JP2009168519A - Inspection apparatus for optical element splitting light, and inspection method for optical element splitting light - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inspection apparatus and an inspection method for an optical element splitting light for efficiently measuring with improved accuracy wave front aberration occurred in two laser beams that pass through and reflect against the optical element splitting light, such as a beam splitter. <P>SOLUTION: The inspection apparatus includes a laser beam irradiating means irradiating a laser beam; a wave front aberration measuring means receiving the laser beam to measure wave front aberration of the laser beam; an optical means introducing the laser beam irradiated from the laser beam irradiating means into an optical element that is to be inspected and splits a light and introducing the laser beams passing through and reflecting against the optical element into the wave front aberration measuring means; a laser beam selecting means provided in the optical element which blocks the laser beams or changes optical paths of the laser beams, such that the laser beam selected out of the laser beams passing through and reflecting against the optical element enters into the wave front aberration measuring means. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical element inspection apparatus that divides light, such as a beam splitter, and an optical element inspection method that divides light.

  Conventionally, for example, a beam splitter is used in many apparatuses as an optical element that splits (branches) incident light into two beams of transmission and reflection. In the beam splitter, the beam branch plane is arranged at an angle of 45 ° with respect to the incident beam, the transmitted light is parallel to the incident beam, and the reflected light is perpendicular to the incident beam. There are several types of beam splitters, but if two right angle prisms are bonded together, the joint surface is coated with a dielectric multilayer film or metal thin film, and the thickness depends on the coating thickness. And the amount of light of the two reflected beams can be adjusted.

As an inspection of such a beam splitter, which is an optical element, for example, as shown in Patent Document 1, the deflection angle, transmittance, and reflectance of two beams of transmission and reflection are measured. Yes.
JP 63-153442 A

  However, in the conventional optical element inspection method such as a beam splitter, even a beam splitter that is inferior due to an inspection result that is less than an allowable value is transmitted due to surface distortion on the beam branching surface or uneven coating thickness. There is a problem that wavefront aberration may occur in the two beams of reflection and reflection, and the wavefront aberration may be an unacceptable amount depending on an apparatus in which the beam splitter is used.

  The present invention has been made in view of such circumstances, and accurately and efficiently measures wavefront aberration generated in two laser beams transmitted and reflected by an optical element that divides light such as a beam splitter. An object of the present invention is to provide an optical element inspection apparatus that divides light and an optical element inspection method that divides light.

  An inspection device for an optical element that divides light according to claim 1 comprises: laser light emitting means for emitting laser light; wavefront aberration measuring means for measuring the wavefront aberration of the laser light upon incidence of the laser light; and laser light emission. An optical system that guides laser light emitted from the means to an optical element that divides the light that is the inspection object, and guides the laser light transmitted and reflected by the optical element that divides the light that is the inspection object to the wavefront aberration measurement means Of the laser beam transmitted and reflected by the optical element that divides the light that is the object to be inspected, and the selected laser beam is incident on the wavefront aberration measuring unit. Alternatively, a laser beam selecting means for changing the optical path of the laser beam is provided.

  The optical element inspection apparatus for splitting light according to claim 2 is characterized in that the laser light selecting means comprises at least two shutters and shutter opening / closing control means for controlling opening / closing of the shutters.

  According to a third aspect of the present invention, there is provided an inspection device for an optical element that divides light, wherein the laser light selecting means is composed of a mirror and a mirror movement control means for controlling the movement of the mirror.

  5. The inspection device for an optical element for splitting light according to claim 4, wherein the polarization state variable means for changing the polarization state of the laser light emitted from the laser light emitting means from linearly polarized light to circularly polarized light is inspected from the laser light emitting means. It is characterized in that it can be arranged on the optical path of the laser beam up to the optical element that divides the light that is an object.

  The optical element inspection apparatus for splitting light according to claim 5 is configured such that the beam diameter of the laser light transmitted from and reflected by the optical element for splitting the laser light emitted from the laser light emitting means and the light to be inspected is determined. A light beam diameter varying means for changing is provided.

  The inspection device for an optical element that divides light according to claim 6 is a light that is an object to be inspected in a state where there is no optical element that divides the light that is the object to be inspected from the laser light emitting means. A wavefront aberration correcting optical path means for guiding to the wavefront aberration measuring means in the same optical path as when there is an optical element for dividing the optical element, and a wavefront aberration measuring means for guiding the laser beam to the wavefront aberration measuring means by the wavefront aberration correcting optical path means. The wavefront aberration correcting means corrects the result of measuring the wavefront aberration of the laser light transmitted and reflected by the optical element that divides the light to be inspected by the wavefront aberration measuring means based on the wavefront aberration of the laser light measured It is characterized by comprising.

  The optical element inspection apparatus for splitting light according to claim 7 is characterized in that the wavefront aberration measuring means is a Shack-Hartmann sensor.

  The method for inspecting an optical element that divides light according to claim 8 leads the emitted laser light to an optical element that divides the light that is the object to be inspected, and is transmitted by the optical element that divides the light that is the object to be inspected. One of the reflected laser beams is selected by blocking the laser beam or changing the optical path of the laser beam, and the wavefront aberration of the selected laser beam is measured.

  The method for inspecting an optical element that divides the light according to claim 9 divides the light that is the inspection object without the optical element that divides the light that is the inspection object with respect to the wavefront aberration of the emitted laser light. The optical path of the laser beam was measured in the same way as when there was an optical element, and based on the measured wavefront aberration, the wavefront aberration of the laser beam transmitted and reflected by the optical element that divides the light that is the inspection object was measured. It is characterized by correcting the result.

  According to the first and eighth aspects of the invention, when measuring the wavefront aberration of the laser light transmitted and reflected by the optical element that divides the light, either the transmitted or reflected laser light is selected to reduce the wavefront aberration. Since the measurement is performed, the wavefront aberration generated in the transmitted and reflected two laser beams can be efficiently measured.

  According to the second aspect of the present invention, the means for selecting one of the transmitted and reflected laser light includes at least two shutters and a means for controlling the opening and closing of the shutter, so that the transmitted and reflected laser light can be selected. Of these, it is possible to efficiently select a laser beam for measuring the wavefront aberration.

  According to the third aspect of the present invention, the wavefront of the transmitted and reflected laser light is configured by configuring the means for selecting either the transmitted or reflected laser light from the mirror and the means for controlling the movement of the mirror. Laser light for measuring aberration can be selected efficiently.

  According to the invention of claim 4, since the means for changing the polarization state of the laser light from linearly polarized light to circularly polarized light is provided before the laser light enters the object to be inspected, the optical element for dividing the light is a polarizing beam splitter. Even so, by changing the polarization state of the laser light from linearly polarized light to circularly polarized light, the intensity of the transmitted laser light and the intensity of the reflected laser light can be made approximately equal, and the wavefront aberration generated in the laser light can be accurately measured. can do.

  According to the invention of claim 5, since the means for changing the beam diameter of the emitted laser beam and the laser beam transmitted and reflected by the object to be inspected is provided, the laser is adjusted in accordance with the size of the optical element for dividing the light. The light beam diameter of the laser light incident on the wavefront aberration measuring means can be made constant after changing the light beam diameter of the light, and the wavefront aberration generated in the laser light can be accurately measured.

  According to the sixth and ninth aspects of the present invention, since the means for correcting the wavefront aberration generated by other than the inspected object from the measured wavefront aberration is provided, the light is transmitted and reflected by the optical element that divides the light. The wavefront aberration generated in the two laser beams can be accurately measured.

  According to the seventh aspect of the present invention, by using the Shack-Hartmann sensor as the means for measuring the wavefront aberration, a light interference system is not required, so that the configuration of the apparatus can be simplified.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. The inspection device for an optical element that divides light in the embodiment of the present invention is an apparatus for inspecting an optical element such as a beam splitter.

  FIG. 1 is a block diagram showing a first embodiment of a beam splitter inspection apparatus to which the present invention is applied. FIG. 2 is an explanatory diagram illustrating a method for obtaining a laser beam wavefront for correction in the beam splitter inspection apparatus according to the first embodiment. The beam splitter inspection apparatus 1 is an inspection apparatus that inspects a beam splitter Ob that is an optical element that divides light. The beam splitter inspection apparatus 1 includes a laser light source 10, a collimating lens 12, a quarter wavelength plate 14, a half mirror 16, beam expanders 18a and 18b, shutters 20 and 24, mirrors 22 and 26, a Shack-Hartmann sensor 30, and a controller 40. , An image generation device 42, an input device 44, a monitor device 46, and the like.

  The laser light source 10 is composed of a semiconductor laser, and the controller 40 controls the emission and stop of the emission of the laser beam, and emits a laser beam having a polarization direction of linearly polarized light at a predetermined wavelength. The polarization direction of the linearly polarized light is 45 ° from the fast axis and slow axis of the quarter-wave plate 14 described later. The collimator lens 12 converts the laser light (diverged light) emitted from the laser light source 10 into parallel light. The quarter-wave plate 14 is set on the optical path of the laser beam when a beam splitter Ob that is an inspection object to be described later is a polarization beam splitter. Since the laser light is incident in a state where the polarization direction of the linearly polarized light is 45 ° from the fast axis and the slow axis of the quarter-wave plate 14, the laser light becomes circularly polarized after being transmitted.

  The half mirror (a beam splitter having a ratio of transmitted light to reflected light of 1: 1) transmits approximately half of the incident laser light and reflects approximately half in the direction perpendicular to the incident direction. The laser light used for the inspection is half of the laser light transmitted from the laser light incident from the laser light source 10 side, and half of the laser light incident from the side of the beam splitter Ob that is an inspection object to be described later. Laser light. The laser beam reflected by the laser beam incident from the laser light source 10 side and the laser beam transmitted by the laser beam incident from the beam splitter Ob side are left as they are and are not used for inspection.

  The beam expanders 18a and 18b change the light beam diameter of the laser light incident from the laser light source 10 side to a light beam diameter that matches the size of a beam splitter Ob that is an inspection object to be described later, and enter the laser beam incident from the beam splitter Ob side. The light beam diameter is changed to the original beam diameter. By exchanging the two lenses of the beam expanders 18a and 18b, the beam diameter of the laser beam can be changed variously.

  A beam splitter Ob serving as an object to be inspected receives the laser light whose beam diameter has been changed by the beam expanders 18a and 18b, reflects a predetermined ratio of the laser light, and transmits a predetermined ratio of the laser light. When the beam splitter Ob of the object to be inspected is a polarization beam splitter, approximately half of the laser light is reflected and transmitted because circularly polarized light is incident. Then, the reflected laser light is reflected by the mirror 22 via the shutter 20, returns to the original optical path, and enters the beam splitter Ob of the inspection object. The transmitted laser light is reflected by the mirror 26 via the shutter 24, returns to the original optical path, and enters the beam splitter Ob of the inspection object.

  The laser light reflected by the mirrors 22 and 26 and incident on the beam splitting Ob also reflects a predetermined ratio of the laser light and transmits a predetermined ratio of the laser light. The laser beam used for the inspection is a laser beam directed toward the half mirror 16, and the laser beam transmitted by the laser beam incident from the mirror 22 side and the laser beam reflected by the laser beam incident from the mirror 26 side are left as they are. And not used for inspection. That is, laser light used for inspection is transmitted through the half mirror 16, reflected by the beam splitter Ob, reflected by the mirror 22, reflected by the beam splitter Ob, and reflected by the half mirror 16 (hereinafter referred to as a reflected laser of the beam splitter Ob). 2) of laser light transmitted through the half mirror 16, transmitted through the beam splitter Ob, reflected by the mirror 26, transmitted through the beam splitter Ob, and reflected by the half mirror 16 (hereinafter referred to as transmitted laser light through the beam splitter Ob). One.

  When the beam splitter Ob of the object to be inspected is a polarization beam splitter, most of the laser light reflected when reflected from the laser light source 10 and reflected by the mirror 22 is reflected and incident from the laser light source 10 side. Most of the laser light transmitted through and reflected by the mirror 26 is transmitted. Opening and closing of the shutters 20 and 24 is controlled by the controller 40, and by closing one of the shutters, either the reflected laser light of the beam splitter Ob or the transmitted laser light of the beam splitter Ob will be described later. It can enter into the man sensor 30 and can test | inspect.

  The inspection of the laser beam is performed by making the laser beam reflected by the half mirror 16 enter the Shack-Hullman sensor 30 and measuring the wavefront. The Shack-Hullman sensor 30 includes an ND filter 32, a microlens array 34, and a CCD image sensor 36. The incident laser light has an appropriate amount of light by the ND filter 32 and is condensed on the CCD image pickup device 36 by the microlens array 34. As a result, a plurality of point images are formed on the CCD image pickup device 36, and the CCD image pickup device 36 outputs video signals corresponding to the plurality of point images to the image generation device 42. Based on the video signal, the wavefront of the laser light is calculated based on the video signal, and stereoscopic image data for displaying as a stereoscopic image is generated, and the evaluation value representing the wavefront aberration of the laser light is calculated and monitored. Output to device 46. The monitor device 46 displays the state of the wavefront of the laser beam as a stereoscopic image based on the stereoscopic image data, and displays the evaluation value.

  When calculating the wavefront of the laser light, the image generating device 42 corrects the wavefront aberration by correcting the wavefront of the laser light that does not pass through or reflect the beam splitter Ob of the inspection object in the same optical path stored in advance. The wavefront of the laser beam is obtained when the laser beam without light is transmitted or reflected only through the beam splitter Ob of the inspection object. In other words, the wavefront aberration of the laser light itself emitted from the laser light source 10 and the optical elements other than the beam splitter Ob on the optical path from when the laser light is emitted from the laser light source 10 to when it enters the Shack-Hartmann sensor 30 Is obtained and stored, and the wavefront aberration generated only by the beam splitter Ob is obtained by subtracting the wavefront aberration from the wavefront aberration when the beam splitter Ob is added. Do.

  In the beam splitter inspection apparatus 1 configured as described above, an operator first measures a correction laser light wavefront stored in the image generation apparatus 42. The operator instructs the correction laser light wavefront measurement used for the wavefront measurement of the transmitted laser light from the input device 44 without setting the beam splitter Ob of the inspection object. Thus, the controller 40 emits laser light from the laser light source 10 and instructs the image generation device 42 to calculate and store the wavefront of the laser light.

  As shown in FIG. 2A, the laser light at this time is incident on the Shack-Hartmann sensor 30 along the same optical path as that used when inspecting the transmitted laser light of the beam splitter Ob. Therefore, the wavefront of the laser light calculated by the image generating device 42 is the wavefront of the laser light when it does not pass through the inspection target beam splitter Ob in the same optical path as when the inspection target beam splitter Ob is present. The image generation device 42 stores the calculation result of the laser beam wavefront in the image generation device 42 as a correction laser beam wavefront when measuring the wavefront of the transmitted laser beam of the beam splitter Ob.

  Next, the operator sets the mirror 29 that has been confirmed by inspection that no wavefront aberration is generated at the position where the beam splitter Ob of the inspection object is set, and uses the input device 44 to measure the wavefront of the reflected laser beam. Directs the correction laser light wavefront measurement to be used. As a result, the controller 40 emits laser light from the laser light source 10, and the image generating device 42 calculates the wavefront of the laser light. As shown in FIG. 2B, the laser light at this time is incident on the Shack-Hartmann sensor 30 along the same optical path as that when the reflected laser light of the beam splitter Ob is inspected. Therefore, the wavefront of the laser light calculated by the image generation device 42 is the wavefront of the laser light when it is not reflected by the inspection target beam splitter Ob in the same optical path as when the inspection target beam splitter Ob is present. The image generation device 42 stores the calculation result of the laser beam wavefront in the image generation device 42 as a correction laser beam wavefront when measuring the wavefront of the reflected laser beam of the beam splitter Ob. Since the correction laser light wavefront does not change in a short time, the correction laser light wavefront may be measured periodically to update the existing stored data.

  When the measurement of the correction laser light wavefront is completed or it is determined that the stored correction laser light wavefront is not necessary, the operator sets the beam splitter Ob of the object to be inspected and inputs it from the input device 44. An instruction for inspection and an instruction on whether to inspect reflected laser light or transmitted laser light of the beam splitter Ob are given. Thus, the controller 40 closes the shutter 24 when the inspection of the reflected laser light is designated, and closes the shutter 20 when the inspection of the transmitted laser light is designated, and emits the laser light from the laser light source 10 to generate an image. The apparatus 42 is instructed to calculate the wavefront of the laser light after designating the correction laser light wavefront to be used for correction.

  The image generation device 42 calculates the wavefront of the laser beam using the video signal input from the CCD image sensor 36, and then designates the specified correction laser among the two correction laser beam wavefronts stored. Correction is performed using the optical wavefront, stereoscopic image data to be displayed as a stereoscopic image is generated, and an evaluation value representing the wavefront aberration of the laser light is calculated and output to the monitor device 46. The monitor device 46 displays the state of the wavefront of the laser beam as a stereoscopic image based on the stereoscopic image data, and displays the evaluation value of the wavefront aberration of the laser beam, so that the operator looks at the displayed stereoscopic image and the evaluation value. The pass / fail of the beam splitter Ob to be inspected is determined. Alternatively, the allowable range of the evaluation value of the wavefront aberration may be set and stored in the image generation device 42, and the image generation device 42 may determine whether the evaluation is acceptable or not along with the evaluation value calculation.

  Various modifications can be made to the embodiment 1 described above. In the first embodiment, the wavefront of the laser beam is measured by the Shack-Hartmann sensor 30, but an interferometer may be used instead of the Shack-Hartmann sensor 30. FIG. 3 is a block diagram showing a second embodiment of a beam splitter inspection apparatus to which the present invention is applied, and is a block diagram of the beam splitter inspection apparatus using an interferometer. The difference of the second embodiment from the first embodiment is that a mirror 28 and a CCD image sensor 38 are provided except for the Shack-Hartmann sensor 30.

  The laser light incident from the laser light source 10 and reflected by the half mirror 16 is reflected by the mirror 28, passes through the half mirror 16, and enters the CCD image element 38. At this time, the laser beam enters the half mirror 16 from the beam splitter Ob side of the object to be inspected, is reflected by the half mirror 16, and interferes with the laser light incident on the CCD image sensor 38. As a result, interference fringes are formed on the CCD image sensor 38, and the CCD image sensor 38 outputs a video signal having an intensity based on the density of the interference fringes. The image generation device 42 creates image data of interference fringes based on the input video signal and outputs the image data to the monitor device 46. The monitor device 46 displays the interference fringes. Further, the image generation device 42 generates and outputs stereoscopic image data of the wavefront of the laser light from the interference fringe image data, and the state of the wavefront of the laser light is displayed as a stereoscopic image on the monitor device 46 as in the first embodiment. indicate.

  In this configuration, the laser light source 10, the collimating lens 12, the quarter wavelength plate 14, the half mirror 16, and the mirror 28 are used so that no wavefront aberration occurs (the wavefront aberration is within an allowable limit). In this way, the interference fringes resulting from the interference are due to the wavefront aberration of the laser light incident on the half mirror 16 from the beam splitter Ob side. In addition, by using a wavefront aberration correction mirror instead of the mirror 28, the wavefront aberration generated in the laser light source 10, the collimating lens 12, and the half mirror 16 is corrected, and the laser beam that passes through the half mirror 16 and travels toward the CCD image pickup device 38. Wavefront aberration may not be generated in the light.

  Also in this case, the image generating device 42 creates stereoscopic image data and calculates and outputs an evaluation value of the wavefront aberration, and the monitor device 46 displays the stereoscopic image and the evaluation value of the wavefront aberration. The person can judge the pass / fail of the beam splitter Ob to be inspected by viewing the displayed stereoscopic image and the evaluation value. Also in the present embodiment, the correction laser light wavefront is obtained by the same method as in the first embodiment and stored in the image generating device 42, and the interference fringe image data and the three-dimensional image of the laser light wavefront are stored. Try to correct the data.

  In the form of the first embodiment, the wavefronts of the reflected laser beam and the transmitted laser beam of the beam splitter Ob are separately measured by opening and closing the two shutters 20 and 24. However, instead of the two shutters 20 and 24, mirrors are used. The wave fronts of the reflected laser beam and the transmitted laser beam of the beam splitter Ob may be separately measured by the movement. FIG. 4 is a block diagram showing a third embodiment of a beam splitter inspection apparatus to which the present invention is applied. The beam splitter inspection apparatus measures the wavefront of reflected laser light or transmitted laser light separately by moving a mirror. FIG.

  The laser light emitted from the laser light source 10 and converted into parallel light by the collimators 12 and transmitted through the beam splitter Ob of the inspection object is incident on the Shack-Hartmann sensor 30 as it is, and the laser light reflected by the beam splitter Ob of the inspection object is Reflected by the mirrors 50, 52, and 54 and then incident on the Shack-Hullman sensor 30.

  The mirror 54 is set in a drive mechanism that can move horizontally, and the drive mechanism moves the mirror 54 to two different positions in response to a command from the controller 40. When the mirror 54 is at the position indicated by the solid line in FIG. 4, the laser light transmitted through the beam splitter Ob of the object to be inspected enters the Shack-Hartmann sensor 30, and the laser light reflected by the beam splitter Ob is reflected in the mirror 54. Then, the light travels in a direction that does not enter the Shack-Hullman sensor 30.

  When the mirror 54 is at the position indicated by the dotted line in FIG. 4, the laser beam that has passed through the beam splitter Ob of the inspection object is blocked by the mirror 54, and the laser beam reflected by the beam splitter Ob of the inspection object is reflected. The light is reflected by the mirrors 50, 52 and 54 and enters the Shack-Hullman sensor 30. The controller 40 outputs a command to a drive mechanism that horizontally moves the mirror 54 based on designation of inspection of transmitted laser light or inspection of reflected laser light input from the input device 44 by the operator.

  In this case as well, the laser beam wavefront for correction is obtained and stored, and the wavefront of the laser beam is corrected. When the wavefront of the correction laser beam is obtained, the beam splitter Ob is eliminated and the mirror 54 is positioned not on the optical path of the laser beam as shown in FIG. At this time, the wavefront of the laser beam acquired by the image processing device 42 is used as a laser beam wavefront for correction when measuring the wavefront of the transmitted laser beam of the beam splitter Ob. Further, as shown in FIG. 5B, a mirror 56 that does not generate wavefront aberration is set at the position of the beam splitter Ob, and laser light is incident on the Shack-Hartmann sensor 30, and the laser light acquired by the image processing device 42 at this time Is the laser beam wavefront for correction when measuring the wavefront of the reflected laser beam of the beam splitter Ob. The data processing of the image processing device 42, the display style of the monitor device 46, and the instructions input by the operator from the input device 44 are all the same as in the first embodiment.

  In the third embodiment, when the beam diameter of the laser beam is changed by the beam expander, the beam diameter of the laser beam incident on the Shack-Hullman sensor 30 is not constant. It needs to be restored. Therefore, the third embodiment is desirably used when the beam splitters Ob to be inspected have substantially the same size.

  Also in the third embodiment, the wavefront of the laser beam may be measured by an interferometer instead of the Shack-Hullman sensor 30. FIG. 6 is a block diagram showing a fourth embodiment of a beam splitter inspection apparatus to which the present invention is applied. A beam splitter in which the Shack-Hartmann sensor 30 of the beam splitter inspection apparatus according to the third embodiment is replaced with an interferometer 60. It is a block diagram of an inspection apparatus.

  Various types of interferometers may be used, but a Mach-Zehnder type interferometer is used in this embodiment. The interferometer 60 includes half mirrors 61 and 69, mirrors 64 and 65, condenser lenses 62, 63, 66 and 68, a pinhole plate 67, and a CCD image sensor 70. Then, the light is guided to two different optical paths, overlapped and interfered again, and interference fringes generated by wavefront aberration of the incident laser light are measured.

  The laser beam reflected by the half mirror 61 changes its optical path in a right angle direction by the mirror 65, is condensed by the condenser lens 66, and is collected around the pinhole (4 to 20 μm) in the pinhole plate 67. Only the center of the image is transmitted through the pinhole. As a result, the wavefront aberration of the laser light is removed, and the light is again converted into parallel light by the condenser lens 68, then reflected by the half mirror 69 and incident on the CCD image pickup device 70 as reference light. The laser light that has passed through the half mirror 61 is reflected by the mirror 64 through a condenser lens 62 as a condenser lens and a condenser lens 63 as a relay lens, passes through the half mirror 69, and is measured by the CCD image sensor 70. Incident as light. Since the measured light is not removed from the wavefront aberration of the incident laser light, and the reference light is removed from the wavefront aberration of the incident laser light, the interference fringes resulting from the interference of the two laser lights are incident on the incident laser light. This is caused by the wavefront aberration.

  In the fourth embodiment, the configuration for calculating and displaying the interference fringes, the three-dimensional image of the wavefront of the laser beam and the evaluation value of the wavefront aberration from the video signal output from the CCD image pickup device 70 is the same as that of the second embodiment. The method for obtaining the laser light wavefront for the same is the same as in the third embodiment. As in the third embodiment, this embodiment is also preferably used when the beam splitters Ob to be inspected have substantially the same size.

  In the first embodiment, when the wavefronts of the reflected laser beam and the transmitted laser beam of the beam splitter Ob are separately inspected by opening and closing the two shutters 20 and 24, the reflected beam 2 is reflected twice by the beam splitter Ob of the object to be inspected. Although the configuration is such that the wavefront of the laser beam that has been transmitted once is inspected, the wavefront of the laser beam that has been reflected once and transmitted once may be inspected. FIG. 7 is a block diagram showing a fifth embodiment of the beam splitter inspection apparatus to which the present invention is applied. The wave fronts of the reflected laser beam and the transmitted laser beam of the beam splitter Ob are separately provided by opening and closing two shutters. When inspecting, the beam splitter inspection apparatus inspects the wavefront of the laser light reflected and transmitted once by the beam splitter Ob. In this embodiment, shutters 72 and 74 and a half mirror 76 are provided in place of the mirror 54 in the beam splitter inspection apparatus 3 of the third embodiment.

  Laser light emitted from the laser light source 10 and converted into parallel light by the collimator lens 12 and transmitted through the beam splitter Ob of the object to be inspected is transmitted through the half mirror 76 via the shutter 72 and is incident on the Shack-Hartmann sensor 30 as it is. The laser light reflected by the beam splitter Ob of the inspection object is reflected by the mirrors 50 and 52, reflected by the half mirror 76 via the shutter 74, and enters the Shack-Hartmann sensor 30. In this case, only the arrangement of the optical elements is different from that in the third embodiment, and the data processing of the image processing device 42, the display style of the monitor device 46, and the instructions input by the operator from the input device 44 are all the same as in the third embodiment. is there. When the wavefront of the correction laser beam is obtained, the wavefront is measured except for the beam splitter Ob of the inspection object, and the wavefront is set by setting a mirror 56 that does not generate wavefront aberration instead of the beam splitting Ob of the inspection object. The points to be measured are also the same as in the third embodiment.

  Also in this case, as in the fourth embodiment, the interferometer 60 can be used in place of the Shack-Hullman sensor 30. As in the third and fourth embodiments, the fifth embodiment is desirably used when the beam splitter Ob of the inspection object has substantially the same size.

  As described above, according to the beam splitter inspection devices 1 to 5 for inspecting the beam splitter, for example, according to the beam splitter inspection devices 1 to 5 for inspecting the beam splitter, the light is transmitted and reflected by the optical element for dividing the light. When measuring the wavefront aberration of the laser beam, either the transmitted or reflected laser beam is selected and the wavefront aberration is measured, so that the wavefront aberration generated in the two transmitted and reflected laser beams can be efficiently performed. Can be measured.

  Further, the means for selecting either the transmitted or reflected laser light is composed of at least two shutters and a means for controlling opening and closing of the shutter, thereby measuring the wavefront aberration of the transmitted and reflected laser light. Laser light can be selected efficiently.

  Further, by configuring the means for selecting either the transmitted or reflected laser light from the mirror and the means for controlling the movement of the mirror, the laser light for measuring the wavefront aberration of the transmitted and reflected laser light is selected. It can be selected efficiently.

  Furthermore, since means for changing the polarization state of the laser light from linearly polarized light to circularly polarized light is provided before the laser light enters the object to be inspected, even if the optical element that divides the light is a polarization beam splitter, the laser light By changing the polarization state from linearly polarized light to circularly polarized light, the intensity of the transmitted laser light and the intensity of the reflected laser light can be made substantially equal, and the wavefront aberration generated in the laser light can be accurately measured.

  Furthermore, by providing means for changing the beam diameter of the emitted laser beam and the laser beam transmitted and reflected by the object to be inspected, the beam diameter of the laser beam is changed according to the size of the optical element that divides the light. In addition, the diameter of the laser beam incident on the wavefront aberration measuring means can be made constant, and the wavefront aberration generated in the laser beam can be measured with high accuracy.

  Furthermore, by providing a means for correcting the wavefront aberration generated by something other than the inspection object from the measured wavefront aberration, the wavefront aberration generated in the two laser beams transmitted and reflected by the optical element that divides the light is accurate. It can be measured well.

  Furthermore, by using a Shack-Hartmann sensor as a means for measuring wavefront aberration, a system for interfering light is unnecessary, and the configuration of the apparatus can be simplified.

  As described above, according to the present invention, light that can accurately and efficiently measure wavefront aberration generated in two laser beams transmitted and reflected by an optical element that divides light, such as a beam splitter, is obtained. An inspection device for an optical element to be divided and an inspection method for an optical element for dividing light can be provided.

It is a block diagram which shows the 1st Example of the beam splitter test | inspection apparatus with which this invention is applied. It is explanatory drawing which shows the method of calculating | requiring the laser beam wave front for correction | amendment in the beam splitter test | inspection apparatus of Example 1. FIG. It is a block diagram which shows the 2nd Example of the beam splitter test | inspection apparatus with which this invention is applied. It is a block diagram which shows the 3rd Example of the beam splitter test | inspection apparatus with which this invention is applied. It is explanatory drawing which shows the method of calculating | requiring the laser beam wave front for correction | amendment in the beam splitter test | inspection apparatus of Example 3. FIG. It is a block diagram which shows the 4th Example of the beam splitter test | inspection apparatus with which this invention is applied. It is a block diagram which shows the 5th Example of the beam splitter test | inspection apparatus with which this invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1-5 ... Beam splitter inspection apparatus 10 ... Laser light source 12 ... Collimating lens 14 ... 1/4 wavelength plate 16 ... Half mirror 18a, 18b ... Beam expander 20 ··· Shutter 22 ··· Mirror 24 ··· Shutter 26 ··· Mirror 28 ··· Mirror 29 ··· Mirror 30 · · · Shack-Hartmann sensor 32 ··· ND Filter 34... Microlens array 36... CCD image sensor 38... CCD image sensor 40. · Monitor device 50 ··· Mirror 52 ··· Mirror 54 ··· Mirror 56 ··· Mirror 60 ··· Interferometer 61 ··· Half mirror 62 ··· Condenser lens 63 ... Optical lens 64 ··· Mirror 65 ··· Mirror 66 ··· Condenser lens 67 ··· Pinhole plate 68 ··· Condenser lens 69 ··· Half mirror 70 ··· CCD image sensor 72... Shutter 74... Shutter 76.

Claims (9)

Laser light emitting means for emitting laser light;
Wavefront aberration measuring means for measuring the wavefront aberration of the laser light upon incidence of the laser light;
The laser light emitted from the laser light emitting means is guided to an optical element that divides the light that is the inspection object, and the laser light transmitted and reflected by the optical element that divides the light that is the inspection object is the wavefront aberration. Optical system means leading to the measuring means;
Of the laser light transmitted and reflected by the optical element that divides the light that is the object to be inspected, provided in the optical system means, the selected laser light is cut off so as to enter the wavefront aberration measuring means. An inspection device for an optical element that divides light, comprising: a laser light selection unit that changes an optical path of the laser light.   2. The optical element inspection apparatus for splitting light according to claim 1, wherein the laser light selecting means comprises at least two shutters and shutter opening / closing control means for controlling opening / closing of the shutters.   2. The optical element inspection apparatus for splitting light according to claim 1, wherein the laser light selecting means comprises a mirror and mirror movement control means for controlling movement of the mirror.   Laser light from the laser light emitting means to the optical element that divides the light to be inspected from the laser light emitting means to change the polarization state of the laser light emitted from the laser light emitting means from linearly polarized light to circularly polarized light The optical element inspection apparatus for splitting light according to claim 1, wherein the optical element can be arranged on an optical path of the optical element.   And a light beam diameter varying means for changing a light beam diameter of the laser light transmitted and reflected by the optical element that divides the laser light emitted from the laser light emitting means and the light that is the inspection object. An inspection device for an optical element that divides the light according to claim 1. The laser light emitted from the laser light emitting means is in the same optical path as in the case where there is an optical element for splitting the light that is the inspection object without the optical element that splits the light that is the inspection object. Wavefront aberration correcting optical path means for guiding to the wavefront aberration measuring means;
Based on the wavefront aberration of the laser light measured by the wavefront aberration measuring means when the laser light is guided to the wavefront aberration measuring means by the wavefront aberration correcting optical path means, the wavefront aberration measuring means 6. A wavefront aberration correcting unit for correcting a result of measuring a wavefront aberration of laser light transmitted and reflected by an optical element that divides certain light. Inspection device for optical elements that divides light.   The optical element inspection apparatus for splitting light according to claim 1, wherein the wavefront aberration measuring means is a Shack-Hartmann sensor. The emitted laser light is guided to an optical element that divides the light that is the inspection object,
One of the laser beams transmitted and reflected by the optical element that divides the light to be inspected is selected by blocking the laser beam or changing the optical path of the laser beam,
A method for inspecting an optical element that divides light, wherein the wavefront aberration of the selected laser light is measured. The wavefront aberration of the emitted laser light is made the same as the optical path of the laser light when there is no optical element that divides the light that is the inspection object without the optical element that divides the light that is the inspection object. Measure and
9. The light according to claim 8, wherein based on the measured wavefront aberration, the result of measuring the wavefront aberration of the laser beam transmitted and reflected by the optical element that divides the light as the inspection object is corrected. Inspection method for optical elements.

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