of the isosceles surfaces approximately perpendicular to the optical axis of the internal focusing telescope 2, and with the apex angle facing the side of the second lens mount 8;

[0040] Step 7: Adjust the focal length of the internal focusing telescope 2 to infinity, and adjust the placement angle of the isosceles prism 7 through the three-dimensional adjustment mechanism 6 so that the internal focusing telescope 2 is autocollimated relative to the isosceles surface of the isosceles prism 7; at this time, the optical axis of the internal focusing telescope 2 is deflected by an angle α after being reflected by the isosceles prism 7 with a vertex angle of α.

[0041] Step 8: Assemble the second lens mount 8 onto the optical engine housing 5, but do not tighten it completely. Then, mount the second centering mirror fixture 9, which contains the plane mirror, onto the second lens mount 8. The center of the second centering mirror fixture 9 is engraved with a crosshair about 0.02 mm wide. Through the precise mechanical fit between the second centering mirror fixture 9 and the second lens mount 8, it can be ensured that the plane normal at the intersection of the crosshair centers coincides with the central axis of the second lens mount 8.

[0042] Step 9: Adjust the focal length of the internal focusing telescope 2 to infinity and observe whether the autocollimated image returned by the second centering mirror fixture 9 can be observed in the field of view of the internal focusing telescope 2. The reflecting surface of the second centering mirror fixture 9 has high reflectivity and is brighter than the reflected image of the isosceles surface of the isosceles prism 7. If the reflected image of the second centering mirror fixture 9 cannot be observed, adjust the angle of the second centering mirror fixture 9 by adding or subtracting copper foil shims on the mounting surface of the second lens frame 8 so that the internal focusing telescope 2 is autocollimated relative to the second centering mirror fixture 9. At this time, the optical axis of the internal focusing telescope 2 is deflected by an angle α and is parallel to the central axis of the second lens frame 8.

[0043] Step 10: Adjust the focal length of the internal focusing telescope 2 so that the image of the central crosshair of the second centering mirror fixture 9 can be observed in the field of view of the internal focusing telescope 2. If the image of the central crosshair of the second centering mirror fixture 9 cannot be observed, adjust the position of the isosceles prism 7 in the plane containing the isosceles surface of the internal focusing telescope 2 using the three-dimensional adjustment mechanism 6 so that the image of the central crosshair of the second centering mirror fixture 9 appears in the field of view of the internal focusing telescope 2.

[0044] Step 11: Adjust the installation position of the second lens mount 8 in a plane perpendicular to the central axis, so that the image of the central crosshair of the second centering mirror fixture 9 coincides with the center of the dividing plate of the inner focusing telescope 2. At this time, the optical axis of the inner focusing telescope 2, after being rotated by an angle α, coincides with the central axis of the second lens mount 8. Disassemble the second centering mirror fixture 9 and use screws and locating pins to fix the installation position of the second lens mount 8.

[0045] Since the optical axis of the internal focusing telescope 2 has been aligned with the central axis of the first lens mount 4 through steps 1 to 5, the alignment of the central axis of the first lens mount 4 with the central axis of the second lens mount 8 after being rotated by an angle α is achieved by using the optical axis of the internal focusing telescope 2 as a conversion reference.

[0046] Step 12: The first lens and the second lens are coaxially mounted on the first lens mount 4 and the second lens mount 8, respectively, to form the folding axis system of the off-axis optical path.

[0047] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A fold axis alignment method for off-axis optical paths, characterized by The specific steps are as follows: Step 1: install the first lens holder at one end of the optical machine shell; Step 2: install the first centering mirror tool with a plane mirror into the first lens holder, and set a cross line at the center to ensure that the plane mirror in the first centering mirror tool is coaxial with the first lens holder; the plane normal at the intersection of the cross line center coincides with the central axis of the first lens holder; Step 3: set the inner focusing telescope outside the optical machine shell, with its outgoing light path opposite to the first centering mirror tool; adjust the position, angle and focal length of the inner focusing telescope to make the optical axis of the inner focusing telescope coincide with the central axis of the first lens holder; then disassemble the first centering mirror tool from the first lens holder; specifically: first, adjust the focal length of the inner focusing telescope to infinity, and adjust the angle of the inner focusing telescope to self-align the plane mirror of the first centering mirror tool; then, adjust the focal length of the inner focusing telescope to make the cross line of the first centering mirror tool clearly imaged in the inner focusing telescope; finally, keep the angle of the inner focusing telescope, and in the plane perpendicular to the optical axis of the inner focusing telescope, adjust the position of the inner focusing telescope to make the cross line of the first centering mirror tool coincide with the center of the graticule of the inner focusing telescope, that is, the optical axis of the inner focusing telescope coincides with the central axis of the first lens holder; Step 4: install the second lens holder at the other end of the off-axis light path of the optical machine shell, and do not fasten it completely; Step 5: place an isosceles prism with a top angle of α at the intersection of the central axes of the first lens holder and the second lens holder; adjust the angle of the isosceles prism while adjusting the focal length of the inner focusing telescope to infinity, so that the inner focusing telescope is self-aligned relative to the isosceles face of the isosceles prism; at this time, the optical axis of the inner focusing telescope is reflected by the isosceles prism with a top angle of α, and the optical axis is deflected by an angle of α; Step 6: install the second centering mirror tool with a plane mirror into the second lens holder, and set a cross line at the center to ensure that the plane mirror in the second centering mirror tool is coaxial with the second lens holder; the plane normal at the intersection of the cross line center coincides with the central axis of the second lens holder; Step 7: By adjusting the focal length of the inner focusing telescope, the position of the isosceles prism, and the position of the second lens holder, the optical axis of the inner focusing telescope is aligned with the central axis of the second lens holder, i.e., the optical axis of the inner focusing telescope is folded by an angle of α and coincides with the central axis of the second lens holder; then the second centering mirror tool is removed from the second lens holder, and the second lens holder is completely fastened; i.e., the folded axis alignment of the off-axis optical path is completed; specifically: first, the focal length of the inner focusing telescope is adjusted to infinity, and the plane mirror of the second centering mirror tool is self-aligned; then, the focal length of the inner focusing telescope is adjusted, and the image of the central crosshair of the second centering mirror tool can be observed in its field of view; finally, the installation position of the second lens holder is adjusted in the plane perpendicular to the central axis of the second lens holder, so that the crosshair of the second centering mirror tool coincides with the center of the dividing plate of the inner focusing telescope, i.e., the optical axis of the inner focusing telescope is folded by an angle of α and coincides with the central axis of the second lens holder.

2. The fold axis alignment method for off-axis optical paths of claim 1, wherein: In step 3, the inner focusing telescope is installed on a four-dimensional adjustment mechanism, and the optical path angle of the inner focusing telescope is accurately adjusted through the four-dimensional adjustment mechanism.

3. The fold axis alignment method for off-axis optical paths of claim 1, wherein: In step 5, the isosceles prism is installed on a three-dimensional adjustment mechanism, and the position and angle of the isosceles prism are adjusted through the three-dimensional adjustment mechanism; one side of the isosceles face of the isosceles prism is perpendicular to the optical axis of the inner focusing telescope, and the vertex angle is located between the first lens holder and the second lens holder.

4. The fold axis alignment method for off-axis optical paths of claim 1, wherein: When the plane mirror of the second centering mirror tool is self-aligned, if the reflected image of the second centering mirror tool cannot be observed by the inner focusing telescope, copper foil shims are added or removed on the mounting surface of the second lens holder to adjust the angle of the second centering mirror tool, so that the inner focusing telescope is self-aligned relative to the centering mirror tool.

5. The fold axis alignment method for off-axis optical paths of claim 4, wherein: If the image of the crosshair of the second centering mirror tool cannot be observed in the field of view of the inner focusing telescope, the isosceles prism is adjusted in the plane where the isosceles face of the isosceles prism is located through the three-dimensional adjustment mechanism, so that the crosshair of the second centering mirror tool appears in the field of view of the inner focusing telescope.

6. A system for implementing the fold axis alignment method for off-axis optical paths of any of claims 1-5, characterized by: It comprises an inner focusing telescope, an optical and mechanical shell, a first centering mirror tool, a first lens holder, an isosceles prism, a second lens holder, and a second centering mirror tool; the optical and mechanical shell is provided with the first lens holder and the second lens holder on both sides, and the first centering mirror tool and the second centering mirror tool provided with a plane mirror are coaxially installed in the first lens holder and the second lens holder, respectively; The vertex angle of the isosceles prism is α, which is set in the optical and mechanical shell through a three-dimensional adjustment mechanism, and the isosceles prism is located at the intersection of the central axes of the first lens holder and the second lens holder; The inner focusing telescope is installed outside the optical and mechanical shell through a four-dimensional adjustment mechanism, and the exit optical path is opposite to the first centering mirror tool; the off-axis optical path folding angle of α can be realized.

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