IMAGING DEVICE HAVING LIGHT FIELD IMAGE SENSOR

• US 20140097252A1
• Filed: 12/09/2013
• Published: 04/10/2014
• Est. Priority Date: 12/22/2011
• Status: Active Grant

• Current Assignee: Symbol Technologies, LLC (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: He, Duanfeng, Gurevich, Vladimir, Goren, David P., Fan, Nong-Qiang
• Granted Patent: US 8,973,826 B2
• Time in Patent Office: Days
• US Class Current: 235/462.41
• CPC Class Codes: G06K 7/10722 Photodetector array or CCD scanning
• CPC Class Codes: G06K 7/10811 Focalisation
• CPC Class Codes: G06K 7/14 using light without selection of wavelength, e.g. sensing reflected white light G06K7/10831 - G06K7/1097 take precedence

Abstract

A method of imaging a target object with an imaging reader. The method includes the following: (1) detecting light from the target object through a lens arrangement with an image sensor to generate light-field data; (2) generating a stream of image data including image data representing an expected in-focus image of the target object, and (3) processing the expected in-focus image of the target object to decode a barcode on the target object. The image sensor includes an array of photosensitive elements and an array of microlenses that overlays the array of photosensitive elements located at a focus plane of the microlens.

Claims

1. An apparatus comprising:

an image sensor for generating light-field data, wherein the image sensor comprises (1) an array of photosensitive elements and (2) an array of microlenses that overlays the array of photosensitive elements with a uniform spacing, wherein a microlens covers multiple photosensitive elements each receiving light through the microlens to function as a sub-pixel;

an image processing unit (IPU) operatively connected to the image sensor to receive the light-field data from the image sensor, the IPU being operative to generate a stream of image data including image data representing an expected in-focus image of a target object; and

a controller operatively connected to the IPU to process the stream of image data received from the IPU.

2. The apparatus of claim 1, wherein the IPU is configured for:

selecting a set of predetermined focus planes; and

constructing a set of images of the target object from the light-field data, wherein each image in the set of images is constructed from the light-field data using one of the predetermined focus planes as a corresponding focus plane.

3. The apparatus of claim 2, further comprising:

a lens arrangement positioned in front of the image sensor; and

wherein each predetermined focus plane is titled with respect an optical axis of the lens arrangement.

4. The apparatus of claim 2, wherein the IPU is configured for:

generating a stream of image data including image data representing each image from the set of images.

5. The apparatus of claim 2, wherein the IPU is configured for:

selecting one image from the set of images constructed from the light-field data as the expected in-focus image of the target object, wherein the one image that is selected has better sharpness than other images from the set of images.

6. The apparatus of claim 1, wherein the IPU is configured for:

constructing multiple local in-focus images from the light-field data; and

combining the multiple local in-focus images together to form the expected in-focus image of the target object.

7. The apparatus of claim 6, wherein the multiple local in-focus images includes more than one local in-focus image constructed from the light-field data, and constructing a chosen local in-focus image comprises:

finding the sharpness of a set of local images with different corresponding local focus planes and with each local image covering essentially the same area on the target object; and

selecting one local image from the set of local images as the chosen local in-focus image, wherein the chosen local in-focus image has better sharpness than other images from the set of local images.

8. The apparatus of claim 7, wherein the IPU is configured for:

transferring the chosen local in-focus image to the controller; and

after the transferring the chosen local in-focus image, reusing the memory used for calculating the chosen local in-focus image to calculate another local in-focus image.

9. The apparatus of claim 1, wherein the IPU is configured for:

selecting three predetermined focus planes;

constructing automatically three images of the target object from the light-field data, wherein each of the three images is constructed from the light-field data using one of the three predetermined focus planes as a corresponding focus plane; and

generate a stream of image data including image data representing each of the three images.

10. The apparatus of claim 1, wherein the IPU is configured for:

constructing a reference image of the target object from the light-field data using a first focus plane as a corresponding focus plane;

comparing the reference image with an intensity distribution in the sub-pixels to selected one of a near focus plane, a far focus plane, and the first focus plane as a next focus plane, wherein the first focus plane is located between the near focus plane and the far focus plane; and

using the next focus plane to construct the expected in-focus image of the target object from the light-field data.

11. The apparatus of claim 10 wherein said comparing the reference image with an intensity distribution in the sub-pixels comprises:

comparing direction of black-to-white transition between micro-lenses and sub-pixels.

12. The apparatus of claim 1, wherein the IPU is configured for:

determining an optimized synthesized aperture based on an intensity of light received from the target object; and

using the optimized synthesized aperture to construct the expected in-focus image of the target object from the light-field data.

13. The apparatus of claim 1, wherein the amount of data transferred to the controller from the IPU is substantially less than the amount of data the IPU receives from the image sensor.

14. (canceled)

15. A method of imaging a target object with an imaging reader, the method comprising:

detecting light from the target object through a lens arrangement with an image sensor to generate light-field data, wherein the image sensor comprises (1) an array of photosensitive elements and (2) an array of microlenses that overlays the array of photosensitive elements with a uniform spacing, wherein a microlens covers multiple photosensitive elements each receiving light through the microlens to function as a sub-pixel;

generating a stream of image data including image data representing an expected in-focus image of the target object, a stream of image data being generated from the light-field data;

selecting a set of predetermined focus planes each being titled with respect an optical axis of the lens arrangement; and

constructing a set of images of the target object from the light-field data, wherein each image in the set of images is constructed from the light-field data using one of the predetermined focus planes as a corresponding focus plane.

16. The method of claim 15, further comprising:

generating a stream of image data including image data representing each image from the set of images.

17. The method of claim 15, further comprising:

selecting one image from the set of images constructed from the light-field data as the expected in-focus image of the target object, wherein the one image that is selected has better sharpness than other images from the set of images.

23. The method of claim 15, further comprising:

determining an optimized synthesized aperture based on an intensity of light received from the target object; and

using the optimized synthesized aperture to construct the expected in-focus image of the target object from the light-field data.

18-20. -20. (canceled)

21. A method of imaging a target object with an imaging reader, the method comprising:

detecting light from the target object through a lens arrangement with an image sensor to generate light-field data, wherein the image sensor comprises (1) an array of photosensitive elements and (2) an array of microlenses that overlays the array of photosensitive elements with a uniform spacing, wherein a microlens covers multiple photosensitive elements each receiving light through the microlens to function as a sub-pixel;

generating a stream of image data including image data representing an expected in-focus image of the target object, a stream of image data being generated from the light-field data;

constructing a reference image of the target object from the light-field data using a first focus plane as a corresponding focus plane;

comparing the reference image with an intensity distribution in the sub-pixels to selected one of a near focus plane, a far focus plane, and the first focus plane as a next focus plane, wherein the first focus plane is located between the near focus plane and the far focus plane; and

using the next focus plane to construct the expected in-focus image of the target object from the light-field data.

22. The method of claim 21, wherein said comparing the reference image with an intensity distribution in the sub-pixels comprises:

comparing direction of black-to-white transition between micro-lenses and sub-pixels.

24-26. -26. (canceled)