Two-dimensional imager with solid-state auto-focus

Patent metadata

Field	Value
Publication number	US-9253393-B2
Application number	US-201514641550-A
Country	US
Kind code	B2
Filing date	Mar 9, 2015
Priority date	Mar 28, 2011
Publication date	Feb 2, 2016
Grant date	Feb 2, 2016

Abstract

An imaging system having a solid-state auto focusing system advantageously images broadband light reflected from an object to be imaged using a lens objective having chromatic aberration, which focuses different colors of light at different focal planes. Using the color information in the focal planes in conjunction with an object distance determined by a range finder, a luminance plane is constructed that has a focused image of the object. The system provides the focused image of the object without the use of any moving parts.

First claim

The invention claimed is:

1. An imaging apparatus, comprising:
a broadband light source configured to illuminate an object to be imaged;
an objective lens module having an objective lens and a hologram lens configured to focus the broadband light reflected from the object, wherein the objective lens module has a chromatic aberration that separates focal planes of different wavelengths of light, each focal plane having a different magnification;
a two-dimensional image sensor configured to capture image data of the object;
a two-dimensional color filter array configured to filter light reflected from the object before reaching the image sensor, wherein the filtering comprises transmitting only one band of wavelengths at certain positions in the array, and at least two bands of wavelengths are transmitted over the array;
a range finder configured to determine a distance of the object from the image sensor; and
a processor configured to construct a luminance plane containing an image of the object by correcting the magnification of the images for each of the different wavelengths such that each image of the object has the same height.

2. The apparatus of claim 1 , wherein the color filter array is a Bayer filter, and the processor is further configured to perform a demosaicing algorithm to interpolate missing image data not transmitted by the color filter array.

3. The apparatus of claim 1 , wherein the chromatic aberration of the objective lens module focuses light at longer wavelengths more strongly than light at shorter wavelengths.

4. The apparatus of claim 1 , wherein the objective lens has a first dispersion and the hologram lens has a second dispersion, and the second dispersion is opposite in sign to the first dispersion.

5. The apparatus of claim 1 , wherein the imaging apparatus comprises a display for displaying the image of the object in the luminance plane.

6. The apparatus of claim 1 , wherein the processor decodes the image of the object in the luminance plane.

7. A method of auto-focusing an imaging system, the method comprising:
focusing broadband light reflected from an object to be imaged through a lens module having an objective lens and a hologram lens, wherein different wavelengths of light are focused at different focal planes, each focal plane having a different magnification;
filtering the focused light to determine contributions of light to one or more color planes;
capturing image data of the object, wherein the image data comprises the filtered focused light;
constructing a resultant plane for the captured image data;
correcting the magnification for each of the different wavelengths such that the object in each of the different wavelengths has the same height in the resultant plane; and
identifying the object imaged in the resultant plane, wherein the object imaged in the resultant plane is focused.

8. The method of claim 7 , wherein filtering the focused light comprises transmitting only one contiguous group of wavelengths at certain spatial locations within the image data, and at least two contiguous groups of wavelengths are transmitted within the captured image data.

9. The method of claim 7 , wherein filtering the focused light comprises:
using a filter array to filter the focused light;
performing a demosaicing algorithm to interpolate missing image data not transmitted by the filter array.

10. The method of claim 9 , wherein the filter array is a Bayer filter.

11. The method of claim 7 , wherein focusing the reflected light from the object comprises focusing longer wavelength light more strongly than shorter wavelength light.

12. The method of claim 7 , comprising displaying the image of the object in the resultant plane.

13. The method of claim 7 , comprising illuminating the object to be imaged using a broadband light source.

14. The method of claim 7 , comprising illuminating the object to be imaged using a white light emitting diode.

15. An imaging apparatus, comprising:
a lens module having an objective lens and a hologram lens for focusing broadband light reflected from an object to be imaged, wherein different wavelengths of light are focused at different focal planes, each focal plane having a different magnification;
a filter array for filtering the focused light to determine contributions of light to one or more color planes;
an image sensor for receiving image data of the object, wherein the image data comprises the filtered focused light;
a processor configured for:
constructing a composite plane for the captured image data;
correcting the magnification of the images for each of the different wavelengths such that each image of the object has the same height in the composite plane;
determining the object imaged in the composite plane, wherein the object imaged in the composite plane is focused.

16. The apparatus of claim 15 , wherein the filter array comprises a color filter array.

17. The apparatus of claim 16 , wherein the color filter array comprises a Bayer filter.

18. The apparatus of claim 15 , wherein the image sensor comprises a two-dimensional imaging array.

Assignees

• Intermec Ip Corp
• Intermec Ip Corp

Inventors

• Gillet Alain
• Thuries Serge

Classifications

• H04N25/58

  involving two or more exposures · CPC title

• H04N25/134

  based on three different wavelength filter elements · CPC title

• H04N25/587

  acquired sequentially, e.g. using the combination of odd and even image fields · CPC title

• H04N23/843

  Demosaicing, e.g. interpolating colour pixel values · CPC title

• H04N23/673 Primary

  based on contrast or high frequency components of image signals, e.g. hill climbing method · CPC title