High speed auto-exposure control

• US 7,227,117 B1
• Filed: 05/30/2006
• Issued: 06/05/2007
• Est. Priority Date: 05/30/2006
• Status: Active Grant

• Current Assignee: Symbol Technologies, LLC (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: Carlson, Brad, Lackemann, Thomas, Pang, Robert
• Primary Examiner(s): Lee; John R.
• Application Number:
  US11/442,912
• Time in Patent Office: 371 Days
• Field of Search: 250/208.1, 235/462.1, 235/462.24, 235/462.25, 235/462.26, 235/462.41, 235/455, 384/364
• US Class Current: 250/208.1
• CPC Class Codes: G06K 7/10584 Source control
• CPC Class Codes: G06K 7/10722 Photodetector array or CCD scanning
• CPC Class Codes: G06K 7/10752 Exposure time control

Abstract

An imager with a two dimensional array of sensors processes illumination data from a subset of the sensors located within a selected region of the image to determine imager settings prior to acting upon a full frame of data. In this manner imager settings can be quickly determined by transferring and examining only the segment of the sensor array data.

Claims

1. An imager that processes indicia comprising:

a two-dimensional array of sensors capable of collecting data corresponding to an amount of light collected by the sensors during an exposure time to produce an image of a target surface at which the scanner is aimed and wherein the two-dimensional array of sensors is capable of outputting array segment data corresponding to a segment of the two-dimensional array of sensors, the segment corresponding to a set of adjacent rows of sensors located about a center of the array of sensors, the set of adjacent rows of sensors comprising not more than 10% of a total number of rows of sensors of the array, and enlarged array data corresponding to data from a predetermined increased number of the sensors in the array;

a decoder that inputs the array segment data during a data input period that is shorter than a period of time required to input the enlarged array data and wherein the decoder determines a modified exposure time based on an exposure quality of the array segment data;

an exposure quality controller that controls a subsequent collection of light data to occur during a modified exposure time duration; and

wherein the decoder selectively sends control signals to the array to cause it to output the enlarged array data for subsequent indicia processing.

2. The imager of claim 1 wherein the segment is a set of rows of sensors located near a center of the array.

3. The imager of claim 2 wherein the rows are adjacent to one another.

4. The imager of claim 2 wherein the sensor exposure quality is an average light level of the sensors in the segment.

5. The imager of claim 1 wherein the decoder interprets array segment data to output information encoded in a barcode image captured by the sensors in the segment.

6. The imager of claim 1 wherein the enlarged array data corresponds to data from substantially all of the sensors in the array.

7. An indicia decoder and two-dimensional array of sensors comprising:

the two-dimensional array of sensors capable of collecting data corresponding to an amount of light collected by the sensors during an exposure time to produce an image of a target surface at which the scanner is aimed and wherein the two-dimensional array of sensors is capable of operating in a cropped frame mode in which it outputs array segment data corresponding to a first segment of the two-dimensional array of sensors, the first segment corresponding to a set of adjacent rows of sensors located about a center of the array of sensors, the set of adjacent rows of sensors comprising not more than 10% of a total number of rows of sensors of the array, and an enlarged frame mode in which it outputs array data corresponding to second, larger segment of array of sensors;

the decoder inputting data from the two-dimensional array of sensors and comprising;

a frame selector in communication with the array of sensors that selectively places the array in cropped frame or enlarged frame mode;

an exposure quality controller that inputs array segment sensor data, determines an exposure quality of the image based on the array segment sensor data and wherein if the exposure quality is within a range of acceptable values the exposure quality controller signals the frame selector to place the array in full frame mode for a subsequent collection of light data; and

wherein if the exposure quality is outside the range of acceptable values, the exposure quality controller signals the frame selector to place the array in cropped frame mode and determines one of a modified exposure time and gain setting for a subsequent collection of light data with the array of sensors; and

wherein the frame selector selectively sends control signals to place the array enlarged frame mode for subsequent indicia processing once the exposure quality is within the range of acceptable values.

8. The decoder of claim 7 wherein the exposure quality is an average level of light received by the sensors in the array.

9. The decoder of claim 7 wherein the decoder determines an exposure time setting for a subsequent collection of light data by applying a preset increment to the current exposure time.

10. The decoder of claim 8 wherein the decoder determines a gain setting for a subsequent collection of light data by applying a preset increment to the current gain setting.

11. The decoder of claim 7 wherein the second segment of the array corresponds to substantially the entire array.

12. A method that processes an indicia that is present on a target surface with an imager that includes a two dimensional array of light sensors that collects light data corresponding to light reflected back to the imager from the target surface during an exposure time to produce light sensor data corresponding to an image of the target surface, the method comprising:

selecting a first subset of light sensors from the two dimensional array to be used to determine an appropriate duration of the exposure time, the first subset of light sensors corresponding to a set of adjacent rows of light sensors located about a center of the array of light sensors, the set of adjacent rows of light sensors comprising not more than 10% of a total number of rows of light sensors of the array;

collecting light sensor array data with the array of sensors during the exposure time;

inputting light data from the selected first subset of light sensors to an exposure quality controller;

adjusting at least one of the duration of the exposure time and an output component gain setting based on light data from sensors in the selected first subset of light sensors; and

selecting a second, larger, subset of light sensors and inputting light data from the second subset of light sensors in subsequent indicia processing.

13. The method of claim 12 wherein data from the subset of light sensors is input to the exposure quality controller by skipping a first number of rows of sensors prior to transferring sensor data to the exposure quality controller.

14. The method of claim 12 wherein the at least one of the duration of the exposure time and the output component gain setting is adjusted by calculating an average sensor signal level and comparing the average signal level to a pre-selected minimum signal and increasing the at least one of exposure time duration and output component gain setting in a subsequent collection of light sensor data when the average signal level is less than the minimum signal.

15. The method of claim 12 comprising decoding the data from the first subset of light sensors to determine information encoded in the indicia.

16. An apparatus for processing an indicia that is present on a target surface with an imager that includes a two dimensional array of light sensors that collects light data corresponding to light reflected back to the imager from the target surface during an exposure time to produce light sensor data corresponding to an image of the target surface, the apparatus comprising:

means for selecting a first subset of light sensors from the two dimensional array to be used to determine an appropriate duration of the exposure time, the first subset of light sensors corresponding to a set of adjacent rows of light sensors located about a center of the array of light sensors, the set of adjacent rows of sensors comprising not more than 10% of a total number of rows of light sensors of the array;

means for collecting light sensor array data with the array of sensors during the exposure time;

means for inputting light data from the selected first subset of light sensors to an exposure quality controller;

means for adjusting at least one of the duration of the exposure time and an output component gain setting based on light data from sensors in the selected first subset of light sensors; and

means for selecting a second, larger, subset of light sensors and wherein the means for inputting light data inputs data from the second subset of light sensors in subsequent indicia processing.

17. The apparatus of claim 16 wherein the means for inputting light data includes means for skipping a first number of rows of sensors prior to transferring sensor data to the exposure quality controller.

18. The apparatus of claim 16 wherein the means for adjusting the at least one of the duration of the exposure time and an output component gain setting includes means for calculating an average sensor signal level and means for comparing the average signal level to a pre-selected minimum signal and wherein the means for adjusting the at least one of the duration of the exposure time and an output component gain setting increases the at least one of the duration of the exposure time and an output component gain setting in a subsequent collection of light sensor data when the average signal level is less than the minimum signal.

19. The apparatus of claim 16 comprising means for decoding the data from the first subset of light sensors to determine information encoded in the indicia.

20. For use with an imager that includes a two dimensional array of light sensors that collects light data corresponding to light reflected back to the imager from a target surface during an exposure time to produce light sensor data corresponding to an image of the target surface, computer readable media having computer-executable instructions stored thereon for performing steps to process an indicia that is present on the target surface, the steps comprising:

selecting a first subset of light sensors from the two dimensional array to be used to determine an appropriate duration of the exposure time, the first subset of light sensors corresponding to a set of adjacent rows of light sensors located about a center of the array of light sensors, the set of adjacent rows of sensors comprising not more than 10% of a total number of rows of light sensors of the array;

collecting light sensor array data with the array of sensors during the exposure time;

inputting light data from the selected first subset of light sensors to an exposure quality controller;

adjusting at least one of the duration of the exposure time and an output component gain setting based on light data from sensors in the selected first subset of light sensors; and

selecting a second, larger, subset of light sensors and inputting light data from the second subset of light sensors in subsequent indicia processing.

21. The computer readable media of claim 20 wherein data from the first subset of light sensors is input to the exposure quality controller by skipping a first number of rows of sensors prior to transferring sensor data to the exposure quality controller.

22. The computer readable media of claim 20 wherein the at least one of the duration of the exposure time and output component gain setting is adjusted by calculating an average sensor signal level and comparing the average signal level to a pre-selected minimum signal and increasing the at least one of the duration of the exposure time and output component gain setting in a subsequent collection of light sensor data when the average signal level is less than the minimum signal.

23. The computer readable media of claim 20 wherein the steps include decoding the data from the first subset of light sensors to determine information encoded in the indicia.