Incremental printing of symbolic information – Light or beam marking apparatus or processes – Scan of light
Reexamination Certificate
2000-02-02
2002-01-08
Pham, Hai C. (Department: 2881)
Incremental printing of symbolic information
Light or beam marking apparatus or processes
Scan of light
C347S246000, C347S136000
Reexamination Certificate
active
06337706
ABSTRACT:
This application is based on an application No. 11-29308 filed in Japan, the contents of which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to a solid scanning optical writing device to write images using a PLZT light shutter array or LED array, light amount correction method therefor and light amount measuring device.
2. Description of the Related Art
Various optical writing devices have conventionally been provided that form images on photographic paper or film using a silver halide material, or on an electrophotographic photoreceptor, by controlling the light for each pixel using a light shutter array or LED array comprising PLZT or other elements. In such an optical writing device, line noise may occur in the output image due to a variation in the amount of light passing through or emitted from the optical elements of the light shutter array or LED array. In order to eliminate this noise, the light amount output from each optical element is measured, correction calculation is performed based on the measurement results, and correction of the light amount variation (shading correction) is performed.
In measuring the light amount, it is preferable from the standpoint of ensuring measurement accuracy and making the measuring device small in size that the light amount from each optical element of the light shutter array, etc., be directly measured. However, it is not easy to accurately measure the light amount from each of the optical elements, which have an extremely dense arrangement in order to form high resolution images, and correlate the measurement results to each optical element.
FIGS. 8 and 9
show how light amount measurement is conventionally performed. They show how the amount of light that passes through each light shutter
31
(optical element) of the PLZT light shutter array is measured by means of a measuring device. The multiple light shutters
31
are aligned in two lines. A light shutter
31
of one line is located between two light shutters
31
of the other line. When voltage is impressed, the light shutter
31
causes the plane of polarization of the light that entered it from behind to rotate, allows the light to pass through and outputs it from the front. When voltage is not impressed, the plane of polarization of the light that enters the light shutter
31
from behind does not rotate and the light is output from the front just as it struck the light shutter.
91
indicates a light receiving mask located in front of the sensor that receives the light from the light shutters
31
. In
FIG. 8
, the light receiving mask
91
has a slit
91
a
with the same configuration as the light shutter
31
, and regulates the light that strikes the sensor. The light receiving mask
92
shown in
FIG. 9
has a slit
92
a
, the length of which that runs along the secondary scanning direction perpendicular to the length of the lines of the light shutter is equal to the length of the light shutter
31
. When the amount of light passing through the light shutter
31
is measured using such a mask
91
or
92
, the light amount output from each light shutter
31
may be accurately measured.
However, when a light shutter array is actually used as an optical writing device, from the standpoint of efficiency of use of the light, and to ensure that the necessary distance from the exposure surface is maintained, an image forming lens (selfoc lens array) is often used together with the light shutter array.
FIG. 10
is a view of the positional relationship between a selfoc lens array and the light shutters
31
of a PLZT light shutter array. Ordinarily, due to the effect of the selfoc lens array on the image forming resolution (hereinafter ‘MTF’), the output light from the light shutters
31
is slightly blurred when it forms an image on the exposure surface.
Because a selfoc lens array comprises multiple rod lenses
35
a
aligned in a zigzag fashion, as shown in
FIG. 10
, the MTF varies depending on the positional relationship between the light shutters
31
and the rod lenses
35
a
. In other words, the image formed on the exposure surface by the output light from the light shutters
31
may be sharp or blurry depending on the area. Where light is output from both lines of the light shutters
31
, the light amount from the gap between light shutters
31
(trough light amount) does not become completely zero. As explained above, where the light shutters
31
are aligned in a zigzag fashion such that they form two lines, exposure is performed by means of the light from a particular light shutter
31
, to which some of the light from the neighboring light shutters
31
located in the other line is added.
In addition, in the manufacturing process by which the light shutters
31
are aligned in a zigzag fashion such that they form two lines, a groove
32
(see
FIGS. 8 and 9
) is formed between any two light shutters
31
, and a slight amount of light escapes of this groove
32
. This escaping light affects the actual exposure as well.
Due to the details explained above, correcting the variation in light amount among the optical elements simply based on the information on the light amount measured using the mask
91
or
92
shown in
FIG. 8
or
9
is insufficient to correct the variation in light amount on the exposure surface where an image is actually formed, and a variation in light amount still occurs on the exposure surface.
OBJECTS AND SUMMARY
The object of the present invention is to provide an improved solid scanning optical writing device, light amount correction method therefor and light amount measuring device.
Another object of the present invention is to provide a solid scanning optical writing device, light amount correction method therefor and light amount measuring device that are capable of accurately measuring the output light amount of each optical element and performing good light amount correction.
Yet another object of the present invention is to provide a solid scanning optical writing device, light amount correction method therefor and light amount measuring device in which the variation in light amount among the optical elements is corrected on the exposure surface where an image is formed.
In order to attain these and other objects, one aspect of the present invention comprises a solid scanning optical writing device that, based on the image data, turns ON/OFF the multiple optical elements that are aligned in a zigzag fashion such that they form two lines in the main scanning directions, said optical writing device having a light amount measuring unit including a light amount sensor to measure the amount of light output from the optical elements, wherein the light receiving area of the light amount sensor has an open slit and the length of the opening of the slit in the secondary scanning direction is set to be as long as or longer than the length of the optical element in the secondary scanning direction.
Another aspect of the present invention comprises a light amount measuring device having a light amount measuring unit including a light amount sensor to measure the amount of light output from the multiple optical elements aligned in a zigzag fashion such that they form two lines, a means to move the light amount measuring unit forward and backward in the direction of the alignment of the optical elements, and a means to adjust the position of the light amount measuring unit, wherein the light receiving area of the light amount sensor of the light amount measuring unit has an open slit and the length of the opening of the slit in the direction perpendicular to the direction of the alignment of the optical elements is set to be as long as or longer than the length of the optical element.
Yet another aspect of the present invention comprises a light amount correction method for the solid scanning optical writing device, wherein this method turns ON/OFF the multiple optical elements aligned in a zigzag fashion such that they form two lines in the main scanning directions based
Minolta Co. , Ltd.
Pham Hai C.
Sidley Austin Brown & Wood
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