JPH0259712A - Picture forming device - Google Patents

Abstract

PURPOSE:To form a highly accurate oscillation circuit without using any crystal resonator, and to change a frequency in a shot time by generating clocks by using the rotation detecting pulse signal of a polygon motor as a basic signal. CONSTITUTION:An encoder 205 with a slit is fixed to the scanner motor 203 of a rotary polygon mirror 202 and, when the motor is rotated, a photo- interruptor 204 detects the slit and outputs a pulse signal (FG) 207 which detects the rotational speed of the motor to a waveform shaping circuit 206. Then a TACH signal 101 outputted from the circuit 206 is converted and decided to an output voltage v1 by means of a frequency voltage conversion circuit 110 by using the frequency of the TACH signal and an error amplifier 107 decides the value of an output frequency (f) by controlling the input voltage V3 of a voltage-controlled oscillator (VCO) 105. The output signal (f) of the VCO 105 is inputted to a frequency divider 106 where the frequency of the signal (f) is divided and a clock signal F103 which is synchronous to a horizontal synchronizing signal (BD signal) 102 is obtained. Therefore, the frequency of the generated clock can be changed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image forming apparatus that records image information on a recording medium by scanning a light beam.

[Conventional technology]

Generally, in an image scanning recording device that records image information by scanning a light beam modulated with an image signal on a recording medium in the main scanning direction and the sub-scanning direction, for example, the light beam position changes by a reference value in the main scanning direction. Each time, image information is recorded using a modulated light beam.

Conventionally, when recording such an image signal, a basic clock signal for reading out image information from a memory, etc., and a light beam detected at an arbitrary point on the main scan and synchronized with the detection are used. In order to obtain the generated horizontal synchronization signal (clock signal (SCK signal) for detecting abnormalities in the period of the BD double signal, etc.), the crystal oscillator and TTL IC, CM
O5 gate circuits and the like were used.

[Problem to be solved by the invention]

However, in the past, a crystal oscillator was used to generate a clock signal, which had the following drawbacks with respect to changes in the rotational speed of the polygon motor.

(1) Since only a clock signal with a fixed period can be obtained from a single crystal oscillator, changing the frequency requires physically changing the crystal oscillator.

(2) The frequency cannot be changed in the short term.

SUMMARY OF THE INVENTION In view of the above-mentioned points, an object of the present invention is to provide an image forming apparatus that is adaptable to changes in the rotational speed of a polygon motor.

[Means to solve the problem]

In an image forming apparatus that records image information by scanning a light beam on a recording medium, the present invention includes a polygon motor for driving a rotating polygon mirror that scans the light beam, and detects the rotational state of the polygon motor. rotation detection means for
and clock generation means for generating a clock signal in proportion to the rotation detection pulse signal output from the rotation detection means.

[Function] According to the present invention, a pulse signal for detecting the rotation of a polygon motor that drives a rotating polygon mirror that scans a light beam is used without using a crystal oscillator, for example, a voltage controlled oscillator (VCO).
By providing a configuration that generates a clock signal using the , it is possible to change the frequency of the generated clock.Furthermore, since the rotation detection pulse signal is used as the reference signal, it can follow the rotational fluctuations of the polygon motor. becomes possible.

〔Example〕

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 3 is a diagram showing the configuration of the light beam scanning section.

A semiconductor laser 305 is driven by a laser control circuit 306 to emit a light beam. The light beam is scanned onto a photosensitive drum 302 by a rotating polygon mirror 202 rotating at a constant speed, and is transferred onto paper 301 after a developing process and output. In addition, the synchronization signal in the main scanning direction (BD double signal is transmitted to the photodetector 30 provided at a predetermined point on the main scanning axis of the light beam).
4, and is waveform-shaped by a waveform shaping circuit 307 to become a BD signal 102.

The rotating polygon mirror 202 rotates at a constant speed using the circuit configuration shown in FIG. This rotating polygon mirror 202 is fixed to a scanner motor 203, and the scanner motor 203 has an encoder 205 having several slits on a disk.
is fixed, and as the motor rotates, the photointerrupter 204 detects the drift and outputs a pulse signal (FG) 207 for detecting the rotational speed of the motor. The FG signal 207 is subjected to processing such as waveform shaping and frequency division by a waveform shaping circuit 206 and is output. The output TAC1+signal 101 is fed back to the motor control circuit 208. The motor control circuit 208 is composed of a motor rotation control IC such as Toshiba TC9142P, and the scanner motor 203 is in a constant speed rotation state. The TAC11 signal 101 is also supplied to the clock signal generation circuit shown in FIG.

FIG. 1 is a diagram showing a clock signal generation circuit of this embodiment. TAG) I signal 101 is the frequency-voltage conversion circuit 11
0 is converted to voltage. Frequency voltage conversion circuit (F
/V) 110 has the characteristics shown in Fig. 4(A), and as the frequency of the TA(:)l signal increases, the output voltage v
1 rises, and the output voltage V, is determined by the frequency of the TACH signal.

The error amplifier 107 calculates the comparative human power V with respect to the reference human power v1.
, the input voltage v3 of the voltage controlled oscillator (VCO) 105 is controlled so that vI=kv2 (k is a constant). The voltage controlled oscillator (VCO) 105 is shown in FIG. 4(B).
The output frequency f increases as the voltage at the input terminal V increases, and the value of the output frequency f is determined by the voltage value v3 of the input voltage v3.

The output signal f is frequency-divided by a frequency divider 108 to l/n (n is an integer of 1 or more), and a frequency-voltage conversion circuit (F/V) 109
is man-powered. Here, if the frequency f of the output signal f is sufficiently small (n
=1, that is, it is also possible to manually input the signal to the F/V conversion circuit 109 without frequency division. Frequency voltage conversion circuit (F/V) 1
Similarly to the F/V conversion circuit 110, the circuit 09 has the characteristics shown in FIG. 4(B), and changes the output voltage v2 according to a human input signal. Then, the error amplifier 107 has an input terminal vI
It has the characteristics shown in Figure 4 (C) according to +v2,
By applying feedback, v3 is adjusted so that v,=kv2, and the output frequency f is adjusted so that it becomes a specified frequency with respect to the frequency of the TACI+ signal. In other words, it is possible to obtain an output clock f of a specified frequency for any given TACH signal frequency.

The output signal f of the VCO 105 is input to the frequency divider 106,
The frequency is divided by 17m (m is an integer greater than or equal to 1), and the frequency is roughly divided by the frequency divider 1.
06 is reset by the horizontal synchronization signal (BD and other signals 102, and as shown in FIG. 5, the horizontal synchronization signal (BD and other signals 102
A clock signal F 103 synchronized with 2 can be obtained.

In an image scanning recording apparatus such as the present embodiment, such as a laser beam printer, a clock signal F 103 and a horizontal synchronization signal 102 are sent to an external control device. Then, as shown in FIG. 6, the external control device +12 receives the clock signal F.
103 and horizontal synchronization signal (e.

Image data (Video) in synchronization with signal) 102
114 is sent to the printer side. On the printer side, a laser control circuit 306 operates according to the input image data signal (Video signal) 114, and the semiconductor laser 305
is driven to record image information on the photosensitive drum.

In such a configuration, if a rotational fluctuation occurs in the scanner motor z03 (see Figure 3), the TACH signal 101
As shown in FIG. 7(A), the period changes. However, TAC)! Since the clock signal f is generated using the signal 101 as the basic signal, the clock signal f also follows the periodic fluctuation of the TAC) signal as shown in FIG. 7(B).
It changes as shown in . Therefore, the timing signal for outputting image information also fluctuates, and when image information scanned onto a photosensitive drum, for example a vertical line, is output, it becomes a straight line as shown in Figure 5 (C), and image abnormalities such as distortion and image protrusion occur. It doesn't happen.

In addition, the frequency division ratio of the frequency divider ioa is set by the central processing unit (CPLI).
) The period of the image writing clock F103 can be changed by changing it using Ill, a gate circuit, etc. That is, the image density in the main scanning direction can be changed. and central processing unit (CP'tl)
The image density in the main scanning direction can be changed by configuring the external control device 112 to instruct control from 11 (i.e., the image density can be changed in the main scanning direction by can provide a recording device that can be controlled).

Another embodiment of the present invention will be described using FIG. 8.

In the embodiment shown in FIG. 8, similarly to the embodiment shown in FIG. m
The oscillation of VC:0105 is controlled via the error amplifier 107, and a steady frequency f is output. Furthermore, the output f is manually inputted to the frequency divider 106, and the horizontal synchronization signal (BD scratch signal 10
An output clock signal F 103 synchronized with 2 is created.

This output clock signal F is counted and B is output within a specified period.
The BD cycle abnormality detection circuit 80 determines whether the D scratch signal is activated or not.
Detected by 1.

In the BD cycle abnormality detection circuit 801, as shown in FIG.
Count the clock signal F until the signal is input. If the counted number n is within a predetermined numerical value range, it is determined that the BD flaw signal is normal, and if it is outside the predetermined numerical value range, it is determined that the BD flaw signal is abnormal.

In such a configuration, even if the BD same period abnormality occurs due to scanner rotational fluctuations, the clock signal F is generated using the TACH signal as the basic signal, so the clock signal F is generated by following the scanner rotational fluctuations and the signal period T8CI+ times Since the clock signal F also fluctuates following the fluctuation, the BD scratch signal does not become abnormal, and it can be accurately determined that the rotational fluctuation of the scanner has occurred.

Furthermore, the rotation speed of the scanner is determined by the central processing unit CPU 11.
Even if the frequency division ratio of the T8 (:11 signal is changed and manually inputted to the scanner motor control circuit 208), the frequency division ratio of the T8 (:11 signal) is changed under control, as the rotation speed of the scanner is changed.
Since the frequency of the clock signal F is also changed, normal or D abnormality detection can be performed without changing the prescribed numerical value for abnormality determination inside the BD cycle abnormality detection circuit 801. Furthermore, it can be seen that it is not necessary to have a crystal resonator for generating the clock signal F.

Furthermore, by controlling this central processing unit CPt1ll from the external control device 112, the rotation speed of the scanner motor can be easily changed. That is, the image density in the sub-scanning direction is controlled by the external control device 112 so that the central processing unit 1
By controlling only the drive circuit of the scanner motor via 11, the rotation speed can be controlled. Therefore, by changing only the rotation control of the scanner motor under the control of the external control device 112, it is possible to realize a recording apparatus that can easily perform enlargement and reduction in the sub-scanning direction.

Furthermore, in the embodiment shown in FIG.
By changing the image density in the main scanning direction under the control from 12, image information can be enlarged or reduced in the main scanning direction, and roughly has the same configuration as the embodiment shown in FIG. In the recording device, an external control device 11
By controlling from 2, it is possible to realize a recording apparatus that can enlarge and reduce image information in both the main scanning direction and the sub-scanning direction.

(Effects of the Invention) As explained above, according to the present invention, by generating a clock using the rotation detection pulse signal of the polygon motor (TAC11 signal in the embodiment) as a basic signal, high accuracy can be obtained without using a crystal oscillator. Furthermore, by using the above-mentioned pulse signal as a basic signal such as VCO, it is possible to generate images and signals that follow and change even when rotational fluctuations occur in the polygon motor. This makes it possible to eliminate curvature of recorded images due to rotational fluctuations of the polygon motor.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a recording device to which the present invention is applied. FIG. 2 is a diagram showing a scanner motor drive circuit to which the present invention is applied. FIG. 3 is a diagram showing a scanning system to which the present invention is applied. Figure 4 is a diagram showing the characteristics of each circuit, Figure 5 is a diagram showing the operation of the frequency divider 106, Figure 6 is a diagram showing the video signal generation timing of an external device, and Figure 7 is a diagram showing scanner rotation fluctuation. FIG. 8 is a diagram showing the configuration of another embodiment. FIG. 9 is a diagram showing the operation of the BD abnormality detection circuit. ... TAC) I signal, ... BD double signal ... output clock signal F, ... vCOl ... frequency divider, ... error amplifier, ... frequency divider, ... F /V conversion circuit, ...F/V conversion circuit, ...cpu. ...External control device, ...Control signal, ...Video signal, ...Polygon mirror, ...Scanner motor, ...Sensor, ...Encoder, ...Waveform shaping circuit, ...・FG signal, ...Motor control circuit, ...Paper, ...Photosensitive drum, ...Travelling optical beam, ...Optical receiver, ...Semiconductor laser, ...Laser control circuit, ...・・BD waveform shaping circuit, ・・BD abnormality detection circuit. Drive (f) Figure 4 Figure 5 Figure 8D Figure 6 (A) Figure 7 ACH

Claims (2)

[Claims] (1) An image forming apparatus that records image information by scanning a light beam on a recording medium, which includes a polygon motor for driving a rotating polygon mirror that scans the light beam, and detecting the rotational state of the polygon motor. An image forming apparatus comprising: rotation detection means; and clock generation means for generating a clock signal in proportion to a rotation detection pulse signal output from the rotation detection means. (2) The image forming apparatus according to claim 1, wherein the rotation detection pulse signal of the polygon motor is used as a reference signal, and a clock signal is generated using a voltage controlled oscillator.