Touch screen rear projection display

A touch screen display includes a diffuser screen, a projector, a camera, an infrared (IR) light source, and a controller. The diffuser screen has a front surface and a rear surface. The projector is disposed to project images onto the rear surface of said diffuser screen, and the images are visible to a user through the diffuser screen. The camera is disposed behind the diffuser screen and aimed to capture images of a pointer near the front surface of the diffuser screen. The IR light source is disposed to direct IR light toward the rear surface of the diffuser screen, so the rays of incident IR light form an acute angle with respect to the rear surface of the diffuser screen, and so that any of the incident IR light reflected off the rear surface of the diffuser screen does not enter the camera.

BACKGROUND OF THE INVENTION

Field of the Invention

This invention relates generally to touch screen displays, and more particularly to rear projection touch screen displays.

Description of the Background Art

Touch screen displays are known. A typical touch screen includes a display surface upon which images are displayed. Touch screens additionally include a means of detecting the position of a pointer (e.g., a stylus, the finger of a user, etc.) when the pointing object comes into contact with the display surface.

One means of detecting the position of the pointer is to capture an image of the pointer through the display surface. For example, a display can include an infrared (IR) camera positioned behind the display surface and focused to capture an image of the display surface. When software analyzing the captured images detects the presence of “spot” on the display surface, the “spot” is presumed to be caused by the pointer, and the location of the spot is taken as user input (e.g., the selection of an object displayed at the determined location of the pointer).

In order to make the image of the pointer more distinguishable, some systems employ an IR light source. The IR light source is positioned behind the display surface and emits IR light toward the display surface at a relatively low angle of incidence (e.g., close to normal) to illuminate the pointer through the display surface. Although, illumination of the pointer can improve the contrast of the captured images, IR light reflected off of the back of the display surface can significantly reduce the contrast of the captured images.

What is needed, therefore, is a touch screen display wherein the images of a pointer through a display screen are easier to discern. What is also needed is a touch screen display that facilitates the illumination of a pointer through the display surface without subjecting the camera to light reflected off of the back of the display surface.

SUMMARY

The present invention overcomes the problems associated with the prior art by providing a touch screen display with a light source disposed to direct light at the rear surface of a diffuser screen at an acute angle. The invention facilitates the illumination of a pointer near the front surface of the diffuser screen, while preventing light reflecting off of the rear surface of the diffuser screen from entering a camera disposed behind the diffuser screen.

An example touch screen display includes a diffuser screen, a projector, a camera, an infrared (IR) light source, and a controller. The diffuser screen has a front surface to be viewed by a user and a rear surface. The projector is disposed to project images onto the rear surface of said diffuser screen, and the images are visible to the user through the diffuser screen. The camera is disposed behind the diffuser screen and aimed to capture images of a pointer near the front surface of the diffuser screen. The IR light source is disposed to direct IR light toward the rear surface of the diffuser screen, so the rays of incident IR light form an acute angle with respect to the rear surface of the diffuser screen, and so that any of the incident IR light reflected off the rear surface of the diffuser screen does not enter the camera. The controller is operative to control the projector and responsive to the images of the pointer near the front surface of the diffuser screen, which indicate user selections.

In a particular embodiment, the touch screen display additionally includes a support structure. The support structure includes a front portion, a rear portion, and a side portion. The front portion is coupled to the diffuser screen. The rear portion of the support structure is disposed opposite the diffuser screen, and the camera is mounted at the rear portion. The side portion extends between an edge of the rear portion and an edge of the front portion, and the IR light source is mounted adjacent the side portion. In the disclosed embodiments, the IR light source is disposed closer to the front portion of the support structure than to the rear portion of the support structure.

The support structure additionally includes a second side portion extending between an opposite edge of the rear portion and an opposite edge of the front portion. A second IR light source is coupled to the second side portion, so that the rays of incident IR light from the second IR light source form an acute angle with respect to the rear surface of the diffuser screen, and so that any of the incident IR light from the second IR light source that is reflected off of the rear surface of the diffuser screen does not enter the camera. The second IR light source is also disposed closer to the diffuser screen than to the rear portion of the support structure.

In another example touch screen display, the IR light source is disposed adjacent the rear surface of the diffuser screen near an edge of the diffuser screen. The diffuser screen has a width and a length, and the length is greater than the width. The IR light source includes a plurality of IR light sources disposed adjacent the rear surface of the diffuser screen and distributed along a long edge of the diffuser screen. Optionally, the IR light source includes a plurality of IR light sources disposed adjacent the rear surface of the diffuser screen and distributed along both long edges of the diffuser screen. In an even more particular example embodiment, the IR light source includes a second plurality of IR light sources disposed adjacent the rear surface of the diffuser screen and distributed along both short edges of the diffuser screen.

In another embodiment, the diffuser screen has two long edges and two short edges, and the IR light source is disposed at one of the short edges. Optionally, a second IR light source is disposed at the other of the short edges.

In the disclosed embodiments, the diffuser screen has a length and a width, and the length is at least ten times the width. In a particular embodiment, the length is twelve times the width.

Another touch screen display includes a diffuser screen, a display, an image capture device, a light source, and a controller. The diffuser screen has a front surface to be viewed by a user and a rear surface. The display is visible to the user through the diffuser screen. The image capture device is disposed behind the diffuser screen and is configured to capture images of a pointer near the front surface of the diffuser screen. The light source emits light in the sensitivity range of the image capture device and is disposed adjacent the rear surface of the diffuser screen at an edge of the diffuser screen. The light source directs light toward the rear surface of the diffuser screen to illuminate the pointer through the diffuser screen. The controller is operative to control the projector and is responsive to the images of the pointer near the front surface of the diffuser screen.

The image capture device has an optical axis, and light emitted from the light source intersects the optical axis of the image capture device. At least a portion of the light emitted from the light source travels in a direction perpendicular to the optical axis of the image capture device. The light emitted from the light source and reflected off the rear surface of the diffuser screen is directed away from the image capture device.

DETAILED DESCRIPTION

The present invention overcomes the problems associated with the prior art by providing a touch screen display with a light source disposed to direct light at the rear surface of a diffuser screen at an acute angle. In the following description, numerous specific details are set forth (e.g., the position of cameras and projectors within the touch screen display) in order to provide a thorough understanding of the invention. Those skilled in the art will recognize, however, that the invention may be practiced apart from these specific details. In other instances, details of well known electronic assembly practices (e.g., touch screen display assembly, camera mounting, projector alignment, etc.) and components (e.g., chassis, housing, etc.) have been omitted, so as not to unnecessarily obscure the present invention.

FIG. 1is front view of a touch screen, rear projection display100. Display100is useful, for example, for interacting with customers in supermarkets. In this example supermarket embodiment, the display size is 4″×48″. Display100can be fixed on or under shelve that display products for sale. It should be understood, however, that the invention is not limited to this or any other particular size. Indeed, the display can have any dimensions that are suitable for any particular application.

A projection display (not visible in the view ofFIG. 1) projects an image on a screen101from the rear side (opposite to a customer) of screen101. In the present example, screen100displays images corresponding to a plurality of products including a first product102, a second product104, a third product106, and other products not explicitly shown in the view ofFIG. 1. The customer can use his finger108as a pointer to touch or closely point to any of the products displayed on screen101to select that product. For example, in response to the user selecting first product102on screen101, the projection display can project a new image on screen101, which provides information about first product102. The customer may continue to interact with touch screen display100by touching or closely pointing his finger108to any selections displayed on screen100. The user's interaction with touch screen display100is substantially similar to a user's interaction with any other touch screen device such as a computer, a tablet, a mobile phone, etc. In particular, the user can navigate through many screens of available information by selecting (pointing to) certain images on the screen101.

FIG. 2Ais a block diagram of touch screen display100ofFIG. 1. In particular, touch screen display100is an infrared (IR) touch screen rear projection display. Touch screen display100includes a housing202, a projection display204, a diffuser screen206, a Fresnel lens screen208, an IR light source210, an IR camera212, an IR pass filter214, and a controller216.

Projection display204is disposed within housing202and projects an image on diffuser screen206. Fresnel lens screen208(optional) is disposed adjacent the front surface of diffuser screen206(i.e., on the viewer's side of diffuser screen206and opposite to projection display204). Fresnel lens screen208further spreads the light diffused by diffuser screen206for better viewing of the image projected by projection display204. Projection display204can be a custom made projection display having an LCOS (liquid crystal on silicon) display panel (not shown). The aspect ratio of the LCOS display panel can be the same as the aspect ratio display screen101. Alternatively, as shown inFIG. 2B, the aspect ratio of an LCOS display panel228can be different than the aspect ratio of screen101, and projection display204can use only a subset230of the pixels232of LCOS display panel228having the same aspect ratio as display screen101. In either case, the size of the image projected by projection display204can correspond to the size of screen101.

IR light source210emits IR light220illuminating diffuser screen206and Fresnel lens screen208. A portion215of illuminating IR light220transmits through diffuser screen206and Fresnel lens screen208, because diffuser screen206and Fresnel lens screen208are transparent at the wavelength of IR light220emitted by IR light source210. IR light source210can be an LED or any other light source now known or yet to be developed. Another portion224and226of IR light220is reflected off of the back surface of diffuser screen206.

Camera212is disposed within housing202behind diffuser screen206and directed toward diffuser screen206to capture images of finger108(or any other pointer) near the front surface diffuser screen206. An IR pass filter214is disposed in front of camera212to let IR light220pass through filter214and into camera212. IR pass filter214blocks light of wavelengths different than IR light220(e.g., visible light) to prevent such light from entering into camera212. Alternatively, camera212is specifically an IR camera, and IR pass filter214might not be necessary and can therefore be omitted.

Touch screen100includes a support structure, for example housing202and/or a chassis (not shown). Camera212and projection display204are positioned at a rear portion of the support structure (e.g., coupled to the rear wall of housing202or a nearby portion of a chassis. A front portion of the support structure is coupled to the diffuser screen. Side portions of the support structure extend between respective edges of the rear portion and respective edges of the diffuser screen. IR light source210is mounted adjacent one of the side portions of the support structure near the diffuser screen.

IR light source210is positioned so that IR light220emitted by IR light source210does not directly enter camera212. As shown inFIG. 2A, the rays of illuminating IR light220intersect an optical axis221of camera212and are not directed into the optical aperture (not shown) of camera212. In addition, IR light source210is positioned so that the rays226of IR light220reflecting off of the rear surface of diffuser screen206are not directed into the optical aperture of camera212. As shown inFIG. 2A, edge ray213reflecting off of diffuser screen206intersects optical axis221in front of camera212and does not enter the aperture of camera212. Thus, the direction and the shadow of illuminating IR light220is determined by the position and direction of IR light source210, such that camera212is in the shadow of illuminating IR light220. Because no reflected or directly transmitted IR light enters to camera212, camera212detects a dark background.

Positioning IR light source near an edge of diffuser screen206facilitates the illumination of the majority of diffuser screen206, while still preventing IR light220reflected off of the rear surface of diffuser screen206from entering camera212. In this example embodiment, IR light source210is disposed on a side wall of housing202near diffuser screen206. IR light source210is not disposed next to camera212, which is disposed on a rear wall of housing202, because a portion of IR light emitted by IR light source210would be reflected off of the back surface of diffuser screen206and enter through the aperture of camera212. In contrast, in this example embodiment, IR light220reflected off of the rear surface of diffuser screen206does not enter camera212.

Position IR light source210near an edge of diffuser screen206is contrary to conventional wisdom in the art. However, preventing any IR light220reflected off of the rear surface of diffuser screen206from entering camera212provides a darker background and thereby improves the contrast of the captured images of finger108(or other pointers) through diffuser screen206.

Controller216provides overall coordination and control for touch screen display100. Controller is electrically coupled to projection display204and camera212. Controller216provides image data to projection display204corresponding to images to be displayed on diffuser screen206. Controller216also analyzes images captured by camera212to determine if a user has selected a particular image being displayed. Responsive to a determination that a user has selected a particular image, controller216can provide new image data to projection display204corresponding to the user's selection. Controller216can include sufficient memory to store all images to be displayed on diffuser screen206, or controller can have a wired or wireless communication link with an external device to provide image data and programing updates as needed.

FIG. 2Cis a block diagram of the touch screen display ofFIG. 1with a pointer (finger108) near the front surface of Fresnel lens screen208scattering infrared (IR) light. Finger108of a customer (not shown) is touching or closely pointing to Fresnel lens screen208(or diffuser screen206if there is no Fresnel lens screen208). A portion of illuminating IR light220transmitted through diffuser screen206and Fresnel lens screen208illuminates finger108. Finger108reflects a portion IR illuminating light220, which becomes reflected IR light222. Some of reflected IR light222passes through IR pass filter214and is detected by camera212. In other words, camera212captures a bright image of finger108against a dark background. Controller216analyzes the captured images to determine the relative position of finger108and provides image data to projection display204accordingly.

FIG. 3is a rear view of diffuser screen206, as viewed by camera212. Camera212is focused at or near diffuser screen206. The viewed image includes a bright spot302, which is finger108that scatters IR light, on a darker back ground304. As indicated above, diffuser screen206provides a dark background, because diffuser screen206is transparent to the IR illumination light220and IR light220reflected off of the rear surface of diffuser screen206is directed away from camera212. In this manner, the position of finger108can easily be detected by camera212. Thus, finger108may be used as a pointing device to operate a system including camera212, projection display204, and controller216(e.g., a stand-alone computer, a network attached computer, etc.). The interconnections between controller216, camera212, and projection display204can be wired or wireless.

FIG. 4is a block diagram of an alternate touch screen display400. Projection display400is substantially similar to projection display100ofFIGS. 1-2C, except that touch screen display400includes two IR light sources210A and210B, which emit illuminating IR light220A and220B, respectively. In this manner, diffuser screen206and Fresnel lens screen208are more evenly illuminated. IR light sources210A and210B may be LEDs or any other light sources now known or yet to be developed.

Similar to IR light source210of touch screen display100, both IR light sources210A and210B are positioned and directed so that any of IR light212A and212B reflected off of the rear surface of diffuser screen206does not enter camera212. Instead, any reflected IR light212A and212B is directed away from camera212.

FIG. 5Ais a block diagram (top view) of another alternate touch screen display500. Projection display500is similar to projection display100ofFIGS. 1-2C, except that projection display500does not use IR light source210, which is disposed on a side of the inner wall of housing202. Instead, projection display500uses an IR light source502, which is disposed adjacent the bottom edge of diffuser screen206, as illustrated inFIGS. 5A, 5B, and 5C. IR light source502emits an illuminating IR light504.

FIG. 5Bshows an IR light source502disposed adjacent diffuser screen206of touch screen display500. The view ofFIG. 5Bis from behind diffuser screen206(from the inside of housing202). In this example embodiment, IR light source502is disposed adjacent to the bottom edge of diffuser screen206. IR light source502may be a line light source or a plurality of discrete light sources such as LEDs or the like. Optionally, a similar IR light source506(line light source or plurality of discrete light sources) can disposed adjacent the top edge of diffuser screen206in addition to or instead of IR light source502. As yet another option, additional IR light sources can be distributed along the short edges of diffuser screen206in addition to IR light sources502and506, which are distributed along the long edges of diffuser screen206.

In this embodiment, similar to previously described embodiments, IR light source502and IR light source504(if present) are both positioned and directed so that any of IR light504reflected off of the rear surface of diffuser screen206does not enter camera212. Instead, any reflected IR light504is directed away from camera212.

FIG. 5Cis a partially sectioned side view (side of housing202removed) of the front portion of touch screen display500. IR light source502is disposed adjacent the lower edge of diffuser screen206, and emits an illuminating IR light504. A portion of illuminating IR light504transmits through diffuser screen206and Fresnel lens screen208, and another portion of IR light504reflects off of the rear surface of diffuser screen206. However, as described above, IR light source502is disposed so that none of the reflected light enters camera212(FIG. 5A).

FIG. 6is a block diagram of another alternate touch screen display600. To capture a wide field of view, for example an aspect ratio 4:48 or 1:12, a specially designed wide angle lens might be required. Accordingly, a specially designed wide angle lens (not shown) can be used in camera212(FIG. 2A). Alternatively, a plurality of cameras can be used. Each camera captures a portion of the field of view. Then, the captured fields of view are combined by a computer (e.g., controller602) to assemble a field of view with an aspect ratio of 1:12.

IR touch screen rear projection display600is identical to projection display200ofFIGS. 2A and 2C, except two cameras212A and212B in combination with IR pass filters214A and214B, respectively, are used instead of a single camera. In this manner, a wide field of view may be divided into two fields of view having smaller view angles. Each smaller field of view is captured by a respective one of cameras212A or212B. Controller602is substantially similar to controller216(FIG. 2A), except that controller602includes additional code/functionality to combine the two separate fields of view. It should be understood that “combining” the fields of view does not require a physical combination of the images, only that the positional relationships between the images be known so that controller602can determine the location of finger108by analyzing the images.

Alternate embodiments are not limited to two cameras. Indeed, any number of cameras may be used depending on the particular application and/or screen aspect ratio.

The description of particular embodiments of the present invention is now complete. Many of the described features may be substituted, altered or omitted without departing from the scope of the invention. For example, alternate configurations of IR light sources (e.g., a ring shaped IR light source encircling diffuser screen206) may be substituted for the IR light sources shown. As another example, embodiments of the invention can employ cameras and light sources that operate at wavelengths outside of the IR spectrum. These and other deviations from the particular embodiments shown will be apparent to those skilled in the art, particularly in view of the foregoing disclosure.