JPH0481808A - beam scanning device - Google Patents

Abstract

PURPOSE:To allow constant speed linear scanning with high accuracy by controlling the rotating angle of a rotating mirror by the beam position detection signal obtd. by detecting the deflection direction of a deflected laser beam for monitoring. CONSTITUTION:A main incident laser beam 22 is made incident diagonally on the rotating mirror 10 and is reflected plural times; thereafter, this laser beam is emitted from the rotating mirror 10. On the other hand, the laser beam for monitor is collimated by a collimating lens 118 to collimate laser beams which are reflected and deflected by the rotating mirror 10 and are directed to a beam position detector 108, by which the beam position is detected. The deflection angle to which the main laser beam is subjected is larger by the number of times reflected by the rotating mirror 10 as compared with the angle of the deflection which the laser beam for monitor receives. The constant speed scanning is easily executed if the beam position detection signal is inputted to a driving system control circuit 18a for controlling laminated piezoelectric actuators 18, 20 and the actuators 18, 10 for driving the rotating mirror 10 are subjected to feedback control by the beam position detection signal, i.e. angle monitor value.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is applicable to laser beam printers, engraving type laser marker devices, facsimiles, barcode readers, optical card readers, laser microscopes, laser micros, optical switches, optical This invention relates to a light beam scanning device used in exchangers and the like.

[Prior Art] Conventionally, galvano mirror scanners have been used as positioners in engraving-type laser marker devices that draw characters, figures, etc. while moving high-output pulsed laser light using a positioner, and in laser beam printers, etc. A polygon mirror scanner is used as a beam scanning device.

However, since the galvanometer mirror scanner uses a moving magnet or a moving coil as its drive system, it consumes a lot of power, has difficulty in high-speed scanning, and is large in size including a detection system for detecting the rotation angle.

In addition, since a polygon mirror scanner is a polygon mirror that rotates at a constant speed, if the laser beam deflected by the scanner is condensed and irradiated directly onto a flat paper surface through an objective lens placed in front of the paper surface, the laser light will not be reflected on the paper surface. f-sin θ above
- Scanning is performed at a speed expressed by dθ/dt, so it is no longer a uniform linear scan. Here, f is the focal length of the objective lens, θ is the deflection angle, and dθ/dt is the deflection angular velocity. On the other hand, since the recording format required in conventional laser beam printers is constant-velocity linear scanning, polygon mirror scanners usually operate at a scanning speed of f-sinθ・dθ/dt.
・Special f to convert to uniform linear scanning of θ・dθ/'dt
It had to be used in combination with a θ lens system.

As a method of compensating for these drawbacks, a scanning mirror consisting of a fixed mirror, a rotating mirror having a rotating shaft opposite to the fixed mirror, and a drive system that allows the rotating mirror to rotate back and forth and whose rotation angle can be controlled is proposed. and an arcuate distortion correction lens system disposed on the exit side of the scanning mirror section, and the laser beam incident on the scanning mirror section is multiple-reflected in a zigzag pattern between the rotating mirror and the fixed mirror. A beam scanning device has been proposed in which the arcuate distortion occurring in the laser beam is corrected by the arcuate distortion correcting lens system after the laser beam is deflected and exits the scanning mirror section. Alternatively, in the above configuration, the fixed mirror is replaced with a second minute angle rotating mirror having a rotation axis perpendicular to the rotation axis of the rotating mirror, and the arc distortion correction lens system is omitted, and the second A light beam scanning device has been proposed in which a minute angle rotating mirror is rotated by a minute angle in synchronization with the control of the rotation angle of the rotating mirror to correct arcuate distortion of the laser beam.

In the beam scanning device having the above configuration, the incident laser beam is deflected by the number of multiple reflections times the deflection angle of the rotating mirror, so for example, if the number of multiple reflections is 10, the laser beam is deflected by ±30'. To do this, rotate the mirror by ±1.5°.
It would be a good thing if it was deflected. Therefore, a multilayer piezoelectric actuator that is small, has low power consumption, and can operate at high speed can be used as a drive system, and by controlling its voltage or injected charge, it is possible to rotate the rotating mirror with fθ characteristics. You can omit it and scan at constant speed. However, the laser light emitted from the scanning mirror section is distorted in an arcuate manner, so scanning is not performed in a straight line. The distortion is corrected by an arcuate distortion correction lens system placed at the exit of the scanning mirror section, and the laser beam is finally scanned in a constant velocity straight line on the target scanning surface. Furthermore, the second configuration described above has the advantage that the arcuate distortion correction lens system can also be omitted.

[Problems to be Solved by the Invention] However, since the laminated piezoelectric actuator has strong hysteresis and has the characteristic of slowly drifting (creep phenomenon) when a constant voltage is applied, it is difficult to perform uniform linear scanning with high accuracy through voltage control. The problem was that it was difficult. On the other hand, although injection charge control can greatly improve the accuracy of uniform linear scanning, it is still difficult to achieve the single-stroke performance of uniform linear scanning required for A3 specification laser beam printers, etc. There was a problem.

Furthermore, even with actuators other than laminated piezoelectric actuators, there is no means to accurately monitor the amount of displacement within the actuator, making it difficult to achieve highly accurate uniform linear scanning.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a light beam scanning device that can perform highly accurate uniform-velocity linear scanning.

[Means for Solving the Problems] In order to achieve this object, the present invention includes a fixed mirror, a rotating mirror having a rotating shaft opposite to the fixed mirror, and a rotating mirror that causes the rotating mirror to perform reciprocating rotational motion. In a light beam scanning device having a scanning mirror section including a drive system whose angle can be controlled, and an arc distortion correction lens system disposed on the exit side of the scanning mirror section, a monitoring laser light source and a monitoring laser light source are provided. It has a beam position detector that detects the deflection direction of the monitoring laser beam emitted from the light source, reflected and deflected by the rotating mirror, and the rotating mirror is rotated by the beam position detection signal obtained from the beam position detector. This is a configuration that controls the angle.

Or, without performing feedback control of the rotating mirror as described above,
The rotating mirror is allowed to freely scan, and instead, the position to be printed or laser marked is determined based on the beam position detection signal, and the beam position detection signal is sent to the control circuit of the main laser light source in order to add intensity modulation to the main laser beam. This is the configuration to send.

[Function] In the light beam scanning device of the present invention having the above configuration,
The monitor laser light source is continuously oscillated without being intensity modulated, and the deflection angle of the monitor laser light is constantly monitored, so the deflection angle of the main laser light is also constantly monitored. , feedback control is applied to the rotating mirror drive system based on the angle monitor value, and highly accurate uniform velocity linear scanning can be easily achieved.

Alternatively, if intensity modulation is applied to the main laser beam based on the angle monitor value, highly accurate printing or marking can be easily achieved.

[Example] Hereinafter, an example embodying the present invention will be described with reference to the drawings.

FIG. 11 is a diagram illustrating an embodiment of the beam scanning device of the present invention, in which the incident main laser beam 22 is obliquely incident on the rotating mirror 10, receives the first reflection, is directed toward the fixed mirror 14, and is directed to the fixed mirror 14. , and is again directed toward the rotating mirror 10, where it is reflected a second time.

Thereafter, the light is similarly reflected several times before being emitted from the rotating mirror 10. The rotating mirror 1o is attached to a rotating shaft 12, and the rotating shaft 12 is rotated back and forth under the force of a couple by two laminated piezoelectric actuators 18 and 20. Further, the rotating mirror 10 has a trapezoidal shape with the portion not hit by the laser beam cut off in order to reduce the driving load.

On the other hand, the monitoring laser beam emitted from the monitoring laser light source 120 is collimated into a parallel laser beam by the collimating lens 118, directed to the rotating mirror 10, reflected and deflected there, and directed to the beam position detector 108, where the beam is The position is detected. The beam position detector 108 is a linear CCD, a semiconductor beam position detector (PSD, position 5ens)
tive detection, etc. The deflection angle that the main laser beam receives is twice the number of times it is reflected by the rotating mirror 10 compared to the deflection angle that the monitor laser beam receives, so it is four times as large in the case of Figure 1, but this relationship is accurate. Therefore, as shown by the solid line in FIG.
Highly accurate uniform speed scanning can be easily achieved by applying feedback control to the laminated piezoelectric actuator 18, 20 that drives the rotating mirror 10 using the beam position detection signal, that is, the angle monitor value.

Alternatively, as shown by the dotted line in FIG.
The beam position detection signal of 08 is sent to the main laser light source control circuit 22a.
It is also possible to perform highly accurate printing and marking by inputting the input into the main laser beam 22 and applying intensity modulation to the incident main laser beam 22 using the beam position detection signal, that is, the angle monitor value.

The above constitutes the scanning mirror section 38, but the scanning mirror section 3
Since the main laser beam 24 to be deflected emitted from the main laser beam 24 has an arcuate distortion, it is then incident on an arcuate distortion correction lens system (not shown), the arcuate distortion is corrected, and the target scanning surface is This means that linear scanning is performed at a uniform speed with high accuracy.

In the embodiment shown in FIG. 1 above, the fixed mirror 14 is changed to a small-angle rotating mirror, and the small-angle rotating mirror is synchronized with the rotating mirror 10 around a rotation axis perpendicular to the rotation axis 12 of the rotating mirror 1o. As another embodiment of the light beam scanning device, a configuration in which the arcuate distortion is corrected by rotating the lens by a minute angle and the arcuate distortion correction lens system is omitted may be considered.

FIG. 2 is a diagram illustrating an example in which the beam scanning device of the present invention is applied to a laser marker. In this FIG. 2, a high-power pulsed laser light source (YAG, carbon dioxide laser, etc.) 52
The main laser beam emitted and the assist visible laser light source (H
The monitor laser beam emitted from the e-Ne laser, visible semiconductor laser, etc.) 120 has its optical axis aligned by a gicroic mirror 118, and is incident on a large-diameter optical fiber 56 with a core diameter of about 400 μm through a condensing lens 54. and transmitted to the laser marker head section 122. The other end of the large diameter optical fiber 56 is a laser marker head section 122 (not shown).
The main laser beam and the assisting visible laser beam, which are fixed to the frame of the machine and are emitted from a large-diameter optical fiber 56 and whose optical axes match, are once focused onto the object to be marked 62 by a condenser lens 58. After being converted into a circular laser beam, the laser beam passes through the cylindrical lens 46 and is adjusted so that only the beam diameter in the feeding direction of the marking object 62 shown by the arrow in FIG. 2 is focused within the scanning mirror section 38. rotating mirror 10
is attached to a rotating shaft 12, and the rotating shaft 12 is rotated back and forth under the force of a couple by two laminated piezoelectric actuators 18 and 20, and the main laser beam and monitor laser beam are deflected, and the scanning mirror section 38 is emitted, passes through an arcuate distortion correction cylindrical mirror 60, and is focused on a marking object 62, and the assisting visible laser beam is
Used to visually confirm the laser marking position.

On the other hand, the monitoring laser beam emitted from the monitoring laser light source 120 disposed within the laser marker head section 122 is collimated into a parallel laser beam by the collimating lens 118, and is directed to the rotating mirror 10, where it is reflected and deflected to determine the beam position. The light beam is directed to a detector 108 and its position is detected.

2 depending on the beam position detection signal, that is, the angle monitor value.
By applying feedback control to the laminated piezoelectric actuators 18 and 20, highly accurate isostray ray scanning can be easily achieved.

Alternatively, accurate laser marking can be easily achieved by controlling the pulse oscillation of the high-output pulse laser light source 52 using the beam position detection signal, that is, the angle monitor value.

In addition, when applying the light beam scanning device in another embodiment in which the fixed mirror 14 described above is changed to the minute angle rotating mirror 34,
The cylindrical lens 46 can be omitted, and the circular distortion correction cylindrical mirror 60 may be a plane mirror.

Above, embodiments in which the present invention is applied to a laser marker have been described in detail based on the drawings, but in addition to the above, the present invention is applied to a laser beam printer, a facsimile, a barcode reader, an optical card reader, a laser microscope, a laser micro, an optical switch, It can also be suitably applied to optical exchangers and the like. Moreover, the present invention can also be implemented in other embodiments. For example, each of the minute angle rotating mirrors shown in FIGS. Applying a couple force to the shaft 12 2
The laminated piezoelectric actuators 18 and 20 can be made with just one laminated piezoelectric actuator by using an appropriate rotation bearing, or can be combined with an angle expanding mechanism using a lever mechanism, etc., to meet the requirements of the laminated piezoelectric actuator. It is also possible to adopt a configuration that reduces the amount of drive performed. In addition to the laminated piezoelectric actuator, the actuator can also be a moving magnet, a moving coil, a piezoelectric element with electrodes attached to make a torsional movement, or a Terfenol-D
It is possible to use giant magnetostrictive alloys, such as typified by giant magnetostrictive alloys, or hydraulic, pneumatic, thermal deformation, etc. Although not illustrated, the present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art.

[Effects of the Invention] As is clear from the detailed description above, according to the present invention, it is possible to provide a light beam scanning device capable of highly accurate uniform speed linear scanning.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram showing the structure of an embodiment embodying the present invention, and FIG. 2 is a schematic block diagram showing the structure of a laser marker to which the light beam scanning device of the present invention is applied. In the figure, 10 is a rotating mirror, 12 is a rotation axis of the rotating mirror, 14 is a fixed mirror, 18 is a first laminated piezoelectric actuator, 20 is a second laminated piezoelectric actuator, 38 is a scanning mirror section, 1
02 is a monitor laser beam, 104 is a main laser beam, 108
1 is a beam position detector, and 120 is a monitoring laser light source.

Claims (1)

[Scope of Claims] 1. A scanning mirror unit consisting of a fixed mirror, a rotating mirror having a rotation axis opposite to the fixed mirror, and a drive system whose rotation angle can be controlled to rotate the rotating mirror in a reciprocating motion; a circular distortion correction lens system disposed on the exit side of the scanning mirror section, and the main laser beam incident on the scanning mirror section undergoes multiple zigzag reflections between the fixed mirror and the rotating mirror. A beam scanning device characterized in that the arcuate distortion of the main laser beam that is received and deflected and that occurs at that time is corrected by the arcuate distortion correction lens system, a monitoring laser light source; and a beam position detector that detects the deflection direction of the monitoring laser beam that is emitted, reflected and deflected by the rotating mirror, and the rotation angle of the rotating mirror is determined by the beam position detection signal obtained from the beam position detector. A beam scanning device characterized by controlling. 2. A beam scanning device according to claim 1, wherein a beam position detection signal obtained from said beam position detector is sent to a control circuit of a main laser light source.