Optics: measuring and testing – By monitoring of webs or thread – For flaws or imperfections
Reexamination Certificate
2000-01-19
2003-01-28
Rosenberger, Richard A. (Department: 2877)
Optics: measuring and testing
By monitoring of webs or thread
For flaws or imperfections
C356S615000
Reexamination Certificate
active
06512585
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a laser scanning position detecting device for detecting the scanning position of a scanning laser beam supplied from a laser unit, which is used in a laser printer to expose an electrostatic latent image forming member such as a photosensitive material drum of a photosensitive material belt.
2. Description of the Related Art
A laser printer of tandem type has been known. In this type of laser printer, exposure optical systems (laser units) corresponding to four printing colors, i.e., yellow (Y), magenta (M), cyan (C), and black (Bk), are disposed in parallel to the rotation direction of the photosensitive material belt having an electrostatic latent image formed thereon. By operating these exposure optical systems in synchronism with the rotating movement of the photosensitive material belt, an image (an electrostatic latent image) is formed on the photosensitive material.
FIG. 1
is a schematic configuration diagram showing an image forming section of a conventional laser printer of tandem type having a photosensitive material belt and four laser units. In the printer shown in
FIG. 1
, however, illustration of a developer is omitted.
The laser printer of tandem type shown in
FIG. 1
includes a photosensitive material belt
1501
formed of a belt-shaped photosensitive material on which an electrostatic latent image is formed, and four laser units corresponding to four printing colors (a laser unit
1502
for the Y color, a laser unit
1503
for the M color, a laser unit
1504
for the C color, and a laser unit
1505
for the Bk color). Four laser units are disposed in a line along a rotation direction of the photosensitive material belt
1501
.
The photosensitive material belt
1501
is wound around a drive roller
1507
and a steering roller
1508
. The photosensitive material belt
1501
is adapted to be rotated when rotating drive force of a motor
1506
is transmitted to the drive roller
1507
via a transmission system such as gears which are not illustrated. The steering roller
1500
is provided to prevent the photosensitive material belt
1501
from meandering. As a result, the equilibrium state of the photosensitive material belt
1501
is maintained.
In the tandem-type printer having such a configuration, mounting precision of the laser units for forming respective colors is important. In the tandem-type printer, therefore, an L-shaped installation positioning plate
1509
is provided as a means for mounting the laser units for respective colors with high precision. Hereafter, an alignment process of laser units using an installation positioning plate
1509
will be described.
Typically, in each laser unit, there is an SOS (Start of Scan) sensor which serves as an image writing start reference and which is not illustrated. By taking a signal output of this SOS sensor as a reference, image forming timing is derived. The SOS sensors in respective laser units are adjusted so as to have the same image forming timing at predetermined installation positions of the respective laser units. When the laser units for respective colors are fixed on the same installation positioning plate
1509
, therefore, positions of respective laser units are adjusted by using an adjustment mechanism while measuring the intervals between the laser units in the installation positioning plate
1509
side and the intervals between the laser units in a side opposite to the installation positioning plate
1509
. As a result, the mounting precision of respective laser units is ensured, and alignment of respective laser units is conducted.
However, the laser units can be aligned by using the above described means only in the case where the laser units are disposed so as to be parallel to each other as in the printer shown in FIG.
1
.
As shown in
FIG. 2
, however, in the case where it is necessary to swell an exposed surface of a photosensitive material belt
1601
in an arch form from restrictions concerning the reduction in apparatus size and the configuration of a developer, the laser units
1602
cannot be mounted so as to become parallel to each other. In this case, it is difficult to accurately measure the mounting error between the laser units as described above. Even when the mounting error can be measured, differing mounting angles of the laser units cause different positions of laser beam scan lines of the laser units
1602
with respect to the vertical direction, due to the relation of bearing structures supporting polygon mirrors
1602
a
respectively included in the laser units
1602
. With respect to the installation positioning plate of the laser units, therefore, the scan lines are not in the same position (height).
Furthermore, even in the case where the laser units are arranged so as to become parallel to each other, the laser beam emitting faces of respective laser units need to be inclined uniformly by an angle of approximately 5 degrees with respect to the surface of the photosensitive material belt in order to prevent laser beams reflected by the surface of the photosensitive material from returning to the laser units. Also because of necessity of providing this inclination, it becomes difficult to keep the positioning precision.
Due to these facts, it is necessary to be able to detect where the scan line actually scanned on the photosensitive material passes through. Heretofore, however, there has not been a sensor capable of detecting the scanning position of laser beam which is scanning at high speed. Therefore, there has been used a technique of forming a test pattern for detecting a position deviation value of the scan line on the photosensitive material, transferring the test pattern on paper, reading the position deviation value of the scan line from an image obtained on the paper, and adjusting the positions of the laser units.
In the case where the above described technique is used as the method for detecting the mounting states of the laser units, all image forming processes must be incorporated in the near perfect state. It is necessary to derive the position deviation value occurring at this time, as a numerical value, from the image transferred onto paper. Furthermore, since the contrast of the color Y is low, it is difficult to automate reading the position deviation value of the scan line for each color by taking the color Y as the reference. It is necessary for a person to judge the line center of the drawn test pattern by watching and read the distance between the centers as a numerical value of the position deviation value. A great deal of labor is required for the position adjustment of each laser unit.
In Japanese Patent Application Laid-open No. 5-119572, a color image forming apparatus having a photo sensor separated from a laser unit is disclosed. The photo sensor is installed at one edge of a photosensitive belt and is used to sense a laser scanning beam at the one edge to produce a image write timing signal.
In Japanese Patent Application Laid-open No. 4-163515, a laser beam printer is provided with a light-receiving portion having a light-gathering lens for gathering an incident laser beam to produce a beam spot on a photo sensor for a predetermined time period. The output of the photo sensor is used to obtain a image write timing.
However, these devices disclosed in Japanese Patent Application Laid-open Nos. 5-119572 and 4-163515 are directed to detection of the write timing when forming an image. Therefore, they cannot provide detection of the scanning position of a laser beam for adjustment of installation position of a laser unit.
SUMMARY OF THE INVENTION
In view of the foregoing description, an object of the present invention is to provide a laser scanning position detecting device which allows detection of the scanning position of a laser beam scanning at high speed.
Another object of the present invention is to provide a laser scanning position detecting apparatus which allows a laser unit to accurately place at a predetermined position.
Still another obj
Dickstein Shapiro Morin & Oshinsky LLP.
Murata Manufacturing Co. Ltd
Rosenberger Richard A.
LandOfFree
Laser scanning position detecting device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Laser scanning position detecting device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Laser scanning position detecting device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3068084