JPH05299749A - Optical apparatus - Google Patents

Abstract

PURPOSE:To provide an optical apparatus wherein it is small-sized and lightweight as compared with conventional cases, its power consumption is low and it can provide a laser beam, scanning. CONSTITUTION:A laser beam which is radiated from a semiconductor laser 1 as a light source is passed through a collimator lens 2; it is changed to nearly parallel beams; a liquid-crystal plate 3 is irradiated with them. A plurality of strip-shaped transparent electrodes are formed in the liquid-crystal plate 3. An electrode to which a voltage is to be applied is selected from the electrodes; the voltage is applied to the electrode; the polarization direction of a liquid crystal is changed; its transmission factor is lowered partly. As a result, an arbitrary grating pattern 4 can appear. When the laser beam is passed through the grating pattern 4, the laser beam is subjected to diffraction which is decided by the pitch of the grating. Thereby, the laser beam scanning is possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical device, and more particularly to an optical device for scanning laser light.

[0002]

2. Description of the Related Art Conventionally, as this type of optical device, one shown in FIG. 2 has been known. In such an optical device, the laser light emitted from the semiconductor laser 10, which is the light source, passes through the collimator lens 11 and becomes substantially parallel light. Reference numeral 12 is a polygon mirror that is rotatable around a rotation axis, and has a plurality of mirror surfaces parallel to the rotation axis.
The substantially parallel light that has passed through the collimator lens 11 is applied to the mirror surface of the polygon mirror 12. The laser light applied to the mirror surface is efficiently reflected by the mirror surface. here,
By rotating the polygon mirror 12, the direction of the reflected light can be changed and the laser light can be scanned.

[0003]

In such an optical device, since the polygon mirror 12 is used, high precision is required for processing the mirror surface thereof. Also, the polygon mirror 12
Since a rotating mechanism is required for the device, the device may be complicated and upsized.

Therefore, instead of the polygon mirror method, a hologram scanner method has been proposed in which a laser beam is scanned by a rotating hologram. However, even in this method, since a rotating mechanism is required, it is inevitable that the device will be complicated and large.

[0005]

SUMMARY OF THE INVENTION The present invention comprises a light source that emits laser light, and a diffractive laser light scanning member that is arranged in front of the light source and diffracts the laser light emitted from the light source. In this optical device, the optical scanning member is formed of a transmissive liquid crystal plate, and laser light is diffracted by a grating pattern displayed on the liquid crystal plate.

That is, in the optical device of the present invention, a diffractive laser light scanning member composed of a transmissive liquid crystal plate is arranged in front of a light source that emits laser light, and a laser beam is emitted by a grating pattern displayed on the liquid crystal plate. The gist is to try to change the diffraction angle by performing diffraction and selecting an electrode for voltage application to change the grating pattern.

As the light source in the present invention, a semiconductor laser, a solid-state laser, a gas laser or the like is appropriately used, but a semiconductor laser having features such as being compact and capable of producing a high energy state is more preferable.

[0008]

The optical device according to the present invention does not have the rotating mechanism as in the conventional optical device. Therefore, it becomes smaller and lighter than the conventional one, and it becomes possible to scan the laser beam with low power consumption.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to one embodiment shown in the drawings. The present invention is not limited to this.

In FIG. 1, an optical device D includes a semiconductor laser 1 as a light source, a collimator lens 2 arranged in front of the semiconductor laser 1, and a diffractive laser light scanning arranged in front of the collimator lens 2. And a transmissive liquid crystal plate 3 as a member.

The laser light emitted from the semiconductor laser 1 passes through the collimating lens 2 and then becomes substantially parallel light, which is applied to the liquid crystal plate 3. A plurality of transparent electrodes are formed in a strip shape on the liquid crystal plate 3. When an electrode for applying a voltage is selected from these electrodes and a voltage is applied to the electrode, the polarization direction of the liquid crystal is changed and the transmittance is partially reduced. As a result, an arbitrary grating pattern 4 can appear. When the laser light passes through the grating pattern 4, the laser light undergoes diffraction determined by the pitch (cycle) of the grating. As a result, the laser beam can be scanned.

When the laser light is incident on the liquid crystal at a right angle, the diffraction angle θ of the emitted laser light is generally θ = tan ^-1 (n), where a is the grating pitch and λ is the wavelength of the laser light. .Lamda. / A) (n = 0, 1, 2, ...
…)

As can be seen from this equation, the diffraction angle θ changes by changing the pitch a of the grating pattern 4 on the liquid crystal surface. Therefore, the laser beam can be scanned by changing the pitch a. At this time, as shown in FIG. 1, the 0th-order light 5 with n = 0 passes straight (θ = 0), and therefore cannot be used for scanning. Therefore, as the scanning light, the primary light of 6 or more is used.

In the optical device D, as described above, the laser beam can be scanned without using the conventional rotating mechanism such as the polygon mirror. Therefore, no electric power is required for the rotating mechanism, and it is possible to realize size reduction and weight reduction.

[0015]

Since the optical device according to the present invention is configured as described above, it is smaller and lighter than conventional ones, and it is possible to scan laser light with low power consumption.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of an optical device according to an embodiment of the present invention.

FIG. 2 is a schematic perspective view of a conventional optical device.

[Explanation of symbols]

 1 semiconductor laser (light source) 2 collimating lens 3 liquid crystal plate (laser light scanning member) 4 grating pattern 5 0th order light 6 1st order light

Claims (2)

[Claims] 1. A light source for emitting a laser beam, and a diffractive laser beam scanning member arranged in front of the light source and diffracting the laser beam emitted from the light source, wherein the laser beam scanning member is a transmissive liquid crystal plate. An optical device that is composed of a laser beam and is diffracted by a grating pattern displayed on the liquid crystal plate. 2. The optical device according to claim 1, wherein the light source is a semiconductor laser.