Optical reader with addressable pixels

• US 6,173,894 B1
• Filed: 10/29/1998
• Issued: 01/16/2001
• Est. Priority Date: 08/23/1996
• Status: Expired due to Term

• Current Assignee: PTO (Safe Fleet Holdings LLC)
• Original Assignee: PTO (Safe Fleet Holdings LLC)
• Inventors: Colley, James E., Olmstead, Bryan L.
• Primary Examiner(s): TREMBLAY, MARK STEPHEN
• Application Number:
  US09/182,954
• Time in Patent Office: 810 Days
• Field of Search: 235/462.01, 235/462.16, 235/462.17, 235/462.18, 235/439, 235/440
• US Class Current: 235/462.17
• CPC Class Codes: G06K 7/10722 Photodetector array or CCD scanning
• CPC Class Codes: H04N 25/616 involving a correlated sampling function, e.g. correlated double sampling [CDS] or triple sampling
• CPC Class Codes: H04N 25/77 Pixel circuitry, e.g. memories, A/D converters, pixel amplifiers, shared circuits or shared components

Abstract

An optical or symbol reader including CMOS circuitry preferably integrated on a single chip. A CMOS optical reader chip comprises a CMOS imaging array having a plurality of pixels each with a dedicated pixel-site circuit. Charge is accumulated at each pixel location transferred upon demand to a common bus. In a preferred embodiment, exposure time of the imaging array is controlled using a feedback loop. One or more exposure control pixels are positioned adjacent to or within the imaging array and receive light along with the imaging array. The charge of the exposure control pixel or pixels is measured against a threshold level, and the amount of time taken to reach the threshold level determines the time exposure of the pixels of the imaging array. CMOS signal processing circuitry is employed which, in combination with the exposure control circuitry, minimizes time-to-read over a large range of light levels, while performing spatially optimal filtering. Clocking cycles and control signals are time-adjusted in accordance with the varying output frequency of the imaging array so as to provide invariant frequency response by the signal processing circuitry. A multi-dimensional CMOS imaging array is also provided having simultaneous pixel exposure with non-destructive readout of the pixel contents.

Claims

1. An optical reader comprising:

a common output bus;

an imaging array comprising a plurality of pixels arranged in a sparse two-dimensional pattern, each pixel connected to said common output bus and comprising a photo-sensitive element and a pixel circuit connected to said photo-sensitive element;

a plurality of pixel select signals connected to said pixels, for selecting a pixel to be read;

an address generator having a plurality of output lines connected to said pixels, said address generator located on the same chip as said imaging array and providing individual access to said pixels according to a predefined, fixed sequence;

a filter located on said chip and connected to said common output bus; and

an edge detector located on said chip and connected to an output of said filter.

2. The optical reader of claim 1 wherein said optical reader further comprises a symbology decoder connected to said edge detector.

13. The optical reader of claim 1, wherein said imaging array, said address generator, said filter and said edge detector are all manufactured from a common CMOS process.

14. The optical reader of claim 13, wherein said edge detector outputs a feature measurement signal, said feature measurement signal available as an output of said chip.

3. An integrated optical reader circuit, comprising:

an imaging array fabricated using a CMOS process and located on a CMOS chip having a chip substrate, said imaging array comprising a plurality of randomly accessible pixels arranged in a sparse two-dimensional pattern;

an address generator connected to said imaging array, said address generator causing accumulated charge at each pixel to be read out according to a predefined, fixed sequence;

an imaging array output signal connected to said imaging array; and

a signal processing circuit connected to said imaging array output signal, said signal processing circuit fabricated using a CMOS process and located on said CMOS chip;

wherein said signal processing circuit comprises an amplifier connected to said imaging array output signal, a low pass filter connected to said amplifier, and an edge detector connected to said low pass filter.

15. The integrated optical reading unit of claim 3, wherein said edge detector outputs a feature measurement signal, said feature measurement signal available as an output from said CMOS chip.

4. An optical reader comprising:

a lens;

a CMOS imaging array positioned so as to receive light focused by said lens, said CMOS imaging array having a sparse two-dimensional pattern of randomly accessible pixels;

an address generator connected to said CMOS imaging array, said address generator causing accumulated charge at each randomly accessible pixel to be read out according to a predefined, fixed sequence;

an edge detector connected to an output of said CMOS imaging array, said edge detector located on the same chip as said CMOS imaging array and manufactured from the same CMOS process as said CMOS imaging array.

5. An optical reader comprising:

a lens;

a CMOS imaging array positioned so as to receive light focused by said lens, said CMOS imaging array having a two-dimensional pattern of randomly accessible pixels, said two-dimensional pattern of randomly accessible pixels comprising a grid pattern, said grid pattern comprising a plurality of horizontal imaging lines and a plurality of vertical imaging lines, the number of said horizontal imaging lines being substantially less than a number of pixels needed to traverse said imaging array in a vertical direction, and the number of said vertical imaging lines being substantially less than a number of pixels needed to traverse said imaging array in a horizontal direction; and

an edge detector connected to an output of said CMOS imaging array.

6. An optical reader comprising:

a lens;

a CMOS imaging array positioned so as to receive light focused by said lens, said CMOS imaging array having a two-dimensional pattern of randomly accessible pixels, said two-dimensional pattern of randomly accessible pixels comprising an asterisk pattern; and

an edge detector connected to an output of said CMOS imaging array.

7. An optical reader comprising:

a CMOS imaging array positioned so as to receive light focused by said lens, said CMOS imaging array having a two-dimensional pattern of randomly accessible pixels, said two-dimensional pattern of randomly accessible pixels comprising a combined grid and asterisk pattern; and

an edge detector connected to an output of said CMOS imaging array.

8. A method for optically reading images, comprising the steps of:

receiving light at a plurality of imaging pixels arranged in a sparse two-dimensional pattern, each of said imaging pixels having a physical address, and accumulating a charge individually at each imaging pixel in response thereto;

generating a predefined, fixed sequence of pixel address signals, said sequence independent of the ordinal sequence of physical addresses of said imaging pixels;

transferring an accumulated charge, corresponding to an amount of light collected, from each imaging pixel to a common output bus, thereby generating an imaging signal, each imaging pixel being connected to the common output bus in response to the generation of its pixel address;

filtering said imaging signal;

detecting transitions directly in said imaging signal between relatively higher and relatively lower signal amplitudes corresponding to transitions between darker and lighter portions of a symbol being read; and

decoding said symbol using said detected transitions;

wherein said steps of accumulating a charge individually at each imaging pixel, generating a predefined, fixed sequence of pixel address signals, transferring an accumulated charge from each imaging pixel to a common output bus, filtering said imaging signal, and detecting transitions in said imaging signal between relatively higher and relatively lower signal amplitudes are carried out by circuitry located on a single CMOS integrated chip.

12. The method of claim 8, wherein said step of decoding said symbol is also carried out by circuitry located on said single CMOS integrated chip.

9. A method for optically reading images, comprising the steps of:

receiving light at a plurality of imaging pixels arranged in a two-dimensional pattern, each of said imaging pixels having a physical address, and accumulating a charge individually at each imaging pixel in response thereto;

generating a sequence of pixel address signals, said sequence independent of the ordinal sequence of physical addresses of said imaging pixels;

transferring an accumulated charge, corresponding to an amount of light collected, from each imaging pixel to a common output bus, thereby generating an imaging signal, each imaging pixel being connected to the common output bus in response to the generation of its pixel address;

filtering said imaging signal;

detecting transitions in said imaging signal between relatively higher and relatively lower signal amplitudes corresponding to transitions between darker and lighter portions of a symbol being read; and

decoding said symbol using said detected transitions;

wherein said two-dimensional pattern comprises at least two linear arrays of imaging pixels overlapping in at least one common pixel, and wherein said step of transferring an accumulated charge from each of said imaging pixels in the two-dimensional pattern to the common output bus comprises the step of transferring an accumulated charge from said at least one common pixel to the common output bus while storing said accumulated charge locally in a separate storage region at said at least one common pixel so that the accumulated charge at said at least one common pixel remains substantially unaffected.

10. The method of claim 9, further comprising the step of transferring the same accumulated charge at said at least one common pixel to said common output bus in response to a second generation of the pixel address of said at least one common pixel.

11. A method for optically reading images, comprising the steps of:

receiving light at a plurality of imaging pixels arranged as intersecting linear arrays in a two-dimensional pattern, each of said imaging pixels having a physical address, and accumulating a charge individually at each imaging pixel in response thereto;

generating a sequence of pixel address signals, said sequence independent of the ordinal sequence of physical addresses of said imaging pixels;

transferring an accumulated charge, corresponding to an amount of light collected, from each imaging pixel to a common output bus, thereby generating an imaging signal, each imaging pixel being connected to the common output bus in response to the generation of its pixel address;

filtering said imaging signal;

detecting transitions in said imaging signal between relatively higher and relatively lower signal amplitudes corresponding to transitions between darker and lighter portions of a symbol being read; and

decoding said symbol using said detected transitions;

wherein said step of transferring an accumulated charge from each imaging pixel to a common output bus comprises the step of reading at least one imaging pixel while storing its accumulated charge locally in a separate storage region at said at least one common pixel, whereby the accumulated charge of said at least one imaging pixel is not affected by reading, said at least one imaging pixel being located at an intersection of two or more of said intersecting linear arrays.