JPS6285805A - Arranging method for zone plate - Google Patents

Abstract

PURPOSE:To arrange a zone plate (ZP) at a reference position with good operability and high precision by judging the position shifting direction of the ZP from a moire fringe. CONSTITUTION:A reference hologram 1 and a manipulator MA 3 are fixed on a base plate 8. The ZP 2 is adjustable by the MA 3 with an arm 4 and the MA 3 can moves the ZP 2 in two orthogonal directions in the plane of the ZP 2 and in a direction perpendicular to the plane of the ZP 2. The base plate 8 has a hole at the position where the hologram 1 is fixed and the ZP 2 which is lighted 2 is observed while its image is enlarged and formed by lenses 6 and 7. When the ZP 2 is superposed upon the hologram 1, a multicurve moire fringe is formed. At this time, four multicurves are positioned in a state A of point symmetry about the center of the hologram 1. In another state B, vertexes of multicurves face in fixed directions. In this case, the ZP 2 is moved in the directions of the vertexes by the MA 3 to the state where all the directions of the vertexes of the multicurve moire fringe face the center. Thus, the direction of shifting is judged.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a zone plate arrangement method.

[Prior art and its problems]

As a small lens used in optical tisf heads, etc.
In place of conventional refractive lenses, considering lightness and mass production,
Diffractive lenses such as zone plates have been proposed.

For the zone plate, there are methods of recording holographically, and methods of calculating the phase using a computer and drawing it using an electron beam or the like. Zone plates are often phase-type to increase diffraction efficiency, making it difficult to clearly observe this psalm.

In such a case, alignment methods include a method of inserting a special marker in the zone plate and a method of utilizing moiré fringes generated between the zone plate and the reference hologram. The method using moiré fringes is effective because it allows highly accurate alignment without modifying the zone plate. For example, a conventional positioning method that makes use of all moiré fringes is
It is described in detail in the specification of 9864 "Hologram Disc Manufacturing Method and Manufacturing Apparatus."

In this positioning method using moiré fringes, the holograms are positioned so that the linear moiré fringes that occur when a zone plate-shaped hologram is superimposed on a reference hologram disappear. However, with this method, it is not possible to directly determine the direction of misalignment from the moiré fringes, and this is determined by moving the zone plate and observing the changing spacing of the fringes.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for determining the direction of displacement of a zone plate from moiré fringes and arranging the zone plate with good operability and high precision with respect to a reference position.

[Structure of the invention]

According to this invention, a reference hologram in which two holograms for reproducing the same cylindrical wave are arranged orthogonally to each other and a zone plate are superimposed to produce a plurality of polycurvilinear moiré fringes,
There is obtained a zone plate arrangement method characterized in that the arrangement position of the zone plate is determined so that the multi-curved moiré fringes are point symmetrical with respect to the center of the hologram.

[Function/principle of the invention]

The shape of moiré fringes that occur when the zone plate and hologram are superimposed can be determined by calculation. The moiré fringes that occur when a zone plate and a hologram that reproduces a cylindrical wave are superimposed are as shown below. Assuming that the center of the zone plate is shifted by ΔX in the X direction from the center line of the hologram, the zone plate and hologram are each (X-Δx)2+y" = m a"
・・・・・・(1)x”=nb”
It is written as `` ・'' (2). a is the radius of the smallest circle of the zone plate, b is the distance between the innermost straight lines, m.

n represents a positive integer.

Since moiré fringes are expressed as the intersection of equations (1) and (2), if we set l=mthn and rearrange equations (1) and (2), we get (3). In equation (3), α is a function of a, b, and ΔX, and this equation indicates that only the eccentricity of the quadratic curve changes, but the position of the center does not change.

case is a set of polycurves.

When this moire fringe is observed at the origin, when the center of the zone plate changes from (ξ1.η) to (ξ2.η), the center of quadratic curve mower No. 1 moves in the X direction. Considering the case of observing a multi-curved moire pattern, this corresponds to the negative sign in equations (3) and (4). If b is set slightly larger than a, a 2 in equation (4)
The term /AL-aLB becomes larger, and the amount of movement of the center of the moiré fringes increases. A polycurve has a point-symmetric shape with respect to the center, and depending on the direction of its curvature, it can be a positive polycurve or
It can be determined whether the curve is on the negative side.

Therefore, by observing the direction of curvature of the multi-curved moiré fringe, the center position can be determined, and furthermore, the direction of deviation can be determined. In the case of rubbing in the X direction, the above discussion applies if a hologram with stripes distributed in the X direction is used. If the holograms are shifted in the X direction and the X direction, a hologram shown in FIG. 2 in which a hologram distributed in the X direction and a hologram distributed in the X direction are superimposed may be used. Such holograms can be easily exploded using mechanical hologram techniques.

〔Example〕

FIG. 1 is a perspective view of one embodiment of an apparatus for aligning zone plates using the method of the present invention. In the figure, 1 is a reference hologram, 2 is a zone plate, 3 is 1 nibulator, 4 is an arm, 5 is an illumination light source, 6 and 7 are lenses, and 8 is a substrate. Reference hologram 1
And the manipulator 3 is fixed to the substrate 8. The zone grade 2 can be finely adjusted by the manipulator 3 using the arm 4. The manipulator 3 can move the zone plate 2 in two directions orthogonal within the plane of the zone plate and in a direction perpendicular to the plane of the zone plate.

A hole is provided in the substrate 8 in the part where the reference hologram 1 is fixed, and a zone plate 2 is illuminated with the illumination light 5.
is magnified and observed by lenses 6 and 7.

FIG. 2 is a diagram showing an example of a reference hologram used in the method of the present invention, and FIGS. 3 and 4 are diagrams for explaining the principle of alignment of the present invention.

When a zone plate is superimposed on the reference hologram shown in FIG. 2, multi-curvilinear moiré fringes are generated. As shown in FIG. 3, the four polygonal curves are aligned to be point symmetrical with respect to the center of the hologram. In a state where the alignment is not completed, the vertices of the polygonal curve are oriented in one direction, as shown in FIG. At this time, the zone plate is moved toward the apex, resulting in the state shown in FIG. That is, in FIG. 1, the manibulator is used to adjust the direction of the vertices of the multi-curved moiré fringes so that they all point toward the center.

With conventional methods that utilize the disappearance of moire forests, it was not possible to determine the direction of deviation, but with this example, it is possible to easily determine the direction of deviation, as shown in Figure 4. .

Regarding the placement accuracy, as a result of actual measurements, when b=1.7a, it was almost the same as that of the conventional example. For example, let this value be b=
1. If la is set, the placement accuracy will be about 10 times that of the conventional example.

〔Effect of the invention〕

As described above, this invention has the effect of making it possible to position the zone plate with high operability and high precision with respect to the reference position by making use of the multi-curved moiré slope to clarify the direction of deviation. .

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the zone plate placement method of the present invention, FIG. 2 is a diagram showing an example of a reference hologram used in the placement method of the present invention, and FIGS. 3 and 4 are moiré It is a figure showing an example of a pine tree. In the figure, l...Reference hologram, 2...
...Zone plate, 3...Manipulator, 4-...Arm, 5...M Meiko L
6.7...Lens, 8. ...l \ ...board. Agent Patent Attorney Uchihara (,t
\, -'#f Figure 82 Figure 3 Figure 4 Procedural amendment (voluntary) 1. Display of case 1985 Patent application No. 2262
No. 40 No. 2, Name of the invention Zone plate arrangement method 3, Relationship with the amended person case Applicant 5-33-1 Shiba, Minato-ku, Tokyo (423) NEC Corporation Representative Tadahiro Sekimoto 4, Agent 5 , Subject of amendment (1) Claims column of the specification (2) Detailed explanation of the invention column 6 of the specification, Contents of amendment (1) The claims are amended as shown in the attached sheet. (2) On the 3rd page, line 12 of the specification, [Appendix Claims

Claims (1)

[Claims] (1) Two holograms that reproduce the same cylindrical wave are placed orthogonally arranged, and a reference hologram and a zone plate are overlapped to produce a plurality of polycurvilinear moiré fringes, and the polycurvilinear moiré fringes are placed at the center of the hologram. A method for arranging a zone plate, characterized in that the arrangement position of the zone plate is determined so as to be point symmetrical with respect to the zone plate.