JPH04291314A - Laser beam scanning device - Google Patents

Abstract

PURPOSE:To control the rotating speed of a motor, which rotates a laser beam diffraction disk for diffracting a laser beam, with high accuracy. CONSTITUTION:The laser beam scanning device consists of the laser beam diffraction disk 1 where the laser beam from a laser light source 3 is made incident on a laser beam diffraction part to scar a photosensitive body 3 with the diffracted and projected laser beam, the motor 4 which rotates the laser beam diffraction disk, 2 motor driver 5 which applies a driving voltage to the motor 4 to drive and rotate the motor, a synchronizing signal detection part 6 which detects a write position as a synchronizing signal with the laser beam projected by each laser beam diffraction part of the laser beam diffraction disk 1, a voltage conversion part 7 which converts a voltage corresponding to the period of the synchronizing signal detected by the synchronizing signal detection part 6, and a comparator 8 which compares the voltage V1 outputted by the voltage conversion part 7 with a reference voltage V0 and outputs a difference output; and the motor driver 5 is controlled with the difference voltages from the comparator 8 and the driving voltage applied to the motor 4 is so controlled that the motor rotates at a constant speed with high accuracy.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention is used in a laser printer, etc., in which a laser beam is incident on a rotating laser beam diffraction disk and diffracted, and the laser beam emitted from the laser beam diffraction disk is directed onto a photoreceptor in a straight line. The present invention relates to a laser beam scanning device that records a latent image on a photoreceptor by scanning, and particularly to a laser beam scanning device that controls the rotation of a laser beam diffraction disk with high precision.

0002

2. Description of the Related Art A conventional laser beam scanning device using a hologram disk includes a semiconductor laser, a hologram lens that focuses a laser beam from the semiconductor laser, and a laser beam focused by the hologram lens that enters and is diffracted. It consisted of three optical components: a hologram disk that linearly scans a photoreceptor with a laser beam emitted by the
(See Publication No. 08).

More specifically, as shown in FIG. 4, a laser beam from a semiconductor laser 11 that emits a laser beam is focused by a hologram lens 12, and the laser beam focused by the hologram lens 12 is
The surface of the hologram forming disk forming the hologram disk 13 is made incident on a hologram section 13a which is equally divided into eight sections, and by rotating this hologram disk 13 with a motor 14, a laser is diffracted and emitted from each hologram section 13a. The photoreceptor 15 is linearly scanned by the beam.

[0004] The motor 14 for rotating the hologram disk 13 is a highly accurate and expensive motor in order to stabilize the scanning speed of the laser beam on the photoreceptor 15 at a constant level. A specific example of rotating a motor with high precision is to detect the speed of a DC motor (the number of rotations of the rotor) using a speed detector such as an optical rotary encoder or tacho generator, and to detect the number of rotations of the rotor from this speed detector. A signal corresponding to the current is fed back to the motor driver to control the rotational speed of the motor to be constant by increasing or decreasing the drive voltage.

[0005]

[Problems to be Solved by the Invention] In a conventional method for controlling the rotation of a motor that rotates a hologram disk in a laser beam scanning device, a signal voltage obtained in accordance with the rotation speed of the rotor is fed back to the motor driver to control the rotation of the motor. is controlled so that it remains constant. A DC motor is normally used as a motor to rotate the hologram disk. Therefore, a rotary encoder or a tacho generator is required to detect the rotational speed of the rotor, which increases the size of the device and increases the cost. Another problem is that it is difficult to detect the rotation speed of the rotor and control the rotation of the motor with high precision based on this detection.

An object of the present invention is to solve the above-mentioned problems, to make a laser beam from a laser light source incident on a laser beam diffraction disk, and to scan the laser beam that is diffracted and emitted to determine the writing start position ( Provided is a laser beam scanning device in which a motor that rotates a laser beam diffraction disk is controlled with high precision by a synchronization signal detection unit that detects the exposure start position) based on a synchronization signal obtained from the synchronization signal detection unit. It's about doing.

[0007]

[Means for Solving the Problems] In order to solve the above problems, the present invention, as shown in FIGS. 1 and 2, makes a laser beam from a laser light source 2 enter a laser beam diffraction section, diffracts the laser beam, and then diffracts the laser beam. A laser beam diffraction disk 1 that linearly scans a photoreceptor 3 with an emitted laser beam, a motor 4 that rotates this laser beam diffraction disk 1, and a motor that rotates and drives the motor 4 by applying a driving voltage to this motor 4. A driver 5, a synchronization signal detection section 6 that detects the writing start position as a synchronization signal using a laser beam emitted from each laser beam diffraction section of the laser beam diffraction disk 1, and a synchronization signal detection section 6 that detects a synchronization signal detected by the synchronization signal detection section 6. It consists of a voltage converter 7 that converts into a voltage according to the cycle, and a comparator 8 that compares the voltage V1 output from the voltage converter 7 with a reference voltage V0 and outputs a difference voltage. A laser beam scanning device characterized in that the motor driver 5 is controlled by a differential voltage ±ΔV between This is what I did.

Further, the laser beam diffraction disk 1 has a hologram section 1a which is made by equally dividing the surface of the hologram forming disk. A laser beam from a laser light source 2 is incident on the hologram section 1a, and the laser beam is diffracted and emitted. This is a laser beam scanning device using a hologram disk that linearly scans the photoreceptor 3.

[0009]

In the laser beam scanning device according to the present invention, a laser beam from a laser light source 2 is emitted from a laser beam diffraction portion of a laser beam diffraction disk 1 and linearly scans a photoreceptor 3 in a fixed direction. For each scan of this linearly scanned laser beam, the writing start position is detected as a synchronization signal by the synchronization signal detection unit 6, and a voltage V1 corresponding to the period of the detected synchronization signal is generated by the voltage conversion unit 7. A comparator 8 compares V1 with a reference voltage V0 corresponding to the period required for one scan of the laser beam as a reference in advance, and applies the difference voltage ±ΔV to the motor driver 5.
The rotation speed of the motor 4 that rotates the laser beam diffraction disk 1 is controlled with high precision so that the period required for one scan of each laser beam is the same as the period required for one scan of the reference laser beam.

0010

Embodiments Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1, 2, and 3. FIG. 1 is a circuit block diagram showing an embodiment of a laser beam scanning device of the present invention, and FIG.
1 is a schematic perspective view of a laser beam scanning device of the present invention. In these figures, 1 is a laser beam diffraction disk, and in this embodiment, a hologram having a hologram portion 1a in which the surface of the hologram forming disk is equally divided into eight parts. It's a disc. 2 is a laser light source such as a semiconductor laser, 3 is a photoreceptor, and 4 is a motor for rotating the laser beam diffraction disk 1. The laser beam focused by the hologram lens 9 that focuses the laser beam from the laser light source 2 is The photoreceptor 3 is linearly scanned by a laser beam that is incident on the hologram portion 1a, diffracted, and emitted.

5 is a motor driver that applies a driving voltage to the motor 4 to rotate the motor 4; 6 is a synchronization signal detection unit that detects the writing start position of the laser beam for each hologram portion 1a of the laser beam diffraction disk 1; 7 is a voltage conversion unit that converts into a voltage according to the period of the synchronization signal detected by the synchronization signal detection unit 6, which is detected as a synchronization signal;
A comparator 8 compares the voltage V1 output from the voltage converter 7 with the reference voltage V0 from the reference voltage source 10 and outputs a difference voltage. The reference voltage source 10 generates a preset reference voltage V0 according to the period required for linear scanning of the laser beam. Note that the synchronizing signal detecting section 6 is provided with a slit 6a in front of the synchronizing signal detecting section 6 to sharpen the laser beam in order to sharpen the detection peak of the detected synchronizing signal.

Next, the operation of the laser beam scanning device of the present invention will be explained. A laser beam from a laser light source 2 is emitted from a hologram section 1a, which is a laser beam diffraction section of a laser beam diffraction disk 1, and linearly scans a photoreceptor 3 in a fixed direction. The writing start position is detected as a synchronization signal by a synchronization signal detection unit 6 for each scan of this linearly scanned laser beam. In FIG. 3, P1 , P2 , P
3 is the synchronization signal detected by this synchronization signal detection section 6, T
is the period required for one scanning of the reference laser beam, and the period between the synchronizing signals P1 and P2 is T, and the period between the synchronizing signals P2 and
, P3 is the period (T+ΔT), which is Δ due to uneven rotation of the motor 4 from the reference period required for one scan of the laser beam.
An example is shown in which the length is increased by T.

Since the voltage converter 7 generates a voltage according to the period of the synchronizing signal, if the voltage according to the period T is set to V0, which is the same as the reference voltage, the voltage difference from the reference voltage by the comparator 8 becomes zero, The motor driver 5 applies a predetermined voltage to the motor 4 to rotate the motor 4 at a predetermined speed. Also,
The period between synchronization signals P2 and P3 is (T+ΔT),
The voltage converter 7 converts the voltage V1 according to the period (T+ΔT)
Therefore, the difference voltage ±ΔV between the reference voltage V0 and the voltage V1 by the comparator 8 is applied to the motor driver 5, and the period required for one scan of each laser beam is the reference period. The rotational speed of the motor 4 that rotates the laser beam diffraction disk 1 is highly controlled so that it becomes the same as the period T. In the embodiments described above, a hologram disk having a hologram section in which the surface of the hologram forming disk is equally divided into eight parts was explained as a laser beam diffraction disk, but the invention is not limited to this, and a commonly used polygon mirror can be used. It is also possible to apply the present invention to a laser beam scanning device using.

[0014]

[Effects of the Invention] As explained above, in the laser beam scanning device of the present invention, a laser beam from a laser light source is incident on a laser beam diffraction section, and the photoreceptor is scanned in a straight line with the diffracted and emitted laser beam. A laser beam diffraction disk, a motor that rotates the laser beam diffraction disk, a motor driver that applies a driving voltage to the motor to rotate the motor, and a laser that is emitted from each laser beam diffraction section of the laser beam diffraction disk. a synchronization signal detection unit that detects the writing start position using the beam as a synchronization signal;
A voltage conversion unit that converts the synchronization signal detected by the synchronization signal detection unit into a voltage according to the cycle; and a comparison unit that compares the voltage V1 outputted from this voltage conversion unit with a reference voltage V0 and outputs a difference voltage. The laser beam Based on the synchronization signal obtained from the synchronization signal detection unit every time the laser beam is scanned by the diffraction disc, the motor that rotates the laser beam diffraction disc can be controlled with high precision within one rotation, and the laser beam can be The recording quality of the printer used can be improved. Moreover, the motor itself does not need to be very precise or expensive, and the precision of the motor can be supplemented by the electric circuit according to the present invention, and the laser beam scanning device operates with high precision at a relatively low cost. can be provided.

[Brief explanation of the drawing]

FIG. 1 is a circuit block diagram of a laser beam scanning device of the present invention.

FIG. 2 is a schematic perspective view of a laser beam scanning device of the present invention.

FIG. 3 is an explanatory diagram of the operation of the laser beam scanning device of the present invention.

FIG. 4 is a schematic perspective view of a conventional laser beam scanning device.

[Explanation of symbols]

1 Laser beam diffraction disk 1a Hologram section 2 Laser light source 3 Photoreceptor 4 Motor 5 Motor driver 6 Synchronization signal detection section 6a Slit 7 Voltage conversion section 8 Comparator 9 Hologram lens 10 Reference voltage source 11 Semiconductor laser 12 Hologram lens 13. Hologram disk 13a Hologram section 14 Motor 15 Photoreceptor

Claims (2)

[Claims] 1. A laser beam diffraction disk (1) that makes a laser beam from a laser light source (2) enter a laser beam diffraction section, and linearly scans a photoreceptor (3) with the laser beam that is diffracted and emitted; This laser beam diffraction disk (1
), a motor driver (5) that applies a driving voltage to the motor (4) to rotate the motor (4), and a laser beam diffraction section of the laser beam diffraction disk (1). Synchronization signal detection unit (6) that detects the writing start position as a synchronization signal using a laser beam emitted every time.
, a voltage conversion unit (7) that converts the synchronization signal detected by the synchronization signal detection unit (6) into a voltage according to the period, and a voltage V1 outputted from the voltage conversion unit (7) and a reference voltage V0. The motor driver (5) is controlled by the voltage difference ±ΔV from the comparator (8), and the motor (4) is
1. A laser beam scanning device characterized in that the drive voltage applied to the motor is controlled so that the motor rotates at a constant rate with high precision. [Claim 2] A laser beam diffraction disk (1) has a hologram section (1a) in which the surface of the hologram forming disk is equally divided, and a laser beam from a laser light source (2) is incident on the hologram section (1a). 2. The laser beam scanning device according to claim 1, wherein the laser beam scanning device is a hologram disk that linearly scans a photoreceptor (3) with a laser beam that is diffracted and emitted.