JP2003004925A - Optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical element in which functions as a beam splitter and a light converging function are integrated and which can be easily mass-produced at a low cost. SOLUTION: The optical element diffracts an incident monochromatic beam 13 to branch into a plurality of diffracted monochromatic beams 14A to 14E and condensing a plurality of the branched diffracted monochromatic beams 14A to 14E to the respective beam spot positions 15A to 15E different from one another, with the different beam spot positions 15A to 15E disposed in a specified arrangement. In the optical element, a plurality of binary zone plates 21A to 21E to diffract the incident monochromatic beam 13 to converge to the specified beam spot positions 15A to 15E are disposed together as one body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element for diffracting light, and more particularly to a beam splitter function for splitting an incident beam into a plurality of outgoing beams and a condensing function for focusing / focusing the split outgoing beams. And an optical element having both.

[0002]

2. Description of the Related Art Conventionally, magnetic cards are prepaid cards,
It is widely used as a credit card, cash card, etc., and contributes to a so-called cashless society that does not directly send and receive cash. However, in the magnetic card, since the recording medium is the magnetic recording layer, it is possible to read the recorded contents relatively easily, and as a result, it is easy to forge the magnetic card.
A large number of telephone cards and credit cards are forged and used illegally, which has become a social problem.

In order to cope with such forgery and unauthorized use of various cards, a magnetic card adopting a complicated recording method that is difficult to read illegally is used instead of the conventional simple magnetic recording type magnetic card. IC cards have been proposed,
Adopting these cards has a problem of high cost.

On the other hand, as another recording method which is difficult to counterfeit or illegally read, an optical recording method using a diffraction grating or a hologram is disclosed in, for example, JP-A-3-71383 and JP-A-5-73738. Proposed and disclosed in. In the conventional optical recording method disclosed in the above publication, a method for detecting / determining whether or not the reflection intensity of light by a hologram recorded on a card is a predetermined value or a predetermined value or more, a diffraction grating Since this is a method of detecting a plurality of different optical paths of reflected light reflected by a hologram, it is useful for identifying whether the card is a genuine product or a counterfeit product.

However, it is not suitable for recording, for example, the remaining amount of money rewritten and recorded on a prepaid card, the personal identification number or the card number recorded on a cash card, and such information is disclosed in the above publication. If you try to record using a conventional optical recording method, it is necessary to arrange a huge number of holograms, cost is also required to manufacture the card, on the other hand, if you try to reproduce these recorded information with high accuracy, The reader becomes very complicated and very expensive, which makes it difficult to implement.

In view of the above, the present applicant has previously proposed Japanese Patent Laid-Open Nos. 10-143603 and 10-171334.
In Japanese Patent Publication, it is suitable for recording complicated information such as the amount of money recorded on a prepaid card, a personal identification number and a card number in a cash card, and proposes a low-cost optical card and a reading device for this optical card. is doing.

FIG. 11 is a perspective structural view showing a monochromatic light generating device using the optical element of the first conventional example, and shows the monochromatic light generating device used in the above-mentioned reading device. In the monochromatic light generator 40, a laser diode (LD), a light emitting diode (LED), or the like is used as a light source, and monochromatic light 46a emitted from them is condensed by a refraction lens 42, and the condensed monochromatic light is generated. The irradiation range of 46b is limited by the pinhole 43, and the monochromatic light 46c thus obtained is branched by the beam splitter 44 into a plurality of (for example, seven) beams 45 for reproduction. In such a monochromatic light generator 40, the refraction lens 42,
The beam splitter 44 and the pinhole 43 are precisely assembled and arranged to obtain the optical element 40A.
Therefore, there is a problem that a great deal of cost is required because extremely high accuracy is required in the assembly adjustment in order to prevent tilting.

On the other hand, the applicant of the present invention has disclosed that
In Japanese Patent No. 66074, an improved optical element is proposed. Hereinafter, a second conventional example will be described. Figure 12
It is a cross-sectional block diagram which shows the optical element of a 2nd prior art example. In the optical element 50 of the second conventional example improved from the first conventional example,
Refraction lens 52, beam splitter 54, pinhole 5
3 is formed integrally.

FIG. 13 is a view for explaining the manufacturing process of the optical element of the second conventional example. Second conventional optical element 5
0 is manufactured as follows. First, the stamper 57 is created. To this end, a diffraction grating-shaped concave-convex pattern serving as the beam splitter 54 is generated so that one incident beam is branched into an arbitrary plurality of outgoing beams. This concave-convex pattern is formed on a silicon master by an electron beam drawing apparatus, and the stamper 57 is formed by replicating the concave-convex pattern from the silicon master. Further, a refraction lens mold 55 for forming the refraction lens 52 is separately prepared.

Next, the stamper 57 and the refraction lens mold 55 are attached to the molding machine in a predetermined arrangement, and the resin 58 of the lens material is injected through the injection hole 56 to integrally form the refraction lens 52 and the beam splitter 54. To do. If necessary, a pinhole 53 is formed by forming a metal thin film on the surface of the beam splitter 54 on the side where the beam is emitted by using a sputtering method or the like, and the optical element 50 of the second conventional example is obtained. .

[0011]

By the way, since the optical element 50 of the second conventional example manufactured by such a manufacturing method is an integrated optical element 50, it is the same as the optical element 40A of the first conventional example. Assembling and adjusting accuracy is not required, which leads to cost reduction when manufacturing the device. However, since the stamper 57 for the beam splitter 54 and the refraction lens mold 55 for the refraction lens 52 are separately provided, such an integrated optical element 50 has a cost of forming both dies, and a molding machine for both dies. There is a problem in that adjustment accuracy is required to be attached to and the cost is accordingly increased.

In view of the above problems, it is therefore an object of the present invention to provide an optical element having a beam splitter function and a light converging function integrated, which can be manufactured inexpensively and easily in large quantities. .

[0013]

As a means for achieving the above object, the first invention is to diffract one incident monochromatic light beam 13 which is incident, and to diffract a plurality of (5) diffracted monochromatic light beams 14A. , 14B, 14C, 14D, 14E,
The plurality of branched diffractive monochromatic light beams 14A, 14
B, 14C, 14D, and 14E are focused on different beam spot positions 15A, 15B, 15C, 15D, and 15E, and the different beam spot positions 15A and 15E are collected.
In an optical element in which B, 15C, 15D, and 15E are arranged in a predetermined array, the incident monochromatic light beam 13 is diffracted and predetermined beam spot positions 15A, 15B, and 15 are formed.
Binary zone plates 21A, 21B, 21C, 21D, 21E for focusing on C, 15D, 15E
The optical element 21 is characterized in that a plurality of (5) are arranged integrally.

A second invention is characterized in that, in the first invention, a pinhole for limiting the shape of the incident monochromatic light beam is arranged on the binary zone plate.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will now be described with reference to the drawings by way of preferred embodiments.

<Example> First, a binary zone plate used in an example of the optical element of the present invention will be described. FIG. 1 is a sectional shape diagram for explaining a binary zone plate applied to the optical element of the present invention.
1A shows a refracting lens, FIG. 1B shows a Fresnel lens, and FIG. 1C shows a binary zone plate. The cross-sectional shape diagram shows the cross section of the central portion.

Refractive lens 10 shown in FIG. 1 (a).
Has the convex lens shape 1 and includes three equal phase surfaces 2a, 2b, 2c. The Fresnel lens 3 shown in FIG. 1B has a blazed annular lens shape 1a, 1b obtained by optimizing the convex lens shape 1 of the refractive lens 10 by removing the equal phase surfaces 2a, 2b, 2c. 1c and 1d.

FIG. 1 (c) shows an annular lens shape 1
Binary zone obtained by digitally approximating a, 1b, 1c, 1d by step shapes 1a ', 1b', 1c ', 1d' of phase level M, respectively. Plate 4 (Bina
ry Zone Plate: hereinafter also simply referred to as BZP). Like the Fresnel lens 3, the BZP 4 has a light collecting function (that is,
It has a function of forming an image of an incident beam at a predetermined focal length). Here, M = 4, that is, the step difference is approximated by three steps, but the value of M (phase level) is related to the diffraction / collection efficiency as will be described later, but can be set arbitrarily. is there.

Next, a method of forming BZP4 will be described. FIG. 2 is a manufacturing process diagram for manufacturing a binary zone plate. First, as shown in FIG. 2A, a photomask 7 having a pattern showing a flat portion of each step of the BZP step shape is prepared in advance. To this end, a predetermined portion of the photoresist formed on the transparent substrate is exposed to light by an electron beam drawing device to produce a photomask composed of a light shielding portion 7a and a transparent portion 7b. This photomask 7 is arranged on a silicon master 5 coated with a photoresist 6 having a predetermined thickness, and, for example, UV light 8 is irradiated to expose the portion of the photoresist 6 corresponding to the transparent portion 7b of the photomask 7. Thus, the exposed portion 6b is formed, and the other portions are left as the non-exposed portion 6a.

Next, as shown in FIG. 2B, the photoresist 6 is developed with a predetermined developing solution to remove the exposed portion 6b and leave the non-exposed portion 6a on the silicon master 5. Next, as shown in FIG. 2C, the silicon master 5 is etched with a predetermined etching solution using the non-exposed portion 6a of the photoresist 6 as a mask to form a recess 5b having a pattern with a predetermined depth. After that, the photoresist 6 is removed.
As a result, the first staircase shape having a predetermined depth is formed on the silicon master 5.

By repeating the above steps according to each stage, BZP is formed on the silicon master 5. A stamper is formed from this silicon master 5 by duplication, and a transparent resin is molded by an injection molding method using this stamper to obtain BZP. When M = 2 ^N level, N
BZP can be formed on the silicon master by repeating exposure, development and etching N times using a single photomask. This technique is described, for example, in Document A. O
KAZAKI et al. : JOEL Vol. 9 S
upp. Optics for Information
on Infrastructure (1998) pp.
356-358 and the like.

By the way, the theoretical value of the diffraction efficiency of BZP is
95.5% when M = 8, 98.7% when M = 16,
When M = 32, it is 99.7%. According to the above manufacturing method, BZP can be formed with three masks when forming BZP with M = 8 and with four masks when M = 16. A highly efficient BZP can be manufactured. Theoretically, the larger the value of M,
The diffraction efficiency approaches 100% without limit, but in this case, the etching depth per staircase becomes shallow, and the etching depth accuracy reaches its limit, making etching impossible. Considering the diffraction efficiency, the etching depth accuracy, and the cost, M = 8, 16, and 32 is particularly preferable, and the condensing characteristics comparable to the refractive lens, that is, the diffraction efficiency is obtained.

There are two types of BZP described above, on-axis BZP and off-axis BZP. FIG. 3 is a top view showing an annular shape of the binary zone plate. FIG. 3A shows the on-axis BZP11, and FIG. 3B shows the off-axis BZP12.

In the on-axis BZP11, the center 11kc of the opening (the center of the geometric shape) and the center 11c of the BZP coincide with each other. In the off-axis BZP12, the center 12kc of the opening does not coincide with the center 12c of the BZP. Concentric circles or arcs are called ring zones. The shape of the BZP, that is, the ring shape, the ring width, and the ring spacing is determined by the positional relationship between the BZP and the position of the beam spot formed by the BZP (beam spot position). Although FIG. 3 shows the case where the opening shape is a rectangle, the opening shape can be an arbitrary opening shape such as a circular shape or an oval shape.

Next, the diffraction direction of the incident light of BZP will be described. FIG. 4 is a perspective view for explaining the diffraction direction of incident light on the binary zone plate. FIG. 4A shows the diffraction direction of the incident light of the on-axis BZP, and FIG. 4B shows the diffraction direction of the incident light of the off-axis BZP. FIG. 4 (c) shows the spatial coordinate axes common to FIG. 4 (a) and FIG. 4 (b).

The incident surface (surface) of the BZPs 11 and 12 is x-
The incident beam 13 (incident light) incident on any of the BZPs 11 and 12 is parallel to the y-plane and parallel to the z-axis. In the case of the on-axis BZP 11, the diffracted beam 14 parallel to the z axis is emitted. Beam spot position coordinates on the z axis (focus position coordinates at which the diffracted beam 14 focuses) (0, 0, z
By specifying _f ), the shape of the on-axis BZP is determined.

On the other hand, in the case of off-axis BZP12, 3
Beam spot position coordinates (x _f , y _f ,
The shape of the off-axis BZP is determined by specifying z _f ). When the incident beam 13, which is a monochromatic light beam, is incident vertically on the surface of the off-axis BZP, the diffraction angle θ determined by the shape of the BZP (the size of the angle can be set arbitrarily).
The incident beam 13 is diffracted by and is emitted as a diffracted beam 14 '. Here, as described above, the on-axis BZ
Since P11 corresponds to the case where the beam spot position coordinates are x = 0, y = 0 in the off-axis BZP12, hereinafter, the on-axis BZP11 and the off-axis BZP12 are collectively referred to simply as BZP, and
The ZP is described as diffracting the incident beam 13 in an arbitrary direction.

Next, examples of the optical element of the present invention will be described. FIG. 5 is a configuration diagram showing an embodiment of the optical element of the present invention. FIG. 5A shows the relationship among the incident beam 13, the optical element 21, the diffracted beam and the focal point of the beam spot, and FIG. 5B shows a top view of the optical element 21. ing. The optical element 21 of the embodiment has five B
It is composed of ZPs 21A, 21B, 21C, 21D and 21E. A circular BZP21E with a diameter of 1000 μm in the center
Is arranged around it, with a central angle of 90 ° and an outer diameter of 35
An annular fan-shaped BZP with a diameter of 00 μm and an inner diameter of 1000 μm
21A, 21B, 21C and 21D are arranged.

Optical element 2 in x-y-z space coordinates.
The center coordinate of 1 is (0, 0, 0), the incident beam 13 is incident parallel to the z-axis, and the surface of the optical element 21 (the surface on which the incident beam 13 is incident) is parallel to the xy plane. The incident beam 13 is formed by each BZP 21A, 21B, 21C, 21D, 2
1E is incident on its center coordinates by design (actually, it is incident on the entire surface), and is diffracted to obtain a diffracted beam 14 respectively.
Emitted as A, 14B, 14C, 14D, 14E,
Beam spot focal position 15A, 15B, 15C, 15
Focus on D and 15E.

In the BZP21A, the incident beam 13
Is incident on the position (center coordinates) of x = −875 μm and y = 875 μm parallel to the z axis, and the diffracted beam 14A is diffracted by −1.59 degrees in the x direction and 0 degrees in the y direction, and x = −27.
The light is focused on the beam spot focal position 15A at a position of 8.6 μm, y = 0 μm, and z = 10000 μm. In the BZP21B, the incident beam 13 is incident on the position (center coordinate) of x = −875 μm and y = −875 μm parallel to the z axis, and the diffracted beam 14B is − in the x direction.
3.18 degree, 0 degree in the y direction, x = −557.1
The light is focused on the beam spot focal position 15B at the positions of μm, y = 0 μm, and z = 10000 μm.

In the BZP21C, the incident beam 13
Is incident on a position (center coordinate) of x = 875 μm and y = −875 μm parallel to the z-axis, and the diffracted beam 14C is diffracted by 1.59 ° in the x direction and 0 ° in the y direction, and x = 278.6.
The light is focused on the beam spot focal position 15C at the positions of μm, y = 0 μm, and z = 10000 μm. B
In the ZP21D, the incident beam 13 is incident on the position (center coordinate) of x = 875 μm and y = 875 μm parallel to the z axis, and the diffracted beam 14D is 3.18 in the x direction.
Degree, 0 degree in the y direction, x = 557.1 μm, y =
The light is focused on the beam spot focal position 15D at a position of 0 μm and z = 10000 μm.

In the BZP21E, the incident beam 13
Is incident on the position (center coordinate) of x = 0 μm and y = 0 μm parallel to the z-axis, and the diffracted beam 14E is 0 ° in the x-direction, y
Direction is diffracted by 0 degree, x = 0 μm, y = 0 μm, z = 1
Beam spot focal position 15 at 0000 μm position
Focus on E. These conditions are shown in Table 1 below.
Are summarized in.

[0033]

[Table 1]

Applying the above conditions to the following, each BZP2
Concavo-convex pattern of 1A, 21B, 21C, 21D, 21E
Calculate φ (x, y) that represents Each BZP21A, 21
The pattern φ (x, y) of B, 21C, 21D, 21E is
With the center of the optical element 21 as the origin (0,0,0),
Focal spot focus positions 15A, 15B, 15C, 15
D and 15E are position coordinates (x_f, Y_f, Z _f)
And each BZP 21A, 21B, 21C, 21D, 21
The center coordinate of E is (x_b, Y_b, 0) φ (x, y) = Mod (((xx_f+ X_b)²+ (Y-y_f+ Y_b)²+ Z_f ²)^1/2, Λ)                                                           Formula (1) Can be calculated by However, mod (a, b) is a for b
The remainder divided by λ is the monochromatic light beam incident on the optical element 21.
Represents the wavelength of the incident beam 13 which is

Each BZP 21A, 21B, 21C, 21
For D and 21E, the coordinates of the beam spot focal positions 15A, 15B, 15C, 15D and 15E of the BZPs and the BZPs 21A, 21B, 21C, 21D and 21E described above.
From the center coordinate of each BZP 21A, 21B, 21C, 2
Equation (1) is calculated within the area of 1D and 21E. The obtained φ (x, y) is rounded to the M level (phase level) to generate an M level uneven pattern.

The pattern of the optical element 21 is formed on the silicon master by using the method shown in FIG. That is, a photomask having a mask pattern corresponding to the pattern of the optical element 21 is formed by the electron beam drawing device. Place a photomask on the silicon master coated with resist, expose from the photomask, develop,
Optical element 2 is obtained by repeating etching and resist removal.
The pattern 1 is formed on the silicon master. In this embodiment, each BZP 21A, 21B, 21C, 21D, 21E
The pattern is integrally formed so that the level difference of M = 16 is 0.1 μm per step.

Each BZP 21A, 21B, 21C, 21
Even if the concavo-convex patterns of D and 21E (ring width, ring gap) are different, a mask pattern can be formed at once by the electron beam drawing apparatus, so that a plurality of BZPs having different ring widths and gaps can be formed at one time. However, the cost is not different from the case of forming one BZP.

FIG. 7 is a top view showing an optical element pattern of an embodiment of the present invention formed on a silicon master. Figure 7
As shown in FIG. 2, a plurality of optical element patterns 16 can be simultaneously formed on the silicon master 20 with one set of mask patterns. Therefore, by duplicating the same, the same optical elements can be mass-produced.

That is, the optical element pattern 16 is duplicated from the silicon master 16 to form a stamper, and the optical element pattern 16 is resin-molded from the stamper by an injection molding method to duplicate the optical element. Alternatively, the optical element may be duplicated by resin molding directly from the silicon master by the 2P molding method without producing the stamper. The concavo-convex pattern, which is the pattern 16 of the optical element, is reversed when the replication is performed once. Be careful because it is different.

Next, an example of arrangement of BZPs in the optical elements of the present embodiment and the modification will be described. FIG. 6 is a top view showing an embodiment of the optical element of the present invention and a modification thereof. As described above, the optical element 21 of the embodiment shown in FIG. 6A has four annular fan-shaped BZPs 21A, 2 having a central angle of 90 °.
1B, 21C, 21D, and a circular BZP 21E arranged inside them, and are integrated into a circular shape as a whole. It has a configuration of five BZPs, and has a beam splitter function of branching the incident beam into five beams and a condensing function. Here, BZP21E is set as an on-axis BZP. An optical element 22 which is a first modification of the embodiment shown in FIG. 6B is composed of four fan-shaped BZPs 22A, 22B, 22C and 22D having a central angle of 90 °. Since each BZP has a different beam spot focal position, the optical element 22 has a beam splitter function of splitting an incident beam into four beams and a light condensing function. As described above, when the areas of the BZPs are all equal, if the center of the incident beam is adjusted to the center of the optical element 22, the light amounts at the four beam spot focal points can be made equal. It is also possible to change the area of each fan-shaped BZP, and when the area changes, the light quantity ratio at the beam spot focal position also changes.

An optical element 23, which is a second modification of the embodiment shown in FIG. 6C, has a central angle of 90 ° arranged inside.
4 fan-shaped BZPs 23E, 23F, 23G, 2
3H and four annular fan-shaped BZPs 23A, 23B, 23C having a central angle of 90 ° arranged outside them.
23D. Since each BZP has a different beam spot focus position, the optical element 23 has a beam splitter function of splitting an incident beam into eight beams and a condensing function.

An optical element 24, which is a third modification of the embodiment shown in FIG. 6D, is a circular BZP arranged in the center.
24I and four annular fan-shaped BZPs 24E, 24F, 24G, and 24H that are arranged outside and have a central angle of 90 °
And four annular fan-shaped BZPs 24A, 24B, 24C, 24 arranged outside these and having a central angle of 90 °.
And D. Since each BZP has a different beam spot focal position, the optical element 24 has a beam splitter function of splitting an incident beam into nine beams and a condensing function.

An optical element 25, which is a fourth modification of the embodiment shown in FIG. 6E, has an oval shape (elliptical shape) as a whole.
The four BZPs 25A, 25B, 25C, 25 having an elliptical fan shape with a central angle of 90 °
D. Since the beam spot focal position of each BZP is different, the optical element 25 changes the incident beam to 4
It has a beam splitter function of branching into a book and a condensing function. When the shape of the incident beam incident on the optical element 25 is an ellipse, there is no light quantity loss and the generation of stray light can be suppressed to a minimum. The examples of different BZP arrangements have been described above, but the combination arrangement of BZPs in the optical element can be arbitrary. These optical elements 22,
Similar to the optical element 21 of the embodiment, all of 23, 24, and 25 can simultaneously produce a plurality of optical element patterns on a silicon master with one set of mask patterns. Mass production of devices is easy.

In the hybrid type optical element in which different BZPs are assembled as in this embodiment, the incident beam diameter is substantially equal to or equal to that of the region where the optical element pattern (concavo-convex pattern) exists. When the beam diameter is larger, the incident beam is incident on a portion of the optical element where the concavo-convex pattern does not exist, so that extra transmitted light that is not diffracted at that portion is generated. In order to prevent such transmitted light, it is preferable to form a pinhole. Further, since the shape of the beam that has passed through the pinhole changes according to the shape of the pinhole, the beam spot can also be formed into a desired shape by changing the shape of the pinhole.

FIG. 8 is a manufacturing process diagram for explaining a method of forming a pinhole in the embodiment of the optical element of the present invention. As shown in FIG. 8A, a metal thin film 18 is formed on a base 17a having a concavo-convex portion (BZP) 17b of a predetermined shape obtained by resin molding, by using a sputtering method or a vacuum evaporation method. Everything, uneven part 17b
Is irradiated with a high-power laser beam to remove the metal thin film 18 in a predetermined area on the uneven portion 17b.

As shown in FIG. 8 (b), by the above procedure, the uneven portion 17b is formed on the base 17a, and the pinhole 18a is formed on the upper portion of the uneven portion 17b. The optical element 17 covered with the metal thin film 18 for light shielding is obtained. When a monochromatic light beam is incident on the optical element 17, excess light can be blocked by the metal thin film 18, and the monochromatic light beam transmits only the region (pinhole 18a) where the metal thin film 18 is removed. Low cost materials such as aluminum and brass are sufficient as materials for the metal thin film.

The pinhole 18a can be easily formed into an arbitrary shape such as a circular shape or an oval shape, and the beam spot shape of the beam incident on the optical element changes depending on the pinhole shape. As another method for forming pinholes, ink is applied only to areas where monochromatic light beams are not desired to be transmitted, and ink is not applied to areas where monochromatic light beams are not desired to be allowed to form pinholes by ink. You can also The screen printing method is particularly suitable for the ink application method. It is preferable that the material and color of the ink have high light opacity, and the light blocking effect similar to that of the metal thin film can be obtained by the ink having high light opacity.
The pinhole forming method does not limit the use of other pinhole forming methods. Although the pinhole 18a is formed on the concavo-convex portion 17b in the above description, the pinhole 18a can be arranged on the opposite side, and the same effect can be obtained.

Another modified example (including a pinhole) of the embodiment of the optical element will be described below. FIG. 9 is a top view showing another modification of the embodiment of the optical element of the present invention.
The optical element 26 shown in FIG. 9A has four rectangular BZs.
P26A, 26B, 26C, and 26D are integrally formed in a rectangular shape as a whole, and have a 4-beam splitter function and a light condensing function.

Optical element 26 'shown in FIG. 9B.
Is the BZP 26A, 26B, 26 in the optical element 26.
A fan-shaped BZP 26 having pinholes 28 formed in C and 26D and having a central angle of 90 ° in the area irradiated with the incident beam
A ', 26B', 26C ', 26D'. As described above, it is highly versatile to form a pinhole having an arbitrary shape in accordance with a desired incident beam shape.

The optical element 27 shown in (c) of FIG.
A circular BZP 27E has a shape in which a circular BZP 27E is arranged in the center of the optical element 26, and a rectangular BZP 27A, 2 with a part cut away.
7B, 27C, 27D and a circular BZP 27E, and has a rectangular shape as a whole. Also in this case, it is possible to form a pinhole having an arbitrary shape in accordance with a desired beam spot shape. FIG. 9D shows an optical element 27 ′ obtained by forming the pinhole 29 in the optical element 27. These optical elements 26, 2
6 ', 27 and 27' are all optical elements 21 of the embodiment.
Similarly to the above, since a plurality of optical element patterns can be simultaneously produced on a silicon master by one set of mask patterns, the same optical element can be easily mass-produced by duplicating this pattern.

Next, an example will be described in which reproduction is preferably performed using the optical element of this embodiment (or its modification). FIG. 10 is a diagram showing an example of reproducing CGH recorded on an optical card by using a modification of the embodiment of the optical element of the present invention. In FIG. 10, the optical recording medium 30 is an optical card, and the information recording portion is a CGH (Computer Genera).
ted Hologram) 36, which is a plurality of hologram interference fringes generated by calculation based on two-dimensional image data. When a monochromatic light beam is incident on the CGH 36, the original two-dimensional image data can be recognized from the diffracted light.

The case is shown in which 10 CGHs 36 are arranged in the vertical direction and 4 CGHs are arranged in the horizontal direction on the recording medium 30. Each CGH 36 represents one data, and as a whole, For example, when the optical recording medium 30 is used as a prepaid card, it represents a certain amount of money.

A monochromatic light beam 33 is emitted from the monochromatic light source 31. Optical element 3 on which monochromatic light beam 33 is incident
2 is composed of, for example, four BZPs as shown in the modified example of the present embodiment, and each BZP has four different beam spot focal positions 35A, 35.
B, 35C, and 35D, which have a 4-beam spirit function and a light condensing function. Since the beam spot focal positions 35A, 35B, 35C, 35D are set so as to be on the four CGHs 36 arranged in a row and arranged at a predetermined interval, the monochromatic light beam 33 is emitted from the optical element 3.
When incident on 2, the four diffracted beams 34A, 34B, 3
4C and 34D are emitted and are condensed on each of the one row of CGH 36. The reflected light obtained from the CGH 36 is detected by a detector (not shown), and the information recorded in the CGH 36 is reproduced. By sequentially applying this to the CGH 36 for each column, the recorded information on the optical recording medium 30 can be easily reproduced.

[0054]

As described above, according to the first and second aspects of the present invention, the optical element of the present invention is a binary optical element for diffracting an incident monochromatic light beam and condensing it at a predetermined beam spot position. By arranging a plurality of zone plates integrally, there is an effect that it is possible to provide an optical element that integrates a beam splitter function and a light converging function, which can be mass-produced inexpensively and easily. .

[Brief description of drawings]

1A and 1B are cross-sectional shape diagrams for explaining a binary zone plate applied to an optical element of the present invention. FIG. 1A shows a refraction lens, and FIG. 1B shows a Fresnel lens. 1 (c) shows a binary zone plate, respectively.

FIG. 2 is a manufacturing process diagram for manufacturing a binary zone plate.

FIG. 3 is a top view showing an annular shape of a binary zone plate.

FIG. 4 is a perspective view for explaining a diffraction direction of incident light on a binary zone plate.

FIG. 5 is a configuration diagram showing an embodiment of an optical element of the present invention.

FIG. 6 is a top view showing an embodiment of the optical element of the present invention and a modification thereof.

FIG. 7 is a top view showing a pattern of an optical element formed on a silicon master according to an embodiment of the present invention.

FIG. 8 is a manufacturing process diagram for explaining a method of forming a pinhole in the example of the optical element of the present invention.

FIG. 9 is a top view showing another modification of the embodiment of the optical element of the present invention.

FIG. 10 is a diagram showing an example of reproducing CGH recorded in an optical card by using a modified example of the embodiment of the optical element of the present invention.

FIG. 11 is a perspective configuration diagram showing a monochromatic light generating device using an optical element of a first conventional example.

FIG. 12 is a sectional configuration diagram showing an optical element of a second conventional example.

FIG. 13 is a diagram for explaining a manufacturing process of the optical element of the second conventional example.

[Explanation of symbols]

1 ... Convex lens shape, 1a, 1b, 1c, 1d ... Orbicular lens shape, 1a ', 1b', 1c ', 1d' ... Step shape, 2a, 2b, 2c ... Equal phase surface, 3 ... Fresnel lens, 4 … Binary Zone Plate (BZP), 5…
Silicon master disc, 5b ... Recessed portion, 6 ... Photoresist, 6a
... non-exposed area, 6b ... exposed area, 7 ... photomask, 7a ...
Light-shielding portion, 7b ... Transparent portion, 10 ... Refractive lens, 11 ... On-axis BZP, 12 ... Off-axis BZP, 13 ... Incident beam, 14, 14 '... Diffraction beam, 15 ... Beam spot, 16 ... (of optical element) pattern, 17 ... Optical element, 17a ... Base, 17b ... Concavo-convex part (BZP), 18
… Metal thin film (pinhole), 19… Laser beam, 2
0 ... Silicon master 21,22,23,24,25,2
6, 27 ... Optical element, 28, 29 ... Pinhole, 30 ...
Optical recording medium, 31 ... Monochromatic light source, 32 ... Optical element, 33 ...
Monochromatic light (incident) beam, 34A, 34B, 34C, 34
D ... Diffracted beam, 35A, 35B, 35C, 35D ... Beam spot, 36 ... CGH, 40 ... Monochromatic light generator,
40A ... Optical element, 41 ... Laser diode (LD),
42 ... Refractive lens, 43 ... Pinhole, 44 ... Beam splitter, 45 ... Beam, 46a, 46b, 46c ... Monochromatic light, 50 ... Optical element, 52 ... Refractive lens, 53 ... Pinhole, 54 ... Beam splitter, 55 ... Refractive lens mold, 56 ... Injection hole, 57 ... Stamper, 58 ... Resin.

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2C005 HA01 HA17 HA19 JB09 KA49                       LA06 LA19 LA31                 2H042 AA14 AA26 AA29                 2H049 AA04 AA14 AA37 AA40 AA43                       AA44 AA50 AA55 AA60 AA63                       AA64 AA65                 2K008 AA08 AA13 CC01 CC03 FF27                       HH06 HH25

Claims (2)

[Claims] 1. A single incident monochromatic light beam that is incident is diffracted and branched into a plurality of diffracted monochromatic light beams, and the plurality of branched diffracted monochromatic light beams are condensed at different beam spot positions, respectively. In the optical element in which the different beam spot positions are arranged in a predetermined array, a plurality of binary zone plates for diffracting the incident monochromatic light beam and converging the incident monochromatic light beam at the predetermined beam spot position are integrally formed. An optical element characterized by being arranged. 2. The optical element according to claim 1, wherein a pinhole for limiting the shape of the incident monochromatic light beam is arranged on the binary zone plate.