JPH04306679A - Light signal generator - Google Patents

Abstract

PURPOSE:To carry out stable control for quantity of light by making a part of optical fiber forked from an optical fiber array for monitoring quantity of light, and by detecting the quantity of light ejected from the end of the optical fiber so that the quantity of light is fed back to a quantity of light control means. CONSTITUTION:Part of optical fiber bundled by a light taking part 21 is forked from an optical fiber array 20 as an optical fiber 20a for monitoring quantity of light. The end of the optical fiber 20a is opposed to the light receiving part of a photosensor 45. The photosensor 45 is irradiated by the part of the light emitted from a light source 10 through the forked fiber 20a for monitoring, and the quantity of light is detected by the photosensor 45. The quantity of light detection output by the photosensor 45 is amplified by a current amplification device 48, and is input into a quantity of light controller 49. Namely, the quantity of light of the light source 10 is varied, the variation is detected by the photosensor 45, and the detection value is fed back to the quantity of light controller 49, and the voltage applied to the light source 10 is thus adjusted.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical signal generating apparatus, and more particularly to an optical signal generating apparatus used in an image writing head of an image forming apparatus such as a printer or facsimile.

0002

[Prior Art] Conventionally, an optical signal generating device used as a head for writing an image on a photoreceptor converts light from a light source such as a halogen lamp into a straight line (main scanning direction) through an optical fiber array. It is known that light emitted from an optical fiber array is turned on and off based on an image signal by an optical shutter array made of PLZT, and an image is formed on a photoreceptor via a lens array.

In such an optical signal generating device, it is necessary to stabilize the amount of light emitted from the light source in order to stably obtain image density. To this end, conventionally, a photo sensor for monitoring the amount of light has been provided in a case surrounding the light source, and the detected value of the amount of light has been fed back to the light amount control device of the light source. However, this monitoring mechanism has a problem in that since the photosensor is located close to the light source, the sensitivity characteristics of the photosensor change due to the heat generated by the light source, and accurate control of the amount of light cannot be expected. Moreover, when the photosensor is attached to the case of the light source, it is difficult to sufficiently shield the photosensor from light, and in this respect, it is also difficult to accurately detect the amount of light emitted from the light source.

0004

[Object, structure, and operation of the invention] Therefore, the object of the present invention is to
To provide an optical signal generating device in which a light amount detection means can accurately detect the amount of light emitted from a light source without being affected by heat generation of the light source, and furthermore, can control the amount of light emitted from the light source in a stable state. In order to achieve the above object, the optical signal generator according to the present invention branches a part of the optical fibers bundled in the lighting section from the optical fiber array, and outputs the light from the tip of the branched monitoring optical fiber. The amount of light is detected by a light amount detection means. A photosensor is usually used as the light amount detection means, and it is installed at a location away from the light source, so there is no possibility that the sensitivity characteristics will change due to thermal effects from the light source. The detection value of the light amount detection means is fed back to the light amount control means, and the light source is controlled so that the amount of emitted light is always constant.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of an optical signal generator according to the present invention will be described with reference to the accompanying drawings. The optical signal generator is shown in Figure 1.
As shown in its schematic configuration, a light source 10, an optical fiber array 20, a rod lens 25, an optical shutter array 30,
It consists of a lens array 40 for imaging and a light amount control device 49, and is further provided with a photosensor 45 for monitoring the amount of light and a current amplification device 48 for amplifying its output.

The light source 10 is made of a halogen lamp, has a reflecting mirror 11 made of a dichroic mirror, and has a case 1.
It is stored in 2. The optical fiber array 20 is made up of a large number of optical fibers, one end of which is tied together and fixed to the case 12 as a lighting section 21, facing the light source 10. Also,
The other end of the optical fiber array 20 is lined up in the main scanning direction (indicated by arrow X) and serves as an output section 22 . Lighting section 21
The light guided to is emitted from the emitting section 22 in a straight line along the main scanning direction X. The optical shutter array 30 has optical shutter elements made of PLZT and their driving circuit arranged in a straight line on a glass substrate, and polarizers 35,
36 (polarizer 35, analyzer 36) are installed. The lens array 40 is composed of a large number of converging rod lenses, and forms an image of light onto the photoreceptor drum 50.

In the above configuration, the light emitted from the light source 10 is collected by the reflecting mirror 11, and the light emitted from the light source 10 is collected by the optical fiber array 20.
The light is guided to the lighting section 21, and is emitted in a straight line from the emission section 22. This light irradiates the optical shutter array 30 via the rod lens 25 and polarizer 35. The voltage of each optical shutter element is turned on and off based on the image signal, and the voltage (
Only the light that has passed through the element to which the half-wave voltage (half-wave voltage) was applied passes through the polarizer 36. The light that has passed through the polarizer 36 forms an image on the photosensitive drum 50 via the lens array 40 . The photosensitive drum 50 is rotated at a constant speed in the direction of arrow a, and a predetermined image is formed as an electrostatic latent image on its surface.

By the way, from the optical fiber array 20, a part of the optical fibers bundled in the lighting section 21 is branched off as an optical fiber 20a for monitoring the amount of light. The tip of this monitoring optical fiber 20a is connected to the photosensor 4.
The photosensor 4 is introduced into a case 46 containing the photo sensor 4.
It faces the light receiving section No. 5. Therefore, a portion of the light emitted from the light source 10 illuminates the photosensor 45 via the monitoring branch fiber 20a, and the amount of light is detected by the photosensor 45. The light amount detection output from the photosensor 45 is amplified by the current amplification device 48, and the light amount detection output is output from the light amount control device 4.
9. The light amount control device 49 includes a lamp power supply circuit (not shown) and is used to control the voltage value applied to the light source 10. That is, when the light amount of the light source 10 changes for some reason, the change is detected by the photosensor 45, the detected value is fed back to the light amount control device 49, and by adjusting the voltage applied to the light source 10, the light source 10 is changed. The amount of emitted light is always maintained constant.

In the light amount monitoring mechanism described above, since the monitoring branch fiber 20a is branched from the array 20, the photosensor 45 can be placed in a place where it is not affected by the heat of the light source 10, and the photosensor 45 can be stabilized. It can be used under certain sensitivity characteristics, and the amount of light can be accurately monitored. Furthermore, the location of the photosensor 45 can be freely selected, and the photosensor 45 can be easily shielded from light by the case 46 alone.

The optical signal generator according to the present invention is not limited to the above-mentioned embodiments, but can be modified in various ways within the scope of the invention. In particular, the light source 10 and the optical shutter array 3
The configuration of 0 or the configuration around them can be changed arbitrarily.

[0011]

As is clear from the above description, according to the present invention, a part of the optical fiber is branched from the optical fiber array for use in monitoring the amount of light, and the amount of light emitted from the tip is detected by the light amount detection means. Since the light amount is fed back to the light amount control means of the light source, the light amount detection means can be placed at any location where it is not affected by the heat of the light source. As a result, the sensitivity characteristics of the light amount detection means are stabilized, and the light source can be controlled to a constant light amount at all times.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an optical signal generating device according to the present invention.

[Explanation of symbols]

1...Light source 20...Optical fiber array 20a...Branch optical fiber 30...Optical shutter array 40...Imaging lens array 45... Photo sensor (light amount detection means) 49...Light amount control means

Claims (1)

[Claims] 1. A light source, an optical fiber array that converts light from the light source into a linear shape, an optical shutter array that turns on and off the light emitted from the optical fiber array, and an imaging lens array. In the optical signal generating device configured, a branch optical fiber for monitoring is obtained by branching a part of the optical fibers bundled from the optical fiber array into a lighting section, and a light quantity for detecting the quantity of light emitted from the branched optical fiber. An optical signal generating device comprising: a detection means; and a control means for controlling the amount of light emitted from the light source based on a detection value of the light amount detection means.