Sensor assembly providing gray scale and color for an optical image scanner

• US 5,773,814 A
• Filed: 09/22/1995
• Issued: 06/30/1998
• Est. Priority Date: 08/23/1994
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Gennetten, Kenneth D., Phillips, Wayne G., Bohn, David D., Hubel, Paul M.
• Primary Examiner(s): Allen, Stephone
• Application Number:
  US08/532,378
• Time in Patent Office: 1,012 Days
• Field of Search: 250/208.1, 250/226, 348/33, 348/342, 348/254, 348/273, 348/276, 382/58, 382/65, 358/505, 358/512, 358/513, 358/514, 358/515
• US Class Current: 250/208.1
• CPC Class Codes: H04N 1/00795 Reading arrangements details of scanning heads H04N1/024; scanning arrangements therefor H04N1/04
• CPC Class Codes: H04N 1/486 with separate detectors, each detector being used for one specific colour component

Abstract

A sensor assembly and an optical image color scanner using the sensor assembly. The sensor assembly is of the type having three separate rows of optical sensors. Two of the three sensor rows have color filters and one is unfiltered (receptive to white light). For gray scale scanning, only the unfiltered (white) sensor row is used, thereby maximizing the speed of gray scale scanning. For color scanning, three color values are computed as a linear transformation of values from the two filtered and one unfiltered values. The linear transformation may be as simple as subtracting signals from the two filtered sensor rows from the signal from the unfiltered (white) sensor row. For color scanning, memory buffers are required for two of the three sensor output signals. For highest accuracy in color scanning, the exposure time for the white sensor row is reduced relative to the exposure time for the two filtered sensor rows. An optional white channel bandpass filter (passing all wavelengths within the human visual range and rejecting wavelengths outside the human visual range) provides improved accuracy if the light source has significant wavelengths outside the human visual range.

Claims

1. A sensor assembly for an optical image scanner comprising:

a first row of sensor elements, each sensor element in the first row receiving light that is unfiltered and having an analog output signal proportional to the received light; and

a plurality of additional rows of sensor elements, each sensor element in the additional rows receiving light that is filtered and having an analog output signal proportional to the received light.

2. A sensor assembly as in claim 1 further comprising:

a first analog-to-digital converter, receiving the analog output signals from the first row of sensor elements and outputting first numerical values representing an amplitude of the received analog signals;

a plurality of second analog-to-digital converters, each receiving the analog output signal from one of the additional rows of sensor elements and outputting second numerical values representing an amplitude of the received analog signals; and

an arithmetic unit, sequentially receiving one of the first numerical values and the second numerical values and performing a linear transformation on the received values.

3. A sensor assembly as in claim 2 further comprising:

a first memory buffer, receiving the first numerical values and outputting the received numerical values on a first-in first-out basis to the arithmetic unit; and

a plurality of second memory buffers, one second memory buffer for each row of the plurality of additional rows of sensor elements, each second memory buffer receiving the second numerical values from its corresponding row of sensor elements and outputting the received second numerical values on a first-in first-out basis to the arithmetic unit.

4. An optical image scanner comprising:

a sensor assembly, receiving light from an image, the sensor assembly further comprising;

a first row of sensor elements, each sensor element in the first row of sensor elements receiving light from the image that is unfiltered and having an analog output signal proportional to the received light;

a plurality of light filters; and

a plurality of additional rows of sensor elements, each additional row of sensor elements having one corresponding light filter in the plurality of light filters, the light filters disposed such that each sensor element in each additional row of sensor elements receives light from the image that is filtered by the one corresponding light filter, each sensor element in each additional row of sensor elements having an analog output signal proportional to the received light.

5. The optical image scanner of claim 4 further comprising:

a first analog-to-digital converter, receiving the analog signals from the first row of sensor elements and outputting first numerical values representing amplitudes of the received analog signals;

a plurality of additional analog-to-digital converters, each receiving the analog signals from one of the additional rows of sensor elements and

outputting numerical values representing amplitudes of the received analog signals; and

an arithmetic unit, receiving the first numerical values and the additional numerical values and performing a linear transformation on the received values.

6. The optical image scanner of claim 5 further comprising:

a first memory buffer for the first row of sensor elements, receiving the first numerical values and outputting the received first numerical values on a first-in first-out basis to the arithmetic unit; and

a plurality of additional memory buffers having a one to one correspondence with the plurality of additional rows of sensor elements, each receiving the additional numerical values from the corresponding additional row of sensor elements and outputting the received second numerical values on a first-in first-out basis to the arithmetic unit.

7. A sensor assembly for an optical image scanner comprising:

a first row of sensor elements, each sensor element in the first row of sensor elements receiving light that is filtered by a bandpass light filter passing substantially all the human visible light spectrum and having an analog output signal proportional to the received light; and

a plurality of additional rows of sensor elements, each sensor element in each additional row of sensor elements receiving light that is filtered by a light filter passing substantially less than the human visible light spectrum and having an analog output signal proportional to the received light.

8. A sensor assembly as in claim 7 further comprising:

a first analog-to-digital converter, receiving analog signals from the first row of sensor elements and outputting first numerical values representing amplitudes of the received analog signals;

a plurality of additional analog-to-digital converters, each receiving analog signals from one of the additional rows of sensor elements and outputting additional numerical values representing amplitudes of the received analog signals; and

an arithmetic unit, receiving the first numerical values and the additional numerical values and performing a linear transformation on the received values.

9. A sensor assembly as in claim 8 further comprising:

a first memory buffer, receiving the first numerical values and outputting the received first numerical values on a first-in first-out basis to the arithmetic unit; and

a plurality of additional memory buffers, one additional memory buffer for each additional row of sensor elements, each additional memory buffer receiving the second numerical values from its corresponding additional row of sensor elements and outputting the received second numerical values on a first-in first-out basis to the arithmetic unit.

10. An optical image scanner comprising:

a sensor assembly, receiving light from an image, the sensor assembly further comprising;

a first row of sensor elements, each sensor element in the first row of sensor elements receiving light from the image that is filtered by a first bandpass light filter passing substantially all the human visible light spectrum and having an analog output signal proportional to the received light;

a plurality of additional light filters, each additional light filter passing substantially less than the human visible light spectrum; and

a plurality of additional rows of sensor elements, each additional row of sensor elements having one corresponding light filter in the plurality of additional light filters, the additional light filters disposed such that each sensor element in each additional row of sensor elements receives light from the image that is filtered by the one corresponding additional light filter, each sensor element in each additional row of sensor elements having an analog output signal proportional to the received light.

11. The optical image scanner of claim 10 further comprising:

a first analog-to-digital converter, receiving analog signals from the first row of sensor elements and outputting first numerical values representing amplitudes of the received analog signals;

a plurality of additional analog-to-digital converters, each receiving analog signals from the sensor elements in each additional row of sensor elements and outputting second numerical values representing amplitudes of the received analog signals; and

an arithmetic unit, receiving the first numerical values and the additional numerical values and performing a linear transformation on the received values.

12. The optical image scanner of claim 11 further comprising:

a first memory buffer for the first row of sensor elements, receiving the first numerical values and outputting the received first numerical values on a first-in first-out basis to the arithmetic unit; and

a plurality of additional memory buffers having a one to one correspondence with the plurality of additional rows of sensor elements, each receiving the additional numerical values from the corresponding additional row of sensor elements and outputting the received additional numerical values on a first-in first-out basis to the arithmetic unit.

13. In an color optical image scanner, a method of measuring light intensity within a particular spectral band, the method comprising the following steps:

(a) receiving the light unfiltered, by a first row of sensor elements;

(b) filtering the light through a first bandpass light filter for a second row of sensor elements;

(c) filtering the light through a second bandpass light filter for a third row of sensor elements;

(d) digitizing an analog output from the first, second and third rows of sensor elements into first, second and third numerical values respectively; and

(e) computing the light intensity within the particular spectral band as a linear transformation of the first, second and third numerical values.

14. In a color optical image scanner, a method of scanning gray scale and color images, the method comprising the following steps:

(a) exposing a first sensor element to light to be measured for a first exposure time;

(b) digitizing an analog output from the first sensor element into a first numerical value;

(c) exposing a second sensor element to the light to be measured filtered by a second filter for a second exposure time, the second exposure time greater than the first exposure time;

(d) exposing a third sensor element to the light to be measured filtered by a third filter for a third exposure time, the third exposure time greater than the first exposure time;

(e) digitizing an analog output from the second and third sensor elements into second and third numerical values respectively;

(f) computing three transformed numerical values as a linear transformation of the first, second, and third numerical values;

(g) scanning a gray scale image by repeating steps (a) and (b); and

(h) scanning a color image by repeating steps (a) through (f).

15. In an color optical image scanner, a method of measuring an intensity of light within a particular spectral band, the method comprising the following steps:

(a) filtering the light through a first bandpass light filter to a first row of sensor elements, the first bandpass filter passing substantially all the human visible light spectrum;

(b) filtering the light through a second bandpass light filter to a second row of sensor elements, the second bandpass filter passing substantially less than the human visible light spectrum;

(c) filtering the light through a third bandpass light filter to a third row of sensor elements, the third bandpass filter passing substantially less than the human visible light spectrum;

(d) digitizing an analog output from the first, second and third rows of sensor elements into first, second and third numerical values respectively; and

(e) computing the light intensity within the particular spectral band as a linear transformation of the first, second, and third numerical values.

16. In a color optical image scanner, a method of scanning gray scale and color images, the method comprising the following steps:

(a) exposing a first sensor element to light to be measured filtered by a first filter for a first exposure time, the first filter passing substantially all the human visible light spectrum;

(b) digitizing an analog output from the first sensor element into a first numerical value;

(c) exposing a second sensor element to the light to be measured filtered by a second filter for a second exposure time, the second exposure time greater than the first exposure time, the second filter passing substantially less than the human visible light spectrum;

(d) exposing a third sensor element to the light to be measured filtered by a third filter for a third exposure time, the third exposure time greater than the first exposure time, the third filter passing substantially less than the human visible light spectrum;

(e) digitizing an analog output from the second and third sensor elements into second and third numerical values respectively;

(f) computing three transformed numerical values as a linear transformation of the first, second and third numerical values;

(g) scanning a gray scale image by repeating steps (a) and (b); and

(h) scanning a color image by repeating steps (a) through (f).

17. A sensor assembly for an optical image scanner comprising:

a first row of sensor elements, each sensor element in the first row receiving light that is filtered by a first filter;

a second row of sensor elements, each sensor element in the second row receiving light that is filtered by a second filter;

a third row of sensor elements, each sensor element in the third row receiving light that is filtered by a third filter; and

a fourth row of sensor elements, each sensor element in the fourth row receiving light that is not filtered.

18. A color scanner comprising:

a sensor array having a plurality of sensor elements, at least one of the sensor elements receiving light that is not filtered and at least two of the sensor elements receiving light that is filtered;

a pixel at a particular position corresponding to one of the sensor elements that receives light that is not filtered and at least two of the sensor elements that receive light that is filtered;

for a color scan the color of a particular pixel being determined by a color transformation of light measured by all of the sensor elements corresponding to the particular pixel; and

for a gray scale scan, the color of the particular pixel being determined by light measured by the one sensor element, corresponding to the particular pixel, that receives light that is not filtered.

19. In a color optical image scanner, a method of scanning gray scale and color images, the method comprising the following steps:

(a) exposing a first sensor element to light to be measured filtered by a first filter for a first exposure time, the first filter passing substantially all the human visible light spectrum;

(b) digitizing an analog output from the first sensor element into a first numerical value;

(c) exposing a second sensor element to the light to be measured filtered by a second filter for a second exposure time, the second exposure time greater than the first exposure time, the second filter passing substantially less than the human visible light spectrum;

(d) exposing a third sensor element to the light to be measured filtered by a third filter for a third exposure time, the third exposure time greater than the first exposure time, the third filter passing substantially less than the human visible light spectrum;

(e) exposing a fourth sensor element to the light to be measured filtered by a fourth filter for a fourth exposure time, the fourth exposure time greater than the first exposure time, the fourth filter passing substantially less than the human visible light spectrum;

(f) digitizing an analog output from the second, third and fourth sensor elements into second, third and fourth numerical values respectively;

(g) computing three transformed numerical values as a linear transformation of the second, third and fourth numerical values;

(h) scanning a gray scale image by repeating steps (a) and (b); and

(i) scanning a color image by repeating steps (c) through (g).

20. In a color optical image scanner, a method of scanning gray scale and color images, the method comprising the following steps:

(a) exposing a first sensor element to light to be measured filtered by a first filter for a first exposure time, the first filter passing substantially all the human visible light spectrum;

(b) digitizing an analog output from the first sensor element into a first numerical value;

(c) exposing a second sensor element to the light to be measured filtered by a second filter for a second exposure time, the second exposure time greater than the first exposure time, the second filter passing substantially less than the human visible light spectrum;

(d) exposing a third sensor element to the light to be measured filtered by a third filter for a third exposure time, the third exposure time greater than the first exposure time, the third filter passing substantially less than the human visible light spectrum;

(e) exposing a fourth sensor element to the light to be measured filtered by a fourth filter for a fourth exposure time, the fourth exposure time greater than the first exposure time, the fourth filter passing substantially less than the human visible light spectrum;

(f) digitizing an analog output from the second, third and fourth sensor elements into second, third and fourth numerical values respectively;

(g) computing three transformed numerical values as a linear transformation of the first, second, third and fourth numerical values;

(h) scanning a gray scale image by repeating steps (a) and (b); and

(i) scanning a color image by repeating steps (a) through (g).