JPS6250721A - Photoscanning synchronizing device - Google Patents

Abstract

PURPOSE:To obtain an invariably stable recording image or readout signal by correcting the time from the generation of a synchronizing signal to the start of image information recording or reading according to the quantity of variation of a member to be scanned in a main scanning direction which is detected on every scan. CONSTITUTION:When a photodetector 7 detects light reflected by a reflecting mirror 6 in the 1st photoscanning, a synchronizing signal generating circuit 10 generates a signal. When the synchronizing signal is inputted, a recording control circuit 12 delays the operation of a laser driving circuit 13 by a set time (a) and then generates a photoscanning beam to record a signal on a photosensitive drum 1. The circuit 13 oscillates a laser beam for a period (d) a proper time interval after the end of the recording to scan an end part of the drum 1 and a position detection sensor 9 detects the position of the end surface of the drum 1 as a reference position. In the 2nd photoscanning, the quantity of variation of the end surface of the drum 1 from the reference position is detected by a position detecting circuit 11 and inputted to a recording control circuit 12. In the 3rd photoscanning, the time (a) is corrected by using the detected quantity of variation and similar operation is repeated thereafter.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical scanning synchronization device that performs image formation, information recording, or image reading by scanning a scanned member with an optical scanning beam using a polarizer or the like.

2. Description of the Related Art Conventionally, as an optical scanning device of this type, an electrostatic latent image recording section of a laser image recording device shown in FIG. 6 is known. The beam L is made into parallel light by the collimator lens 3, and then polarized (scanned) in the axial direction of the photoreceptor drum 1 (hereinafter referred to as main scanning direction a) by the rotating polygon mirror 4, and then polarized (scanned) by the f/θ lens 6 into the photoreceptor drum 1. The image is formed on the drum 1. Optical scanning beam L output by semiconductor laser 2
is modulated by an electrical signal (not shown).

Furthermore, since the photoreceptor drum 1 is rotated at a constant speed in the direction of the arrow (hereinafter referred to as the sub-scanning direction), an electrostatic latent image is formed two-dimensionally on the photoreceptor drum 1. . Incidentally, the area around the photoreceptor drum 1 is developed using a well-known electrophotographic process.

A transfer means is arranged to visualize the electrostatic latent image described above on the recording paper. In such a configuration, the timing of the start of modulation of the optical scanning beam in the main scanning direction a of the photosensitive drum 1 is taken for each scan, and in order to accurately align the position of the recorded image area, a reflecting mirror 6 is provided in the scanning path of the optical scanning beam, and a photodetector 7 is provided at a position to detect the reflected light. When the beam is incident on the photodetector 7, a light beam scanning synchronization signal is generated, and 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 and detecting the light scanning beam. Note that by accurately obtaining this synchronization signal for each scan, the timing for starting image signal modulation can be determined accurately regardless of the accuracy of the surface division angle of the rotating polygon mirror 4 and unevenness in rotation speed, and therefore the image position can be determined accurately. can be precisely matched for each scan, it is necessary to detect the optical scanning beam with extremely high precision and generate a synchronization signal. One method of controlling the image signal modulation start timing using the synchronization signal is to count clocks of a constant frequency using the synchronization signal, and when the count reaches a constant number, that is, when the optical scanning beam L is This is a control method in which image signal modulation is started only when the image signal passes through the detector 7 and reaches the image recording start position. Another method is to provide a timer including a time constant circuit instead of a counter so that the image signal modulation is started after a certain period of time that is the same as the time for counting a certain number of clocks, and a similar effect can be obtained. It's something you get. In these methods, by changing the count value of the counter or the time constant of the timer, it is possible to selectively define the image recording start position depending on the recording paper size or the like.

Problems to be Solved by the Invention However, with such a configuration, no matter how accurately the optical scanning beam L is detected by the photodetector 7 and the timing of starting image recording is made the same for each scan, the scanned target If the photosensitive drum 1, which is a member, changes its position in the main scanning direction during image recording due to play during installation or aging of the bearing, the image formed based on a fixed recording timing signal will also change in each scan. It will shift from time to time. This will be explained using FIG. Polarized light (scanning) in main scanning direction a
The optical scanning beam L enters the photodetector 7 in FIG. 6 and starts recording an image after a certain period of time. Although recorded at the same distance, when the photoreceptor drum 1 changes its position in the main scanning direction a with respect to the mounting position of the photodetector 7, the recorded dots D are recorded at the same distance as shown in FIG. When viewed with the end surface of the drum 1 as a reference, it will be shifted in the main scanning direction a. This deviation ΔE of the recorded dots D corresponds to the amount of positional variation of the photosensitive drum 1, and the recorded image is disturbed.

To solve this problem, it is possible to prevent the recording dots D from shifting by mechanically eliminating the mounting looseness in the main scanning direction of the photosensitive drum 1 on which an electrostatic latent image is formed according to image information. Theoretically, this is possible, but the misalignment of the recording dots requires a very high degree of precision. Even if you adopt a method of forcibly applying a load to prevent misalignment, it is difficult to completely prevent misalignment.
Furthermore, since the photoreceptor drum 1 requires regular maintenance, it is desirable that the method for attaching and detaching it be as simple as possible.
In addition to increasing costs, this method cannot prevent displacement due to mechanical vibration of the photoreceptor drum 1, and is ultimately not a satisfactory solution. Note that such problems occur not only in recording devices but also in reading devices that use optical scanning beams.

The present invention has been made in view of the above-mentioned problems, and is capable of preventing the occurrence of misalignment of a recorded image on a scanned member, and of always recording a stable image without distortion of the recorded image. An object of the present invention is to provide an optical scanning synchronization device that can stably read an image on a scanned member without causing distortion.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention includes a photodetector that detects the scanning light for each scan of the optical scanning beam, and a detection output from the photodetector that detects the start of scanning. means for generating a reference synchronization signal; means for detecting the amount of variation in the polarization direction of the optical scanning beam of the scanned member; and recording or reading of image information from the generation of the synchronization signal based on the amount of variation. and means for correcting the timing until the start.

Effect: With the above-described configuration, the present invention detects the amount of variation in the main scanning direction for each scan of the scanned member, and uses the detected amount of variation to determine the time from the generation of the synchronization signal to the start of image information recording or reading. can be corrected, and deviations in the recording position or reading position can be prevented. In this way, even if the recording position of the scanned member changes in the main scanning direction with respect to the photodetector from the main scanning start position of the first line due to various reasons, image information recording will start from the generation of the synchronization signal. Alternatively, the time until the start of reading is corrected for each scan depending on the variation.

Example Hereinafter, preferred embodiments of the present invention will be described.

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. 6 are designated by the same reference numerals and detailed explanations will be omitted.

In FIG. 1, 8 is an imaging lens, and 9 is a position detection sensor. The imaging lens 8 is adjusted to form an image of the optical scanning beam reflected by the surface near the end face of the photoreceptor drum 1 on the light receiving sensor position of the position detection sensor 9. It is fixed at a fixed position separately from the photosensitive drum 1. The position detection sensor 9 reads the reflected light of the optical scanning beam scanning the part other than the recording width of the photoreceptor drum 1, and detects the direction of the main scanning direction of the photoreceptor drum 1 based on the change in the area where the reflected light is generated. It detects the position. In this embodiment, a focusing rod lens array (SLA) is arranged in the imaging lens 8 so as to have a long shape in the main scanning direction a. In addition, a C0D (charge coupled device) is used for the position detection sensor 9 to further improve end face detection accuracy, and the position detection unit combining the imaging lens 8 and the position detection sensor is made lightweight and compact.

LE is the recording width.

FIG. 2 is a diagram showing a schematic configuration of a circuit of a laser image recording apparatus according to an embodiment of the present invention. Reference numeral 10 denotes a synchronization signal generation circuit, which receives a detection signal of the optical scanning beam from the photodetector 7 and generates a synchronization signal for synchronizing the timing of the start of image information recording for each scan. Note that the photodetector 7 includes
A photodiode capable of high-speed response is used, and is designed to exhibit high sensitivity to the oscillation wavelength of the semiconductor laser 2. 11
is a six-position detection circuit, which detects the amount of variation of the photosensitive drum 1 in the main scanning direction based on the output signal from the position detection sensor 9. Reference numeral 12 denotes a recording control circuit which stores in advance the amount of correction of the image information recording start timing based on the amount of variation in the main scanning direction a of the photosensitive drum 1, and also controls the synchronization signal from the synchronization signal generation circuit 10. A position detection signal from the position detection circuit 11 is input, a stored correction amount for the recording start timing is selected based on this position detection signal, and the correction amount until the start of image information recording is determined based on the specified correction amount. The time is configured such that it can be automatically set stepwise or continuously, and by this setting, the timing from the generation of the synchronization signal to the recording of image information is corrected. The recording control circuit 12 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. 13 is a laser and drive circuit, which drives the semiconductor laser 2 according to a recording signal sent from the recording control circuit 12.
The circuit is configured to turn on and off the input current to the circuit. This laser drive circuit 13 uses, for example, a known current circuit. 14 is an image information input section. The image signal sent to the image information input section 14 is synchronized by the recording control circuit 12 with respect to the recording start position and the timing of its modulation start for each scan, and is sent to the laser drive circuit 13, and is sent to the laser drive circuit 13. An image is formed on the body drum 1.

FIG. 3 is a diagram for explaining the output waveform from the position detection sensor 9, and shows the position of the light receiving sensor of the position detection sensor 9 corresponding to the polarization direction of the optical scanning beam (in this embodiment, the position is equal to the CCD sensor arrangement direction). ) The output waveforms are waveform A and waveform B.
, the output waveform C corresponding to the amount of reflected light from the surface of the photoreceptor drum 1 of the optical scanning beam is a waveform created by moving in the direction of the arrow by main scanning, and has a constant output voltage value region. The shape has a falling region. The intermediate position E1 of this falling region. The area indicated by the arrow on the left side from E2 is the area indicating the photosensitive drum 1, and the intermediate position E1. E
An arrow portion F on the right side from 2 corresponds to an area outside the end surface of the photoreceptor drum 1. Therefore, when the position of the photosensitive drum 1 changes in the main scanning direction, the output waveform of the position detection sensor 9 changes as shown in waveform A and waveform B, and the falling position changes, so that the detection level remains constant. The output signal obtained by the comparison is generated at the sensor position 1 from a fixed reference point in the case of waveform A and at 12 in the case of waveform B. A position detection circuit 11 detects the amount of variation in the position where these two output signals are generated, that is, the amount of variation from the reference position of the photosensitive drum 1.

Next, the operation of the above embodiment will be explained with reference to the main signal waveform diagram shown in FIG. First, in the first optical scanning, when the photodetector 7 detects the light reflected by the reflecting mirror 6, the synchronization signal generation circuit 10 generates the synchronization signal shown in FIG. 4A. 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 a multiphase clock whose phase is slightly shifted by a delay circuit or the like. When the synchronization signal is input to the recording control circuit 12, the recording control circuit 12 delays the operation of the laser drive circuit 13 by a preset time a, as shown in FIG. Thereafter, the laser drive circuit 13 generates an optical scanning beam modulated according to the image signal, as shown by C in FIG. 4, and performs recording on the photosensitive drum. After an appropriate time interval after the end of recording, the laser drive circuit 13 continuously oscillates the laser for a period d to scan the end portion of the photoreceptor drum, and the position detection sensor 9 detects the position of the photoreceptor drum 1. Detects the position of the end face. The position E0 at this time becomes the reference position.

Note that the continuous light emitting period d only needs to have a width sufficient to detect the maximum value of the amount of variation in the main scanning direction of the photoreceptor drum 1, and should be kept as short as possible in consideration of the life span of the semiconductor laser 2, etc. It is set.

The second scan is performed in the same manner. However, at the second time, the amount of variation in the end surface position of the photosensitive drum 1 from the reference position is detected by the position detection circuit 11 and inputted to the recording control circuit 12. In the third optical scan, the timing (time a in FIG. 4) from the generation of the synchronizing signal to the start of recording is corrected by the amount of variation detected during the previous scan. Thereafter, similar operations are repeated. Here, photoreceptor drum 1
The timing correction according to the variation amount will be further explained.

Now, assume that the end surface position of the photosensitive drum 1 was E in FIG. 3 during the previous scan, and the sensor position l was detected. At the time of the next scan, the synchronization signal shown in FIG.
2 is input. On the other hand, the position detection circuit 11 has a variation amount l,
has already been output to the recording control circuit 12. The recording control circuit 12 corrects the start delay time a in FIG. 4 based on the correction amount stored in advance in accordance with the variation amount 11, as shown in FIG. Thus, after a delay time has elapsed since the synchronization signal was generated, recording is performed as shown in FIG. Here, the delay time S is selected so that the distance from the recording start position to the photoreceptor drum end surface position E1 is equal to the distance from the recording start position to the photoreceptor drum end surface position E0 in C. Similarly, when the end surface position of the photosensitive drum 1 reaches E2, after the synchronization signal shown in G is generated, the signal is delayed by a delay time C corresponding to the amount of end surface variation 12 as shown in H, and then as shown in R. will be recorded. The distance between the recording start position and the end surface position E2 of the photosensitive drum 1 is also the same as in case C. As described above, recording is performed at the same position from the end surface regardless of the positional fluctuation of the photosensitive drum 1 in the main scanning direction.

Note that the time a from the generation of the first synchronization signal to the start of recording is set in order to reduce the mechanical precision of the arrangement of the photodetector 71 reflecting mirror 6 with respect to the photosensitive drum 1, and to change the recording start position depending on the recording size. , which can be controlled automatically or manually from the outside, and the above-mentioned corrections are thereby added to the set time.

The electrostatic latent image formed on the photosensitive drum shown in FIG. 1 is made visible by a developing device (not shown), and then transferred onto a recording medium to finally become a recorded image.

At this time, since the recording medium is temporarily attracted onto the photoreceptor drum 1 by the static electricity on the photoreceptor drum 1, the recording medium does not shift relative to the photoreceptor drum 1. If the image recording position varies from the end face for each scan, the variation will be directly transferred to the recording medium. However, as mentioned above, the photoreceptor drum 1
Since the recording timing is controlled so that the image information recording area is constant for each scan with respect to the end face of the recording medium, the image transferred to the recording medium is good and free of distortion.

In the above embodiment, the end face position of the photoreceptor drum detected during the first scan was used as the reference position, but instead of this, a reference position is set in advance, and the amount of variation from the reference position is always adjusted. The delay time until the start of recording may be corrected accordingly.

Further, in the above embodiment, the optical scanning beam is directly used as the light source of the position detection sensor 9 for detecting the end surface position of the photoreceptor drum 1, but the invention is not limited to this.
Similar control may be performed using a halogen lamp or an LED as the light source. Further, in the above embodiment, a laser image recording device based on a well-known electrophotographic process is illustrated, but the present invention is not limited thereto, and can be applied to any recording device or image reading device that uses an optical scanning beam. It is applicable.

Effects of the Invention As is clear from the above description, the present invention provides a means for generating a synchronizing signal based on an output signal of a photodetector, and a means for generating a synchronizing signal according to an output signal from a means for detecting fluctuations in the main scanning direction of a scanned member. By correcting and controlling the time from generation to the start of image information recording or reading, it is possible to keep both information recording positions or reading positions constant for each scan, so there is no image shift for each scan, and the image is stable. This has the effect that recorded images or read signals can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a schematic configuration of a main part of a laser image recording device using an optical scanning synchronization device according to an embodiment of the present invention;
Fig. 2 is a circuit block diagram thereof, Fig. 3 is a waveform diagram of the output of the position detection sensor shown in Fig. 2, Fig. 4 is a waveform diagram of main signals of the above embodiment, and Fig. 6 is a conventional laser image recording method. FIG. 6 is a perspective view of the main parts of the electrostatic latent image forming section of the apparatus, and is a schematic diagram of a conventional image recording example 1...Photosensitive drum (scanned member), 2
... Semiconductor laser, 4 ... Rotating polygon mirror, 6 ... Reflection mirror, 7 ... Photodetector, 8
...Imaging lens, 9...Position detection sensor, 1o...Synchronization signal generation circuit, 11...
...Position detection circuit, 12... Recording control circuit, 1
3... Laser drive circuit, 14... Image signal input section, A. B...Position detection sensor output waveform. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 7-9 Detection number 8-11 9-ft

Claims (1)

[Claims] a photodetector for detecting the optical scanning beam for each scan; means for generating a synchronization signal as a reference for starting scanning based on the detection output from the photodetector; An optical scanning synchronization device comprising means for detecting an amount of variation, and means for correcting timing from generation of the synchronization signal to start of image information recording or reading based on the amount of variation.