JP3206334B2 - Optical scanning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device, and more particularly to an optical scanning device using a hologram disk.

[0002]

2. Description of the Related Art Generally, an optical scanning device using a hologram comprises a semiconductor laser 101, a condenser lens 102, and a hologram disk 103, as shown in FIG. The emitted light is converted into, for example, divergent light by the condenser lens 102, then diffracted by the hologram facet 112 of the hologram disc 103, and irradiated on the photosensitive drum 120. The hologram disk 103 is attached to the rotation shaft of a motor 122, and the hologram disk 103
Is rotated, first-order diffracted light of the laser light diffracted by the hologram facet 112 of the hologram disk 103 scans the photosensitive drum 120 linearly in the longitudinal direction. That is, the hologram disk 103 deflects and converges the laser light.

The hologram facet 112 is provided on one side of the hologram disk 103, that is, on the diffraction surface 1 as shown in FIG.
27 is formed as a shape of irregularities on the surface, a so-called surface relief. The angle of incidence of the laser beam 130 on the hologram facet 112 is restricted based on the hologram pattern of the hologram facet 112 enabling linear scanning with a minute spot, and the arrangement of the photosensitive drum 120, the condenser lens 102, and the semiconductor laser 101. ing. In particular, if the angle of incidence of the laser beam 130 on the hologram disk 103 is changed, the arrangement of all the devices related to the laser beam must be changed, which is very troublesome.
Angle of incidence of the laser beam 130 with respect to the motor 122, the photosensitive drum 120, the condenser lens 102, the semiconductor laser 1
01 and so on.

[0004]

However, the laser beam 13 incident from the entrance surface 128 of the hologram disc 103 where the hologram facets 112 are not formed.
0 is diffracted by the hologram facet 112 and becomes a scanning light 132 as shown in the range between the solid lines, but a part thereof is reflected as shown in the range between the broken lines. The reflected laser light is reflected by the incident surface 128 and then re-enters the hologram facet 112 to be scanned by the scanning light 132.
Is diffracted in the same direction as the above and becomes stray light 135. This stray light 1
Due to 35, the scanning light 132 and the stray light 135 are incident on the photosensitive drum 120, so that the scanning line is doubled, and a ghost image is generated or noise is increased.
There was a problem that the quality of the image deteriorated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to provide an optical scanning device using a hologram in which image quality is not deteriorated by stray light.

[0006]

In order to achieve this object, an optical scanning device according to the first aspect of the present invention comprises a hologram scanner.
The thickness of the hologram disc near the facet is
Formed thicker than other parts of hologram disc
A hologram disk having a thickness such that, of the incident laser light incident from the other surface, the laser light reflected by the hologram facet and reflected again by the other surface does not enter the hologram facet. .

Further, the optical scanning apparatus of the invention described in claim 2, further radial width of said hologram facet is substantially not equal to the radius direction of the spot diameter on the hologram facet of the incident laser beam.

[0008]

In the optical scanning device according to the first aspect of the present invention, the hologram disk has a hologram facet formed on one surface and no hologram facet formed on the other surface. Near the hologram facet
The hologram disc is formed thicker than other parts
Have been. The incident laser light enters from the other surface and is diffracted by the hologram facet, but part of the incident laser light is reflected by the hologram facet and becomes reflected light. The reflected light is reflected again on the other surface and reaches a position off the hologram facet on one surface of the hologram disk due to the thickness of the hologram disk near the hologram facet. In other words, the holog
Adjust the thickness of the hologram disc near the ram facet to another
By making the part thicker than the part, the reflected light
It prevents it from entering the gram facet .

Further, in the optical scanning device according to the present invention, the radial width of the hologram facet is made substantially equal to the radial spot diameter of the incident laser light on the hologram facet, and the reflected light There it reaches the position again out of the range of the hologram facets on one surface of the hologram disc.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

An optical scanning apparatus to which the present invention is suitably applied is shown in FIG.
As shown in the figure, a semiconductor laser 15 which is a laser light source,
A collimating lens 16 that converts the laser light emitted from the semiconductor laser 15 into substantially parallel light, and the substantially parallel light from the collimating lens 16 is converged and incident in a direction perpendicular to the circumferential direction of the hologram disk 10, that is, in the sub-scanning direction. Hologram disk 10 on which hologram facet 12 for forming laser beam 18 and converging on hologram facet 12 and hologram facet 12 for diffracting incident laser beam 18 are formed.
And a hologram lens 19 that focuses the diffracted light 20 from the hologram disk 10 on the photosensitive drum 40, and a motor 22 that is a rotation drive unit that rotates the hologram disk 10.

A plurality of hologram facets 12 are formed on the hologram disk 10 as shown in FIG. 2, and the width of the hologram facet 12 in the radial direction is substantially equal to the spot diameter of the incident laser light 18 in the radial direction.
An enlarged cross section near the hologram facet 12 is schematically shown in FIG. The hologram facet 12 is provided on one surface of the hologram disk 10, that is, on the diffraction surface 27,
That is, it is formed as a surface relief.

The incident laser light 18 enters from a surface on which the hologram facet 12 is not formed, that is, from an incident surface 28, is diffracted by the hologram facet 12, and becomes a diffracted light 20 as shown by a range between solid lines. A part of the incident laser light 18 is reflected by the hologram facet 12 and the incident surface 28, and becomes a reflected light 30 as shown in a range sandwiched by a dotted line to reach the diffraction surface 27. Here, the thickness d of the hologram disk 10 is determined so that 2d · tan θ> a (1), where θ is the reflection angle at the hologram facet, and a is the spot diameter of the incident laser beam 18 in the radial direction. ing.

Since the width of the hologram facet 12 is substantially equal to the radial spot diameter a of the incident laser beam 18, the reflected light 30 reaches a position closer to the center of rotation than the range of the hologram facet 12 on the diffraction surface 27. That is, the reflected light 30 that has reached the diffraction surface 27 does not enter the hologram facet 12. Since the reflected light 30 is prevented from being incident on the hologram facet 12 in this manner,
The hologram disc 10 is directed in a direction different from that of the diffracted light 20.
And does not reach the photosensitive drum 40 as stray light. For this reason, a ghost image or noise does not occur, and an adverse effect on image quality formed on the photosensitive drum can be suppressed.

Since the hologram lens 19, which is a condensing optical means, has power in the sub-scanning direction, the diffracted light 20 diffracted by the hologram facet 12 and diverged is condensed on the photosensitive drum 40 as a minute spot. I do. In the main scanning direction, which is a direction parallel to the longitudinal direction of the photosensitive drum 40, the laser light 18 incident on the hologram facet 12 is substantially parallel light, and the diffracted light 20
Is converged by the hologram lens 19 with a power different from that in the sub-scanning direction, and is condensed on the scanning line 40 as a minute spot. In addition, such a hologram lens 1
The light condensing function 9 can also compensate for eccentricity, surface deflection of the hologram disk 10 and fluctuations in the diffraction angle due to fluctuations in the wavelength of the semiconductor laser 15, so that a better image can be obtained. Also, since the angle of incidence of the laser beam 130 on the hologram disk 112 is not changed,
The arrangement of the devices related to the laser light is also fixed as it is, and a good image can be obtained only by changing one component.

Here, in the above embodiment, the radial width of the hologram facet 12 is made substantially equal to the radial spot diameter of the incident laser light 18, but is not limited to this. For example, as shown in FIG. 4, the width of the hologram facet 12 in the radial direction may be larger than the spot diameter of the incident laser light 18 in the radial direction. At this time, if the thickness of the hologram disk satisfies the expression (1),
By causing the incident laser light 18 to enter the end of the hologram facet 12, the generation of stray light can be prevented. The hologram disc may be further thickened so that the reflected light 30 does not enter the hologram facet 12 when it reaches the diffraction surface 27. It is to be noted that the thickness of the hologram disk 10 can be made relatively thin by making the radial width of the hologram facet 12 substantially equal to the radial spot diameter of the incident laser light 18 as in the previous embodiment. Become.

Further, it is not necessary for the hologram disk 10 as a whole to satisfy the relationship of the expression (1). For example, it is sufficient that only the vicinity where the hologram facet 12 is formed as shown in FIG. 5 is satisfied. As a result, the entire hologram disk 10 can be reduced in weight, and can be rotated at a high speed. Further, as shown in FIG. 6, an auxiliary disk 51 having substantially the same refractive index as the hologram disk 10 may be attached to the hologram disk 10.

The diffraction surface 2 of the hologram disk 10
7 and the entrance surface 28 need not be parallel over the entire hologram disk 10. For example, as shown in FIG.
The surface where 0 is reflected by the incident surface 28 may be tapered. This makes it possible to more reliably separate the diffracted light 20 and the reflected light 30.

The configuration of the optical scanning device is not particularly limited as long as the hologram disk 10 is used.
For example, the incident laser light 18 may be converged also in the main scanning direction. Instead of using these optical elements, as shown in FIG. 8, an optical element such as a hologram lens 60 or a front hologram as an irradiation optical unit may be arranged in front of the hologram disk 10. Further, as shown in FIG. 8, an optical element such as a post-hologram 62 may be arranged behind the hologram disk 10 as a condensing optical means. Further, the hologram lens 19 may be provided with a uniform scanning characteristic. As described above, various combinations other than the above are possible for the irradiation optical unit and the condensing optical unit. By doing so, the hologram disk 10
Fluctuations in the diffraction angle of the hologram disc 10 caused by the eccentricity of the hologram disc and the wavelength fluctuation of the laser light source, and fluctuations in the diffraction angle caused by the surface of the hologram disc 10 can be compensated.
Further, a good image can be formed.

Although the relief depth in the hologram facet 12 is not limited, its diffraction efficiency may be 30% or less. In the surface relief type hologram, if the diffraction efficiency is 30% or less, the depth of the relief can be made smaller than the pitch, and duplication by injection molding or the like becomes possible. Can be provided.

A semiconductor laser 1 is used as a laser light source.
It is not limited to 5, and for example, a gas laser, a solid laser, or the like may be used. Alternatively, the second harmonic of these lasers may be used.

[0022]

As is apparent from the above description,
In the optical scanning device according to the first aspect, even if the laser beam reflected by the hologram facet is reflected by the incident surface, the laser beam does not re-enter the hologram facet because the hologram disk is thick. Thereby, generation of a ghost image and noise is suppressed, and an adverse effect on image quality can be avoided. Ma
A hologram disc near the hologram facet;
Lightweight because the thickness of the metal is thicker than other parts
And high-speed rotation can be realized.

In the optical scanning device according to the present invention, the width of the hologram facet in the radial direction is substantially equal to the radial spot diameter of the incident laser light on the hologram facet. The generation of ghost images and noise is suppressed even on a disc, and adverse effects on image quality can be avoided.

[Brief description of the drawings]

FIG. 1 is a side view of an essential part for explaining an embodiment of an optical scanning device of the present invention.

FIG. 2 is an explanatory diagram showing a relationship between a hologram and a laser beam.

FIG. 3 is a sectional view of a main part showing a relationship between a hologram facet and a laser beam.

FIG. 4 is an explanatory diagram showing a relationship between a hologram facet and a laser beam in another embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a relationship between a hologram facet and a laser beam in one embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a relationship between a hologram facet and a laser beam in another embodiment of the present invention.

FIG. 7 is an explanatory diagram showing a relationship between a hologram facet and a laser beam according to another embodiment of the present invention.

FIG. 8 is an explanatory diagram showing a relationship between a hologram facet and a laser beam according to another embodiment of the present invention.

FIG. 9 is a side view of a main part showing a configuration of a conventional optical scanning device.

FIG. 10 is an explanatory diagram showing a relationship between a hologram facet and laser light in a conventional optical scanning device.

[Explanation of symbols]

 Reference Signs List 10 hologram disk 12 hologram facet 15 semiconductor laser 16 collimator lens 17 cylindrical lens 18 incident laser beam 19 hologram lens 22 rotation driving means 40 scanning line

Claims (2)

(57) [Claims] 1. A laser light source that emits laser light, irradiation optical means that uses the laser light from the laser light source as a predetermined incident laser light, and a plurality of hologram facets formed on one surface and incident on the other surface A hologram disk that transmits the incident laser light from the irradiation optical means and diffracts the incident laser light by the hologram facet formed on the one surface; and a center of rotation of the hologram disk. A rotation drive unit for rotating a hologram disc, wherein the hologram disc is provided with the hologram facet.
The thickness of the hologram disk in the vicinity is
It is formed larger than the thickness of the other portion of the arm disc, among the incident from the other surface the incident laser light, the laser light reflected on the other face again and reflected by the hologram facet to said hologram facet An optical scanning device having a thickness so as not to be incident. 2. The optical scanning device according to claim 1, wherein a radial width of the hologram facet is substantially equal to a radial spot diameter of the incident laser light on the hologram facet. apparatus.