Rotary scanner

An apparatus positions a rotary drum having an axis of rotation in an image scanner having a frame to position an image source mounted on the rotary drum. A way is mounted to the frame. A headstock and a tailstock are disposed and arranged to receive and support the rotary drum and are independently mounted on the way for lineal movement along the axis of the drum. A drum drive device rotates the drum about the axis and a headstock drive device linearly moves the headstock along the axis in first and second opposite directions. A stop block is supported by the frame and impedes a linear movement of the tailstock in the second direction at a selected stop position. A connector connects the headstock to the tailstock to cause the tailstock to move linearly along the axis in response to the movement of the headstock and includes a disengaging mechanism to disengage the tailstock from the headstock when the tailstock is at the selected stop position to permit the headstock to continue to move in the second direction.

BACKGROUND OF THE INVENTION 
The present invention relates generally to image scanners for providing a 
digitized image of a document, and in particular, to a rotary drum scanner 
for providing a digitized image from a transparent or reflective document. 
Image scanners are utilized for digitizing both text and image sources. The 
image sources scanned include conventional documents such as letters, 
memoranda, photographs, transparencies, and the like. The two principle 
types of image scanners are flat bed scanners and rotary scanners. Flat 
bed scanners are constructed so that the image source is mountable on a 
flat surface or "bed." The image source is scanned from side to side and 
line by line and then processed into a desired digital image which is in a 
form suitable for high-speed processing. A problem with using flat-bed 
scanners is the complexity of the scanner which requires careful 
adjustment in order to maintain image quality. In addition, the resolution 
and the dynamic range of the digital image is limited because of the 
nature of the linear array used for scanning the image. Consequently, 
flat-bed image scanners are used in applications which do not require a 
high resolution or a wide dynamic range because flat-bed scanners have 
traditionally been priced at the low end of the image scanner price range. 
A rotary scanner utilizes a rotary drum to mount the image source. The 
rotary scanner rotates the drum and linearly positions the drum to permit 
a light source to illuminate portions of the image source. An optical 
processing unit of the image scanner contains a scanning device which 
scans the illuminated portions of the image to form the digitized image. 
Both the light source and the scanning device are fixed in position and 
the rotary drum is moved linearly and rotated relative to the light source 
and the scanning device. Because the relative motion between the drum and 
the scanning device is primarily rotational in nature, high scanning rates 
can be achieved. The high scanning rates produce digital images with high 
resolutions and increase dynamic ranges. Thus, rotary scanners are 
typically used in commercial operations. Nevertheless, the nature of the 
rotary scanner has typically made it more expensive than flat-bed 
scanners. Thus, there is desire for a rotary scanner which provides high 
quality resolution and broad dynamic range at a lower cost than existing 
rotary scanners. 
One problem associated with rotary scanners is that removing the drum to 
place a new image source on the drum has traditionally required complex 
alignment procedures. A quick release mechanism eases the removal of the 
drum. The Boston U.S. Pat. No. 4,024,518 discloses a rotary image scanner 
which includes such a quick release mechanism. The Boston patent mounts 
the drum between a headstock assembly and a tailstock assembly. The 
tailstock assembly is movably mounted on a carrier rail for axial movement 
towards the headstock assembly. The tailstock assembly has a spring 
loaded, conically tapered moving center element corresponding to a conical 
taper on the drum. Axial movement of the tailstock assembly is controlled 
by an actuator assembly where a handle of the actuator assembly is moved 
in a direction to move the tailstock assembly in an axial direction 
towards the headstock assembly. The moveable center element of the 
tailstock engages the left-hand conical drum aperture and moves the drum 
to the right until the right-hand tapered drum aperture is seated on the 
drum spindle. In this way, the drum is actually aligned with a rotational 
axis of the drive spindle. 
Another type of quick release mechanism is used in the Howtek, Inc. Scan 
Master D4000 image scanner. Again, the drum is mounted between a headstock 
and a tailstock. However, unlike the Boston patent, the headstock and 
tailstock are fixedly mounted to a first carriage and a second carriage 
respectfully. The first carriage is fixedly mounted on a base, and the 
second carriage is movably mounted on the base. The Howtek Scanner 
includes an arm mounted on one of the carriages and rotatable to force the 
carriages apart, which allows the drum to be inserted when the arm is in 
the open position to force the carriages apart. In addition, a spring 
inner-connects the carriages to bias the carriages towards each other when 
the arm is in the closed position so that the drum is secured between the 
headstock and the tailstock. 
SUMMARY OF THE INVENTION 
The present invention relates to a first apparatus for positioning a rotary 
drum having an axis of rotation in an image scanner having a frame to 
position an image source mounted on the rotary drum so that a light source 
illuminates a selected portion of the image and to enable an analyzing 
device to analyze the selected portion of the image source. The apparatus 
includes a way mounted to the frame. A headstock is disposed and arranged 
to receive and support a first end of the rotary drum. A tailstock is 
disposed and arranged to receive and support a second end of the rotary 
drum. The headstock and tailstock are independently mounted on the way for 
linear movement along the axis of the drum. Drum drive means rotates the 
drum about the axis. Headstock drive means linearly moves the headstock 
along the axis in first and second opposite directions. A stop block is 
supported by the frame and impedes a linear movement of the tailstock in 
the second direction at a selected stop position. A connector connects the 
headstock to the tailstock to cause the tailstock to move linearly along 
the axis in response to the movement of the headstock. The connector 
includes a disengaging mechanism to disengage the tailstock from the 
headstock when the tailstock is at the selected stop position to permit 
the headstock to continue to move in the second direction. 
A second form of the invention relates to a second apparatus for sensing 
and processing image source signals from an image source mounted on a 
rotary drum of an image scanner and illuminated by a light source. This 
second apparatus includes a receiver lens for receiving and focusing light 
representative of the image source. An aperture receives and projects the 
light focused by the receiver lens. The second apparatus includes a 
substantially opaque housing. A condenser lens is mounted in a wall of the 
housing and receives and projects light transmitted through the aperture. 
A light splitter is disposed inside the housing and splits the light 
projected by the condenser lens into a plurality of light beams. A 
plurality of light filters are disposed in the housing for filtering 
selected portions of the light spectrum from the plurality of light beams. 
A plurality of photo-multiplier tubes corresponding to the plurality of 
light filters receive the plurality of light beams filtered by the light 
filters. Each photo-multiplier tube provides a voltage level based on the 
intensity of the incident filtered light beam. 
In a preferred embodiment of the first apparatus according to the present 
invention, the connector includes a connecting rod having a first end 
fixedly mounted to the tailstock. A retaining ring is supported by the 
connecting rod. The connector also includes a spring having a first end 
bearing against the retaining ring. A second end of the spring bears 
against the headstock to retain the drum between the headstock and the 
tailstock. The spring reacts against a force applied in the second 
direction of linear movement of the headstock when the tailstock is in the 
stop position to permit continued movement of the headstock in the second 
direction to release the drum from between the headstock and the 
tailstock. 
The headstock drive means of the first apparatus according to the present 
invention preferably includes a lead screw and a nut mechanism which is 
fixedly attached to the headstock. The nut mechanism is threadably 
attached to the lead screw. A motor rotates the lead screw to cause the 
nut mechanism to move linearly along the lead screw which causes the 
headstock to move linearly in the first and second opposite directions. In 
addition, the drum drive means preferably includes a motor. A home sensing 
switch preferably operates to turn off the drum motor and the lead screw 
motor when the headstock reaches a preset stop position. 
A preferred embodiment of the second apparatus according to the present 
invention includes a rotary wheel having a plurality of apertures 
circumferentially arranged on the rotary wheel. The rotary wheel is 
operable to select one of the plurality of apertures through which light 
is received and projected. The plurality of apertures are preferably 
rectangular-shaped apertures. The rotary wheel can be controlled manually 
by an operator to select a desired aperture. Alternatively, the rotary 
wheel is automatically controlled by a computer to select a desired 
aperture. 
The preferred embodiment of the second apparatus according to the present 
invention preferably includes a red filter, a blue filter, and a green 
filter. A first photo-multiplier tube receives light filtered by the red 
filter. A second photo-multiplier tube receives light from the blue 
filter. A third photo-multiplier tube receives light from the green 
filter. A first light splitter preferably splits the light transmitted 
through the aperture into a first light beam and a second light beam. A 
second light splitter preferably splits the second light beam into a third 
light beam and a fourth light beam. The first light beam preferably 
comprises substantially red spectral components and is projected to the 
red filter. The third light beam preferably comprises substantially blue 
spectral components and is projected to the blue filter. The fourth light 
beam preferably comprises substantially green spectral components and is 
projected to the green filter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A rotary image scanner according to the present invention in generally 
illustrated at 10, in FIGS. 1 and 2. The rotary scanner 10 scans an image 
source and provides voltage values representative of the image source to a 
digital signal processor which provides a digitized image having a high 
resolution and wide dynamic range. Rotary scanner 10 is substantially less 
expensive than existing rotary scanners that provide comparable 
resolutions and dynamic ranges. Like reference characters will be used for 
like elements throughout the drawings. 
Referring to FIGS. 1 and 2, the rotary scanner 10 comprises a drum mounting 
and positioning portion 12 and an optical bench portion 14. The drum 
mounting and positioning portion 12 includes a supporting frame 16. A 
linear way 18 is fixedly mounted on frame 16. Linear way 18 is a 
commercially available part which comprises a track rail 19, a slide unit 
22 and a slide unit 32. Slide units 22 and 32 are independently movably 
mounted on track rail 19. A headstock 20 is mounted on slide unit 22. 
Since slide unit 22 is movably mounted on linear way 18, headstock 20 
rides on linear way 18. Headstock 20 includes a drive plate portion 24 and 
a drive base portion 26 to form an L-shaped headstock. Drive base portion 
26 of headstock 20 is fixedly mounted to slide unit 22. An L-shaped 
tailstock 30 is fixedly mounted on slide unit 32 which is movably mounted 
on linear way 18 such that the L-shaped headstock 20 and the L-shaped 
tailstock 30 face inwardly towards each other with the tailstock being 
disposed on the linear way to the right of the headstock when viewing the 
image scanner from the front. The tailstock includes an end plate portion 
34 and an end base portion 36. The end base portion 36 of tailstock 30 is 
fixedly mounted to the slide unit 32. Two support posts 28 are fixedly 
attached into the lower portion of the drive plate 24 of headstock 20 to 
face inwardly towards the tailstock. Likewise, two support posts 38 are 
fixedly attached into the lower portion of end plate 34 of tailstock 30 to 
face inwardly towards headstock 20. 
As illustrated in detail in FIG. 3, track rail 19 is mounted on frame 16 
with screws 72. Headstock 20 is mounted to slide unit 22 of linear way 18 
with four screws 74 and tailstock 30 is mounted to slide unit 32 of linear 
way 18 with four screws 76. 
Referring back to FIGS. 1 and 2, a drum drive motor 40 is mounted into 
drive plate 24 of headstock 20. Art encoder 42 is attached to drum drive 
motor 40. When the rotary scanner 10 is operating to scan an image, a 
rotary drum 44 is seated between a tapered shaft 46 of motor 40 and a 
tapered receiving portion 48 of tailstock 30. Drum 44 includes scribe 
lines 50 indicating the outer boundaries of a selected inner portion of 
the drum. An image source 52 is mountable between scribe lines 50. Thus, 
when properly energized, drum drive motor 40 rotates drum 44 which rotates 
image source 52. 
The mounting and positioning portion 12 of image scanner 10 also includes a 
lead screw 54. Lead screw 54 is a commercially available part which 
comprises a nut mechanism 70. Nut mechanism 70 is threadably coupled 
around lead screw 54 and fixedly attached to drive base portion 26 of 
headstock 20 such that a rotation of lead screw 54 drives nut mechanism 70 
longitudinally along the lead screw which causes headstock 20 to ride 
linearly to the right or left along way 18. Lead screw 54 is mounted 
between a right side wall 56 of frame 16 and a bracket 58. Bracket 58 is 
fixedly mounted to frame 16 at the left end of the image scanner. A left 
end portion of the lead screw runs through the left side of bracket 58. A 
lead screw drive motor 62 is mounted on the left end of frame 16 on a 
mounting bracket 64. A drive shaft 66 of motor 62 is coupled to the left 
end portion of screw 54 with a mechanical coupler 68 to allow the lead 
screw drive motor 62 to rotate lead screw 54 counterclockwise and 
clockwise to move headstock 20 linearly along linear way 18. 
A more detailed view of the connection of drive base portion 26 of 
headstock 20 to nut mechanism 70 of lead screw 54 is illustrated in FIG. 
5. Nut mechanism 70 comprises a right nut end 82 and a left nut end 84 
which are threadably coupled around lead screw 54. An anti-back lash 
spring 86 has a first end connected to nut end 82 and a second end 
connected to nut end 84 to bias the nut end 84 and nut end 82 away from 
each other. By splitting the nut area in this way, end play in lead screw 
54 is substantially eliminated. Nut end 84 is bolted to drive base 26 of 
headstock 20 with bolts 88. Lead screw 54 passes through a rectangular 
opening 90 in drive base 26 of headstock 20 and a rectangular opening 92 
in end base 36 of tailstock 30. Headstock 20 linearly moves substantially 
parallel to the rotational axis of drum 44 along linear way 18 as nut 
mechanism 70 is driven longitudinally along lead screw 54. 
A connecting mechanism 80 connects tailstock 30 to headstock 20. Connecting 
mechanism 80 causes tailstock 30 to move linearly along way 18 in response 
to movement of the headstock caused by the rotation of lead screw 54. A 
more detailed discussion of the features of connection mechanism 80 are 
discussed below in reference to FIG. 5. Thus, when image scanner 10 is 
scanning image 52, drum drive motor 40 rotates drum 44 and lead screw 
drive motor 62 rotates lead screw 54 to cause headstock 20 to move 
linearly to the right and left along linear way 18 which causes tailstock 
30 to move correspondingly to the left or right depending on the rotation 
direction of lead screw 54. This linear movement of headstock 20 and 
tailstock 30 along linear way 18 is in a line substantially parallel to 
the rotational axis of rotary drum 44. Because drum 44 is seated between 
headstock 20 and tailstock 30, drum 44 is driven longitudinally along a 
line substantially parallel to the rotational axis of the drum. 
Referring to FIG. 4A, a light source or a lamp 100 provides a high 
intensity beam for illuminating portions of image source 52 on the drum 
44. The light from light source 100 travels through a fiber optic cable 
102. A tube 104 is attached to frame wall 56 (see FIG. 2) and extends 
inwardly from wall 56. Fiber optic cable 102 is mounted to tube 104 with a 
set screw. A plate 108 fits inside of tube 104 and is held with two nylon 
tipped set screws. A mirror 106 receives the light transmitted by fiber 
optic cable 102. Mirror 106 is mounted to plate 108. Mirror 106 is 
positioned at a 45.degree. angle to the path of light provided by fiber 
optic cable 102. A lens plate 110 is attached to and extends inwardly from 
plate 108. A source lens 112 has a threaded portion 114 which threads into 
a threaded opening 116 of lens plate 110. Mirror 106 receives and reflects 
the light from fiber optic cable 102 through the source lens 112. Source 
lens 112 receives the light reflected by mirror 106 and projects the light 
through transparency image source 52 to a receiving lens 150. Receiving 
lens 150 is contained in optical bench 14 which is discussed below. In 
this way, light source 100, fiber optic cable 102, mirror 106, and source 
lens, 112 provide a light source to illuminate the portion of image 52 
which is rotated and longitudinally positioned into the path of the light 
projected by source lens 112. Receiving lens 150 receives the light 
transmitted through transparency image source 52 to permit optical bench 
14 to analyze the image. A scrambler rod 120 is attached to the end of 
fiber optic cable 102 to provide relatively uniform distribution of light 
over the end face of fiber optic cable 102. In this way, scrambler rod 120 
avoids excessive hot spots. 
The above description of the present invention with reference to FIG. 4A 
describes and illustrates a rotary drum scanner configured to scan a 
transparent image source 52. A reflective image is also easily scanned by 
image scanner 10. A reflective configuration of image scanner 10 is 
illustrated in FIG. 4B. A light source 130 provides a high intensity beam 
for illuminating portions of a reflective image source 53 mounted on the 
drum 44. The light from light source 130 travels through a fiber optic 
cable 132 which feeds light into an illuminating ring 134. Illuminating 
ring 134 encloses several illuminating lenses 136 which project the light 
from fiber optic cable 132 at a 45.degree. angle to the lens axis onto a 
spot 138 on reflective image 53, which reflects the light to receiver lens 
150. Thus, in the reflective configuration, light illuminates the outside 
of drum 44 instead of the inside of drum 44 to allow light to be reflected 
off reflective image 53 to the receiver lens 150. 
In reference to FIG. 2, optical bench 14 comprises receiver lens 150 to 
receive the light transmitted through transparent image source 52 or 
reflected off of reflective image source 53. Receiver lens 150 extends 
through an opening 152 of a housing 154 of optical bench 14 and threads 
into a bracket 118. Receiver lens 150 focuses light transmitted through 
transparent image source 52 or reflected from reflective image source 53 
to a directing mirror 156. Directing mirror 156 receives and reflects the 
light focused by receiver lens 150 to an aperture wheel 157 and through a 
selectable aperture 158 which is disposed in the aperture wheel. The light 
transmitted through aperture 158 is received by an optical block 160. 
Optical block 160 comprises a substantially opaque housing 162. A condenser 
lens 164 is mounted in an opening 166 disposed in a side wall 168 of 
opaque housing 162. Condenser lens 164 receives and projects the light 
transmitted through aperture 158. A light splitter 170 is mounted inside 
of opaque housing 162 to receive the light projected by condenser lens 
164. Light splitter 170 splits the light projected by condenser lens 164 
into a light beam 172 and a light beam 174. A light splitter 176 splits 
light beam 174 into a light beam 178 and a light beam 180. A red filter 
182 receives light beam 172 and filters selected portions of the light 
spectrum from light beam 172 to provide red light. Red filter 182 is 
mounted in an opening 184 disposed in a right side wall 186 of opaque 
housing 162. A blue filter 188 receives light beam 178 and filters 
selected portions of the light spectrum from light beam 178 to provide 
blue light. Blue filter 188 is mounted in an opening 190 disposed in right 
side wall 186. A green filter 192 receives light beam 180 and filters 
selected portions of the light spectrum from light beam 180 to provide 
green light. Green filter 192 is mounted in an opening 194 disposed in a 
front wall 196 of opaque housing 162. 
Light splitter 170 operates by transmitting the red spectral components of 
light received from condenser lens 164 and reflecting the remaining 
spectral components from the light from condenser lens 164. Thus, red 
filter 182 receives substantially red spectral components of light. Light 
splitter 176 operates by transmitting the green spectral components of 
light from light beam 174 and reflecting the remaining spectral components 
from light beam 174 which substantially comprise blue spectral components. 
Thus, blue filter 188 receives substantially blue light components from 
light beam 178. Green filter 192 receives substantially green spectral 
components of light from light beam 180. 
A photo-multiplier tube 198 receives the red light filtered by red filter 
182. A photo-multiplier tube 200 receives the blue light from blue filter 
188. A, photo-multiplier tube 202 receives the green light filtered by 
green filter 194. The photo-multiplier tubes 198, 200, and 202 provide 
respective voltage levels indicating the relative intensity of the red, 
blue, and green light that has been transmitted from the selected portion 
of image 52 or image 53 which is illuminated during one illumination 
interval by the light source. The voltage levels provided by the 
photo-multiplier tubes are provided to processing and control board 300. 
The processing and control board 300 processes the voltage levels provided 
by photo-multiplier tubes 198, 200, and 202 to provide a digitized image 
of the image source. 
The opaque housing of optical box 160 substantially eliminates light noise 
in the red, blue, and green light provided to photo-multiplier tubes 198, 
200, and 202. Previous designs of image scanners did not enclose the 
condenser lens, the light splitters, and the light filters in an optical 
box such as optical box 160. The opaque housing 162, substantially 
eliminates light noise which allows the design of the image scanner to be 
accomplished at a reduced price and still provide the same resolution and 
dynamic range in the resulting digitized image provided by the image 
scanner. The opaque housing 162 is preferably made from an extruded and 
molded plastic such as an acetal. Such an acetal is provided by EI Dupont 
under the commercial name of Delrin. The Delrin should be black or any 
substantially opaque color so the outside light will not produce light 
noise into the light provided to the photo-multiplier tubes. In this way, 
photo-multiplier tube 198 provides an accurate voltage level indicating 
the intensity of red light that has been transmitted from the selected 
portion of image 52 or image 53 which is illuminated during one 
illumination interval. Correspondingly, photo-multiplier tube 200 provides 
an accurate voltage level indicating the intensity of blue light 
transmitted during this same illumination interval and photo-multiplier 
tube 202 provides an accurate voltage level indicating the intensity of 
green light transmitted from the image source during the same illumination 
interval. 
An auto-focusing mechanism 210 is attached to receiving lens 150. 
Auto-focusing mechanism 210 translates lens 150 toward or away from drum 
44 to thereby change the focal position of lens 150. Auto-focus mechanism 
210 is a standard motorized auto-focusing mechanism. 
Aperture wheel 157 has a series of apertures 158 which are selectably 
brought into the path of the light reflected by directing mirror 156. 
Apertures 158 define the size of the image that is passed to the optical 
block 160. The size of the image being passed to optical block 160 defines 
the resolution of the image. A motor 212 selectively positions the 
appropriate aperture 158 into the light reflected by mirror 156. 
FIG. 6 illustrates the disposition of the apertures 158 circumferentially 
arranged on the aperture wheel 157. As illustrated, apertures 158 are 
rectangular-shaped apertures. The width of the rectangular apertures is 
indicated by arrows 214 at the longest aperture. In the preferred 
embodiment illustrated in FIG. 6, the apertures are all a width of 0.0025 
inches, but the apertures vary in length. As indicated by arrows 216, the 
longest aperture is 0.05 inches. Apertures decrease in size in the 
counter-clockwise direction on wheel 157. Lengths of the apertures in this 
embodiment are as follows from the shortest to the longest aperture 
length: 
Apertures with a tolerance of .+-.0.001 inches 
0.0500 inches 
0.0400 inches 
0.0300 inches 
0.0250 inches 
0.0200 inches 
0.0150 inches 
Apertures with tolerances of .+-.0.0005 inches 
0.0125 inches 
0.0100 inches 
0.0075 inches 
0.0050 inches 
0.0025 inches 
With these varying aperture lengths and with a variation of the rotation of 
drum 44, resolutions are provided varying from 4000 DPI when the shortest 
aperture of 0.0025.times.0.0025 inches is selected to 200 DPI when the 
longest aperture of 0.05.times.0.0025 inches is selected. 
Drum drive motor 40 typically operates in range from approximately 355 RPM 
to approximately 1745 RPM. Lead screw drive motor 62 drives the headstock 
and tailstock in increments as small as 0.00025 inches. A 6 inch.times.6 
inch image 52 is scanned in approximately 1.38 minutes at a resolution of 
400 DPI. Accordingly, as the resolution gets higher, the scanning time 
increases such that an 6.times.6 inch image is scanned in approximately 
4.23 minutes at 1000 DPI. Similarly, as the resolution decreases, the scan 
time also decreases. 
The rectangular apertures illustrated in FIG. 6 provide a convolution of 
the input image. In previous image scanners, the apertures were designed 
to have a symmetrical shape, such as a circular or square shape, as 
compared to the rectangular ones in the present invention. Symmetrical 
apertures average the input signal more than the rectangular apertures of 
the present invention which tends to minimize the noise but blurs the 
image. The rectangular apertures of the present invention do not tend to 
blur the image and provide a closer representation of the input light 
signal. 
FIG. 5 illustrates in detail connecting mechanism 80. Connecting mechanism 
80 includes a front connecting mechanism 246 and a rear connecting 
mechanism 248 which are substantially similar. Front connecting mechanism 
246 comprises a front connecting rod 250 having an end 252 fixedly mounted 
into end base portion 36 of tailstock 30. Connecting rod 250 passes 
through a cylindrical opening 254 of drive base portion 26 of headstock 
20. Cylindrical opening 254 has a diameter slightly larger than the 
diameter of connecting rod 250 to enable connecting rod 250 to freely move 
through opening 254. A left end 256 of connecting rod 250 is disposed in a 
cylindrical opening 258 of drive base portion 26 of headstock 20. 
Cylindrical opening 258 has a diameter substantially larger than the 
diameter of cylindrical opening 254. A retaining ring 260 fits into a 
groove of connecting rod 250 adjacent to the right side of opening 254. 
Retaining ring 260 has a diameter larger than the diameter of opening 254 
so that the movement of tailstock 30 relative to headstock 20 is limited 
when drum 44 is not installed in the image scanner. A spring 262 has a 
left end 264 pressing against a retaining ring 263 which fits into a 
groove of connecting rod 250 adjacent to end 256 of the connecting rod. 
Spring 262 has a right end 266 pressing against a washer or bushing 268. 
Washer 268 has an outer diameter which is larger than the diameter of 
opening 254 and an inner diameter slightly larger than the diameter of 
connecting rod 250 so that when headstock 20 is driven linearly to the 
left along way 18, a force is applied to washer 268 to compress spring 
262. When connecting mechanism 80 is assembled, spring 262 is compressed 
between retaining ring 263 and washer 268. When drum 44 is installed 
between headstock 20 and tailstock 30, spring 262 is further compressed to 
retain drum 44. 
Rear connecting mechanism 248 comprises a rear connecting rod 270 having an 
end 272 fixedly mounted into end base portion 36 of tailstock 30. 
Connecting rod 270 passes through a cylindrical opening 274 of drive base 
portion 26 of headstock 20. Cylindrical opening 274 has a diameter 
slightly larger than the diameter of connecting rod 270 to enable 
connecting rod 270 to freely move through opening 274. A left end 276 of 
connecting rod 270 is disposed in a cylindrical opening 278 of drive base 
portion 26 of headstock 20. Cylindrical opening 278 has a diameter 
substantially larger than the diameter of cylindrical opening 274. A 
retaining ring 280 fits into a groove of connecting rod 270 adjacent to 
the right side of opening 274. Retaining ring 280 has a diameter larger 
than the diameter of opening 274 so that the movement of tailstock 30 
relative to headstock 20 is limited when drum 44 is not installed in the 
image scanner. A spring 282 has a left end 284 pressing against a 
retaining ring 283 which fits into a groove of connecting rod 270 adjacent 
to end 276 of the connecting rod. Spring 282 has a right end 286 pressing 
against a washer or bushing 288. Washer 288 has an outer diameter which is 
larger than the diameter of opening 274 and an inner diameter slightly 
larger than the diameter of connecting rod 270 so that when headstock 20 
is driven linearly to the left along way 18, a force is applied to washer 
288 to compress spring 282. When connecting mechanism 80 is assembled 
spring 282 is compressed between retaining ring 283 and washer 288. When 
drum 44 is installed between headstock 120 and tailstock 30, spring 282 is 
further compressed to retain drum 44. 
Thus, front connecting mechanism 246 and rear connecting mechanism 248 work 
in conjunction to retain drum 44 and to transfer the force from headstock 
20 to tailstock 30 to drive tailstock 30 to the right as headstock 20 
moves to the right linearly along linear way 18. As headstock 20 is driven 
linearly to the left, tailstock 30 is also pulled linearly to the left 
because the tensions of springs 262 and 282 are such that the springs do 
not substantially compress in response to the force required to pull 
tailstock 30 to the left. A stop block or home stop 292 is fixedly 
attached to frame 16 at a selected home stop position to stop the 
tailstock 30 from moving in a left direction linearly along linear way 18 
once tailstock 30 has reached the home stop position. The height of stop 
block 292 extends higher than the bottom of end base 36 of tailstock 30 to 
impede the left linear motion of tailstock 30. When tailstock 30 is 
stopped by stop block 292, the nut mechanism 70 is still driven to the 
left longitudinally along lead screw 54 by the lead screw drive motor 62 
which drives headstock 20 to the left and causes headstock 20 to apply a 
longitudinal force on washers 268 and 288 to compress springs 262 and 282 
against retaining rings 263 and 283. Thus, headstock 20 moves linearly to 
the left while tailstock 30 is stopped in the selected home stop position. 
Referring to FIG. 2, a home sensor switch 294 senses when headstock 20 has 
reached a preset home position and accordingly shuts off drum drive motor 
40 and lead screw drive motor 62. As headstock 20 moves to the left away 
from tailstock 30, the distance between drive plate portion 24 of 
headstock 20 and end plate portion 34 of tail stock increases which 
disengages drum 44 from between the tailstock and the headstock. Thus, 
home sensor switch 294 operates to shut off the drive motors so that the 
tailstock stops before the tailstock contacts stop block 292 to prevent 
the drum 44 from being disengaged prematurely from between the tailstock 
and the headstock. In the preferred embodiment of image scanner 10, the 
preset home position is set to shut off drum drive motor 40 and lead screw 
drive motor 62 to stop tailstock 30 a few 1/1000ths of an inch to the 
right of stop block 292. 
A processing and control board 300 controls drum drive motor 40 via lines 
indicated at 302 and controls lead screw drive motor 62 through 
transmission of signals along lines indicated at 304. A user interface 301 
provides an interface between an operator and processing and control board 
300. User interface 301 can be implemented in a computer having a display 
and a keyboard. Thus, once both the lead screw drive motor 62 and drum 
drive motor 40 have been shut off by home sensor switch 294, processing 
and control board 300, operating under the control of an operator, 
energizes lead screw drive motor 62 to pull headstock 20 further away from 
tailstock 30 to disengage drum 44 from between tailstock 30 and headstock 
20. When drum 44 is disengaged, drum 44 rests on the two drum support 
posts 28 and the two drum support posts 38. Once headstock 20 has been 
driven to a sufficient distance to the left, processing and control board 
300 stops the movement of headstock 20. In this way, drum 44 can be easily 
removed to replace image 52. 
When an operator wants to reinsert drum 44 into the image scanner, the 
operator simply places the drum on support posts 28 and 38, pushes a "V" 
groove on drum 44 plate onto a pin on drive shaft 46, and then goes back 
to user interface 301 and types the appropriate command to move headstock 
20 back to the right to seat drum 44 between drive shaft 46 of motor 40 
and the tapered receiving portion 48 of tailstock 30. A limit switch or 
drum in place switch 296 is positioned to detect that drum 44 is properly 
seated between headstock 20 and tailstock 30. Limit switch 296 operates to 
control drum drive motor 40 and prevents drive motor 40 from being 
energized to rotate drum 44 until drum 44 is properly seated. 
Thus, as compared to previous designs, the quick release nature of 
connecting mechanism 80 permits an operator to easily remove and replace 
drum 44 when a new image needs to be scanned. Because drum drive motor 40 
and lead screw drive motor 62 are controlled by processing and control 
board 300, the operator does not need to spend time at the image scanner 
itself to unload and load an image onto drum 44. In addition, the complex 
alignment procedures typically required to insert the drum are no longer 
needed because the exact positioning of drum 44 is known to be at the home 
stop position when the scanning process begins. 
In addition to controlling the drive motors, processing and control board 
300 receives signals from shaft encoder 42 indicating the instantaneous 
position of the rotation of drum 44 via the lines indicated at 302. 
Processing and control board 300 also controls motor 212 to control the 
selection of apertures 158 on aperture wheel 157 through signals provided 
on lines 306. Processing and control board 300 can identify the distance 
between apertures to provide further control of motor 212 in the selection 
of apertures. In this way, when the image scanner is in operation, the 
operator can control the desired resolution of the digital image from user 
interface 301 instead of being at the image scanner. In addition, 
processing and control board 300 provides many other valuable functions. 
For example, if auto-focus 210 fails to focus receiver lens 150 properly, 
the processing and control board prompts the operator via user interface 
301 to manually focus receiver lens 150 to provide the proper focus. 
Image scanner 10, as described above, provides a high resolution and wide 
dynamic range and can be configured to scan reflective or transmissive 
image sources. Image scanner 10 is computer controlled by processing and 
control board 300 and the operator needs to spend little time at the image 
scanner itself. Instead, the operator can be setting scan parameters at 
the computer display and keyboard. 
Because the headstock and tailstock of image scanner 10 ride on a singular 
linear way 18, complex alignment procedures required in the manufacturing 
of a typical rotary image scanner are eliminated. Typically, the tailstock 
and headstock ride on two rails instead of one linear way which 
accordingly causes alignment problems in the positioning of the two rails. 
Therefore, complicated alignment procedures are needed to align the two 
rails when manufacturing a typical rotary image scanner. Since these 
alignment procedures are not performed in the manufacturing of image 
scanner 10, image scanner 10 is much less expense to manufacture than 
typical rotary image scanners. 
In addition, the optical block with its opaque housing 162, allows image 
scanner 10 to be constructed at a significantly lower price than existing 
scanners providing the same high resolution and wide dynamic ranges of 
image scanner 10. Moreover, the quick releasing nature of connecting 
mechanism 80 and the driving mechanism of lead screw 54 and lead screw 
drive motor 62 provide further enhancements to the image scanner to 
provide a cost effective, yet high quality design. Moreover, the easy 
removal of drum 44 allows images to be scanned by operators of less 
technical skill and requires less time in the mounting of a new source 
image. 
Although the present invention has been described with reference to 
preferred embodiments, workers skilled in the art will recognize that 
changes may be made in form and detail without departing from the spirit 
and scope of the invention.