JP2007047043A - Multi-wavelength interferometer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multi-wavelength interferometer capable of carrying out an interference measurement using multiple wavelengths without moving an optical element to be measured. <P>SOLUTION: The multi-wavelength interferometer comprises a plurality of laser light sources 11a-11c for emitting light beams having different wavelengths, a mirror and a half mirror for reflecting laser beams which are emitted by respective laser light sources 11a-11c, toward an interference measuring section, and a light source switching mechanism 17 which is disposed between the light sources and the interference section alternatively selects laser beams emitted by the respective laser light sources 11a-11c and brings the selected laser beam to enter the interference measuring section. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a multiwavelength interferometer capable of measuring at different wavelengths.

  In recent years, optical recording apparatuses that record and reproduce various optical recording media with a single device have been developed. In such an optical recording apparatus, the same condenser lens is used when writing a signal to the recording medium and when reading the written signal, and laser light having a different wavelength is used for each optical recording medium system. The lens uses the same objective lens.

Conventionally, an interferometer has been used as a means for measuring the characteristics of such an objective lens. A conventional interferometer has a configuration in which coherent light is divided and measurement light transmitted through a lens to be measured and reference light reflected by a reference mirror are overlapped to interfere with each other.
JP 7-181005 A

  However, since the conventional interferometer can only measure with a light beam having a single wavelength, an interferometer must be prepared for each wavelength, and the lens to be measured must be moved to each interferometer.

  The present invention has been made in view of such a problem, and an object of the present invention is to obtain a multi-wavelength interferometer capable of measuring interference with a plurality of wavelengths without moving the optical element to be measured.

  The present invention that solves such a problem is an interferometer that includes an interference unit that splits light incident from a light source and causes measurement light transmitted or reflected by a measured optical element to interfere with reference light reflected by a reference mirror. A plurality of light sources that emit light of different wavelengths, a reflective optical element that reflects the light emitted from each light source in the direction of the interference unit, and the light source disposed between the light source and the interference unit, There is provided a light source switching means for selectively making the light emitted from each of the light sources incident on the interference section.

  In a preferred embodiment, the plurality of light sources are arranged away from each other in a direction orthogonal to the traveling direction of the emitted light, and the reflective optical element is emitted from a light source farthest from the interference unit among the light sources. A mirror that reflects light toward the interference unit, and a half mirror that reflects light emitted from a light source closer to the interference unit than the farthest light source toward the interference unit, and is closest to the interference unit The light emitted from the light source farther than the light source and reflected by the half mirror or mirror is formed so as to pass through the other half mirror in the optical path and enter the interference portion.

Each of the light sources, the mirror and the half mirror is arranged so that an optical axis or an optical center is located on the same plane, and the light source switching means is arranged in an optical path between each of the light sources and the mirror and the half mirror, It is preferable to selectively transmit light from the light source.
The light source switching means includes a light shielding plate disposed between the mirror and the half mirror and the light source and extending in the light source arrangement direction, and an opening provided in the light shielding plate. When one opening is located in an optical path that allows transmission of light emitted from the corresponding light source, the other opening is provided so as to be out of the optical path of the corresponding light source.
It is preferable that the light source is arranged closer to the interference portion as the light source has a shorter wavelength.

  According to the present invention, since light of different wavelengths can be selectively guided to the interference unit, interference measurement using light of a plurality of wavelengths can be performed without moving the measured optical element. In addition, since the optical element for guiding the light from the light source does not move, no error occurs due to the movement. Furthermore, since interference measurement can be performed by a single interference unit, cost reduction can be achieved.

  The present invention will be described in detail with reference to the illustrated embodiments. FIG. 1 is a front view showing a main configuration of an embodiment of a multiwavelength interferometer to which the present invention is applied.

  In this embodiment, three laser light sources 11a, 11b, and 11c that emit laser beams having different wavelengths are provided. The first laser light source 11a emits laser light having a wavelength of about 405 nm, the second laser light source 11b emits laser light having a wavelength of about 660 nm, and the third laser light source 11c emits laser light having a wavelength of about 780 nm. That is, the first laser light source 11a is a so-called Blu-ray disc device, the second laser light source 11b is a DVD device, and the third laser light source 11c is a light source that emits laser light for a CD device. In this embodiment, the light path length is shorter as the light source has a shorter wavelength. This is because the shorter the laser beam, the greater the attenuation and the more easily affected by the optical elements in the path.

  The laser light emitted from the laser light sources 11a to 11c is once diverged after being diverged by the diverging lenses 13a, 13b, and 13c, and then collimated into parallel light beams by the collimating lenses 15a, 15b, and 15c. The parallel laser beams emitted from the collimating lenses 15a, 15b, and 15c are controlled so as to be selectively transmitted by the light source switching mechanism 17 serving as a light source switching unit. The light source switching mechanism 17 has a structure that transmits any one of the laser beams emitted from the collimating lenses 15a, 15b, and 15c. Each of the laser light sources 11a to 11c maintains a normal light emission state during measurement in order to stabilize the wavelength and intensity.

  The laser light emitted from the first laser light source 11a and transmitted through the light source switching mechanism 17 is reflected by the half mirror 19a toward the measurement lens unit 23 (measured optical element) constituting the measurement unit. The laser light emitted from the second laser light source 11b and transmitted through the light source switching mechanism 17 is reflected by the half mirror 19b toward the measurement lens unit 23 and passes through the half mirror 19a. The laser light emitted from the third laser light source 11c and transmitted through the light source switching mechanism 17 is reflected by the mirror 19c toward the measurement lens unit 23 and passes through the half mirrors 19b and 19a.

  The laser light sources 11a to 11c, the diverging lenses 13a to 13c, the collimating lenses 15a to 15c, and the mirrors 19a to 19c are arranged such that their optical axes Oa, Ob, Oc, or optical centers are located on the same plane. Yes.

  The laser light reflected or transmitted by the half mirror 19 a is incident on the half mirror 21, and part of the laser light is transmitted through the half mirror 21 and is incident on the measurement lens unit 23. The measurement lens unit 23 includes a reflection reference concave mirror 24, and the lens L to be measured is placed in front of the reflection reference concave mirror 24. The lens L to be measured is arranged so that its focal point FL coincides with the focal point F of the reflective reference concave mirror 24.

  Furthermore, in this embodiment, the focal point FL of the lens L to be measured coincides with the focal point F of the reflecting reference concave mirror 24 according to the focal position (focal length) of the lens L to be measured that varies according to the wavelength of the laser light to be used. A cover glass 25 (for example, thickness, 0.1 mm for Blu-ray Disc, 0.6 mm for DVD, 1.2 mm for CD) that adjusts the position of the reflective reference concave mirror 24 and its wavelength specification The lens L and the reflecting reference concave mirror 24 are arranged so as to be switched.

  The laser light that has passed through the cover glass 25 and the lens L to be measured, reflected by the reflection reference concave mirror 24, and again transmitted through the lens L and the cover glass 25 to be measured returns to the half mirror 21 and is directed toward the half mirror 29 by the half mirror 21. The laser beam reflected and reflected by the half mirror 29 enters the interference fringe observation unit 31. The laser beam reflected by the half mirror 21 is reflected by the reference plane plate 27 and returns to the half mirror 21, passes through the half mirror 21, is reflected by the half mirror 27, and enters the interference fringe observation unit 31.

  The measurement laser light that has entered the interference fringe observation unit 31 and has passed through the lens L to be measured reflected by the reflection reference concave mirror 24 and the reference laser light reflected by the reference plane plate 27 are collected by the condenser lens 32 and are then collected by the CCD camera. 33 is incident. The measurement laser light and the reference laser light incident on the imaging surface of the CCD camera 33 interfere with each other to form an interference fringe, and the image sensor picks up the interference fringe.

  Further, in this embodiment, the measurement laser light reflected by the reflection reference concave mirror 24, reflected by the half mirror 21, and transmitted through the half mirror 29 enters the CCD camera 35. A point image corresponding to the focal point FL position of the lens L to be measured is formed on the imaging surface of the CCD camera 35 and imaged.

  Images captured by the CCD cameras 33 and 35 are displayed on a monitor television. The image picked up by the CCD camera 33 shows interference fringes, and the image picked up by the CCD camera 35 shows dot fringes. The coma aberration is measured by the interference fringes projected on the monitor TV. On the other hand, the decentration and tilt state of the lens L to be measured can be measured by the position of the point image displayed on the monitor television.

  FIG. 2 shows an enlarged view of the measurement lens unit 23. A lens L to be measured, a cover glass (optical flat) 25, and a reflective reference concave mirror 24 are arranged in this order along the direction in which the laser light transmitted through the half mirror 21 travels. The laser light (parallel light beam) incident on the lens L to be measured is converged by the lens L to be measured, passes through the cover glass 25, and then converges and then diffuses and is reflected by the reflective reference concave mirror 24, and passes through the incident optical path. Backlit and emitted as a parallel light beam from the lens L to be measured.

  Furthermore, in this embodiment, the focal point FL of the lens L to be measured coincides with the focal point F of the reflecting reference concave mirror 24 according to the focal position (focal length) of the lens L to be measured that varies according to the wavelength of the laser light to be used. A cover glass 25 (for example, thickness, 0.1 mm for Blu-ray Disc, 0.6 mm for DVD, 1.2 mm for CD) that adjusts the position of the reflective reference concave mirror 24 and its wavelength specification The lens L and the reflecting reference concave mirror 24 are arranged so as to be switched.

  FIG. 3 shows an embodiment of the light source switching mechanism 17. In this embodiment, openings 171a, 171b and 171c are provided at predetermined intervals in a light shielding plate 171 extending in the arrangement direction of the laser light sources 11a, 11b and 11c. The height and width of each opening 171a, 171b, 171c are set to be equal to or slightly larger than the beam diameter of the laser light emitted from the collimating lenses 15a, 15b, 15c. Further, the distance D between the openings 171a, 171b, 171c is the distance between the laser light sources 11a, 11b, 11c, that is, the distance between the optical axes Oa, Ob, Oc (pitch d1) and the height (d2) of each opening 171a, 171b, 171c. A little wider than the sum of That is, D> (d1 + d2) is set. The shape of the openings 171a, 171b, and 171c is not limited to a square, and may be a polygon or a circle.

  The light shielding plate 171 shields the optical paths of the other laser light sources 11b and 11c at a position where the opening 171a matches the optical path of the laser light source 11a and the optical path is opened (FIG. 3A). When the light shielding plate 171 is moved downward by a pitch D in FIG. 1, the opening 171b matches the optical path of the laser light source 11b and opens the optical path, while the optical paths of the other laser light sources 11a and 11c are shielded by the light shielding plate 171. (FIG. 3B). When the light shielding plate 171 is further moved downward by the pitch D, the opening 171c matches the optical path of the laser light source 11c and opens the optical path, while the optical paths of the other laser light sources 11a and 11c are shielded by the light shielding plate 171. (FIG. 3C).

  A mechanism for moving the light shielding plate 171 to the respective positions can be formed using a known mechanism. For example, the light-shielding plate 171 is supported so as to be movable in parallel in the vertical direction, and a mechanism that holds it by a click stop mechanism or the like at every pitch D, or a rack is formed at the edge in the vertical direction, and a pinion is engaged with the rack and moved. It is formed by a rack and pinion mechanism.

  As described above, according to the embodiment of the present invention, since the plurality of laser light sources 11a to 11c can be switched only by driving the light source switching mechanism 17, the lens to be measured is moved by the measurement using laser light of different wavelengths. It can be executed easily without any problems. In addition, since optical elements such as mirrors and half mirrors that affect the path of the laser beam are not moved, there is no risk of the optical path shifting. Since the laser light sources 11a to 11c are arranged in a vertical line, the installation area can be reduced. A cover glass 25 corresponding to the selected laser light sources 11a to 11c is inserted into the optical path.

  Although the illustrated embodiment has a configuration in which three laser light sources 11a to 11c having different wavelengths can be switched, the present invention can also be applied to two or four or more laser light sources.

  Although the illustrated light source switching mechanism is configured to move one light shielding plate in the vertical direction, in another embodiment, each opening is formed by shifting in the horizontal direction, and the light shielding plate is moved in the horizontal direction. Further, a movable light shielding plate, a diaphragm or a shutter may be provided for each laser light source, and these may be selectively opened.

  In the illustrated embodiment, the laser light sources 11a to 11c are arranged in a vertical row. However, in another embodiment, the laser light sources 11a to 11c are arranged at different positions around the optical path passing through the plan view, the mirror, and the half mirror. In short, a configuration is adopted in which light from a plurality of light sources is incident on the interference unit by a mechanism that selectively transmits light. With the above configuration, it is possible to perform interference measurement for each light of different wavelengths without moving the optical element to be measured, and it is possible to shorten the measurement time and the work process.

It is a figure which shows the whole outline | summary of embodiment of the multiwavelength interferometer to which this invention is applied. It is a figure which expands and shows the member holding a to-be-measured lens, and the structure of the periphery. It is a figure which shows the state which permeate | transmits the laser beam from a different laser light source for one Example of the light source switching mechanism of the embodiment.

Explanation of symbols

11a 11b 11c Laser light source 13a 13b 13c Diverging lens 15a 15b 15c Collimating lens 17 Light source switching mechanism 19a 19b Half mirror 21 Half mirror 23 Measuring lens unit 24 Reflection reference concave mirror 25 Cover glass 27 Reference plane plate 29 Half mirror 31 Interference fringe observation unit 33 CCD camera

Claims (5)

An interferometer comprising an interference unit that splits light incident from a light source and causes measurement light transmitted or reflected by a measured optical element to interfere with reference light reflected by a reference mirror,
A plurality of light sources that emit light of different wavelengths;
A reflective optical element that reflects the light emitted from each light source toward the interference portion;
A multi-wavelength interferometer, comprising: a light source switching unit that is disposed between each light source and the interference unit and selectively makes light emitted from each light source enter the interference unit. 2. The multiwavelength interferometer according to claim 1, wherein the plurality of light sources are arranged apart from each other in a direction orthogonal to a traveling direction of the emitted light, and the reflective optical element is closest to the interference unit among the light sources. A mirror that reflects light emitted from a distant light source in the direction of the interference unit, and a half mirror that reflects light emitted from a light source closer to the interference unit than the farthest light source in the direction of the interference unit, A multiwavelength interferometer in which light emitted from a light source farther than the light source closest to the interference unit and reflected by a half mirror or mirror passes through the other half mirror in the middle of the optical path and enters the interference unit. 3. The multi-wavelength interferometer according to claim 2, wherein each of the light sources, the mirror, and the half mirror is disposed such that an optical axis or an optical center is located on the same plane, and the light source switching means includes the light sources, the mirror, A multi-wavelength interferometer that is disposed in an optical path between the half mirrors and selectively transmits light from the light source. 4. The multi-wavelength interferometer according to claim 2, wherein the light source switching unit is disposed between the mirror and the half mirror and the light source, and extends to the light source arrangement direction and the light shielding plate. When one of the openings is located in an optical path that allows transmission of light emitted from the corresponding light source, the other opening deviates from the optical path of the corresponding light source. A multi-wavelength interferometer provided. 5. The multi-wavelength interferometer according to claim 1, wherein a light source having a shorter wavelength is arranged near the interference unit. 6.

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