JPH0480708A - Light beam scanning device - Google Patents

Abstract

PURPOSE:To make a light beam scan with high accuracy by providing a light beam position detector which detects the position of monitor laser light passed through an optical filter. CONSTITUTION:A fixed mirror 14 is provided with a thin line type transmission part 112, the optical filter 106 which extracts the monitor light from laser light is provided behind the transmission part 112, and the light beam position detector 108 which detects the position of the monitor laser light 102 passed through the optical filter 106 is provided. In this case, a monitor laser light source is continuously oscillated without being intensity-modulated and the deflection angle of the monitor laser light 102 is monitored at all times. Consequently, the angle to be deflected of main laser light 104 is also monitored at all times, so the driving system 30 for a rotary mirror 10 is brought under feedback control based upon the angle monitor value to easily realize the equal-speed linear scan with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a light beam scanning device used in a laser beam printer or the like.

[Conventional technology]

Conventionally, a part of a scanning mirror consists of a fixed mirror, a rotating mirror having a rotating shaft opposite to the fixed mirror, and a driving means that rotates the rotating mirror reciprocatingly around the rotating shaft and whose rotation angle can be controlled. The laser beam incident on a part of the scanning mirror is multiple-reflected in a zigzag pattern between the rotating mirror and the fixed mirror,
A light beam scanning device with a biased configuration was disclosed in Japanese Patent Application Laid-Open No. 61-2155.
It is described in No. 16 etc.

Such a conventional technique will be explained with reference to FIG. 5. In FIG. 5, reference numeral 101 is a rotating mirror, which is attached to be rotatable about a rotation center 103.

The rotating mirror 101 is a multilayer piezoelectric actuator (PZ
It was rotating by T).

On the other hand, a fixed mirror 104 is arranged opposite to this,
The light emitted from the laser beam generator 105 is transmitted to the rotating mirror 103.
The laser beam is first reflected by the fixed mirror 104, and is then reflected multiple times in a zigzag pattern so that the laser beam is deflected.

After that, for example, in a laser marker device, the surface to be marked is irradiated with a deflected laser beam to mark the surface.

When marking, in order to understand the position of the laser beam on the marking surface, the voltage applied to the laminated piezoelectric actuator or the amount of charge injected into the PZT is monitored to determine where on the marking surface the laser beam hits. was judging. PZT can be considered a type of capacitor, and the amount of expansion and contraction is proportional to the amount of charge stored in the capacitor if the load is constant.

The positional accuracy of each point marked in this way depends on the control accuracy of the PZT.

[Problem to be solved by the invention]

However, according to the above-mentioned conventional technology, there is a problem in that the thinner the marking, the more difficult it is to achieve this accuracy in determining the location where the laser beam hits the marking surface.

Furthermore, even with actuators other than laminated piezoelectric actuators, there is a problem in that it is difficult to achieve highly accurate beam scanning without a means to accurately monitor the position of the laser beam.

The present invention has been made to solve the above-mentioned problems, and its purpose is to provide a highly accurate light beam scanning device.

[Means to solve the problem]

The present invention having the above objects includes: a fixed mirror, a rotatable rotating mirror facing the fixed mirror, a drive unit for rotating the rotatable rotating mirror, and a drive unit for rotating the rotatable rotating mirror; In a light beam scanning device that performs beam scanning after multiple reflections and deflections, a fixed mirror is provided with a thin line-shaped transmitting section, and an optical filter is installed behind the transmitting section to extract monitor light from the laser beam. Equipped with a beam position detector to detect the position of the monitoring laser beam.

C Effect] In the beam scanning device of the present invention having the above configuration, the monitoring laser light source is not intensity-modulated (is continuously oscillated, and the deflection angle of the monitoring laser light is constantly monitored; Therefore, since the deflected angle of the main laser beam is also constantly monitored, feedback control is applied to the drive system of the rotating mirror based on the angle monitor value, making it possible to easily achieve highly accurate uniform-velocity linear scanning. By applying intensity modulation to the main laser beam using the angle monitor value, highly accurate printing or marking can be easily achieved.The accuracy mainly depends on the accuracy of the beam position detector.

〔Example〕

Embodiments embodying the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram illustrating an embodiment of the beam scanning device of the present invention, in which the incident main laser beam 22 whose optical axis is aligned in advance
The incident monitoring laser beam 100 is obliquely incident on the rotating mirror 10, undergoes the first reflection, is directed to the fixed mirror 14, is reflected by the fixed mirror 14, is directed again to the rotating mirror 10, and is then reflected for the second time. receive a reflection. Thereafter, the light is similarly reflected several times before being emitted from the rotating mirror 10. The rotating mirror 10 is the rotating shaft 1
2, and the rotating shaft 12 is subjected to a couple by two laminated piezoelectric actuators 18.2o so as to be rotated back and forth. 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. The fixed mirror 14 is provided with a thin line-shaped transmission section 112, behind which an optical filter 106 and a beam position detector 108 are arranged. Of the monitoring laser beam 102 and the main laser beam 104 that have passed through the portion 112, the main laser beam 104 passes through the optical filter 106.
The beam position of only the monitoring laser beam 102 is detected by the beam position detector 108. The beam position detector 108 is, for example, a linear CCD, a semiconductor beam position detector (PSD, position 5ensi), etc.
tivedNector), etc. and,
The beam position detector 108 is connected to the drive system control circuit 3o and the main laser light source control circuit 31. Referring to FIG. 1, the light beam position detected by the light beam position detector 108 is
Since it is proportional to the deflection angle of the main laser beam 24 to be deflected, feedback control is applied to the two laminated piezoelectric actuators that drive the rotating mirror 10 using the beam position detection signal of the beam position detector 108, that is, the angle monitor value. Highly accurate uniform speed scanning can be easily achieved.

That is, the position on the marking surface 63 that is hit by the laser beam is determined based on which position on the linear CCD as the beam position detector 108 is hit by the monitoring laser beam whose optical axis is aligned with that of the marking laser.

Next, an example of marking the first column, the nth column, and the 2048th column with vertical lines will be described with reference to FIG. 2. In this case, the marking laser is pulsed at row 1, column 1, row 1, column n, row 1, row 2048, and row 1, row m, column m, row m, row 2048. This judgment is made by using the beam position detector 10 to determine whether or not the laser oscillates at the 1st row and 1st column.
It is judged based on the signal from 8, and if it is in the 1st row and nth column, it oscillates a laser beam, and if it is not, it moves to the next column. If it is determined that the beam position detector 108 has reached the 2048th column,
A laser beam is emitted at that position.

Highly accurate printing and marking can also be performed by applying intensity modulation to the incident main laser beam 22 using the beam position detection signal of the beam position detector 108, that is, the angle monitor value.

The above constitutes the scanning mirror part 38, and the scanning mirror part 3
Since the deflected main laser beam 24 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 is performed. A uniform linear scan is performed on the surface with high precision.

FIG. 4 is an explanatory diagram illustrating an example in which the beam scanning device of the present invention is applied to a laser marker. In FIG. 4, a high-power pulsed laser light source (YAG, carbon dioxide laser, etc.) 52
The main laser beam emitted and the monitoring laser light source (He-N
The monitor laser beam emitted from the laser beam emitted from the laser beam (e.g., e-laser, visible semiconductor laser, etc.) 120 is aligned with its optical axis by the dichroic mirror 118, and is incident on the large-diameter optical fiber 56 with a core diameter of about 400 μm through the condensing lens 54, and is directed to the laser marker head. The data is transmitted to the section 102. The other end of the large diameter optical fiber 56 is fixed to the machine frame of the laser marker head section 102 (not shown), and the large diameter optical fiber 56 is emitted.
The main laser beam and the monitoring laser beam, whose optical axes are aligned, are first focused on the object to be marked 62 by the condensing lens 58, and are turned into laser beams with a circular cross-sectional shape. Marking object 6 indicated by arrow
Only the beam diameter in the two feed directions is adjusted so that it is focused within the scanning mirror portion 38. The 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 the monitoring laser beam are deflected. The light is emitted from the scanning mirror section 38, passes through the circular arc distortion correction cylindrical mirror 60, and is focused onto the marking object 62. Here, the beam position of a part of the monitoring laser beam is detected by the beam position detector, and therefore the beam position of the main laser beam is also detected, so the beam position detection signal, that is, the angle monitor value, is used to detect the beam position of the main laser beam. By applying feedback control to the laminated piezoelectric actuators 18 and 20, highly accurate uniform stray ray scanning can be easily achieved. Or a beam position detection signal,
In other words, depending on the angle monitor value, the high output pulsed laser light source 5
Precise laser marking can also be easily achieved by controlling the pulse oscillation of step 2.

The embodiments in which the present invention is applied to a laser marker have been described in detail with reference to the drawings, but other applications include laser beam printers, facsimiles, barcode leagues, optical card readers, laser microscopes, laser micros, optical switches, and optical exchanges. It can also be suitably applied to vessels etc. Moreover, the present invention can be implemented in other embodiments. Also, for example,
Each of the micro-angle rotating mirrors shown in FIGS. 1 and 2 may have a simple rectangular shape instead of a trapezoidal shape, as long as the drive system has sufficient driving capacity, or the rotating shaft shown in FIG. The two laminated piezoelectric actuators 18 and 20 that provide a couple force to the
It is also possible to use the piezoelectric actuator individually, or it may be combined with an angle enlarging mechanism using a lever mechanism or the like to reduce the amount of drive required of the laminated piezoelectric actuator. In addition to laminated piezoelectric actuators, we also use moving magnets,
Alternatively, a moving coil, or a piezoelectric element with electrodes attached for torsional motion, or a Terfeno
Giant magnetostrictive alloys such as LD, hydraulic pressure, air pressure, thermal deformation, etc. can be used. Although not illustrated, the present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art.

〔Effect of the invention〕

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

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram for explaining the configuration of the first embodiment of the image forming apparatus of the present invention, FIG. 2 is an explanatory diagram of the operation of the image forming apparatus of the present invention, and FIG. 3 is a detailed diagram of the thin line transparent portion. FIG. 4 is an explanatory diagram illustrating an example of application to a laser marker, and FIG. 5 is a perspective view of a conventional image forming apparatus. 10...Rotating mirror 12...Rotating mirror rotation axis 14...Fixed mirror 18...First laminated piezoelectric actuator 20...Second laminated piezoelectric actuator 22...Incoming main laser beam 24...・・Deflected main laser beam 34 ・・Micro-angle rotating mirror 36 ・・Rotating shaft 38 of the small-angle rotating mirror ・・Scanning mirror part 46 ・・Cylindrical lens 52 ・・・Pulse laser oscillator (YAG, carbon dioxide) gas, etc.) 54...Condensing lens 56...Large diameter optical fiber 60...Circular distortion correction cylindrical mirror 62...
Object to be marked 100...Laser beam for incident monitoring 02...Laser beam for monitoring 04...Main laser beam 06...Optical filter 08...Beam position detector 10...Beam position detector Detection surface 12...Thin linear transmission portion 14...Glass base 16 of a fixed mirror or minute rotating mirror...Gold deposition surface 18...Dichroic mirror 20...Laser light source for monitoring 22...Laser marker head Department

Claims (1)

[Claims] A fixed mirror, a rotatable rotating mirror facing the fixed mirror, a drive unit for rotating the rotatable rotating mirror, and a beam incident on the fixed mirror, which is reflected multiple times between the fixed mirror and the rotating mirror, and then deflected. In a beam scanning device that performs beam scanning, a thin line-shaped transparent part is provided on a fixed mirror, an optical filter is installed behind the transparent part to extract the monitor light from the laser beam, and the position of the monitor laser beam that has passed through the optical filter is detected. 1. A beam scanning device characterized by being provided with a beam position detector.