JP2886733B2 - Hologram creation method and creation apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hologram forming method and apparatus, and more particularly to a hologram forming method and apparatus for recording an aspherical wave.

A hologram can be used for an optical element such as a laser scanning optical system and a hologram lens. recent years,
In hologram optical elements, there is an increasing demand for recording complex aspherical waves. In the hologram forming method and the hologram forming apparatus, it is necessary that a hologram recording the complicated aspherical wave can be formed with high accuracy and in a short time.

[0003]

2. Description of the Related Art Conventionally, in order to record a complex aspherical wave on a hologram, there has been known a method of calculating an interference fringe of a hologram by calculation and directly drawing the interference fringe with an electron beam or the like to form a hologram. .

[0004]

However, in the conventional method of calculating the interference fringes of a hologram by calculation and directly drawing the interference fringes with an electron beam or the like to form a hologram, a complicated interference fringe is drawn with high precision. However, it is difficult and time-consuming.

The present invention has been made in view of the above points, and has as its object to provide a hologram forming method and a hologram forming method capable of forming a hologram recording a complicated aspherical wave with high accuracy and in a short time. And

[0006]

According to the present invention, there is provided a hologram forming method for forming a hologram by irradiating a hologram recording material with two forming waves, wherein one of the forming waves is a spherical wave emitted from a point light source and the other is a spherical wave. Is an aspherical wave whose phase is modulated by a mirror matrix group.

[0007]

According to the present invention, in a hologram producing method for producing a hologram by irradiating a hologram recording material with two producing waves, one of the producing waves is a spherical wave and the other is a
Since the aspherical wave whose phase is modulated by the mirror matrix group is used, a complicated aspherical wave can be recorded with high accuracy. In addition, since the setting of the spherical wave and the aspherical wave, which are the creation waves, can be performed in a short time, the hologram can be created in a short time.

[0008]

FIG. 1 shows a configuration diagram of a hologram forming apparatus to which a first embodiment of the present invention is applied. In the figure, 10 is a laser as a light source, 11 is a beam splitter for dividing the laser beam into two forming waves, 12 and 14 are reflecting mirrors, and 13 is a lens for converging the laser beam and converting it into a spherical wave. And 6 denote pinholes for adjusting the position of the point light source. Also, 1
Reference numeral 5 denotes a beam expander for expanding the laser light, and 16 denotes a half mirror. 7 is a mirror matrix group (Defor
Table 2 shows the MMC (Match Mirror Device: DMD). The DMD 7 has minute mirrors arranged in a matrix, and can change the height position of each mirror using a piezoelectric element to modulate the phase of reflected light.

Reference numeral 1 denotes a hologram recording material, 2 denotes a cell obtained by dividing the hologram recording material 1, 8 denotes a mask for irradiating only the cell 2 with a generation wave, 3 denotes a spherical wave of the generation wave, and 4 denotes an aspheric surface of the generation wave. Show the waves.

Reference numeral 9 denotes a stage for moving the hologram recording material 1 in order to align the cell 2 of the hologram recording material 1 with the mask 8. Reference numeral 17 denotes a control circuit,
MD7 and a pinhole drive as a pinhole drive means
The operation circuit 18 is controlled. The status is controlled by the control circuit 17.
X, Y direction position of the page 9 and each mirror constituting the DMD 7
Height and the optical axis direction of the pinhole 6 (A ₁ , A ₂
Direction) is set. The laser light emitted from the light source 10 passes through the beam splitter 11, is reflected by the reflecting mirror 12, is converged at the position of the pinhole 6 by the lens 13, and is converted into a spherical wave 3 emitted from the point light source 5. On the other hand, the light reflected by the beam splitter 11 is reflected by the reflecting mirror 14 and the beam expander 15
Is converted into a plane wave expanded to a predetermined size. This plane wave is reflected by the half mirror 16 and enters the DMD 7. The plane wave incident on the DMD 7 is
Phase is modulated by each minute mirror of
Is converted to The hologram of the cell 2 of the hologram recording material 1 is created by the above-mentioned spherical wave 3 and aspherical wave 4.

In FIG. 1, the origin of the X axis and the Y axis is the center of the mask 8, the Y axis is the left direction from FIG. 1 from the origin, and the X axis is the direction from the origin to the front to the back of FIG. I do.

Next, a hologram forming method according to this embodiment will be described. The phase φ of the wavefront of the hologram to be created
(X, Y) is assumed to be given. The hologram is created by approximating the phase φ (X, Y) of the given wavefront with the phase of the spherical wave 3. Phase φ (X, Y)
The hologram recording material 1 is divided into cells 2 of a predetermined size determined by the size of the mask 8 so that hologram can be approximated by the phase of the spherical wave 3, and a hologram is created for each of the divided cells 2.

FIG. 2 is an explanatory diagram of division of the hologram recording material 1. FIG. 2 shows the case where the hologram recording material 1 is divided into 64 cells 2 by equally dividing the hologram recording material 1 into 8 in both the vertical and horizontal directions.
The vertical and horizontal dimensions of the cell 2 are about 100 μm, and the number of divisions changes according to the dimensions of the hologram recording material 1.

First, the stage 9 is moved to align the cell 2 for forming a hologram with the mask 8. Here, the cell 2 is an n-th cell 2 in the divided hologram recording material 1. FIG. 3 is an explanatory view of the cell 2 of the hologram recording material 1. In the figure, the cell 2 is aligned with the mask 8 and
The state when the center of the cell 2 is placed at the origin of the X axis and the Y axis is shown. The section 32 of the cell 2 shown in the figure corresponds to each minute mirror of the DMD 7 and indicates a unit area when one plane wave of the created wave is subjected to phase modulation by the DMD 7 as described later. . FIG. 4 shows an example of the distribution of the interference fringes 31 of the hologram to be created in the cell 2.

Next, the difference between the phase of the wavefront of the hologram to be created and the phase of the approximate spherical wave 3 is minimized.
The position of the point light source 5 is determined. Let the phase of the wavefront of the hologram to be created in the n-th cell 2 be φ ⁿ (X, Y),
ⁿ (X, Y) of the spherical wave 3 phases is created waves to approximate the phi _R ⁿ and (X, Y). When the position of the point light source 5 with respect to the cell 2 is defined by F _n and H _n in FIG. 1, φ _R ⁿ (X,
Y) is φ _R ⁿ (X, Y) = K√ (F _n ² + X ² + (H
_n− Y) ² ). Here, the phase φ ⁿ (X, Y) of the hologram to be created and the phase φ _R ⁿ (X,
It is necessary to minimize the difference Y). For this purpose, the phase φ of the hologram to be created, expressed by the following equation,
ⁿ (X, Y) and the phase φ _R ⁿ (X, Y) of the spherical wave 3 mean square E of the difference to calculate the value of F _n and H _n of the minimum.

E = ∬ (φ ⁿ (X, Y) −φ _R ⁿ (X, Y)) ² dX dY The values of F _n and H _n that minimize E are calculated by the above equations,
F _nm and H _nm , respectively. Control circuit 1 for pinhole 6
7 by that move through the pinhole driving circuit 18, the F _n and H _n, is set to the value of the calculated F _nm and H _nm. Thereby, the position of the point light source 5 in the n-th cell 2 is determined. The movement of the pinhole 6 can be performed in a short time by the control circuit 17 and the pinhole drive circuit 18.

Next, in each divided section 32 of the cell 2 corresponding to each minute mirror of the DMD 7, the height position of each mirror of the DMD 7 is determined so as to eliminate the difference between the wavefront to be created and the actual wavefront. .

FIG. 5 is an explanatory diagram of the DMD. FIG. 5 (A)
Shows a view of DMD7 from the side, and FIG.
7 shows a view from below. As shown in FIG.
In the figure, minute mirrors are arranged in a matrix at a pitch of about 5 μm, and the height position (vertical direction in FIG. 5A) of each mirror can be changed in minute units.

As shown in FIG. 5, the number for dividing each mirror of the DMD 7 is p for the X-axis direction, and q for the Y-axis direction (in the example of FIG. 5, p and q are 1). (Integer of 10 to 10), a mirror whose section number in the X-axis direction is p and a section number q in the Y-axis direction is a mirror (p, q).

As shown in FIG. 3, the cell 2 is divided into sections 32 corresponding to the respective mirrors of the DMD 7, and the numbers of the sections in the X-axis direction and the Y-axis direction are p and q (in the example of FIG. 3, respectively). ,
p and q are integers of 1 to 10), and the section 32 in which the section number in the X-axis direction is p and the section number in the Y-axis direction is q is a section (p, p).
q), and these coordinates are (X _p , Y _q ).

The phase φ ⁿ (X, Y) of the wavefront of the hologram to be created in the n-th cell 2 and the approximate spherical wave 3
The phase difference of the phase ^{_{φ R n (X, Y)}} , i.e. a non-spherical component φ _A ⁿ (X, Y) of the hologram to be created when the, holds the following equation.

[0022] ^{_{φ A n (X, Y)}} = - (φ n (X, Y) -φ R n (X, Y)) - Thus, (X _p, Y _q) In, φ _A ⁿ (X _{p, Y q) = - (} φ n (X p, Y q) -φ R n (X p, Y q)) - satisfies the following equation. From the right side of the equation, the phase difference between the wavefront of the hologram to be created and the spherical wave 3 in each section (p, q) of the cell 2 is obtained. This phase difference is converted into a phase difference in each mirror (p, q) of the DMD 7, and a height position of each mirror (p, q) corresponding to the converted phase difference is calculated.

After calculating the height position of each mirror (p, q), the control circuit 17 applies a voltage to the piezoelectric element for driving each mirror of the DMD 7, and the height of each mirror (p, q). The position is set to this calculated value. Each mirror (p,
The setting of the height position in q) can be performed in a short time by the control circuit 17.

The calculation of the phase difference between the wavefront of the hologram to be created and the spherical wave 3 in each section (p, q) of the cell 2 is advantageous in terms of calculation time, etc., by introducing the following equation. The calculation method is described below.

The cell 2 (X, Y) in the phase difference between the hologram plane and spherical waves 3 to be created, namely a non-spherical component of the hologram to be created φ _A ⁿ (X, Y) the expression of a power series type of formula Expressed as

[0026] ^{_{φ A n (X, Y)}} = KΣC i + j n · X i · Y j - from Equation and Equation, holds the following equation.

− (Φ ⁿ (X, Y) −φ _R ⁿ (X, Y)) = KΣC _{i + j} ⁿ · X ⁱ · Y ^j −− From this equation, the series coefficient C _{i + j} ⁿ is appropriately determined. It is determined by performing approximate approximation. When C _{i + j} ⁿ is obtained, (X,
Y) The phase difference between the wavefront of the hologram to be created and the spherical wave 3, ie, the aspherical component φ of the hologram to be created
_A ⁿ (X, Y) can be calculated from the equation. Therefore, cell 2
The calculation of the phase difference between the wavefront of the hologram to be created and the spherical wave 3 in each section (p, q) of equation (2) is expressed by ( _Xp , _Yq ).
By substituting the value of

As described above, the position of the point light source 5 and the DMD 7
The height position of each mirror can be set, and the phases of the spherical wave 3 and the aspherical wave 4, which are the creation waves of the n-th cell 2 to be created, are determined. In this state, a laser beam is emitted from the light source 10, and the spherical wave 3 and the aspherical wave 4 whose phases are determined as described above are irradiated, whereby a hologram of the n-th cell 2 can be created.

As described above, according to the method of the first embodiment, the phase of the wavefront of the hologram to be created is approximated by the phase of the spherical wave 3 and the aspherical wave 4 for correcting the aspherical component by the DMD 7 is generated. Since the hologram is generated, a hologram in which a complicated aspherical wave is recorded can be created with high accuracy. Further, since the position of the point light source 5 and the height position of each mirror of the DMD 7 can be set in a short time, a hologram can be created in a short time.

FIG. 6 shows a configuration diagram of a hologram forming apparatus to which the second embodiment of the present invention is applied. In the figure, the same components as those in FIG. In the second embodiment shown in FIG.
The telescope system 21 is arranged between D7. DMD in the figure
When the distance L ₁ between the lens system 7 and the lens system 22 is set to be equal to the distance L ₂ between the hologram recording material 1 and the lens system 22, the telescope system 21 (magnification 1: 1) prevents the hologram recording material 1 from moving in the cell 2. The phase of the spherical wave 4 becomes equal to the phase of the aspherical wave 4 in the mirror of the DMD 7. Therefore, cell 2
Can be extremely easily converted from the phase in each section (p, q) to the height position of each mirror (p, q) of the DMD 7.

In the case where there is a difference between the dimension of the DMD 7 and the dimension of the cell 2, the telescope system 21 may have a function of changing the magnification and converting this dimension ratio.
For example, when the size of the cell 2 is smaller than the DMD 7, by making the magnification of the telescope system smaller than 1, a hologram having a finer pattern than when the magnification is 1 can be created in the cell 2.

In the method of the second embodiment, similarly to the method of the first embodiment, a hologram recording a complicated aspherical wave can be created with high precision and in a short time.

[0033]

As described above, according to the present invention, one of the hologram-forming waves is a spherical wave and the other is a non-spherical wave whose phase is modulated by a mirror matrix group. Holograms that record spherical waves can be created with high precision, and the creation of spherical waves and aspherical waves can be set in a short time, so that holograms can be created in a short time. .

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a hologram forming apparatus to which a first embodiment of the present invention is applied.

FIG. 2 is an explanatory diagram of hologram division.

FIG. 3 is an explanatory diagram of a hologram cell.

FIG. 4 is a diagram showing an example of an interference fringe distribution of a cell.

FIG. 5 is an explanatory diagram of a DMD.

FIG. 6 is a configuration diagram of a hologram forming apparatus to which a second embodiment of the present invention is applied.

[Explanation of symbols]

 Reference Signs List 1 hologram recording material 2 cell 3 spherical wave 4 aspherical wave 5 point light source 6 pinhole 7 DMD 8 mask 9 stage 10 light source 11 beam splitter 12, 14 reflecting mirror 13 lens 15 beam expander 16 half mirror 17 control circuit 18 pinhole Drive circuit 21 Telescope system 22, 23 Lens system 31 Interference fringe 32 Section

Claims (4)

(57) [Claims] 1. A hologram production method of irradiating two create waves in the hologram recording material to create a hologram, a spherical wave that is one of creating waves emitted Ri by a point light source, the other to create wave mirror producing holograms method characterized in that an aspherical wave obtained by modulating a more phase in the matrix group. 2. A minimum error phase of the spherical wave on which the root mean square of a difference between a phase of a hologram to be created and a phase of the spherical wave is calculated on the hologram recording material, and the calculated minimum error phase is obtained. light source point against the said hologram recording material as
2. The hologram creating method according to claim 1 , wherein the position is moved. Wherein said aspherical wave is a hologram creation method according to claim 1 or 2, characterized in that it is irradiated to the holographic recording material through a telescope system. 4. A laser beam of Ri by the light source is divided from <br/> the beam splitting hand stage, creating a hologram by irradiating two laser beams said divided on the hologram recording material on the stage hologram in creating device, a pin hole <br/> Lumpur for converting one of the laser light the divided spherical wave, a pinhole drive means to vary the position of the pinholes, the divided laser beams of the other phase Are arranged in a matrix.
A mirror matrix group of aspherical wave modulated by a plurality of mirrors that location, the pinhole driving hand Dan及 beauty the mirror matrix group
Hologram creation and wherein the configuration and the to have a plurality of respective heights braking Gosuru control <br/> circuitry of mirrors constituting.