SYSTEM AND METHOD TO AUTOMATICALLY FOCUS AN IMAGE READER

• US 20100044440A1
• Filed: 11/02/2009
• Published: 02/25/2010
• Est. Priority Date: 03/11/2005
• Status: Active Grant

• Current Assignee: Hand Held Products Incorporated (Honeywell International Inc.)
• Original Assignee: Hand Held Products Incorporated (Honeywell International Inc.)
• Inventors: Havens, William H., Wang, Ynjiun P.
• Granted Patent: US 8,146,820 B2
• Time in Patent Office: Days
• US Class Current: 235/462.240
• CPC Class Codes: G06K 7/10722 Photodetector array or CCD scanning
• CPC Class Codes: G06K 7/10732 Light sources
• CPC Class Codes: G06K 7/10811 Focalisation
• CPC Class Codes: G06K 7/10831 Arrangement of optical elements, e.g. lenses, mirrors, prisms optical elements per se G02B
• CPC Class Codes: H04N 23/689 Motion occurring during a rolling shutter mode

Abstract

The invention features a system and method to automatically focus an image reader using a single frame of image data. The method comprises exposing sequentially a plurality of rows of pixels in the image sensor. The method further comprising varying in incremental steps the focus of the image reader'"'"'s optical system from a first setting where a distinct image of objects located at a first distance from the image reader is formed on the image sensor to a second setting where a distinct image of objects located at a second distance from the image reader is formed on the image sensor. As part of the method, the varying of the focus of the optical system occurs during the exposure of the plurality of rows of pixels.

Claims

1. A bar code reading device for minimizing ambient light image degradation, the bar code reading device comprising:

an integrated circuit including at least an image sensor array, the image sensor array providing a signal suitable for light intensity determination;

a hand held housing encapsulating said image sensor array;

a rolling shutter control module configured to sequentially expose a plurality of lines of pixels in the image sensor array;

a global electronic shutter control module configured to simultaneously expose the plurality of lines of pixels in the image sensor array,

a bar code processing module configured to identify the presence of a bar code symbol represented in collected image data;

wherein said bar code reading device is programmable to operate in a mode in which said bar code reading device selects one of the rolling shutter control module and the global electronic shutter control module in response to the signal suitable for light intensity determination.

2. The bar code reading device according to claim 1, wherein the signal suitable for light intensity determination includes information related to an intensity of a light source of the image reader.

3. The bar code reading device according to claim 1, wherein the signal suitable for light intensity determination is useful for determining whether a minimum integration time is satisfied.

4. The bar code reading device according to claim 1, wherein the signal suitable for light intensity determination is useful for determining whether an integration time for the current environmental condition is less than a calculated minimum integration time.

5. The bar code reading device according to claim 1, wherein the rolling shutter control module and the global electronic shutter control module are integrated on the same integrated circuit containing the image sensor array.

6. A method for operating a portable bar code reading device, the method comprising:

determining at least one parameter related to an ambient light intensity;

analyzing the at least one parameter;

switching control of an image sensor array in the portable bar code reading device from a global electronic shutter control module to a rolling shutter control module in response to the analysis of the at least one parameter;

collecting image data while said image sensor array is being controlled by said rolling shutter control module; and

transferring collected image data collected while said image sensor array is controlled by said rolling shutter control module to a bar code decode module.

7. The method according to claim 6, wherein the at least one parameter includes an exposure time for current environmental conditions.

8. The method according to claim 7, wherein the analyzing the at least one parameter includes calculating a ratio of the exposure time for current environmental conditions to a predetermined exposure time.

9. The method according to claim 8, wherein the predetermined exposure time is based on illumination supplied by light sources of the image reader.

10. The method according to claim 6, wherein the analyzing the at least one parameter includes determining whether a ratio of the ambient light intensity to an intensity of a light source of the image reader exceeds a specified threshold.

11. A bar code reading device for reading a bar code disposed on a target, said bar code reading device comprising:

an integrated circuit including an image sensor array, said image sensor array having a plurality of rows of pixels;

a memory;

a hand held housing encapsulating said image sensor array;

an imaging lens capable of directing light reflected from a target onto said image sensor array, wherein said imaging lens is capable of first and second focus settings, wherein said bar code reading device when said imaging lens is at a first focus setting has a first best focus distance, and wherein said bar code reading device when said imaging lens is at said second focus setting has a second best focus distance;

a trigger for initiating reading of said bar code;

wherein said bar code reading device is adapted so that subsequently to said trigger being depressed, said bar code reading device is operative for determining a read attempt focus setting of said imaging lens;

wherein responsively to said determining, said bar code reading device captures a frame of image data representing light incident on said image sensor array when said focus setting is at said read attempt focus setting;

wherein further responsively to said determining, said bar bode reading device attempts to decode said bar code utilizing said frame of image data representing light incident on said image sensor array when said focus setting is at said read attempt focus setting;

wherein said bar code reading device is operative to output decoded data from data responsively to a successful decoding of the bar code;

wherein said bar code reading device is operative to one of store into said memory or transmit from said bar code reading device said frame of image data responsively to a determination that said frame of image data does not include a representation of a bar code.

12. The bar code reading device of claim 11, wherein said read attempt focus setting is a focus setting other than said first focus setting or said second focus setting.

13. The bar code reading device of claim 11, wherein for performance of the determining, the bar code reading device processes image data.

14. The bar code reading device of claim 13, wherein said bar code reading device in processing said image data assesses a flatness of image data.

15. The bar code reading device of claim 11, wherein the bar code reading device is adapted to projection aiming light, and wherein for performance of the determining, the bar code reading device utilizes a signal that is responsive to the aiming light.