Digitizing scanner

• US 6,606,171 B1
• Filed: 10/09/1997
• Issued: 08/12/2003
• Est. Priority Date: 10/09/1997
• Status: Expired due to Fees

• Current Assignee: Howtek Incorporated (iCAD Incorporated)
• Original Assignee: Howtek Incorporated (iCAD Incorporated)
• Inventors: Fernald, Mark R., Renk, Jeffrey D., Lehman, Richard F., Winey, Calvin M.
• Primary Examiner(s): Lee, Cheukfan
• Application Number:
  US08/948,108
• Time in Patent Office: 2,133 Days
• Field of Search: 358/475, 358/509, 358/496, 358/483, 358/474, 358/487, 358/506, 250/205, 250/208.1, 250/234, 250/578.1, 250/239, 362/800
• US Class Current: 358/475
• CPC Class Codes: H04N 1/00002 Diagnosis, testing or measuring; Detecting, analysing or monitoring not otherwise provided for error detection, error correction or monitoring in digital computers or digital computer components G06F11/00
• CPC Class Codes: H04N 1/00013 Reading apparatus
• CPC Class Codes: H04N 1/00037 Detecting, i.e. determining the occurrence of a predetermined state H04N1/00031 takes precedence
• CPC Class Codes: H04N 1/00053 out of service, i.e. outside of normal operation
• CPC Class Codes: H04N 1/00063 using at least a part of the apparatus itself, e.g. self-testing
• CPC Class Codes: H04N 1/00087 Setting or calibrating picture signal circuits H04N1/40
• CPC Class Codes: H04N 1/02815 Means for illuminating the original, not specific to a particular type of pick-up head
• CPC Class Codes: H04N 1/0284 in combination with a light integrating, concentrating or diffusing cavity
• CPC Class Codes: H04N 1/02885 Means for compensating spatially uneven illumination, e.g. an aperture arrangement
• CPC Class Codes: H04N 1/121 Feeding arrangements transporting sheets to or from the scanning position H04N1/0057; control or error compensation of sub-scanning velocity H04N1/0473
• CPC Class Codes: H04N 1/191 the array comprising a one-dimensional array , or a combination of one-dimensional arrays, or a substantially one-dimensional array, e.g. an array of staggered elements
• CPC Class Codes: H04N 1/40056 Circuits for driving or energising particular reading heads or original illumination means H04N1/401, H04N1/407 take precedence
• CPC Class Codes: H04N 1/40068 Modification of image resolution, i.e. determining the values of picture elements at new relative positions H04N1/3935 takes precedence
• CPC Class Codes: H04N 1/401 Compensating positionally unequal response of the pick-up or reproducing head H04N1/403 takes precedence
• CPC Class Codes: H04N 2201/0412 Scanning X-ray films

Abstract

A digitizing scanner particularly for scanning transparent films such as X-rays provides an improved illuminator for transmitting light through the film. The illuminator defines a line array of a plurality of individually calibrated and controlled LEDs. The LEDs are calibrated by determining their relative points of projection on a CCD camera array. The camera array scans the LEDs and adjusts them individually to produce a predetermined illumination pattern from the group. The adjustment occurs over a plurality of cycles that address cross-talk between LEDs in the array. The camera includes anti-reflection elements to minimize bounce-back of image light and noise suppression circuitry to reduce low-level signal noise. A central processing unit, interconnected with the camera assembly includes a pixel averager to reduce the inherent resolution of the CCD to a desired level and to attenuate further noise. The scanner can include an illuminator for illuminating a scannable opaque bar-code strip and size-measurement circuitry for determining the relative size and location of the scanned image.

Claims

1. An illuminator for a digitizing scanner a scanning camera interconnected with a central processing unit, the scanning camera defining discrete pixels arranged in a widthwise direction, the pixels being adapted to acquire an image of a transparent film passing through a widthwise field of view of the scanning camera, the illuminator comprising:

a plurality of light sources, each being a light emitting diode and each being individually arranged in a line across the widthwise field of view so as to face a first side of the transparent film opposite to a second side of the transparent film arranged to face the scanning camera;

a plurality of controllers each interconnected with respective of the plurality of individual light sources, each of the controllers providing a variable driving power to a respective of the plurality of individual light sources; and

wherein the central processing unit is constructed and arranged to instruct the controllers to respectively change the driving power to each of the plurality of the light sources in response to a reading of intensity of predetermined of the pixels that are mapped to each of the plurality of light sources so that the scanning camera receives a predetermined illumination pattern across the widthwise field of view and wherein the controllers are adapted to respectively change the driving power during a calibration procedure that occurs with respect to operation of the digitizing scanner after startup of operation of the scanner.

2. The illuminator as set forth in claim 1 further comprising a housing for enclosing the light sources and a diffuser window disposed between the light sources and the scanning camera.

3. The illuminator as set forth in claim 2 further comprising a pair of walls approximately parallel to each other in the widthwise direction.

4. The illuminator as set forth in claim 1 wherein the controllers provide a plurality of current regulating circuits.

5. The illuminator as set forth in claim 4 further comprising an intensity controller interconnected with each of the plurality of controllers for varying a primary driving power to each of the plurality of light sources, the intensity controller being responsive to the central processing unit based upon a predetermined maximum level of light exposure by each of the plurality of light sources at the scanning camera.

6. The illuminator as set forth in claim 5 further comprising a photodetector for detecting an output of a predetermined light source of the plurality of light sources, the photodetector being constructed and arranged to produce a reference signal, the photodetector being interconnected with the intensity controller whereby the predetermined maximum level of light exposure is set and maintained based upon the reference signal.

7. An illuminator for a digitizing scanner having a widthwise field of view, a scanning camera interconnected with a central processing unit comprising:

a plurality of light sources each individually arranged in a line across the widthwise field of view;

a plurality of controllers, each interconnected with respective of the plurality of individual light sources, each of the controllers providing a variable driving power to a respective of the plurality of individual light sources;

wherein the central processing unit is constructed and arranged to instruct the controllers to respectively change the driving power to each of the plurality of the light sources so that the scanning camera receives a predetermined illumination pattern across the widthwise field of view;

wherein the light sources comprise a plurality of light emitting diodes and wherein the controllers provide a plurality of current regulating circuits;

an intensity controller interconnected with each of the plurality of controllers for varying a primary driving power to each of the plurality of light sources, the intensity controller being responsive to the central processing unit based upon a predetermined maximum level of light exposure by each of the plurality of light sources at the scanning camera;

a photodetector for detecting an output of a predetermined light source of the plurality of light sources, the photodetector being constructed and arranged to produce a reference signal, the photodetector being interconnected with the intensity controller whereby the predetermined maximum level of light exposure is set and maintained based upon the reference signal; and

wherein each of the plurality of controllers comprises a digital/analog converter and a common emitter buffer amplifier interconnected with one of the plurality of light sources, the analog/digital converter being interconnected with and receiving a digital control signal from the central processing unit and interconnected with and receiving the reference signal, the digital/analog converter having an output interconnected with and controlling the common emitter buffer amplifier whereby the driving power of the one of the plurality of light sources is varied.

8. A method for calibrating an illumination assembly in a digitizing scanner having a camera defining a widthwise line of photosensitive pixels, the camera being adapted to scan widthwise lines of an image in a lengthwise direction and a controller for controlling the illumination assembly and the camera, the method comprising the steps of:

(a) during a calibration procedure that occurs with respect to operation of the digitizing scanner after startup of operation of the scanner, incrementally activating predetermined light sources of a plurality of light sources, each of the plurality of light sources comprising a discrete light emitting diode, being arranged in a widthwise line to each project an illumination light therefrom so as to transmit the light to a side of a film being scanned toward the camera which faces an opposing side of the film, the step of incrementally activating including activating light sources that are each spaced apart by a predetermined number of inactivated light sources until all light sources have been activated;

(b) identifying pixels on the camera activated by each of the plurality of light sources and mapping each of the activated pixels to a predetermined of the plurality of light sources;

(c) activating all of the plurality of light sources at a predetermined power level and deriving an intensity signal based upon projected light from the light sources at the camera;

(d) comparing an intensity value for each of the pixels identified in the step of identifying with a predetermined reference intensity value; and

(e) changing a power level of each of the plurality of light sources so that a measured exposure value of respective pixels is closer to a desired exposure value based upon readings of intensity at identified pixels mapped to each of the predetermined of the plurality of light sources.

9. The method as set forth in claim 8 further comprising repeating each of steps (c), (d) and (e) a predetermined number of times, whereby the measured intensity values of each of the respective pixels is made closer to a desired exposure characteristic.

10. The method as set forth in claim 9 wherein the step of activating all of the plurality of light sources includes controlling a driving power input to all of the light sources so that each of the light sources has an intensity less than a predetermined maximum intensity.

11. The method as set forth in claim 8 further comprising measuring an output intensity of one of the plurality of light sources to generate the reference intensity value.

12. A method for controlling a width of an illumination line oriented in a widthwise direction and generated by an illumination assembly in a digitizing scanner having a camera assembly for receiving light from a scanned sheet that moves relative to the camera assembly in a lengthwise direction transverse to the widthwise direction, the method comprising the steps of:

providing a plurality of light sources oriented in a line along the widthwise direction each of the light sources being directed to provide illumination light that is centered at a predetermined position along a widthwise line of the sheet;

individually addressing selected of the plurality of light sources to enable the selected of the plurality of light sources to be deactivated; and

controlling the step of individually addressing so that the selected of the plurality of light sources are light sources that provide illumination light that is centered with respect to portions of the widthwise line that are remote from a region of the sheet desired to be scanned.

13. The method as set forth in claim 12 wherein the step of controlling includes identifying widthwise edges of the sheet and defining the portions of the widthwise line that are remote based upon widthwise positions of the widthwise edges.

14. The method as set forth in claim 13 wherein the step of identifying includes scanning the sheet to determine widthwise locations of change in scanned density between a free space density and a density greater than free space and the step of defining includes deriving the widthwise positions of the widthwise edges based the widthwise locations of the change in scanned density.

15. The method as set forth in claim 13 wherein the step of controlling includes identifying widthwise limits of a region of interest of an image on the sheet and defining the portions of the widthwise line that are remote based upon widthwise positions of the widthwise limits.

16. An illuminator for a digitizing scanner having a widthwise field of view, a scanning camera interconnected with a central processing unit comprising:

a plurality of light sources, each individually arranged in a line across the widthwise field of view;

a plurality of controllers, each interconnected with respective of the plurality of individual light sources, each of the controllers providing a variable driving power to a respective of the plurality of individual light sources;

wherein the central processing unit is constructed and arranged to instruct the controllers to respectively change the driving power to each of the plurality of the light sources so that the scanning camera receives a predetermined illumination pattern across the widthwise field of view;

a housing for enclosing the light sources and a diffuser window disposed between the light sources and the scanning camera; and

wherein the wall comprise tapered walls, the tapered walls tapering between a first spacing apart adjacent the diffuser window and a second wider spacing adjacent the light sources, the walls including a reflective surface thereon.