JPS6224218A - Manufacture of hologram disk - Google Patents

Abstract

PURPOSE:To place with high accuracy a hologram on a disk by utilizing Moire fringes, by changing by a small quantity a focal distance of the hologram and a reference hologram which are placed on the disk. CONSTITUTION:One hologram is superposed at a position where the center of a zone plate is shifted by a small quantity. In such a case, the position of a hologram 2 is adjusted so that zone plate-shaped Moire fringes are generated in some prescribed position of an observation system whose position is fixed to a hologram 1. In such a case, the position of the hologram 2 is determined relatively to the hologram 1, therefore, the positioning can be executed.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for manufacturing a hologram disk, and in particular to a hologram disk used for scanning a laser beam as typified by a holographic laser scanner. The present invention relates to a manufacturing method.

(Prior art and its problems) As an optical scanning device, a disk-type optical scanning device using a hologram has recently been proposed in place of the conventional combination of a rotating polygon mirror and an f/θ lens. That is, by arranging a plurality of holograms along the circumference of the disk and rotating the disk, as many scanning lines as the number of holograms are scanned per rotation of the disk. Because it is a disc type,
Although the problem of air resistance during rotation is greatly improved, holographic scanners also have the same problem as the tilt angle of rotating polygon mirrors. A hologram with a spatial frequency distribution of interference fringes is used in a hologram scanner, but in this case, if the position of the hologram with respect to the central axis of the hologram disk shifts in the radial direction, the scanning lines of multiple holograms will be on the same line. do not come. That is, so-called collapse occurs. Therefore, in order to reduce the inclination of the scanning line, it is necessary to accurately determine the radial position of the hologram with respect to the central axis of the hologram disk.

One way to deal with this is to use a disk-shaped photoreceptor with a central axis and record the same holograms one after another on the circumference of the disk, but in this case, all holograms on the disk circumference are It is difficult to make the diffraction efficiency uniform. Therefore, we created a hologram with high diffraction efficiency and uniform distribution using a relief hologram.
The method is to mass produce replicas and attach them to the circumference of the disk.

Alignment methods include a method of inserting a special marker into the hologram and a method of utilizing moire fringes that occur between the hologram and the reference hologram. The method of using moiré fringes allows for highly accurate positioning without modifying the hologram.
It is valid. One of the conventional positioning methods using moiré fringes is described in detail in Japanese Patent Application No. 58-039864 (Hologram Disk Manufacturing Method and Manufacturing Apparatus). In this method, a hologram to be placed and fixed on a hologram disk is This method cannot be applied to the production of a hologram disk in which moiré fringes are generated over a reference hologram, and the position of the hologram on the disk needs to be positioned with high accuracy of about 10 μm or more so that the moire fringes disappear.

(Means for Solving the Problems) A method for manufacturing a hologram disk according to the present invention is a method for manufacturing a hologram disk in which a plurality of holograms for reproducing spherical waves are arranged and fixed on the circumference of the disk. The hologram is superimposed on a reference hologram that reproduces a spherical wave having a focal length different from that of the hologram, with its center shifted, to produce concentric moiré fringes, and the hologram is placed so that the center of the concentric circles of the moiré fringes is formed at a predetermined position. This method of manufacturing a hologram disk is characterized in that the hologram is moved to position the hologram on the disk, and then the hologram is bonded to a disk plate.

(Operation/Principle of the Invention) The shape of moire fringes that occur when two holograms are superimposed can be determined analytically. For example, the moiré fringes that occur when zone plate holograms with different focal lengths are superimposed are as follows. Assuming that the center of the reference hologram is the origin and the hologram to be placed is shifted by Δx in the X direction and Δy in the y direction with respect to the reference hologram, the two holograms are each x2+72=ma2"""" Ex -/1lx )2+(y-Δy)2=nb2
It is written as °°=+21. a and b represent the radius of the minimum circle of each zone plate, and m and n represent positive integers. Moiré stripes are
It is expressed as the intersection of equations (1) and (2), and when the plane is rotated by 180 degrees, l=m+n, and zone plate-like stripes occur. Here, C is a, b, Δ
Although it is a function of X and Δy, it is not an essential term, only the radius of the circle of the zone plate-like moiré fringe changes relatively. The center coordinates of the hologram lens to be placed are (ΔX, Δ
When changing from y1) to (ΔX2.Δy2), the center of the zone plate moiré fringes shifts. Therefore, a and b
If the focal lengths of are slightly different, then a2/(b2- a
2) becomes larger and the sensitivity becomes higher. For example, b=1.
1a, the center of the zone plate-like moiré fringe moves 4.8 times the center coordinates of the hologram lens to be placed.

Accurate alignment can be achieved by adjusting the positional relationship of the mutual holograms so that the center is always located at a constant position when observed with a magnifying system. The reference hologram at this time can be produced using an optical or computer generated hologram method.

When the fringes are magnified 100 times and aligned with an accuracy of 0.5 mm on the observation plane, the placement accuracy of the hologram lens is 1 μm.

(Example) FIG. 1 is a diagram for explaining the principle of alignment according to the method of the present invention. In this case, one hologram is superimposed on the zone plate at a position slightly shifted from the center. At this time, the position of the hologram 2 is adjusted so that zone plate-like moiré fringes are generated at a certain position of the observation system whose position is fixed with respect to the hologram 1.

In this case, the position of the hologram 2 is determined relative to the hologram 1, so alignment can be achieved.

FIG. 2 is a perspective view showing an embodiment of a manufacturing apparatus for implementing the hologram disk manufacturing method of the present invention. A central axis 5 of the disk plate 4 and a reference hologram 6 are fixed to the substrate 3. The hologram 7 can be finely adjusted by a manipulator 8 using an arm 9. The manipulator 8 can rotate the hologram within the plane and move the hologram in two directions orthogonal within the hologram plane and in a direction perpendicular to the hologram plane. A hole is formed in the substrate 3 at a portion where the reference hologram 6 is fixed, and the hologram is illuminated with the illumination light 1o. The hologram is enlarged and imaged by lenses 11 and 12 and observed. In the case of a portion with moiré fringes, for example, in the case of FIG. 1, the manipulator 8 is used to adjust the center of the concentric circles to be located at a fixed position on the observation plane. The positioning is completed when moire fringes are formed at a predetermined position, and the disk plate 4 and the hologram 7 are fixed with adhesive.

(Effects of the Invention) As described above, according to the present invention, by slightly changing the focal length of the hologram placed on the disk and the reference hologram, the hologram is placed on the disk with high precision using moiré fringes. A method for manufacturing a hologram disk is obtained.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of moiré fringes produced by the alignment method of the present invention, and FIG. 2 is a perspective view showing an embodiment of the hologram disk manufacturing method of the present invention. In the figure, 1...Reference hologram, 2...Hologram, 3...Substrate, 4...
Disc plate, 5... Central axis, 6...
...Reference hologram, 7...Hologram,
8...Manipulator, 9...Arm, 10...Illumination light, 11.12...
・・・Lens, National Institute of Industrial Science and Technology 1 Figure

Claims (1)

[Claims] In a method for manufacturing a hologram disk in which a plurality of holograms for reproducing spherical waves are arranged and fixed on the circumference of the disk, the center of the hologram is shifted from a reference hologram for reproducing spherical waves having a focal length different from that of the hologram. to create concentric moiré fringes,
Positioning the hologram on the disk by moving the hologram so that the center of the concentric circles of the moire fringes is located at a predetermined position, and bonding the hologram to the disk plate in the determined position. A method for manufacturing a hologram disk characterized by: