JPS609242B2 - Semiconductor laser scanning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor laser scanning device using a semiconductor laser as a light source, and in particular to a semiconductor laser scanning device that performs scanning by rotating the semiconductor laser itself around the entrance pupil of a light receiving lens. The present invention relates to a scanning device.

Generally, in an image scanning optical system that uses a semiconductor laser as a light source, scanning is performed by modulating the semiconductor laser with an external signal source and passing the output light through a light receiving lens, as shown in Figure 1. It is well known to use a scanning system to scan a light beam and use an imaging lens to record or display on a recording surface or a display surface.

FIG. 2 is a block diagram of the optical system.

That is, the semiconductor laser 2 is driven by the signal output from the signal source 1 to modulate the optical output. A modulated light beam emitted from a semiconductor laser is collimated by a collimator lens 3, deflected by a galvano mirror or a rotating polygon mirror 4, enters an imaging lens 5, and is imaged on a recording surface 6. The recording surface 6 is a cylindrical drum, and can record two-dimensional information by scanning the galvanometer mirror 4 and rotating the recording surface 6. The present invention aims at simplifying and compacting such an image scanning recording (or displaying) optical system. Its feature is that the semiconductor laser itself is given vibrational (or rotational) motion, making it possible to omit the scanning system using a galvano mirror (or rotating polygon mirror). The optical system itself can be made extremely compact by combining the optical system and the imaging lens into one. FIG. 3 shows an embodiment of the present invention, in which a is a top view and a' is a side view.

The semiconductor laser 2 is vibrated about the rotation center 7, and the emitted light from the semiconductor laser enters the entrance pupil of the lens 5. The center of rotation 7 is located at the intersection of the entrance pupil plane of the lens 5 and the optical axis, and the rotation of the semiconductor laser prevents the light flux incident on the lens 5 from being eclipsed by the lens 5. (Figure b) The light emitted from the lens forms an image on the recording surface 6. The lens 5 has a field curvature controlled to a certain value. FIG. 4 is an explanatory diagram of this. The locus of the light source with the entrance pupil as the center of rotation becomes a spherical surface with a radius R, which is converted into a flat surface by the lens 5 at the imaging position (for example, on the drum surface). be.

This means that for Shins 5, the radius of curvature R of the object point and the radius of curvature R' of the bride surface are generally the same as Beppel's relational expression = 庨Q=P (PetZvaISum) where Ni is the index of the optical system and i If the power of the optical system is R→, then the following relationship is satisfied (within the third-order aberration): poison-consonant;p.

In reality, even higher-order aberration correction is required depending on the angle of view, performance, depth, etc. used. If the vibration of the semiconductor laser 2 is constant velocity (linear) with respect to time, the imaging position of the image plane (drum surface) by the lens 5 will be y = b・8...■ However, if the image is designed to satisfy the following condition, the image will be Uniform velocity on the surface can be obtained.

However, the formula ■ applies when the entrance pupil of the lens 5 and the principal point coincide, otherwise y=b-nen-1 (S number 8S on the lid) However, R is the value of the imaging lens. The distance from the entrance pupil position to the object, which is also the radius of curvature of the object.

If S is given to the lens a distortion characteristic given by the distance between the entrance pupil and the principal point, uniform speed scanning of the spot on the recording surface can be obtained.

In FIG. 5, a plurality of semiconductor lasers are provided around a rotation center 7 and rotated at a constant speed to perform image scanning. That is, the light emitted from the semiconductor laser 2 is imaged by the lens 6 onto a recording surface 6 such as a drum. A plurality of semiconductor lasers 2 are arranged at equal intervals around a rotation center 7, and a signal is sent to them so that they emit light only when they are placed on the side opposite to the recording surface 6 with respect to the lens 5. This can be done by using a commutator in a motor etc. to separate the current going to each element, but since a brush etc. is used, the semiconductor laser itself is vulnerable to electric shock, so the following method is better. . That is, as shown in FIG. 5b, a coaxial generator 9 is provided on the shaft 8 of the rotating body, and power is supplied to the semiconductor laser 2 by the generator 9 when rotation is applied from the outside.

Signals are supplied to the semiconductor laser 2 using radio waves or photo signals.
Give it OFF LINE with a coupler. An electronic circuit is installed on the rotating body, and smoothes the power and distributes signals to each element according to the rotation angle. FIG. 6 shows an example using a photocoupler, in which a is a top view and b is a side view.

That is, light emitted from an LED (or semiconductor laser) 10 is imaged by a lens 11 and a mirror 12 onto a light receiving element 12 placed at the center of rotation. However, among the plurality of semiconductor lasers, only one at a predetermined position is configured to emit light (this can be easily achieved using a potentiometer or the like depending on the rotation angle), and the information received by the light receiving element 12 is transmitted to the semiconductor laser. Enters the laser and is modulated. Initially, LED I O is only ON and no information is output. That is, the semiconductor laser 2 is ON.
It rotates while emitting light. The moment this light beam crosses the synchronization light receiving element 15, a synchronization clock pulse is generated. The clock pulses are counted, and when a predetermined number is reached, one line of information is output from the control device 14, causing the LEDIO to blink and modulating the semiconductor laser 2. The output light from the semiconductor laser is imaged on the recording surface by the lens 5, but in order to prevent the light beam from being blocked by the rotating body, an odd number of semiconductor lasers are used, and the surface facing the semiconductor laser is need to be scraped off.

Alternatively, the optical axis of the light emitted from the lens may be bent by a mirror. Although this method has made the optical system simpler and more compact, other features include the fact that the semiconductor laser itself is air-cooled by rotation, which prevents heat from rising, and that it is possible to prevent heat from increasing by using multiple semiconductor lasers. If one element is destroyed, it can be replaced with another element (however, the recording speed will be reduced), but reliability will be improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional semiconductor laser scanning device, FIG. 2 is a schematic diagram of a conventional semiconductor laser scanning device according to the block diagram of FIG. 1, and FIG. 3 is a schematic diagram of a semiconductor laser scanning device of the present invention. 3A is a diagram showing a state where the semiconductor laser is positioned on the optical axis of the imaging lens, FIG. 3A' is a side view of FIG. 3A, and FIG. Fig. 3b is a diagram showing the state in which the semiconductor laser is rotated, Fig. 4 is a diagram showing the locus of the semiconductor laser when it rotates with respect to the lens, and Fig. 5 is a diagram showing the second embodiment of the present invention. , Figure 5a is a top view,
Fig. 5b shows a side view, Fig. 6 shows a writing machine to which the semiconductor laser scanning device of Fig. 5 is applied, Fig. 6a shows a top view, and Fig. 6b shows a side view. . In the figure, 2 is a semiconductor laser, 5 is an imaging lens, 6 is a drum, and 7 is a rotating shaft. Figure 1 Figure 2 Figure 2 Figure 4 Figure 5 Figure 6

Claims (1)

[Scope of Claims] 1. In a semiconductor laser scanning device in which modulated output light from a semiconductor laser is recorded or imaged on a display surface by an imaging optical system, the semiconductor laser is centered around a certain axis. The semiconductor laser is fixed to a semiconductor laser support member that rotates or vibrates with respect to the imaging optical system, and the imaging optical system has an aberration characteristic that images a curved locus of the semiconductor laser into a planar shape. Laser scanning device. 2. The semiconductor laser scanning device according to claim 1, wherein the center of rotation or vibration of the semiconductor laser is located near the intersection of the entrance pupil of the imaging optical system and the optical axis.