JP4986148B2 - Optical element molding die, molding die processing method, optical element, optical device, optical scanning device, image display device, and optical pickup device - Google Patents

Description

The present invention relates to a molding die for molding an optical element such as a diffractive optical element having a fine stepped pattern on the surface of the diffraction surface, a method for processing the molding die, and an optical molded with the molding die. The present invention relates to an element, an optical device using the optical element, an optical device, an optical scanning device, an image display device, and an optical pickup device.
In addition, not only diffractive optical elements but also the surface to be measured changes discontinuously as optical elements, so it can be used for those that require accurate measurement line positioning with micron accuracy. For example, coordinate estimation by interpolation is possible. This is difficult and requires a submicron shape accuracy such as an optical surface.

Conventionally, various proposals such as an optical element such as a diffractive optical element, a processing method for molding the optical element, a molding die, a manufacturing method of an optical element, a manufacturing apparatus, and the like have been made.
For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2003-251552) discloses a processing method suitable for processing a free-form surface having no rotational symmetry, an optical element and a mold manufacturing method using the method, an optical element, and the optical element In order to provide a processing method and the like that can obtain a surface shape with extremely small processing error even if the target surface shape is a free-form surface with no symmetry, In a processing method for forming a desired curved surface shape in a desired region, a marking step for forming an alignment mark on the same surface as the surface having the desired region of the workpiece, and the desired mark on the basis of the alignment mark A processing method characterized by forming the surface shape in a region "is disclosed. Further, as a summary of the solution means, “the grinding process (steps 1 and 2) and the polishing process (step 4) for processing the processing area of the quartz block that is the workpiece so as to approach the desired free-form surface shape, and the above processes A correction step (step 5) for performing correction processing on the processing region processed in (steps 1, 2, 4), and a marking step (step 3) for processing the alignment mark in the region excluding the processing region before this correction step. In the correction step (step 5), the shape of the processing region is measured with reference to the alignment mark (step 6), and correction processing is performed based on the measurement result (step 8). " It is described.

  Patent Document 2 (Japanese Patent Laid-Open No. 2000-56114) relates to a manufacturing method and a manufacturing apparatus for a diffractive optical element used in an optical system such as a semiconductor exposure apparatus, a camera, a telescope, and a microscope. In order to manufacture a highly rigid and highly accurate diffractive optical element by adhering other members, the “diffractive grating that is deformed by its own weight and / or the pressure and / or pressure of the holding member alone is used as another member. A method of manufacturing a diffractive optical element characterized by having a step of contacting at one contact point and a step of joining both of them by expanding the contact surface from the contact point to the whole is disclosed. Further, as a summary of the means for solving the problem, “a diffractive optical element is placed on the chuck 12 and air is discharged from the exhaust port 17 and fixed. The jig 11 is rotated by a predetermined angle, the mark position is measured by the mark scope 18, and diffraction The center of rotation is made coincident by removing the eccentricity of the optical element 16 and the jig 11. The refractive lens 19 is placed on the lens holder 13, and the distance to the front and back two surfaces is measured by the laser length measuring device 20 at two different points. The optical axis of the lens 19 and the eccentricity of the jig 11 are removed so as to coincide with the center of rotation, the lens holder 13 is lowered, the diffractive optical element 16 is brought into contact with the refractive lens 19 from the center position, and the sucked exhaust port 17 By returning the negative pressure to atmospheric pressure, the joint portion is gradually expanded from the center position to the peripheral portion, and both are directly joined. "

  Patent Document 3 (Japanese Patent Application Laid-Open No. 2002-52576) relates to an optical imaging element molding die and its assembly apparatus, and relates to a lens molding die and a prism molding die in an optical imaging element molding die. In order to perform alignment by accurately grasping the position of the lens mirror piece and the position of the prism mirror piece, the “incident side lens located on the incident side and the incident side lens are optically equivalent to each other”. An imaging side lens having an optical axis perpendicular to the optical axis of the incident side lens and positioned on the imaging side, and an optical axis of these lenses between the incident side lens and the imaging side lens. A molding die for forming an optical imaging element comprising a roof prism having a ridge line disposed so as not to be orthogonal to any of the optical axes of the incident side lens and the imaging side lens in a plane to be formed The incident side In an optical imaging element molding die having a mirror piece for incident side lenses for forming a lens and a mirror piece for imaging side lenses for forming the roof prism, a lens mirror surface is provided on the lens molding die 11. An optical imaging element provided with a lens mold block 13 having a mark for knowing the optical axis position of the frame, and provided with a prism mold block 14 having a mark for knowing the position of the prism mirror piece on the prism molding die 12 A "molding die" is disclosed.

  Patent Document 4 (Japanese Patent Laid-Open No. 2001-6203) relates to an optical head device by positioning with a positioning mark for center axis alignment formed on an objective lens and a phase control element and fixing it to one holder, In order to enable stable recording and reproduction of optical disc information with a simple configuration, the information is collected by focusing the light from the light source on the optical recording medium using an optical system equipped with an objective lens and a phase control element. In the optical head device for recording or reproducing the above, the objective lens and the phase control element are formed with a positioning mark for center axis alignment, and are positioned by this mark and fixed to one holder. More specifically, “the optical head device” is disclosed, and more specifically, “the optical head device is decentered on each surface where the phase control element 1 and the objective lens 2 face each other on the optical axis of the optical head”. For the purpose of adjustment, a concave Kubo positioning mark 11 is formed on the central axis of the annular zone of the phase control element, and a similar positioning mark 21 is formed on the symmetrical central axis of the objective lens. The eccentricity is adjusted so that the positioning mark 11 at the center of the annular zone of the control element coincides and is fixed to the holder 3. Thereby, the phase control element of the optical head device and the objective lens are integrated without being eccentric, and the DVD is integrated. In other words, the reproduction performance of the CD optical disk can be stably obtained as designed, while maintaining the reproduction performance of the optical disk of the system ”.

  Patent Document 5 (Japanese Patent Laid-Open No. 2006-235069) relates to an optical scanning device and an image forming apparatus. In an optical scanning device using a power diffraction surface, not only a beam spot diameter variation due to temperature variation but also an oscillation wavelength due to mode hopping. The challenges of realizing an optical scanning device that can reduce beam spot diameter fluctuations due to changes in the light beam and performing optical scanning with a more stable beam spot diameter, and also to realize an image forming apparatus using such an optical scanning device, After the light beam from the laser is converted into a light beam having a desired beam shape by a coupling lens, the light beam is guided to an optical deflector through an anamorphic optical element, and the optical beam deflected by the optical deflector is scanned optically. An optical scanning device that forms a light spot by condensing on a scanned surface by a system and optically scans the scanned surface, the scanning light The system includes one or more resin lenses, and the anamorphic optical element is a rotationally symmetric surface having a concentric power diffractive surface on one side, and the other surface is parallel to the main scanning direction and concentrated only in the sub-scanning direction. This is a resin lens that is a surface having a power diffractive surface having an optical action, and fluctuations in the beam waist position in the main scanning direction and / or sub-scanning direction due to mode hopping and temperature change in the semiconductor laser are made substantially zero. Thus, an optical scanning device characterized by setting the power of each of the power diffractive surfaces is disclosed.

JP 2003-251552 A JP 2000-56114 A JP 2002-52576 A Japanese Patent Laid-Open No. 2001-6203 JP 2006-235069 A

  Since the diffractive element and the diffractive element have opposite dispersion characteristics with respect to the light source wavelength, many optical systems that combine the refractive surface and the diffractive surface to stabilize the focal position even when the light source wavelength fluctuates have been implemented. ing. For example, an optical element that corrects a focal position shift of a refracting surface due to a change in environmental temperature with a diffractive surface is, for example, collimating optics of an optical printer or an optical scanning device for a digital copying machine as disclosed in Patent Document 5 described above. Implemented in the device. In this disclosed example, a step-like concentric diffractive surface that does not have power (condensing ability) and has power only when the wavelength shifts due to temperature disturbance is applied while the light source wavelength is kept at the reference wavelength. Has been. On the other hand, when used in an optical scanning device, a strict depth of focus is required to ensure image quality, and the curvature error required for an optical element is set to several tens of nm or less in terms of depth. The curvature of the step-like diffractive element is obtained from the regression curve of each step portion vertex as shown in FIG. 11. In order to guarantee this, the ring zone diameter and the step of each step portion are set to several tens of nm. There is a need to produce with precision.

Curvature evaluation in conventional spherical and aspherical lenses has been performed by obtaining cross-sectional curves. In order to obtain the cross-sectional curve, a method has been used in which the probe displacement is obtained by scanning a contact-type probe including an atomic force probe so as to pass through a vertex of a spherical surface or an aspherical surface. In a continuous curved surface, the vertex search is easy, and the contact probe is scanned in the direction perpendicular to the scanning direction when the cross-section curve is acquired to find the highest point of probe displacement (the lowest point on the concave surface).
However, the conventional vertex search cannot be used for the step-like concentric diffractive surfaces as described above, and the accuracy of matching with the diffractive surface rotation center corresponding to the vertices is insufficient. It has been difficult to obtain accuracy.

  In the case of the above-described prior art, Patent Document 4 discloses that marking is performed at the center of a diffractive surface on a staircase and that is used as a reference for assembly. In this case, even if a mark that does not function directly optically is formed at the center of the optical surface, the optical characteristics are ensured. However, in an ordinary optical element, the light intensity that passes through the center is the highest. In most cases, it is difficult to form a pattern that is a disturbance as a shape error in the vicinity thereof.

Japanese Patent Application Laid-Open No. H10-228667 discloses that a free-form optical element is processed by forming a processing mark by a grinding tool in an optically unnecessary area and using it as a processing reference. Here, the grinding mark is a toric (or torus) type ship-shaped dent, which is used as a processing origin by searching for the apex.
However, in this conventional technique, it is necessary to search for the apex of the machining trace itself, which is troublesome, and since a relatively large machining trace is necessary so that the apex search is possible, there is a sufficiently large optically unused area. There is a problem that it is necessary and is difficult to apply to a collimating optical element of an optical pickup or an optical scanning device.

A method of alignment using a crosshair provided on the outer periphery of the diffractive surface is disclosed in Patent Document 2, and in the embodiment of this document, the diffractive surface is formed by lithography, and a cross mark is also formed by the drawing apparatus. Is.
However, this conventional technique is formed on a resist and can be applied to a diffractive element having a depth of about 10 μm, but cannot be applied to an element having a diffractive surface formed on a curved surface. In the embodiment of the same decentralization, the step of attaching the diffractive element to the refractive optical element is disclosed. However, when a modification such as attaching to the curved surface is accompanied, the mark remaining on the completed element is displaced. There is a possibility, it can not be used for final inspection.

The present invention has been made in view of the above circumstances, a molding die having a mark as a measurement standard that can accurately perform the shape evaluation of a diffraction pattern that is stepped, and a method for processing the molding die, An object is to provide an optical element molded with the molding die, an optical device using the optical element, an optical device, an optical scanning device, an image display device, and an optical pickup device.
The present invention also provides a method of forming a mark as a measurement standard capable of accurately evaluating the shape of a diffraction pattern having a staircase shape, and the mark is formed in a small optically unused area. Since it can be formed, it can be formed without impairing the optical performance, and can be applied to a small-diameter lens such as an optical pickup or a collimating optical element of an optical scanning device. In the present invention, the diffractive surface cutting process of the molding die can be carried out in a series of processing operations, eliminating the need for special position indexing and dedicated tools, and without sacrificing delivery time and cost. It is an object of the present invention to realize a high-precision diffraction pattern.

In order to solve the above-mentioned problems, the present invention employs the following solutions.
The first means of the present invention is a metal mold for an optical element having a diffraction pattern in which the cross section of the diffraction surface forms a stepped pattern, and the shape of the ridge line of the stepped portion viewed from the optical axis direction is a straight line, circle or ellipse. In the mold, a pattern in which at least two V grooves intersect each other in an optically unnecessary area on the outer periphery of the diffractive surface is formed, and the intersection is used as a base point for measurement and mold processing.

According to a second means of the present invention, there is provided a diffraction pattern for an optical element having a diffraction pattern in which the cross section of the diffraction surface forms a stepped pattern, and the shape of the ridge line of the stepped portion viewed from the optical axis direction is a straight line. An optically unnecessary area on the outer periphery of the surface has a V-groove parallel to the ridgeline, and at least two straight V-grooves orthogonal to the ridgeline are formed, and the intersection is used as a base point for measurement and mold processing. It is characterized by using.
Further, according to a third means of the present invention, in the molding die of the second means, the plurality of substantially perpendicular V grooves are a pair of two pairs facing each other across the diffraction surface. The straight lines are arranged on two straight lines, and the straight lines are orthogonal to the stepped ridge lines forming the diffraction surface.

According to a fourth means of the present invention, there is provided a diffraction pattern for an optical element having a diffraction pattern in which the cross section of the diffraction surface forms a stepped pattern, and the shape of the ridge line of the stepped portion viewed from the optical axis direction is a circle. A circular V-groove having a shape similar to the ridgeline and having a common center in an optically unnecessary region on the outer periphery of the surface, and forming at least two linear V-grooves substantially perpendicular to the circular V-groove; The intersection point is used as a base point for measurement and mold processing.
Further, the fifth means of the present invention is a pair of two pairs, each having a plurality of substantially perpendicular V grooves facing each other across a circular diffraction surface, in the molding die of the fourth means. The grooves are parallel to each other.

According to a sixth means of the present invention, in the optical element molding die having a diffraction pattern in which the cross section of the diffraction surface forms a stepped pattern and the shape of the ridge line of the stepped portion viewed from the optical axis direction is an ellipse. An elliptical V-shaped groove having a shape similar to the ridgeline and having a common center in an optically unnecessary area on the outer periphery of the surface, and forming at least two linear V-shaped grooves substantially orthogonal to the V-shaped groove, The intersection point is used as a base point for measurement and mold processing.
According to a seventh means of the present invention, in the molding die of the sixth means, a plurality of substantially perpendicular V-grooves are a pair of four opposing each other across an elliptical diffraction surface. The grooves are parallel to each other.

  According to an eighth means of the present invention, in the molding die of any one of the first to seventh means, the angle between the two inclined surfaces of the V-groove shape is the standing shape of the step-shaped portion forming the diffraction surface. The opening angle θ is the same as the opening angle θ of the wall base, and the opening angle θ is an obtuse angle of 92 to 110 degrees.

  A ninth means of the present invention is a method for processing a molding die according to any one of the third, fifth and seventh means, and the plurality of substantially orthogonal V grooves are processed at the time of diffraction surface processing. From the object gripping state to the attaching / detaching state, using a rotating stage around an axis orthogonal to the central portion of the diffractive surface, the rotation is indexed in units of 90 ° and engraved.

The tenth means of the present invention is an optical element, characterized in that it is molded using the molding die of any one of the first to eighth means.
The eleventh means of the present invention is an optical apparatus, characterized in that the optical element of the tenth means is used.

  The twelfth means of the present invention comprises a light source, a first optical system that collimates the light beam from the light source and converts it into a desired beam form, a deflection means that deflects and scans the light beam from the first optical system, In an optical scanning apparatus having a second optical system that forms an image of a light beam deflected and scanned by a deflecting unit on a surface to be scanned, the optical element of the tenth unit is used for the first optical system or the second optical system. It is characterized by that.

  According to a thirteenth means of the present invention, in an image display device including a light source, an illumination optical system, an image display element, and a projection lens, the optical element constituting the illumination optical system or the projection lens is arranged in the tenth aspect. The optical element of the means is used.

  The fourteenth means of the present invention includes a light source, an optical system for collimating the light beam from the light source, an objective lens for condensing the collimated light beam on the optical recording medium, and a reflected light beam from the optical recording medium. In an optical pickup device including a condensing lens that emits light and a light receiving element that receives the collected light beam, an optical element of a tenth means is provided in at least one of the collimating optical system, the objective lens, and the condensing lens. It is used.

  In the molding die of the present invention, a pattern (mark) is formed by crossing at least two V grooves in an optically unnecessary area on the outer periphery of the diffractive surface, and the intersection point is a base point for measurement and die processing As a result, it is possible to accurately measure the shape of an optical element having a stepped diffractive surface whose center is a flat surface or its mold, and to realize a diffractive optical element with higher accuracy. Moreover, since it can be used for the inspection at the time of production, it is possible to reduce the manufacturing cost by shortening the inspection time.

  Hereinafter, the best mode for carrying out the present invention will be described in detail based on the embodiments shown in the drawings.

  FIG. 1 is a perspective view of a molded product of a diffractive lens showing an example of an optical element in which measurement reference marks are formed on the outer periphery. The material of the diffractive lens 1 is an olefin polymer having excellent fluidity and moisture resistance. In the optically unnecessary area 7 on the outer peripheral portion from the concentric explanation surface 5 of the diffractive lens 1, a circumferential mark 3 of a belt-like projection having the same center as the diffraction pattern, and a radial direction orthogonal to the circumferential mark 3. Four extending marks 2a, 2b, 2c, 2d are formed. These marks are formed by imprinting V grooves on a molding die (not shown).

  FIG. 2 shows an example of a 5-axis control processing machine used for processing a diffractive surface of a molding die and a reference V-groove for molding an optical element such as the diffractive lens shown in FIG. This processing machine has a five-axis configuration with a linear three-axis slide of X, Y, and Z and two rotation axes of B and C. The linear triaxial positioning resolution is 1 nm, and the B and C axis angular resolution is 1 / 100,000 degrees. The base material of the mold member is stainless steel, and the electroless Ni plating having a thickness of 300 μm is applied to the surface on which the diffraction pattern is formed. The mold member 30 clamps the workpiece surface on the B-axis table 13 rotatably installed on the X-axis table 11 with the processing surface facing upward. A single crystal diamond tool 16, which is used for both the diffraction surface and V-groove processing, is fixed to a tool holder 17 connected to a C-axis spindle 14. After the blade tip of the single crystal diamond tool 16 is positioned at a predetermined position in the XZ plane, the Z-axis slide and the Y-axis slide 12 are lowered and cut into the plating surface of the mold member 30. In synchronization with the notch, the B-axis table 13 rotates counterclockwise and groove processing on the arc is performed.

  FIG. 3 shows how the stepped diffraction surface and the reference V-groove are processed by a non-rotating tool. The single crystal diamond tool 16 includes a diamond chip 16a and a shank 16b, and the cutting edge at the tip of the diamond chip 16a has a flat shape called a flat tool suitable for cutting a rectangular groove. Since the stepped diffractive surface requires a strict squareness at the step part orthogonal to the rotation axis, the tilt of the C axis is finely adjusted based on the processing result of the dummy workpiece, and the orthogonality with the rotation axis of the cutting edge is set. Secured. In addition, the staircase pattern is transferred at the corner K of the cutting edge of the diamond tip 16a. The opening angle of the corner is 96 degrees in consideration of the release property of the molded product and the visibility of the V groove after processing. And slightly obtuse.

  After processing the concentric diffraction pattern on the mold member 30, V-groove processing is performed on the optically unnecessary portion (optically unnecessary region on the outer periphery of the diffraction region 35 on the mold) 37 on the outer periphery thereof. Since the cutting edge is in a horizontal state, 48 degrees, which is a half of the opening angle of the bite corner, is rotated counterclockwise by the C axis from this position.

  In this posture, the reference V-groove in which the diffraction surface and the rotation axis coincide with each other can be easily machined by rotating the B-axis table 13 in synchronism with the notch similarly to the machining of the staircase portion. When the cutting tool 16 is tilted in the counterclockwise direction, it is difficult to precisely match the rotation center of the C-axis spindle 14 with the cutting tool corner K. Therefore, the corner K is displaced in the XY direction simultaneously with the rotation. Will occur. Even in a state where this deviation occurs, an accurate vertex search mark can be obtained according to the following procedure.

FIG. 4 illustrates a procedure for forming a reference V-groove on the mold member 30 for forming a diffraction surface having a concentric diffraction pattern. Here, after processing the circumferential V-groove 33 in the mold member 30, the radial V-grooves 32a to 32d are processed.
First, the corner K of the tool (bite) 16 is moved to a coordinate that coincides with the rotation center of the C-axis spindle 14. Since this uses a coordinate system for stair shape processing, the point K and the center of rotation are not exactly coincident after the rotation of the C-axis spindle 14 is applied. The mold member 30 has a cylindrical shape, and a V-groove is processed from the outside toward the center by a Z-axis slide. The four radial V grooves 32a to 32d are processed (marked) by changing the rotation angle of the B-axis table 13 to 0 °, 90 °, 180 °, and 270 °. At this time, since the diffractive surface 35 protrudes from the optically unnecessary area 37 in the mold member 30, it is necessary to control the movement amount of the cutting tool 16 so as not to contact the diffractive surface 35.

  FIG. 5 explains that a line connecting the intersections of two opposing V grooves of the mold member 30 shown in FIG. 4 is a probe scanning line. δ is the amount of deviation from the rotation center 36 of the corner (point K) of the cutting tool caused by rotation of the C-axis spindle 14. By processing according to the above procedure, as shown in the figure, the crossing points O and Q of the opposing radial V-grooves are symmetrical and both are shifted by δ, so the line segment connecting point O and point Q accurately passes through the apex. Will be. The same applies to the point P and the point R. If these line segments are used as probe trajectories at the time of measurement, an accurate sectional curve can be acquired. In the measurement of such a stepped diffraction surface, a laser probe type non-contact three-dimensional measuring device is used because the data of corners and smears is not slowed down. In this method, the laser beam is autofocused on the surface to be measured, and the lens displacement caused by the autofocus is monitored by scanning in that state, and the coordinates of the surface to be tested are acquired. In this measuring apparatus, the position of the laser spot on the test surface can be accurately confirmed with an image by a CCD camera arranged coaxially with the laser optical path. By performing binarization, centroid calculation, etc. on this image, it is possible to accurately match the laser spot to the marker formed on the test surface.

  FIG. 6 illustrates a means for more accurately specifying the intersection of the V grooves. FIG. 6 is an enlarged view of the intersection P of the V-grooves with a CCD camera. The groove depth is 2 μm and the groove width is 4 μm. Image processing is used to accurately identify the intersection from the line having this width. When illumination coaxial with the CCD camera is used, the V-groove portion is recognized as a black crosshair in the field of view because the amount of reflected light is smaller than that of an unprocessed plane. Since the opening angle of the V groove is not 90 ° but an obtuse angle, the reduction of reflected light is remarkable. By binarizing the cross line in the image processing area 45 for specifying the intersection and obtaining the center of gravity, the intersection can be specified with submicron resolution. Points O to R in FIG. 5 are obtained by the same processing.

Next, FIG. 7 illustrates a procedure for forming a mold member 59 and a reference V groove for forming a concentric elliptical diffraction surface. The hatched portion inside the outermost periphery 50 of the elliptical diffraction pattern is an optically effective area, and the outside thereof is a planar optically unused area. In this embodiment, the mold member 59 is a rectangular parallelepiped.
First, after forming a step-like diffraction pattern on the mold member 59 as in the case of the concentric mold member, elliptical diffraction is performed at the same processing origin without removing the mold member 59 as a workpiece from the processing machine. A circumferential V-groove 51 similar to the pattern is processed. In the ellipse shape evaluation, it is necessary not only to pass through the center of the ellipse as a measurement probe trajectory but to be parallel to the major axis and the minor axis. Therefore, two V grooves intersecting with the circumferential V groove 51 similar to the elliptical diffraction pattern 50 are formed on each of the front, rear, left and right.

Next, the tool is moved to the X coordinate where the corner portion K of the tool (bite 16) coincides with the center of the ellipse in the same way as when the circular reference V groove is formed. In the rotational coordinates of the B axis, the state where the elliptical minor axis is parallel to the Z axis is set to B = 0 °, and the V grooves 52a and 52c parallel to the elliptical minor axis are imprinted at the B axis 0 °. V grooves 52b and 52d at 90 °, V grooves 53a and 53c at B = 180 °, and V grooves 53b and 53d at B = 270 °. At this time, the amount of deviation from the center of the ellipse caused by the change in the posture of the tool by the C-axis spindle 14 is X1, and in this embodiment, X1 = Z1.
Next, by obtaining a point S and a point T, which are the midpoints of the V-groove intersection, and connecting them, a measurement line passing through the center of the ellipse and parallel to the minor axis can be obtained. Similarly, the point U and the point V are obtained in the long axis direction, and a measurement line can be obtained by connecting the points.

  FIG. 8 shows another embodiment of FIG. 7. Instead of the circumferential V groove 51 used in FIG. 7, a linear V parallel to the elliptical short axis or the elliptical long axis is shown. Grooves 61a, 61b, 61c, 61d are formed.

  Next, FIG. 9 shows an example in which a reference mark is formed by a molded article 79 of an optical element having a linear diffraction surface. In the same manner as in the above example, using the same processing standard and tool as in the diffraction pattern processing, outer peripheral marks 71a, 71b parallel to the diffraction pattern 70, outer peripheral marks 72a, 72b, 73a, 73b orthogonal to the diffraction pattern 70, 74a and 74b are formed. A straight line connecting 72a and 72b facing each other with the diffraction part interposed therebetween is a measurement line. In this embodiment, it is assumed that three cross sections are obtained.

  FIG. 10 shows an example of a mold member 89 for molding the reference mark and the linear diffraction surface of the molded product of the optical element shown in FIG. It can be easily processed by X, Y, Z linear three-axis slide using the X-axis table 11 and the Z-axis slide and Y-axis slide 12 of the machine.

  As described above, in the molding die of the present invention, a pattern (mark) in which at least two V grooves intersect each other in an optically unnecessary region on the outer periphery of the diffraction surface is formed, and the intersection is measured and By using it as a base point when processing a mold, it is possible to accurately measure the shape of an optical element having a stepped diffractive surface whose center is a flat surface or its mold, and to realize a diffractive optical element with higher accuracy. Moreover, since it can be used for the inspection at the time of production, it is possible to reduce the manufacturing cost by shortening the inspection time.

  Further, in the molding die of the present invention, in the optically unnecessary area on the outer periphery of the diffraction surface, a V-groove parallel to the ridge line, or a circular or elliptical shape having a shape similar to the ridge line and having a common center. Since there are at least two straight V-grooves having V-grooves and perpendicular to the V-grooves, and the intersection of the V-grooves is used as a base point (mark) at the time of measurement and mold processing, a diffraction pattern as an optical surface By using parallel or similar marks, there are advantages such as easy processing and a small area required for the marks, and it is possible to minimize the cost increase associated with mark formation.

  Furthermore, in the molding die of the present invention, by forming the mark with a V-groove, the tool (for example, single crystal diamond tool 16) used for processing the diffraction part can be used as it is, the working time can be shortened, and the tool can be changed This is advantageous in terms of ensuring accuracy. Further, it is not necessary to prepare a dedicated tool for forming a mark, which is advantageous in terms of cost. Furthermore, positioning resolution of about 1/10 of the V groove width can be obtained by image processing of the intersection of two V grooves.

  Furthermore, in the molding die of the present invention, in addition to the above-described configuration, the V-groove shape has the same angle between the two inclined surfaces as the opening angle θ of the standing wall root of the stepped portion that forms the diffraction surface. The opening angle θ is an obtuse angle of 92 to 110 degrees, so that when the molded product is ejected in the direction of the optical axis in forming the stepped portion, it acts as a draft and suppresses deformation at the time of mold release. I can do it. Further, in specifying the V-groove intersection point by the CCD camera image, since there is no return light due to two-surface reflection compared to the case where the amount of light reflected on the V-groove surface is 90 °, the groove shape can be recognized with higher contrast.

  In the present invention, since the optical element is molded using the molding die as described above, an optical element such as a diffractive optical element having a fine stepped pattern on the surface can be easily and accurately formed. . Moreover, since not only a diffractive optical element but also a test surface changes discontinuously as an optical element, it is possible to use an optical element that requires accurate measurement line positioning with micron accuracy. For example, the present invention can also be applied to a case where coordinate estimation by interpolation is difficult and submicron level shape accuracy is required such as an optical surface.

  The diffractive optical element having the diffraction pattern as shown in the above embodiments can be applied to various optical devices, and can be used for various optical devices such as a still camera, a video camera, an optical microscope, and a telescope. The optical element of the present invention is particularly suitable for use in an optical system such as an optical scanning device, an image display device, and an optical pickup device. An example is shown below.

  FIG. 12 is a schematic configuration diagram showing an example of an optical scanning device using the optical element of the present invention. In FIG. 12, a light beam 104 emitted from a semiconductor laser 101 passes through a collimating lens 102 and an aperture 103 of the first optical system and is shaped into a beam. By the action of a cylindrical lens 105, the reflected light is deflected and reflected by a polygon mirror 106 that is a deflecting unit. After being formed as a line image (imaged in the sub-scanning direction and long in the main scanning direction) on the surface, it is deflected and scanned by the polygon mirror 106. The light beam deflected and scanned by the polygon mirror 106 is scanned on the surface to be scanned of the photosensitive drum 108 which is an image carrier by the second optical system 107 (first scanning lens 107-1 and second scanning lens 107-2). Scanned as a beam spot. In addition, a beam detection sensor 109 for synchronization detection is provided at a position optically equivalent to the surface of the photosensitive drum 108 serving as a scanned surface, and the start position of beam scanning in the main scanning direction is detected.

  In the optical scanning device 100 having such a configuration, the collimating lens 102 and the cylindrical lens 105 of the first optical system, or the first scanning lens 107-1 and the second scanning lens 107-2 of the second optical system 107 are included in the above-described configuration. The diffractive optical element of the present invention can be used, and clear image writing can be performed.

  Next, FIG. 13 is a schematic configuration diagram showing an example of an image display device (projector) using the optical element of the present invention. As shown in FIG. 13, the image display apparatus 200 includes at least a light source (lamp) 201 that emits light, a spatial light modulator (for example, a liquid crystal light valve) 203 that forms pixels, and spatial light modulation of the light. An illumination optical system 202 that uniformly illuminates the light source 203, a projection lens 205 for projecting image light from the spatial light modulator 203 onto the screen 206, and an optical path disposed between the spatial light modulator 203 and the projection lens 205. The optical path deflecting element 204 for deflecting the light is disposed.

This image display apparatus 200 has a configuration in which a spatial light modulator (liquid crystal light valve) 203 is combined with an optical path deflecting element (also referred to as a pixel shifting element, a wobbling element, an optical path shifting element, etc.) 204. By using the optical path deflecting element 204 capable of deflecting (pixel shifting) the light path of the image light from the modulator 203, an image having a resolution that is an integral multiple of the spatial light modulator 203 is displayed on the screen 206. Can do.
As the spatial light modulator (liquid crystal light valve) 203, a single plate type in which pixels of three colors R (red), G (green), and B (blue) are arranged on one liquid crystal light valve, A three-plate type in which liquid crystal light valves that individually display R, G, and B color images are superimposed is used, and a color image can be displayed.

  In the image display apparatus 200 having such a configuration, the above-described diffractive optical element of the present invention can be used for the lens, the diffractive optical element, the projection lens 205, and the like used in the illumination optical system 202, and a clear image display can be performed. Is possible.

  Next, FIG. 14 is a schematic configuration diagram showing an example of an optical pickup device using the optical element of the present invention. In FIG. 14, light emitted from a light source (for example, a semiconductor laser) 301 becomes substantially parallel light by a collimating lens 302, passes through a polarizing beam splitter 303 and a quarter-wave plate 304, and is recorded by a recording medium (for example, an optical disk) 306 by an objective lens 305. Condensed to The reflected light from the optical disk 306 passes through the objective lens 305 and the quarter wavelength plate 304, is reflected by the polarization beam splitter 303, which is a light beam separating means, is focused by the condenser lens 307, and is detected by the photodetector (light receiving element) 308. Irradiated on top.

  In the configuration of FIG. 14, the objective lens 305 is configured to have a mechanism (a condensing spot position control mechanism (not shown)) that can move with respect to the optical disk 306 in the optical axis direction and the direction orthogonal to the optical axis. By adjusting the relative position of the focused spot with respect to the optical disc 306, the recording layer in the optical disc 306 is modulated and irradiated with light from the light source 301 to record information, and the light from the light source 301 is also recorded. The information can be read by irradiating the recording layer in the optical disk 306 and detecting the reflected light by the photodetector 308.

  In the optical pickup device having such a configuration, the above-described optical element of the present invention can be used for the collimator lens 302, the objective lens 305, the condenser lens 307, etc., and information can be recorded and reproduced with high accuracy. Is possible.

It is a perspective view of the molded product of the diffraction lens which shows an example of the optical element which formed the measurement reference mark in the outer peripheral part. It is a schematic perspective view which shows an example of the 5-axis control processing machine used for the metal mold | die process of the diffraction surface of a shaping die and the reference | standard V groove. It is a figure for demonstrating the processing form of the step-shaped diffraction surface and reference | standard V-groove by a non-rotating tool. It is a figure for demonstrating the formation procedure of the metal mold | die member for shape | molding the diffraction surface of a concentric circular diffraction pattern, and the reference | standard V groove | channel. It is explanatory drawing in the case of making the line which connects two V-groove intersections provided in the outer peripheral part of a concentric circular diffraction pattern into a probe scanning line. It is a figure for demonstrating the means for pinpointing a V-groove intersection more correctly. It is a figure for demonstrating the formation procedure of the metal mold | die member for shape | molding a concentric elliptical diffraction surface, and the reference | standard V groove | channel. It is a figure which shows the other example of formation of the metal mold | die member for shape | molding a concentric elliptical diffraction surface, and the reference | standard V groove | channel. It is a figure which shows the example which formed the marker for a reference | standard with the molded article of the optical element which has a linear diffraction surface. FIG. 10 is a perspective view showing an example of a mold member for forming a reference mark and a linear diffraction surface of the molded article of the optical element shown in FIG. 9. It is a figure explaining the accuracy evaluation item of a stair-like diffraction surface. It is a schematic block diagram which shows an example of the optical scanning device using the optical element of this invention. It is a schematic block diagram which shows an example of the image display apparatus using the optical element of this invention. It is a schematic block diagram which shows an example of the optical pick-up apparatus using the optical element of this invention.

Explanation of symbols

1: Diffraction lens molded product with a measurement reference marker formed on the outer periphery 2a: Radial direction marker (0 °)
2b: radial marker (90 °)
2c: radial marker (180 °)
2d: radial marker (270 °)
3: Circumferential marker 5: Concentric diffractive surface 7: Optically unnecessary area on the outer periphery of the diffraction area 11: X-axis table 12 :: Z-axis slide and Y-axis slide 13: B-axis table 14: C-axis spindle 16: Single Crystal diamond tool (machining tool)
16a: Diamond chip 16b: Shank 17: Tool holder 30: Work piece (mold member)
32a: Radial V groove (0 °)
32b: Radial V groove (90 °)
32c: Radial direction V-groove (180 °)
32d: V-groove in the radial direction (270 °)
33: Circumferential V-groove 35: Diffraction pattern area 36: Center of diffraction pattern 37: Optically unnecessary area on the outer periphery of the diffraction area on the mold 42: Line passing through the diffraction pattern and parallel to the radial V-groove 45: Intersection Image processing area for identification 50: Outermost circumference of elliptical diffraction pattern 51: Circumferential V-groove 52a, 52c similar to elliptical diffraction pattern: V-groove 52b, 52d parallel to elliptical short axis imprinted at B-axis 0 ° : V-shaped groove 53a, 53c parallel to the elliptical long axis imprinted at B axis 90 ° 53: V-shaped groove 53b, 53d parallel to the elliptical short axis imprinted at 180 ° B-axis: Ellipse minor axis imprinted at 270 ° B-axis 59: Ellipse pattern diffractive lens molding die members 61a, 61c: Peripheral V-grooves parallel to the major axis 61b, 61d: Peripheral V-grooves parallel to the major axis 70: Stairs forming a linear pattern Diffractive surfaces 71a, 7 b: Peripheral part mark parallel to the diffraction pattern 72a, 72b, 73a, 73b, 74a, 74b: Peripheral part mark orthogonal to the diffraction pattern 79: Diffraction lens molded article with a linear pattern in which the measurement reference mark is formed on the outer peripheral part 81a: Peripheral V-grooves 82a, 83a, 84a parallel to the diffraction pattern: Peripheral V-grooves orthogonal to the diffraction pattern 89: Diffraction lens molding die member having a linear pattern 100: Optical scanning device 101: Light source 102: Collimating lens 105: Cylindrical lens 106: Polygon mirror (deflection means)
107: second optical system 107-1, 107-2: scanning lens 200: image display device 202: illumination optical system 203: spatial light modulator 204: optical path deflecting element 205: projection lens 300: optical pickup device 301: light source 302 : Collimating lens 303: Polarizing beam splitter 304: 1/4 wavelength plate 305: Objective lens 306: Optical disk 307: Condensing lens 308: Optical disk (optical recording medium)

Claims (14)

In the molding die of the optical element of the diffraction pattern in which the cross section of the diffraction surface forms a stepped pattern, and the shape of the ridge line of the stepped portion viewed from the optical axis direction is a straight line, a circle or an ellipse,
A molding die characterized by forming a pattern in which at least two V-grooves intersect in an optically unnecessary region on the outer periphery of the diffraction surface, and using the intersection as a base point for measurement and mold processing. In the molding die of the optical element of the diffraction pattern in which the cross section of the diffractive surface forms a stepped pattern, and the shape of the ridgeline of the stepped portion viewed from the optical axis direction is a straight line
An optically unnecessary region on the outer periphery of the diffractive surface has a V-groove parallel to the ridgeline, and at least two straight V-grooves orthogonal to the ridgeline are formed. A molding die characterized by being used as a base point. The molding die according to claim 2,
A plurality of substantially perpendicular V-grooves are a pair of two pairs facing each other across the diffraction surface, and the pair is arranged on one straight line, and the straight line is a stepped ridge line forming the diffraction surface. Molding die characterized by being orthogonal. In the mold of the optical element of the diffraction pattern in which the cross section of the diffractive surface forms a stepped pattern, and the shape of the ridge line of the stepped portion viewed from the optical axis direction is a circle,
An optically unnecessary region on the outer periphery of the diffractive surface has a circular V-shaped groove that is similar to the ridgeline and has a common center, and at least two linear V-shaped grooves that are substantially orthogonal to the circular V-shaped groove are formed. A molding die characterized in that its intersection is used as a base point for measurement and die processing. In the molding die according to claim 4,
A plurality of V-grooves which are substantially orthogonal to each other are a pair of two pairs facing each other across a circular diffraction surface, and the grooves forming the pair are parallel to each other. In the molding die of the optical element of the diffraction pattern in which the cross section of the diffractive surface forms a stepped pattern, and the shape of the ridge line of the stepped portion viewed from the optical axis direction is an ellipse,
An optically unnecessary region on the outer periphery of the diffractive surface has an elliptical V-shaped groove that is similar to the ridgeline and has a common center, and at least two linear V-shaped grooves that are substantially perpendicular to the elliptical V-shaped groove are formed. A molding die characterized in that its intersection is used as a base point for measurement and die processing. In the molding die according to claim 6,
A plurality of V-grooves substantially orthogonal to each other are a pair of four pairs facing each other across an elliptical diffraction surface, and the pair of grooves are parallel to each other. In the molding die according to any one of claims 1 to 7,
In the V-groove shape, the angle formed by the two slopes is the same as the opening angle θ of the standing wall root of the stepped portion forming the diffraction surface, and the opening angle θ is an obtuse angle of 92 to 110 degrees. Molding mold. A method for processing a molding die according to any one of claims 3, 5, and 7,
A plurality of substantially perpendicular V-grooves are indexed in 90 ° increments using a rotary stage around the axis perpendicular to the center of the diffraction surface, without attaching / detaching, from the workpiece gripping state during diffraction surface processing. A method of processing a molding die characterized by engraving.   An optical element formed using the molding die according to claim 1.   An optical device using the optical element according to claim 10. A light source, a first optical system that collimates the light beam from the light source and converts it into a desired beam form, deflection means that deflects and scans the light beam from the first optical system, and a light beam deflected and scanned by the deflection means. In an optical scanning device including a second optical system that forms an image on a surface to be scanned,
An optical scanning device using the optical element according to claim 10 in the first optical system or the second optical system. In an image display device comprising a light source, an illumination optical system, an image display element, and a projection lens,
An image display device using the optical element according to claim 10 for an optical element constituting the illumination optical system or the projection lens. A light source, an optical system for collimating a light beam from the light source, an objective lens for condensing the collimated light beam on an optical recording medium, a condensing lens for condensing a reflected light beam from the optical recording medium, In an optical pickup device provided with a light receiving element that receives received light flux,
An optical pickup device using the optical element according to claim 10 for at least one of the collimating optical system, the objective lens, and the condenser lens.

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