JPS6212485B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hologram scanner.

As a conventional technique, a hologram is recorded on a cylindrical recording medium using a converging spherical wave as an object beam and a diverging spherical wave or a plane wave as a reference beam, and then the hologram is moved at a constant speed while being illuminated with reproduction illumination light. There is a hologram scanner that scans by deflecting diffracted light from a hologram.

Before entering into the description of the present invention, a method of manufacturing a hologram for a hologram scanner and a scanning method using the hologram according to the prior art will be described below.

Conventionally, when producing a hologram for a hologram scanner, as shown in FIGS. 1 and 2, the recording medium 1 is a cylindrical transparent body coated with a photosensitive material on the inside or outside. A plurality of holograms are placed on the circumferential surface of the cylinder, with a spherical wave diverging from a point O on the rotation axis of the inner cylinder as a collimating beam 2, and a spherical wave converging to a point P at the center on the scanning plane A-A as an object beam 3. recorded. In addition, in Figure 2,
Symbols L and M indicate a lens and a mirror for guiding the object light 3 to the point P, respectively.

The hologram H recorded in this manner is reproduced using a part of the recording reference light 2 emanating from the point O on the rotation axis as the reproduction illumination light 4, as shown in FIG. In other words, the reproduction illumination light 4 is fixed to illuminate the hologram on the recording medium 1, and the recording medium 1 is rotated in one direction as indicated by the arrow.

Then, from the hologram H, a part of the object light at the time of recording is reproduced as diffracted light 5, which is converged at a position corresponding to the above-mentioned point P, and a light point _P1 is reproduced. Then, this light point _P1 moves as the hologram H rotates, and moves to, for example, a point _P2 . Then, on the scanning plane A-A, the image is reproduced at a position indicated by the symbol _P3 .

In this manner, scanning is performed on the scanning plane A-A. In addition to the above-mentioned example, there is also a hologram scanner in the form shown in FIG. This is different in that the shape of the recording medium is not cylindrical as in the above example but disc-shaped. However, the recording and reproduction (scanning) of the hologram is carried out in accordance with the above explanation. The reference numeral 6 indicates a recording medium, the reference numeral 7 indicates a motor for rotating the recording medium, the reference numeral _H1 indicates a hologram, the reference numeral 8 indicates reproduction illumination light, and the reference numeral 9 indicates a diffracted light.

Traditionally, such hologram scanners
In these devices, the beam diameters of the reproduction illumination lights 4, 8, etc. are always set to be constant.

By the way, there is an application field in which a hologram scanner is used as a scanning device for image formation, such as a laser printer. In this case, it is clear that if the beam diameter of the diffracted light can be freely changed according to the desired pixel density, it will be extremely beneficial in improving the functionality of the laser printers and the like. However, if conventional hologram scanners are used as they are, the beam diameter of the diffracted light cannot be freely changed according to requirements.

The present invention has been made in view of these circumstances, and it is an object of the present invention to provide a hologram scanner which is capable of making the beam diameter of diffracted light variable and is suitable for use primarily as a scanning device for image formation. The purpose is

Embodiments of the present invention will be described in detail below with reference to the drawings. It should be noted that the same reference numerals are used in each figure for parts that are unlikely to be confused with each other.

The present invention is implemented using the property of hologram diffracted light expressed by the following formula (1).

2w ₀ = 4/π×λ・R ₂₀ /d ₀ ...(1) In the above equation, 2w ₀ is the diameter of the convergence point (beam waist part) of the diffracted light, R ₂₀ is the distance from the hologram to the convergence point, d ₀ means the beam diameter of the reproduction illumination light irradiated onto the hologram, and λ means the wavelength of the beam.

In this way, the beam waist diameter (2w ₀ ) of the diffracted light (scanning beam) diffracted by the hologram is inversely proportional to the beam diameter on the hologram of the reproduction illumination light used to obtain this diffracted light. .

On the other hand, in a hologram scanner, the convergence point (beam waist) is set on the scanning plane, so the beam diameter d ₀ (see Figure 6) of the reproduction illumination light 4 that illuminates the hologram is By changing it, the beam diameter of the diffracted light on the scanning surface can be changed.

Figure 7 shows a specific example of this.
Reference numeral 19 in the drawing indicates an aperture mechanism, and the aperture mechanism 19 selectively narrows and adjusts the beam diameter of the reproduced illumination light 4 according to the purpose. Along with this, the beam diameter of the diffracted light 5 on the scanning plane A-A is changed. thus,
It is possible to realize a so-called holoscanner laser plotter (laser scanner) that can obtain pixel (line) density according to the required quality. Incidentally, in FIG. 7, reference numeral 10 indicates a motor for rotating the recording medium 1, reference numeral L _c indicates a collimating lens, reference numeral 11 indicates a modulator, and reference numeral 12 indicates a laser light source.

The position where this diaphragm mechanism 19 is provided, that is, the position where the beam diameter of the reproduced illumination light is narrowed down, may be within the parallel beam of the laser emitted light as shown in FIG. 7, or may be near the hologram as shown in FIG.

In the case of FIG. 8, the recording medium 13 has a concave shape, and a large number of holograms _H2 are recorded on its circumferential surface. The aperture mechanism 19 is placed close to the hologram _H2 .

Regarding the implementation of the present invention in a hologram scanner using a disk-shaped recording medium 6 as shown in FIG. 5, according to the example shown in FIG. 7 or FIG. Once the mechanism is in place, the invention can be implemented.

The diaphragm mechanism as an implementation means of the present invention may be a camera diaphragm mechanism, or a turret type diaphragm plate 19A as shown in FIG.
A mechanism in combination with a motor 19B that selectively controls the amount of rotation of the aperture plate 19A may be used.

The aperture plate 19A in FIG. 9 has several aperture holes F ₁ with different diameters arranged concentrically at intervals.
F ₂ , F ₃ ... F _o is open, motor 19
By controlling the amount of rotation of B, an aperture hole of a desired diameter is selected, and the reproduced illumination light 4 that has passed through the selected aperture hole (for example, aperture hole F ₃ ) is applied to the hologram and is projected onto the scanning plane. to obtain diffracted light that is reproduced with a desired optical diameter.

[Brief explanation of the drawing]

Fig. 1 is a plan view of a recording medium and its surrounding area, explaining a hologram recording method according to the prior art;
The figure is a side view of the same as above, FIG. 3 is a plan view of the above figure explaining the hologram reproduction method, FIG. 4 is a perspective view of the same as above, and FIG. 5 is a hologram scanner using a disc-shaped recording medium. 6 is an enlarged perspective view of the main part of FIG. 4, FIG. 7 is a side sectional view of a hologram scanner that becomes a cylindrical recording medium, explaining an embodiment of the present invention, and FIG. 8 is a perspective view of the present invention. FIG. 9 is a perspective view of a hologram scanner that serves as a concave recording medium, explaining another embodiment of the present invention. FIG. 19...A diaphragm mechanism as a means for changing the beam diameter of the reproduced illumination light, _d0 ...Beam diameter of the reproduced illumination light.

Claims (1)

[Claims] 1. A hologram produced by interfering a spherical wave with a spherical wave or a spherical wave with a plane wave while shining reproduction illumination light on the hologram and changing the relative positional relationship between the hologram and the reproduction illumination light. In a hologram scanner as an image forming scanning device that performs a predetermined scan using diffracted light from a hologram, the beam diameter of the reproduced illumination light is selectively changed according to a desired pixel density formed by the diffracted light. A hologram scanner that is characterized by: