JPS6143906B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recording device, and in particular to a recording device that has a constant phase and a stable frequency for a trigger signal that is output irregularly, and is capable of obtaining a high-quality image. The present invention relates to a suitable recording device.

Conventionally, in beam scanning recording devices that record information by modulating and deflecting a light beam or an electron beam, the beam deflection position and modulation timing are extremely important factors, and the This has a large impact on image quality.

FIG. 1 is a schematic configuration diagram schematically showing the basic configuration of a laser beam recording device.

A laser beam oscillated by a laser oscillator 1 is guided to an input aperture of a modulator 3 via a reflecting mirror 2. The reflector 2 is inserted to bend the optical path in order to reduce the space of the device.
It will be removed if it is not needed.

For the modulator 3, an acousto-optic modulation element using a known acousto-optic effect or an electro-optic element using an electro-optic effect is used.

In the modulator 3, the laser beam is modulated in intensity according to the input signal to the modulator 3.

In addition, when the laser oscillator is a semiconductor laser, a gas laser, etc., which is capable of current modulation, or an internal modulation type laser with a modulation element built into the oscillation optical path, The modulator 3 is omitted and the beam is guided directly to the beam expander 4.

The beam diameter of the laser beam from the modulator 3 is expanded by a beam expander while it remains a parallel beam. Furthermore, the laser beam whose beam diameter has been expanded is incident on a polyhedral rotating mirror 5 having one or more mirror surfaces. The polyhedral rotating mirror 5 is mounted on a shaft supported by a high-precision bearing (for example, an air bearing), and is driven by a motor 6 that rotates at a constant speed (for example, a hysteresis synchronous motor, a DC servo motor). The horizontally swept laser beam 12 is imaged as a spot on the photosensitive drum 8 by an imaging lens 7 having f-θ characteristics. In a general imaging lens, when the incident angle of a light ray is θ, the position r of the image on the image plane has the following relationship: r=f・tanθ−(1) (f: focal length of the imaging lens) , as in this embodiment, the laser beam 1 reflected by a fixed polyhedral rotating mirror 5
2, the angle of incidence of the imaging lens changes linearly with time. Therefore, the mobility of the imaged spot position on the photosensitive drum 8, which is the image surface, changes non-linearly and is not constant. That is, the moving speed increases at the point where the angle of incidence increases. Therefore, when the laser beam is turned on at regular time intervals to draw a row of spots on the photosensitive drum 8, the distance between the spots will be wider at both ends than at the center.

In order to avoid this phenomenon, the imaging lens 7 is r=f・θ -(2) It is designed to have certain characteristics.

Such an imaging lens 7 is called an f-θ lens. Furthermore, when collimated light is imaged into a spot by an imaging lens, the minimum diameter of the spot dmin is dmin=εfλ/A - (3) where f: focal length of the imaging lens λ: wavelength of the light used A ; If the incident aperture of the imaging lens or the incident beam diameter is small, the incident beam will expand. ε: Given by a constant that depends on the beam shape. If f and λ are constant, increasing A will result in a smaller spot diameter dmin. can get. The beam expander 4 mentioned above is used to provide this effect. Therefore, if the required dmin can be obtained by the beam diameter of the laser oscillator, the beam expander 4 is omitted.

The beam detector 18 has a small entrance slit and
It consists of a photoelectric conversion element (for example, a PIN diode) with a fast response time. The beam detector 18 detects the position of the swept laser beam 12, and uses this detection signal to determine the start timing of an input signal to the modulator 3 for providing desired optical information on the photosensitive drum. As a result, it is possible to greatly reduce errors in the division accuracy of each reflective surface of the polyhedral rotating mirror 5 and synchronization deviations in horizontal signals due to uneven rotation, and it is possible to obtain high-quality images and to The tolerance range of accuracy required for the drive motor 6 is increased, and the drive motor 6 can be manufactured at a lower cost.

As described above, the deflected and modulated laser beam 1
2 is irradiated onto the photosensitive drum 8, visualized by an electrophotographic process, transferred to plain paper, fixed, and output as a hard copy.

Next, the printing section 20 will be explained with reference to FIG. 2.

As an example of the electrophotographic process applied to this embodiment, a photosensitive plate whose basic constituents are a conductive support, a photoconductive layer, and an insulating layer, as described in Japanese Patent Publication No. 42-23910 of the present applicant. The surface of the insulating layer 8 is uniformly charged positively or negatively in advance by a first corona charger 9, and the surface of the insulating layer 8 is uniformly charged positively or negatively by the first corona charger 9, and
Charges having a polarity opposite to the charged polarity are captured inside the photoconductive layer, and then the surface of the insulating layer to be charged is irradiated with the laser beam 12 and, at the same time, an AC corona discharge is applied by the AC corona discharger 10 to remove the laser beam. A pattern is formed on the surface of the insulating layer by a difference in surface potential generated according to the light and dark pattern of the light 12, and the entire surface of the insulating layer is uniformly exposed to form a high-contrast electrostatic image on the surface of the insulating layer. After the electrostatic image is developed and visualized by a developing device 13 using a developer mainly composed of charged colored particles, the visible image is applied to a transfer material 11 such as paper using an internal or external electric field. Then, the transferred image is fixed by a fixing means 15 such as an infrared lamp or a hot plate to obtain an electrophotographic print image.Meanwhile, after the transfer is performed, the surface of the insulating layer is cleaned by a cleaning device. 16 to remove remaining charged particles, and the photosensitive plate 8 is used repeatedly.

In the configuration shown in Figures 1 and 2, image recording is performed as shown in the explanatory diagram of Figure 3. That is, the rotating photosensitive drum 8 gives a gentle sub-scan in the direction of the arrow 26 perpendicular to the scanning direction 24 of the laser beam 12, which is scanned at an extremely high speed. 3, the modulated laser beam 12 corresponding to black or white is directed onto the photosensitive drum 8 in the direction of arrow 2.
The flying spots 22 are repeatedly scanned at a very high speed in the main scanning direction indicated by 4 and at a slow speed in the sub-scanning direction indicated by an arrow 26. This flying spot 22 is subjected to brightness modulation by the modulator 3 according to its position in the main scanning direction 24 and the sub-scanning direction 26, and the photosensitive drum 8
A desired latent image is formed thereon.

As mentioned above, in this configuration, the beam detector 18 is provided to set the start timing of the input signal to the modulator 3 for providing desired optical information on the photosensitive drum 8. As mentioned above, the synchronization of the input signal to the modulator 3 is
It is necessary to always have the same phase relationship with respect to the trigger signal from the beam detector 18, and by doing so, the input signal to the modulator 3 for each main scan can be synchronized, and a high quality image can be obtained. It is something that can be obtained.

In response to such a request, a method can be considered in which the output of a crystal oscillator that is started in response to the trigger signal is used as a synchronization signal, but this method cannot be said to be reliable due to problems such as the rise characteristics of the crystal oscillator.

Furthermore, one-shot multi-function devices, multi-vibrator devices, etc. are not suitable for obtaining a reliable synchronization signal because their operation is unstable.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to eliminate the drawbacks of the prior art described above, and to provide a recording apparatus that can obtain a synchronization signal that is always output in a constant relationship with a trigger signal, and can obtain high-quality images.

In this embodiment, based on the output of the crystal oscillator with a stable oscillation frequency, the temporal relationship is always maintained with respect to the output of the crystal oscillator based on the temporal relationship of the trigger signal with respect to the output pulse of the crystal oscillator. By outputting pulses while
It is an object of the present invention to provide a recording device equipped with a new synchronization signal generating device that generates a stable and reliable synchronization signal.

FIG. 4 shows a block diagram of a synchronizing signal generator according to an embodiment of the present invention, and FIG. 5 is a time chart illustrating its operation.

In FIG. 4, 50 is a pulse oscillator that oscillates pulses at a high frequency of 50 MHz, 52 is a crystal oscillator that accurately oscillates pulses at a frequency of 5 MHz lower than that of the pulse oscillator 50, and 54 is the output of the first illustrated beam detector 18. Driver for importing, 56,5
8 is a binary counter to which the output of the pulse oscillator 50 is input to its clock terminal, and the output of the crystal oscillator 52 is input to its direct reset terminal CR through an inverter 60; 64 represents a digital comparator that compares the output of the latch 62 and the output of the counter 58 and outputs "1" when both outputs match. It is. The output of the pulse oscillator 50 is shown in FIG. 5a, and the output of the crystal oscillator 52 is shown in FIG. 5b.
These are shown in the following.

In this configuration, the counters 56 and 58 constantly count up the output of the pulse oscillator 50 and are reset by the output of the crystal oscillator 52, which is repeated.

In this state, when the laser beam is detected by the beam detector 8, the driver 54 applies a latch signal as shown in FIG. Latch. The count contents at this time are the count contents of the counter 56 from when the counter 56 is reset by the output of the crystal oscillator 52 until the latch signal is output from the driver 54.

The contents of latch 62 are compared with the contents of counter 58, but the contents of counter 58 match the contents of latch 62 only after the contents of counter 58 are reset by the output of crystal oscillator 52. This is when the count is counted up until it becomes equal to the content of the latch 62, and at this time the digital comparator 64 outputs a pulse as shown in FIG. 5d.

Therefore, the output pulse of the digital comparator 64 is generated every time the time elapses from the time when the pulse is output from the crystal oscillator 52 until the content of the counter 58 matches the count content M latched in the latch 62. The basic period is a crystal oscillator 5 that oscillates with an extremely accurate period.
2, and the error also depends on the frequency of the pulse oscillator 50.
Extremely high frequency pulse 1 oscillated from
It is possible to obtain a relatively accurate synchronization signal up to the period.

Further, each time a trigger signal is output from the beam detector 18, the latch 62 sets the counter 56 at that time.
Since the contents of the trigger signal are rewritten, the synchronization signal is always synchronized based on the new trigger signal.

Therefore, when the synchronization signal generator having such a configuration is applied to the laser beam recording device shown in the first figure, the beam detector 18 can be easily adjusted without significantly improving the rotational unevenness or surface division accuracy of the polyhedral rotating mirror 5. By controlling the input signal to the modulator 3 using a precise synchronization signal obtained based on the output of the It is something that can be recorded. In the above embodiment, the time from the pulse output of the crystal oscillator 52 to the trigger signal is digitally counted by the counter 56, and the latch 62 is
Although everything was done digitally, such as recording the stored value digitally and comparing this stored value with the digital count value of the counter 58, the above operation can also be realized using an analog configuration. It is possible.

FIG. 6 shows a block diagram of a synchronizing signal generator according to another embodiment of the present invention, and FIG. 7 is a time chart illustrating its operation. 6th
In the figure, numerals 66 and 68 are integrators that both provide integral output with the same characteristics and have the output of the crystal oscillator 52 inputted to their reset terminal CR, and 72 is the driver 54 that is given the output of the beam detector 18. A sample hold circuit 74 captures and stores the output of the integrator 56 depending on the output, and a comparator 74 outputs "1" when the output of the integrator 68 exceeds the output of the sample hold circuit 72. It shows. The output of the crystal oscillator 52 is shown in FIG. 7a. Further, the slope of each output of each integrator 66, 68 can be adjusted depending on the integrated voltage applied from terminal 76.

In this configuration, the integrators 66 and 68 always
The operation of outputting a ramp voltage based on the integrated voltage and being reset based on the output of the crystal oscillator 52 is repeated, and the output voltage waveform is as shown in FIG. 7b. In this state, when the laser beam is detected by the beam detector 18, the driver 54 supplies the sample and hold circuit 72 with a sampling signal as shown in FIG. The integral output of the integrator 66 is sampled and held. At this time, the output of the sample and hold circuit 72 becomes as shown in FIG. This is the amount of integration by the integrator 66 until the signal is output.

The hold voltage of sample-and-hold circuit 72 is compared to the contents of integrator 68;
The content of 8 matches the hold voltage when the integrated value of the integrator 68 is reset by the output of the crystal oscillator 52 and then is integrated until it becomes equal to the hold voltage of the sample and hold circuit 72. At this time, the comparator 74 outputs "1" as shown in FIG. 7e.

Therefore, the output signal of the comparator 72 is as follows from the time when the pulse output is made from the crystal oscillator 52.
The integral output of the integrator 68 is sent to the sample hold circuit 7.
It rises to "1" every time the time elapses until it matches the voltage held at "2", and its basic period depends on the frequency of the crystal oscillator 52, which oscillates at an extremely accurate period. The error is also integrator 66,6
If an accuracy of 8 is ensured, extremely few synchronization signals can be obtained.

Further, the sample and hold circuit 72 performs T ₁ and T ₂ every time a trigger signal is output from the beam detector 18.
In addition, since the output voltage of the integrator 66 at that point in time is sampled, the synchronization signal is always synchronized based on a new trigger signal.

A device having such a configuration can also be applied to a laser beam recording device, similar to the configuration shown in the fourth figure, to obtain extremely good results.

In each of the above embodiments, the output of the beam detector 18 is used as the trigger signal, but the trigger signal is not limited to a specific signal and may be a synchronized frequency signal. Any signal may be used as long as it is a reference signal for obtaining the signal. Furthermore, the application of the present invention is not limited to laser beam recording devices, but can be applied to all other devices. Furthermore, the present invention can be realized by combining digital techniques and analog techniques.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram showing the basic configuration of the laser beam recording device, Fig. 2 is a cross-sectional view of the printing section of the first Fig. 1 recording device, and Fig. 3 is an explanatory diagram of the recording principle of the first Fig. 1 recording device. , FIG. 4 is a block diagram of a synchronization signal generating device according to an embodiment of the present invention, FIG. 5 is a time chart explaining the operation of the device shown in FIG. FIG. 7 is a block diagram of the synchronizing signal generator, and a time chart for explaining the operation of the device shown in FIG. 18... Beam detector, 50... Pulse oscillator, 52... Crystal oscillator, 56, 58... Counter, 62... Latch, 64... Digital comparator, 66, 68... Integrator, 72... Sample Hold circuit, 74... comparator.

Claims (1)

[Claims] 1. In a recording device that records an image by repeatedly scanning a recording medium with a beam, the scanning position of the beam is indicated every time the beam scans in order to determine the timing to start recording an image. Trigger signal generation means for generating a trigger signal; reference pulse generation means for generating a reference pulse of a reference frequency; and means for measuring and storing the time from generation of the reference pulse to input of the trigger signal. and a synchronization signal output means for outputting a synchronization signal every time the stored time elapses from the reference pulse, and recording an image based on a synchronization signal of a predetermined period output from the synchronization signal output means. A recording device characterized by performing the following.