JPH0634910A - Laser scanning optical system - Google Patents

Abstract

PURPOSE:To provide a laser scanning optical system which has small-sized, inexpensive, constitution and tolerance to external vibration and can periodically deflect laser luminous flux in a specific direction. CONSTITUTION:The laser luminous flux is deflected in a specific direction by a couple of deflecting elements 1 and 3 which are arranged on the optical axis closely in the front and rear direction and almost equal in deflection angle. Those deflecting elements are successively rotated in the mutually opposite directions about the optical axis, so the laser luminous flux is deflected through a 1st deflecting element 1 first by a specific angle in the direction determined by the rotation of the deflecting element. This deflected laser luminous flux is then deflected through a 2nd deflecting element 3 by a specific angle in the direction determined by the rotation of the deflecting element. When this deflecting operation is considered divisionally as a vertical and a horizontal component, the horizontal component is canceled at all times and then the laser luminous flux is periodically deflected at perpendicular angles to the optical axis.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a laser scanning optical system,
More specifically, the present invention relates to a laser scanning optical system that performs scanning by periodically deflecting a laser light beam emitted from a laser light source in a predetermined direction.

[0002]

2. Description of the Related Art In such a laser beam scanning optical system,
A laser beam emitted from a laser light source is collimated into a parallel beam, which is then reflected by a mirror that rotates or oscillates periodically such as a polygon mirror or galvano mirror. Laser scanning is performed by deflecting the laser beam.

A laser scanning optical system using a polygon mirror has a drawback that each optical element cannot be arranged in a straight line because the polygon mirror has a reflecting structure and the apparatus becomes large. Although the division angle of the surface must be made small, when the laser beam diameter is large, the polygon diameter must be made large and at the same time the thickness must be made large.

Further, in the laser scanning optical system using the galvano mirror, similarly to the laser scanning optical system using the polygon mirror, there is a disadvantage that each optical element cannot be arranged on a straight line and the apparatus becomes large because of the reflecting structure. is there. Furthermore,
High-speed scanning is difficult because the galvanomirror operates reciprocally. Further, when the beam diameter of the laser is large, it is necessary to make the mirror large, but in that case, there is a problem that since the reciprocating motion is performed, a load due to a large moment of inertia is applied to the rotating shaft.

Further, it is conceivable to deflect the laser light flux electro-optically by using an acousto-optic element instead of deflecting the laser light flux according to such mechanical vibration, but the acousto-optic element is expensive. Therefore, there is a drawback that the entire laser scanning optical system becomes expensive.

[0006]

SUMMARY OF THE INVENTION Therefore, the present invention has been made in order to eliminate the above-mentioned conventional drawbacks, and it is small in size and inexpensive, and is strong against external vibration so that the laser beam is directed in a predetermined direction. An object is to provide a laser scanning optical system capable of periodically deflecting.

[0007]

SUMMARY OF THE INVENTION To solve this problem, the present invention provides a laser scanning optical system for periodically scanning a laser beam emitted from a laser light source in a predetermined direction. A pair of deflection elements, which are arranged close to each other in the front-rear direction on the optical axis from which the light beam is emitted and have substantially the same deviation angle, and a means for continuously rotating the respective deflection elements in opposite directions about the optical axis. A structure is provided in which the laser light flux is periodically deflected in the direction perpendicular to the optical axis at a deflection angle determined by the rotation angle between the deflection elements according to the rotation of the deflection elements.

[0008]

In such a structure, the laser light beam is deflected in a predetermined direction by a pair of deflection elements which are arranged close to each other on the optical axis in the front-rear direction and have substantially the same deviation angle. Since each deflecting element is continuously rotated in opposite directions about the optical axis, the laser beam is first deflected by the first deflecting element in a direction determined by the rotation of the deflecting element by a predetermined angle. The deflected laser beam is subsequently further deflected by a second deflection element by a predetermined angle in a direction determined by the rotation of the deflection element. Considering this deflection action separately for the vertical component and the horizontal component, the laser beam is periodically deflected in the direction perpendicular to the optical axis by always canceling out the horizontal component.

[0009]

The present invention will be described in detail below with reference to the embodiments shown in the drawings.

In FIG. 1, the semiconductor laser 8 has an optical axis L.
The laser arranged above and emitted from the semiconductor laser 8 is collimated by the collimator lens 7. The collimated laser light flux is incident on the deflection optical system. The deflecting optical system includes a first deflecting prism 1 and a second deflecting prism 3, and the deflection angles θ of the first deflecting prism and the second deflecting prism are set to be equal.

The first deflecting prism 1 has a gear portion 2a on its outer periphery.
The second deflection prism 3 is similarly held by the holding frame 4 having a gear portion 4a formed on the outer periphery thereof. The holding frames 2 and 4 are bearings 9 and 10, respectively.
It is rotatably held by. Gear parts 2 of the holding frames 2 and 4
a and 4a mesh with a gear 5 driven by a motor 6, and when the gear 5 rotates by the motor 6, the respective deflection prism holding frames 2 and 4 rotate in opposite rotation directions at the same cycle.

In such a structure, in the initial state, the apex angles of the deflecting prisms 1 and 3 coincide upward as shown in FIG. 2A, which corresponds to the state of FIG. At this time, the laser light beam is deflected by θ by the first deflecting prism 1 and further by θ by the second deflecting prism 3 so that a total of 2θ is deflected. As shown in FIG. It is vertically deflected to 18 points. In FIG. 2, white circles indicate the apex angle direction of the first deflecting prism 1, and black circles indicate the apex angle direction of the second deflecting prism 3.

Subsequently, the respective deflection prisms 1 and 3 are connected to the motor 6
When rotated by 45 ° in the opposite direction as shown by arrows 1a and 3a (B of surface 2) according to the rotation of, the deflection direction and deflection angle of the laser beam incident on the two deflection prisms 1 and 3 are considered as follows. be able to.

In the first deflecting prism 1, the light is deflected by the angle θ in the lower right direction of 45 ° indicated by the arrow 11. If this deflection direction is divided into a vertical component and a horizontal component, θc
It is divided into os (45 °) and θ sin (45 °). Further, in the second deflecting prism 3, the lower left 4 indicated by the arrow 13
A deflection action of an angle θ acts in the 5 ° direction. Also at this time, if the deflection direction is divided into a vertical component and a horizontal component, θco
s (45 °) and θ sin (45 °), but the horizontal component is canceled because the direction is reversed, and the laser beam is deflected by 2θcos (45 °) in the vertical direction. Is closer to the optical axis direction in the direction 20 perpendicular to the optical axis as compared with FIG.

Then, as shown in C of FIG.
When rotated by 0 °, the vertical component disappears and the deflection point 18 coincides with the optical axis L. To explain this in the state of FIG. 1, the laser light flux is deflected by the deflection prism 1 in the direction perpendicular to the paper surface, and subsequently, is deflected by the deflection prism 3 also in the direction perpendicular to the paper surface, and reaches the optical axis L. Equivalent to that. Therefore, the laser light flux is deflected in the vertical direction 20 toward the optical axis.

Further, as shown in FIGS. 2C to 2C, while the deflecting prisms rotate in mutually opposite directions, the horizontal direction is always canceled and the deflecting direction is always the vertical direction 20.
Then, the deflection angle becomes 4θcos (α) (α is the rotation angle of the deflection prism), and the deflection point 18 repeats the periodic scanning of simple vibrations as the deflection prisms 1 and 3 rotate.

According to the embodiment of the present invention, a compact and durable scanning optical system can be supplied, and the deflection direction 20 can be rotated by rotating the entire deflection optical system from a pair of deflection prisms by another mechanism. It will be possible.

In the above-mentioned embodiments, the deflecting prism is used as the deflecting element, but the present invention is not limited to this, and other deflecting elements such as a diffraction grating or a hologram may be used. Of course, the effect of can be obtained.

[0019]

As described above, according to the present invention, a pair of deflection elements, which are arranged close to each other in the front-rear direction on the optical axis from which a laser beam is emitted and have substantially the same deviation angle, and each deflection element. A means for continuously rotating the optical axis in opposite directions to each other is provided, and the laser beam is periodically deflected in the direction perpendicular to the optical axis at a deflection angle determined by the rotation angle between the deflection elements according to the rotation of the deflection elements. Since it is a transmissive structure instead of a reflective structure, the optical element can be arranged on a straight line and the size can be easily reduced. Even if the diffraction phenomenon is taken into consideration with respect to the beam diameter of the laser, the deflection element is twice that diameter Has the largest diameter,
It is advantageous for downsizing, there is no reciprocating motion, so it is possible to speed up.The rotation of the deflection element can be held by bearings with a large diameter, so a thin rotating shaft like a galvanometer mirror is not required, and durability Various effects such as excellent are obtained.

[Brief description of drawings]

FIG. 1A is a configuration diagram showing an optical configuration of a laser scanning optical system of the present invention, and FIG. 1B is a side view thereof.

FIG. 2 is an explanatory diagram illustrating a deflection direction of a laser scanning optical system of the present invention.

[Explanation of symbols]

 1 First Deflection Prism 2 Holding Frame 2a Gear Part 3 Second Deflection Prism 4 Holding Frame 4a Gear Part 5 Gear 6 Motor 7 Collimator Lens 8 Semiconductor Laser 9 Bearing 10 Bearing

Claims (4)

[Claims] 1. In a laser scanning optical system for scanning by periodically deflecting a laser light beam emitted from a laser light source in a predetermined direction, the laser light beam is arranged close to the front-back direction on the optical axis from which the laser light beam is emitted. A pair of deflection elements having substantially the same deviation angle and means for continuously rotating the respective deflection elements in opposite directions about the optical axis, and rotating the laser beam between the deflection elements in accordance with the rotation of the deflection elements. A laser scanning optical system characterized by periodically deflecting in a direction perpendicular to the optical axis at a deflection angle determined by the angle. 2. The laser scanning optical system according to claim 1, wherein the deflection element is a deflection prism, a diffraction grating or a hologram. 3. The deflection means comprises a motor and an idle gear driven by the motor, and the idle gear is meshed with a gear formed on an outer periphery of a holding frame of each deflection element, whereby each deflection is performed in accordance with the rotation of the motor. 2. The elements are continuously rotated in opposite directions to each other.
Alternatively, the laser scanning optical system according to the item 2. 4. The laser scanning optical system according to claim 1, wherein the entire deflection optical system is rotatable to change the deflection direction.