JPS5872120A - Scanning optical system - Google Patents

Abstract

PURPOSE:To minimize the influence of face blur and eccentricity, by forming the illumination luminous flux to an ellipse which is shorter in the direction of the radius of a hologram disc and has a high ellipticity and arranging a unidirectional focusing optical system between a concave mirror and a scanning face. CONSTITUTION:A reproducing illumination light 4 is a parallel beam, and the section of the luminous flux is an ellipse which is longer in the circumferential direction of a disc and is shorter in the direction of the radius and has a high ellipticity. The reproducing beam is a divergent light from a hologram in the direction of the radius of the disc. In a focusing optical system, a cylindrical lens 5 having the axis in the scanning direction is provided besides a concave mirror and is arranged between the concave mirror and the scanning face. Thus, since the focus point is not affected by face deviation DELTAtheta of the disc and the angle and the position of incidence to the concave 3, the influence of face blur and eccentricity of the hologram surface is minimized.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention rotates a disk on which a plurality of holograms are distributed concentrically around a rotation axis, and inputs illumination light onto the disk to reproduce reproduction light obtained from a concave surface. To prevent the pitch unevenness of scanning fII that occurs when scanning is performed by forming an image on the scanning surface.
The present invention relates to an optical scanning device.

2. Description of the Related Art Conventionally, an optical scanning device using a flat disk provided with a hologram lens is known. However, it is generally known that the scan lines produced by such devices are curved. In order to straighten this scanning line, the reproduction beam from the hologram is reflected by a concave mirror with a spherical center on the disk rotation axis, and scanning light parallel to the disk and surface is made perpendicular to the scanning surface to straighten the scanning line. It is proposed that.

(For example, see US Pat. No. 953,105)
However, the above-mentioned proposal also contained various problems in practical use. For example, if there is an error in the attachment of the hologram disk to the rotating shaft, disk O oscillation will occur due to vcm shake, eccentricity, etc. when the disk is rotated, and as a result, pitch unevenness at the scanning edge will occur due to deviation of the scanning position. To prevent this, 4
In this case, it is necessary to increase the mounting precision and processing precision of the disk D to prevent surface wobbling, eccentricity, etc., which is an obstacle to reducing the cost of the hologram-based priority light device.

The present invention is intended to provide an optical deflection device that does not cause pitch unevenness D of scanning lines even if the processing accuracy of the disk and the mounting accuracy of D to the rotating shaft are poor. A detailed explanation will be given below with reference to the drawings.

FIGS. 1 and 2 show a conventionally known optical photometry device using a hologram, in which the diffracted light by the hologram 2 on the hologram disk 1 is once focused at point F, and then becomes a divergent beam of light, which forms a sphere on the rotation axis of the hologram disk 10. An image is formed at point P on the scanning plane by the concave mirror 3 having a center O. When the disc 1 is shaken and a 600-plane blur occurs as shown in FIG. Compared to the principal ray (dotted line), the incident angle and position of the principal ray (solid line) on the θ concave mirror are different, and the deviation of the focal point F is expanded to ΔP. As shown in Figure @4 and Figure 1g5, although the reproduction illumination light 4 is a parallel beam, its beam cross section is long in the circumferential direction of the disk, short in the radial direction, and has an elliptical shape with a large ellipticity. The reproduction beam has a convergence point F in the circumferential direction as in the known device shown in the gt diagram, but in the disk radial direction it is a diverging beam from the hologram. In addition to the concave mirror 3, the imaging optical system includes a cylindrical lens 5 having a generatrix in the scanning direction between the concave mirror and the scanning surface. 〇9th, in the scanning direction plane, the focusing point F and the imaging point P are the conjugate points of the concave mirror 3, as in the prior art, but in the direction perpendicular to this (sub-scanning direction), the concave @ 3 and the cylindrical lens 5, the hologram surface and the imaging point P are in a conjugate relationship. Therefore, as shown in FIG.
Since the imaging point is not affected by the angle of incidence and the position of incidence on the concave mirror 3 even by zero-plane vibration, the positional deviation of the imaging point PQ is extremely small, as shown in the rgG diagram.

FIG. 7 shows a recording system for holograms on a disk used for this purpose. The object light is focused by the lens 6 onto a pinhole Po arranged at a position corresponding to the center of the scanning plane. The θ-diverging light from the pinhole Po is strengthened in one direction only by the cylindrical lens 7, is made into a focused light by the concave mirror 8, and is incident on the disk 1 carrying the hologram recording material. On the other hand, the reference beam is perpendicularly incident on the disk, and interference fringes with the previous object beam are recorded on the recording material.

The hologram 9 recorded at this time has a narrow width in the radial direction of the disk 1, as shown in FIG. 8, depending on the cross-sectional shape of the object beam υ hologram recording surface.

This is another embodiment of the mokkeko invention shown in FIGS. 9 and 10. In the @l embodiment, as shown in Figure #I5,
In the scanning direction plane, the concave mirror 3 has an imaging effect.
'7), and the locus of the imaging point P shows a large curvature of field. For this reason, in order to reduce the diameter of the imaged spot below the allowable value, it is necessary to shorten the scanning length or to increase the distance between the disk and the scanning surface Q. Furthermore, the scanning speed is not constant.

To solve this problem, as shown in Fig. 9.10, the reproduction beam reflected by the concave surface -3 is made parallel in the scanning direction plane and imaged by the fθ lens 10. It is preferable to correct the field curvature using the fθ characteristic of the lens 10 to provide uniform scanning speed. At this time, in the direction perpendicular to the scanning direction (sub-scanning direction), the concave mirror 3. The refractive power of the cylindrical lens 5 may be selected so that the combined refractive power of the fθ lens 10 and the cylindrical lens 50 places the disk l and the imaging point P in a conjugate relationship.

As described above, this invention makes the illumination light beam of the hologram D narrow in the radial direction of the disk, and includes a unidirectional imaging optical system in the imaging optical system consisting of a concave mirror etc. in the scanning direction. By placing the hologram plane and the scanning plane in a conjugate relationship in a plane perpendicular to As far as possible, the reproduction illumination light may be focused on a single point on the disk rotation axis, the unidirectional imaging optical system may be changed to a cylindrical reflector, a spheroidal reflector, etc., or the hologram may be a transmission type. There is no need to explain that you can freely change the design, such as changing it to a reflective type.

[Brief explanation of the drawing]

Figures 1 and 2 are a diagram of a known hologram scanning device υ optical arrangement and a plan view of a hologram disk used therein;
Figure 1 is an explanatory diagram of the scanning line deviation of the scanning device, Figures 4 and 5 are diagrams of the optical arrangement and light weight of one embodiment of the scanning apparatus of the present invention, and Figure 6 is an illustration of the scanning line deviation. Explanation/Diagrams, Figures 7 and 8 are an optical layout diagram of the hologram e recording system used in the D invention, a plan view of the hologram disk O, Figure 9, and Figure 1.
FIG. 0 is an optical arrangement and optical path diagram of another embodiment. l: Hologram disk 3.8: Concave mirror 5.7: Cylindrical lens xo: fθ Relen Figure 1

Claims (1)

[Claims] Reproduction illumination light was incident on a fixed position of a disk with multiple hologram lenses arranged concentrically around the rotation axis, the disk was rotated, and the reproduction light from the hologram was focused onto the scanning surface by a concave mirror. In the scanning optical system, the illumination light beam is made into a narrow light beam in the radial direction of the hologram disk, and a unidirectional imaging optical system is arranged between the concave mirror and the scanning surface, and the hologram surface and scanning are arranged in a direction perpendicular to the scanning direction. A scanning optical system characterized by having a conjugate relationship with a surface.