JP2615668B2 - Laser recording device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser recording apparatus using a rotating polygonal mirror having a plurality of reflecting surfaces, and more particularly, to a variation in the rotation speed of the rotating polygonal mirror and the rotation of the rotating polygonal mirror. The present invention relates to a control for correcting an image jitter caused by a variation in processing accuracy of each reflecting surface of a mirror.

[Conventional technology]

Conventionally, a laser light generated from a laser light oscillator is modulated by an image signal, and the modulated light is deflected by a rotating polygon mirror such as a polygon mirror and scanned on a photosensitive member which is a recording medium. After forming an electrostatic latent image,
2. Description of the Related Art A laser recording apparatus (laser printer) that develops by a developing device and performs transfer recording on transfer paper is known.

In such a laser recording apparatus, a so-called jitter occurs in which the pixel position of a latent image formed on the photoreceptor fluctuates due to an error in the reflectance of each reflecting surface of the rotary polygon mirror or a fluctuation in the rotation cycle.

In order to achieve the above object, the present invention modulates a laser beam generated from a laser oscillator according to an image signal by an optical modulator, and deflects the modulated laser beam by a rotary polygon mirror having a plurality of reflection surfaces. A laser detector that records an image by scanning over a recording medium, and a first detector that detects a start timing of each of the scans, and a second detector that detects an end timing of each of the scans. A detector, a clock generator for generating a clock signal, and each pixel information of the image signal captured in synchronization with the clock signal generated from the clock generator, and the scanning detected by the first detection unit. And a synchronous circuit for supplying the image signal to the optical modulator in synchronization with the start timing of the scan, and detecting whether the scan start timing is detected by the first detection unit. A counter for counting a clock signal generated by the clock generator until the end of the scanning is detected by the second detection means; and a count value counted by the counter for each reflection of the rotary polygon mirror. Storage means for storing information corresponding to each surface; and one rotation of the rotary polygon mirror corresponding to a deviation between a count value corresponding to each reflection surface of the rotary polygon mirror stored in the storage means and a predetermined reference value. The correction output previously output corresponding to the reflection surface is corrected to calculate a new correction output, and the period of the clock signal generated from the clock generator based on the new correction output is calculated by the rotating polygon mirror. And a jitter correction circuit variably controlled corresponding to each reflection surface.

[Action]

In the present invention, the jitter correction circuit performs one rotation of the rotary polygon mirror one rotation before corresponding to the deviation between the count value corresponding to each reflection surface of the rotary polygon mirror stored in the storage means and a predetermined reference value. The correction output output corresponding to the reflecting surface is corrected to calculate a new correction output, and the period of the clock signal generated from the clock generator based on the new correction output is calculated by each reflection of the rotary polygon mirror. Variable control corresponding to the surface.

According to such a configuration, a relatively long-period jitter caused by fluctuations in the rotation speed of the rotary polygon mirror and one of the rotary polygon mirrors caused by variations in the processing accuracy of the respective reflecting surfaces of the rotary polygon mirror.
Both relatively short-period jitter occurring during rotation can be corrected.

〔Example〕

FIG. 1 is a block diagram showing one embodiment of the present invention.
Laser light generated from the laser oscillator 1 is input to the optical modulator 2 and is modulated by an image signal input from the synchronization circuit 3. The modulated laser light is deflected by a rotary polygon mirror 5 driven to rotate by a motor 4, and is scanned on the surface of the photoconductor 6 via an imaging optical system (not shown).
Here, the period during which the light is deflected by one reflection surface of the rotary polygon mirror 5 corresponds to one scanning period in the main scanning direction of the recorded image, and at the start of one scanning cycle, the laser beam adjusts the timing of the scanning start position. It is detected by the leading edge detector 7 that detects it.

At the end of one scanning cycle, the laser beam is detected by an end detector 12 which detects the timing of the scanning end position.

Upon detecting the scanning start timing of the laser beam, the leading end detector 7 inputs the detection output to the pulse generator 8, and the pulse generator 8 generates a single pulse SOS having a predetermined width synchronized with the scanning start timing. This single pulse SOS is input to the jitter correction circuit 9 and the synchronization circuit 3.

When the end detector 12 detects the scan end timing, the detection output is input to the pulse generator 13 and the pulse generator 13
From 13, a single pulse EOS synchronized with the scan end timing is generated. The single pulse EOS is input to the jitter correction circuit 9.

When the single-shot pulses SOS and EOS are input, the jitter correction circuit 9 detects the period from the single-shot pulse SOS to the single-shot pulse EOS for each reflection surface of the rotary polygon mirror 5, and further detects the scan value and the period for each reflection surface. Calculates the deviation of the period from the reference value, and outputs a voltage signal corresponding to the deviation to a voltage-controlled variable frequency oscillator (VC
O) Supply as 10 control voltage. VCO10 is one of the recorded images
A clock signal having a cycle corresponding to 1/4 to 1/8 of a pixel is generated. When a voltage signal related to a shift of a scanning cycle is input from the jitter correction circuit 9, the clock signal generated until then is output. Is corrected by the correction width indicated by the voltage signal and output.

On the other hand, there is a synchronous circuit 3 in which an image signal to be recorded is input to the optical modulator 2 in synchronization with a single pulse SOS from the pulse generator 8 and a clock signal from the VCO 10, but the period of the clock signal is Since the correction is made in accordance with the shift amount of one scanning cycle for each scanning cycle, the scanning cycle length of one scanning line of the laser beam changes, whereby the leading pixel position and the ending pixel position become 1/4 to 1 for each scanning line. It is suppressed to fluctuation within the range of / 8. Therefore, even if the rotational fluctuation of the rotary polygon mirror 5 occurs, it is possible to correct both the jitter due to the fluctuation and the jitter due to the variation in the processing accuracy of the rotary polygon mirror 5.

In other words, only by correcting the clock signal of the oscillator 10 only by the deviation between the period detection value from SOS to EOS and the reference scanning period, it is possible to correct the jitter accompanying the rotation fluctuation including the entire four scanning periods, By detecting the scanning cycle for each reflecting surface as described above, it is possible to correct the variation in the scanning cycle for each reflecting surface.

FIG. 2 is a circuit diagram showing a specific configuration of the jitter correction circuit 9. The counter 99 counts clock pulses of the VCO 10 from the occurrence of a single pulse to the occurrence of EOS. On the other hand, the counter 100 updates the count value each time the single pulse SOS is input, and forms an address signal indicating each reflection surface number n of the rotating polygon mirror. This address signal is applied to each reflection surface of the rotating polygon mirror. The data is supplied to the address of the memory 101 having the corresponding n recording areas.

In the memory 101, the count output of the counter 99 is input to its data input, and a single pulse EOS is input as a write command.

Therefore, the value of the detection cycle from SOS to EOS detected by the counter 99 is stored in the memory 101 for each reflection surface. The arithmetic circuit 91 compares the detected value of the scanning cycle for each reflecting surface obtained in this way with the reference value, and controls the oscillation frequency of the VCO 10 for each reflecting surface according to the deviation.

Here, the address counter 100 sets the address value m (m =
1... N), the scan period detection value Cm of the m-th reflection surface one rotation before is read from the memory 101.

Therefore, the arithmetic circuit 91 calculates a deviation k (C0-Cm) between the detection value Cm one rotation before and the reference value C0, and outputs the deviation k (C0-Cm) previously output.
The correction output regarding the m-th reflection surface is added, and the added value Dm (t) = Dm (t−1) + k (C0−Cm) is output as the current correction output Dm (t) regarding the m-th reflection surface. .

Here, k is a correction coefficient, and usually k may be set to 1. In addition, the arithmetic circuit 91 has n storage areas like the memory 101 in order to perform the above-described arithmetic operation.
The correction output Dm (t) output this time is stored until the next cycle.

〔The invention's effect〕

As described above, according to the present invention, the scanning period of the laser beam is detected for each reflecting surface of the scanning means, and the period of the clock pulse for synchronizing the image signal in accordance with the deviation between the detected value and the reference value is set to the reflecting surface. Since the variable control is performed separately, it is possible to accurately correct both the jitter due to the rotation fluctuation of the rotating polygon mirror and the jitter for each reflecting surface due to the variation in the processing accuracy of each reflecting surface.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 is a detailed configuration diagram showing an example of the jitter correction circuit of FIG. DESCRIPTION OF SYMBOLS 1 ... Laser oscillator, 2 ... Optical modulator, 3 ... Synchronous circuit, 4 ... Motor, 5 ... Rotating polygon mirror, 6 ... Photoconductor,
7 ... tip detector, 8, 13 ... pulse generator, 9 ... jitter correction circuit, 10 ... oscillator, 12 ... termination detector, 91 ...
Arithmetic circuit, 99 counter, 100 address counter, 101 memory.

Claims (1)

(57) [Claims] A laser light generated from a laser oscillator is modulated by an optical modulator in accordance with an image signal, and the modulated laser light is deflected by a rotary polygon mirror having a plurality of reflecting surfaces to be reflected on a recording medium. In a laser recording apparatus for recording an image by scanning, a first detector for detecting a start timing of each of the scans, a second detector for detecting an end timing of each of the scans, and a clock signal And a clock generator that generates each pixel information of the image signal in synchronization with the clock signal generated by the clock generator, and synchronizes with the scan start timing detected by the first detection unit. A synchronization circuit for supplying the image signal to the optical modulator, and the second detection means after detecting the start timing of the scanning by the first detection means. A counter for counting the clock signal generated from the clock generator until the end timing of the scanning is detected, and a count value counted by the counter is stored in correspondence with each reflection surface of the rotary polygon mirror. Storage means for performing, on the reflection surface before one rotation of the rotary polygon mirror corresponding to the deviation between the count value corresponding to each reflection surface of the rotary polygon mirror stored in the storage means and a predetermined reference value The correction output corresponding to the correction output is corrected to calculate a new correction output, and the cycle of the clock signal generated from the clock generator based on the new correction output corresponds to each reflection surface of the rotary polygon mirror. And a jitter correction circuit for variably controlling the laser recording apparatus.