JPS61240759A - Laser image recording device - Google Patents

Abstract

PURPOSE:To obtain a stable recorded images by detecting a peak value of output of a photodetector, selecting a waveform corresponding to the peak value from a stored beam waveform and correcting the timing of an image information recording according to lag relation between synchronizing signals. CONSTITUTION:A synchronizing signal generating circuit 8 receives a detection signal of a light scanning beam from a photodetector 7 and generates synchronizing signals for adjusting a timing of starting an image information recording of each scanning. A recording controlling circuit 10 stores a waveform of plural light scanning beams beforehand and inputs synchronizing signals from the synchronizing signal generating circuit 8, and inputs a peak value signal from a peak value detecting circuit 9, and selects the waveform of stored light scanning beam based on the peak value signal. By this selected waveform, the time until starting of the image information recording can be set automatically, stepwise or continuously. The timing from the generation of synchronizing signals to the image information recording is corrected by this setting. A laser driving circuit 11 makes a semiconductor laser 2 on and off by recording signals sent from the recording controlling circuit 10.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an image recording apparatus that forms an image, records information, etc. by scanning an object with a scanning light beam using a polarizer, etc. The present invention relates to a laser image recording device that can appropriately control start timing and perform stable recording.

2. Description of the Related Art Conventionally, as this type of optical scanning device, one as shown in FIG. 4, which shows an electrostatic latent image forming section of a laser image recording device, has been proposed. In FIG. 4, an optical scanning beam L outputted by a semiconductor laser 2 is made into parallel light by a collimator lens 3, and then polarized (scanned) in the axial direction of the photoreceptor drum 1 by a rotating polygon mirror 4. An image is formed on the photosensitive drum 1 by a lens 5. The light beam L output by the semiconductor laser 2 is modulated by an electric signal (not shown), and since the photoreceptor drum 1 is rotated at a constant speed in the direction of the arrow, an electrostatic latent image is formed on the photoreceptor drum 1. is formed two-dimensionally. In addition,
A developing/transfer means of a well-known electrophotographic process is arranged around the photosensitive drum 1, so that the electrostatic latent image described above is visualized on the recording paper.

In such a configuration, in order to adjust the timing of modulation of the optical scanning beam in the axial direction S of the photosensitive drum 1 for each scan and to accurately align the position of the recorded image area, the reflecting mirror 6 is used.
and a photodetector 7, the optical scanning beam is incident on the optical detector 7 to generate an optical beam scanning synchronization signal,
This synchronization signal controls the timing of the start of modulation of the image recording signal of the semiconductor laser 2. This light beam scanning synchronization signal is generally generated by comparing the output level of the photodetector 7 with a predetermined reference level.
This is done by detecting an optical scanning beam. Note that by accurately obtaining this synchronization signal for each scan, the timing of image signal modulation can be determined accurately regardless of the accuracy of the surface division angle of the rotating polygon 'a4 and the unevenness of the rotational speed. It is possible to accurately match the optical scanning beam for each scan, and it is necessary to detect the optical scanning beam with extremely high precision and generate a synchronization signal.

The image signal modulation timing is controlled by the synchronization signal. First, clocks of a certain frequency are counted by the synchronization signal, and when the count reaches a certain number, that is, when the optical scanning beam reaches the photodetector. 7 and reaches the image recording start position, the image signal modulation is started. Second, instead of a counter,
By providing a timer including a time constant circuit, a similar effect can be obtained by generating an output after a certain period of time that is the same as the time for counting a certain number of clocks.

Further, by changing the count value of the counter and the time constant of the timer, it is possible to define the recording start position according to the recording paper size and the like.

Problems to be Solved by the Invention However, with this configuration, the output of the photodetector may be affected due to variations in the reflectance of each mirror surface of the rotating polygon mirror 4 and variations in processing accuracy (flatness, roughness, etc. of the reflecting surface). When the light intensity of the scanning light beam changes for each scan, or when the photodetector 7
If the output of the photodetector 7 fluctuates due to dust adhering to the photodetector T, etc., the output waveform of the photodetector T will fluctuate, causing a time lag in the generation of the synchronization signal that is the reference for starting scanning.
Images formed based on this scanning synchronization signal will also be shifted. This will be explained using FIG. When the optical scanning beam is incident on the photodetector 7, the optical scanning beam is
Since the photosensitive drum is scanned at a constant speed in one axial direction as shown by arrow S in FIG. 4, its output has an output waveform as shown in waveform a in FIG. 6. Here, when the output waveform of the photodetector 7 changes as shown in the waveform due to the above-mentioned causes, the synchronization signal generated by comparison with the predetermined detection level T becomes
In the case of waveform B, the synchronizing signal G is generated at time t1, and in the case of waveform S, the synchronizing signal Q is generated at time t2, resulting in a time difference and the timing of image recording is shifted.

To solve this problem, there is a method that constantly identifies the mirror surface of a rotating polygon mirror that performs light beam scanning, and corrects the timing of synchronization signal generation based on the correction amount for each mirror surface that has been stored in advance. 2826), but this method requires a very complicated device and requires periodic inspection of the correction amount. On the other hand, there is a method in which two photodetectors are arranged in the scanning direction and a constant synchronization signal is generated by the output of each, but this method requires two photodetectors and the circuit becomes complicated. It has drawbacks that lead to increased costs.

The present invention has been made in view of the above-mentioned problems, and is a laser image that prevents the occurrence of deviations in the synchronization signal of light beam scanning, and that can always record a stable image without distortion in the recorded image. The purpose is to provide a recording device.

Means for Solving the Problems In order to achieve the above object, the present invention provides synchronization as a reference for starting scanning when the output of the photodetector for each scan of the optical scanning beam exceeds a predetermined threshold. A device comprising means for generating a signal, means for detecting a peak value of the output of the photodetector, and means for correcting the timing from generation of the synchronization signal to recording of image information based on the peak value. It is.

The timing correcting means stores a plurality of waveforms of the optical scanning beam in advance, and selects a corresponding waveform based on the peak value signal.

By detecting the peak value of the output of the active photodetector, a waveform corresponding to the peak value is selected from a plurality of pre-stored beam waveforms. Then, according to the relationship between the selected waveform and the shift in synchronization signal generation timing, the amount of correction for the time from synchronization signal generation to the start of image information recording is read out, and the image information recording timing is corrected. In this way, even if the output waveform of the photodetector fluctuates due to various causes and the synchronization signal shifts, the time from the generation of the synchronization signal to the start of image information recording is adjusted for each scan to cancel out the shift. Corrected.

Embodiment @1 FIG. 1 is a schematic configuration diagram showing a laser image recording apparatus according to an embodiment of the present invention, and the same members as those shown in FIG. 4 are designated by the same reference numerals.

In the figure, 8 is a synchronization signal generation circuit, and a photodetector 7
A synchronization signal is generated to synchronize the timing of the start of image information recording for each scan. Note that the photodetector 7 uses a photodiode capable of high-speed response, and is designed to exhibit high sensitivity to the oscillation wavelength of the semiconductor laser 2. 9 is a peak value detection circuit which inputs the detection signal of the photodetector 7 and detects the peak value of this signal. This peak value detection circuit basically consists of a diode and a charging capacitor. 1o is a recording control circuit, which is
A plurality of waveforms (in this example, waveform & waveform shown in Fig. 2)
It stores the waveforms of the optical scanning beams, and inputs the synchronization signal from the synchronization signal generation circuit 8 and the peak value signal from the peak value detection circuit 9, and based on this peak value signal,
The configuration is such that a stored waveform of the optical scanning beam is selected and the time required to start recording image information based on the selected waveform can be set automatically, stepwise or continuously.
With this setting, the timing from the generation of the synchronization signal to the recording of image information is corrected.

The recording control circuit 1° is composed of a general counter or a timer, and its count value or time constant value can be controlled and selected from the outside. Reference numeral 11 denotes a laser drive circuit, which is configured to turn on and off the hexagonal current to the semiconductor laser 2 in accordance with a recording signal sent from the recording control circuit 1o. This laser drive circuit 11 uses, for example, a known constant current circuit. 12 is an image information input section. The image signal sent to the image information input section 12 is sent to the laser drive circuit 11 by the recording control circuit 10, which accurately synchronizes the recording start position and its modulation start timing for each scan. , to form an image on the photosensitive drum 1.

Regarding the laser image recording machine configured as above,
The effect will be explained below with reference to FIGS. 2 and 3.

FIG. 2 is a diagram showing the output waveform from the photodetector 7. As mentioned above, since the optical traveling beam is scanned on the constant velocity detector, the output waveform is the waveform a, the filtered waveform. As shown, the shape has a rising part, a peak part, and a falling part, and the output is symmetrical with respect to the peak part. The time from the rising edge to the falling edge is determined by the scanning speed of the light beam and the photodetector 7.
This is determined by the distance in the scanning direction of the light receiving section. Note that for waveform a and filtered waveform, the output voltage decreases uniformly, and the fluctuation rate in the linear region of the rising and falling portions is the peak value p1.
．． It is almost the same as the fluctuation rate of p2. Here, the photodetector 7
The amount of light beam incident on the photoelectric converter is directly proportional to the output voltage generated through photoelectric conversion. When the output waveform fluctuates as a waveform a or a filtered waveform due to a change in the amount of light, the synchronization signal generated by comparison with the detection level will be tl in the case of waveform a,
In the case of waveform A, this occurs at t2, but the deviation due to the synchronization signal between the two can be accurately estimated from the peak value P1 in the case of waveform A and the peak value P2 in the case of waveform A. This is 1. This is because, as described above, the fluctuation rate in each part of the waveform a and the filtered waveform can be considered to be almost the same as the fluctuation rate of the peak values p, , p2.

Figure @3 is a signal waveform diagram of main parts of a laser image recording device according to an embodiment of the present invention. Waveform A and waveform 2 represent output waveforms from the synchronizing signal generation circuit 8, and are generated at time it+time t2 according to waveform a and waveform 2 in FIG. 2, respectively. Since it is necessary to generate this synchronization signal with extremely high precision, accurate detection is performed using a sampling circuit using a high-frequency clock or a sampling circuit using multi-phase clocks whose phase is slightly shifted by a delay circuit or the like. The time Δt represents the time difference between the synchronous signal waveform A and the synchronous signal generation 2, and represents the difference between time t and time t2 in FIG. 2.

The waveform opening represents the time from the generation of the synchronization signal A to the start of image information recording, which corresponds to the peak value P□ in FIG. It represents the time B from the generation of signal 2 to the start of image information recording. The recording control circuit 1o accurately sets this time 1 hour B so that the recording start position coincides with every fixed distortion by the shift time Δt of the synchronizing signal, and recording is performed. Waveform C and waveform represent image information recording signals that respectively correspond to waveform a and waveform S of the photodetector output voltage in FIG. The recording end positions match. The time from synchronization signal generation to the start of recording is determined by controlling the mechanical precision of the arrangement of the photodetector 7 and reflection mirror 6 with respect to the photosensitive drum 1, and by controlling the recording start position by the recording size. In order to prevent the optical scanning beam from being irradiated onto the photosensitive drum 1 outside the area, the configuration is such that it can be controlled automatically or manually from the outside. In this example, the shift time Δt of the synchronization signal corresponding to the peak value of the photodetector output waveform shown in Fig. This is to perform recording timing control so as to cancel out the influence of output fluctuations of the photodetector.

In this example, a laser image recording device based on a well-known electrophotographic process is exemplified, but the invention is not limited to this, and can be applied to any recording device, image reading device, etc. that uses an optical scanning beam. It can be applied.

Effects of the Invention According to the present invention, the time from the generation of the synchronization signal to the start of image information recording is determined according to the output signal from the means for generating the synchronization signal based on the output signal of the photodetector and the means for detecting the peak value of the output signal. By controlling the correction, it is possible to prevent deviations in the synchronization signal of light beam scanning and obtain accurate image information recording timing. Obtainable.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing a laser image recording device according to an embodiment of the present invention, FIG. 2 is a waveform diagram showing the output of the photodetector of the device shown in FIG. 1, and FIG. 3 is similar to FIG. 1. FIG. 4 is a schematic perspective view showing an electrostatic latent image forming section in an example of a conventional laser image recording apparatus, and FIG. 5 is a signal waveform diagram of the main parts of the apparatus shown in FIG. 2...Semiconductor laser, 4...Rotating polygon mirror, 7...Photodetector, 8...Synchronizing signal generation circuit, 9...・Peak value detection circuit, 10...
. . . Recording control circuit, 11 . . . Laser drive circuit, 12 . . . Image signal input section, a. b...Photodetector output waveform, T...detection level. Name of agent: Patent attorney Toshi Nakao, Idiot 1
Figure 2 Ward 3 Figure 4 Figure 5

Claims (1)

[Claims] An optical scanning beam modulated according to the image information is scanned over the scanned member by a polarizer, and the scanning start is synchronized based on the scanning light detection output for each scan from the photodetection element placed in the scanning path. A laser image recording device for obtaining a signal,
means for generating a synchronization signal as a reference for starting scanning when the output of the photodetector for each scan of the optical scanning beam exceeds a predetermined threshold; and detecting the peak value of the output of the photodetector. and means for correcting timing from generation of the synchronization signal to recording of image information based on the peak value.