U.S. patent application number 09/271455 was filed with the patent office on 2002-03-21 for scanner having a light beam incident position adjusting device.
Invention is credited to HIRANO, MASAKAZU, MORITA, TAKASHI.
Application Number | 20020033988 09/271455 |
Document ID | / |
Family ID | 14062424 |
Filed Date | 2002-03-21 |
United States Patent
Application |
20020033988 |
Kind Code |
A1 |
MORITA, TAKASHI ; et
al. |
March 21, 2002 |
SCANNER HAVING A LIGHT BEAM INCIDENT POSITION ADJUSTING DEVICE
Abstract
A scanner includes a light-beam emitter for emitting a light
beam; a light-beam deflector for deflecting the light beam to scan
a scanning surface; a photo-detector provided at a position outside
an image-forming scanning range of the scanning surface to detect a
scanning light beam before the scanning light beam starts
generating a scanning line in the image-forming scanning range; a
rotatable member, located in front of an incident surface of the
photo-detector, that is rotatable about a rotational axis
perpendicular to a plane defined by the scanning light beam by the
deflector; an optical member, provided on the rotatable member,
that allows the scanning light beam to pass therethrough to be
incident upon the incident surface of the photo-detector; and a
device for adjusting rotational position of the rotatable member
about the rotational axis.
Inventors: |
MORITA, TAKASHI; (SAITAMA,
JP) ; HIRANO, MASAKAZU; (TOKYO, JP) |
Correspondence
Address: |
GREENBLUM & BERNSTEIN, P.L.C.
1941 ROLAND CLARKE PLACE
RESTON
VA
20191
US
|
Family ID: |
14062424 |
Appl. No.: |
09/271455 |
Filed: |
March 18, 1999 |
Current U.S.
Class: |
359/209.1 |
Current CPC
Class: |
G02B 26/122 20130101;
G02B 26/127 20130101 |
Class at
Publication: |
359/196 |
International
Class: |
G02B 026/08 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 19, 1998 |
JP |
10-092725(P) |
Claims
What is claimed is:
1. A scanner comprising: a light-beam emitter for emitting a light
beam; a light-beam deflector for deflecting said light beam to scan
a scanning surface; a photo-detector provided at a position outside
an image-forming scanning range of said scanning surface to detect
a scanning light beam before said scanning light beam starts
generating a scanning line in said image-forming scanning range; a
rotatable member located in front of an incident surface of said
photo-detector, said rotatable member being rotatable about a
rotational axis perpendicular to a plane defined by said scanning
light beam by said deflector; an optical member that is provided on
said rotatable member, said optical member allowing said scanning
light beam to pass therethrough to be incident upon said incident
surface of said photo-detector; and a device for adjusting
rotational position of said rotatable member about said rotational
axis.
2. The scanner according to claim 1, wherein said light-beam
deflector comprises a polygon mirror.
3. The scanner according to claim 1, wherein a signal, output from
said photo-detector, is used for detecting the timing for
commencement of writing said scanning line with respect to said
scanning surface.
4. The scanner according to claim 1, wherein said optical member
comprises a cylindrical lens.
5. The scanner according to claim 1, wherein said optical member
comprises a plane-parallel plate.
6. The scanner according to claim 1, wherein said optical member
comprises a member having an optical axis which lies in said plane
defined by said scanning light beam and wherein said rotational
axis extends perpendicular to said optical axis.
7. The scanner according to claim 1, wherein said rotatable member
is positioned in a recess formed in a housing to be rotatable about
said rotational axis.
8. The scanner according to claim 7, wherein said recess is a
circular recess, and wherein said rotatable member comprises a disc
portion which is fitted into said circular recess to be rotatable
about said rotational axis.
9. The scanner according to claim 7, wherein said rotatable member
comprises a shaft coaxial to said rotational axis, and wherein said
rotatable member is positioned in said recess with said shaft being
inserted into a hole formed at the bottom of said recess so that
said rotatable member is rotatable about said shaft.
10. The scanner according to claim 7, wherein said recess is formed
on an outer surface of said housing, and wherein a through hole
through which said optical member is inserted in said housing is
formed at the bottom of said recess, and wherein said rotatable
member is positioned in said recess with said optical member being
inserted into said housing through said through hole.
11. The scanner according to claim 7, wherein said adjusting device
comprises at least one set screw which penetrates into said
rotatable member through a slot formed thereon to be screwed into
said housing.
12. The scanner according to claim 7, wherein said adjusting device
comprises a member, fixed to said housing, for pressing said
rotatable member against the bottom of said recess.
13. The scanner according to claim 12, wherein said pressing member
comprises a spring.
14. The scanner according to claim 13, wherein said spring
comprises a leaf spring fixed to said housing by at least one set
screw.
15. The scanner according to claim 1, further comprising a device
for rotating said rotatable member about said rotational axis.
16. The scanner according to claim 15, wherein said rotating device
comprises: a radial slot formed on said rotatable member to extend
in a radial direction thereof; and a rotating tool engageable with
said rotatable member to rotate said rotatable member about said
rotational axis, wherein said tool comprises an engaging pin
engageable with said radial slot, an axis of said engaging pin
deviating from a rotational axis of said rotating tool.
17. The scanner according to claim 15, wherein said rotating device
comprises: a circumferential gear formed on an outer peripheral
surface of said rotatable member; and a rotating tool engageable
with said rotatable member to rotate said rotatable member about
said rotational axis, said rotating tool comprising a pinon gear
which is engaged with said circumferential gear.
18. The scanner according to claim 1, wherein said scanning surface
is a photoconductive surface of a photoconductive drum.
19. The scanner according to claim 1, wherein said photo-detector
and said light-beam emitter are supported on a common circuit
substrate and do not relatively move.
20. The scanner according to claim 1, further comprising an
f.theta. reflecting lens that reflects said scanning light beam
deflected by said light-beam deflector to said scanning
surface.
21. A scanner comprising: a light-beam emitter for emitting a light
beam; a light-beam deflector for deflecting said light beam to scan
a scanning surface; a photo-detector provided at a position outside
an image-forming scanning range of said scanning surface to detect
a scanning light beam before said scanning light beam starts
generating a scanning line, said photo-detector generating an
output signal upon detecting said scanning light beam to determine
a timing of commencement of writing said scanning line with respect
to said scanning surface; and an optical member for deflecting said
scanning light beam to be incident upon said photo-detector in a
direction to vary the timing of the scanning light beam incident
upon said photo-detector.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a scanner in which a light
beam is deflected to scan a scanning surface, and more specifically
to a scanner which is provided with a device for adjusting an
incident position of a light beam on a photo-detector used for
determining the timing of commencement of writing each scanning
line with respect to a scanning surface.
[0003] 2. Description of the Related Art
[0004] A laser-beam printer provided with a laser-beam scanner is
well known. In a laser-beam printer, a laser beam which is
modulated in accordance with image signals to be output from a
laser-beam emitter is deflected by a polygon mirror to scan a
photoconductive surface of a photoconductive drum in the main
scanning direction to thereby form a main scanning line in the
photoconductive surface. The laser emission is turned ON and OFF in
accordance with given image signals to draw a corresponding image
(charge-latent image) on the photoconductive surface of the drum,
and subsequently this image drawn on the photoconductive surface of
the drum is transferred to plain paper according to a conventional
electrophotographic method. Dry powder (e.g., toner) that adheres
only to the charged area is applied to the drum, transferred to the
plain paper and fused by heat. Such a laser-beam printer is widely
used; e.g., as an output device for a computer.
[0005] In a laser-beam scanner provided in such a laser-beam
printer, a photo-detector (i.e., a laser-beam detector) is
generally fixed at a position outside the latent-image-forming
scanning range to detect the scanning laser beam before it starts
generating each scanning line. The photo-detector generates a pulse
signal each time the scanning laser beam is incident on the
photo-detector. The pulse signals output from the photo-detector
are input to a processor, and subsequently the processor generates
corresponding horizontal synchronizing pulses (HSYNC) to determine
the timing of commencement of writing main scanning data, namely,
writing each main scanning line.
[0006] In such a laser-beam scanner, two types of devices for
adjusting the timing of commencement of writing each main scanning
line with respect to the photoconductive surface of the drum (i.e.,
for adjusting the timing of generating horizontal synchronizing
pulses) are known. In each type of adjusting device, a reflecting
mirror is arranged at a position outside the
latent-image-forming-scanning range to detect the scanning laser
beam before it starts generating each scanning line, while a
photo-detector is arranged at a position on the path of the laser
beam reflected by the reflecting mirror. In one type of adjusting
device, the reflecting mirror is rotatable so that the incident
position of the laser beam on the photo-detector can be adjusted,
which makes it possible to adjust the timing of generating
horizontal synchronizing pulses. In the other type of adjusting
device, the reflecting mirror is fixed while the photo-detector is
linearly movable so that the incident position of the laser beam on
the photo-detector can be adjusted.
[0007] In the former type of adjusting device, although the
incident position of the laser beam on the photo-detector can be
adjusted by rotating the reflecting mirror, it is difficult to
finely adjust the incident position of the laser beam on the
photo-detector. Furthermore, the reflective mirror needs to be
accurately and precisely positioned on a base on which the
reflective mirror is to be mounted. In the latter type of adjusting
device, the position at which the photo-detector is to be arranged
is quite limited. Moreover, in each type of adjusting device, in
the case where the base on which the reflective mirror and the
photo-detector are mounted is slightly deformed after a long period
of use, the respective positions of the reflective mirror and the
photo-detector deviate from their original positions. In this case,
the respective positions of the reflective mirror and the
photo-detector cannot be easily adjusted from outside the
laser-beam apparatus.
SUMMARY OF THE INVENTION
[0008] An object of the present invention is to provide a scanner
provided with a device for adjusting the incident position of a
light beam on a photo-detector used for determining the timing of
commencement of writing each scanning line with respect to a
scanning surface, wherein the adjusting device makes it possible to
finely and easily adjust the incident position of the light beam on
the photo-detector.
[0009] Another object of the present invention is to provide a
scanner having such an adjusting device which makes it possible to
finely and easily adjust the incident position even from outside
the scanner.
[0010] Other aspects, objects and advantages of the present
invention will become apparent to one skilled in the art from the
following disclosure and the appended claims.
[0011] According to an aspect of the present invention, there is
provided a scanner including a light-beam emitter for emitting a
light beam; a light-beam deflector for deflecting the light beam to
scan a scanning surface; a photo-detector provided at a position
outside an image-forming scanning range of the scanning surface to
detect a scanning light beam before the scanning light beam starts
generating a scanning line in the image-forming scanning range; a
rotatable member, located in front of an incident surface of the
photo-detector, that is rotatable about a rotational axis
perpendicular to a plane defined by the scanning light beam by the
deflector; an optical member, provided on the rotatable member,
that allows the scanning light beam to pass therethrough to be
incident upon the incident surface of the photo-detector; and a
device for adjusting rotational position of the rotatable member
about the rotational axis.
[0012] Preferably, the light-beam deflector includes a polygon
mirror.
[0013] Preferably, a signal, output from the photo-detector, is
used for detecting the timing for commencement of writing the
scanning line with respect to the scanning surface.
[0014] The optical member can include a cylindrical lens or a
plane-parallel plate. Preferably, the optical member includes a
member having an optical axis which lies in a plane defined by the
scanning light beam, and the rotational axis extends perpendicular
to the optical axis.
[0015] The rotatable member can be positioned in a recess formed in
a housing to be rotatable about the rotational axis.
[0016] In an embodiment, the recess is a circular recess, and the
rotatable member includes a disc portion which is fitted into the
circular recess to be rotatable about the rotational axis.
[0017] Alternatively, the rotatable member includes a shaft coaxial
to the rotational axis, and the rotatable member is positioned in
the recess with the shaft being inserted into a hole formed at the
bottom of the recess so that the rotatable member is rotatable
about the shaft.
[0018] Further, the recess can be formed on an outer surface of the
housing, and a through hole through which the optical member is
inserted in the housing is formed at the bottom of said recess, and
the rotatable member is positioned in the recess with the optical
member being inserted into the housing through the through
hole.
[0019] For holding the rotatable member at an adjusted position,
the adjusting device can include at least one set screw which
penetrates into the rotatable member through a slot formed thereon
to be screwed into the housing.
[0020] Alternatively, it is possible that the adjusting device
includes a member, fixed to the housing, for pressing the rotatable
member against the bottom of the recess. Preferably, the pressing
member includes a spring. Further, the spring can be a leaf spring
fixed to the housing by at least one set screw.
[0021] Preferably, the scanner further includes a device for
rotating the rotatable member about the rotational axis.
[0022] In an embodiment, the rotating device includes a radial slot
formed on the rotatable member to extend in a radial direction
thereof; and a rotating tool engageable with the rotatable member
to rotate the rotatable member about the rotational axis. Namely,
the tool includes an engaging pin engageable with the radial slot,
an axis of the engaging pin deviating from a rotational axis of the
rotating tool.
[0023] Alternatively, the rotating device includes a
circumferential gear formed on an outer peripheral surface of the
rotatable member; and a rotating tool engageable with the rotatable
member to rotate the rotatable member about the rotational axis.
Namely, the rotating tool includes a pinon gear which is engaged
with the circumferential gear.
[0024] It is preferable that the scanning surface is a
photoconductive surface of a photoconductive drum.
[0025] In an embodiment, the photo-detector and the light-beam
emitter are supported on a common circuit substrate and do not
relatively move.
[0026] The scanner can include an f.theta. reflecting lens that
reflects the scanning light beam deflected by the light-beam
deflector to the scanning surface.
[0027] According to another aspect of the present invention, there
is provided a scanner including a light-beam emitter for emitting a
light beam; a light-beam deflector for deflecting the light beam to
scan a scanning surface; a photo-detector provided at a position
outside an image-forming scanning range of the scanning surface to
detect a scanning light beam before the scanning light beam starts
generating a scanning line, the photo-detector generating an output
signal upon detecting the scanning light beam to determine a timing
of commencement of writing the scanning line with respect to the
scanning surface; and an optical member for deflecting the scanning
light beam to be incident on the photo-detector in a direction to
vary the timing of the scanning light beam incident upon the
photo-detector.
[0028] The present disclosure relates to subject matter contained
in Japanese Patent Application No. 10-92725 (filed on Mar. 19,
1998) which is expressly incorporated herein by reference in its
entirety.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] The present invention will be described below in detail with
reference to the accompanying drawings in which:
[0030] FIG. 1 is a perspective view of the scanning optical system
of a laser-beam scanner to which the present invention is
applied;
[0031] FIG. 2 is a perspective view of an embodiment of a device
for adjusting the rotational position of a cylindrical lens with
respect to a housing of the laser-beam scanner;
[0032] FIGS. 3A and 3B are explanatory views of the cylindrical
lens when rotated about a rotational axis;
[0033] FIG. 4 is a perspective view of the scanning optical system
of a laser-beam scanner in which a photo-detector and a light-beam
emitter are supported on a common circuit substrate;
[0034] FIG. 5 is an exploded perspective view of another embodiment
of the device for adjusting the rotational position of the
cylindrical lens;
[0035] FIG. 6 is a plan view of still another embodiment of the
device for adjusting the rotational position of the cylindrical
lens;
[0036] FIG. 7 is a plan view of yet another embodiment of the
device for adjusting the rotational position of the cylindrical
lens;
[0037] FIG. 8 is a plan view of yet another embodiment of the
device for adjusting the rotational position of the cylindrical
lens;
[0038] FIG. 9 is a plan view of yet another embodiment of the
device for adjusting the rotational position of the cylindrical
lens;
[0039] FIG. 10 is a perspective view of an embodiment of a device
for rotating the cylindrical lens; and
[0040] FIG. 11 is a perspective view of another embodiment of the
device for rotating the cylindrical lens.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0041] FIG. 1 shows the scanning optical system of a laser-beam
scanner to which the present invention is applied. The laser-beam
scanner scans the photoconductive surface of a photoconductive drum
1 (scanning surface). The laser beam scanner and the
photoconductive drum 1 are positioned within a laser-beam printer
as essential elements.
[0042] The scanning optical system of the laser-beam scanner is
provided with a laser diode (light-beam emitter) 2, a collimating
lens 4a, a cylindrical lens 4b, a reflecting mirror 6, a polygon
mirror (light-beam deflector) 8, an f.theta. reflecting lens 10, an
f.theta. lens 12, a reflecting mirror 14, a cylindrical lens
(optical member) 16, and a laser-beam detector (photo-detector) 18.
The collimating lens 4a and the cylindrical lens 4b together
constitute an optical system 4 for the laser diode 2.
[0043] The laser diode 2 outputs a laser beam L1 modulated in
accordance with image signals. The laser beam emitted from the
laser diode 2 is collimated through the collimating lens 4a.
Thereafter, this collimated laser beam is made incident upon the
cylindrical lens 4b positioned in front of the collimating lens 4a.
The cylindrical lens 4b has power in the sub-scanning direction, so
that the spot of the laser beam incident thereon is converged
therethrough in the sub-scanning direction to be incident upon the
reflecting mirror 6. The laser beam which is incident on the
reflecting mirror 6 is reflected thereby to be incident on the
polygon mirror 8. The polygon mirror 8 is driven to rotate at a
fast rotational speed by a motor (not shown), so that the laser
beam incident on the polygon mirror 8 is deflected in the main
scanning direction to be incident on the f.theta. reflecting lens
10.
[0044] The deflected laser beam L2 which is incident on the
f.theta. reflecting lens 10 to be reflected thereby proceeds to the
reflecting mirror 20 through the f.theta. lens 12, which is
arranged to face the f reflecting lens 10. Subsequently, the laser
beam incident upon the reflecting mirror 20 is reflected thereby
towards the photoconductive surface of the drum 1.
[0045] The polygon mirror 8 rotates in a counterclockwise direction
(shown by an arrow "A"), as viewed in FIG. 1. The reflecting mirror
14 is fixed at a position to receive the scanning laser beam
emitted from the polygon mirror 8 before the scanning laser beam is
incident on the f.theta. reflecting lens 10 at each scanning sweep
while the polygon mirror 8 rotates. The laser beam L3 reflected by
the reflecting mirror 14 is incident on the laser-beam detector 18
through the cylindrical lens 16. The laser-beam detector 18 is
fixed at a position facing to the reflecting mirror 14 with the
cylindrical lens 16 being positioned between the reflecting mirror
14 and the laser-beam detector 18. Namely, the cylindrical lens 16
is located in front of an incident surface of the laser-beam
detector 18.
[0046] The laser-beam detector 18 outputs a pulse signal for
detecting the timing of commencement of writing each scanning line
with respect to the photoconductive surface of the drum 1 each time
the laser beam L3 is incident on the laser-beam detector 18.
[0047] As shown in FIG. 2 the cylindrical lens 16 is fixed onto a
rotatable base (rotatable member) 22 which is mounted on the
housing 26 of the laser-beam scanner to be rotatable about a
rotational axis 16a relative to the housing 26. The scanning
optical system shown in FIG. 1 is enclosed in the housing 26. The
rotational axis 16a extends perpendicular to the optical axis of
the cylindrical lens 16 and the direction (path) of the laser beam
L3. Note that, in this embodiment, the optical axis of the
cylindrical lens 16 lies in a plane that is defined by the scanning
light beam emitted from the polygon mirror 8.
[0048] The cylindrical lens 16 can be rotated about the rotational
axis 16a to deflect the laser beam L3 which passes therethrough so
as to shift the same substantially in parallel on a plane which is
perpendicular to the rotational axis 16a to thereby either delay or
advance the timing of the incident laser beam L3 on the laser-beam
detector 18. Accordingly, the timing of commencement of writing
each scanning line with respect to the photoconductive surface of
the drum 1 can be adjusted by rotating the cylindrical lens 16.
[0049] The rotatable base 22, onto which the cylindrical lens 16 is
mounted, is provided with a disc portion 221 and a shaft 224 which
is formed integral with the disc portion 221. The rotatable base 22
is connected to the housing 26 so that the disc portion 221 is
rotatably fitted in a circular recess 222 with the shaft 224 being
rotatably fitted into a hole 223 formed at the center of the bottom
of the circular recess 222. With this structure, the rotatable base
22 is rotatable about the shaft 224 with respect to the housing 26
so that the cylindrical lens 16 can rotate about the rotational
axis 16a.
[0050] The rotatable base 22 is provided with a circumferential
slot 241 which extends circumferentially about the rotational axis
16a. A set screw 242 is inserted into the circumferential slot 241
so that the set screw 242 is screw-engaged with a female screw hole
243 formed at the bottom of the circular recess 222. The rotatable
base 22 can be rotated about the rotational axis 16a on the housing
26 when the set screw 242 is loosened while the rotatable base 22
cannot be rotated about the rotational axis 16a on the housing 26
when the set screw 242 is tightly fastened. Accordingly, the
circumferential slot 241, the set screw 242 and the female screw
hole 243 together constitute an adjusting device 24 for adjusting
the rotational position of the cylindrical lens 16 about the
rotational axis 16a and for fixing the same with respect to the
housing 26.
[0051] In the laser-beam scanner having such a structure, the laser
beam L1 emitted from the laser diode 2 is incident upon the
reflected mirror 6 via the collimating lens 4a and the cylindrical
lens 4b. Subsequently, the laser beam L1 is reflected by the
reflected mirror 6 to be incident upon the polygon mirror 8. The
polygon mirror 8 has a regular hexagonal cross section and is
provided along a circumference thereof with six reflecting surfaces
(scanning laser beam deflecting surfaces). The laser beam reflected
by the reflecting mirror 6 to be incident on the polygon mirror 8
is reflected by each of the six reflecting surfaces while the
polygon mirror 8 rotates. The laser beam reflected by the polygon
mirror 8 is incident on the f.theta. reflecting lens 10. The laser
beam L2 reflected by the f.theta. reflecting lens 10 to proceed
towards the f.theta. lens 12 passes therethrough to be reflected by
the reflecting mirror 20 to thereby proceed towards the
photoconductive surface of the drum 1. The laser diode 2 is
controlled to turn its laser emission ON and OFF in accordance with
given image data to draw a corresponding image (charge-latent
image) on the photoconductive surface of the drum 1; and
subsequently, the image drawn on the photoconductive surface of the
drum 1 is transferred to plain paper according to a conventional
electrophotographic method.
[0052] The polygon mirror 8 is rotated at a fast rotational speed
in the direction of the arrow "A" shown in FIG. 1, so that the
incident angle of the laser beam L1 on each reflecting surface of
the polygon mirror 8 varies. Hence, the laser beam L2 is deflected
by the polygon mirror 8 in the main scanning direction (indicated
by an arrow B in FIG. 1).
[0053] The laser beam L3 which is incident on the f.theta.
reflecting lens 10 to be reflected by the reflecting mirror 14
proceeds towards the cylindrical lens 16 rather than the f.theta.
lens 12. As described the above, when the laser beam L3 passes
through the cylindrical lens 16, the laser beam L3 which proceeds
towards the laser-beam detector 18 is deflected to shift
substantially in parallel on a plane which is perpendicular to the
rotational axis 16a. Namely, when the laser beam L3 passes through
the cylindrical lens 16, the laser beam L3 which proceeds towards
the laser-beam detector 18 is deflected in a direction to either
delay or advance the timing of commencement of writing each
scanning line with respect to the photoconductive surface of the
drum 1.
[0054] Each time the laser beam L3 is incident on the laser-beam
detector 18, the laser-beam detector 18 outputs a pulse signal. The
pulse signals output from the laser-beam detector 18 are input to a
processor (not shown), and subsequently, the processor generates
corresponding horizontal synchronizing pulses (HSYNC) to determine
the timing of commencement of writing main scanning data; i.e. each
main scanning line.
[0055] The horizontal synchronizing pulses are input to a clock
generator so that it synchronously generates corresponding clock
pulses. Subsequently the clock pulses are input to a memory for
storing image data, and the stored image signals are sequentially
read out of the memory in accordance with the input close pulses.
The laser diode 2 outputs the laser beam L1 which is modulated in
accordance with the image signals read out of the memory.
[0056] The way of adjusting the angular position of the cylindrical
lens 16 to deflect the incident laser beam so as to delay or
advance the timing of commencement of writing each scanning line
with respect to the photoconductive surface of the drum 1 will be
hereinafter discussed.
[0057] First of all, the rotatable base 22 having the cylindrical
lens 16 mounted thereon needs to be fitted in the circular recess
222, with the shaft 224 being fitted into the hole 223 and with the
set screw 242 being engaged with the female screw hole 243 through
the circumferential slot 241.
[0058] In this state, the set screw 242 is loosened and
subsequently the rotatable base 22 is slightly rotated clockwise or
counterclockwise about the shaft 224, i.e., the rotational axis
16a.
[0059] In the case where the cylindrical lens 16 is rotated
clockwise as viewed in FIG. 3A from the position shown by a solid
line to the position shown by a dotted line, the laser beam L3
incident on the laser-beam detector 18 is deflected to shift to the
left from the position shown by a solid line to the position shown
by a two-dotted chain line in FIG. 3A. When the polygon mirror 8 is
rotated, the laser beam L3 is scanned (moved) from right to left in
FIGS. 3A and 3B. Accordingly, the rotation of the cylindrical lens
16 as shown in FIG. 3A causes the laser-beam detector 18 to delay
the output of a pulse signal to thereby delay the timing of
commencement of writing each scanning line with respect to the
photoconductive surface of the drum 1.
[0060] On the other hand, in the case where the cylindrical lens 16
is rotated counterclockwise as viewed in FIG. 3B from the position
shown by a solid line to the position shown by a dotted line, the
laser beam L3 incident on the laser-beam detector 18 is deflected
to shift to the right from the position shown by a solid line to
the position shown by a two-dotted chain line in FIG. 3B. This
makes the laser-beam detector 18 to advance the output of a pulse
signal to thereby advance the timing of commencement of writing
each scanning line with respect to the photoconductive surface of
the drum 1.
[0061] After the adjustment of the timing of commencement of
writing each scanning line is completed, the set screw 242 is
tightly fastened to fix the disc portion 221 to the circular recess
222 of the housing 26, which completes the adjusting operation. The
cylindrical lens 16, the rotatable base 22, the circular recess 222
and the adjusting device 24 together constitute a light beam
incident position adjusting device.
[0062] It can be appreciated from the foregoing that the incident
position of the laser beam L3 with respect to the laser-beam
detector 18 can be easily and precisely adjusted by rotating the
rotatable base 22 about the rotatable axis 16a. Hence, with the
light beam incident position adjusting device, the timing of
commencement of writing each scanning line with respect to the
photoconductive surface of the drum 1 can be easily and precisely
adjusted by rotating the rotatable base 22 about the rotatable axis
16a.
[0063] FIG. 4 shows an embodiment in which, so as not to relatively
move, the laser-beam detector 18' (photo-detector) and the laser
diode 2' (light-beam emitter) are supported on a common circuit
substrate 100. In this construction, since the laser-beam detector
18' is fixed to the substrate 100, the type of adjusting device
that moves the photo-detector (i.e., the laser-beam detector 18')
cannot be used. However, in the above-described adjusting device of
the present invention, the cylindrical lens 16 is rotated in order
to perform adjustment; therefore, the timing of the incident laser
beam L3 on the laser-beam detector 18' can be adjusted regardless
of the type of photo-detector being utilized.
[0064] The device for adjusting the rotational position of the
cylindrical lens 16 (and fixing the cylindrical lens 16 to the
housing 26) is not limited solely to the particular aforementioned
device (i.e., the adjusting device 24) but can be any other device
as long as it bears a similar function. FIG. 5 shows another
embodiment of the adjusting device for adjusting the rotational
position of the cylindrical lens 16. In this embodiment the housing
26 is provided on a bottom surface thereof with a circular recess
222' which corresponds to the circular recess 222 of the previous
embodiment. A circular through hole 225 through which the
cylindrical lens 16 can be inserted in the housing 26 is formed at
the center of the bottom of the circular recess 222'. A rotatable
base 22', which corresponds to the rotatable base 22 of the
previous embodiment, is not provided with a shaft which corresponds
to the shaft 224 of the rotatable base 22. When the rotatable base
22' is set on the housing 26, the disc portion 221 of the rotatable
base 22' is rotatably fitted in the circular recess 222' with the
cylindrical lens 16 being inserted into the housing 26 through the
through hole 225. With such a adjusting (fixing) device, the
cylindrical lens 16 can be fixed to the housing 26 in place from
outside the housing 26, which makes it easier to set the
cylindrical lens 16 on the housing 26.
[0065] In the aforementioned embodiments, the rotatable base 22 (or
22') is fixed to the housing 26 using only one set screw 242.
However, the rotatable base 22 (or 22') can be fixed to the housing
using more than one set screw. FIG. 6 shows another embodiment
using two set screws 242 to fix the disc portion 221 of the
rotatable base 22 to the housing 26. FIG. 7 shows yet another
embodiment using three set screws 242 to fix the disc portion 221
of the rotatable base 22 to the housing 26. In FIG. 6 the two set
screws 242 are positioned on respective sides with respect to the
path of the laser beam L3 so as to face respective ends (right and
left ends as viewed in FIG. 6) of the cylindrical lens 16. In FIG.
7 the three set screws 242 are positioned at regular intervals in a
circumferential direction of the disc portion 221.
[0066] FIG. 8 shows another embodiment of the adjusting device for
adjusting the rotational position of the cylindrical lens 16. In
this embodiment the disc portion 221 is fixed to the housing 26 by
a adjusting device 30 which is composed of a leaf spring 302 and
two set screws 303 for securing the leaf spring 302 to the housing
26. The leaf spring 302 has a substantially rectangular shape and
is provided at a center thereof with a circular hole 301 in which
the cylindrical lens 16 is positioned. The longitudinal length of
the leaf spring 302 is larger than the diameter of the disc portion
221 so as to press the same against the housing 26. The leaf spring
302 is provided, on a surface thereof facing the disc portion 221,
with two projections 304 which are positioned on respective sides
with respect to the cylindrical lens 16 to be aligned along the
path of the laser beam L3, as can be seen in FIG. 8. The leaf
spring 302 is further provided at respective ends thereof with two
slits through which the two set screws are respectively inserted to
be screwed into the housing 26. In a state where the leaf spring
302 is tightly secured to the housing 26 by the set screws 303, the
two projections 304 of the leaf spring 302 come into pressing
contact with the disc portion 221, so that the disc portion 221 is
tightly held between the leaf spring 302 and the housing 26, so
that the disc portion 221 is fixed to the housing 26.
[0067] FIG. 9 shows yet another embodiment of the adjusting device
for adjusting the rotational position of the cylindrical lens 16.
In this embodiment the disc portion 221 is fixed to the housing 26
by a adjusting device 40 which includes a leaf spring 402 and a set
screw 403 for securing the leaf spring 402 to the housing 26. The
leaf spring 402 has a substantially U-shape and is provided with
two parallel projecting portions 401 between which the cylindrical
lens 16 is positioned. The projecting portions 401 are positioned
on respective sides relative to the path of the laser beam L3, as
can be seen in FIG. 9. Each projecting portion 401 is provided, at
its tip on a surface thereof facing the disc portion 221, with a
projection 404. In a state where the leaf spring 402 is tightly
secured to the housing 26 by the set screw 403, the two projections
404 of the leaf spring 402 come into pressing contact with the disc
portion 221, so that the disc portion 221 is tightly held between
the leaf spring 402 and the housing 26, so that the disc portion
221 is fixed to the housing 26.
[0068] FIG. 10 shows an embodiment of device for rotating the
cylindrical lens 16. In this embodiment, the cylindrical lens 16 is
positioned in place by inserting the same into the housing 26 from
outside the housing 26, and the operation of rotating the
cylindrical lens 16 can be carried out from outside the housing
26.
[0069] In this embodiment, similar to the embodiment shown in FIG.
5, the housing 26 is provided on a bottom surface thereof with a
circular recess 222'. A circular through hole 225 through which the
cylindrical lens 16 can be inserted in the housing 26 is formed at
the center of the bottom of the circular recess 222'. The disc
portion 221 of this embodiment is provided with two circumferential
slots 241 for fixing the disc portion 221 to the housing 26 by two
set screws 242 respectively inserted into the two circumferential
slots 241. The disc portion 221 is further provided with a radial
slot 601 which extends in a radial direction of the disc portion
221. The disc portion 221 is rotatably fitted in the circular
recess 222' with the cylindrical lens 16 being inserted into the
housing 26 through the through hole 225. A tool 603 is used to
rotate the cylindrical lens 16. The tool 603 is provided at the tip
thereof with an engaging pin 602 which can be inserted into the
radial slot 601. The axis of the engaging pin 602 extends parallel
with, but deviates from, the rotational axis of the tool 603, so
that the disc portion 221 is rotated when the tool 603 rotates
about its rotational axis with the engaging pin 602 being inserted
into the radial slot 601. Each set screw 242 needs to be loosened
in advance when the disc portion 221 is rotated by the tool 603.
The slot 601 and the tool 603 together constitute a device 60 for
externally rotating the cylindrical lens 16.
[0070] In a state where the engaging pin 602 is engaged with the
radial slot 601, rotating the tool 603 without moving the same in a
radial direction thereof causes the disc portion 221 (the
cylindrical lens 16) to rotate clockwise or counterclockwise in a
direction shown by an arrow in FIG. 10. Hence, with the use of the
device 60, the incident position of the laser beam L3 on the
laser-beam detector 18 can be finely and easily adjusted even from
outside the housing 26 of the scanner. After the adjusting
operation (i.e., the rotation of the cylindrical lens 16) is
completed, the tool 603 is disengaged from the disc portion 221 and
subsequently each set screw 242 is tightly fastened to fix the disc
portion 221 to the circular recess 222' of the housing 26, which
completes the adjusting operation.
[0071] FIG. 11 shows another embodiment of a device for rotating
the cylindrical lens 16. In this embodiment, similar to the
previous embodiment shown in FIG. 10, the cylindrical lens 16 is
positioned in place by inserting the same into the housing 26 from
outside the housing 26, and the operation of rotating the
cylindrical lens 16 can be carried out from outside the housing 26.
The housing 26 is provided on a bottom surface thereof with a
circular recess 222'. A circular through hole 225 through which the
cylindrical lens 16 can be inserted in the housing 26 is formed at
the center of the bottom of the circular recess 222'. The disc
portion 221 of this embodiment is provided with two circumferential
slots 241 for fixing the disc portion 221 to the housing 26 by two
set screws 242 respectively inserted into the two circumferential
slots 241. The disc portion 221 is further provided on an outer
peripheral surface thereof with a circumferential gear 701. The
disc portion 221 is rotatably fitted in the circular recess 222'
with the cylindrical lens 16 being inserted into the housing 26
through the through hole 225. The housing 26 is provided with a
small circular recess 226 which is connected with the circular
recess 222'. In this embodiment a tool 703 is used to rotate the
cylindrical lens 16. The tool 703 is provided at the tip thereof
with a pinion gear 702 which can be fitted in the small circular
recess 226. The pinion gear 702 meshes with the circumferential
gear 701 of the disc portion 221 when the pinion gear 702 is fitted
in the small circular recess 226. Each set screw 242 needs to be
loosened in advance when the disc portion 221 is rotated by the
tool 703. The circumferential gear 701, the tool 703 and the small
circular recess 226 together constitute a device 70 for rotating
the cylindrical lens 16.
[0072] The pinion gear 702 is engaged with the circumferential gear
701 by inserting the pinion gear 702 into the small circular recess
226 when the cylindrical lens 16 needs to be rotated. In a state
where the pinion gear 702 is engaged with the circumferential gear
701, rotating the tool 703 causes the disc portion 221 (the
cylindrical lens 16) to rotate clockwise or counterclockwise in a
direction shown by an arrow in FIG. 11. Hence, with the use of the
device 70, the incident position of the laser beam L3 on the
laser-beam detector 18 can be finely and easily adjusted even from
outside the housing 26 of the scanner. After the adjusting
operation (i.e., rotation of the cylindrical lens 16) is completed,
the tool 703 is taken out of the small circular recess 226 of the
housing 26 and subsequently each set screw 242 is tightly fastened
to fix the disc portion 221 to the circular recess 222' of the
housing 26, which completes the adjusting operation.
[0073] In each of the aforementioned embodiments, although the
cylindrical lens 16 as an optical member is fixed to the disc
portion 221, the cylindrical lens 16 can be replaced by a
plane-parallel plate to attain a similar effect. FIGS. 3A and 3B
show a sectional portion of the cylindrical lens 16; the sectional
portion of the cylindrical lens 16 does not have any power in
scanning (beam shifting) direction (right to left in FIGS. 3A and
3B) with respect to the laser-beam detector 18. In view of this
aspect, if this sectional portion is replaced by an equivalent
plane-parallel plate that does not have any power in the scanning
direction, a similar beam-shifting effect as shown in FIGS. 3A and
3B is carried out by rotating the plane-parallel plate. However, a
cylindrical lens 16 is used in the above-described embodiment as
the cylindrical lens facilitates collection of the laser beam L3
onto the laser-beam detector 18.
[0074] Obvious changes may be made in the specific embodiments of
the present invention described herein, such modifications being
within the spirit and scope of the invention claimed. It is
indicated that all matter contained herein is illustrative and does
not limit the scope of the present invention.
* * * * *