JP4667965B2 - Light beam measuring device - Google Patents

Description

  The present invention relates to a light beam measuring apparatus that performs wavefront measurement of a light beam to be measured and various measurements at a focused spot of the light beam, and in particular, a light beam suitable for measuring a low coherence light beam. It relates to a measuring device.

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

  Further, as a device for measuring the wavefront of a light beam, an apparatus having an optical system arrangement of a Mach-Zehnder interferometer has been generally known so far, but in recent years, an optical system arrangement of a Fizeau interferometer has been provided. This has been proposed by the present applicant and has already been disclosed to the Patent Office (see Patent Document 2 below).

  In the Mach-Zehnder type wavefront measuring device, a part of the reference beam forming light beam separated from the test light beam is shaped by transmitting the pinhole, whereas in the Fizeau type wavefront measuring device, the reference light beam measuring device An optical element (hereinafter referred to as a “reflection diffractive section”) that reflects a part of a light beam for forming a light beam in the direction opposite to the incident direction to shape the wavefront is used. Such a reflection diffraction part is also referred to as a reflection type pinhole or the like, in which a minute reflection region is formed on a glass substrate, or in which a minute reflection region is formed at the tip of a needle-like member (Patent Document 3 below) For example) (see the following Patent Document 4).

JP 2004-45327 A Japanese Patent Application No. 2004-168965 Specification JP 2000-97612 A JP 58-60590 A

  The beam profiler and the wavefront measuring apparatus as described above are used, for example, for measuring the output light of the optical pickup device. Some of these optical pickup devices use a low-coherence semiconductor laser beam on which harmonics are superimposed as an irradiation beam. In order to perform the wavefront measurement of such a low-coherence light beam, It is necessary to make the optical path length of the test light beam and the optical path length of the reference light beam substantially coincide with each other.

  The Fizeau type wavefront measuring apparatus disclosed in the above-mentioned Patent Document 2 is set so that the optical path lengths of the test light beam and the reference light beam are different from each other, so that the light beam to be measured is a low coherence light beam. In some cases, it is difficult to perform wavefront measurements.

  On the other hand, since the Mach-Zehnder type wavefront measuring apparatus can substantially match the optical path lengths of the test light beam and the reference light beam, it can cope with the wavefront measurement of a light beam with low coherence. There is a problem that adjustment of the optical system is very difficult because the number of parts of the optical system is large and there are various adjustment points. In addition, there are problems such as being easily affected by vibration and difficult to install a phase shift mechanism.

  In the optical pickup device, two measurements, that is, a wavefront measurement and a spot characteristic measurement of irradiated laser light are sometimes performed in the manufacturing stage. Conventionally, these two measurements are performed using different measurement devices. It was done separately. Therefore, there is a problem that it takes a lot of time to perform two measurements.

  The present invention has been made in view of such circumstances, and can be used for wavefront measurement of a light beam with low coherence, and can easily adjust an optical system and install a phase shift mechanism. A first object is to provide a light beam measuring apparatus for measurement.

  It is a second object of the present invention to provide a light beam measuring apparatus that can cope with wavefront measurement of a light beam having low coherence and can also perform spot characteristic measurement of the light beam.

In order to achieve the first object, the light beam measuring apparatus of the present invention is configured as follows. That is, the light beam measuring apparatus according to the present invention includes a test / reference light beam separating means for separating a light beam to be measured into a test light beam and a reference light beam forming light beam, and a wavefront of the reference light beam forming light beam. Wavefront shaping means for shaping and converting to a reference light beam, multiplexing means for combining the test light beam and the reference light beam with each other to obtain interference light, and wavefront information of the light beam by the obtained interference light An interference fringe imaging / imaging means for imaging by imaging an interference fringe carrying
The wavefront shaping means includes a converging lens for converging the reference light beam forming light beam, and a minute reflection diffraction portion arranged at a convergence point of the converging lens. A reflection wavefront shaping unit configured to convert a part of the wavefront into the reference light beam, and to emit the reference light beam toward the test / reference light beam separating unit.
The test / reference light beam separating unit and the combining unit cause the test light beam separated from the reference light beam forming light beam to be incident on a reflecting surface, and the test light beam returning from the reflecting surface is the wavefront shaping unit. A beam separation / combination surface for combining with the reference beam from
When at least the light beam is a low-coherence light beam, a first optical path length returning from the light beam separation / combination surface to the light beam separation / combination surface through the reflection surface, and from the light beam separation / combination surface Optical path length adjusting means for making the second optical path lengths that return to the light beam separation / combining surface through the reflective wavefront shaping unit substantially coincide with each other ;
One of the light beam before entering the light beam separation / combination surface, the test light beam after being separated by the light beam separation / combination surface, or the reference light beam preparation light beam before wavefront shaping. A spot creating light beam separating means for separating a portion as a spot creating light beam, a spot image imaging / imaging means for imaging a spot image of the light beam by the spot creating light beam,
First analysis means for analyzing the interference fringes and obtaining a wavefront measurement result of the light beam;
And a second analysis means for obtaining a point image intensity distribution as a result of spot characteristic measurement of the light beam by analyzing the spot image .

  Further, the image data indicating the intensity of the parallel wavefront of the light beam is subjected to a Fourier transform operation to obtain the point image intensity distribution calculating means for obtaining the point image intensity distribution of the light beam and the second analyzing means. It is preferable to include a point image intensity distribution and comparison analysis means for comparing and analyzing the point image intensity distribution obtained by the point image intensity distribution calculation means.

  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.

  According to the light beam measuring apparatus of the present invention, the apparatus includes a wavefront shaping unit configured by a reflective wavefront shaping unit, a test / reference beam separation unit configured by a beam separation / combining surface, and a multiplexing unit. Therefore, it is possible to adopt a Michelson type optical system arrangement, so that the optical system can be easily adjusted and the phase shift mechanism can be installed as compared with the conventional Mach-Zehnder type.

  In addition, since the optical path length adjustment means is provided, the optical path lengths of the test light beam and the reference light beam can be made substantially equal to each other, so that it can cope with the wavefront measurement of a light beam with low coherence. Can do.

  Further, according to the aspect including the spot creating light beam separating means and the spot image forming / imaging means, two measurements, that is, the wavefront measurement of the light beam and the spot characteristic measurement of the light beam can be performed. Is possible.

<First Embodiment>
Hereinafter, embodiments of a light beam measuring apparatus according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of the light beam measuring apparatus according to the first embodiment of the present invention, and FIG. 2 is a schematic configuration diagram of the analysis apparatus shown in FIG.

  A light beam measuring apparatus 1A shown in FIG. 1 measures both the wavefront measurement and spot characteristic measurement of a light beam output from the optical pickup module 50. First, the optical pickup module 50 will be described.

  An optical pickup module 50 shown in FIG. 1 includes a semiconductor laser 51 that outputs a low-coherence light beam on which harmonics are superimposed, and a collimator lens 52 that collimates the light beam output from the semiconductor laser 51 as divergent light. And a condensing lens 53 that condenses the light beam collimated by the collimator lens 52 so that a low-coherence light beam to be measured is emitted toward the right in the figure. It is configured. The optical pickup module 50 is used by being mounted on an optical pickup device (not shown), and is not a component of the light beam measuring device 1A.

  Next, the light beam measuring apparatus 1A will be described. A light beam measuring apparatus 1A shown in FIG. 1 includes a measurement analysis system that is configured around an optical system portion constituted by various optical members arranged on an optical axis indicated by a one-dot chain line in the drawing, and an analysis apparatus 31. The optical system part is further divided into a collimator lens 11 for guiding the light beam from the optical pickup module 50 into the optical system, and a wavefront measuring unit for measuring the wavefront of the guided light beam. 10A and a spot characteristic measuring unit 10B for measuring the spot characteristic of the guided light beam.

  First, the part of the optical system will be described. The wavefront measuring unit 10A includes a test / reference beam separation means (15) for separating the guided light beam into a test beam for measuring the wavefront and a reference beam generation beam, and the reference beam generation beam. Wavefront shaping means (20) for wavefront shaping and converting to a reference light beam, multiplexing means (15) for combining the test light beam and the reference light beam to obtain interference light, and the obtained interference light And interference fringe imaging / imaging means (18, 19) for imaging by imaging the interference fringes carrying the wavefront information of the light beam.

  More specifically, the wavefront shaping means includes a reflective wavefront shaping unit 20. The reflection type wavefront shaping unit 20 includes a converging lens 21 for converging a reference light beam forming light beam, and a minute reflection diffraction portion 22 disposed at a convergence point of the converging lens 21, and an incident reference is made. A part of the light beam for forming the light beam is wavefront shaped and converted into a reference light beam, and the reference light beam is emitted toward the test / reference light beam separating means.

  The reflection diffraction part 22 is made of a metal film such as gold, aluminum, or chromium formed on the substrate 23 by vapor deposition or the like, and the size thereof is larger than the diffraction limit of a light beam incident as a convergent light beam. It is small. A part of the reference light beam forming light beam incident as the convergent light beam is reflected as an ideal spherical wave wave-shaped. The surface of the substrate 23 that faces the converging lens 21 is subjected to an antireflection coating process corresponding to the wavelength of the light beam so that the reference beam forming light beam that is not wavefront shaped does not return to the converging lens 21. It has become.

  The test / reference beam separation means and the multiplexing means comprise a beam separation / multiplexing surface 15. The light beam separation / combination surface 15 is formed by a cube prism type beam splitter, a plate-shaped half mirror, or the like, and the test light beam separated from the reference light beam forming light beam is reflected on the reflection surface 17a of the reflection plate 17 (the incident light beam). And the test light beam returning from the reflection surface 17a is combined with the reference light beam from the reflection type wavefront shaping unit 20 (which is smoothed with high precision so that the wavefront can be maintained). ing.

  The reflecting plate 17 is provided with a uniaxial stage that holds the reflecting plate 17 so as to be movable in the optical axis direction (vertical direction in the figure), and a fringe scan adapter having a piezoelectric element or the like ( (All are not shown). These are the first optical path length returning from the light beam separation / combination surface 15 to the light beam separation / combination surface 15 through the reflection surface 17a, and the light beam separation / combination surface from the light beam separation / combination surface 15 through the reflective wavefront shaping unit 20. The optical path length adjusting means for making the second optical path length returning to 15 substantially coincide with each other is configured. The fringe scan adapter constitutes a phase shift mechanism. For example, when performing sub-fringe measurement using the phase shift method, the reflector 17 is finely moved in the optical axis direction by driving the piezoelectric element. It is configured.

  The interference fringe imaging / imaging means comprises an imaging lens 18 and a first imaging camera 19. The imaging lens 18 forms an image of interference fringes obtained from the interference light from the beam separation / combining surface 15 on the imaging surface 19a of the first imaging camera 19 (for example, an imaging surface such as a CCD or CMOS). The first imaging camera 19 is configured to image the interference fringes imaged on the imaging surface 19a and output the image signal.

  A light shielding means 16 is disposed on the optical path between the light beam separation / combining surface 15 and the reflective wavefront shaping unit 20. The light shielding means 16 comprises an openable / closable shutter or the like, and interrupts the optical path between the light beam separation / combining surface 15 and the reflective wavefront shaping unit 20 when calculating the point image intensity distribution of the light beam by calculation, which will be described later. However, the optical path is configured to be opened at the time of wavefront measurement.

  On the other hand, the spot characteristic measuring unit 10B includes a spot creating light beam separating means (12) for separating a part of the light beam before entering the light beam separating / combining surface 15 as a spot creating light beam, and a separated spot. And a spot image imaging / imaging means (13, 14) for imaging a spot image of a light beam by forming a light beam.

  More specifically, the spot creating light beam separating means comprises a light beam separating surface 12 formed by a cube prism type beam splitter, a plate-like half mirror, or the like. An image lens 13 and a second imaging camera 14 are included. In other words, the light beam separation surface 12 is configured to separate a part of the light beam emitted from the collimator lens 11 as a light beam for spot creation and guide it to the imaging lens 13. The spot image generated from the light beam for imaging is formed on the imaging surface 14a of the second imaging camera 14 (consisting of an imaging surface such as a CCD or CMOS). The second imaging camera 14 is configured to capture a spot image formed on the imaging surface 14a and output the image signal.

  Next, the part of the measurement analysis system will be described. The measurement analysis system includes an analysis device 31 that performs various analyzes based on image signals from the first and second imaging cameras 19 and 14, a display device 32 that displays analysis results and images by the analysis device 31, and An input device 33 including a keyboard and a mouse is provided.

  The analysis device 31 is configured by a computer or the like, and generates image data of interference fringes and image data of spot images based on image signals from the first and second imaging cameras 19 and 14, as shown in FIG. The image generation unit 34, the fringe analysis unit 35 as a first analysis unit that analyzes the interference fringe image data and obtains the wavefront measurement result of the light beam, and the shape of the light beam spot by analyzing the image data of the spot image And a spot image analysis unit 36 as second analysis means for obtaining spot characteristic measurement results such as point image intensity distribution and barycentric coordinates.

  The analysis device 31 includes a point image intensity distribution calculation unit 37 for calculating a point image intensity distribution of the light beam by calculation, and the two point image intensity distribution calculation units 37 and the spot image analysis unit 36 respectively. A comparison analysis unit 38 for comparing and analyzing the point image intensity distribution results with each other is provided. Each of the units 34 to 38 is specifically configured by a processing program stored in a memory or the like, an arithmetic circuit that executes the processing program, or the like.

  The point image intensity distribution calculation unit 37 receives light from the first imaging camera 19 when the light shielding unit 16 shown in FIG. 1 blocks the optical path between the light beam separation / combining surface 15 and the reflective wavefront shaping unit 20. A point image intensity distribution of the light beam is obtained by performing a Fourier transform operation on the image data indicating the intensity distribution of the parallel wavefront of the light beam generated in the image generation unit 34 based on the image signal. As described above, as a technique for obtaining the point image intensity distribution from the intensity distribution of the parallel wavefront of the light beam, for example, those described in the following documents (1) and (2) are known.

(1) Warren J. Smith: Optical Engineering, SPIE Press, McGraw-Hill 3rd Edition
(2) Max Born & Emil Wolf: Principle of Optics, Pergamon Press 6th Edition
As described above, in the light beam measuring apparatus 1A, the spot image analysis is performed on the point image intensity distribution of the light beam based on two methods, that is, the spot image of the light beam obtained by the spot characteristic measuring unit 10B and the image generating unit 34. Based on the method of obtaining the point image intensity distribution in the unit 36 and the intensity distribution of the parallel wavefronts of the light beams obtained by the wavefront measuring unit 10A and the image generating unit 34, the point image intensity distribution calculating unit 37 obtains the point image intensity distribution. It can be determined by each method. Since these two types of point image intensity distributions are obtained by one light beam measuring apparatus 1A, it is also possible to easily correlate each other (using two different measuring apparatuses, two types of point images). Even if an image intensity distribution is obtained, it is extremely difficult to correlate them). Therefore, the comparison analysis result obtained by the comparison analysis unit 38 is used for determining the accuracy of the wavefront measurement result and the spot characteristic measurement result obtained by the light beam measurement apparatus 1A, and the aberration of the light beam measurement apparatus 1A. It can be used to obtain a system error such as.

Hereinafter, the operation at the time of measurement of the above-described light beam measuring apparatus 1A will be described.
As shown in FIG. 1, a low-coherence light beam emitted from the optical pickup module 50 to the right in the drawing is converted into a parallel beam by the collimator lens 11 and then the right beam in the drawing on the beam separation surface 12. Are split into a light beam for wavefront measurement that goes in the direction and a light beam for creating a beam spot that goes downward in the figure.

  The separated light beam for creating a beam spot is condensed on the imaging surface 14a in the second imaging camera 14 through the imaging lens 13, and forms a spot image of the light beam on the imaging surface 14a. The formed spot image is captured by the second imaging camera 14, and the image signal is output to the analysis device 31. Based on the output image signal, image data of the spot image is generated in the image generation unit 34 of the analysis device 31, and the image data of the spot image is analyzed in the spot image analysis unit 36, and the point image intensity of the light beam spot is calculated. Various spot characteristic measurement results such as distribution, half-value width, cross-sectional shape and luminance dispersion can be obtained.

  On the other hand, a wavefront measuring light beam directed from the light beam separation surface 12 to the right in the figure is incident on the light beam separation / combining surface 15 and is reflected on the light beam separation / combination surface 15 upwardly in the figure. The light beam separating / combining surface 15 is separated into a reference light beam forming light beam that passes through the reflection wavefront shaping unit 20 and passes through the light shielding means 16 in an open state to the converging lens 21. Incident.

  The reference light beam forming light beam incident on the converging lens 21 is converged by the converging lens 21 and is incident on the reflection diffraction portion 22 arranged at the convergence point. A part of the reference light beam forming light beam incident on the reflection diffraction unit 22 is converted into a spherical wave whose wavefront is shaped by the reflection diffraction unit 22 and reflected toward the convergent lens 21. The spherical wave is converted into a plane wave by the converging lens 21 and is emitted toward the light beam separation / combining surface 15 as a reference light beam. Further, a part of the reference light beam is reflected downward in the drawing by the light beam separation / combining surface 15.

  On the other hand, the test light beam reflected upward from the light beam separation / combination surface 15 is reflected in the reverse direction on the reflection surface 17a of the reflecting plate 17 and returns to the light beam separation / combination surface 15, and part of the light beam separation. / The light passes through the multiplexing surface 15 and is emitted downward in the figure.

  Interference light is obtained by combining this test light beam with the reference light beam reflected by the light beam separation / combination surface 15. The interference light is incident on the imaging surface 19a in the first imaging camera 19 through the imaging lens 18, and forms an interference fringe image carrying the wavefront information of the light beam on the imaging surface 19a. The formed interference fringe image is captured by the first imaging camera 19, and the image signal is output to the analysis device 31. Based on the output image signal, image data of the interference fringe image is generated in the image generation unit 34 of the analysis device 31, and the image data of the interference fringe image is analyzed in the fringe analysis unit 35, and the wavefront measurement result of the light beam Is obtained.

  As described above, according to the light beam measuring apparatus 1A, the wavefront measuring unit 10A and the spot characteristic measuring unit 10B are provided, and the wavefront measuring unit 10A includes the reflective wavefront shaping unit 20, the light beam separation / combining surface 15, Since the Michelson type optical system arrangement having the reflecting plate 17 and the optical path length adjusting means is adopted, two measurements, that is, a wavefront measurement of a light beam with low coherence and a spot characteristic measurement of the light beam are performed. In addition, it is possible to easily adjust the optical system and install a phase shift mechanism as compared with the conventional Mach-Zehnder type.

<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 1B according to the second embodiment of the present invention. In the light beam measurement apparatus 1B shown in FIG. 3, the same reference numerals are used for the same components as those in the light beam measurement apparatus 1A shown in FIG. 1, and detailed descriptions thereof are omitted to avoid duplication. Hereinafter, only different points will be described in detail.

  The light beam measuring apparatus 1B shown in FIG. 3 measures the wavefront of the light beam output from the optical pickup module 50. The light beam measuring apparatus 1A shown in FIG. Is different. Further, since the spot characteristic measuring unit is not provided, the light shielding means 16 shown in FIG. 1, the spot image analyzing unit 36, the point image intensity distribution calculating unit 37, the comparative analyzing unit 38, etc. shown in FIG. 2 are omitted. .

The wavefront measuring unit 10A ′ shown in FIG. 3 has a Michelson-type optical system arrangement that includes a reflective wavefront shaping unit 20, a light beam separation / combining surface 15, and a reflecting plate 17, and is also reflective. The point that the plate 17 has an optical path length adjusting means including a uniaxial stage and a fringe scan adapter is the same as in the first embodiment.
Therefore, according to this light beam measuring apparatus 1B, it is possible to measure the wavefront of a low-coherence light beam, and it is easier to adjust the optical system and install a phase shift mechanism than the conventional Mach-Zehnder type. It is possible to do it.

<Change of mode>
As mentioned above, although embodiment of this invention was described in detail, this invention is not limited to this embodiment, A mode can be variously changed.

  For example, in the above-described embodiment, since it is assumed that the wavelength of the light beam to be measured does not change, the reflection type wavefront shaping unit 20 is only one type, but there are a plurality of light beams to be measured, In order to be able to cope with the case where these wavelengths are different from each other, a plurality of types of reflective wavefront shaping units corresponding to each wavelength are provided, and when the wavelength of the light beam to be measured changes, they are switched to each other. May be used.

  In the embodiment shown in FIG. 1, a part of the light beam before entering the light beam separation / combining surface 15 (test / reference light beam separation means) is spotted by the light beam separation surface 12 (spot creation light beam separation means). Although the light beam is separated as a preparation light beam, another light beam separation surface is provided between the light beam separation / combining surface 15 and the reflection plate 17, and the test light beam after being separated by the light beam separation / combining surface 15 is used. Is separated as a spot-forming light beam, or another light beam separation surface is installed between the light beam separation / combining surface 15 and the wavefront shaping unit 20, and the reference light beam before being wavefront shaped. A part of the creation light beam may be separated as a spot creation light beam.

  Further, in the above-described aspect, since the light beam output from the optical pickup module 50 is a measurement object, unlike a normal interferometer device, the light source device is not included as a component, but a highly accurate wavefront A reference light source device capable of outputting a reference beam having When such a reference light source device is provided, the reference beam from the reference light source device is output through the test lens to be measured, and its wavefront measurement is performed, whereby the refractive index of the test lens is obtained. It is also possible to measure the distribution and the like.

  Further, as the reflection diffraction section 22 used in the wavefront shaping unit 20, various forms disclosed in the above-mentioned Patent Document 2 can be used.

1 is a schematic configuration diagram of a light beam measuring apparatus according to a first embodiment of the present invention. Schematic configuration diagram of the analysis apparatus shown in FIG. Schematic configuration diagram of a light beam measuring apparatus according to a second embodiment of the present invention

Explanation of symbols

1A Light Beam Measuring Device (First Embodiment)
1B Light Beam Measuring Device (Second Embodiment)
10A, 10A 'Wavefront measuring unit 10B Spot characteristic measuring unit 11, 52 Collimator lens 12 Light beam separation surface (light beam separating means for spot creation)
13, 18 Imaging lens 14 Second imaging camera 14a, 19a Imaging surface 15 Beam separation / combining surface (test / reference beam separation means)
DESCRIPTION OF SYMBOLS 16 Light-shielding means 17 Reflector 17a Reflective surface 20 Reflective wavefront shaping unit 21 Converging lens 22 Reflection diffraction part 23 Substrate 31 Analyzing device 32 Display device 33 Input device 34 Image generation unit 35 Stripe analysis unit (first analyzing means)
36 Spot image analysis unit (second analysis means)
37 Point Image Intensity Distribution Calculation Unit 38 Comparison Analysis Unit 50 Optical Pickup Module 51 Semiconductor Laser 53 Condensing Lens

Claims (2)

A test / reference beam separating unit that separates a light beam to be measured into a test beam and a reference beam generation beam; and a wavefront shaping unit that wave-shapes the reference beam generation beam into a reference beam. , A means for combining the test light beam and the reference light beam to obtain interference light, and imaging the interference fringes carrying the wavefront information of the light beam with the obtained interference light A light beam measuring device comprising: interference fringe imaging / imaging means;
The wavefront shaping means includes a converging lens for converging the reference light beam forming light beam, and a minute reflection diffraction portion arranged at a convergence point of the converging lens. A reflection wavefront shaping unit configured to convert a part of the wavefront into the reference light beam, and to emit the reference light beam toward the test / reference light beam separating unit.
The test / reference light beam separating unit and the combining unit cause the test light beam separated from the reference light beam forming light beam to be incident on a reflecting surface, and the test light beam returning from the reflecting surface is the wavefront shaping unit. A beam separation / combination surface for combining with the reference beam from
When at least the light beam is a low-coherence light beam, a first optical path length returning from the light beam separation / combination surface to the light beam separation / combination surface through the reflection surface, and from the light beam separation / combination surface Optical path length adjusting means for making the second optical path lengths that return to the light beam separation / combining surface through the reflective wavefront shaping unit substantially coincide with each other ;
One of the light beam before entering the light beam separation / combination surface, the test light beam after being separated by the light beam separation / combination surface, or the reference light beam preparation light beam before wavefront shaping. A spot creating light beam separating means for separating a portion as a spot creating light beam, a spot image imaging / imaging means for imaging a spot image of the light beam by the spot creating light beam,
First analysis means for analyzing the interference fringes and obtaining a wavefront measurement result of the light beam;
Analyzing the spot image, thereby obtaining a point image intensity distribution as a spot characteristic measurement result of the light beam;
Light beam measurement apparatus comprising: a.   Point image intensity distribution calculating means for obtaining a point image intensity distribution of the light beam by performing Fourier transform operation on image data indicating the intensity of the parallel wavefront of the light beam;
  Comparative analysis means for comparing and analyzing the point image intensity distribution obtained by the second analysis means and the point image intensity distribution obtained by the point image intensity distribution calculation means;
The light beam measuring apparatus according to claim 1, further comprising:

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