Light beam deflection means

A light beam deflection unit for deflecting a light beam has a carrier seated in rotatable fashion around an optical axis, a reflector arranged at the rotatable carrier, and a reflection face oriented transversely relative to the optical axis. The carrier is connected to a sleeve that laterally surrounds the reflector at least in certain regions, and that rotates with the carrier. The sleeve has a light entry aperture for the incident light beam at an end face facing away from the reflector, and a light exit aperture for the deflected light beam in the generated surface. An achromatic lens that is displaceable in the direction of the optical axis for the purpose of focussing the light beam and that is held by the sleeve is located in the light entry aperture. A wedge-shaped, transparent insert is arranged in the light exit aperture for astigmatism correction.

BACKGROUND OF THE INVENTION 
The invention is in the field of electronic reproduction technology and is 
directed to a light beam deflection unit in a scanner device for an 
originals scanning apparatus or recording apparatus. Such a scanner device 
essentially comprises a light source, for example a laser light source, 
that generates a light beam that is periodically deflected across a 
subject with the rotating light beam deflection unit. 
In an originals scanning apparatus, also referred to as input scanner, a 
light beam generated in a scanner device is conducted pixel-by-pixel and 
line-by-line over an original to be scanned, and the scan light the 
original reflects or allows to pass is converted into an image signal by 
an optoelectronic transducer. In a recording apparatus, also referred to 
as a recorder, exposer or output scanner, the light beam acquired in a 
scanner device is modulated in intensity by an image signal for recording 
information and is conducted pixel-by-pixel and line-by-line across a 
light-sensitive recording material. 
In the case of a flat bed scanner, the holder for the original or, the 
recording material is a plane surface over which the light beam is 
conducted pixel-by-pixel and line-by-line, and which moves relative to the 
scanner device. In the case of an inside drum apparatus, the holder for 
the original or, for the recording medium is designed as a stationary 
half-shell or trough. The scanner device moves parallel to the 
longitudinal axis of the holder, and the light beam is radially conducted 
over the original or, the recording material perpendicular to the 
longitudinal axis. 
An inside drum apparatus is disclosed, for example, by EP-A-0 354 028. The 
light beam deflection unit therein is designed as a reflective surface 
arranged transversely relative to the direction of light propagation and 
is connected to a rotating shaft. The light beam is conducted onto a 
recording material with the assistance of the reflective surface. 
Contaminants can collect at the reflective surface during operation of the 
recording apparatus, and air turbulence can arise at high speeds due to 
the asymmetrical design with respect to the axis of rotation. This air 
turbulence leads to noise loads, causes additional dirt in the region of 
the reflective surface and deteriorates the uniform rotation of the 
reflective surface. 
DE-A41 24 229 already discloses a light beam deflection means with a light 
entry face and a light exit face for the perpendicularly deflected light 
beam that is composed of a rotationally seated carrier prism and of a 
light-transmissive deflection prism that extends in the direction of its 
rotational axis. The surface of the deflection prism adjoining the carrier 
prism is designed as a reflection face that proceeds transversely relative 
to the rotational axis. The deflection prism is glued to the carrier 
prism, and the two prisms supplement each other at least in regions to 
form a unit that is symmetrical relative to the rotational axis. 
Disk-shaped cover elements that project beyond the unit in radial expanse 
are arranged to the side of the unit. 
Only slight air turbulence, contamination and unquiet running in fact occur 
in this light beam deflection unit due to the cover elements; the 
manufacture thereof, however, is comparatively complicated since the cover 
elements must be precisely manufactured and precisely centered at the 
unit. 
DE-A41 30 977 discloses another light beam deflection unit that is composed 
of a transparent body designed as a spherical segment that has a light 
entry face, a reflection face, and a light exit face, and is further 
composed of a carrier member likewise designed as a spherical segment that 
is glued to the transparent body at the reflection face. The unit formed 
of the transparent body and of carrier member is rotatable around an axis 
residing vertically relative to the light entry face and has an outside 
contour that is rotational-symmetrical at least with reference to the 
axis. As a result of the spherical designing of the light beam deflection 
unit, this can rotate at a relatively high speed without creating 
significant air turbulence and bearing noise. 
The known light beam deflection units have proven themselves well up to 
now. However, light sources, preferably laser light sources, with higher 
luminous power are required for exposing certain recording materials. In 
practice, the required luminous powers can currently only be generated by 
light sources that generate light with a greater wavelength of, for 
example, 1064 nm. In order to deflect a light beam having a greater 
wavelength, the light beam deflection units must have a correspondingly 
large entry aperture in order to obtain comparable pixel sizes and line 
widths in the exposure, despite the greater wavelength. 
The enlargement of the entry aperture in a light beam deflection unit, 
however, results in an increase in the running noises and in unquiet 
running. A further disadvantage is that the air turbulences contaminate 
the reflective surfaces of the light beam deflection unit, this leading to 
optical losses and, thus, poorer reproduction quality. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to design a focussing 
light beam deflection unit such that is has a large entry aperture, and 
air turbulences and unquiet running are reduced and contamination of the 
reflective surfaces is prevented. 
According to the invention, a light beam deflection unit is provided having 
a carrier seated in rotatable fashion around an optical axis. A reflector 
is arranged on the rotating carrier and has a reflection face oriented 
transversely relative to the optical axis. A sleeve is connected to the 
carrier and which laterally at least partially surrounds the deflector. 
The sleeve has a light entry aperture for an incident light beam at an end 
facing away from the reflector and a light exit aperture for a light beam 
deflected by the reflector in a generated surface of the sleeve. At least 
one lens is held by the sleeve at the light entry aperture for focusing 
the light beam. The transparent insert is provided in the light exit 
aperture. 
The invention is explained in greater detail below with reference to FIGS. 
1 and 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows a longitudinal section through the light beam deflection unit 
of the invention. A reflector 1 is connected to a carrier 2 that is 
coupled to a rotatable shaft 3. The shaft 3 is guided in a mount 4. The 
reflector 1 is arranged inside a housing designed as a dynamically 
balanced sleeve 5 that is connected to the carrier 2. The connection can 
occur via screws 6. The hollow-cylindrical sleeve 5 comprises a light 
entry aperture 7 at the end face facing away from the reflector 1 and 
comprises a light exit aperture 8 in the generated surface. 
At least one lens, preferably an achromatic lens 9, that is symmetrically 
arranged relative to an optical axis 10, is located in the light entry 
aperture 7. The optical axis 10 simultaneously forms the rotational axis 
for the light beam deflection unit. 
The achromatic lens 9 is displaceable in the direction of the optical axis 
10 for the purpose of adjustment and can be fixed in the ultimate position 
in the sleeve 5 after the adjustment, for example by gluing. The 
adjustment occurs such that a reflected light beam 11 is focussed onto a 
subject plane 12. 
The light exit aperture 8 is closed by a transparent insert 13 that 
comprises a planar inner light passage face 14 and a planar outer light 
passage face 15. The light passage faces 14; 15 are preferably aligned in 
wedge-like fashion relative to one another, whereby the outer light 
passage face 15 is oriented parallel to the optical axis 10 or, parallel 
to the surface line of the sleeve 5. The angle between the light passage 
faces 14; 15 aligned in wedge-like fashion relative to one another can 
vary dependent on the respective reflection angle of the light beam 11. 
The wedge-shaped, transparent insert 13 is glued into the light exit 
aperture 8. An astigmatism correction can be advantageously implemented 
with the wedge-shaped insert 13. 
In order to enhance the stability of the device and for the best possible 
approximation of the insert 13 to the outside contour of the sleeve 5, the 
outside limitation of the insert 13 preferably has slanting sides 16, so 
that the crossectional area of the insert 12 is essentially designed 
trapezoidal in both expanses. 
The reflector 1 has a reflection face 17 or mirror face oriented at a slant 
relative to the optical axis 10. The reflector 1 is composed of, for 
example, polished aluminum, and the reflection face 17 comprises, for 
example, a gold coat. The angle of inclination .beta. of the reflection 
face 17 relative to the optical axis 1 can, for example, lie in the range 
from 45.degree. through 70.degree.. In the illustrated exemplary 
embodiment, for example, the angle of inclination .beta. amounts to 
65.degree.. A resistant embodiment of the reflector 1 is achieved in that 
the reflector 1 comprises an essentially cylindrical basic shape, and the 
reflection face 17 is designed as an obliquely arranged cylindrical 
section. 
The light beam 11 generated in a stationary light source not shown is 
incident through the light entry aperture 7 and the achromatic lens 9 10 
onto the reflection face 17 of the reflector 1. The light beam 11 
deflected by the reflection face 17 proceeds through the light exit 
aperture 8 onto the subject plane 12, on which a recording material to be 
exposed is fixed in that case when the light beam deflection unit is 
employed in an exposer. 
As a result of arranging the reflector 1 in a sleeve-shaped housing, a 
compact light beam deflection unit that has an essentially dynamically 
balanced outside contour advantageously arises. As a result of the light 
entry aperture 7 being closed by the achromatic lens 9 and the light exit 
aperture 8 being closed by the transparent insert 13, an encapsulated 
interior that prevents a contamination of the reflection face 17 of the 
reflector 1 preferably arises. 
The sleeve 5 is provided with an all around flange 18 in which bores 19 are 
arranged for the passage of the screws 6. Outside threads of the screws 6 
engage into the inside thread of the carrier 2. The carrier 2 accepts an 
end piece of the shaft 3 in a recess 20. For centering the reflector 1, 
the carrier 2 has a centering peg 21 that is introduced into a centering 
bore 22 of the reflector 1. The centering bore 22 and the centering peg 21 
extend symmetrically relative to the optical axis 10. 
The achromatic lens 9 is held by an insert 23 that is displaceable in the 
direction of the optical axis 10 relative to the sleeve 5 for the purpose 
of focussing the light beam 11. 
The reflector 1 has weight compensation bores 24 in order to achieve a 
symmetrical distribution of the material relative to the optical axis 10 
and to simultaneously achieve a reduction in weight. The weight 
compensation bores 24 extend from the carrier 2 of the reflector 1 in the 
direction toward the reflection face 17 without, however, penetrating the 
latter. 
A balancing given high mechanical stability at the same time can be 
achieved in that three weight compensation bores 24 are provided. An 
effective arrangement of the weight compensation bores 24 is produced in 
that they extend along the outside circumference of the reflector 1. A 
space-saving arrangement is achieved by weight compensation bores 24 
arranged adjacent to one another. 
The employment of the light beam deflection unit of the invention makes it 
possible to utilize an enlarged entry aperture corresponding to the 
greater wavelength and to generate comparable line widths and pixel or, 
dot sizes despite the greater wavelength. The light beam deflection unit 
can also be fundamentally employed for the deflection of light beams with 
a shorter wavelength, whereby an improvement in quiet running and a 
reduction in the tendency to become contaminated are likewise achieved 
compared to the prior art. Over and above this, the light beam deflection 
unit has the advantage that it is modularly constructed, as a result unit 
each structural module can be individually balanced with respect to the 
rotational axis and, thus, fabrication can be simplified. 
In a view onto the reflector 1, FIG. 2 shows the position of the weight 
compensation bores 24 relative to the centering bore 22. Three weight 
compensation bores 24 are provided, these extending on a circle around the 
centering bore 22. Connecting lines of the mid-point of the centering bore 
22 with the mid-points of the weight compensation bores 24 lying at the 
outside erect an angle of 90.degree.. The positioning of the weight 
compensation bores 24 is selected such that both a high stability as well 
as a symmetrical weight distribution relative to the optical axis 10 as a 
rotational axis are achieved. The reflector 1 is mounted on the carrier 2 
over which a cylindrical section 25 with the reflection face 17 (not 
visible) rises. 
Although various minor changes and modifications might be proposed by those 
skilled in the art, it will be understood that our wish is to include 
within the claims of the patent warranted hereon all such changes and 
modifications as reasonably come within our contribution to the art.