JPH05281490A - Hologram scanner - Google Patents

Abstract

PURPOSE:To prevent the spot size on a scanning surface from largely changing at a scanning center and both ends of scanning. CONSTITUTION:The reconstructing light L1 from a semiconductor laser 10 is made incident a hologram 31 for scanning on a hologram disk 30. The diffracted light L2 diffracted and deflected by the hologram 31 for scanning is introduced to a scanning surface 50 and the deflection angle of the diffracted light L2 is changed by the rotation of the hologram disk 30, by which optical scanning is executed. The pupil shape of the incident reconstructing light L1 on the hologram 31 for scanning is made into an ellipse flattened in an X direction (optical scanning direction) so that the pupil shape of the reconstructing light L1 on the hologram 31 for scanning is made nearly circular.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hologram scanner applicable to laser printers and the like.

[0002]

2. Description of the Related Art FIG. 5 is a schematic view of a hologram scanner, and also shows an optical path viewed from a meridional surface. In the figure, 10 is a semiconductor laser, 11 is a collimator lens, 20 is a front hologram, and 40 is a rear hologram. A hologram disk 30 which is rotationally driven by a motor (not shown) is arranged between the front hologram 20 and the rear hologram 40, and a scanning hologram 31 is provided on this surface.

That is, the reproduction light L1 emitted from the semiconductor laser 10 is incident on the scanning hologram 31 on the hologram disk 30 via the collimator lens 11 and the front hologram 20. After that, the light is diffracted and deflected by the scanning hologram 31, and is guided and imaged as the diffracted light L2 to the scanning surface 50 via the rear hologram 40. When the hologram disk 30 rotates, the outgoing angle of the diffracted light L2 with respect to the scanning hologram 31 changes accordingly, and the diffracted light L2 alternately moves in the direction perpendicular to the paper surface to perform optical scanning. The scanning surface 50 also moves in the direction (Y direction) orthogonal to the optical scanning direction (X direction) to perform sub-scanning.

FIG. 5 shows a state in which the diffracted light L2 is located at the scanning center of the post-installed hologram 31. At this time, the incident angle of the reproduction light L1 with respect to the scanning hologram 31 is set to 45 °, while the diffracted light L2 with respect to the rearward hologram 40 is set.
The incident angle of is set to 0 °.

Now, the pupil shape of the reproduced light L1 emitted from the semiconductor laser 10 is bent in the Y direction (the optical axes of the reproduced light L1 and the diffracted light L2 are bent by an optical system (scanning hologram 31, etc.) in the middle. The relationship between the X-axis and the Y-axis with respect to the optical axis of each ray remains unchanged). Hologram for scanning by collimator lens 11 and front hologram 20
The shape of the pupil of the reproduction light L1 incident on 31 is a perfect circle as shown by the dotted line in FIG.

Since the incident angle of the reproduction light L1 with respect to the scanning hologram 31 is 45 °, the pupil shape of the reproduction light L1 on the scanning hologram 31 is 1: √2 as shown by the dotted line in FIG.
It becomes a flat ellipse at the ratio of. However, when the diffracted light L2 is at the scanning center, the diffracted light L2 for the scanning hologram 31 is
Since the exit angle of is also 45 °, the pupil shape of the diffracted light L2 on the post-installed hologram 40 returns to a perfect circle as shown by the dotted line in FIG.

[0007]

However, as the diffracted light L2 approaches the scanning both ends from the scanning center, the outgoing angle of the diffracted light L2 with respect to the scanning hologram 31 becomes farther from 45 °. The pupil shape of the diffracted light L2 becomes a flat ellipse deviating from the perfect circle as shown by the dotted lines in FIGS. That is, the pupil shape of the diffracted light L2 on the post-installed hologram 40 is greatly different between the scanning center and both ends of the scanning. Therefore, in the case of an optical system with sufficient aberration, the beam is narrowed down to the diffraction limit, and this variation in the pupil shape results in variation in the spot shape on the scanning surface 50. A case where the hologram scanner is used in a laser printer will be described. In this case, the scanning surface 50 corresponds to the photoconductor drum, but if the pupil shape of the diffracted light L2 on the photoconductor drum is different between the scanning center and both ends of the scan, the spot shape on the printer paper is different between the center and both ends. It changes and is distorted, the quality of printing is impaired, and the performance of the hologram scanner is also questioned.

The present invention was created under the background described above, and its object is to improve a hologram scanner so that the spot shape on the scanning surface does not largely change between the scanning center and both ends of the scanning. To provide.

[0009]

According to the hologram scanner of the present invention, the reproduction light emitted from the light source is incident on the scanning hologram on the hologram disk through the pre-position hologram, and is diffracted and deflected by the scanning hologram. In the hologram scanner that guides the diffracted light to the scanning surface via the post-positioned hologram to form an image, and changes the deflection angle of the diffracted light by rotating the hologram disk to perform optical scanning, the pupil of the reproduction light that enters the scanning hologram. It is characterized in that the shape is an ellipse flattened in the optical scanning direction, and the pupil shape of the reproduction light on the scanning hologram is substantially a circle.

[0010]

When the pupil shape of the reproducing light incident on the scanning hologram is made an ellipse flattened in the optical scanning direction so that the pupil shape of the reproducing light on the scanning hologram becomes substantially a perfect circle, The spot shape of the reproduction light becomes an ellipse regardless of the scanning center and both ends of the scanning, and the degree of change of the spot shape between the scanning center and the both ends of the scanning becomes small.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a hologram scanner according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a hologram scanner.

The hologram scanner described by way of example here is equipped in a laser printer.
In the figure, 10 is a semiconductor laser as a light source. The reproduction light L1 emitted from the semiconductor laser 10 is a collimator lens 11,
The light enters the scanning hologram 31 on the hologram disk 30 via the front hologram 20.

The front hologram 20 has a function of diffracting the reproduction light L1 guided from the semiconductor laser 10 and guiding it to the scanning hologram 31, other holograms (scanning hologram 31,
It has a function of correcting the aberration appearing on the scanning surface 50 together with the post-installed hologram 40).

A total of six scanning holograms 31 are provided on the hologram disk 30 along the circumferential direction thereof. A motor 32 for rotating the hologram disk 30 is provided below the hologram disk 30. That is, when the reproduction light L1 is incident on the scanning hologram 31, it is diffracted and deflected by the scanning hologram 31 (diffracted light L2), and when the hologram disk 30 is rotated by the drive of the motor 32, the diffracted light L2 is changed accordingly. The deflection angle is changed.

The diffracted light L2 emitted from the scanning hologram 31 is
Scanning surface 50 via reflection mirror 41 and rear hologram 40
An image is formed by being guided onto (a photosensitive drum). The vertical direction with respect to the scanning surface is shown as the Z direction in the figure.

The rear hologram 40 is a hologram disc
A plate member fixed between the scanning surface 50 and the scanning surface 50 and long in the optical scanning direction is provided for F / θ correction and aberration correction. That is, the posterior hologram 40 corrects the aberration of the diffracted light L2 on the scanning surface 50 (due to the synergistic effect with the anterior hologram 20), and ensures uniform scanning in proportion to the rotation of the hologram disk 30. It has become.

When the hologram disk 30 rotates, the deflection angle of the diffracted light L2 changes, which causes the diffracted light L2 to change to X in the figure.
The optical scanning is performed by moving in the direction. At the same time, the scanning surface 50 also moves in the Y direction in the figure (by rotating the photosensitive drum), so that sub-scanning is performed.

Although the roles of the front hologram 20, the scanning hologram 31, and the rear hologram 40 are basically different from each other, since these holograms integrally play a predetermined role, they are formed in them. The pattern of the power diffraction grating is determined by optimization by ray tracing using a computer.

Now, the pupil shape of the reproduction light L1 incident on the scanning hologram 31 is conventionally a perfect circle or in the Y direction (the reproduction light L1 and the diffracted light L2 have the pre-position hologram 20 and the scanning hologram.
31. Although it is bent by the reflecting mirror 41 and the like, it is assumed that the relationship in the X and Y directions with respect to the optical axis of each light ray does not change. In the present invention, the pupil shape of the reproduction light L1 incident on the scanning hologram 31 is positively made into an ellipse flattened in the X direction (optical scanning direction), and the scanning hologram is obtained.
In connection with the incident angle of the reproduction light L1 with respect to 31, the greatest feature is that the pupil shape of the reproduction light L1 on the scanning hologram 31 is a perfect circle.

In this embodiment, the output aperture of the semiconductor laser 10 is extended in the X direction in order to flatten the pupil shape of the reproduction light L1 incident on the scanning hologram 31 in the X direction (light scanning direction) to form an ellipse. It is done by making a shape. Specifically, the output aperture of the semiconductor laser 10 is selected so that the pupil shape of the reproduction light L1 on the scanning hologram 31 is a perfect circle.

As another method, an optical element such as a prism or a half-wave plate is arranged between the semiconductor laser 10 and the front hologram 20, and the reproduction light incident on the scanning hologram 31 by this optical element. There is a method of making the pupil shape of L1 an ellipse flat in the X direction. The front hologram 21 may have this beam shaping function.

Next, the operation of the hologram scanner configured as described above will be described. However, for the purpose of clarifying the comparison with the conventional device, the incident angle of the reproduction light L1 to the scanning hologram 31 is set to 45 °, while the diffracted light L2 is at the scanning center, the diffracted light to the scanning hologram 31.
Suppose the exit angle of L2 is 45 °.

As a result of changing the output aperture of the semiconductor laser 10 as described above, the pupil shape of the reproduction light L1 incident on the scanning hologram 31 is flattened in the X direction at a ratio of √2: 1 as shown in FIG. It becomes an ellipse. However, since the incident angle of the reproduction light L1 with respect to the scanning hologram 31 is 45 °, the pupil shape of the reproduction light L1 on the scanning hologram 31 is a perfect circle as shown in FIG.

Since the pupil shape of the reproduction light L1 on the scanning hologram 31 is made to be a perfect circle, unlike the conventional case, even when the diffracted light L2 is at the scanning center, the diffracted light L2 on the post-position hologram 40 is different. The pupil shape is an ellipse as shown in FIG. Diffracted light
As in the conventional case, when L2 is at the scanning end, the pupil shape of the diffracted light L2 on the posterior hologram 40 is elliptical.

However, since the pupil shape of the reproduction light L1 incident on the scanning hologram 31 is extended in the X direction (light scanning direction) as shown in FIG. 2, the diffracted light L2 is at the scanning end. At some point, the pupil shape of the diffracted light L2 on the post-installed hologram 40 is elliptical as shown in FIGS. 3 and 4, but the distortion is small unlike the conventional one.

When the pupil shape of the diffracted light L2 on the post-installed hologram 40 is compared at the scanning end and the scanning center, the degree of change is small, and the degree of change is suppressed to a low level in comparison with the conventional case. .. Therefore, in the case of an optical system with sufficient aberration, the beam is narrowed to the diffraction limit (beam waist), so that the spot shape of the diffracted light L2 on the scanning surface 50 does not change significantly between the scanning center and the scanning ends. Become.

Therefore, the dots on the scanning surface 50 do not change greatly between the central portion and both end portions of the printer paper, and as a result,
The performance as a hologram scanner is improved without impairing the printing quality.

The present invention is not limited to the above embodiment,
It is also applicable to a scanner or the like that does not have a front hologram or a rear hologram.

[0029]

As described above, according to the hologram scanner of the present invention, the pupil shape of the reproduction light incident on the scanning hologram is an ellipse flattened in the optical scanning direction, and the pupil shape of the reproduction light on the scanning hologram is a perfect circle. With this configuration, the spot shape on the scanning surface does not significantly change between the scanning center and both scanning ends, and the printing quality is not impaired. Therefore, there is an advantage that the performance as a hologram scanner is improved.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an embodiment of the present invention,
It is a schematic block diagram of a hologram scanner.

FIG. 2 is a diagram showing a pupil shape of reproduction light which is incident on a scanning hologram.

FIG. 3 is a diagram schematically showing a scanning hologram and a post-position hologram, and also a diagram showing a pupil shape of reproduced light on the scanning hologram.

FIG. 4 is a diagram showing a pupil shape of diffracted light on a post-installed hologram.

FIG. 5 is a schematic diagram for explaining a conventional hologram scanner, in which an optical path seen from a meridional surface is shown.

[Explanation of symbols]

 10 Semiconductor laser 30 Hologram disk 31 Scanning hologram 50 Scanning surface L1 Reconstructed light L2 Diffracted light

Claims (1)

[Claims] 1. A reproduction light emitted from a semiconductor laser is incident on a scanning hologram on a hologram disk, and diffracted light diffracted by the scanning hologram and deflected is guided to a scanning surface to form an image, which is recorded on a hologram disk. In a hologram scanner that performs optical scanning by changing the deflection angle of the diffracted light by rotation, the pupil shape of the reproduction light incident on the scanning hologram is made an ellipse flat in the optical scanning direction, and the pupil of the reproduction light on the scanning hologram is A hologram scanner characterized by having an almost perfect circle shape.