JPS59193413A - Optical beam scanner - Google Patents

Abstract

PURPOSE:To decrease a semiconductor laser and a temperature control device, and to execute a beam scanning at a low cost by dividing an optical beam from a sigle semiconductor laser into two beams by means of time division, and making them incident to one polyhedral mirror. CONSTITUTION:An optical circulator 9 causes a Faraday effect by an input signal from the outside, and rotates a polarizing surface of an incident light by 90 deg.. Among optical beams which are made incident to a polarized beam splitter 10, a polarized component in the direction parallel to a revolving shaft 11 of a rotary polyhedral mirror 3 is reflected to the right, reflected again by a mirror 12, and advances to the polyhedral mirror 3. Thereafter, said component passes through an image forming optical system 4a, goes forward to the lower direction by a mirror 5a, and an optical spot scanning is executed on a photosensitive drum 6a. Also, a polarized component in the direction falling at a right angle with the revolving shaft 11 of the polyhedral mirror 3 passes through a mirror 5b, and executes an optical spot scanning to a photosensitive drum 6b. By repeating on and off of a signal to the optical circulator 9, the photosensitive drums 6a, 6b are scanned by a modulated optical beam in accordance with a picture signal, an electrostatic latent image corresponding to a picture is formed, and the optical beam scanning is executed at a low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a light beam scanning device comprising a light source such as a laser and a light deflector using a rotating polygon mirror or a vibrating mirror.

FIG. 7 is a diagram illustrating a conventional light beam scanning device used in a colorless laser beam printer as an output device for a computer or the like using the light beam scanning device. A light beam from a semiconductor laser /a whose light intensity is modulated in synchronization with the output of a computer or the like is deflected by a rotating polygon mirror 3 rotated by a motor unit.

Further, the light beam passes through the imaging optical system a, is reflected by the mirror 5a, is directed downward, and rotates to scan the electrophotographic photosensitive drum Oa with a light spot along the scanning line A in the figure. . A latent image is electrostatically formed on the photosensitive drum Oa according to the amount of laser light, and after being developed black by a developing device (not shown), it is transferred onto the paper 7.

Subsequently, the paper 7 is sent to the photosensitive drum by a downward feeding means such as a feeding belt g. The photosensitive drum b is subjected to optical spot scanning by the modulated light beam from the semiconductor laser f/b in the same manner as described above, and then developed in red and transferred onto the paper 7. After that, go to paper 7! The image is fixed by a fixing device (not shown), and color prints of black and red can be made.

Such a light beam scanning device that performs scanning using a plurality of light sources requires semiconductor lasers corresponding to the number of colors when applied to, for example, a Rade beam printer. However, semiconductor lasers are expensive, and it is undesirable that the temperature of the semiconductor laser increases and the wavelength of the light beam from the semiconductor laser shifts. This is because the sensitivity characteristics of a photosensitive drum scanned by a light beam from a semiconductor laser are wavelength dependent, and therefore the sensitivity differs depending on the wavelength of the light beam from a semiconductor laser.

Therefore, the temperature of the semiconductor laser is normally adjusted to keep the semiconductor laser at a constant temperature so that the wavelength of the light beam of the semiconductor laser does not shift. As the element used for this temperature adjustment, an electronic cooling element that utilizes the Peltier effect is used, and a control circuit for this temperature adjustment is also used, which has the disadvantage that the temperature adjustment device itself is expensive. Ta.

The present invention has been made in view of the above points and to eliminate the above drawbacks, and is an inexpensive light beam that scans with a plurality of light beams from a single light source used in color laser beam printers, etc. The object of the present invention is to provide a scanning device.

Below, embodiments of a light beam scanning device according to the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the present invention.

In the figure, an optical circulator tower is provided immediately after the semiconductor laser via a collimator lens (not shown).

When the optical circulator tower receives an external signal, it causes the Faraday effect and changes the polarization plane of the incident linearly polarized light to 9
It has the function of rotating by 0°. There is a polarizing beam splitter 10 behind the optical circulator 9, and among the light beams incident on the polarizing beam splitter 10, there is a direction parallel to the rotation center of the rotation axis of the polygon mirror 3 in the figure (hereinafter simply referred to as ""). The polarized light component in the parallel direction (not abbreviated as "") is reflected to the right, then reflected again by the mirror 2, and proceeds to the rotating polygon mirror 3 rotating in the direction of the arrow in the figure, where it is deflected. , passes through the imaging optical system 4a, is directed downward by the mirror 5aK, and scans the photosensitive drum 2 with a light spot.

This optical path will be referred to as the first optical path.

Also, among the light beams incident on the polarizing beam nucleator 10, the polarized component in the direction perpendicular to the rotation axis of the rotating polygon mirror 3 (hereinafter simply referred to as the perpendicular direction 11) travels straight in the direction of the arrow shown in the figure. A light spot is scanned on the photosensitive drum through the rotating polygon mirror 3, the imaging optical system/lb, the mirror, and tb. This optical path is called the 7th optical path.
is the paper, and is the feed belt that conveys the paper/3. ,/'l
These are for receiving a horizontal synchronization signal with photosensors placed beside the photosensitive drums Otoa and Otsu, respectively. Note that known equipment used in the electrophotographic process, such as a charging device, a developing device, a fixing device, etc., are not shown.

Assume that the modulated light beam from the semiconductor laser is linearly polarized light having only two components in the parallel direction. When no signal is input to the optical circulator 9 via a collimator lens (not shown), the polarization direction of the modulated light beam from the semiconductor laser does not change, and this light beam is reflected by the polarization beam splitter 10 and is The light is incident on the photo sensor 3 through the optical path 1, and then the light spot scans the photosensitive drum 1, which is rotating in the direction of the arrow in the figure.

In addition, in the figure, the locus of light spot scanning is drawn.

Next, when a signal is applied to the optical circulator, the polarization direction of the modulated light beam from the semiconductor laser is rotated by 90 degrees to become linearly polarized light in "one orthogonal direction."

In this case, the modulated light beam goes straight through the polarizing beam splitter 10 and passes through the optical path of the photo sensor/ll.
-, and then the light spot scans the photosensitive drum which is rotating in the direction of the arrow in the figure.

Also in this case, the locus of the optical spot scan is drawn in the figure. That is, by repeating ON-OFF of the signal to the optical circulator tower, the photosensitive drums 4a, 4b
are repeatedly scanned with a modulated light beam in accordance with the respective image signals, and electrostatic latent images corresponding to the images of each color component are formed along their circumferential surfaces.

After this, the feeding belt g is
Color printing is performed on the paper 7 moving in the direction of the arrow shown in the figure. In other words, it is possible to obtain a single optical spot scan using seven semiconductor lasers and seven sets of deflectors.
This provides an inexpensive light beam scanning device that can be applied to laser beam printers and the like. Since the ON-OFF operation of the optical circulator 9 can be performed at extremely high speed, one photosensitive drum can be alternately scanned with multiple lights.

FIG. 3 is a block diagram of an embodiment of a control system for controlling the light beam scanning device shown in FIG. 2. In FIG. 3, / is a semiconductor laser, U is a motor for rotating the rotating polygon mirror 3, 9 is an optical circulator, /3. /'
1 is a photosensor, and the arrangement thereof is as described above in FIG. Ω.

Note that other optical systems are not shown for simplicity. /'? is a horizontal synchronization circuit, which inputs the detection signal of the photosensor /3 or /ll located at a position that corresponds to the start of image writing on each photosensitive drum and outputs a horizontal synchronization signal. . 20 is a controller which inputs the horizontal synchronization signal from the horizontal synchronization generating circuit /9 and after a predetermined period of time gives a control signal to the semiconductor laser drive circuit 7g connected to the semiconductor laser '/ to generate an image of the semiconductor laser /. This is a device that starts driving with a signal. Note that this image signal is output from, for example, a facsimile, a word processor, a computer device, etc., and is input to the controller 20. /7 is an optical circulator drive circuit for applying a signal to the optical circulator according to the timing signal from the controller 0.

/RO is a motor drive circuit for controlling the motor unit.The speed of the motor is detected by an encoder /S, and this detected signal is fed back to the motor drive circuit /I.

After scanning is completed, the controller 20 gives a timing signal to the optical circulator drive circuit/7 to place the optical circulator in either selected state. The controller 20 also provides a rotation control signal to the motor drive circuit/B to control the rotation speed of the morus as well as the rotation speed of the rotating polygon mirror 3. The rotational speed of this motor λ is detected by an encoder/S, and is constantly fed back to the motor drive circuit/B to keep the rotational speed of the motor constant.

The horizontal synchronization generating circuit /9, which receives the detection signal from the photo sensor /3 or /ll- which receives the laser light from the semiconductor laser / reflected from the rotating polygon mirror 3, outputs a horizontal synchronization signal to the chondrolus □. . After a predetermined short time from this signal, the controller 20 gives a control signal to the semiconductor laser drive circuit /g to start driving the semiconductor laser / in accordance with the distorted image signal. As described above, the modulated laser light from the semiconductor laser scans a predetermined selected photosensitive drum via the optical circu tower and the rotating polygon mirror 3 as described above. By repeating the above process, the light beam scanning device shown in FIG. 2 scans the light beam while being controlled.

However, if there is no need to alternately switch the optical path of the light beam as described above in Fig. A light beam scanning device that is applied to a laser beam printer that performs optical spot scanning, that is, a second
In the figure, if the distance between the two photosensitive drums is sufficiently large compared to the length of the paper 7 in the feeding direction, an optical beam scanning device can be used instead of the optical circulator 9 or the polarizing beam splitter 10. The method shown in FIG. 9 can be used. In FIG. 9, the light beam of the semiconductor laser is passed through a collimator lens (not shown) to a rotating mirror 2 having a rotation axis 2.
．． 2 to the right in the figure, passes through mirror /2, is deflected by rotating polygon mirror 3, and then heads toward imaging optical system /la. When the rotating mirror 22 is rotated to the position indicated by the dashed-dotted line in the figure, the semiconductor laser beam/carano optical beam travels straight through a collimator lens (not shown), enters the rotating polygon mirror 3, and is deflected toward the imaging optical system +b. . The subsequent processes are clear from the above examples and will be omitted. In the case of this embodiment, since the optical path switching is mechanical, the switching speed is slow. Therefore, as described above, it can only be used in the case of a system in which the optical path is switched after the optical spot scanning of the first photosensitive drum is completed, and the optical spot is scanned on the first photosensitive drum. It is simpler than the embodiment shown in the figure. In addition, if a full-color laser beam printer is obtained, an Ω
By arranging seven more sets of the configurations shown in FIG. 3 and FIG. 3, a color laser beam printer capable of full-color printing can be constructed.

The same applies to the configuration shown in FIG.

In addition to this, the present invention also provides a semiconductor laser or a polarizing beam splitter without using an optical circulator in Figure Ω.
It may be rotated by 0°.

As described in detail, according to the present invention, a light beam from a single semiconductor laser is divided into two optical paths in a time-sharing manner and is incident on seven polygon mirrors, thereby eliminating the need for expensive components. It is possible to obtain a light beam scanning device at low cost without reducing the number of semiconductor lasers and its temperature adjustment device. Moreover, if this light beam scanning device is applied to a color laser beam printer, not only will the cost be reduced, but since a single semiconductor laser is used, the light beam from it will be time-divided. The wavelength and intensity of the 12 beams are the same, and the sensitivity of the photosensitive drum that receives this light beam is always constant, making it possible to print stable color images.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic perspective view showing a conventional light beam scanning device, and FIGS. 2 to 7 are explanatory diagrams showing each embodiment of the light beam scanning device according to the present invention. / is a semiconductor laser, 3 is a rotating polygon mirror, G a and G b are imaging optical systems, O a and O are photosensitive drums, 7 is paper, 9 is an optical circulator, 10 is a polarizing beam splitter, and N is a rotating It's a mirror. Patent applicant Canon Inc. -65- Figure 4

Claims (1)

[Claims] In a light beam scanning device comprising a single light source for generating a light beam and a single light deflector for deflecting the light beam, the light beam from the single light source is time-divided. The optical beam is divided into a plurality of optical paths and made incident on the single optical deflector to obtain a plurality of scanning light beams.
-Music scanning device.