Semiconductor laser and optical system having a collimator lens

Details Semiconductor laser and optical system having a collimator lens Semiconductor laser and optical system having a collimator lens

2001-09-06

2003-07-22

Phan, James (Department: 2872)

Optical: systems and elements

Deflection using a moving element

C359S212100, C359S216100, C359S227000

Reexamination Certificate

active

06597486

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to optical systems and, more particularly, to an optical system used for laser beam printers, digital PPC and the like which has a semiconductor laser accommodated within a case to emit laser light to be delivered to a collimator lens through a window formed in the case.
2. Description of the Prior Art
There is shown, in
FIG. 6
, a laser beam printer
1
having a conventional optical system of this kind. In this laser beam printer
1
, a semiconductor laser unit
2
emits laser light to be irradiated to a photosensitive drum
8
through a collimator lens
3
, a cylinder lens
4
, a polygon mirror
5
, f-&thgr; lenses
6
a
and
6
b
, a reflection mirror
7
and so on. Due to this, an electrostatic latent image is formed on the photosensitive drum
8
, which is then toner-developed so that a toner image formed is transferred onto a recording paper.
The semiconductor laser unit
2
used in this laser beam printer
1
includes, as shown in
FIG. 7
, a case
2
b
having a window
2
a
. Within the case
2
b
, a heat-sink
2
c
is provided. The heat-sink
2
c
has a semiconductor laser
2
e
mounted on a lateral surface thereof through a sub-mount
2
d
. A cover formed of a transparent material, such as glass, is fitted on an inner side of the window
2
a
. Meanwhile, the collimator lens
3
is arranged at one end of a lens barrel
3
a
, while the lens barrel
3
a
at the other end is faced to the window
2
a
of the semiconductor laser unit
2
. Consequently, the laser light emitted from the semiconductor laser
2
e
is given onto the collimator lens
3
through the window
2
a
and lens barrel
3
a
, and further to a polygon mirror
5
via the cylindrical lens
4
.
In the prior art, the laser light emitted from the semiconductor laser
2
e
is delivered to the collimator lens
3
through the window
2
a
and lens barrel
3
a
. Accordingly, part of the laser light reflects upon the window
2
a
or the lens barrel
3
a
and thus turns into stray light. Such stray light might travel off the normal path and go onto the photosensitive drum
8
. For example, if part of laser light deviates from the polygon mirror
5
and comes to and reflected upon a drive motor
5
a
or the like, there is a fear that the laser light acts as a rest beam on the photosensitive drum
8
thus resulting in undesired printing (vertical straight line).
SUMMARY OF THE INVENTION
Therefore, it is a primary object of the present invention to provide an optical system which can prevent undesirable printing due to stray light thereby improving image quality.
The present invention is an optical system, comprising: a semiconductor laser; a case accommodating the semiconductor laser and having a window to pass through laser light emitted from the semiconductor laser; a collimator lens for turning the laser light passed through the window into a parallel luminous flux; a reflector for reflecting the laser light in a parallel luminous flux toward a main scanning direction; a light collector for collecting the laser light reflected on a scanning surface; and a light shield member provided between the semiconductor laser and the collimator lens and having a pinhole to allow the laser light passed through the window to pass through.
The laser light spread with a predetermined angle or greater with respect to an axis of the semiconductor laser or that reflected upon an inner surface of the window formed in the case, in most part, does not pass through the pin hole formed through the light shield member. Also, the laser light reflected upon the window inner surface or pinhole inner surface, in greater part, attenuates due to the reflection. Accordingly, there is no occurrence of stray light that might cause undesired printing.
According to the present invention, image quality is improved because undesired printing is prevented.
The above described objects and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.


REFERENCES:
patent: 5035476 (1991-07-01), Ellis et al.

Affiliated with

Also associated with

Rating

Semiconductor laser and optical system having a collimator lens does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Semiconductor laser and optical system having a collimator lens, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Semiconductor laser and optical system having a collimator lens will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3039145