KR101258601B1

KR101258601B1 - focus indicator

Info

Publication number: KR101258601B1
Application number: KR1020100131520A
Authority: KR
Inventors: 양호순; 이윤우
Original assignee: 한국표준과학연구원
Priority date: 2010-12-21
Filing date: 2010-12-21
Publication date: 2013-05-03
Also published as: KR20120070102A

Abstract

The present invention relates to a focus indicator used when measuring a focal position or focal length of an optical system located between an interferometer and a reflector. The focus indicator may include: a support plate positioned between the interferometer and the optical system when the focus position or the focal length of the optical system is measured and provided to move in a direction closer to or farther from the interferometer; And a spherical reflector fixed to the support plate to reflect light emitted from the interferometer.

Description

Focus indicator {FOCUS INDICATOR}

The present invention relates to a focus indicator used to accurately measure a focal position or focal length of an optical system provided in an optical device.

In general, optical instruments are used to form images of objects in space or analyze light reflected from the objects by using characteristics of light (reflection, refraction, interference, diffraction, etc.) radiated from the sun or electric light. Means a device. Examples of the optical device include a telescope, a microscope, a camera, and the like. Optical devices are usually equipped with an optical system. The optical system is manufactured by appropriately combining a reflector, a lens, a prism, and the like, and has a focus. An image of an object is formed at the focal point of the optical system.

In order for the performance of the optical apparatus to be properly exhibited, the accuracy of the mounting position of the optical system is required, and the information about the focus position or the focal length of the optical system is required in order to accurately determine the position where the optical system is mounted on the optical apparatus. For example, when the optical device is a camera, as shown in FIG. 1, the focal position of the optical system 10 must be formed on the image sensor 12, that is, the focal length f of the optical system 10 is compared with the optical system 10. An image of an object may be clearly formed in the image sensor 12 when the distance between the image sensors 12 is the same. Therefore, prior to the mounting operation of the optical system 10, the focus position or the focal length measurement operation of the optical system 10 is preceded. Hereinafter, a method of measuring a focus position or a focal length of the optical system 10 using a conventional focus indicator will be described with reference to FIG. 2.

The focal position or focal length measurement operation of the optical system 10 is initiated by placing the optical system 10 between the interferometer 20 and the external reflector 30 and then operating the interferometer 20. Here, the interferometer 20 includes a light source 22, a semi-plated mirror 25, an internal reflector 23, a lens 24, and an image sensor 26.

When the interferometer 20 is operated, light is irradiated from the light source 22, a part of the light irradiated from the light source 22 is reflected by the half-plating mirror 25 and then directed to the inner reflector 23, and the rest is half-plated ( Pass 25 to lens 24. The light reflected by the semi-plating mirror 25 is reflected by the internal reflecting mirror 23 and passes through the semi-plating mirror 25 to reach the image sensor 26. Light passing through the semi-plating mirror 25 toward the lens 24 is reflected by the external reflector 30 after passing through the optical system 10, and the light reflected by the external reflector 30 is again reflected by the optical system 10 and Pass through the lens 24 sequentially. Light passing through the lens 24 is reflected by the semi-plated mirror 25 and reaches the image sensor 26. When the light reflected from the inner reflector 23 and the outer reflector 30 reaches the image sensor 26, interference of light occurs in the image sensor 26. Interference from the image sensor 26 may be visually confirmed through the display device 27 electrically connected to the image sensor 26.

If an interference fringe appears on the display device 27 after the interferometer 20 is operated, the optical system 10 is moved in a direction closer to the interferometer 20 or in a direction away from the interferometer 20. When the interference pattern having a desired shape appears on the display device 27 during the movement of the optical system 10, the optical system 10 is fixed.

In the state where the optical system 10 is fixed, the focal point of the optical system 10 is located in the space between the optical system 10 and the lens 24, as shown in FIG. 2. However, since the focus cannot be visually confirmed, the focus position of the optical system 10 cannot be measured directly. After the optical system 10 is fixed, the focus indicator 40 is positioned between the lens 24 and the optical system 10.

At this time, if all the light passing through the lens 24 passes through the hole 42 formed in the focus indicator 40, when the interference fringe and the focus indicator 40 when the focus indicator 40 is not positioned The interference fringes of are identical. However, if any part of the light passing through the lens 24 does not pass through the hole 42, the interference fringe when the focus indicator 40 is not positioned and the interference fringe when the focus indicator 40 is positioned are different. Therefore, when the focus indicator 40 moves in a direction closer to the lens 24 or away from the lens 24, an interference pattern that appears in the display device 27 does not position the focus indicator 40. If it is equal to, the center of the hole 42 is the focal position of the optical system 10. In this case, if the focal length f of the optical system 10 is to be known, the distance between the center of the hole 42 and the optical system 10 is measured, and the distance is defined as the focal length f of the optical system 10.

However, when the focus indicator 40 as described above is used to measure the focal position or the focal length f of the optical system 10, as shown in FIG. 3, the focus of the optical system 10 is determined by the focus indicator 40. The interference pattern when the focus indicator 40 is not positioned not only in the case of being accurately positioned in the center of the hole 42 (in the case of (a)) but also in the case of (b) or in the case of (c), The interference fringes when the focus indicator 40 is positioned are the same. Therefore, when the focus position or the focal length f of the optical system 10 is measured using the focus indicator 40, an error of up to d / 2 may occur in the measured focal position or the focal length f. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a focus indicator that enables more accurate measurement of an optical system focus position or focal length.

In order to achieve the object described above, the present invention is a focus indicator used when measuring the focal position or the focal length of the optical system located between the interferometer and the reflector, and when measuring the focal position or focal length of the optical system and the interferometer A support plate disposed between the optical systems and provided to move in a direction closer to or farther from the interferometer; And a spherical reflector fixed to the support plate and reflecting light irradiated from the interferometer.

Preferably, a plurality of spherical reflectors are fixed to the support plate, and any one of the plurality of spherical reflectors is used to measure a focal position or focal length of the optical system when light is incident vertically into the optical system, and the other is light to the optical system. It is used to measure the focal position or the focal length of the optical system when this oblique incident.

According to the present invention, since the interference fringes when the focus indicator is not positioned and the interference fringes when the focus indicator are positioned only when the focal position of the optical system is exactly coincident with the center position of the spherical reflector, the focal position or the focus of the optical system The distance can be measured accurately.

1 is a schematic diagram illustrating an optical system and an image sensor of a camera.
2 is a schematic view illustrating a method of measuring a focus position or a focal length of an optical system using a conventional focus indicator.
3 is a partial cross-sectional view for explaining the problem of the conventional focus indicator.
4 is a schematic diagram illustrating a method of measuring a focus position or a focal length of an optical system using a focus indicator according to the present invention.
FIG. 5 is a schematic diagram illustrating the operation of the focus indicator shown in FIG. 4.
6 is a perspective view illustrating a modification of the focus indicator shown in FIG. 4.
FIG. 7 is a schematic diagram illustrating a method of measuring a focus position or a focal length of an optical system using the focus indicator illustrated in FIG. 6.

Hereinafter, preferred embodiments of the focus indicator according to the present invention will be described in detail with reference to the drawings. It is to be understood that the terminology or words used herein are not to be construed in an ordinary sense or a dictionary, and that the inventor can properly define the concept of a term to describe its invention in the best possible way And should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention.

The focal position or focal length measurement of the optical system 10 is made using an interferometer 20, an external reflector 30, and a focus indicator according to the present invention. The interferometer 20 includes a light source 22, a semi-plated mirror 25, an internal reflector 23, a lens 24, and an image sensor 26. In addition, the focus indicator includes a support plate 110 positioned between the interferometer 20 and the optical system 10 when the focus position or the focal length of the optical system 10 is measured, and light fixed to the support plate and irradiated from the interferometer 20. It includes a spherical reflector 120 that reflects.

In this case, the support plate 110 is mounted on a driving unit (not shown) that performs a linear reciprocating motion in the direction in which the interferometer 20 or the optical system 10 is located. The spherical reflector 120 is fixed to the support plate 110 by fixing means 130 such as a bolt or a pin.

Hereinafter, a method of measuring the focus position or the focal length of the optical system 10 using the interferometer 20, the external reflector 30, and the focus indicator will be described.

The focal position or focal length f_c measurement of the optical system 10 is initiated by placing the optical system 10 between the interferometer 20 and the external reflector 30 and then operating the interferometer 20. When the interferometer 20 is operated, light is irradiated from the light source 22, a part of the light irradiated from the light source 22 is reflected by the half-plating mirror 25 and then directed to the inner reflector 23, and the rest is half-plated ( Pass 25 to lens 24. The light reflected by the semi-plating mirror 25 is reflected by the internal reflecting mirror 23 and passes through the semi-plating mirror 25 to reach the image sensor 26. Light passing through the semi-plating mirror 25 toward the lens 24 is reflected by the external reflector 30 after passing through the optical system 10, and the light reflected by the external reflector 30 is again reflected by the optical system 10 and Pass through the lens 24 sequentially. Light passing through the lens 24 is reflected by the semi-plated mirror 25 and reaches the image sensor 26. When the light reflected from the inner reflector 23 and the outer reflector 30 reaches the image sensor 26, interference of light occurs in the image sensor 26. Interference from the image sensor 26 may be visually confirmed through the display device 27 electrically connected to the image sensor 26.

In the state in which the optical system 10 is fixed, the focus of the optical system 10 is located in the space between the optical system 10 and the lens 24. However, since the focal point cannot be visually confirmed, the focal position or focal length f_c of the optical system 10 cannot be measured directly. After the optical system 10 is fixed, the focus indicator is positioned between the lens 24 and the optical system 10.

When the focus indicator is located between the lens 24 and the optical system 10, the light irradiated from the interferometer 20 is all reflected by the spherical reflector 120 and does not reach the optical system 10. At this time, when the center position of the spherical reflector 120 and the focal position of the optical system 10 coincide with each other, the light reflected after reaching the spherical reflector 120 is all directed to the lens 24 along the same path as shown in FIG. 5. Since incident again, the interference fringe when the focus indicator is not positioned and the interference fringe when the focus indicator is positioned are the same.

However, if the center position of the spherical reflector 120 and the focal position of the optical system 10 do not coincide with each other, some of the reflected light after reaching the spherical reflector 120 may not be incident again into the lens 24, and thus, the focus indicator may be used. The interference fringes when no is positioned and the interference fringes when a focus indicator is placed are different.

Therefore, when the focus indicator is moved in a direction closer to the lens 24 or away from the lens 24, and the interference fringes appearing on the display device 27 are the same as the interference fringes when the focus indicator is not positioned, the spherical shape is spherical. The center position of the reflector 120 is a focal position of the optical system 10. In this case, if the focal length f_c of the optical system 10 is to be known, the distance between the center of the spherical reflector 120 and the optical system 10 is measured, and the distance is defined as the focal length f_c of the optical system 10.

Meanwhile, as described above, one spherical reflector 120 is fixed to the support plate 110, and the spherical reflector 120 has a focal position or focal length f_c when light is incident perpendicularly to the optical system 10. It was used for the measurement. Alternatively, as shown in FIG. 6, five spherical reflectors 120 may be fixed to the support plate 110. At this time, one spherical reflector 120 is fixed to the center of the support plate 110 and four spherical reflectors 120 are fixed around it. The shape and size of the four spherical reflectors 120 connected to each other are the same as the shape and size of the device (image sensor 12 in the case of a camera) in which an image of an object is formed. The spherical reflector 120 fixed to the center of the support plate 110 is used to measure the focus position or focal length f_c when light is incident vertically into the optical system 10, and the remaining four spherical reflectors 120 are optical systems. (10), it is used to measure the focal position or the focal length f_e when the light is incident obliquely. The number of the spherical reflectors 120 is not limited to five, but may be smaller or larger than that in some cases.

The focal position or the focal length f_e measured when the light enters the optical system 10 at an oblique angle is measured by using the interferometer 20 and the external reflector 30 positioned between the optical system 10 as shown in FIG. 7. ) Is initiated by positioning the tilted relative to the optical system 10 and then operating the interferometer 20. The process after the interferometer 20 is operated is the same as described above.

As described above, although the present invention has been described by way of limited embodiments and drawings, the present invention is not limited thereto and is described below by the person skilled in the art and the technical spirit of the present invention. Of course, it can be variously modified and modified within the scope of equivalent claims.

10: optical system 20: interferometer
22: light source 23: internal reflector
24: lens 25: semi-plated diameter
26: image sensor 27: display device
30: external reflector 110: support plate
120: spherical reflector 130: fixing means

Claims

In the focus indicator used when measuring the focus position or focal length of the optical system located between the interferometer and the reflector,
A support plate positioned between the interferometer and the optical system when measuring a focus position or a focal length of the optical system, the support plate being provided to move closer to or farther from the interferometer; And
And a spherical reflector fixed to the support plate to reflect light emitted from the interferometer.
A plurality of spherical reflectors are fixed to the support plate, and any one of the plurality of spherical reflectors is used to measure a focal position or a focal length of the optical system when light is incident vertically into the optical system, and the light is obliquely incident to the optical system. Focus indicator, characterized in that used when measuring the focus position or focal length of the optical system.

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