JPS6137606B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laser beam recording device, and more particularly to an inexpensive and highly reliable laser beam deflection system.

In order to print out information from electronic computers at high speed, printers have been made faster. However, conventional type hammer type printers have their own limitations on printing speed, and high-speed non-impact printers have been developed whose printing speed is not limited by mechanical factors.
A typical example of these technologies is a laser beam printer that combines electrophotography and laser beam exposure. With current technology, it has been demonstrated that it is possible to create a printer with a recording speed of approximately 1 m/s by using a photoconductor whose wavelength region with the best spectral sensitivity characteristics matches the emission wavelength of a laser beam. There is.

Although laser beam printers are extremely superior in terms of performance, the current biggest problems in realizing this device are the technical difficulties of the components and their cost. It's probably the height. Particularly regarding the optical system, special equipment is required in addition to the various optical components commonly known in the prior art.

Generally, the optical system of a laser beam printer is composed of the following factors.

(1) Laser light source: Required as a single wavelength, phase-aligned point light source.

(2) Modulator: means for modulating the laser beam according to input information.

(3) High-speed rotating polygon mirror: means for deflecting and scanning the modulated laser beam. Although it depends on the recording speed, recording accuracy, and number of mirror surfaces, the rotation speed is generally 10,000 revolutions per minute or more.

(4) F-theta lens: characters are formed by scanning the photoreceptor with a laser beam deflected by the high-speed rotating polygon mirror, so a normal lens will cause too much distortion around the photoreceptor. . This is a large-diameter lens that corrects this distortion.

For high-speed modulation, even if (1) and (2) above are absolutely necessary, (3) a high-speed rotating polygon mirror, and
(4) The use of the F-theta lens makes the recording apparatus extremely expensive and special.
Regarding high-speed rotating polygon mirrors, the rotation speed is 1 per minute.
Since the number of cycles is more than 10,000 times, and typically reaches around 20,000 times, it is not possible to use ordinary mechanical bearings or bearings, and it is necessary to use something that requires advanced technology such as air bearings. . In addition, high-precision processing technology is required, as the surface tilt accuracy between each mirror surface of a polygon mirror must be within a few seconds.

For F-θ lenses, the maximum effective diameter is 100mm
Therefore, a large aperture lens with a lens length of 100 mm or more is required, and special technology is required to polish such a large lens.

In addition to such an optical system, it is conceivable to scan the laser beam using a scanning device such as a galvanometer mirror, but generally speaking, such a galvanometer-like reflecting mirror is used at high speed. It is extremely difficult to stably swing it in a sawtooth wave.

On the other hand, it is possible to make a galvanometer-like reflector resonate with a sine wave and deflect it at high speed, but when it is vibrated like a sine wave, it is difficult to actually record when it deflects to one side (for example, from left to right). In addition to the disadvantage that if only the peripheral part and the central part are used, the scanning speed is different between the peripheral part and the central part, which causes distortion in the recorded image.

In addition, there are devices that feed back part of the laser beam used for recording to the position detection system using a half mirror, etc., but this method reduces the amount of laser beam used for recording and reduces the amount of exposure to the photoreceptor for recording. In order to reduce this, it was necessary to slow down the deflection scanning speed, increase the amount of laser beam emission, or increase the sensitivity of the photoreceptor.

Therefore, an object of the present invention is to provide a laser beam that does not require such special technology and can use common parts as much as possible, and that can effectively utilize the laser beam output for recording. The purpose is to provide a recording device.

According to the invention, the above-mentioned object is solved by the following device. That is, a laser beam is modulated by a signal having information according to the information, the modulated laser beam is deflected and scanned to expose a photoreceptor, and the information is recorded using electrophotographic technology. In this laser beam recording device, there is a recording laser beam light that is output when there is a signal that should cause the laser beam light to reach the photoconductor, and a signal that should block the light from reaching the photoconductor. a modulator, characterized in that non-recording laser beams output when The non-recording laser beam reflected from the non-recording light reflecting means guides the electrical signal to a micromirror that can be deflected to an angle corresponding to the applied electric signal, and the non-recording laser beam reflects the non-recording light at least at a plurality of locations in the deflection area. A laser beam recording apparatus is provided that includes a position detection means for detecting which position on a photoreceptor is scanned by a laser beam and controlling generation of the information signal.

Hereinafter, the present invention will be explained in detail with reference to the drawings. FIG. 1 is a schematic explanatory diagram showing the principle arrangement of a laser beam modulation/deflection device in a laser beam recording apparatus according to the present invention.

1 is a laser device, 2 is an optical modulator, 3 is a reflecting mirror,
4 is a galvanometer-like micromirror, and 5 is a drive circuit for the micromirror. 6 and 6' are first-order diffracted lights that appear on the output side as a result of being modulated by the optical modulator 2, and 7 and 7' are zero-order diffracted lights. Further, 8 is a photoreceptor, 9 is a reflecting mirror that reflects only the zero-order diffracted light, 10 is a photoelectric conversion device, 11 is a clock pulse generator, and 12 is a buffer memory.

A laser beam emitted from a laser device 1 is input to a modulator 2 capable of modulating the laser beam using an electrical signal. As such a modulator, a Bragg diffraction modulator using an acousto-optic effect or an electro-optic effect is generally known. The output of the modulator 2 is ideally such that the input signal is e.g.
When the TTL level is “1”, the first-order diffracted light 6
The output of 0 appears most strongly, and when it is “0”, 0
It is required that only the second-order diffracted light 7 appears on the output side.

Both the 1st-order diffracted light 6 and the 0th-order diffracted light 7 are caused by a reflecting mirror 3 in response to an electric signal applied to the drive circuit 5, and are oscillated by an angle proportional to the intensity of the electric signal. Guided by mirror 4. Generally, in order to meet the demands for high-speed recording, the output of the drive circuit 5 of the micromirror 4 is an electrical signal that causes the micromirror to vibrate in a sinusoidal manner. When the mirror is vibrated sinusoidally in this way, it has the advantage of being able to use the mechanical resonance of the mirror in addition to high speed, and in the case of a resonant mirror, it is possible to vibrate the amplitude and phase repeatedly. The properties are extremely stable. The first-order diffracted light 6 and the zero-order diffracted light 7 are separated by the micromirror 4.
Both are reflected and emitted toward the photoreceptor 8. 1 deflected by said mirror 4
The next diffracted light 6' directly enters the photoreceptor 8, but
The deflected zero-order diffracted light 7' is reflected by a reflecting mirror 9 located between the mirror 4 and the photoreceptor 8 and guided to the photoelectric conversion device 10. The signal obtained from the photoelectric conversion device 10 is applied to a clock pulse generator 11 to generate clock pulses for reading information from the buffer memory 12.

2 and 3 show in principle how information is read from the buffer memory 12 and how it is recorded on the photoreceptor.

FIGS. 2 and 3 are explanatory diagrams of the form of signals at the positions of the reflecting mirror and the photoelectric conversion device. Reference numeral 13 denotes a light-shielding stripe provided on the reflecting mirror to selectively prevent reflection of laser light. FIG. 3a shows a time-series clock pulse obtained from the photoelectric conversion device 10 when the reflecting mirror 9 is scanned with a laser beam, and b shows a signal to be actually recorded on the photoreceptor. Further, c is a signal pulse train to be applied to the optical modulator in the presence of such signals a and b.

When the laser beam light (0th order diffracted light) is scanned by the reflecting mirror 9 provided with the light-shielding stripes 13 that selectively prevent reflection of the laser beam as shown in FIG. 2, the photoelectric conversion device 10 generates a signal as shown in FIG. 3a. is obtained. Ideally, the spatial frequency of the light-shielding stripes 13 should correspond to a pixel, which is the minimum recording unit to be recorded on the photoreceptor. In such a case, it is easy for those skilled in the art to infer that this waveform a can be used as a clock pulse for reading out a signal for recording from a buffer memory in which information to be temporarily recorded is stored using this waveform. It is about to be done. Assuming that the signal waveform to be recorded on the photoreceptor 8 is as shown in b in relation to the waveform a, the modulation signal to be applied to the optical modulator under such conditions is as follows. The waveform should look like c. That is, under the condition that the level of waveform b is "1", the input signal triggered by the clock pulse and applied to the optical modulator 2 must also be at level "1". In this way, when the input level applied to the modulator 2 is "1", the 0th order diffracted light becomes a very weak light even if it is not completely erased. For this reason, each pulse width in the waveform of FIG. 3c has an appropriate value. In other words, if the pulse width becomes too long and extends to the next clock pulse signal, the 0th order diffracted light for generating a clock pulse at an adjacent pixel will no longer exist, resulting in a 1:1 ratio between the pixel and the clock pulse. It becomes impossible to deal with the situation. This means that the dot due to the light spot will not be recorded at the correct position, which must be avoided at all costs. Therefore, the trailing edge of the pulse width of waveform c must naturally occur at the same time as or before the leading edge of the subsequent clock pulse that would normally occur.

As described above, the micromirror 4 is generally driven to vibrate in a sinusoidal manner.
In this case, if we consider the partial frequency of the clock pulse when one horizontal scanning line is scanned, we can see that the scanning speed of the light spot is slow in the peripheral area of the photoreceptor.
Since it is faster in the center, the clock pulse generation frequency is low in the periphery and high in the center.

Even if the frequency of the clock pulse of waveform a varies from place to place, the pulse width of waveform c should be kept constant. The reason is that by making the pulse width of waveform c constant, the light energy input to each pixel on the photoreceptor becomes approximately constant, and the density recorded on the photoreceptor can be kept constant. It is. In addition, another advantage obtained from the above explanation is that the laser beam can be deflected pixel by pixel. Both the back and forth vibrations of the mirror can be used for recording, and the recording speed can be doubled.

In the above explanation, we have taken as an example the case where light-shielding stripes are provided on the reflecting mirror in order to generate clock pulses in units corresponding to pixels, which are the units of the smallest image to be recorded, but they do not necessarily correspond to each pixel. There is no need to generate clock pulses. In other words, there is a method in which a calibration pulse is output for each pixel every several pixels, and the clock pulses are successively corrected based on the correlation between the pulses, or in the case of a line printer, only the pulses representing the position of characters are output. It is possible to obtain an undistorted image even if the two ends are compared with the center by sequentially generating clock pulses based on the correlation between the pulses and knowing the position at which the characters begin to be written. can. Furthermore, although a detailed explanation will be omitted, even in this method, in which a calibration pulse is issued for every plural pixels and the clock pulse is successively corrected based on the correlation between the pulses, the reciprocation of the vibrating micromirror is It is possible to use the motion of for recording.

As described above, according to the present invention, the first diffracted light that is output when there is an information signal that causes the laser beam light to reach the photoreceptor by the optical modulator, and The laser beam is divided into a second diffracted beam that is output when there is an information signal that should be blocked from reaching the body, and the first and second diffracted beams are polarized and scanned by a minute vibrating mirror. Since the photoreceptor is exposed to the first diffracted light and the second diffracted light is photoelectrically converted to control the clock pulse, the photoreceptor and the photoelectric conversion element are The laser beam applied to the photoreceptor can be strengthened, and therefore the image forming characteristics on the photoreceptor and the generation of the clock pulse control signal on the photoelectric conversion element can be ensured. Moreover, the second
The diffracted light is interrupted in correspondence with the scanning position by the light-shielding stripes provided in the deflection scanning area, so the output signal obtained by photoelectrically converting this is connected to the scanning position of the first diffracted light for recording. By controlling the generation of the clock pulse using this photoelectric conversion output signal, this clock pulse can be made to correspond correctly to the scanning position of the first diffracted light. Therefore, if the information signal given to the optical modulator is controlled by this clock pulse, it is possible to control the laser beam at the correct scanning position and record the correct image, thereby reducing the mechanical resonance of the vibrating mirror. The sinusoidal vibration mode used enables stable high-speed recording. Furthermore, recording by the first diffracted light is generated when the second diffracted light is in an area blocked by the light-shielding stripes, so that the clock pulse control and the recording control do not interfere with each other. As a result of the above, the goal is to effectively utilize laser beam light for recording by using common parts without requiring special technology such as high-speed rotating polygon mirrors and F-theta lenses as in the past. The effect is that a laser beam recording device that can perform the following steps can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a schematic explanatory diagram showing the principle arrangement of laser beam modulation and deflection devices in the laser beam recording device according to the present invention, Fig. 2 is a schematic diagram of a photoelectric conversion device, and Fig. 3 is a signal waveform. It is a diagram. 1... Laser device, 2... Light modulator, 3... Reflector, 4... Galvanometer-like minute mirror, 5
...Drive circuit, 6,6'...1st-order diffracted light, 7,
7'...0th-order diffracted light, 8...photoreceptor, 9...reflector, 10...photoelectric conversion device, 11...clock pulse generator, 12...buffer memory, 13...shading stripe.

Claims (1)

[Claims] 1 A means for emitting a laser beam, a means for modulating the laser beam according to information with an information signal, a means for deflecting and scanning the modulated laser beam, and a means for receiving the deflected and scanned laser beam. In a laser beam recording device equipped with a photoconductor, the laser beam is divided into a first diffracted beam that is output when there is an information signal that causes the laser beam to reach the photoconductor, and a first diffracted beam that is output before the photoconductor. an optical modulator that deflects and outputs the second diffracted light in a direction that is different from the second diffracted light by a small angle from the second diffracted light that is output when there is an information signal that should be blocked from reaching the laser beam; means for guiding both the first diffracted light and the second diffracted light to a micro-oscillating mirror that deflects and scans at an angle corresponding to an applied electric signal; means for generating a clock pulse while being controlled by a light-shielding stripe provided in the scanning direction in a scanning area by the diffracted light, and a photoelectric conversion output signal of a second diffracted light interrupted by the light-shielding stripe; A laser beam characterized by comprising means for generating a first diffracted light by applying recorded information to the optical modulator in a region where the controlled second diffracted light is blocked by the light-shielding stripes. Recording device.