JPS6364944B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention uses a light beam such as a laser beam,
The present invention relates to an improvement in an information recording device that can reproduce image information such as characters and graphics from a computer or the like at high speed.

Laser beam printers are excellent printers that not only can reproduce image information from computers etc. at high speed, but also have the advantages of low noise and good printing quality.

To explain using Figure 1, laser oscillator 1
The oscillated laser beam La is guided to the input aperture of a light beam modulator 3 via a reflecting mirror 2. The modulator 3 uses an acousto-optic element or the like, and the laser beam is subjected to intensity modulation in the modulator 3 according to an input signal to the modulator 3 based on image information from a computer or the like. The laser beam emitted from the modulator 3 is bent vertically upward by a reflecting mirror 5, further bent horizontally by a reflecting mirror 6, and guided to a beam expander 7. The laser beam whose beam diameter has been expanded by the beam expander 7 is incident on a rotating polygon mirror 8 having a plurality of mirror surfaces driven by a motor 11, and is horizontally deflected by the rotating polygon mirror 8. Beam detector 1
0 consists of one reflecting mirror, a small entrance slit, a photoelectric conversion element with a quick response time (for example, a photo diode), and a waveform shaping circuit. A beam detector 10 detects the position of a laser beam 12 scanned by a rotating polygon mirror 8 through an imaging lens 9, and uses this detection signal to perform modulation to provide desired optical information onto a photosensitive drum 4. The start timing of the input signal to the device 3 is determined. Figure 2 is the timing chart. A timer b starts timing in response to a detection signal a from the beam detector 10. When the timer b has elapsed for a predetermined time, input of the signal c based on the image information to the modulator 3 is started, and desired optical information is written onto the photosensitive drum 4. As a result, it is possible to greatly reduce synchronization errors in horizontal signals caused by errors in the dividing accuracy of each reflective surface of the rotating polygon mirror 8 and uneven rotation of the motor 11, and it is possible to obtain high-quality images and to obtain a high-quality image. The tolerance range of accuracy required for the motor 11 can be increased.

As described above, the modulated laser beam 12 is irradiated onto the photosensitive drum 4, visualized by an electrophotographic processing process (not shown), and then transferred to plain paper.
The image is fixed (not shown) and output as a hard copy.

Next, the beam detector 10 will be explained in more detail with reference to FIGS. 3 and 4. A mirror 13 for reflecting the laser beam 12 is attached to a mirror holding plate 14 at a portion before the laser beam 12 to be scanned enters the area of the photosensitive drum 4 . The inclination of the mirror 13 can be adjusted by changing the screwing amount of the screw 14a. A slit 15 is arranged on the focal plane of the imaging lens 9 on the output side of this mirror, and the slit 15 is provided so as to be substantially perpendicular to the scanning direction of the laser beam being scanned. Behind the slit 15 is a light receiving element 16 having a photoelectric conversion function.
is placed. The light receiving element 16 is soldered to the waveform shaping circuit board 18, and the waveform shaping circuit holding board 1
It is fitted into the hole of the positioning part 17a provided in 7 and is positioned. Now, the laser beam 12 transmitted through the imaging lens 9 irradiates the mirror 13 before scanning the photosensitive drum 4, and the reflected light from the mirror 13 forms an image on the slit 15. Therefore, the fourth
As shown in Figure c (Figures 4a and 4c are views of the slit 15 and light receiving element 16 from the direction A in Figure 3), the beam spot 19 that is imaged on the slit as the laser beam is scanned is indicated by the arrow. It moves in a direction perpendicular to the slit as shown in FIG.
generates output like . The meaning of slit 15 will be explained. Now, suppose that there is no slit 15 in front of the light receiving element 16 as shown in FIG. 4a. When the beam spot 19 scans the light-receiving element 16 in this state, the output waveform is transmitted to the detection portion 20 of the light-receiving element 16.
Due to disturbances in the green color and distortion of the lens surface in front of the light receiving element 16, an output waveform with a long rise time _tr1 as shown in FIG. 4b results. If the rise time is long and the output level changes as shown in the dashed line due to differences in reflectance of the mirror surface of the rotating polygon mirror 8, etc., the position where the slice level rises and cuts the waveform changes in the time axis direction, so the beam A difference occurs in the time for detecting the laser beam 12, making it difficult to detect the position of the laser beam 12 with high precision. On the other hand, as shown in FIG. 4c, the light receiving element 1
If a slit 15 narrower in width than the detection portion 20 of the light receiving element 16 is placed in front of the rotating polygon mirror 6, a short output waveform with a rise time tr ₂ can be obtained due to the sharpness of the edge of the slit. Even if there is a difference in the reflectance of the mirror surfaces 8, etc., the variation in the time axis position of the rising waveform with respect to the slice level can be suppressed to a small value, and the position of the laser beam 12 can be detected with high precision. The reason for arranging the slit 15 on the focal plane of the imaging lens 9 is exactly the same; if the slit 15 is away from the focal plane, the diameter of the beam spot 19 at the slit position increases, and the rise time becomes This is because it becomes long as in Figure b. By providing the beam detector in this manner, the timing at which the laser beam starts recording on the photosensitive drum can be determined with high precision.

In FIG. 4c, the closing edge of the slit 15 (corresponding to the falling part of the output waveform) is also arranged inside the detection part 20 of the light receiving element 16. If you put it outside, the fourth
This is because the output waveform becomes double peaks as shown by the dotted line in FIG. b, which may cause the beam detector 10 to malfunction. If the circuit is free from such concerns, the light beam blocking end forming means need not be a slit, but may simply be an end face of a plate.

Now, in order to operate the beam detector stably, which is an important part of the information recording device,
The beam detection signal detected by the photodetector is electrically
The signal must be transmitted to the post-processing circuit without being affected by magnetic noise. For this purpose, it is most desirable that the photodetector be directly attached to the signal post-processing circuit, but space and
It is generally difficult to house a post-processing circuit in the beam scanning unit due to maintenance issues, and the beam scanning unit is usually equipped with a waveform shaping circuit 18, which is a circuit that shapes and converts the beam detection signal into a signal that is resistant to noise, as shown in Figure 3. A method is used in which the reshaped signal is transmitted to a signal post-processing circuit through a cable.

By the way, laser beam printers first appeared as large, high-speed output machines, but in recent years, semiconductor lasers have become available for use as light sources, and they have been used as output machines for word processors and office computers, as well as small, medium-speed printers. Its uses are expanding. When used as an output device for a word processor or office computer, it is better to keep the size as small as possible, considering that it will be placed in a small office.

The above-mentioned waveform shaping circuit is not a small component to be housed in the beam scanning section, and it becomes an obstacle when downsizing a laser beam printer. In particular, as shown in FIG. 5, the imaging lens 9 and the photosensitive drum 4
A reflecting mirror 20 is provided between the rotating polygon mirrors 8 and 8 to bend the direction of the scanning laser beam 12'.
If the distance between the photosensitive drum 4 is shortened and the size of the exterior 21 is made as compact as possible to achieve miniaturization, there may be little space available for the waveform shaping circuit.

In view of the above-mentioned drawbacks of conventional beam detectors, the present invention aims to provide a beam detector with a new configuration suitable for small-sized laser printers. This is due to the fact that it was used.

As described above, the present invention provides a photoelectric conversion element provided on a circuit board in an information recording apparatus that detects the position of a deflected light beam and determines the timing of starting modulation of the light beam with recorded information based on this detection signal. and an optical fiber that transmits the light beam from the light beam position detection section to the photoelectric conversion element.

The beam detector of the present invention will be explained with reference to FIGS. 6 and 7. A mirror 13 glued to a mirror holding plate 14 is provided before the laser beam 12 enters the area of the photosensitive drum 4, and its slit is scanned onto the focal plane of the imaging lens 9 on the exit side of this mirror. As in FIG. 3, the slit 15 is arranged substantially perpendicular to the scanning direction of the laser beam. An optical fiber 22 is arranged behind the slit 15 so that its central axis coincides with the direction of the laser beam reflected from the mirror. The light entrance end 22a of the optical fiber 22 is inserted into a hole 23a provided in the holding member 23 and fixed with adhesive. The holding member 23 is fixed to the fiber mounting plate 24 by a nut 25. On the other hand, the light emitting end 22b of the optical fiber 22 is placed in front of the light receiving element 16, and the light receiving element 16 is connected to the printer control circuit board 2.
6 is soldered. Now, the laser beam 12 that has passed through the imaging lens 9 is reflected by the mirror 13 and is imaged on the slit 15, as shown in FIG.
As the laser beam is scanned as shown in FIG.
The beam spot 19 moves in a direction perpendicular to the slit as shown by the arrow, and until it reaches the slit, it is blocked from entering the fiber 22c of the optical fiber, and as soon as it enters the slit, it enters the fiber 22c of the optical fiber. The light passes through the optical fiber 22 and enters the light receiving element 16, producing an output as shown in FIG. 7b. The rise time of the output waveform at this time is shown in Figure 4d.
It's short like tr ₂ . 22d in FIG. 7a is a coating of the optical fiber 22c.

Compared to conventional beam detectors, the beam detector with the new configuration described above allows the waveform shaping circuit board to be easily integrated into the printer control circuit board, so a small beam can be inserted into the beam scanning section. Only the light incident part of the fiber needs to be placed, and the beam detector in the beam scanning section can be made compact, which is very advantageous when downsizing the laser beam printer.

Furthermore, by using optical fiber,
Since the conventional signal transmission from the waveform circuit board to the printer control circuit board can be replaced from electrical signals to light, it has the advantage of being resistant to electrical and magnetic noise and increasing the reliability of the beam detector. By making the circuit board the same as the printer control circuit board, the number of parts can be reduced, and cost reductions can also be expected.

As described above, according to the present invention, it is possible to provide a compact beam detector that is optimal for small laser printers while maintaining the accuracy of conventional beam detectors.

In addition, in the explanation, a laser oscillator and a light beam modulator were used as a method to obtain a light beam modulated based on image information, but if a semiconductor laser is used as a laser oscillator, the semiconductor laser has a modulation function. Therefore, a light beam modulator is not required. The present invention also includes the case where a semiconductor laser is used as a laser oscillator in this way.

Further, although the structure of the optical fiber is not particularly limited in the description, the fiber constituting the optical fiber may be a bundle of a plurality of single fibers. Furthermore, the fiber may or may not be coated.

Furthermore, in the explanation, a case was described in which a mirror was placed between the imaging lens and the light beam blocking edge forming means to change the direction of the light beam, but the mirror may not be needed if there is no need to change the direction of the light beam. do not have.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a conventional example of an information recording device according to the present invention, FIG. 2 is a timing chart explaining the operation of the beam detector and modulator of the device shown in FIG. 1, and FIG. Fig. 1 is a perspective view of the beam detector of the device shown in Fig. 1, Fig. 4 is a view of the light receiving element seen from direction A shown in Fig. 3, and the output waveform of the light receiving element at that time, and Fig. 5 is a diagram to which the present invention can be applied. A partial view of an example of an information recording device, FIG. 6 is a perspective view of an embodiment of the beam detector of the present invention, and FIG. 7 is a view of the optical fiber seen from direction B shown in FIG. 6, and a light receiving element at that time. The output waveform of is shown. 10...Beam detector, 13...Mirror, 15
...slit, 16...light receiving element, 22...optical fiber.

Claims (1)

[Claims] 1. In an information recording device that detects the position of a deflected light beam and determines the timing to start modulating the light beam with recorded information based on this detection signal, a photoelectric conversion element provided on a circuit board and a light beam An information recording device comprising: an optical fiber that transmits a light beam from a position detection section to a photoelectric conversion element.