JP2006023279A - Wave front measuring interferometer unit, and light beam measuring instrument and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wave front measuring interferometer unit provided with a compact optical system of simple constitution, and capable of regulating easily the optical system, and a light beam measuring instrument and method capable of measuring a wave front of a light beam and measuring a characteristic of a light beam spot. <P>SOLUTION: This light beam measuring instrument 10A is provided with a beam splitter 13 for splitting the light beam emitted from a light source part 11 into two beams, a semi-transparent reflection face 15a for reflecting one portion of the separated one light beam as a inspected light beam to a direction reverse to an incident direction, and a reflection type reference light generating means 23 for converting one portion of the transmitted light beam transmitted through the semi-transparent reflection face 15a into a wave front-faired reference light beam to be output. The wave front of the light beam, and the characteristic of the light beam spot are measured by such a manner. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a wavefront measuring interferometer apparatus that performs wavefront measurement of a light beam to be measured, and a light beam measuring apparatus and method that perform wavefront measurement of the light beam and various measurements at a focused spot of the light beam. It is about.

  Conventionally, a spot image is formed by forming a light beam to be measured in a dot shape on an imaging surface such as a CCD, and measuring the shape and size of the spot image, intensity distribution, barycentric coordinates, etc. An apparatus (also referred to as a beam profiler) that collectively refers to these as “light beam spot characteristic measurement” is known (see Patent Document 1 below).

  On the other hand, as an apparatus for measuring the wavefront of a light beam, a wavefront measuring interferometer apparatus having an optical system arrangement of a Mach-Zehnder interferometer as shown in FIG. 8 is known.

  In the wavefront measurement interferometer device shown in FIG. 8, the light beam emitted from the light source unit 101 is separated into two light beams by the beam splitter 102. One of the two light beams is converged by the converging lens 103 and enters the pinhole 104 disposed at the convergence point. The pinhole 104 is configured to have a smaller diameter than the diffraction limit of the converged light beam, and an ideal spherical wave whose wavefront is shaped is emitted from the back surface side of the pinhole 104. The spherical wave enters the collimator lens 105 and is converted into a plane wave, and then is reflected at a right angle by the mirror 106 and enters the beam splitter 107 as reference light.

  The other light beam separated by the beam splitter 102 is reflected by the mirror 108 at a right angle and then converged by the converging lens 109, but no pinhole is disposed at the convergence point. For this reason, wavefront shaping is not performed, and the light beam that has passed through the converging lens 109 is once converged and then diverges to enter the collimator lens 110 to be parallel light, and then enters the beam splitter 107 as test light.

  Interference light is obtained by combining the reference light and the test light in the beam splitter 107, and the interference light is taken into the imaging camera 112 through the imaging lens 111. Based on the interference fringes picked up by the image pickup camera 112, the wavefront of the light beam is measured.

  The pinhole as described above has a function of forming an ideal spherical wave, but the formed spherical wave is emitted to the back side of the pinhole. On the other hand, a device having a function of converting a part of an incident light beam into an ideal spherical wave and reflecting the reflected light in the direction opposite to the incident direction (hereinafter referred to as “reflection diffractive portion”) is also known. Yes. Such a reflection diffraction part is also referred to as a reflection type pinhole or the like, and has a minute reflection region formed on a glass substrate, or a minute reflection region formed at the tip of a needle-like member (Patent Document 2 below) For example) (see the following Patent Document 3).

JP 2004-45327 A JP 2000-97612 A JP 58-60590 A

  The conventional Mach-Zehnder interferometer for wavefront measurement as described above has a symmetrical arrangement of optical elements such as a beam splitter and a mirror, and the two light beams that interfere with each other are symmetrical with respect to each optical path. Therefore, if the optical characteristics of the optical elements arranged symmetrically are made uniform, the aberrations and the like of each optical element hardly have an adverse effect on the measurement result. For this reason, the Mach-Zehnder type wavefront measuring interferometer apparatus is generally used as a highly versatile measuring apparatus for measuring the wavefront of a light beam.

  However, the Mach-Zehnder type interferometer for wavefront measurement has a problem that the adjustment of the optical system is very difficult because the number of parts of the optical system is large and the adjustment points are various. In addition, since the optical path of the reference light and the optical path of the test light have to be arranged spatially apart, there is a problem that the apparatus becomes large. In addition, since the reference light and the test light pass through separate optical paths, there are problems such as being easily affected by vibration and the difficulty of installing a phase shift mechanism.

  The present invention has been made in view of such circumstances, and provides a highly practical wavefront measurement interferometer device that includes a compact optical system with a simple configuration and can easily adjust the optical system. This is the first purpose.

  In addition, no measuring apparatus capable of simultaneously measuring the wavefront of the light beam and measuring the characteristics of the light beam spot has been known. If two measurements can be performed at the same time using a single measuring device, it is possible to compare and analyze the two measurement results in real time, and to greatly reduce the measurement cost. is there.

  The present invention has been made in view of such circumstances, and it is a second object of the present invention to provide a light beam measuring apparatus and method capable of simultaneously measuring the wavefront of a light beam and measuring the characteristics of a light beam spot. And

  In order to achieve the first object, the wavefront measuring interferometer apparatus of the present invention is configured as follows. That is, the interferometer apparatus for wavefront measurement according to the present invention transmits a part of a light beam to be measured as a test light beam in a direction opposite to the incident direction, and transmits through the transflective surface. A converging lens for converging the transmitted light flux and a minute reflection diffraction portion disposed at the convergence point of the converging lens, and a part of the transmitted light beam incident from the semi-transmissive reflection surface is wavefront shaped. A reference light generating means for converting the reference light beam into the semi-transmissive reflection surface, and guiding the interference light formed by combining the reference light beam and the test light beam to the detection surface, An image forming unit for forming interference fringes on the detection surface is provided, and the wavefront measurement of the light beam is performed based on the interference fringes formed on the detection surface. It is.

  In the interferometer for wavefront measurement according to the present invention, at least one of the transflective surface and the reference light generating means is moved in the optical axis direction, thereby adjusting an optical path length adjusting means for adjusting an optical distance therebetween. Or the reference light generating means may be configured to hold a plurality of reflection diffraction portions having different sizes and selectively place one of them at the convergence point.

In order to achieve the second object, the light beam measuring apparatus of the present invention is configured as follows. That is, the light beam measurement apparatus according to the present invention is a light beam measurement apparatus capable of measuring both the wavefront measurement of the light beam to be measured and the spot characteristic measurement of the light beam,
A test / reference beam separating means for separating the light beam into two light beams, a test light beam for wavefront measurement and a reference light beam, and a reference light beam by shaping the wave surface of the reference light beam and converting it to a reference light beam A reference light generating means that interferes with the test light beam and the reference light beam to form an interference fringe image that carries the wavefront information of the test light beam, and an imaging surface of the interference fringe A first light detector provided, and a wavefront measuring unit comprising:
The light beam before entering the test / reference beam separation unit, the test beam after being separated by the test / reference beam separation unit, or the reference beam creation beam before wavefront shaping. A spot creating light beam separating means for separating a part of the spot creating light beam as a spot creating light beam, a spot image generating means for forming the spot creating light beam separated by the spot creating light beam separating means as a spot image, and the spot image And a spot characteristic measuring section having a second photodetector provided on the imaging plane.

  The test / reference light beam separating means reflects a part of the incident light beam as the test light beam in a direction opposite to the incident direction, and transmits the remaining part of the light beam as the reference light beam. It can be a transflective surface.

  Further, the reference light generating means includes a converging lens that converges the reference light beam forming light beam, and a minute reflection diffraction portion disposed at a convergence point of the converging lens. A part of the reference beam forming light beam incident from the separating unit may be wavefront shaped and converted into the reference light beam, and the reference light beam may be emitted toward the test / reference light beam separating unit.

  The light beam measuring apparatus according to the present invention includes a light beam separating unit that separates a light beam to be measured into two light beams, and one of the two light beams separated by the light beam separating unit. A semi-transmissive reflecting surface that reflects a part of the light beam as a test light beam in the direction opposite to the incident direction, a converging lens that converges the transmitted light beam that has passed through the semi-transmissive reflecting surface, and a minute lens disposed at the convergence point of the converging lens A reference diffracting unit, which converts a part of the transmitted light beam incident from the transflective surface into a reference light beam whose wavefront is shaped, and emits the reference light beam toward the transflective surface A first image forming unit for guiding interference light formed by combining the reference light beam and the test light beam to a first detection surface and forming an interference fringe on the first detection surface; And the two luminous fluxes separated by the luminous flux separation means A second image forming unit that forms a spot image of the other light beam on the second detection surface, and measures the wavefront of the light beam based on the interference fringes formed on the first detection surface. And measuring the characteristics of the light beam spot based on the spot image formed on the second detection surface.

  The “fine reflection diffractive part” is determined by the diffraction limit of the convergent light beam condensed (converged) on the reflection diffractive part (preferably configured to be smaller than the diffraction limit). It has a function of reflecting a part of it as a spherical wave having a wavefront shape. As such a reflection diffractive section, it is possible to use various configurations, but as a specific aspect, for example, a micro reflection region formed on a substrate, or a micro reflection at the tip of a needle-like member An example in which a region is formed, or a case in which a reflective surface is arranged in the immediate vicinity of the back side of a pinhole can be cited.

  In addition, the peripheral region of such a reflection diffraction part is configured to have a shape that can suppress the transmission light beam incident on the peripheral region through the converging lens from being reflected toward the converging lens. Is preferred.

  In the light beam measurement apparatus of the present invention, the interference light may be guided to the first detection surface via the beam splitter, or at least one of the transflective surface and the reference light generation unit Can be provided with an optical path length adjusting means for adjusting the optical distance between them.

  In addition, a light shielding unit that blocks an optical path between the transflective reflecting surface and the reference light generation unit, a configuration that can move the reflection diffraction unit to a position off the optical path, or a reference light generation unit A plurality of reflection diffractive parts having different sizes can be held, and one of them can be selectively placed at the convergence point, or the light intensity of the light beam emitted from the light source part can be A power meter to measure can also be provided.

  A first analyzing unit for analyzing the interference fringes to obtain a wavefront measurement result of the light beam; and a second analyzing unit for analyzing the spot image to obtain a characteristic measurement result of the light beam spot of the light beam. Can also be provided.

  The light beam measurement method of the present invention is a light beam measurement method capable of measuring both the wavefront measurement of the light beam to be measured and the spot characteristic measurement of the light beam, After splitting into two light beams, a test light beam for wavefront measurement and a reference light beam, and converting the reference light beam to a reference light beam after wavefront shaping, the test light beam and the reference light beam Interference fringe generation procedure for forming an interference fringe that forms the interference fringe carrying the wavefront information of the test light beam, and the light before being separated into two light beams of the test light beam and the reference light beam The beam, the test light beam after being separated, or a part of the reference light beam for beam shaping before wavefront shaping is separated as a spot image light beam, and the spot image light beam is formed as a spot image. A spot image generation procedure, and A first analysis procedure for obtaining a wavefront measurement result of the light beam by analyzing a fringe pattern; and a second analysis procedure for obtaining a characteristic measurement result of the light beam spot of the light beam by analyzing the spot image. It is characterized by doing.

  According to the interferometer for wavefront measurement according to the present invention, in the conventional Mach-Zehnder type, the two beamsplitters have different functions, that is, the light beam from the light source unit is used as the reference light and the test light. Since the single transflective surface is responsible for the function of demultiplexing and combining these functions, the optical system can be arranged in a simple and compact configuration, and the optical system can also be adjusted. It can be done easily. Therefore, the wavefront measurement can be easily performed on the coherent light such as laser light, and the practicality is extremely high such as easy installation space for the apparatus.

  In addition, according to the light beam measuring apparatus and method of the present invention, the above-described configuration makes it possible to simultaneously perform the wavefront measurement of the light beam and the characteristic measurement of the light beam spot.

  Further, when the test / reference beam separation means is constituted by a semi-transmissive reflection surface, the optical system can be arranged in a simple and compact configuration, and the adjustment of the optical system can be easily performed.

<Interferometer device for wavefront measurement>
Hereinafter, embodiments of a wavefront measuring interferometer device according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of a wavefront measuring interferometer device according to an embodiment of the present invention.

  A wavefront measuring interferometer device 10 shown in FIG. 1 performs wavefront measurement of a light beam emitted from a light source unit 11, and is disposed on an optical path extending rightward in the drawing from the light source unit 11. A splitter 13, a transflective plate 15, a reference light generating means 23, an imaging lens 25 and an imaging camera 27 arranged below the beam splitter 13 in the figure are provided. The wavefront measuring interferometer device 10 also includes a computer 33 that performs various analyzes based on image signals from the imaging camera 27, a display device 34 that displays analysis results and images by the computer 33, and a keyboard and mouse. A device 35 is provided. In the present embodiment, the beam splitter 13, the imaging lens 25, and the imaging camera 27 constitute an imaging unit in the present invention.

  In the present embodiment, the light source unit 11 is formed by appropriately combining a light source body 11a made of a solid laser, a semiconductor laser, a gas laser, or the like with a beam expander, a collimator lens, a cylindrical lens, or the like (used alone). A beam optical system 11b (including a case where it can be used alone), and configured to emit a single longitudinal mode or multi-longitudinal mode light beam as parallel light to the right in the figure. Yes. As the light source body 11a, for example, a light source configured to output laser light from a solid laser or the like via an optical fiber can be used. The light source unit 11 is used as a laser light output device incorporated in various devices, and is not a constituent element of the light beam measurement device 10.

  Details of the components of the wavefront measuring interferometer device 10 will be described below. The transflective plate 15 is held by a fringe scan adapter 36 as optical path length adjusting means. The fringe scan adapter 36 includes a holder 37 and a piezoelectric element 38, and the transflective plate 15 is moved in the optical axis direction by driving the piezoelectric element 38, so that the transflective plate 15 and the reference light generating unit 23 are moved. The optical distance between the two is adjusted. The driving of the piezoelectric element 38 is controlled by the computer 33 via the driver 39.

  The reference light generating means 23 includes a converging lens 17 for converging a parallel light beam incident from the left in the figure to one point, and a reflection diffraction unit 19 disposed at the converging point of the converging lens 17. . The reflection diffractive portion 19 is made of a metal film such as gold, aluminum, or chromium formed on the substrate 21 by vapor deposition or the like, for example, and the size of the reflection diffractive portion 19 is smaller than the diffraction limit of the incident convergent light beam. Is also made smaller.

  Hereinafter, the operation of the wavefront measurement interferometer device 10 during measurement will be described. A part of the light beam emitted to the right in the drawing from the light source unit 11 is directed to the semi-transmissive reflection plate 15 via the beam splitter 13, and is incident on the semi-transmissive reflection surface 15 a of the semi-transmissive reflection plate 15. The test light beam reflected in the direction opposite to the direction and the transmitted light beam that passes through the semi-transmissive reflector 15 and travels toward the reference light generation unit 23 are separated. The light enters the converging lens 17.

  The transmitted light beam incident on the converging lens 17 is converged by the converging lens 17 and is incident on the reflection diffraction unit 19 disposed at the convergence point. A part of the transmitted light beam incident on the reflection diffraction unit 19 is converted into a spherical wave whose wavefront is shaped by the reflection diffraction unit 19, and reflected toward the convergence lens 17. The spherical wave is converted into a plane wave by the converging lens 17 and is emitted toward the transflective plate 15 as a reference light beam.

  The reference light beam passes through the semi-transmissive reflecting plate 15 and is combined with the test light beam reflected by the semi-transmissive reflecting surface 15a, whereby interference light is obtained. The interference light enters the imaging lens 25 via the beam splitter 13 and is taken into the imaging camera 27 via the imaging lens 25. The imaging camera 27 includes a detection surface 27a composed of a solid-state image sensor such as a CCD or CMOS, for example, and images the interference fringes formed on the detection surface 27a via the imaging lens 25. It is configured. The image information of the captured interference fringes is input to the computer 33, and the wavefront measurement of the light beam is performed based on the image information. The fringe scan adapter 36 finely moves the transflective surface 15a in the optical axis direction to pick up an interference fringe while gradually changing the optical path length difference between the reference light beam and the test light beam. By performing the measurement, a more detailed wavefront measurement result can be obtained.

  As described above, according to the wavefront measuring interferometer apparatus 10 of the present embodiment, in the conventional Mach-Zehnder type, the separate functions that the two beam splitters respectively performed, that is, the light beam from the light source unit is used as a reference. Since one transflective surface is responsible for the function of demultiplexing light into the test light and the function of combining them, the optical system can be arranged in a simple and compact configuration. Adjustment of the optical system can be easily performed. Therefore, the wavefront measurement can be easily performed on the coherent light such as laser light emitted from the light source unit 11, and the installation space for the apparatus can be easily secured.

  In addition, until now, the wavefront measurement of multi-longitudinal mode laser light with a very short coherence distance has been used to produce interference fringes with good contrast unless the optical path length difference between the two light beams of the reference light beam and the test light beam is adjusted with high accuracy. Since it cannot be obtained, it has been difficult to adjust the optical system using a conventional interferometer apparatus for wavefront measurement. On the other hand, in the wavefront measuring interferometer apparatus 10 described above, the optical path length difference between the two light beams can be easily adjusted by changing the position of the transflective surface 15a using the fringe scan adapter 36. For this reason, the wavefront measurement of multi-longitudinal mode laser light can also be performed with high accuracy.

  In the embodiment shown in FIG. 1, the transflective plate 15 and the reference light generating means 23 are arranged on the right side of the beam splitter 13 in the drawing, and the separation surface 13a of the light beam incident on the beam splitter 13 from the light source unit 11 is arranged. Although the transmitted light beam is directed to the semi-transmissive reflection surface 15a, the semi-transmissive reflection plate 15 and the reference light generating means 23 are arranged on the upper side of the beam splitter 13 in the drawing, and the light splitter 11 to the beam splitter 13 are arranged. Of the light beam incident on the light beam, the light beam reflected at a right angle by the separation surface 13a may be directed toward the transflective surface 15a.

<Light Beam Measuring Device (First Embodiment)>
Next, an embodiment of a light beam measuring apparatus according to the present invention will be described in detail with reference to the drawings. FIG. 2 is a schematic configuration diagram of the light beam measuring apparatus according to the first embodiment of the present invention.

  A light beam measuring apparatus 10A shown in FIG. 2 is a light beam measuring apparatus capable of measuring both a wavefront measurement of a light beam to be measured and a characteristic measurement of a spot of the light beam. And a spot characteristic measuring unit.

  The wavefront measuring unit includes a test / reference beam separation means (15) for separating the light beam emitted from the light source unit 11 into two beams, a test beam for wavefront measurement and a reference beam generation beam, and a reference A reference light generating means (23) for wavefront shaping the light beam for forming a light beam and converting it into a reference light beam, and an interference fringe carrying the wavefront information of the test light beam are formed by causing the test light beam and the reference light beam to interfere with each other. Interference fringe generating means (25) and a first photodetector (27a) provided on the image plane of the interference fringes are provided.

  On the other hand, the spot characteristic measuring unit includes a spot creating light beam separating means (13) for separating a part of the light beam before entering the test / reference light beam separating means (15) as a spot creating light beam, and the spot. Spot image generating means (29) for forming the spot forming light beam separated by the generating light beam separating means (13) as a spot image, and a second photodetector (31a) provided on the image plane of the spot image ).

  More specifically, the light beam measuring apparatus 10A is arranged on an optical path extending to the right in the drawing from the light source unit 11, and includes a beam splitter 13 as a light beam separating unit and a semi-transmissive as a test / reference light beam separating unit. The reflecting plate 15, the light shielding plate 16, the reference light generating means 23, the first imaging lens 25, the first imaging camera 27, and the beam splitter 13 arranged below the beam splitter 13 in the figure are arranged above the figure. The second imaging lens 29 and the second imaging camera 31 are provided. The light beam measuring apparatus 10 includes a computer 33 that performs various analyzes based on image signals from the first and second imaging cameras 27 and 31, a display device 34 that displays analysis results and images by the computer 33, and a keyboard. And an input device 35 such as a mouse. The computer 33 includes first analysis means for analyzing the interference fringes and obtaining a wavefront measurement result of the light beam, and second analysis means for analyzing the spot image and obtaining a characteristic measurement result of the light beam spot of the light beam; Are provided as a program stored in a memory or the like, an arithmetic circuit for executing the program, or the like.

  In the present embodiment, the beam splitter 13, the first imaging lens 25, and the first imaging camera 27 constitute a first imaging unit, and the beam splitter 13, the second imaging lens 29, The second imaging camera 31 constitutes a second imaging unit.

  Further, in the light beam measuring apparatus 10A shown in FIG. 2, the same reference numerals are used for the same components as those of the wavefront measuring interferometer apparatus 10 shown in FIG. 1, and a detailed description thereof will be omitted to avoid duplication. Omitted and only the differences will be described in detail below.

  In the present embodiment, the light source unit 11 is configured in the same manner as that shown in FIG. 1, and is used by being incorporated in various devices as a laser light output device, like the wavefront measuring interferometer device 10. Yes, it is not a component of the light beam measuring apparatus 10A.

  The light shielding plate 16 is composed of an openable / closable shutter or the like, and blocks the optical path between the transflective plate 15 and the reference light generating means 23 when adjusting the optical system, and opens the optical path during measurement. It is configured as follows. The light shielding plate 16 is opened and closed by an electric motor 41, and the driving of the electric motor 41 is controlled by a computer 33 via a driver 43.

  Hereinafter, the operation at the time of measurement by the light beam measuring apparatus 10A will be described. The light beam emitted from the light source unit 11 to the right in the drawing is a light beam traveling toward the transflective plate 15 and a light beam traveling toward the second imaging lens 29 (on the separation surface 13a of the beam splitter 13). The light beam is separated into two light beams (spot light for creating a spot image). Of the two light beams, one of the light beams traveling toward the transflective plate 15 is reflected on the transflective surface 15a of the transflective plate 15 in the direction opposite to the incident direction, and the transflective light is reflected. The light is separated into a transmitted light beam (reference light beam forming light beam) that passes through the plate 15 and travels toward the reference light generation means 23. During the measurement, the light shielding plate 16 is open, and the transmitted light beam is incident on the converging lens 17 of the reference light generating unit 23 without being blocked by the light shielding plate 16.

  The transmitted light beam incident on the converging lens 17 is converged by the converging lens 17 and is incident on the reflection diffraction unit 19 disposed at the convergence point. A part of the transmitted light beam incident on the reflection diffraction unit 19 is converted into a spherical wave whose wavefront is shaped by the reflection diffraction unit 19, and reflected toward the convergence lens 17. The spherical wave is converted into a plane wave by the converging lens 17 and is emitted toward the transflective plate 15 as a reference light beam.

  The reference light beam passes through the semi-transmissive reflecting plate 15 and is combined with the test light beam reflected by the semi-transmissive reflecting surface 15a, whereby interference light is obtained. The interference light is incident on the first imaging lens 25 via the beam splitter 13, and the first detection surface 27 a in the first imaging camera 27 is transmitted via the first imaging lens 25. The interference fringes are imaged. The image information of the captured interference fringes is input to the computer 33, and the wavefront measurement of the light beam is performed based on the image information.

  On the other hand, of the two light beams separated by the beam splitter 13, the light beam emitted toward the second imaging lens 29 passes through the second imaging lens 29 and the second imaging camera. A light beam spot image is formed on the second detection surface 31a by being condensed on a second detection surface 31a (for example, a solid-state imaging device such as a CCD or a CMOS). The second imaging camera 31 is configured to capture the formed spot image and output the image information to the computer 33. Based on the image information of the spot image input to the computer 33, various characteristics such as intensity distribution, half width, cross-sectional shape and luminance dispersion of the light beam spot are measured.

  The adjustment of the optical system in the light beam measuring apparatus 10A is first performed in a state where the light path between the transflective plate 15 and the reference light generating means 23 is blocked by the light shielding plate 16. In this state, a light beam is emitted from the light source unit 11, adjusted for each optical member arranged on the optical path reaching the second imaging camera 31 via the beam splitter 13, and from the light source unit 11. Each beam reaches the semi-transmissive reflection surface 15a via the beam splitter 13, is reflected by the semi-transmissive reflection surface 15a, and is disposed on the optical path reaching the first imaging camera 27 via the beam splitter 13 again. Adjustment of the optical member is performed. After this adjustment, the light shielding plate 16 is opened, and the reference light generating means 23 is adjusted.

  As described above, according to the light beam measuring apparatus 10A according to the first embodiment, the wavefront measurement of the light beam emitted from the light source unit 11 and the characteristic measurement of the light beam spot can be performed simultaneously. Further, since the Fizeau type optical system arrangement is adopted, the configuration is simple and compact, and the optical system can be easily adjusted.

  In the embodiment shown in FIG. 2, the transflective plate 15, the light shielding plate 16 and the reference light generating means 23 are arranged on the right side of the beam splitter 13 in the drawing, and the second imaging lens is on the upper side of the beam splitter 13 in the drawing. 29 and the second imaging camera 31 are arranged, but the arrangement positions thereof are exchanged, that is, the second imaging lens 29 and the second imaging camera 31 are arranged on the right side of the beam splitter 13, and the beam You may make it arrange | position the transflective plate 15, the light-shielding plate 16, and the reference light production | generation means 23 above the splitter 13. FIG.

  In the mode shown in FIG. 2, the interference light returning from the transflective reflector 15 side is guided to the first imaging lens 25 via the beam splitter 13. Another beam splitter is disposed between the reflecting plate 15 and the interference light returning from the semi-transmissive reflecting plate 15 side is guided to the first imaging lens 25 through the other beam splitter. May be.

  Further, in the embodiment shown in FIG. 2, when adjusting the optical system, in order to prevent the light beam from returning to the semi-transmissive reflector 15 from the reference light generator 23, the semi-transmissive reflector 15 and the reference light generator are used. Is provided with a light shielding plate 16 that interrupts the optical path to the optical path 23. Instead of providing such a light shielding plate, the reflection diffractive portion can be moved to a position off the optical path (including tilting). The light beam may not be returned from the reference light generating means 23 to the transflective plate 15 by moving the reflection diffraction portion 19 to a position off the optical path. As a mode of moving the reflection diffraction unit 19 to a position off the optical axis, there are a mode of moving the entire reference light generation unit 23 out of the optical path, a mode of moving only the reflection diffraction unit 19 out of the optical path, etc. When the reflection diffractive portion 19 is changed to the one shown in FIG. 6 (details will be described later), the reflection diffractive portions 19A to 19D are easily moved out of the optical path by rotating the substrate 21A. be able to.

<Light Beam Measuring Device (Second Embodiment)>
Next, a second embodiment of the light beam measuring apparatus according to the present invention will be described. FIG. 3 is a schematic configuration diagram of a light beam measuring apparatus 10B according to the second embodiment of the present invention. In the light beam measurement apparatus 10B shown in FIG. 3, the same reference numerals are used for the same components as those in the light beam measurement apparatus 10A shown in FIG. 2, and detailed descriptions thereof are omitted to avoid duplication. Hereinafter, only different points will be described in detail.

  The light beam measuring apparatus 10B shown in FIG. 3 includes the following constituent elements in addition to the constituent elements of the light beam measuring apparatus 10A shown in FIG. That is, as shown in FIG. 3, the light beam measuring device 10B is disposed on the optical path between the light source unit 11 and the beam splitter 13 when measuring the light intensity of the light beam emitted from the light source unit 11. A reflection mirror 51 that guides the light beam by reflecting it at a right angle downward in the figure in a parallel light beam state and a power meter 52 that measures the light intensity of the light beam from the reflection mirror 51 are provided. The power meter 52 includes a light detection surface 52a. The power meter 52 is configured to measure the intensity of a light beam incident on the light detection surface 52a in a substantially parallel light flux state and output the measurement information to the computer 33. ing. A beam expander may be provided on the optical path between the reflection mirror 51 and the power meter 52 so that the diameter of the parallel light beam incident on the power meter 52 may be changed as necessary. The reflection mirror 51 is disposed on the optical path only when measuring the light intensity of the light beam, and is normally used when measuring the wavefront of the light beam and measuring the characteristics of the light beam spot. It is configured to be evacuated from the road.

  In addition, the light beam measuring apparatus 10B includes a beam splitter 53 that guides a part of the light beam emitted from the light source unit 11 by reflecting the light beam downward at right angles in the figure between the light source unit 11 and the beam splitter 13; An imaging lens 54 for alignment disposed on the optical path of the light beam guided by the beam splitter 53 and an imaging camera 55 for alignment are also provided. The imaging lens 54 condenses the incident light beam on a detection surface 55a (for example, a solid-state image sensor such as a CCD or a CMOS) in the imaging camera 55, and the light beam is formed on the detection surface 55a. The spot image is formed. The imaging camera 55 is configured to capture the formed spot image and output the image information to the computer 33.

  The spot image captured by the imaging camera 55 is used for aligning the inclination of the light source unit 11 and the like. That is, the alignment adjustment of the light source unit 11 is performed based on the position information of the spot image input to the computer 33 on the detection surface 55a.

  Further, the light beam measuring apparatus 10B reflects a part of the light beam reflected from the transflective surface 15a between the beam splitter 13 and the transflective plate 15 at a right angle downward in the figure. And an alignment imaging lens 57 disposed on the optical path of the light beam guided by the beam splitter 56, and an alignment imaging camera 58. The imaging lens 57 condenses the incident light beam on a detection surface 58a (for example, a solid-state imaging device such as a CCD or a CMOS) in the imaging camera 58, and the light beam is formed on the detection surface 58a. The spot image is formed. The imaging camera 58 is configured to capture the formed spot image and output the image information to the computer 33.

  The spot image captured by the imaging camera 58 is used for aligning the inclination and the like of the transflective plate 15 and the reference light generator 23. That is, the alignment adjustment of the transflective plate 15 and the reference light generating means 23 is performed based on the position information of the spot image input to the computer 33 on the detection surface 55a.

  This alignment adjustment is first performed in a state where the light path between the transflective plate 15 and the reference light generating means 23 is blocked by the light shielding plate 16. In this state, alignment adjustment of the transflective plate 15 is performed, and after this adjustment, the light shielding plate 16 is opened, and alignment adjustment of the reference light generating means 23 is performed.

  The light beam measuring apparatus 10B also includes an alignment light source 61 that outputs an alignment light beam at the upper position of the beam splitter 13 in the figure, and a divergent light beam that is output from the alignment light source 61 to the right in the figure. When aligning the collimating lens 62 to be collimated with the parallel plate-shaped optical element described later, the collimating lens 62 is disposed on the optical path between the beam splitter 13 and the second imaging lens 29, and from the collimating lens 62. A reflection mirror 63 is provided that reflects the parallel light beam at a right angle downward in the figure and guides it to the beam splitter 13.

  The alignment light source 61 is configured so that the parallel plate-like optical element (for example, a cover glass or various filters, not shown) is disposed between the light source unit 11 and the beam splitter 53. It is used when adjusting the alignment of the inclination of the element. That is, when the alignment of the optical element is adjusted, the reflection mirror 63 is disposed on the optical path between the beam splitter 13 and the second imaging lens 29, and the alignment output from the alignment light source 61 is performed. The light beam for use is guided to the beam splitter 13 through the collimator lens 62 and the reflection mirror 63. A part of the alignment parallel light beam guided to the beam splitter 13 is guided to the optical element at a part of the separation surface 13a of the beam splitter 13 at a right angle to the left in the drawing.

  A part of this parallel light beam for alignment led to the optical element is reflected by the optical element, and a part of the reflected light beam is reflected by the beam splitter 53 at a right angle downward in the figure, and further the above-mentioned connection is made. The image lens 54 collects the light on the detection surface 55a in the imaging camera 55 and forms a spot image on the detection surface 55a. The spot image is picked up by the image pickup camera 55, and the image information is output to the computer 33. Based on the positional information on the detection surface 55a of the spot image input to the computer 33, alignment adjustment of the optical element is performed.

  The above-described reflection mirror 51 and power meter 52 measure the light transmittance of a predetermined condenser lens (for example, an optical pickup lens) and the light intensity of a light beam output through the condenser lens. It can also be used. FIG. 4 shows a measurement unit 70 used for measuring the transmittance of such an optical pickup lens.

  A measurement unit 70 shown in FIG. 4 includes a first lens 71 for an optical pickup to be measured, and light that is incident on the first lens 71 from the left in the drawing and is converged and diverged by the first lens 71. A second lens (having a known light transmittance) for collimating the beam is held at a predetermined distance from each other. The measurement unit 70 uses the light transmittance measurement method proposed by the applicant of the present application (see Japanese Patent Application Nos. 2004-379449 and 2004-379450) to transmit light of the first lens 71. When measuring the rate and the light intensity of the light beam output through the first lens 71, the light beam is disposed on the optical path between the light source unit 11 and the reflection mirror 51 shown in FIG.

  That is, the maximum light amount data of the light beam output from the light source unit 11 through the measurement unit 70 in a state where the measurement unit 70 is disposed on the optical path between the light source unit 11 and the reflection mirror 51 shown in FIG. Is calculated by the power meter 52, and this is compared with the light amount data of the light beam from the light source unit 11 measured in a state where the measurement unit 70 is not arranged, thereby calculating the light transmittance of the first lens 71 and The light intensity of the light beam output through only the first lens 71 can be obtained (for details, see the above specifications).

  Further, even when the light transmittance of the second lens is not known, a third lens is added to the lens to be measured in addition to the first and second lenses 71 and 72, and three different lenses are obtained by these three lenses. A pair is formed, the maximum light quantity data is sequentially obtained for these lens pairs, and the light transmittance of each lens to be measured is obtained by calculating a ternary simultaneous equation with the light transmittance of each lens as an unknown. Also good.

  When measuring the light transmittance or the like of the first lens 71, a reference light source for measurement capable of outputting a light beam having higher wavefront accuracy instead of the light source unit for test 11 shown in FIG. (Not shown) is preferably used.

  As described above, according to the light beam measuring apparatus 10B according to the second embodiment, it is possible to simultaneously perform the wavefront measurement of the light beam emitted from the light source unit 11 and the characteristic measurement of the light beam spot. It is also possible to measure the light intensity of the light beam emitted from the light source unit 11 and measure the light transmittance of the optical pickup lens. In addition, since the alignment optical system is provided, the entire system can be adjusted more easily.

  In the embodiment shown in FIG. 3, a part of the light beam before entering the transflective plate 15 (test / reference light beam separating means) is separated as a spot forming light beam by the beam splitter 13 (light beam separating means). However, a part of the test light beam after being separated by the transflective reflector 15 (test / reference light beam separating means) is separated by the beam splitter 56 as a spot forming light beam, Another beam splitter may be installed between the transflective plate 15 and the reference light generating means 23 so that a part of the reference beam generating beam before wavefront shaping is separated as a spot generating beam. Good.

<Light beam measurement method>
Hereinafter, a light beam measuring method according to an embodiment of the present invention will be described. This light beam measurement method is performed using the above-described light beam measurement apparatus 10A or 10B.

  That is, first, a light beam to be measured (a light beam emitted from the light source unit 11) is subjected to two light beams of a test light beam for wavefront measurement and a reference light beam forming light beam on the transflective surface 15a. The reference beam generation light beam 23 is subjected to wavefront shaping and converted into a reference light beam by the reference light generation unit 23, and then the test light beam and the reference light beam are caused to interfere with each other to obtain wavefront information of the test light beam. Is formed on the first detection surface 27a in the first imaging camera 27 (interference fringe generation procedure).

  On the other hand, a part of the light beam before being separated into two light fluxes, that is, a test light flux and a reference light flux, is separated as a spot light flux by the beam splitter 13, and the separated spot light flux is separated, A spot image is formed on the first detection surface 31a in the second imaging camera 31 (spot image generation procedure).

  Then, in the computer 33, the interference fringes are analyzed to obtain a light beam wavefront measurement result (first analysis procedure), and the spot image is analyzed to obtain a light beam spot characteristic measurement result of the light beam (second analysis procedure). Analysis procedure).

<Change of mode>
The optical beam measurement device 10A shown in FIG. 2 and the optical beam measurement device 10B shown in FIG. 3 have a Fizeau type arrangement of the optical system for obtaining interference fringes, but instead of the Fizeau type, a Michelson type It is also possible to adopt the following optical system arrangement. In such a case, the characteristics of the arrangement employing the Fizeau-type optical system as described above, that is, the characteristic that the configuration of the optical system is simple and compact and the adjustment of the optical system is easy, but the interference fringes are reduced. Since the optical path lengths of the test light beam and the reference light beam to be obtained can be set to be substantially equal to each other, measurement can be performed even when the light beam to be subjected to wavefront measurement is a low-coherence light beam. There is an advantage that it becomes possible.

  Also, by providing the reflection mirror 51 and the power meter 52 of the light beam measuring apparatus 10B shown in FIG. 3 in the wavefront measuring interferometer apparatus 10 shown in FIG. It is also possible to configure so that light intensity measurement or the like can be performed. In that case, the reflection mirror 51 may be disposed on the optical path between the light source unit 11 and the beam splitter 13 so that it can be taken in and out. Furthermore, by using the measurement unit 70 shown in FIG. 4, the wavefront measurement interferometer apparatus 10 shown in FIG. 1 can be configured to measure the light transmittance and the like of the optical pickup lens.

  It is also possible to variously change the aspect of the reflection diffraction section 19 that is commonly used in the wavefront measurement interferometer device 10 shown in FIG. 1 and the light beam measurement devices 10A and 10B shown in FIGS. is there.

  Hereinafter, modifications of the aspect of the reflection diffraction unit 19 will be described with reference to FIGS. The reflection diffraction portion 19E shown in FIG. 5 is made of, for example, a metal film formed by vapor deposition or the like on a substrate 21B formed in a curved surface shape such as a spherical surface. In this embodiment, since the substrate 21B is formed in a curved shape, the convergent light beam incident on the substrate 21B from the converging lens (not shown) arranged on the left side in the drawing is directed toward the converging lens. The reflection can be suppressed, and the generation of noise light is thereby suppressed.

  The reflection diffraction portions 19A to 19D shown in FIG. 6 are made of, for example, a metal film formed by vapor deposition or the like on a substrate 21A formed in a disc shape, and the sizes of the reflection diffraction portions 19A to 19D are different from each other. It is configured. The substrate 21 </ b> A is configured to be rotatable along the paper surface about the rotation shaft 44. In this embodiment, one of the reflection diffraction units 19A to 19D can be selectively arranged at the convergence point of the convergent lens according to the NA of the convergent lens arranged on the front side of the sheet. It has become.

  The reflection diffraction portion 19F shown in FIG. 7 includes a pinhole 45 formed smaller than the diffraction limit of the incident convergent light beam, and a reflection surface 47 arranged in the immediate vicinity of the back surface side of the pinhole 45. In this embodiment, even if the relative positions of the pinhole 45 and the reflecting surface 47 are shifted along the reflecting surface 47, the function of wavefront shaping does not change. Therefore, when the portion of the reflective surface 47 facing the pinhole 45 is damaged and its function is impaired, the function can be easily repaired by relatively shifting the pinhole 45 and the reflective surface 47. There is an advantage.

The figure which shows one Embodiment of the interferometer apparatus for wavefront measurement which concerns on this invention The figure which shows 1st Embodiment of the light beam measuring apparatus which concerns on this invention. The figure which shows 2nd Embodiment of the light beam measuring apparatus which concerns on this invention. The figure which shows the measurement unit for light transmittance measurement The figure which shows the modification of a reflection diffraction part The figure which shows the other modification of a reflection diffraction part The figure which shows the other modification of a reflection diffraction part Schematic configuration diagram of a conventional wavefront measurement interferometer device

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Interferometer apparatus for wavefront measurement 10A, 10B Light beam measuring apparatus 11, 101 Light source part 11a Light source main body 11b Beam optical system 13 Beam splitter (Flux separation means, Spot creation light flux separation means)
53, 56, 102, 107 Beam splitter 13a Separation surface 15 Transflective plate (test / reference beam separation means)
15a transflective surface 17, 103, 109 converging lens 16 light shielding plate 19, 19A-19F reflection diffractive parts 21, 21A, 21B substrate 23 reference light generating means 25 imaging lens (first imaging lens, interference fringe generating means) )
27 Imaging camera (first imaging camera)
27a Detection surface (first detection surface, first photodetector)
29 Second imaging lens 31 Second imaging camera 31a Second detection surface (second photodetector)
33 Computer 34 Display Device 35 Input Device 36 Fringe Scan Adapter 37 Holder 38 Piezoelectric Element 39, 43 Driver 41 Electric Motor 44 Rotating Shaft 45, 104 Pinhole 47 Reflecting Surface 51, 63 Reflecting Mirror 52 Power Meter 52a Photodetecting Surface 54, 57 Imaging lens for alignment 55, 58 Imaging camera for alignment 55a, 58a Detection surface 61 Light source for alignment 62, 105, 110 Collimator lens 71 First lens 72 Second lens 106, 108 Mirror 111 Imaging lens 112 Imaging camera

Claims (17)

A transflective surface that reflects part of the light beam to be measured as a test light beam in the direction opposite to the incident direction;
The transmitted light beam having a converging lens for converging the transmitted light beam transmitted through the semi-transmissive reflective surface and a minute reflection diffraction portion disposed at a convergence point of the convergent lens, and incident from the semi-transmissive reflective surface A reference light generation means for converting a part of the reference light beam into a wavefront-shaped reference light beam and emitting the reference light beam toward the transflective surface,
And an imaging unit that guides interference light formed by combining the reference light beam and the test light beam to a detection surface and forms interference fringes on the detection surface,
A wavefront measurement interferometer device configured to perform wavefront measurement of the light beam based on the interference fringes formed on the detection surface.   Optical path length adjusting means is provided for adjusting an optical distance between the semi-transmissive reflecting surface and the reference light generating means by moving at least one of the semi-transmissive reflecting surface and the reference light generating means in the optical axis direction. The wavefront measuring interferometer device according to claim 1.   The reference light generating means is configured to hold a plurality of reflection diffractive parts having different sizes and to selectively arrange one of the plurality of reflection diffractive parts at the convergence point. The wavefront measuring interferometer device according to claim 1 or 2.   The peripheral region of the reflection diffraction part is configured to have a shape capable of suppressing reflection of the transmitted light beam incident on the peripheral region through the converging lens toward the converging lens. The interferometer device for wavefront measurement according to any one of claims 1 to 3. A light beam measuring apparatus capable of measuring both a wavefront measurement of a light beam to be measured and a characteristic measurement of a spot of the light beam,
A test / reference beam separating means for separating the light beam into two light beams, a test light beam for wavefront measurement and a reference light beam, and a reference light beam by shaping the wave surface of the reference light beam and converting it to a reference light beam A reference light generating means that interferes with the test light beam and the reference light beam to form an interference fringe image that carries the wavefront information of the test light beam, and an imaging surface of the interference fringe A first light detector provided, and a wavefront measuring unit comprising:
The light beam before entering the test / reference beam separation unit, the test beam after being separated by the test / reference beam separation unit, or the reference beam creation beam before wavefront shaping. A spot creating light beam separating means for separating a part of the spot creating light beam as a spot creating light beam, a spot image generating means for forming the spot creating light beam separated by the spot creating light beam separating means as a spot image, and the spot image A second photo detector provided on the imaging plane of
A light beam measuring apparatus comprising:   The test / reference light beam separating means reflects a part of the incident light beam as the test light beam in a direction opposite to the incident direction, and transmits the remaining part of the light beam as the reference light beam. 6. The light beam measuring apparatus according to claim 5, wherein the light beam measuring apparatus is a transflective surface.   The reference light generating means includes a converging lens for converging the reference light beam forming light beam, and a minute reflection diffracting portion arranged at a convergence point of the converging lens, and the test / reference light beam separating means A part of the incident light beam for generating the reference light beam is wavefront shaped and converted into the reference light beam, and the reference light beam is emitted toward the test / reference light beam separating means. Item 7. The light beam measuring apparatus according to Item 5 or 6. A light beam separating means for separating a light beam to be measured into two light beams,
A transflective surface that reflects a part of one of the two light beams separated by the light beam separating means as a test light beam in a direction opposite to the incident direction;
The transmitted light beam having a converging lens for converging the transmitted light beam transmitted through the semi-transmissive reflective surface and a minute reflection diffraction portion disposed at a convergence point of the convergent lens, and incident from the semi-transmissive reflective surface A reference light generation means for converting a part of the reference light beam into a wavefront-shaped reference light beam and emitting the reference light beam toward the transflective surface,
A first imaging unit that guides interference light formed by combining the reference light beam and the test light beam to a first detection surface and forms interference fringes on the first detection surface;
And a second imaging unit that forms a spot image of the other of the two light beams separated by the light beam separating unit on a second detection surface,
The wavefront of the light beam is measured based on the interference fringes formed on the first detection surface, and the characteristics of the light beam spot are measured based on the spot image formed on the second detection surface. A light beam measuring device configured as described above.   9. The light beam measuring apparatus according to claim 8, wherein the interference light is configured to be guided to the first detection surface through the light beam separating unit.   Optical path length adjusting means is provided for adjusting an optical distance between the semi-transmissive reflecting surface and the reference light generating means by moving at least one of the semi-transmissive reflecting surface and the reference light generating means in the optical axis direction. 10. The light beam measuring apparatus according to claim 8 or 9, wherein:   The reference light generating means is configured to hold a plurality of reflection diffractive parts having different sizes and to selectively arrange one of the plurality of reflection diffractive parts at the convergence point. The light beam measuring apparatus according to claim 8, wherein   The light beam measuring apparatus according to claim 8, further comprising a light blocking unit that blocks an optical path between the transflective surface and the reference light generating unit.   The light beam measuring apparatus according to claim 8, wherein the reflection diffraction unit is configured to be moved to a position out of the optical path.   The peripheral region of the reflection diffraction part is configured to have a shape capable of suppressing reflection of the transmitted light beam incident on the peripheral region through the converging lens toward the converging lens. The light beam measuring apparatus of any one of Claims 8-13.   The light beam measuring apparatus according to claim 5, further comprising a power meter that measures light intensity of the light beam.   A first analysis unit that analyzes the interference fringes to obtain a wavefront measurement result of the light beam; a second analysis unit that analyzes the spot image to obtain a light beam spot characteristic measurement result of the light beam; The light beam measuring device according to claim 5, comprising: A light beam measurement method capable of measuring both a wavefront measurement of a light beam to be measured and a characteristic measurement of a spot of the light beam,
The light beam is separated into two light beams, a test light beam for wavefront measurement and a reference light beam, and the reference light beam is shaped into a reference beam and converted into a reference light beam. An interference fringe generation procedure for forming an interference fringe that forms an interference fringe carrying the wavefront information of the test light flux by interfering with the reference light flux;
The light beam before being separated into two light beams, that is, the test light beam and the reference light beam, or the test light beam after being separated, or the reference light beam light beam before being wavefront shaped. A spot image generation procedure in which a part is separated as a spot image creation light beam, and the spot image creation light beam is formed as a spot image;
A first analysis procedure for analyzing the interference fringes and obtaining a wavefront measurement result of the light beam;
A second analysis procedure for analyzing the spot image and obtaining a characteristic measurement result of the light beam spot of the light beam;
A method of measuring a light beam, comprising:

Images