JPS6212893B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical scanning device that uses a light beam such as a laser beam and is used in optical printers, facsimile machines, display devices, and the like.

(Prior Art) Conventionally, as this type of optical scanning device, a mechanical optical scanner using a galvano mirror or a rotating mirror, or a non-mechanical optical scanner using an acousto-optic or electro-optic crystal is known.

However, with such an optical scanner that scans a light beam, the light beam scanned on the projection plane has blurred connections and differences in scanning speed due to the difference in projection distance between the scanning center and both ends of the projection plane. This method has disadvantages in that it cannot perform linear plane scanning and cannot obtain high-resolution, homogeneous images.

In order to eliminate such drawbacks, a so-called f
Some have a θ lens inserted to correct image blur and scanning speed deviation. however,
This fθ lens is a combination of a plurality of concave lenses, convex lenses, etc., and has the problem that the design of the lens system is extremely complicated, and it is expensive and cannot be mass-produced.

Therefore, an optical scanning device that uses a rotating hologram without using an fθ lens has been proposed.

FIG. 1 is a configuration diagram showing an example of an optical scanning device using a conventional rotating hologram.

This device optically divides the circumference into a plurality of parts (four parts in this case), and disks 11, 12, 1 on which the same or different types of holograms are recorded.
The rotary hologram 1 has a rotating hologram 1 configured by attaching holograms 3 and 14, and when producing a hologram, light beams 21 and 22 are attached to the rotating hologram 1.
is irradiated so that both beams intersect on the disk, and during reproduction, a light beam 23 is irradiated.

(Problems to be Solved by the Invention) In the conventional device having such a configuration, the reproduction light beam emitted from the rotating hologram 1 is projected onto the projection surface 3, and as the hologram 1 rotates, the reproduction light beam moves along the arrows a and b. As shown in FIG. 1, the light spot oscillates and scanning is performed, but there is a problem in that it results in curved scanning as shown in FIG.

The present invention has been made in view of these problems, and its purpose is to realize an optical scanning device that is capable of linear plane scanning and has a simple configuration.

(Means for Solving the Problems) The present invention that achieves the above object includes a first hologram and a second hologram that rotate in synchronization with each other, and a light beam from a light source that is directed to the first hologram and the second hologram. The first hologram controls the incident angle of the light beam incident on the second hologram so that the light spot on the projection surface scans in a straight line. It is characterized by

(Operation) The incident angle θi of the light beam on the hologram and the diffraction angle θo of the light beam from there are calculated as follows from the principle of diffraction, assuming that the hologram grating pitch is d and the wavelength of the light beam is λ. Become.

−sinθi+sinθo=λ/d Therefore, the light beam from the first hologram is
Incident angle θi when entering the second hologram
By controlling this by the first hologram, the diffraction angle θo of the light beam from the second hologram can be controlled, and the light spot on the projection plane can be linearly scanned.

(Example) FIG. 2 is a perspective view of the configuration of an apparatus according to the present invention, and FIG. 3 is a side view thereof.

In both figures, 1 is a rotating hologram, and in the apparatus of the present invention, this rotating hologram is particularly divided into two types of holograms 1A, 1A, and 1A arranged concentrically.
It is composed of 1B. Further, the holograms 1A and 1B are optically divided into a plurality of parts (here, four parts) on the circumference. 4 is a light source, for example a laser light source is used. Reference numeral 5 denotes a lens that converts the light from the light source 4 into a parallel beam, and is arranged so that the light emitted from this is incident on the first (inner) hologram 1A side. 6 and 7 are both mirrors for optical path conversion, and the first mirror 6 is arranged so that the light that has passed through the first hologram 1A is incident thereon and the reflected light is projected onto the second mirror 7. , the second mirror 7 is arranged so that the light from the first mirror 6 is incident thereon, and the reflected light passes through the second (outer) hologram 1B side and is projected onto the projection surface 3. .

The operation of the apparatus configured in this way will be explained next. The rotating hologram 1 is rotated by a motor (not shown). The light emitted from the light source 4 is turned into a parallel beam by the lens 5, and is incident on the first hologram 1A. First hologram 1A
is the hologram 1A with the incident light as parallel beam light.
It is deflected as shown by the arrow y as it rotates.
Note that the light emitted from the hologram 1A is
At the same time, there is no problem even if the beam is deflected in a direction perpendicular to the y direction and parallel to the hologram 1A. The light emitted from the first hologram 1A enters the second hologram 1B via the first mirror 6 and the second mirror 7,
The light beam passing through this forms an image of a light spot on the projection surface 3. Here, when the incident angle of the light beam incident on the second hologram 1B is constant, the scanning of the light spot on the projection surface 3 is the same as that of the conventional device shown in FIG. 1, as shown by the broken line r. It becomes an arc shape. In this device, the second hologram 1
The angle of incidence of the light beam incident on B changes with the rotation of the first hologram 1A, and the hologram has a change in the angle of incidence of the light beam.
Since it has the function of changing the position of the reproduced image, the light spot on the projection plane 3 scans in a straight line as shown by the solid line l.

That is, if we consider as an example the light beam a, light beam b, and light beam c generated from the first hologram 1A as the hologram rotates, the incident angle of each light beam incident on the second hologram 1B is θa, θb, and θc are different from each other, and this incident angle is created by the first hologram 1A so that the spot of the light beam emitted from the second hologram 1B linearly scans the projection surface 3. . As the hologram 1 rotates, the light beams a, b, and c from the first hologram 1A are incident on the second hologram 1B while changing the incident angle θc → θa → θb, and this second hologram The light that has passed through 1B linearly scans the projection plane 3 in the direction of →→.

FIG. 4 is a block diagram showing another embodiment of the present invention. In this embodiment, the first hologram 1A and the second hologram 1B are each composed of disks having the same shape, and are installed in parallel so that the holograms 1A and 1B are rotated synchronously. be. Further, mirrors 6 and 7 for changing the optical path are arranged between each of these disks.

In this device, a light beam from a light source 4 passes through a first hologram 1A and a second hologram 1B, respectively, and linearly scans a light spot on a projection surface 3. The operation, function and effect are the same as the device shown in FIG.

(Effects of the Invention) As explained above, the device according to the present invention includes a first hologram and a second hologram, and directs a light beam to the first hologram, the second hologram, and the second hologram.
The first hologram controls the incident angle of the light beam that enters the second hologram so that the light spot on the projection surface scans in a straight line. It has various features such as:

(a) It has a simple structure, is easy to manufacture, and is inexpensive.

(b) Mass production is possible.

(c) The rotating parts are lightweight and easy to drive.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an example of an optical scanning device using a conventional rotating hologram, FIG. 2 is a perspective view of the configuration of the device according to the present invention, and FIG. 3 is a side view thereof.
FIG. 4 is a block diagram showing another embodiment of the present invention. 1... Rotating hologram, 1A... First hologram, 1B... Second hologram, 3... Projection surface,
4...Light source, 5...Lens, 6, 7...Mirror.

Claims (1)

[Claims] 1 A first hologram and a second hologram that rotate in synchronization with each other, a means for projecting a light beam from a light source onto a projection surface via the first hologram and the second hologram, An optical scanning device characterized in that the incident angle of the light beam incident on the second hologram is controlled so that the light spot on the projection surface scans in a straight line.