Methods and apparatus for automatic exposure control

• US 7,148,923 B2
• Filed: 07/11/2001
• Issued: 12/12/2006
• Est. Priority Date: 09/30/2000
• Status: Expired due to Term

• Current Assignee: Hand Held Products Incorporated (Honeywell International Inc.)
• Original Assignee: Hand Held Products Incorporated (Honeywell International Inc.)
• Inventors: Pankow, Matthew W., Hussey, Robert M., Meier, Timothy P., Harper, Jeffrey D.
• Primary Examiner(s): Ometz, David
• Assistant Examiner(s): TRAN, NHAN T
• Application Number:
  US09/903,300
• Publication Number:
  US 20020039137A1
• Time in Patent Office: 1,980 Days
• Field of Search: 348/221.1, 348/229.1, 348/362, 235/462
• US Class Current: 348/229.1
• CPC Class Codes: G06K 7/10722 Photodetector array or CCD scanning
• CPC Class Codes: G06K 7/10752 Exposure time control
• CPC Class Codes: G06K 7/1092 sensing by means of TV-scanning

Abstract

A multi-dimensional imaging device and method for automated exposure control that implement two distinct modules to control the exposure and gain settings in the imager so that processing can occur in a multi-tasking single CPU environment. The first module, referred to herein as the imager control module, controls the exposure and gain settings in the imager. The first module is typically implemented in a high priority routine, such as an interrupt service routine, to insure that module is executed on every captured frame. The second module, referred to herein as the histogram processing module, calculates a target contrast (the product of the targeted exposure and gain settings) based on feedback data from the first module and image data from memory. The second module is typically implemented in a low priority routine, such as a task level routine, to allow for the routine to be executed systematically in accordance with priority.

Claims

1. An imaging device for capturing optical image data, the device comprising:

an imager for generating an image signal;

a memory component that receives the image signal from the imager and stores the image signal as image data;

a processor operating according to a multi-tasking operating system;

a histogram processing module executed by the multi-tasking operating system as a low priority task that analyzes the image data in the memory component and calculates a target contrast; and

an imager control module executed by the multi-tasking operating system concurrently with the histogram processing module, the imager control module being executed as a high priority task that sets a gain and exposure for the imager based on the target contrast calculated by the histogram processing module.

2. The imaging device of claim 1, wherein the imager generates the image signal from multi-dimensional symbologies.

3. The imaging device of claim 1, wherein the multi-tasking operating system is a real-time operating system and wherein the imager control module is executed as a real-time thread.

4. The imaging device of claim 1, wherein the imager control module is implemented in a high priority thread.

5. The imaging device of claim 1, wherein the imager control module is implemented in an interrupt service routine.

6. The imaging device of claim 1, wherein the histogram processing module is implemented in a low priority thread routine.

7. The imaging device of claim 1, further comprising a Direct Memory Access (DMA) controller that receives the image signals from the imager, responds to an image capture command from the histogram processing module and transfers captured image signals into the memory component.

8. The imaging device of claim 1, further comprising a programmable logic device that serves as an interface between the imager and the processor.

9. The imaging device of claim 8, wherein the programmable logic device comprises a DMA controller that receives the image signals from the imager, responds to an image capture command from the histogram processing module and transfers captured image signals into the memory.

10. An imaging device for capturing optical image data, the device comprising:

an imager for generating an image signal;

a memory component that receives the image signal from the imager and stores the image signal as image data; and

a processor operating pursuant to a multi-tasking operating system that concurrently executes a high priority software-exclusive module for real time control of the imager with a lower priority software-exclusive module that examines the image data and provides feedback to the high priority software-exclusive module facilitating setting of a gain and exposure of the imager.

11. A method for exposure control in a multi-dimensional imaging device, the method comprising:

executing, as a high priority task in a multi-tasking operating system, a first software-exclusive module that controls exposure and gain settings in the imager in response to an end of frame signal;

generating, in the first software-exclusive module, a captured contrast setting, wherein contrast is defined as the product of the exposure setting and the gain setting;

executing, concurrently with the the first software-exclusive module, a second software-exclusive module that calculates a target contrast setting in response to the end of frame signal, the captured contrast setting and stored image data, the second software-exclusive module being executed as a low priority task;

generating, in the first software-exclusive module, a subsequent exposure and gain setting for the imager in response to the target contrast setting; and

implementing the subsequent exposure and gain setting in the imager.

12. A program storage device readable by a processor, tangibly embodying a program of instructions executable by the processor to perform a method for exposure control in a multi-dimensional imaging, the method comprising:

generating, in a high priority software-exclusive module, a captured contrast setting in response to an end of frame signal from an imager, wherein contrast is defined as the product of exposure setting and gain selling;

calculating, in a low priority software-exclusive module concurrently executed with the high priority software-exclusive module, a target contrast setting in response to the end of frame signal from the imager, the captured contrast setting and stored image data;

generating, in the high priority software-exclusive module, a subsequent exposure and gain setting for the imager in response to the target contrast setting; and

implementing the subsequent exposure and gain setting in an imager of the multi-dimensional imaging device.

13. The program storage device of claim 12, wherein generating, in a high priority software-exclusive module, a captured contrast setting in response to an end of frame signal from an imager and generating, in the high priority software-exclusive module, a subsequent exposure and gain setting for the imager in response to the target contrast setting further comprises generating in an interrupt service routine module.

14. The program storage device of claim 12, wherein generating, in a high priority software-exclusive module, a captured contrast setting in response to an end of frame signal from an imager and generating, in the high priority software-exclusive module, a subsequent exposure and gain setting for the imager in response to the target contrast setting further comprises generating in a high priority thread module.

15. The program storage device of claim 12, wherein generating, in a high priority software-exclusive module, a captured contrast setting in response to an end of frame signal from an imager and generating, in the high priority software-exclusive module, a subsequent exposure and gain setting for the imager in response to the target contrast setting further comprises generating in a high priority task module.

16. The program storage device of claim 12, wherein calculating, in a low priority software-exclusive module, a target contrast setting in response to the end of frame image signal from the imager, the captured contrast setting and stored image data further comprises calculating in a low priority task module.

17. The program storage device of claim 12, wherein calculating, in a low priority software-exclusive module, a target contrast setting in response to the end of frame image signal from the imager, the captured contrast setting and stored image data further comprises calculating in a low priority thread module.

18. The program storage device of claim 12, wherein calculating, in a low priority software-exclusive module, a target contrast setting in response to the end of frame image signal from the imager, the captured contrast setting and stored image data further comprises implementing histogram processing to calculate a target contrast setting.

19. A portable bar code reader for capturing optical image data, the portable bar code reader comprising:

an imager for generating an image signal based on a bar code;

a memory component that receives the image signal from the imager and stores the image signal as image data; and

a central processing unit operating in accordance with a multi-tasking operating system and a plurality of concurrently executed software based imaging modules to calculate and adjust settings of the imager based on an analysis of the image signals stored in the memory component wherein modules that adjust setting of the imager are given a higher priority than modules that calculate desired settings of the imager.

20. The bar code reader of claim 19, wherein the software based imaging modules comprise a first software-exclusive module that controls the exposure and gain setting in the imager and a second software-exclusive module that implements computations in response to exposure data transmitted from the first software-exclusive module to determine a targeted exposure and gain setting.

21. The bar code reader of claim 20, wherein the second software-exclusive module implements computations in response to exposure data transmitted from the first software-exclusive module and image data transmitted from the memory component.

22. The bar code reader of claim 20, wherein the first software-exclusive module is implemented in a high priority thread.

23. The bar code reader of claim 20, wherein the first software-exclusive module is implemented in a high priority task.

24. The bar code reader of claim 20, wherein the first software-exclusive module is implemented in an interrupt service routine.

25. The bar code reader of claim 20, wherein the second software-exclusive module is implemented in a low priority thread routine.

26. The bar code reader of claim 20, wherein the second software-exclusive module is implemented in a low priority task routine.

27. The bar code reader of claim 20, wherein the second software-exclusive module includes histogram processing.

28. The bar code reader of claim 20, wherein the first software-exclusive module is implemented in a an interrupt service routine and the second software-exclusive module is implemented in a low priority task routine.

29. A barcode imaging device for capturing information, the device comprising:

an optics imaging system that captures an image of a two-dimensional barcode data symbol;

an imaging sensor in communication with the optics imaging system that receives the image from the optics imaging system and converts the image to an electrical signal representative of image data;

a memory storage element in communication with the sensor that stores the image data; and

a central processing unit (CPU) in communication with the imaging system, the imaging sensor and the storage element, wherein the CPU implements a multitasking operating system that concurrently executes a first high priority software-exclusive module that provides imaging system control processing and a second low priority software-exclusive module that recognizes and decodes the image data.

30. The device of claim 29, wherein the multi-tasking operating system implemented by the CPU of the barcode imaging device further executes a third software-exclusive module that performs calculations on the image data.

31. The device of claim 29, wherein the first software-exclusive module is further defined as controlling imager exposure time.

32. The device of claim 29, wherein the first software-exclusive module is further defined as synchronized with timing of the imager.

33. The device of claim 29, wherein the barcode imaging device is further defined as a portable barcode imaging device.