KR102465766B1 - Measurement system for form error of optical surface using dove prism and beam expander - Google Patents

Abstract

The present invention relates to measuring the shape error of a large-diameter reflector, and more particularly, to a system for measuring the shape error of an optical surface using a rotating prism and a beam expander. To this end, in the shape error measuring system of the large-diameter reflector 10, the interferometer 100 including a detector and a light source; a first wave plate 110 that converts light from a light source into linearly polarized light; a first PBS 120, first and second image lenses 130 and 140, and a second PBS 150 arranged to pass linearly polarized light sequentially; a second wave plate 160 that converts the light passing through the second PBS 150 into circularly polarized light; an objective lens 170 that converts circularly polarized light into spherical waves and directs the large-diameter reflector 10; a rotating prism 220 into which light reflected from the large-diameter reflector 10 is reflected from the second PBS 150 and incident; a rotation motor 250 that rotates the rotation prism 220 by a predetermined angle; a beam expander 200 in which light passing through the rotating prism 220 is incident and expanded; an aperture 190 through which light passing through the beam expander 200 passes; a first reflector 180 that reflects light passing through the aperture 190 toward the first PBS 120; A linear motor 260 for moving the first reflector 180 in a linear direction; a shape error measuring system of an optical surface using a rotating prism and a beam expander, characterized in that it includes, is provided.

Description

Measurement system for form error of optical surface using dove prism and beam expander}

The present invention relates to measuring the shape error of a large-diameter reflector, and more particularly, to a system for measuring the shape error of an optical surface using a rotating prism and a beam expander.

In general, large reflectors or large-diameter reflectors are essential parts applied to terrestrial astronomical telescopes, satellite cameras, and EUV exposure equipment. Since such a large-diameter reflector is a high-resolution, large-diameter optical component, it must be very precise, and thus the manufacturing cost is high. In addition, after the fabrication is completed, the process of measuring and inspecting the shape error of the surface follows.

However, in the conventional surface error measurement method, a detector with high resolution was used to measure the surface of a high spatial frequency with an interferometer. At this time, there is a limit to increasing the resolution of the detector, and the higher the resolution, the higher the price.

On the other hand, if a part of the reflector is measured with an interferometer and all of the partial information is collected and combined, information can be obtained with high spatial resolution for the entire surface. However, it is necessary to move and realign the system whenever parts are measured, and a large positioning transfer stage that can define the position of the measuring instrument is required.

1. Republic of Korea Patent Registration No. 10-1861957 (Axis alignment error measuring device and method using reflector and variable shaft), 2. Republic of Korea Patent Registration No. 10-1751877 (Apparatus and method for measuring the relative position of a mirror reflective surface).

Therefore, the present invention has been made to solve the above problems, and the problem to be solved by the present invention is to apply a small diameter reflector measurement system when measuring shape errors with high spatial resolution when evaluating the performance of a large diameter reflector. By doing so, it is possible to measure with the existing system without introducing additional expensive equipment, and to provide a shape error measurement system for a large-diameter reflector using a rotating prism and a beam expander that can increase the efficiency of measurement.

However, the technical problems to be achieved in the present invention are not limited to the above-mentioned technical problems, and other technical problems not mentioned will be clear to those skilled in the art from the description below. You will be able to understand.

In order to achieve the above technical problem, in the shape error measuring system of the large-diameter reflector 10, the interferometer 100 including a detector and a light source; a first wave plate 110 that converts light from a light source into linearly polarized light; a first PBS 120, first and second image lenses 130 and 140, and a second PBS 150 arranged to pass linearly polarized light sequentially; a second wave plate 160 that converts the light passing through the second PBS 150 into circularly polarized light; an objective lens 170 that converts circularly polarized light into spherical waves and directs the large-diameter reflector 10; a rotating prism 220 into which light reflected from the large-diameter reflector 10 is reflected from the second PBS 150 and incident; a rotation motor 250 that rotates the rotation prism 220 by a predetermined angle; a beam expander 200 in which light passing through the rotating prism 220 is incident and expanded; an aperture 190 through which light passing through the beam expander 200 passes; a first reflector 180 that reflects light passing through the aperture 190 toward the first PBS 120; A linear motor 260 for moving the first reflector 180 in a linear direction; a shape error measuring system of an optical surface using a rotating prism and a beam expander, characterized in that it includes, is provided.

In addition, as another embodiment of the present invention, in the shape error measuring system of the large-diameter reflector 10, a light source and a collimator 300 for irradiating light; A first PBS 120 that reflects light; a first wave plate 110 that converts light into linearly polarized light; an objective lens 170 that converts linearly polarized light into spherical waves and directs the large-diameter reflector 10; a rotating prism 220 into which the light reflected from the large-diameter reflector 10 passes through the first PBS 120 and is incident; a rotation motor 250 that rotates the rotation prism 220 by a predetermined angle; a beam expander 200 in which light passing through the rotating prism 220 is incident and expanded; an aperture 190 through which light passing through the beam expander 200 passes; a wavefront sensor 310 receiving light passing through the aperture 190; A linear motor 260 for moving the diaphragm 190 and the wavefront sensor 310 in a linear direction; there is provided a shape error measuring system of an optical surface using a rotating prism and a beam expander comprising a.

In addition, the first wave plate 110 and the second wave plate 160 are λ/4 wave plates.

Also, the rotating prism 220 is a Dove prism.

In addition, a second reflector 210 for reflecting light reflected from the second PBS 150 toward the rotating prism 220 may be further included.

In addition, the rotating prism 220 rotates by equally dividing 180°, and the entire image rotates up to 360° by twice the divided angle.

Also, the divided angle is an angle selected from the range of 5° to 45°.

In addition, the linear motor 260 moves in a linear direction by the radius of the large-diameter reflector 10 .

In addition, while rotating the rotating prism 220 and moving the first reflector 180, a full image generating means for generating a full image by matching the partial images 20 of the large diameter reflector 10 measured by the detector is further provided. include

In addition, while rotating the rotating prism 220 and moving the wavefront sensor 310 and the diaphragm 190, the partial image 20 of the large-diameter reflector 10 measured by the wavefront sensor 310 is matched to obtain an entire image. It further includes an entire image generation unit to generate.

According to one embodiment of the present invention, when evaluating the performance of a large-diameter reflector by applying a measurement system for a small-diameter reflector, it may be necessary to measure a shape error with high spatial resolution. Therefore, there is no need to introduce additional expensive equipment, and there is an effect of increasing the efficiency of measurement.

In addition, it is possible to precisely measure the shape error of a large reflector with high spatial resolution at a low price without using a high resolution detector or a large precision stage that moves the measurement position of the interferometer.

In addition, it is possible to reduce manufacturing cost/time consumption, and thus, there is an effect of improving business feasibility and marketability for the development of large-sized optical equipment.

However, the effects obtainable in the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description below. You will be able to.

The following drawings attached to this specification illustrate preferred embodiments of the present invention, and together with the detailed description of the present invention serve to further understand the technical idea of the present invention, the present invention is the details described in such drawings should not be construed as limited to
1 is a configuration diagram of a system for measuring shape error of an optical surface using a rotating prism and a beam expander according to a first embodiment of the present invention.
2 is a plan view showing a combination of a large-diameter reflector 10 and a measured partial image 20;
3 is a configuration diagram of a shape error measuring system of an optical surface using a rotating prism and a beam expander according to a second embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention. However, since the description of the present invention is only an embodiment for structural or functional description, the scope of the present invention should not be construed as being limited by the embodiments described in the text. That is, since the embodiments can be changed and have various forms, it should be understood that the scope of the present invention includes equivalents capable of realizing the technical idea. In addition, since the object or effect presented in the present invention does not mean that a specific embodiment should include all of them or only such effects, the scope of the present invention should not be construed as being limited thereby.

The meaning of terms described in the present invention should be understood as follows.

Terms such as "first" and "second" are used to distinguish one component from another, and the scope of rights should not be limited by these terms. For example, a first element may be termed a second element, and similarly, a second element may be termed a first element. It should be understood that when an element is referred to as “connected” to another element, it may be directly connected to the other element, but other elements may exist in the middle. On the other hand, when an element is referred to as being “directly connected” to another element, it should be understood that no intervening elements exist. Meanwhile, other expressions describing the relationship between components, such as “between” and “immediately between” or “adjacent to” and “directly adjacent to” should be interpreted similarly.

Singular expressions should be understood to include plural expressions unless the context clearly dictates otherwise, and terms such as “comprise” or “having” refer to a described feature, number, step, operation, component, part, or It should be understood that it is intended to indicate that a combination exists, and does not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

All terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs, unless defined otherwise. Terms defined in commonly used dictionaries should be interpreted as consistent with meanings in the context of related art, and cannot be interpreted as having ideal or excessively formal meanings unless explicitly defined in the present invention.

Configuration of the first embodiment

Hereinafter, the configuration of a preferred embodiment will be described in detail with reference to the accompanying drawings. 1 is a configuration diagram of a system for measuring shape error of an optical surface using a rotating prism and a beam expander according to a first embodiment of the present invention. As shown in FIG. 1, the interferometer 100 may include a detector and a light source, emit light to one side, and detect the received light. The light source may be a laser light source or a lamp having a specific wavelength. The detector contains CCD or CMOS and can output digital images (e.g. JPG, RAW files). The first waveplate 110 is located in front of the interferometer 100 and is a λ/4 waveplate that converts light from a light source into linearly polarized light.

The first Prism Beam Seperator (PBS) 120 is located in front of the first wave plate 110 on the optical axis, and linearly polarized light sequentially passes therethrough. The first PBS 120 passes light from the first wave plate 110 to the first image lens 130 and reflects light from the first reflector 180 to the first wave plate 110 .

The first and second image lenses 130 and 140 are located between the first and second PBSs 120 and 150, and are composed of a plurality of convex lenses and concave lenses that control the focal length. A clear image of the large-diameter reflector 10 can be obtained by adjusting the distance between the first and second image lenses 130 and 140 .

The second PBS 150 is located between the second image lens 140 and the second wave plate 160 on the optical axis. The second PBS 150 passes light from the light source toward the large-diameter reflector 10 and reflects light reflected from the large-diameter reflector 10 to the second reflector 210 .

The second wave plate 160 is positioned between the second PBS 150 and the objective lens 170 and is a λ/4 wave plate that converts light from a light source back into circularly polarized light.

The objective lens 170 is located between the second wave plate 160 and the large-diameter reflector 10, and determines the size (diameter) of the partial image 20 inspecting the large-diameter reflector 10.

The second reflector 210 converts the reflected light by 90° from the second PBS 150 and then reflects it toward the rotating prism 220.

The rotation prism 220 is located between the second reflector 210 and the beam expander 200 and is a trapezoidal Dove prism. The rotating prism 220 is configured to rotate around an axis in the longitudinal direction.

The rotation motor 250 is configured to rotate the rotation prism 220 by a predetermined angle. For example, the rotation motor 250 may equally divide 180° in the range of 5° to 45° and rotate the entire image by twice the divided angle. The rotation motor 250 may be a stepping motor, a servo motor, a brushless DC servo motor, or the like.

The beam expander 200 is composed of third and fourth image lenses 230 and 240 that are movable on the optical axis. The beam expander 200 enlarges an image and functions to project a clear image onto the interferometer 100 . The magnification ratio can be determined by adjusting the distance of the third and fourth image lenses 230 and 240 .

The diaphragm 190 is provided between the beam expander 200 and the first reflector 180, and an opening of the diaphragm 190 is eccentric from the optical axis.

The first reflector 180 reflects light passing through the diaphragm 190 to the first PBS 120 . The first reflector 180 is configured to be reciprocally transported along a straight line toward the first PBS 120 . For this purpose, a slider or a transfer guide is provided.

The linear motor 260 is configured to linearly transfer the first reflector 180 by a predetermined distance. For example, the linear motor 260 can reciprocate in a linear direction as much as the radius of the large-diameter reflector 10 . The linear motor 260 may be a stepping motor, a servo motor, a brushless DC servo motor, a linear servo motor, or the like.

The entire image generating means is an image processing processor that generates a full image by matching the partial images 20 of the large-diameter reflector 10 measured by the detector while rotating the rotating prism 220 and moving the first reflector 180. to be. The entire image generating unit may be a Digital Signal Processor (DSP), CPU, Application Processor (AP), or a computer.

2 is a plan view showing a combination of a large-diameter reflector 10 and a measured partial image 20. As shown in FIG. 2 , the large-diameter reflector 10 is a circular reflective mirror having a large diameter. The detector of the interferometer 100 receives the partial image 20 . As shown in FIG. 2 , an entire image of the large-diameter reflector 10 may be generated by matching nine partial images 20 .

As the rotation prism 220 rotates in the rotation direction 225, the partial image 20 moves in the circumferential direction and is inspected. As the first reflector 180 is transferred along the linear direction 185, the partial image 20 moves in the radial direction and is inspected. Therefore, the entire area of the large-diameter reflector 10 can be inspected by combining the rotation of the rotating prism 220 and the linear transfer of the first reflector 180 .

Operation of the first embodiment

Hereinafter, the operation of the preferred embodiment will be described in detail with reference to the accompanying drawings. First, the light emitted from the light source of the interferometer 100 becomes linearly polarized while passing through the first wave plate 110 . Then, after passing through the first PBS 120, the first and second image lenses 130 and 140, and the second PBS 150, the light becomes circularly polarized light again while passing through the second wave plate 160. Then, a partial image 20 is obtained by inspecting (photographing) a portion of the large-diameter reflector 10 through the objective lens 170 .

The light reflected from the large-diameter reflector 10 passes through the objective lens 170 and the second wave plate 160 and is reflected from the second PBS 150 toward the second reflector 210.

Then, the light reflected by the second reflector 210 is incident to the rotating prism 220 . The rotation motor 250 equally divides 180° into 22.5° and rotates every 22.5°, so that the rotation prism 220 rotates to rotate the entire image by 45°, and 8 inspections (8 parts) are performed along the circumferential direction. An image 20 acquisition) is made.

Then, the light is magnified by the beam expander 200 and passes through the aperture 190, the first reflector 180, the first PBS 120, and the first wave plate 110 to the detector of the interferometer 100. are hired Accordingly, in the detector, 8 partial images 20 are acquired through 8 examinations.

Next, when the linear motor 260 moves the first reflector 180 in a linear direction, the central region of the large-diameter reflector 10 is inspected and one partial image 20 is obtained.

The entire image generation unit generates an inspection image for the entire reflector 10 by combining the nine images obtained in this way.

When the diameter of the large-diameter reflector 10 is large and the partial image 20 is relatively small, images can be obtained while the rotating prism 220 rotates 180° every time the first reflector 180 moves in stages. have.

Configuration of the second embodiment

3 is a configuration diagram of a shape error measuring system of an optical surface using a rotating prism and a beam expander according to a second embodiment of the present invention. Among the components of the second embodiment, detailed descriptions of the same components as those of the first embodiment are omitted. As shown in FIG. 3, the laser and collimator 300 emits a laser as a light source.

The first PBS 120 reflects the laser toward the first wave plate 110 .

The first wave plate 110 is provided between the first PBS 120 and the objective lens 170.

The objective lens 170 faces the large-diameter reflector 10.

The rotation prism 220 is located between the first PBS 120 and the beam expander 200 . Light reflected from the large-diameter reflector 10 passes through the objective lens 170, the first wave plate 110, and the first PBS 120 and enters the rotating prism 220.

The rotation motor 250 rotates the rotation prism 220 by a predetermined angle as in the first embodiment.

The beam expansion unit 200 is located between the rotating prism 220 and the wavefront sensor unit 320 . The beam expander 220 includes the first and second image lenses 130 and 140 as in the first embodiment.

The wavefront sensor unit 320 includes a wavefront sensor 310 and an aperture 190 . The wavefront sensor 310 is configured to receive the partial image 20 and inspect the wavefront of the large-diameter reflector 10 . The detection signal of the wavefront sensor 310 may be output as a digital image (eg, JPG or RAW file).

The linear motor 260 moves the wavefront sensor unit 320 in a linear direction.

The whole image generating unit generates a full image by matching the partial images 20 of the large-diameter reflector 10 measured by the wavefront sensor 310 while rotating the rotating prism 220 and moving the wavefront sensor 320. It is an image processing processor that

Operation of the second embodiment

First, the laser irradiated from the laser and collimator 300 is reflected by the first wave plate 110 and then passes through the first wave plate 110 . Then, a partial image 20 is obtained by inspecting (photographing) a portion of the large-diameter reflector 10 through the objective lens 170 .

Light reflected from the large-diameter reflector 10 passes through the objective lens 170 and the first wave plate 110 and then through the first PBS 120 .

Then, the laser is incident on the rotating prism 220. The rotation motor 250 equally divides 180° into 22.5° and rotates every 22.5°, so that the rotation prism 220 rotates to rotate the entire image by 45°, and 8 inspections (8 parts) are performed along the circumferential direction. An image 20 acquisition) is made.

Then, the laser is incident to the wavefront sensor 310 through the diaphragm 190 after being magnified by the beam magnifying unit 200 . Accordingly, in the wavefront sensor 310, 8 partial images 20 are acquired through 8 inspections.

Next, when the linear motor 260 moves the wavefront sensor unit 320 in a linear direction, the central region of the large-diameter reflector 10 is inspected and one partial image 20 is acquired.

The entire image generation unit generates an inspection image for the entire reflector 10 by combining the nine images obtained in this way.

When the diameter of the large-diameter reflector 10 is large and the partial image 20 is relatively small, images can be obtained while the rotating prism 220 rotates 180° every time the wavefront sensor unit 320 transfers step by step. have.

Detailed descriptions of the preferred embodiments of the present invention disclosed as described above are provided to enable those skilled in the art to implement and practice the present invention. Although the above has been described with reference to preferred embodiments of the present invention, those skilled in the art will understand that the present invention can be variously modified and changed without departing from the scope of the present invention. For example, those skilled in the art can use each configuration described in the above-described embodiments in a manner of combining with each other. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

The present invention may be embodied in other specific forms without departing from the spirit and essential characteristics of the present invention. Accordingly, the above detailed description should not be construed as limiting in all respects and should be considered as illustrative. The scope of the present invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the present invention are included in the scope of the present invention. The invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. In addition, claims that do not have an explicit citation relationship in the claims may be combined to form an embodiment or may be included as new claims by amendment after filing.

10: large diameter reflector,
20: partial image,
100: interferometer,
110: first wave plate,
120: first PBS,
130: first image lens,
140: second image lens,
150: second PBS,
160: second wave plate,
170: objective lens,
180: first reflector,
185: linear direction,
190: aperture,
200: beam expansion unit,
210: second reflector,
220: rotation prism,
225: rotation direction,
230: third image lens,
240: 4th image lens,
250: rotation motor,
260: linear motor,
300: laser and collimator,
310: wavefront sensor,
320: wavefront sensor unit.

Claims (11)

In the shape error measuring system of the large-diameter reflector 10,
an interferometer 100 including a detector and a light source;
a first wave plate 110 that converts light from the light source into linearly polarized light;
a first PBS 120, first and second image lenses 130 and 140, and a second PBS 150 arranged so that the linearly polarized light passes sequentially;
a second wave plate 160 for converting the light passing through the second PBS 150 into circularly polarized light;
an objective lens (170) that converts the circularly polarized light into a spherical wave and directs the large-diameter reflector (10);
a rotating prism 220 into which the light reflected from the large-diameter reflector 10 is reflected from the second PBS 150 and incident;
a rotation motor 250 that rotates the rotation prism 220 by a predetermined angle;
a beam expander 200 in which light passing through the rotating prism 220 is incident and expanded;
an aperture 190 through which the light passing through the beam expander 200 passes;
a first reflector 180 that reflects the light passing through the aperture 190 toward the first PBS 120;
A shape error measuring system of an optical surface using a rotation prism and a beam expander, characterized in that it comprises a; linear motor 260 for moving the first reflector 180 in a linear direction. In the shape error measuring system of the large-diameter reflector 10,
A light source and a collimator 300 for irradiating light;
a first PBS 120 that reflects the light;
a first wave plate 110 that converts the light into linearly polarized light;
an objective lens (170) that converts the linearly polarized light into a spherical wave and directs the large-diameter reflector (10);
a rotating prism 220 through which light reflected from the large-diameter reflector 10 is incident through the first PBS 120;
a rotation motor 250 that rotates the rotation prism 220 by a predetermined angle;
a beam expander 200 in which light passing through the rotating prism 220 is incident and expanded;
an aperture 190 through which the light passing through the beam expander 200 passes;
a wavefront sensor 310 receiving light passing through the aperture 190;
A shape error measuring system of an optical surface using a rotating prism and a beam expander, characterized in that it includes; a linear motor 260 for moving the diaphragm 190 and the wavefront sensor 310 in a linear direction. According to claim 1 or 2,
The first wave plate 110 is a shape error measuring system of an optical surface using a rotating prism and a beam expander, characterized in that the λ / 4 wave plate. According to claim 1 or 2,
The rotation prism 220 is a shape error measuring system of an optical surface using a rotation prism and a beam expansion unit, characterized in that a Dove prism. According to claim 1,
The shape error of the optical surface using the rotation prism and the beam expander, characterized in that it further comprises a second reflector 210 for reflecting the light reflected from the second PBS 150 toward the rotation prism 220. System for measuring error. According to claim 1 or 2,
The rotating prism 220 divides 180 ° equally and rotates at each divided angle. According to claim 6,
The divided angle is a shape error measuring system of an optical surface using a rotating prism and a beam expander, characterized in that the angle selected from the range of 5 ° to 45 °. According to claim 1 or 2,
The linear motor 260 is a shape error measuring system of an optical surface using a rotating prism and a beam expansion unit, characterized in that for moving in a linear direction by the radius of the large-diameter reflector 10. According to claim 1,
Full image generating means for generating a full image by matching partial images 20 of the large-diameter reflector 10 measured by the detector while rotating the rotation prism 220 and moving the first reflector 180 A shape error measuring system of an optical surface using a rotating prism and a beam expander, characterized in that it further comprises. According to claim 2,
While rotating the rotating prism 220 and moving the wavefront sensor 310 and the diaphragm 190, the partial images 20 of the large-diameter reflector 10 measured by the wavefront sensor 310 are matched. A shape error measuring system of an optical surface using a rotating prism and a beam expander, characterized in that it further comprises a full image generating means for generating a full image. According to claim 1,
The second wave plate 160 is a shape error measuring system of an optical surface using a rotating prism and a beam expander, characterized in that the λ / 4 wave plate.

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