JPH02188713A - Image forming device - Google Patents

Abstract

PURPOSE:To easily generate excellent image information by constituting a horizontal synchronizing signal for plural fluxes of laser light in the case of forming the image information on the surface of a photosensitive body. CONSTITUTION:By shifting the main scanning direction of the flux of laser light by a specified amount (distance (b)) and utilizing a slit member 6 having a specified aperture part (width (a)), two fluxes of laser light are independently detect by one photodetector, time sequentially, to obtain the horizontal synchronizing signal for two fluxes of laser light. Plural fluxes of light from a laser unit 1 are reflected by an optical scanning means 3 and conducted to the surface of the photosensitive body 4 to perform scanning at the same time. At such a time, the image information is formed on the surface of the photosensitive body 4 by rotating the photosensitive body 4 in a subscanning direction with the rotation of the optical scanning means 3. According to the image information formed on the surface of the photosensitive body 4, a desired image is obtained in the process of development, transfer and separation as well as a conventional image forming device.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an image forming apparatus, and particularly to an image forming apparatus that uses a plurality of laser beams modulated by signals based on image information from a computer, facsimile, document reading bag, word processor, etc. The present invention relates to an image forming apparatus in which light is guided to a rotating polygon mirror serving as a light scanning means, and by rotating the rotating polygon mirror, the surface of a photoreceptor such as a photosensitive drum is scanned and image information is formed. .

(Prior Art) Conventionally, an image forming apparatus that utilizes a light beam from a semiconductor laser, which is optically modulated based on image information, was disclosed in Japanese Patent Laid-Open No. 6
This method has been proposed in JP-A No. 1-13759, Japanese Patent Laid-Open No. 102609-1980, and the like.

These image forming apparatuses convert image information into current pulses, emit a modulated light beam from a semiconductor laser, deflect the light beam through a rotating polygon mirror, and scan the surface of a photoconductor such as a photoconductor drum. Image information is formed on the surface of the photoreceptor while continuously rotating the photoreceptor in a sub-scanning direction perpendicular to the main-scanning direction.

At this time, the number of light beams that scan the surface of the photoreceptor is determined by using a single laser beam or a plurality of laser beams depending on the purpose.

In either case, 1, for example, JP-A-55-74519
As proposed in Japanese Patent Laid-Open No. 55-59474, etc., when forming an image, a photodetector placed near the photoreceptor surface detects the incident position of the laser beam in the main scanning direction on the photoreceptor surface. horizontal synchronization signal is obtained.

For example, when using a plurality of laser beams, the same number of photodetectors are used to obtain a horizontal synchronization signal from each photodetector.

For this reason, in conventional image forming apparatuses, especially when forming an image using a plurality of laser beams, the detection device for detecting the horizontal synchronization signal becomes complicated, and it is therefore very difficult to obtain high detection accuracy.

(Problems to be Solved by the Invention) The present invention provides a case in which a plurality of laser beams modulated based on image information are guided onto the surface of a photoreceptor through an optical scanning means, and an image is formed on the surface of the photoreceptor. , prevents the complexity of the detection device when obtaining the horizontal synchronization signal for the laser beam of 11 losses,
Another object of the present invention is to provide an image forming apparatus that can form good image information while preventing a decrease in detection accuracy of a horizontal synchronizing signal.

(Means for Solving the Problems) In the present invention, a plurality of laser beams modulated based on image information are guided onto the photoreceptor surface via an optical scanning means, and the photoreceptor surface is scanned to form an image. When forming information, the incident positions of the plurality of laser beams incident on a predetermined position on the photoreceptor surface are sequentially detected in time series by a photodetector through a slit member having a predetermined shape of the entrance, and It is characterized in that a horizontal synchronization signal is obtained when image information is formed on the top.

(Embodiment) FIG. 1 is a schematic diagram of a main part of an embodiment of an image forming apparatus of the present invention.

In the figure, l is a laser unit that emits a plurality of laser beams, and is made up of, for example, a single laser that emits a plurality of laser beams or a plurality of lasers. 2 is a drive circuit which outputs a plurality of laser beams modulated from the laser mountain unit 1 based on image information mtm. Reference numeral 3 denotes a light scanning means, which is rotated at a constant speed by a drive section (not shown) and reflects a plurality of laser beams from the laser unit 1 in the direction of the photoreceptor 4.

Reference numeral 4 denotes a photoreceptor, which is shaped like a drum or a belt, and a photosensitive layer for forming an image is provided on the surface of the photoreceptor. Reference numeral 5 denotes a light detection section, which is disposed near the a-light body 4 and outside the scanning direction N, and receives the scanning light flux from the optical scanning means 3. A slit member 6 has a narrow slit opening and is disposed in front of the photodetector 5. 7 is a synchronization signal circuit, which obtains a horizontal synchronization signal from the output signal from the photodetector 5 and sends the horizontal synchronization signal to the drive circuit 2.
It is being sent to 8 is an image output circuit, which sends a signal based on image information to the drive circuit.

In this embodiment, based on the signal from the image output circuit 8, the driving circuit 2 causes the laser unit 1 to emit a plurality of laser beams modulated based on image information, for example, two laser beams.

A plurality of light beams from the laser unit 1 are reflected by the optical scanning means 3 and guided onto the surface of the photoreceptor 4, where they are simultaneously scanned. At this time, image information is formed on the photoreceptor 411i by rotating the photoreceptor 4 in the sub-scanning direction together with the rotation of the optical scanning means 3. Then, a desired image is obtained from the image information formed on one surface of the photoreceptor through the processes of development, transfer, and separation in the same manner as in a normal image forming apparatus.

2(A) and 2(B) show the scanning state of the laser beams that scan the surface of the photoreceptor 4 in FIG. So 2
FIG. 2 is a schematic diagram when receiving two laser beams and obtaining a horizontal synchronization signal.

In this embodiment, two laser beams L"1 and L2 are transferred to the photoreceptor 4.
Scanning is performed with the two laser beams being shifted by a distance in the main scanning direction (horizontal scanning direction) on the surface, and with the beam diameter C (spot diameter) S of the two laser beams being smaller than the distance lsb.

Incidentally, since the slit member 6 is disposed near the photoreceptor 4, the following description will be made assuming that it is located at the same position as the photoreceptor 4iii for convenience.

That is, it is assumed that two light beams Ll and L2 are incident on the surface of the slit part 46 while being shifted by a distance fib in the main scanning direction. At this time, the pitch of the scanning lines in the sub-scanning direction is C.

Here, the width of the slit opening 6a of the slit member 6 in the main scanning direction is a, and the width a becomes a(b) when separated by a distance.As a result, the two laser beams L1 and L2 are directed to the slit opening. The two laser beams L1 and L2 are detected in time series by one photodetector 5 such that they pass through the laser beam 6a after a certain period of time has elapsed from each other.

That is, in this embodiment, the main scanning direction of the laser beam is set to
distance b) by using a slit member 6 having a predetermined opening (width a), one photodetector can detect two
The two laser beams are detected independently in time series to obtain horizontal synchronization signals for the two laser beams.

In this embodiment, there are three laser beams LL.

When detecting L2 and L3 with one photodetector, the laser beam L1. The configuration may be such that L2, L3 and the slit opening 6a of the slit member 6 are located, and the same applies to the case where there are four or more.

Further, when the scanning positions of a plurality of laser beams on the photoreceptor surface in the main scanning direction are the same, the slit member 6 is moved to the laser beam Ll as shown in FIG.

L2 and L3 are arranged at an angle (with respect to the sub-scanning direction), and the laser beam L1. L2. The configuration may be such that L3 is incident on the slit opening 6a of the slit member 6 in time series.

In this embodiment, in order to obtain horizontal synchronization signals for a plurality of laser beams, a slit member 6 and a photodetector 5 as shown in FIG.
Horizontal synchronization signals for a plurality of laser beams may be obtained by using a plurality of photodetecting means.

Furthermore, in this embodiment, by arranging a condenser lens behind the slit member or in front of the photodetector, the laser beam passing through the slit opening can be efficiently guided to the photodetector.

As shown in the other part 5, two slit members 51.5
2 in the optical axis direction, it is possible to prevent light beams other than the target laser beam beam, for example, light beams entering the slit member 51 from an oblique direction, from entering the photodetector 5, resulting in high accuracy. This is preferable because it allows for accurate detection.

In this embodiment, the slit member may be made monolithically when producing the photodetector element, which simplifies the structure.

(Effects of the Invention) According to the present invention, when a plurality of laser beams modulated based on image information are guided onto the photoreceptor surface via an optical scanning means and image information is formed on the photoreceptor surface, n An image type r#, which can obtain horizontal synchronizing signals for several laser beams with high precision with a simple configuration, for example, by one photodetector, and can easily form good image information on the surface of the photoreceptor. equipment can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the main parts of one embodiment of the present invention, and FIG.
The figure is an explanatory view of scanning by a plurality of laser beams on the surface of a photoreceptor and a photodetection method, and FIGS. 3, 4, and 5 are explanatory views of another embodiment of the photodetection means according to the present invention. In the figure, l is a laser unit, 2 is a drive circuit, 3 is a scanning means, 4 is a photoreceptor, 5 is a photodetector, 6 is a slit member, 7
The synchronizing signal circuit 58 is an image output circuit, and 51 and 52 are slit members.

Claims (1)

[Claims] (1) When a plurality of laser beams modulated based on image information are guided onto the photoreceptor surface via an optical scanning means and scanned on the photoreceptor surface to form image information, a predetermined portion of the photoreceptor surface is scanned. Horizontal synchronization when image information is formed on the surface of the photoreceptor by sequentially detecting the incident positions of the plurality of laser beams incident on the photoreceptor surface in time series using a photodetector through a slit member having an aperture of a predetermined shape. An image forming apparatus characterized in that it obtains a signal.