JPS61285423A - Optical scanning device - Google Patents

Abstract

PURPOSE:To simplify the constitution of an optical scanning device by providing a photoelectric converter with many photoelectric conversion parts arrayed along its scanning line with equal intervals and controlling the driving of a light source for generating modulated light through the photoelectric converter. CONSTITUTION:The photoelectric converter 2 is formed on the upper part of a photosensitive drum 1 and a deflector 3 is positioned in the front of the drum 1 and the converter 2. A polygon mirror, for example, is used for the deflector 3 to control light sources 4, 5 consisting of semiconductor laser oscillators, for example, respectively so as to generate modulated light L3 directly from the light source 4 and generate continuous light L4 from the light source 5 by controlling their oscillation in accordance with a picture signal. The courses of the modulated light L3 and the continuous light L4 irradiated to the deflector 3 are turned to a photosensitive body 1 and the photoelectric converter 2 and both the light rays L3, L4 are moved along respective scanning lines 6, 7 on the photosensitive body 1 and the photoelectric converter 2. The photoelectric converter 2 is provided with many photoelectric conversion parts 8 along the scanning line with equal fine intervals to irradiate beam spots on the scanning line of the photosensitive body 1 with equal intervals.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical scanning device used in an optical printer or the like.

[Prior Art] A known optical scanning device includes a light source such as a laser that generates a light beam, and a deflector that causes the light beam to scan along a scanning line of a photoreceptor.

As the deflector, a rotating polygon mirror that rotates at a constant speed, a galvanometer mirror that rotates in a sine vibration mode with a constant amplitude, or the like is used. FIG. 1 shows an example in which a rotating polygon mirror a is used as a deflector. The light beam L1 from the light source is changed by a rotating polygon mirror a and is irradiated onto the scanning surface of the photoreceptor as a beam spot. This beam spot moves on the scanning surface in the range from the scanning start point x 1 to the scanning end point x 2 as the rotating polygon mirror a rotates. Assuming that the distance from the surface of the rotating polygon mirror a to the scanning surface is 1, the position X of the beam spot on the scanning surface when the deflected beam L2 is deflected at an angle θ with respect to the scanning center line is 1. It is expressed as tanθ. That is, the position of the beam spot is not proportional to the angle .theta. but proportional to tan .theta., and as the resultant dots approach the scanning start point X1 or the scanning start point x2, the distance between the dots becomes wider than in the center.

If a galvano mirror is used as a deflector, on the other hand, the dot spacing will be wider at the center of the scanning line than at both sides.

For this reason, conventionally, an optical correction device such as an fθ lens or an arcs inθ lens is provided between the deflector a and the scanning surface in order to move the beam spot at a constant speed on the scanning surface. Ta. Furthermore, in laser printers, when obtaining modulated light, a beam spot has been moved at a constant speed on a scanning surface by changing the period of a clock pulse.

[Problems to be Solved by the Invention] When correcting the position of a beam spot using an optical correction device, the optical correction device is usually composed of a plurality of lens groups, and the position adjustment of each lens is extremely complicated. It requires a lot of time and effort. In addition, the cost of manufacturing increases because the optical correction device is expensive.

When changing the period of the clock pulse, the circuit configuration becomes complicated, and there is an error in the interval between the beam spots in the scanning direction, and a huge memory capacity is required to reduce this error.

Therefore, a first object of the present invention is to enable a beam spot to be scanned at a uniform speed along a scanning line on a photoreceptor without using an optical correction device.

A second object of the present invention is to make it possible to easily obtain a clock pulse whose period changes for uniformly scanning a beam spot along a scanning line on a photoreceptor.

A third object of the present invention is to provide a low-cost optical scanning device that can uniformly scan a beam spot along a scanning line on a photoreceptor.

Means for Solving the Problem In addition to modulated light that is scanned along a scanning line on a photoreceptor via a deflector, continuous light is used. This continuous light is scanned along the scanning line on the photoelectric conversion device via the deflector. This photoelectric conversion device has a large number of photoelectric conversion parts arranged at minute intervals along the scanning line. When a semiconductor laser oscillator is used as the light source, the semiconductor laser oscillator is controlled via the output of the photoelectric conversion device, and when a gas laser oscillator is used as the light source, the modulator is controlled via the output of the photoelectric conversion device.

[Function] When the deflector is a rotating polygon mirror, the photoelectric conversion device
Output pulses are generated at a period proportional to lanθ. By controlling the modulated light corresponding to the image signal in synchronization with the output of the photoelectric conversion device, beam spots or dots irradiated along the scanning line on the photoreceptor are formed at equal intervals.

[Example] In FIG. 2, a photoelectric conversion device 2 is provided above a photoreceptor (photosensitive drum) 1. A deflector 3 is located in front of the photoreceptor 1 and the photoelectric conversion device 2. In this example, a rotating polygon mirror that rotates at a constant speed is used as the deflector 3. In this example, semiconductor laser oscillators are both used as the two light sources 4 and 5. The light source 4 has its oscillation controlled in response to the image signal, and emits modulated light L.
3 directly, and the light source 5 generates continuous light L4.

The modulated light L3 and the continuous light L4 irradiated toward the deflector 3 change their light paths toward the photoreceptor 1 and the photoelectric conversion device 2. Therefore, as the deflector 3 rotates, the modulated light 3 and the continuous light L4 move along each scanning line 6, 7 on the photoreceptor 1 and photoelectric conversion device 2. The photoelectric conversion device 2 includes a large number of photoelectric conversion units 8 arranged at minute equal intervals along the scanning line 7 . In this embodiment, the photoelectric conversion device 2, as shown in FIG.
1 and a transparent electrode 12 formed on its upper surface, and this transparent electrode 12 includes a large number of comb-like electrode elements 12a.
have. The number of electrode elements 12a, that is, the number of photoelectric conversion units 8, corresponds to the number of dots to be formed on the scanning line 6 of the photoreceptor 1, and the pitch thereof is determined by the distance from the deflector 3 of the photoelectric conversion device 2. . For example, as in this embodiment, when the photoelectric conversion device 2 is placed at a distance equal to the distance from the deflector 3 to the scanning line 6 of the photoreceptor 1, the pitch of the photoelectric conversion unit 8 is It is equal to the pitch of dots to be formed on one scanning line 6.

A bias voltage VB is supplied to the transparent electrode 12, and the entire surface electrode 10 is connected to a comparator 13.

The comparator 13 has a reference voltage source 1 that provides a reference level to it.
4 is connected. When the light beam is scanned along the scanning line 7 on the photoelectric deflection device 2, the light beam strikes the transparent electrode 12.
When the comb-shaped electrode element 12a is irradiated, the electrical resistance of the photoconductive thin film 11 between the electrode element 12a and the entire surface electrode 1O decreases, and a bias voltage is supplied to the comparator 13. 13 generates a level 1 pulse.

Since the moving speed of the light beam moving along the scanning line 7 of the photoelectric conversion device 2 is proportional to tanθ (see FIG. 1 for θ), the period of the pulse train generated by the photoelectric conversion device 2, that is, the comparator 13 is 1. /lanθ. The comparator 13 is connected to a control circuit 15, and the light source 4 is controlled via the control circuit 15 by an AND signal of the output of the comparator 13 and the image signal.

Therefore, the modulation period of the modulated light beam 3 generated by the light source 4 is 1
/lanθ, and as a result, the beam spots are irradiated on the scanning line of the photoreceptor 1 at equal intervals.

FIG. 4 shows the main part of an embodiment in which a continuous oscillation gas laser oscillator such as a He-Ne laser or an Ar laser is used as a single light source 16.

Continuous light generated from the laser light source 16 is transmitted to the half mirror 1
The beam is split into two via a beam splitter 19 consisting of a beam splitter 7 and a total reflection mirror 18, one of which is connected to a modulator 20.
is converted into modulated light.

The control of the modulator 15 is performed by the control circuit 15 shown in the third figure in the same manner as in the previous embodiment. The other configurations are substantially the same as those of the above embodiment.

The present invention is specified only by the claims, and various modifications can be made without departing from the technical idea thereof.

For example, the present invention is similarly applicable to the case where the deflector 3 is a galvanometer mirror. In addition to the above embodiments, the photoelectric conversion device 2 may also include a silicon semiconductor photodiode array, a phototransistor array, or a charge-coupled device (COD).
It is also possible to use arrays. The installation positional relationship between the photoreceptor 1 and the photoelectric conversion device 2 is not particularly limited.

This is because the purpose of the photoelectric conversion device 2 is to obtain a pulse train with a period proportional to 1/lanθ, and the positional relationship with the photoreceptor 1 can be freely changed for this purpose. For example, the photoelectric conversion device 2 may be placed closer to the deflector 3 than the position shown in the second diagram, or vice versa.

When the photoelectric conversion device 2 is moved away from the deflector 3, the pitch of the photoelectric conversion sections 8 on the scanning line 7 can be increased accordingly, so that manufacturing of the photoelectric conversion device 2 becomes easier. Roughly,
In FIG. 2, the position of the light source 5 may be changed so that the continuous light L4 is irradiated to a surface different from the surface 3a to which the modulated light 3 is irradiated, for example, 3b. In this case, the photoelectric conversion device 2 would be provided on the opposite side of the photoreceptor 1 with respect to the deflector 3.

The photoreceptor 1 may be in the form of a drum or in the form of a sheet which is endlessly passed between two rollers.

[Effects of the Invention] According to the optical scanning device according to the present invention described above, in order to form dots at equal intervals, an expensive optical correction device that requires positional adjustment is not provided between the deflector and the photoreceptor. Alternatively, there is no need to provide any special circuit for changing the period of light modulation. Therefore, the configuration of the optical scanning device is simpler than that of the conventional device, and it can be manufactured at low cost. Roughly speaking, the position of the dot on the photoreceptor is determined by the output of the photoelectric conversion device, so it is not affected by rotational fluctuations of the deflector. Therefore, higher quality recording is possible. Since the conversion device can also be used to detect the beam position, the beam position detector used in the past can be omitted.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the deflection of a light beam when a rotating polygonal mirror is used as a deflector, Fig. 2 is a perspective view showing an embodiment of an optical scanning device according to the present invention, and Fig. 3 is an illustration of a photoelectric conversion device. FIG. 4 is a circuit diagram showing a cross-sectional structure, and a perspective view showing another embodiment of the light source section. 1... Photoreceptor 2... Photoelectric conversion device 3...
Deflector 4...First light source 5...Second light source 6...Scanning line 7 on photoconductor...Scanning line 8 on photoelectric conversion device...Photoelectric conversion unit 16... Single light source 19...
Beam splitter 20... Modulator and above Figure 1 Figure 4

Claims (2)

[Claims] (1) A first light source that generates modulated light corresponding to an image signal, a second light source that generates continuous light, and photoelectric conversion of the continuous light by transmitting the modulated light along a scanning line on a photoreceptor. a deflector for scanning along a scanning line on the device; the photoelectric conversion device has a large number of photoelectric conversion sections arranged at equal intervals along the scanning line; An optical scanning device characterized by controlling driving of the first light source. (2) A light source that generates continuous light, a beam splitter that splits this continuous light into two, and converts one of the two continuous lights into modulated light corresponding to an image signal via this beam splitter. a modulator that scans the modulated light along a scanning line on a photoreceptor, and a deflector that causes the other of the continuous light that is split into two parts via the beam splitter to scan along a scanning line on a photoelectric conversion device. The photoelectric conversion device has a large number of photoelectric conversion units arranged at equal intervals along the scanning line, and the modulator is controlled via the output of the photoelectric conversion device. scanning device.