JP4244570B2 - Cutting method for diffractive optical element and cutting method for mold for forming diffractive optical element - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a diffractive optical element having a diffractive surface in which a concavo-convex pattern is formed with a non-uniform density, a diffractive optical element molding die for molding the diffractive surface, a diffractive optical element cutting method, and a diffractive optical element molding The present invention relates to a cutting method for a metal mold and a cutting apparatus.
[0002]
[Prior art]
Since the diffractive optical element has various functions such as a lens function, a branching / combining function, a light intensity distribution conversion function, a wavelength filter function, and a spectral function, it has been widely used in various optical systems.
For example, a zone plate as a lens and a grating (diffraction grating) as a spectroscopic element have been put into practical use for a long time.
[0003]
The concavo-convex pattern to be provided in the diffractive optical element is determined depending on the application and varies widely. For example, the concavo-convex pattern of the grating is a straight line arranged at the same pitch. In addition, the uneven pattern of the zone plate is concentric (annular) arranged at different pitches depending on the radial position.
[0004]
Each diffractive optical element is ideally designed so that incident light travels only in the intended direction and does not travel in any other direction.
However, in actuality, the light may travel in an unintended direction, flare may occur, the diffraction efficiency may decrease, and the effective light intensity may decrease.
Possible causes are (1) the wavelength of incident light is different from the design value, and (2) a shape error in the diffractive surface of the diffractive optical element. The cause (1) can be solved by combining a plurality of different diffractive optical elements. Various techniques have already been proposed for this.
[0005]
On the other hand, it is considered that the cause (2) can be solved by increasing the processing accuracy of the diffraction surface.
Here, for the processing of the diffractive surface, “cutting” in which the surface to be processed is traced with a tool having a sharp tip (so-called bite) is applied.
In order to increase productivity, molding with a mold is preferable to direct cutting, but in that case, the cutting is applied to the processing of the molding surface of the mold. The reversal shape of the molding surface is directly transferred to the diffraction surface.
[0006]
In order to increase the accuracy of this cutting process, the error of the relative movement between the bite and the workpiece is usually fed back to increase the movement accuracy, and the complexity of the diffractive surface to be formed (uneven pattern formation density) Accordingly, the diameter of the cutting tool tip should be reduced.
However, since the machined surface roughness increases when the diameter of the cutting tool tip is small, the normal feed is reduced. As a result, the tracing distance of the cutting edge becomes long, processing takes time, and the cutting edge wear also increases.When the formation density of the uneven pattern is sufficiently small, it is preferable to use a cutting tool having a tip diameter as large as possible. The
[0007]
Therefore, conventionally, a bit having a small tip diameter is used when the formation density of the concavo-convex pattern is high, and a bit having a large tip diameter is used when the formation density of the concavo-convex pattern is low, and the formation density of the concavo-convex pattern is not uniform like a zone plate. In this case, a cutting tool with a small tip diameter that fits the densest part is used.
[0008]
[Problems to be solved by the invention]
However, if a cutting tool with a small tip diameter is used when the uneven pattern formation density is non-uniform, not only will the processing time of the low formation density part be increased, but it will be required for that part. It has been found that there is a possibility of generating flare without obtaining a shape.
[0009]
  Thus, if the optical performance of the portion with a low formation density of the concave / convex pattern cannot be obtained sufficiently, the overall performance of the diffractive optical element is deteriorated even if the optical performance of the portion with a high formation density is good. To do.
  Therefore, the present invention can provide high optical performance even when the uneven pattern formation density is non-uniform.TimesFolding optical element cutting method,as well asCutting method of diffractive optical element molding dieTheThe purpose is to provide.
[0010]
[Means for Solving the Problems]
[0012]
  One aspect of the cutting method for a diffractive optical element of the present invention has a diffractive surface on which uneven patterns are formed with a non-uniform density.A method of cutting a diffractive optical element for cutting the diffractive surface of a diffractive optical element,A first cutting step of processing the first region of the diffractive surface with a first cutting tool mounted on the cutting processing device; and a tip diameter larger than that of the first cutting tool mounted on the cutting processing device. A second cutting step of processing a second region of the diffractive surface having a density of the uneven pattern lower than that of the first region by the second cutting tool; the first cutting step; and the second cutting step. A cutting tool, and a tool exchanging process for exchanging a tool used for processing the diffraction surface between the first tool and the second tool, and in the tool exchanging process, The tip position of the cutting tool at the start of machining in the cutting process performed after replacement is made to coincide with the tip position of the cutting tool at the end of machining in the cutting process performed before replacement.It is characterized by that.
[0013]
The method for cutting a diffractive optical element molding die according to the present invention has a molding surface on which uneven patterns are formed with a non-uniform density.A method of cutting a diffractive optical element molding die for cutting the molding surface of a diffractive optical element molding die,A first cutting step of processing the first region of the molding surface with a first cutting tool mounted on the cutting processing device; and a tip diameter larger than that of the first cutting tool mounted on the cutting processing device. A second cutting step of processing a second region of the molding surface having a density of the uneven pattern lower than that of the first region, a first cutting step and the second A cutting tool, and a tool exchanging process for exchanging a tool used for processing the molding surface between the first tool and the second tool. In the tool exchanging process, The tip position of the cutting tool at the start of machining in the cutting process performed after replacement is made to coincide with the tip position of the cutting tool at the end of machining in the cutting process performed before replacement.It is characterized by that.
[0014]
  In the cutting tool exchanging step, the leading end position may be matched based on the output of a sensor that detects the deviation between the leading end position of the cutting tool before replacement and the leading end position of the cutting tool after replacement.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
A first embodiment of the present invention will be described with reference to FIGS. 1, 2, 3, 4, 5, and 6.
[0016]
In the present embodiment, a mold for forming a diffractive optical element having a diffractive surface on which uneven patterns are formed with a non-uniform density is produced.
FIG. 1 is a diagram illustrating a mold 10 according to the present embodiment. FIG. 1A is a completed form (a cross-sectional view and a plan view) of the mold 10 of the present embodiment, and FIG. 1B is a blank material (mold original mold) 10 ′ before the mold 10 is processed. (Sectional view).
[0017]
As shown in FIG. 1A, the ideal shape of the molding surface 10c of the mold 10 according to the present embodiment is a diffractive surface in which a concavo-convex pattern is formed with a non-uniform density. The reversal shape of the diffractive surface of the zone plate.
As shown in FIG. 1B, the mold master 10 'is obtained by forming a workable layer 10b on a base material 10a. The base material 10a is made of, for example, a stainless steel metal, and the processed layer 10b is made of, for example, electroless plating.
[0018]
In the present embodiment, the mold 10 is manufactured by cutting the workpiece layer 10b of the mold prototype 10 '.
Next, in describing the cutting process of the mold master 10 ', the relationship between the tip of the cutting tool used for the cutting process and the shape of the processed surface will be described.
FIG. 2 is a diagram for explaining a difference in a processed surface depending on a tip diameter R of a cutting tool.
[0019]
2A is an ideal shape (cross section) of a certain machining surface, FIG. 2B is a shape (cross section) of a cutting surface cut with a cutting tool having a small tip diameter R, and FIG. It is the shape (cross section) of the cut surface cut by the cutting tool having a large tip diameter R. In addition, the cutting motion at the time of cutting the illustrated processing surface was the front and back direction of the paper surface, and the feeding motion was the left-right direction of the paper surface.
Comparing FIG. 2 (b) and FIG. 2 (c), when the tip diameter R is smaller (FIG. 2 (b)), the overall shape error (deviation from the ideal shape in FIG. 2 (a)). It can be seen that can be reduced.
[0020]
Here, in general, a diffractive surface of a diffractive optical element such as a zone plate needs a stepped portion whose height is to be suddenly changed and a smoothed portion which should be as smooth as possible in order to cause diffraction. Therefore, also on the molding surface 10c (see FIG. 1A) of the mold 10 according to the present embodiment, as shown in FIG. 2A, the stepped portion A whose height is to be suddenly changed and as smooth as possible. And a smooth part B to be required.
[0021]
Incidentally, in the zone plate, the diffracted light is not properly generated unless the stepped portion is sufficiently steep, and if the smooth portion is not sufficiently smoothed, scattered light is generated and causes flare.
In FIG. 2, when paying attention to the stepped portion A, a steep step can be formed when the tip end diameter R is smaller (FIG. 2B) than when the tip end diameter R is larger (FIG. 2C). It can be seen that it can be brought close to its ideal shape (FIG. 2A).
[0022]
However, paying attention to the smooth portion B, when the tip diameter R is larger (FIG. 2C) than when the bite tip diameter R is small (FIG. 2B), it can be closer to the smooth shape. It can be seen that it can be approximated to (FIG. 2 (a) B).
This is related to the fact that the height (surface roughness) of the tool flaw (tool mark) by cutting becomes smaller as the tip diameter R of the tool becomes larger.
[0023]
Incidentally, the height of the tool mark is f with respect to the feed pitch f of the cutting process.²/ 8R.
Therefore, it can be seen that a bit with a small tip diameter R is suitable for processing the stepped portion A, and a bit with a large tip diameter R is suitable for processing the smooth portion B.
Next, as shown in FIG. 1A, the ideal shape of the molding surface 10c of the mold 10 of the present embodiment is a region where the uneven pattern is formed with a non-uniform density and the formation density is relatively high. 10c-2 and a relatively low region 10c-1.
[0024]
Among these, the region 10c-2 having a higher formation density has a relatively large proportion of the stepped portion A (see FIG. 2), and the region 10c-1 having a lower formation density has a smooth portion B (see FIG. 2). ) Is relatively large.
[0025]
Therefore, in the cutting process of the present embodiment, for the region 10c-2 having a high formation density, the shape accuracy of the stepped portion A is prioritized and a cutting tool having a relatively small tip diameter R is used, and the region 10c-1 having a low formation density is used. As for, a cutting tool having a relatively large tip diameter R is used by giving priority to the shape accuracy of the smooth portion B.
In this way, the smoothed portion B and the stepped portion A can be brought close to their ideal shapes in a well-balanced manner for each of the high formation density region 10c-2 and the low region 01c-1.
[0026]
FIG. 3 is a configuration diagram of a cutting apparatus used for cutting according to the present embodiment. FIG. 4 is a perspective view showing a state around the cutting tool of the cutting apparatus.
Hereinafter, cylindrical coordinates (Z, X) in which the center of the work surface 10c ′ of the mold prototype 10 ′ held in the cutting apparatus is the origin and the Z coordinate is arranged in the normal direction of the work surface 10c ′. , Θ) (Z is a coordinate in the height direction, X is a coordinate in the radial direction, and θ is a coordinate in the circumferential direction).
[0027]
The cutting apparatus according to the present embodiment is basically the same as a conventional cutting apparatus (the one used for cutting a zone plate or a mold for forming a diffractive surface of a zone plate, a so-called ultraprecision cutting apparatus). Are the same.
That is, in the cutting apparatus, as shown in FIGS. 3 and 4, the spindle 15 that rotates the mold prototype 10 ′ in the θ direction around the Z axis, and the moving mechanism 14 z that moves the entire spindle 15 in the Z direction. A holding member 19 that holds the cutting tool 17 and a moving mechanism 14x that moves the holding member 19 in the X direction are provided so that the tip of the cutting tool 17 in use maintains an appropriate angle with respect to the processing surface 10c ′.
[0028]
In FIG. 4, reference numeral 15b is a holding member for holding the mold master 10 ', and reference numeral 15a is a spindle rotor.
Further, inside or outside of the cutting apparatus, a control unit 12 including a circuit for driving and controlling each unit such as a motor MZ in the moving mechanism 14z, a motor MX in the moving mechanism 14x, a motor (not shown) in the spindle 15 and the like. Is provided.
[0029]
In this cutting apparatus, the cutting motion is performed by the movement of the spindle 15 in the Z direction and the rotation of the mold master 10 ′ in the θ direction, and the feeding motion is performed by the movement of the cutting tool 17 in use in the X direction.
Since this cutting device is used for cutting a rotationally symmetric shape, it has a moving mechanism in the X and Z directions and a rotating mechanism in the θ direction, but other shapes (such as line symmetric shapes) are cut. Needless to say, it is not limited to this when used for processing (for example, it is composed of moving mechanisms in the X, Z, and Y directions orthogonal to each other).
[0030]
FIG. 5 is a diagram for explaining the bytes used in this embodiment.
Here, in this embodiment, a plurality of bytes (hereinafter referred to as two bytes 17a and 17b shown in FIG. 5) are used for processing one mold prototype 10 '.
The cutting edge portions of these cutting tools 17a and 17b are each made of a material (for example, single crystal diamond) suitable for cutting the workpiece layer 10b of the mold prototype 10 ', but the tip diameters thereof are different from each other. .
[0031]
Hereinafter, it is assumed that the tip diameter Ra of the cutting tool 17a and the tip diameter Rb of the cutting tool 17b are in a relationship of Ra> Rb.
Here, at the time of cutting, the X coordinate of the cutting tool 17 being used is changed by the feed movement, and the Z coordinate of the cutting tool 17 being used is changed by the cutting movement.
Conventionally, since the cutting tool is not exchanged during the cutting of the workpiece surface 10 c ′, the coordinates (Z, X) of the tip of the cutting tool 17 in use can be controlled entirely by the control unit 12 after the cutting process is started.
[0032]
However, in this embodiment, since the cutting tool is exchanged during cutting of the work surface 10c ′, even if each part of the cutting device is set to be the same, there is a possibility that the position of the cutting tool tip is shifted before and after the exchange. is there.
Therefore, as shown in FIGS. 3 and 4, the cutting apparatus according to the present embodiment is provided with a camera 16 for detecting the deviation.
[0033]
The camera 16 detects at least the deviation of the X coordinate between the tip when the cutting tool 17a is mounted and the tip when the cutting tool 17b is mounted.
For example, as shown in FIG. 4, the camera 16 is arranged on a straight line extending in a direction perpendicular to the X axis from the space near the tip of the tool 17 (the tool 17a or the tool 17b) in use. Catches.
[0034]
The camera 16 may be fixed either on the side of the cutting tool 17 in use (the holding member 19 side) or on the mold base 10 'side (on the spindle 15 side), but at least the feed movement and cutting. It is installed so that its tip does not deviate from the field of view of the camera 16 due to the movement.
In FIG. 4, reference numeral 16 b denotes a holding member (arm) that holds the camera 16 (described later).
[0035]
The camera 16 is driven and controlled by the control unit 12, and the control unit 12 displays an image acquired by the camera 16 on the monitor 13.
Incidentally, the Z coordinate of the tip of the bite 17 in use can be recognized without using the camera 16.
For example, the motor in the spindle 15 and the motor MZ in the moving mechanism 14z are driven, and the mold prototype 10 ′ is gradually brought closer to the tip of the cutting tool 17 (the cutting tool 17a or the cutting tool 17b). The Z coordinate of the tip of the byte 17 at the time when it starts to be generated may be regarded as “0”.
[0036]
FIG. 6 is a diagram illustrating the cutting method according to the present embodiment.
In FIG. 6, the dotted line is the shape (ideal shape) after the cutting of the work surface 10 c ′. As described above, the ideal shape has a dense uneven pattern from the center (X = 0) to the periphery (X = Xh).
In the present embodiment, for the range (X = 0 to Xp) on the center (X = 0) side on the processing surface 10c ′, the cutting tool 17a having a large tip diameter is used, and the peripheral side range (X = For Xp to Xh), a cutting tool 17b having a small tip diameter is used.
[0037]
The specific procedure of the cutting process of the present embodiment is as follows (note that a case of cutting from the center (X = 0) to the peripheral edge (X = Xh) will be described here).
First, the control unit 12 stores data indicating the ideal shape of the processing surface 10c '.
[0038]
Further, the holding member 19 holds the cutting tool 17a having a large tip diameter, and the moving mechanism 14x is set so that the tip of the cutting tool 17a becomes the center of the processing surface 10c '. The X coordinate of the tip of the byte 17a after setting is regarded as “0”.
Further, from a state where the distance between the mold prototype 10 ′ and the tip of the cutting tool 17a is sufficiently separated, the motor in the spindle 15 and the motor MZ in the moving mechanism 14z are driven, and the mold prototype 10 ′ gradually becomes the cutting tool. 17a.
[0039]
Then, the Z coordinate of the tip of the cutting tool 17a at the time when the shavings start to occur is regarded as “0”.
Thereafter, the coordinates (Z, X) of the tip of the cutting tool 17a are recognized by the control unit 12 based on the driving amounts of the motors MZ and MX.
Then, the control unit 12 controls the coordinates (Z, X) of the tip until X = Xp, and performs cutting so that the range of 0 <X <Xp in the processing surface 10c ′ becomes an ideal shape. .
[0040]
Next, the operator of the cutting apparatus removes the cutting tool 17a from the holding member 19 and replaces it with the cutting tool 17b.
Then, at the time of the replacement, the operator uses the X coordinate (here, Xp) of the tip of the byte 17a before replacement and the tip of the byte 17b after replacement from the image displayed on the monitor 13. The deviation from the X coordinate is recognized, and the coordinate of the tip of the byte 17b after replacement is made to coincide with Xp.
[0041]
In order to match, it is necessary to drive the moving mechanism 14x, but the driving may be performed directly by the operator or by the operator via the control unit 12.
Further, the motor in the spindle 15 and the motor MZ are driven from a state in which the distance between the mold master 10 'and the tip of the cutting tool 17b is sufficiently separated, and the mold master 10' is gradually brought closer to the cutting tool 17b.
[0042]
Then, the Z coordinate of the tip of the cutting tool 17b at the point in time when the shavings start to occur is regarded as “0”.
Thereafter, the coordinates (Z, X) of the tip of the cutting tool 17b are recognized by the control unit 12 based on the driving amounts of the motors MZ and MX.
Then, the control unit 12 controls the coordinates (Z, X) of the tip until X = Xh, and performs cutting so that the range of Xp <X <Xh in the processing surface 10c ′ becomes an ideal shape. .
[0043]
As a result of this cutting process, the work surface 10c ′ of the mold prototype 10 ′ becomes a molding surface 10c (see FIG. 1A) for transferring the diffractive surface of the zone plate (as described above, the cutting of this embodiment). Processing procedure).
As described above, in the cutting process of the present embodiment, a cutting tool with a small tip diameter (cutting tool 17b) is used for a region where the formation density of the concavo-convex pattern is high, and a cutting tool with a large tip diameter (cutting tool 17a) is used for the region where the formation density of the projection / recess pattern is low. use.
[0044]
When properly used in this way, in the completed mold 10 (see FIG. 1A), the smoothed portion B and the stepped portion of each of the region 10c-2 having a high uneven pattern formation density and the region 01c-1 having a low density are formed. A (see FIG. 2) approaches the ideal shape with a good balance.
Note that the camera 16 is used in the cutting apparatus according to the present embodiment. However, any sensor such as an optical sensor can be used as long as it can detect at least the displacement of the tips when the cutting tools 17a and 17b are mounted. May be used.
[0045]
Moreover, although two types of cutting tools are used in the cutting process of the present embodiment, three or more types of cutting tools may be used.
Moreover, you may comprise the cutting apparatus of this embodiment so that some or all of the operation | movement of an operator mentioned above may be automated.
[Second Embodiment]
A second embodiment of the present invention will be described with reference to FIG.
[0046]
In the present embodiment, a zone plate is produced. The present embodiment is characterized in that the mold 10 of the first embodiment is used for forming the diffractive surface of the zone plate.
FIG. 7 is a diagram illustrating a zone plate manufacturing process.
The zone plate material of the present embodiment may be glass, resin, or a combination thereof. In the following, a resin optical layer 22 is formed on a glass optical layer (glass substrate) 21, and The composite zone plate 20 (FIG. 7C) in which the surface of the optical layer 22 is a diffractive surface will be described as a representative.
[0047]
A glass substrate 21 made of optical glass is prepared, and an uncured resin 22 ′ to be used for the optical layer 22 is dropped on the glass substrate 21.
The mold 10 of the first embodiment is prepared, and the uncured product 22 ′ is spread over the entire glass substrate 21 by the molding surface 10 c (FIG. 7A).
By irradiating light (or heat) for curing the uncured product 22 ′, the uncured product 22 ′ is cured to form a resin optical layer 22 (FIG. 7B).
[0048]
The mold 10 is separated to complete the composite zone plate 20 (FIG. 7C).
The diffractive surface 20a of the composite zone plate 20 thus completed has an inverted shape of the molding surface 10c cut in the first embodiment, and each of the smooth portions of the high and low portions of the uneven pattern formation density The stepped part approaches the ideal shape with a good balance. Therefore, the performance of the composite zone plate 20 is high.
[0049]
The zone plate of the present embodiment has a resin optical layer 22 formed on the glass substrate 21. If the glass substrate 21 is peeled off at the end of the above procedure, the zone plate is made of resin alone. It can be.
In addition, the molding of the present embodiment is to mold the surface of the resin optical layer 22 on the diffractive surface 20a (resin molding method). By applying this, the surface of the glass optical layer is diffracted. It can also be formed into a glass (glass mold method).
[0050]
[Others]
In each of the above embodiments, the diffractive optical element to be manufactured is a zone plate, but a grating having a non-uniform concavo-convex pattern on the diffractive surface can also be used.
In the first embodiment and the second embodiment, a diffractive optical element is manufactured using a mold. The original pattern (base material) of the diffractive optical element is formed by the cutting method according to the first embodiment. Direct cutting may be performed.
[0051]
However, the material of the cutting tool tip to be used is not limited to the above-described material (for example, single crystal diamond) but is appropriately selected according to the original material.
The diffractive optical element fabricated in that case also exhibits good performance, similar to the diffractive optical element fabricated in the first and second embodiments.
In the second embodiment, a transmissive diffractive optical element is manufactured. However, if a reflective film such as a gold coat or a silver coat is formed on the surface of a molded product, a reflective diffractive optical element is manufactured. You can also By the way, the reflection type diffractive optical element does not matter the optical characteristics (transmittance, refractive index, dispersion characteristics, etc.) of the original resin (glass) or glass, so the range of materials that can be used is wide. Are known.
[0052]
【Example】
[First embodiment]
A first example (specific example of the first embodiment) of the present invention will be described.
FIG. 8 is a diagram for explaining the present embodiment.
In this example, a mold for molding a resinous zone plate was produced.
[0053]
A stainless steel Stabux was used as the mold base material 10a, and a Ni—P electroless plating layer was provided thereon as the work layer 10b. This was designated as a blank material (die mold) 10 '.
The ideal shape after processing (molding surface) of the processing surface 10c 'of the processing layer 10b was an inverted shape of the diffraction surface of the blazed zone plate.
[0054]
The grating depth h of this diffraction surface is 16 μm, the grating formation pitch p is 3 mm to 0.1 mm from the center to the periphery, and the number of gratings is 60 in total (FIG. 8 is exaggerated). ).
A cutting apparatus according to the first embodiment, a diamond tool having a tip radius of 2 μm, and a diamond tool having a tip radius of 8 μm were prepared.
[0055]
With this cutting device, the processing surface 10c 'of the processing layer 10b of the mold prototype 10' was cut.
In this cutting process, a diamond cutting tool having a tip radius of 8 μm was used in a region where the lattice pitch p was 1 mm or more, and a diamond cutting tool having a tip radius of 2 μm was used in a region where the lattice pitch p was 1 mm or less.
[0056]
The shape of the completed molding surface 10c is such that the uneven smooth portion is close to the ideal shape (smooth) in the central portion where the uneven pattern formation density is low, and the uneven step portion is ideal in the peripheral portion where the uneven pattern formation density is high. It was close to the shape (steep). That is, the smooth part and the step part of the high density area and the low density area of the concavo-convex pattern approached the ideal shape in a balanced manner.
[0057]
[Second Embodiment]
A second example (specific example of the second embodiment) of the present invention will be described.
FIG. 9 is a diagram for explaining the present embodiment.
In this example, a composite zone plate 20 made of glass and resin (see FIG. 9E) was produced by resin molding using the mold 10 of the first example.
[0058]
On the glass optical layer (glass substrate) 21 subjected to the silane coupling treatment, an uncured product 22 ′ of the urethane acrylate ultraviolet curable resin 22 was dropped (FIG. 9A). The glass substrate 21 had a diameter of 50 mm and a thickness of 2 mm.
The top and bottom of the glass substrate 21 is inverted to hang the uncured product 22 ′, and at the same time, the molding surface 10c of the mold 10 of the first embodiment gradually approaches the uncured product 22 ′ on the glass substrate 21 (FIG. 9). (B)) It is fixed when the distance from the glass substrate 21 reaches a predetermined distance (in this embodiment, the distance from the top of the lattice of the molding surface 10c of the mold 10 to the surface of the glass substrate 21 is 10 μm) ( FIG. 9 (c)).
[0059]
In this state, the uncured product 22 ′ was filled between the glass substrate 21 and the mold 10 without bubbles.
Further, the uncured material 22 ′ was cured by irradiating light (ultraviolet light) of a high-pressure mercury lamp from the side of the glass substrate 21 to form a resin optical layer 22 on the glass substrate 21 (FIG. 9D )).
[0060]
The mold 10 was separated to complete a composite zone plate 20 composed of a glass substrate 21 and an optical layer 22 (FIG. 9 (e)).
In this composite zone plate 20, the high density portion and the low density portion of the concavo-convex pattern functioned in a well-balanced manner, and the overall optical performance was high.
[0061]
In FIG. 9, the surface of the glass substrate 21 is a flat surface, but it may be a curved surface (spherical or aspherical).
In the present embodiment, if the glass substrate 21 is finally separated without subjecting the glass substrate 21 to the silane coupling treatment, a zone plate made of only a resin can be produced.
[0062]
In this embodiment, an ultraviolet curable resin is used as the material of the optical layer 22, but a visible light curable resin or the like can also be used. Furthermore, a molding method (injection molding) different from the present embodiment can be applied.
[Third embodiment]
A third example (another specific example of the second embodiment) of the present invention will be described.
[0063]
FIG. 10 is a diagram for explaining the present embodiment.
In this example, a glass zone plate 40 was produced by a glass mold using the mold 10 of the first embodiment. Hereinafter, the difference from the second embodiment will be mainly described.
In this embodiment, considering the high temperature durability of the glass mold, the material of the base material 10a and the layer to be processed 10b of the mold 10 is the same as the mold used in the second embodiment (the mold of the first embodiment). In addition, S45C (carbon steel) was used instead of Starbucks, and Ni-P electroless plating containing about 2% W (tungsten) was used. The cutting method of the layer to be processed 10b was the same as that in the first example.
[0064]
In the glass mold method, in order to form both surfaces simultaneously, a back surface mold 41 (lower mold) made of the same material as the mold 10 was also prepared. The molding surface 41a of the lower mold 41 was a flat surface.
A glass substrate 40 ′, which is a prototype of the glass zone plate 40, was prepared. As the glass substrate 40 ′, a low melting point glass (P-SK60, Sumida Optical Glass, diameter 60 mm, thickness 5 mm) whose surface 40 a ′ was polished to a flat surface was used.
[0065]
The glass substrate 40 ′ is placed on the lower mold 41, and the nitrogen (N₂) Heated up to 420 ° in the atmosphere (FIG. 10A).
In a nitrogen atmosphere with heating, the glass substrate 40 ′ is sandwiched between the lower mold 41 and the mold 10, and 30 kgf / cm²For 5 minutes (FIG. 10B).
The pressurization was stopped, the mold was cooled to a predetermined temperature, and then released, and the completed zone plate 40 was taken out (FIG. 10C).
[0066]
The glass zone plate 40 thus completed also functions in a well-balanced manner in each of the high and low portions of the uneven pattern formation density, and thus the overall optical performance is high.
The shape of the surface 40a 'of the glass substrate 40' is not limited to a flat surface, and may be a curved surface (spherical surface or aspherical surface).
[0067]
Further, if the molding surface 41a of the lower mold 41 is processed into a reversal shape of the diffractive surface, a zone plate having diffractive surfaces on both surfaces can be produced.
[0068]
【The invention's effect】
  As described above, according to the present invention, high optical performance can be obtained even if the uneven pattern formation density is non-uniform.TimesFolding optical element cutting method,as well asCutting method of diffractive optical element molding dieButRealize.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a mold according to a first embodiment. FIG. 1A is a completed mold (cross-sectional view and plan view) of the mold according to the present embodiment, and FIG. 1B is a blank material (mold original mold) before the mold is processed (cross-sectional view). It is.
FIG. 2 is a diagram for explaining a difference in a processed surface depending on a tip diameter R of a cutting tool.
FIG. 3 is a configuration diagram of a cutting apparatus used for cutting according to the first embodiment.
FIG. 4 is a perspective view showing a state around the cutting tool of the cutting apparatus according to the first embodiment.
FIG. 5 is a diagram illustrating bytes used in the first embodiment.
FIG. 6 is a diagram illustrating a cutting method according to the first embodiment.
FIG. 7 is a diagram illustrating a zone plate manufacturing process.
FIG. 8 is a diagram for explaining a first embodiment;
FIG. 9 is a diagram illustrating a second embodiment.
FIG. 10 is a diagram illustrating a third embodiment.
[Explanation of symbols]
10 Mold
10 'mold prototype
10a Base material
10b Work layer
10c, 41a Molded surface
10c 'Work surface
A Stepped part
B Smoothing part
11 Cutting device
12 Control unit
13 Monitor
14x, 14z moving mechanism
MZ, MX motor
15 spindle
15a Spindle rotor
15b, 19, 16b Holding member
16 Camera
17 Bytes in use
17a, 17b bytes
20 Composite zone plate
21 Glass substrate
22 Resinous optical layer
22 'uncured resin
20a Diffraction surface
40 glass zone plate
40 'glass substrate
40a ’surface
41 Lower mold

Claims (2)

A method for cutting a diffractive optical element, wherein the diffractive optical element has a diffractive surface having a concavo-convex pattern formed at a non-uniform density, and the diffractive optical element is cut.
A first cutting step of processing the first region of the diffractive surface with a first bite mounted on a cutting device;
A second area of the diffractive surface, which is mounted on the cutting device and has a tip diameter larger than that of the first area, is used to process a second area of the diffractive surface having a lower density of the concavo-convex pattern than the first area. A second cutting process;
A tool exchange for exchanging a tool used for processing the diffraction surface between the first tool and the second tool between the first cutting process and the second cutting process. Including a process,
In the byte exchange process,
Based on the output of the sensor that detects the deviation between the tip position of the tool before replacement and the tip position of the tool after replacement, the tip position of the tool at the start of machining in the cutting process performed after replacement and the cutting method of the diffractive optical element, characterized in that to match the bytes of the tip position in the machining end point of cracking cutting machining process. A method for cutting a diffractive optical element molding die, which cuts the molding surface of a diffractive optical element molding die having a molding surface on which a concavo-convex pattern is formed with a non-uniform density,
A first cutting step of machining a first region of the molding surface with a first bite mounted on a cutting device;
The second region, which is mounted on the cutting device and has a tip diameter larger than that of the first bite, is used to machine a second region of the molding surface in which the density of the uneven pattern is lower than that of the first region. A second cutting process;
Byte exchange for exchanging a bit used for processing the molding surface between the first bit and the second bit between the first cutting step and the second cutting step. Including a process,
In the byte exchange process,
Based on the output of the sensor that detects the deviation between the tip position of the tool before replacement and the tip position of the tool after replacement, the tip position of the tool at the start of machining in the cutting process performed after replacement and the diffractive optical element molding die cutting methods, wherein the match we have a byte tip position in the processing end of the cutting process a.

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