Method and system for reducing effects of undesired signals in an infrared imaging system

• US 7,593,593 B2
• Filed: 06/16/2004
• Issued: 09/22/2009
• Est. Priority Date: 06/16/2004
• Status: Expired due to Fees

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Wilson, Andrew D.
• Primary Examiner(s): STREGE, JOHN B
• Application Number:
  US10/870,777
• Publication Number:
  US 20050281475A1
• Time in Patent Office: 1,924 Days
• Field of Search: 382/254, 348/241, 348/102, 348/162
• US Class Current: 382/275
• CPC Class Codes: G06F 3/0421 by interrupting or reflecting a light beam, e.g. optical touch-screen
• CPC Class Codes: G06V 40/107 Static hand or arm
• CPC Class Codes: H04N 23/56 provided with illuminating means
• CPC Class Codes: H04N 5/33 Transforming infrared radiation cameras or camera modules for generating image signals from infrared radiation H04N23/20; circuitry of SSIS for transforming infrared radiation into image signals H04N25/20

Abstract

Effects of undesired infrared light are reduced in an imaging system using an infrared light source. The desired infrared light source is activated and a first set of imaging data is captured during a first image capture interval. The desired infrared light source is then deactivated, and a second set of image data is captured during a second image capture interval. A composite set of image data is then generated by subtracting from first values in the first set of image data corresponding second values in the second set of image data. The composite set of image data thus includes a set of imaging where data all infrared signals are collected, including both signals resulting from the IR source and other IR signals, from which is subtracted imaging in which no signals result from the IR course, leaving image data including signals resulting only from the IR source.

Claims

1. A method for reducing an effect of an undesired infrared light source in an imaging system using a desired infrared light source and an image capture device that detecting emissions of both the undesired infrared light source and the desired infrared light source, the method comprising the steps of:

(a) positioning a desired infrared light source, an image capture device and a screening device, wherein the desired infrared light source, image capture device, and screening device are both positioned on a same, first side of a light permeable surface and in a manner that provides direct light communication between the light permeable surface with each of the desired infrared light source and the image capture device, the light permeable surface further having a second side on which one or more physical objects are detected, wherein the positioning includes positioning the infrared light source at a location closer to the light permeable surface than both the image capture device and the screening device, and positioning the screening device at a location closer to the light permeable surface than the image capture device, and wherein the screening substantially prevents any infrared light from the light source from entering the image capture device without first being directed to the light permeable surface;

(b) activating the desired infrared light source during a first image capture interval thereby causing the desired infrared light source to transmit infrared light at least partially through the light permeable surface;

(c) capturing, with the image capture device, a first set of image data during the first image capture interval, the first set of image data including image data of the one or more physical objects on the light permeable surface and which corresponds to both the desired infrared light source and an undesired infrared light source, the undesired infrared light source originating infrared light from a location on the second side of the light permeable surface;

(d) deactivating the desired infrared light source during a second image capture interval;

(e) capturing, with the image capture device, a second set of image data during the second image capture interval, the second set of image data corresponding to only the undesired infrared light source; and

(f) producing a composite set of image data of the one or more physical objects located on the second surface by subtracting from first values in the first set of image data, corresponding second values in the second set of image data, the resulting composite set of image data including only image data resulting from illumination generated by the desired infrared light source, thereby reducing the effect of the undesired infrared light source by considering both desired and undesired infrared light sources.

2. The method of claim 1, further comprising the step of controlling activation of the desired infrared light source with an image capture device, such that an image capture signal generated by the image capture device causes the desired infrared light source to be activated during the first image capture interval and deactivated during the second image capture interval.

3. The method of claim 1, wherein the first values in the first set of image data represent an intensity of infrared light captured for a plurality of points across the first side of the light-permeable surface during the first image capture interval while the desired infrared light source was activated, and the second values in the set of image data represent an intensity of infrared light captured for the plurality of points across the first side of the light-permeable surface during the second image capture interval while the desired infrared light source was deactivated.

4. The method of claim 3, wherein the subtracting from the first values in the first set of image data corresponding second values in the second set of image data is defined by:

D(x,y)=I_ON(x,y)−

I_OFF(x,y)

where;

(a) x,y represents a coordinate location of a point on the first side of the light-permeable surface;

(b) I_ON (x,y) represents an intensity of infrared light detected during the first image capture interval at the point x,y;

(c) I_0FF (x,y) represents an intensity of infrared light detected during the second image capture interval at the point x,y; and

(d) D (x,y) represents a net intensity of infrared light at the point x,y when the intensity of the infrared light captured at the point x,y during the second image capture interval is subtracted from the intensity of the infrared light captured at the point x,y during the first image capture interval.

5. The method of claim 1, further comprising the step of communicating the composite set of image data to an image processing system.

6. The method of claim 5, further comprising the step of using the infrared light reflected by the physical object to recognize a characteristic of the physical object.

7. The method of claim 1, further comprising the step of positioning a projector on the first side of the light-permeable surface such that light from the projector directed onto the light-permeable surface is used to present images visible on the opposite side of the light-permeable surface with which the physical object can interact.

8. The method of claim 1, wherein positioning the image capture device that provides direct light communication between the light permeable surface and the image capture device includes positioning the image capture device such that light reflected from the light permeable surface to the camera is not reflected off mirrors and such that such light reflected from the light permeable surface passes only through an infrared band pass filter.

9. A method for reducing an effect of unintended, undesired, and extraneous infrared light signals in a table-top infrared light vision system and without shielding the table-top infrared light vision system from all background infrared sources, the method comprising:

(a) within a table-top infrared light vision system, providing an interactive light permeable surface on which images are projected, the light-permeable surface having a first surface on an internal side of the light-permeable surface, and having a second surface on an opposing external side of the light-permeable surface;

(b) providing a projector and positioning the projector on the internal side of the light-permeable surface;

(c) positioning one or more mirrors on the interior side of the light-permeable surface, the one or more mirrors being positioned so as to reflect light from the projector onto the light-permeable surface;

(d) reflecting light projected from the projector of the one or more mirrors and onto the light-permeable surface to present images visible on the external side of the light-permeable surface;

(e) positioning an infrared video camera on the interior side of the light-permeable surface such that it receives images directly from the light-permeable surface and without being reflected off the one or more mirrors;

(f) positioning a desired infrared light source on the interior side of the light-permeable surface, the infrared light source being screened by a screening device from the video camera so as to substantially prevent any infrared light emitted from the desired infrared light source from entering the camera without first being directed to the light-permeable surface, wherein the desired infrared light source is positioned to emit desired infrared light directly to the light-permeable surface without being reflected off the one or more mirrors and is further positioned to be closer to the light-permeable surface than the screening device and the video camera, which screening device is positioned between the video camera and the desired infrared light source;

(g) selectively activating the desired infrared light source during a first image capture interval, and capturing, with the infrared video camera, a first set of image data for a pixelwise defined portion of the light-permeable surface, the first set of image data including infrared light intensity values of the first set of image data corresponding to background infrared light as well as infrared light emitted from the desired infrared light source through at least a portion of the light-permeable surface;

(h) selectively deactivating the desired infrared light source during a second image capture interval, and capturing, with the infrared video camera, a second set of image data for the pixelwise defined portion of the light-permeable surface, the second set of image data including infrared light intensity values at each pixel for the pixelwise defined portion of the light-permeable surface, the infrared light intensity values of the second set of image data corresponding to the background infrared light and excluding infrared light from the desired infrared light source; and

(i) producing a composite set of image data representing one or more physical objects touching the second surface of the light-permeable surface, by subtracting, on a pixel basis, infrared light intensity values of the second set of image data from corresponding infrared light intensity values of the first set of image data, the resulting composite set of image data including only light intensity values resulting from illumination of the one or more physical objects generated by the desired infrared light source.

10. The method of claim 9, wherein:

reflecting light projected from the projector of the one or more mirrors and onto the light-permeable surface to present images visible on the external side of the light-permeable surface includes reflecting light directed from the projector substantially directly toward the light-permeable surface off a first mirror, which first mirror reflects the light further from said light-permeable surface to a second mirror, which second mirror reflects the light onto the light-permeable surface;

the screening device is a baffle; and

producing the resulting composite set of image data is performed without regard to static ambient infrared measurements and/or initial calibration.