Incremental printing of symbolic information – Light or beam marking apparatus or processes – Scan of light
Reexamination Certificate
1998-09-24
2001-08-21
Le, N. (Department: 2861)
Incremental printing of symbolic information
Light or beam marking apparatus or processes
Scan of light
C347S256000
Reexamination Certificate
active
06278474
ABSTRACT:
This application is based on application No. 9-262307 filed in Japan, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus which forms an image (electrostatic latent image) on a photographic recording medium such as photosensitive material, photosensitive member, or the like by using an optical write head having a light shutter array made of PLZT or a LED array.
2. Description of Related Art
Conventionally, various kinds of optical write heads which turn on and off light for each pixel with use of a light shutter array made of PLZT or an LED array have been used to form images (electrostatic latent images) on a silver-salt print sheet or film or an electrophotographic photosensitive member. Also, in order to realize an image forming at high speed, an image forming apparatus which has three optical write heads has been disclosed (refer to U.S. Pat. No. 5,488,450).
In the image forming apparatus with three optical write heads, a tandem method is adopted; which is, with three optical write heads arranged in row in the sub scanning direction, an image is composed and recorded on a recording medium being carried flat by exposing one by one with specified time lag. However, the apparatus of tandem method has problems: it is difficult to carry the recording meidum flat at high accuracy; and, an extra control is needed in order to synchronize three exposure positions, and operation of the control is complicated.
On the other hand, an optical write head, in order to form high-quality images without unevenness, needs to be subjected to measurement of the quantity of light outputted from each element and to correction in quantity of light according to the measurement result. Conventionally, an optical write head is fitted in a jig before it is built in an image forming apparatus, and the quantity of light outputted from each element is measured by a light-quantity measuring device with a photosensor; then, correction date are produced based on the result of the measurement. However, those correction data are effective only in the early time of building the optical write head in an apparatus, and are not useful when the output characteristic of each light element changes because of aging and/or a change in environmental conditions. That is, a real-time light-quantity correction for three optical write heads has not been achieved in the present condition.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an image forming apparatus which is capable of composing and recording an image at high accuracy on an image receiving member with use of a plurality of light signal emitting heads.
Another object of the present invention is to provide an image forming apparatus which is capable of measuring the quantity of light outputted from a plurality of light signal emitting heads as necessary and producing correction data at real time so as to produce high-quality images constantly.
In order to attain the objects above, an image forming apparatus in accordance with the present invention comprises: a plurality of light signal emitting heads which control turn-on and -off of a plurality of optical elements extending in a main scanning direction individually responsive to an image data; an optical path changing member which leads light emergent from the light signal emitting heads to align on a substantially same line; and a guiding member which guides on its arced curving section an image receiving member which moves in a sub scanning direction on an image focusing position of the light guided by the optical path changing member.
According to the present invention, the image receiving member, with being adhered to the curving section of the guiding member, is guided to move in the sub scanning direction at the exposure position; thus, the receiving position of the image receiving member is accurately located. Moreover, since light emergent from a plurality of light signal emitting heads are led to align on the substantially same line by the optical path changing member, image composing position is also accurately located; thus high-quality image can be realized at high accuracy.
In accordance with the present invention, it is preferable that the exposure position is adjustable responding to the thickness of the image receiving member. For that purpose, it is proper to provide a means for adjusting the exposure position which displaces either the guiding member or the light signal emitting head.
Further, the image forming apparatus in accordance with the present invention has a holder for holding the guiding member wherein the guiding member can move toward or away from the exposure position. By moving away the guiding member from the exposure position, the image receiving member can be set easily. Also, by further providing a positioning member for touching and stopping the guiding member through the image receiving member when the guiding member is set on the exposure position, the image receiving member is accurately set on the exposure position corresponding to the thickness thereof.
Furthermore, the image forming apparatus in accordance with the present invention comprises a light-quantity measuring unit which moves a light-receiving element for receiving light emergent from each of the light signal emitting heads in the main scanning direction when the guiding member is set aside from the exposure position. The light-quantity measuring unit, as moving in the main scanning direction, measures the light quantity outputted from each optical element of the light signal emitting head, and simultaneously produces light-quantity correction data which will be fed back when image-forming. In the image forming apparatus, since the light-quantity measuring unit is built in the apparatus, it is possible to measure light quantity at desired time and renew the correction data; thus, it can properly cope with a change in output characteristic of the optical elements because of aging and/or a change in environmental conditions.
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Matsubara Ken
Saito Itaru
Wada Kenichi
Le N.
McDermott & Will & Emery
Minolta Co. , Ltd.
Pham Hai C.
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