Filter driving mechanism for color optical reader

A durable filter driving mechanism for a color optical reader that is capable of being positively and accurately positioned is proposed. The filter driving mechanism includes a guiding piece mounting thereon a reduction gear assembly having a reduction gear set meshing with a rack of a sliding piece having a rail coupling thereto a color filter assembly operating in cooperation with a lens assembly and a charge coupled element.

BACKGROUND OF THE INVENTION 
The present inventin relates to a driving mechanism, and more particularly 
to a filter driving mechanism for a color optical reader or scanner. 
The conventional filter driving mechanism for a color optical reader, as 
shown in FIG. 1, includes a filter frame 1, two side belt wheels 6, 7 and 
a transmitting belt 8 which is connected to a first connecting portion 4a 
of frame 1, wound around wheel 6, extended through guiding members 5c, 5b, 
and 5a of frame 1, wound around wheel 7 and connected to a second 
connecting portion 4b of frame 1 so that belt 8 can move frame 1 in the 
desired direction. 
The filter is brought into scanning positin by belt 8 which, however, is 
elastic, has poor rigidity and a large inertia so that the scanning 
position for filter frame 1 always tends to produce a deviation. In 
addition, belt 8 is relatively easily fatigued owing to its frequent use 
and has a shortened life-span if it is excessively tightened. Furthermore, 
belt 8 is loosely guided by guiding members 5a-5c of filter frame 1 so 
that filter frame 1 cannot be moved steadily and positively guided since 
belt 8 has a variable elasticity. 
SUMMARY OF THE INVENTION 
It is therefore an objective of the present invention to provide a filter 
driving mechanism for a color optical reader that enables the color filter 
assembly thereof to be positively positioned and steadily moved. 
It is a further objective of the present invention to provide a durable 
filter driving mechanism for a color optical reader. 
The present invention provides a filter driving mechanism for a color 
optical reader which includes a guiding piece having a bottom sliding 
groove and a guiding groove, a sliding piece having a rack and a raised 
rail having a coupling groove and at least two flexible coupling hooks, a 
color filter assembly having a frame on which are evenly arranged a 
plurality of filtering glasses, a bottom coupling portion provided with at 
least two coupling holes respectively coupling therein the coupling hooks 
when the coupling portion is inserted into the coupling groove, and a 
reduction gear assembly mounted on the guiding piece and having a 
reduction gear set engaging with the rack.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to FIGS. 2-5, a filter driving mechanism for a color optical 
reader according to the present invention includes a guiding piece 10 of a 
reduction gear assembly having a housing 11 and a reduction gear set 20, a 
stepping motor 30, a sliding piece 40, and a color filter assembly 50. 
Guiding piece 10 has a bottom sliding groove 17, a guiding groove 18 
communicating with sliding groove 17 and a bottom cover 19 to cover 
sliding piece 40 in sliding groove 17. 
Housing 11, closed by cover 13 having stepping motor 30 affixed thereto and 
being fixed to housing 11 by a plurality of screws 12 transversing through 
screw holes 14, includes a plurality of positioning shafts 16 for 
respectively mounting thereon the gears of reduction gear set 20, and a 
plurality of positioning cylinders 15 into which screws 12, transversing 
through screw holes 14, respectively lodge. 
Sliding piece 40 slidably received in sliding groove 17 includes a rack 41 
and a raised rail 42 which projects above guiding groove 18 and has a 
coupling groove 43 the defining wall of which includes at least two 
flexible coupling hooks 44 each of which includes a downwardly inwardly 
extending hooking portion 45. The sliding friction of sliding piece 40 can 
be reduced if piece 40 is provided with fine rollers. 
Color filter assembly 50 includes a generally rectangular frame 51 evenly 
arranging therein a translucent filtering glass T, a red filtering glass 
R, a green filtering glass G and a blue filtering glass B. The color 
filter assembly 50 also has a coupling portion 56 provided with at least 
two coupling holes 57 capable of respectively retaining therein hooking 
portions 45 of hooks 44 when coupling portion 56 has been aligned and 
inserted into coupling groove 43 to forcedly pass hooking portions 45 
after sliding piece 40 is received in sliding groove 17 and rack 41 is 
caused to mesh with the driving gear 21 of reduction gear set 20 which 
means that raised rail 42 projects above guiding groove 18. Color filter 
assembly 50 must work with a lens assembly 60 and a charge coupled element 
70, both of which are known and deserve no further description here, in 
order that any one of glasses T, R, G, and B can be correctly positioned 
in front of the lens. 
The operation of the present invention is now described as follows: 
After being energized, the present invention will automatically determine 
the magnitude of the image signal. If glass T is not positioned in front 
of lens assembly 60, color filter assembly 50 will be moved by the 
cooperation of reduction gear assembly 20 and sliding piece 40 to the 
position shown in FIG. 3. If the movement of color filter assembly 50 is 
out of synchronization or encounters an obstacle, the designed system 
control will command stepping motor 30 to first leftwardly and then 
rightwardly move assembly 50 in order to obviate the obstacle. If the 
obstacle cannot be obviated or the set steps are exceeded, an error signal 
will be generated to protect the present invention and to notify the user. 
In dealing with the plain image, the gray scale, the monochrome scale or 
the semi-color scale of the present invention, T glass is capable of 
performing the scanning task at one time during which the present 
permanently magnetic stepping motor 30 is "locked" to maintain the 
"holding torque" to prevent color filter assembly 50 from shaking. 
In color-scanning, stepping motor 30 will rightwardly move filter assembly 
50 an appropriate distance to position R glass in front of lens assembly 
60 within about 0.38 sec to determine by the image signal whether filter 
assembly 50 is correctly positioned. If not, filter assembly 50 is first 
leftwardly moved to the position shown in FIG. 3 and again rightwardly 
moved 18 mm to automatically correct and obviate the obstacle. If the 
obstacle still is not obviated, an error signal will be generated to 
notify the user. 
The color-scanning operation of the mechanism of the present invention is 
executed according to systematic instructions and obtains continuity by 
the coordination of the software, and the hardware. Filtering glasses R, 
G, and B can be selected to match with the exposing or main-scanning time 
(i.e., the X-axis) of the charge coupled element 70 and to complete the 
operation of the sub-scanning (i.e., the Y-axis). 
Through the above description, it should now become readily apparent how 
and why the present invention can achieve the objectives it contemplates. 
It should also be clear that the scanning speed and effectiveness of the 
present invention are also increased and improved. It should also be 
understood that modifications to the above described embodiment can be 
made by those skilled in the art without departing from the spirit and 
scope of the present invention.