JP2012027240A - Working distance measuring apparatus and working distance measuring method of finite type lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a working distance measuring apparatus and a working distance measuring method that can accurately measure a working distance of a finite type lens such as a coupling lens with simple work and in a short period.SOLUTION: A working distance measuring apparatus for a finite type lens includes a first light source that emits a first laser beam so as to be condensed at a condensation point, condensation point moving means that moves the condensation point, first distance measuring means that measures a movement distance of the condensation point, a lens holding member that holds a test lens, lens moving means that moves the lens holding member, second distance measuring means that measures a movement distance of the test lens, a lens unit having positive power toward the first light source side, a second light source that makes a second laser beam that is parallel light enter the lens unit from the opposite side from the test lens, and photographing means that picks up an image by the first or second laser beam at a focal position of the lens unit.

Description

  The present invention relates to a working distance measuring device and a working distance measuring method for measuring a working distance of a finite system lens used for a coupling lens or the like of an optical communication device.

  An optical communication apparatus that performs communication using an optical fiber, like the apparatus described in Patent Document 1, collects a laser diode that emits laser light, and the laser light emitted from the laser diode and enters the optical fiber. And a coupling lens to be incident on the end.

  In order to perform the above communication, it is necessary to ensure that the laser beam as the carrier wave is condensed at the incident end of the optical fiber. In order to accurately collect the laser light at the incident end of the optical fiber, it is necessary to accurately position the incident end of the optical fiber at the condensing position of the laser light.

JP 7-191237 A

  In recent years, miniaturization of optical communication devices has progressed, and the allowable range of the distance between the coupling lens and the incident end of the optical fiber has become extremely narrow. For this reason, in order to be able to condense the laser light at the incident end of the optical fiber, the working distance of the coupling lens (the distance from the coupling lens to the condensing position of the laser light) falls within a certain range. There is a need.

  Therefore, it can be said that measuring the working distance of the coupling lens in advance is extremely useful from the viewpoint of improving the production yield of the optical communication device. Conventionally, the shape of the lens surface of the coupling lens is measured, and the working distance is calculated based on the measurement result. However, the estimation of the working distance by the above measuring method takes time, and the calculation result of the working distance includes many errors.

  In view of the above problems, the present invention provides a working distance measuring apparatus and a working distance measuring method capable of accurately measuring the working distance of a finite lens such as a coupling lens in a simple operation and in a short time. With the goal.

  In order to achieve the above object, a working distance measuring apparatus for a finite system lens according to the present invention includes a first light source that emits the first laser beam so as to be condensed at a condensing point, and the first laser beam. A condensing point moving means for moving the condensing point in a direction along the optical path of the first laser light, a first distance measuring means for measuring a moving distance of the condensing point by the condensing point moving means, and a first A lens holding member for holding the test lens so that the optical path of the laser beam of the laser beam coincides with the optical axis of the test lens which is a finite system lens, and the lens holding member in a direction along the optical path of the first laser light A lens moving means to be moved; a second distance measuring means for measuring a moving distance of the test lens by the lens moving means; and a first laser disposed on the opposite side of the first light source with respect to the test lens. The first light source is positioned so that the optical path of the light coincides with the optical axis And a second laser beam that is incident on the lens unit from the opposite side of the lens to be tested in the direction along the optical axis of the lens unit. A light source and a photographing means for photographing an image by the first or second laser light at the focal position of the lens unit, and the focusing point moving means is in a state where the lens to be examined is not attached to the lens holding member Then, the imaging means moves the condensing point to a first position where a point image by the first laser beam is obtained, and the lens moving means reflects the light from the surface of the lens to be examined and passes through the lens unit. The lens holding member is moved to a second position so as to obtain a point image by the second laser light, and the lens moving means is moved to a third position close to the first light source by a predetermined distance from the second position. Move the lens holding member and focus The moving means moves the focusing point to a fourth position where the imaging means obtains a point image by the first laser light, and the second distance measuring means moves from the second position to the third position. The first distance measuring means measures the distance from the first position to the fourth position.

  With such a configuration, the working distance of the test lens can be obtained in a short time by measuring the distance from the second position to the third position and the distance from the first position to the fourth position. Is possible.

  In addition, the first laser beam and the second laser beam are preferably laser beams having the same wavelength.

  Since the refractive index of the material constituting the lens varies depending on the wavelength of the incident light, the working distance can be more accurately determined if the wavelengths of the first laser beam and the second laser beam are equal. Can be requested.

  Further, the lens moving means may be configured such that the lens holding member can be moved in three orthogonal directions including the direction along the optical path of the first laser beam.

  The first and second laser beams may be infrared light, and the photographing unit may include an imaging element having high sensitivity to visible light and a filter that converts infrared light into visible light. Good.

  When the test lens is a lens that is premised on input of infrared light, such as a coupling lens for guiding infrared laser light to an optical fiber, the first lens for measuring the working distance is used. Further, the working distance can be determined more accurately by using infrared light as the second laser light. Ordinary (inexpensive for visible light) imaging means incorporating a silicon-based image sensor cannot normally capture an image of infrared light with high sensitivity. However, as in the above-described configuration of the present invention, infrared imaging is not possible. By providing a filter that converts light into visible light, an infrared image can be taken with high sensitivity.

  As described above, according to the present invention, a working distance measuring device for a finite system lens capable of accurately measuring the working distance of a finite system lens such as a coupling lens in a short time is realized.

FIG. 1 is a block diagram of a working distance measuring apparatus for a finite lens according to an embodiment of the present invention. FIG. 2 is a side view of the working distance measuring device according to the embodiment of the present invention in a region from the light source unit to the lens unit. FIG. 3 is a side view of the working distance measuring device according to the embodiment of the present invention in a region from the light source unit to the lens unit. FIG. 4 is a side view of the working distance measuring device according to the embodiment of the present invention in a region from the light source unit to the lens unit.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a working distance measuring apparatus according to this embodiment. The working distance measuring device 1 of the present embodiment includes a main light source unit 10, a light source moving stage 20, a sample stage 30, a sample stage moving stage 40, a lens unit 50, an incident light source unit 60, a television camera 70, and a point image display. Means 90 are provided.

  The main light source unit 10 includes a laser diode 11, a collimator lens 12, a diaphragm 13, and a condenser lens 14 arranged in a line in this order. The specification (laser light wavelength) of the laser diode 11 is the light incident on the test lens L when the test lens L whose working distance is measured by the working distance measuring device 1 of this embodiment is actually used. The wavelength is selected according to the wavelength. For example, if the test lens L is used as a coupling lens for optical communication, the laser diode 11 that emits infrared laser light used in optical communication is selected.

  Laser light emitted from the laser diode 11 is converted into parallel light by the collimator lens 12, adjusted to a constant diameter by the diaphragm 13, and then in front of the lens L (that is, the main light source unit 10 and the focusing lens 14). The light is condensed at a condensing point P1 located between the lens L).

  In order for the laser light to be condensed at the condensing point P1 as described above, the traveling direction of the laser light emitted from the laser diode 11 and the optical axes of the collimator lens 12 and the condensing lens 14 are the same axis (hereinafter referred to as the following). , Referred to as an optical axis OA1). For this reason, the optical path of the laser light emitted from the main light source unit 10 is along the optical axis OA1. In addition, the condensing point P1 is also located on the optical axis OA1.

  The main light source unit 10 can be moved in the direction along the optical axis OA1 by the light source moving stage 20. By operating the light source moving stage 20, the position of the condensing point P1 can be moved on the optical axis OA1. Further, the light source moving stage 20 also has a function as a distance measuring means for obtaining a moving distance of the main light source unit 10. For example, the light source moving stage 20 moves the main light source unit 10 by a feed screw mechanism and obtains a moving distance of the main light source unit 10 by a rotary encoder attached to the feed screw.

  The sample stage 30 holds the test lens L so as to transmit the laser light incident on the test lens L. The sample stage 30 can be moved in the three orthogonal directions by the sample stage moving stage 40. The sample stage 30 holds the test lens L such that the optical axis OA2 of the test lens L is parallel to the optical axis OA1 of the main light source unit 10 in a state where the test lens L is held. Further, the sample stage moving stage 40 has a function as a distance measuring means for obtaining the moving distance of the sample stage 30, similarly to the light source moving stage 20.

  The lens unit 50 is disposed on the lower side of the sample stage 30 (the side that is distal to the main light source unit 10) and in proximity to the sample stage 30. The lens unit 50 is a so-called combined lens in which a plurality of lenses are combined, and has a positive power as a whole. The lens unit 50 is positioned so that the optical axis OA3 thereof coincides with the optical axis OA1 of the light source unit.

  The television camera 70 is disposed on the lower side of the lens unit 50 (a position distal to the main light source unit 10). Further, the optical axis OA4 of the optical system of the television camera 70 is parallel to the optical axis OA3 of the lens unit 50 and is substantially equal to the optical axis OA3. Note that the television camera 70 of the present embodiment includes a general image sensor that can capture an image of visible light with high sensitivity. However, if the laser light emitted from the main light source unit 10 or the epi-illumination light source unit 60 has a low sensitivity in the general image sensor as in the case of infrared light, the infrared light is placed on the optical axis OA4. It is also possible to insert a filter that converts the wavelength of light into visible light. As described above, in this embodiment, even if the lens L to be tested is a lens for infrared light, an inexpensive television camera for visible light 70 is used without using an expensive camera for infrared light. Can be used to measure the working distance of the lens L.

  A half mirror 81 and an imaging lens 82 are disposed between the lens unit 50 and the television camera 70. The half mirror 81 is located on the lens unit 50 side, and the imaging lens 82 is located on the television camera 70 side. The optical axis OA5 of the imaging lens 82 coincides with the optical axis OA4 of the television camera 70. In addition, the imaging lens 82 is disposed at a position where a point image is displayed on the image captured by the television camera 70 when parallel light parallel to the optical axis OA4 is incident from the lens unit 50 side.

  The point image display means 90 includes an image processing device 91 and a monitor 92. The video signal of the video imaged by the television camera 70 is sent to the image processing device 91. The pixel processing device 91 processes the video signal sent from the television camera 70 (for example, brightness adjustment processing) and causes the monitor 92 to display the video signal. As a result, an image taken by the television camera 70 is displayed on the monitor 92.

  The incident light source unit 60 includes a laser diode 61 and a collimator lens 62. The laser diode 61 emits laser light having the same wavelength as the laser light emitted from the laser diode 11 of the main light source unit 10. The laser light emitted by the laser diode 61 becomes parallel light by the collimator lens 62. Laser light emitted from the epi-illumination light source unit 60 enters the half mirror 81.

  The half mirror 81 bends the laser light emitted from the incident light source unit 60 so as to travel on the optical axis OA3 of the lens unit 50, and transmits the laser light emitted from the lens unit 50 toward the television camera 70. Thus, the laser beam proceeds in the direction along the optical axis OA5 of the imaging lens 82.

  The procedure for measuring the working distance of the lens L to be measured by the working distance measuring apparatus 1 of the present embodiment described above will be described below with reference to FIGS. 2 to 4 both show side views of the working distance measuring device 1 in a region from the main light source unit 10 to the lens unit 50.

  Before measuring the working distance of the test lens L, the origin of the position of the main light source unit 10 is set. Specifically, as shown in FIG. 2, the user of the working distance measuring device 1 turns on the laser diode 11 (FIG. 1) of the main light source unit 10 with no lens attached to the sample table 30. Then, the light source moving stage 20 is operated to place the main light source at a position where the condensing point of the laser light B1 from the main light source unit 10 by the condensing lens 14 (FIG. 1) coincides with the focal point P2 of the lens unit 50. Move part 10. More specifically, the main light source unit 10 is moved to a position where the image by the laser beam B1 from the main light source unit 10 is displayed as a point image on the monitor 92 (FIG. 1). Light that is focused at the focal point P2 of the lens unit 50 and whose traveling direction coincides with the optical axis OA3 of the lens unit 50 becomes parallel light when passing through the lens unit 50, and a point image is displayed on the monitor 92. Become. The position of the main light source unit 10 at this time is defined as a light source unit origin Po0.

  Next, the user of the working distance measuring apparatus 1 turns off the laser diode 11 of the main light source unit 10, attaches the lens L to be tested to the sample stage 30, and turns on the laser diode 61 (FIG. 1) of the incident light source unit 60. To do. Next, the user of the working distance measuring apparatus 1 operates the sample stage moving stage 40 so that the point P3 where the lens surface R2 of the lens L on the lens unit 50 side intersects with the optical axis OA2 of the lens L to be tested. The sample stage 30 is moved so as to coincide with the focal point P2 of the lens unit 50 (FIG. 3). Specifically, the user of the working distance measuring apparatus 1 operates the sample stage moving stage 40 so that a point image is displayed on the monitor 92. The laser light emitted from the incident light source unit 60 is reflected by the half mirror 81, passes through the lens unit 50, and enters the lens L to be examined. Here, the laser light incident on the test lens L is focused on the focal point P2, but when the lens surface R2 is located on the focal point P2 and the incident light is reflected by the lens surface R2 (point P3), The reflected laser beam B2 takes the same optical path as the incident light. That is, the reflected laser beam B2 becomes parallel light by the lens unit 50, passes through the half mirror 81, and forms an image on the television camera 70 by the imaging lens 82. Accordingly, when the point P3 where the lens surface R2 of the lens L on the lens unit 50 side intersects with the optical axis OA2 of the lens L coincides with the focal point P2 of the lens unit 50, a point image is displayed on the monitor 92. Will be displayed. The position of the sample stage 30 at this time is defined as a sample stage origin Ps0.

  Next, the user of the working distance measuring device 1 turns off the laser diode 61 of the incident light source unit 60 and turns on the laser diode 11 of the main light source unit 10. Next, the user of the working distance measuring device 1 operates the sample stage moving stage 40 to place the test lens L at the design position (the distance from the focal point P2 of the lens unit 50 to the point P3 of the test lens L is predetermined). It is moved to a position where the distance is d1 (FIG. 4). In the present embodiment, the point P3 of the test lens L is designed so as to be located on the same plane as the surface on which the test lens L abuts on the sample stage 30. Accordingly, by moving the sample stage 30 to the main light source unit 10 side so that the distance from the sample stage origin Ps0 of the sample stage 30 is d1, the distance from the focal point P2 of the lens unit 50 to the point P3 of the lens L to be examined. The distance is set to a predetermined distance d1. The position of the sample stage at this time is Ps1. If the point P3 of the test lens L is not located on the same plane as the surface on which the test lens L abuts on the sample stage 30, the point P3 and the test lens L abut on the sample stage 30. What is necessary is just to move the lens L by offsetting the distance from the surface.

  Further, the user of the working distance measuring device 1 operates the light source moving stage 20 so that the focal point of the laser light B1 from the main light source unit 10 by the lens L to be matched with the focal point P2 of the lens unit 50. The main light source unit 10 is moved to such a position. More specifically, the main light source unit 10 is moved to a position where the image by the laser beam B1 from the main light source unit 10 is displayed as a point image on the monitor 92 (FIG. 1). The position of the main light source unit 10 at this time is Po1.

  As described above, the light source moving stage 20 can measure the moving distance of the main light source unit 10 from the light source unit origin Po0. That is, the distance d2 between the positions Po1 and Po0 can be measured. This interval d2 is equal to the interval (distance between object images) from the focal point P4 of the laser beam B1 from the main light source unit 10 to the focal point of the lens unit 50 in this state.

  The working distance Wd of the test lens L passes through the test lens L when light that is condensed at the focal point P2 of the lens unit 50 is incident on the lens surface R2 of the test lens L on the lens unit 50 side. The distance between the collected light position and the flange portion Lf around the lens surface R2 of the lens L to be measured. Here, the surface Lt of the flange portion Lf on the main light source unit 10 side is a flat surface, and the distance d3 from the surface Lt to the point P3 is measured in advance using a three-dimensional shape measuring device or the like. Therefore, the working distance Wd of the test lens L is calculated from the following formula 1.

  As described above, the working distance Wd of the test lens L can be measured by using the working distance measuring device 1 of the present embodiment.

  In addition, it is preferable that the calculation of Formula 1 is automatically performed by a CPU or personal computer (not shown).

DESCRIPTION OF SYMBOLS 1 Working distance measuring apparatus 10 Main light source part 20 Light source movement stage 30 Sample stage 40 Sample stage movement stage 50 Lens unit 60 Incident light source part 70 Television camera

Claims (5)

A first light source that emits the first laser light so as to be condensed at a condensing point;
Condensing point moving means for moving the condensing point of the first laser light in a direction along the optical path of the first laser light;
First distance measuring means for measuring a moving distance of the condensing point by the condensing point moving means;
A lens holding member that holds the test lens so that the optical path of the first laser beam and the optical axis of the test lens that is a finite system lens coincide with each other;
Lens moving means for moving the lens holding member in a direction along the optical path of the first laser beam;
Second distance measuring means for measuring a moving distance of the lens to be examined by the lens moving means;
It is disposed on the opposite side to the first light source with respect to the test lens, is positioned so that the optical path and the optical axis of the first laser light coincide with each other, and has positive power on the first light source side. A lens unit having
A second light source for allowing a second laser beam, which is parallel light, to enter the lens unit from a side opposite to the lens to be tested in a direction along the optical axis of the lens unit;
Photographing means for photographing an image by the first or second laser light at a focal position of the lens unit;
The condensing point moving means has the condensing point at a first position where the imaging means obtains a point image by the first laser light in a state where a test lens is not attached to the lens holding member. Move and
The lens moving means moves the lens holding member to a second position where the imaging means obtains a point image by the second laser light reflected by the surface of the lens to be examined and passing through the lens unit. And
The lens moving means moves the lens holding member to a third position close to the first light source by a predetermined distance from the second position;
The condensing point moving means moves the condensing point to a fourth position where the imaging means obtains a point image by the first laser beam,
The second distance measuring means measures a distance from the second position to the third position;
The working distance measuring device for a finite system lens, wherein the first distance measuring means measures a distance from the first position to the fourth position.   2. The working distance measuring device for a finite system lens according to claim 1, wherein the first laser beam and the second laser beam are laser beams having the same wavelength.   3. The lens moving unit according to claim 1, wherein the lens moving unit is capable of moving the lens holding member in three orthogonal directions including a direction along an optical path of the first laser beam. Working distance measuring device for finite lenses. The first and second laser lights are infrared light;
4. The apparatus according to claim 1, wherein the photographing unit includes an imaging element having high sensitivity to visible light and a filter that converts infrared light into visible light. 5. The working distance measuring device of the finite system lens described in the item. A first light source that emits the first laser light so as to be condensed at a condensing point;
A lens holding member that holds the test lens so that the optical path of the first laser beam and the optical axis of the test lens that is a finite system lens coincide with each other;
It is disposed on the opposite side to the first light source with respect to the test lens, is positioned so that the optical path and the optical axis of the first laser light coincide with each other, and has positive power on the first light source side. A lens unit having
A second light source for allowing a second laser beam, which is parallel light, to enter the lens unit from a side opposite to the lens to be tested in a direction along the optical axis of the lens unit;
Photographing means for photographing an image by the first or second laser light at a focal position of the lens unit;
A working distance measuring method for a finite system lens using a working distance measuring device for a finite system lens comprising:
Moving the condensing point to a first position where the imaging means obtains a point image by the first laser light in a state where the lens to be examined is not attached to the lens holding member;
Moving the lens holding member to a second position where the imaging means obtains a point image by the second laser light reflected on the surface of the lens to be examined and passing through the lens unit;
Moving the lens holding member to a third position close to the first light source by a predetermined distance from the second position;
Moving the condensing point to a fourth position where the imaging means obtains a point image by the first laser beam;
Measuring a distance from the second position to the third position;
Measuring a distance from the first position to the fourth position;
Calculating a working distance of the test lens based on a distance from the second position to the third position and a distance from the first position to the fourth position;
A method for measuring a working distance of a finite lens characterized by comprising:

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