Optical system auxiliary input calibration arrangement and method of using same

• US 5,594,468 A
• Filed: 11/21/1994
• Issued: 01/14/1997
• Est. Priority Date: 11/07/1989
• Status: Expired due to Term

• Current Assignee: Straight Signals LLC (Intellectual Ventures LLC)
• Original Assignee: Proxima Corporation (Ask ASA)
• Inventors: Busch, Jeffrey W., Lizon, Richard M., Hauck, Lane T., Marshall, Roger N.
• Primary Examiner(s): Hjerpe, Richard
• Assistant Examiner(s): Wu, Xiao M.
• Application Number:
  US08/342,814
• Time in Patent Office: 785 Days
• Field of Search: 345/7, 345/8, 345/9, 345/157, 345/156, 345/158, 345/183, 345/182, 345/180, 345/87, 348/211, 348/221, 348/229, 348/744, 348/745, 348/746, 348/747, 359/142, 359/443, 359/448, 359/449, 434/323, 434/324, 434/325, 434/337
• US Class Current: 345/158
• CPC Class Codes: G06F 3/038 Control and interface arrangements therefor, e.g. drivers or device-embedded control circuitry
• CPC Class Codes: G06F 3/0386 for light pen
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment

Abstract

A method and optical system auxiliary input calibration arrangement accurately and reliably discriminate between a user generated image and a video source generated image, such as one produced by a computer. The calibration arrangement includes amplifier devices for increasing the strength of a video information signal indicative of the video generated image, and a user generated auxiliary input signal indicative of an auxiliary input light image, without increasing spurious ambient light signals. A discrimination circuit generates a detection signal whenever the amplified information signals are greater than a predetermined reference level signal. A microprocessor calculates the appropriate predetermined reference level signal based upon ambient lighting conditions, the strength of that portion of the information signal indicative of the video image, the type of optical system and the distance the optical system is disposed away from a viewing surface. The microprocessor controls the exposure time of the light sensing device and selects an appropriate level of amplification for the output signal from the sensing device to increase light sensitivity between the video source generated light images as compared to the user generated auxiliary light images. A dual beam light generating device produces a low intensity laser beam for helping a user locate a desire portion of the video generated image and a high intensity laser beam for providing auxiliary input light of the desired position of the image illuminated by the low intensity beam.

Claims

1. A system for controlling a projected video image with auxiliary control light projected onto a viewing surface reflecting the projected video image, comprising:

means for generating a bright calibration video signal indicative of the combination of the projected video image and background light to facilitate discriminating accurately the projected video image from the background light reflecting from the viewing surface, said video signal having a minimum value and a maximum value;

means for determining the minimum value of said bright calibration video signal above a given background light level to facilitate the elimination of a portion of said video signal indicative of the background light;

means for storing the determined minimum value to facilitate modifying said video signal above said given background light level thereafter to facilitate responding to the auxiliary control light projected onto the viewing surface;

means for adjusting the value of said bright calibration video signal from said maximum value to a lesser value, said lesser value being equal to the maximum value less the stored minimum value to generate a modified video signal indicative of the projected video image only, said modified video signal having another minimum value and another maximum value; and

means for adjusting the value of a reference level signal to be greater than said lesser value to distinguish a video signal indicative of an auxiliary control light image from a video signal indicative of the combination of the projected video image and background light to facilitate discrimination accurately the projected auxiliary control light from the projected video image light reflecting from the viewing surface;

whereby the auxiliary control light is enabled to control the projected liquid crystal display image when projected onto the viewing surface.

2. A system according to claim 1, comprising:

means for generating a low intensity auxiliary locating image for projecting onto the viewing surface to help a user locate a desired portion of the video image reflecting from the viewing surface;

means for generating said auxiliary light image being a high intensity auxiliary control image for projecting onto the viewing surface at substantially the same location as said location image was projected to enable the optical input system to detect the control image for calibration purposes; and

discrimination means for distinguishing said signal indicative of said control image from said reference level signal for display control purposes.

3. A system according to claim 2, further comprising:

means for causing the projected video image to change between a brightest image and a darkest image to help facilitate determining the maximum and minimum values of said modified video signal relative to the projected image; and

means for determining the maximum value of said modified video signal for helping to determine a value of said reference level signal sufficiently above the value of a modified video signal indicative of the combination of the low intensity locating image and the brightest image to prevent the optical input system from generating auxiliary control information in response to the system detecting the locating image on the viewing surface.

4. A system according to claim 3, further comprising:

means for storing expected boundary values of the projected video image for calibration purposes;

said expected boundary values being indicative of a range of maximum and minimum width and height values of projected images having a sufficient intensity to be detected by the optical input system;

means for determining the width and height values of the projected video image detected by the optical input system;

means for comparing the determined width and height values of the projected video image with said expected boundary values to determine if the optical input system is physically aligned with the viewing surface to detect the entire projected video image from the viewing surface; and

said input system being aligned when both the determined width and height values falls within the range of the expected maximum and minimum width and height values respectively.

5. A system according to claim 4, further comprising:

means for storing factors indicative of expected luminance levels associated with different types of image projection systems to facilitate determining the value of said reference level signal;

means for retrieving the stored factors to help determine the value of said reference level signal relative to the type of image projection system generating the projected video image; and

algorithm means for calculating the value of said reference level signal to distinguish said signal indicative of an auxiliary light image from said modified video signal to help the optical input system detect the control image on the viewing surface.

6. A system according to claim 5, wherein said discrimination means includes:

comparator means coupled to said reference level signal and to said modified video signal for generating a detection signal whenever the voltage of said modified video signal is greater than the voltage of said reference level signal.

7. A system according to claim 6, wherein said algorithm means includes a formula:

space="preserve" listing-type="equation">y=mx+b;

wherein y is a minimum voltage potential value for said reference level signal to enable said comparator means to distinguish between a modified video signal indicative of the combination of said low intensity image and the brightest image and a modified video signal indicative of the combination of said high intensity image and the darkest image;

wherein x is the potential difference between a bright image reference level signal and a dark image reference level signal;

wherein b is the potential value of said bright image reference level signal; and

wherein m is a constant indicative of a luminance level for one of a plurality of different kinds of image projection systems.

8. A system according to claim 7, wherein said means for decreasing includes:

means for changing the strength of said video signal to facilitate detection of the video image and the control image under different background light conditions; and

multiple gain means responsive to said modified video signal for changing the strength of said modified video signal to further facilitate detection of the video image and the control image under different background light conditions.

9. A system according to claim 3, wherein said means for determining includes gain level factor means responsive to a gain selection signal for determining a gain factor to adjust the value of said light information signal to a sufficient value to enable it to be compared with said reference level signal.

10. A system according to claim 9, wherein said means for determining further includes black level factor means responsive to a black level signal for determining a black level factor to eliminate substantially ambient background noise from an information signal including said auxiliary light information signals.

11. A system according to claim 10, wherein said mean for determining further includes reference level factor means responsive to a reference level signal to help distinguish between different types of auxiliary light information signals.

12. A system according to claim 11, wherein said mean for determining further includes:

means for generating said black level signal, said gain selection signal and said reference level signal.

13. A system according to claim 1, for use with means for generating video information signals to help produce said video image, further comprising:

means for determining the boundary values of said projected video image reflecting from the viewing surface; and

means coupled to the last mentioned generating means for converting said boundary values to video signal coordinate values to help facilitate changing said video image in response to said control image reflecting from the viewing surface at a user selected portion of the projected image.

14. A method for controlling a projected video image with auxiliary control light projected onto a viewing surface reflecting the projected video image, comprising:

generating a bright calibration video signal indicative of the combination of the projected video image and background light to facilitate discriminating accurately the projected video image from the background light reflecting from the viewing surface, said video signal having a minimum value and a maximum value;

determining the minimum value of said bright calibration video signal above a given background light level to facilitate the elimination of a portion of said video signal indicative of the background light;

storing the determined minimum value to facilitate modifying said video signal above said given background light level thereafter to facilitate responding to the auxiliary control light projected onto the viewing surface;

adjusting the value of said bright calibration video signal from said maximum value to a lesser value, said lesser value being equal to the maximum value less the stored minimum value to generate a modified video signal indicative of the projected video image only, said modified video signal having a minimum value and a maximum value; and

adjusting the value of a reference level signal to be greater than said lesser value to distinguish a video signal indicative of an auxiliary control light image from a video signal indicative of the combination of the projected video image and background light to facilitate discriminating accurately the projected auxiliary control light from the projected video image light reflecting from the viewing surface;

whereby the auxiliary control light is enabled to control the projected liquid crystal display image when projected onto the viewing surface.

15. A method according to claim 14, comprising:

generating a low intensity auxiliary locating image for projecting onto the viewing surface to help a user locate a desired portion of the video image reflecting from the viewing surface;

generating said auxiliary light image being a high intensity auxiliary control image for projecting onto the viewing surface at substantially the same location as said locating image was projected to enable the optical input system to detect the control image for calibration purposes; and

distinguishing said signal indicative of said control image from said reference level signal for display control purposes.

16. A method according to claim 15, further comprising:

causing the projected video image to change between a brightest image and a darkest image to help facilitate determining the maximum and minimum values of said modified video signal relative to the projected image; and

determining the maximum value of said modified video signal for helping to determine a value of said reference level signal sufficiently above the value of a modified video signal indicative of the combination of the low intensity locating image and the brightest image to prevent the optical input system from generating auxiliary control information in response to the system detecting the locating image on the viewing surface.

17. A method according to claim 16, further comprising:

storing expected boundary values of the projected video image for calibration purposes;

said expected boundary values being indicative of a range of maximum and minimum width and height values of projected images having a sufficient intensity to be detected by the optical input system;

determining the width and height values of the projected video image detected by the optical input system;

comparing the determined width and height values of the projected video image with said expected boundary values to determine if the optical input system is physically aligned with the viewing surface to detect the entire projected video image from the viewing surface; and

said input system being sufficiently aligned when both the determined width and height values falls within the range of the expected maximum and minimum width and height values respectively.

18. A method according to claim 17, further comprising:

storing factors indicative of expected luminance levels associated with different types of image projection systems to facilitate determining the value of said reference level signal;

retrieving the stored factors to help determine the value of said reference level signal relative to the type of image projection system generating the projected video image; and

calculating the value of said reference level signal to distinguish said signal indicative of an auxiliary light image from said modified video signal to help the optical input system detect the control image on the viewing surface.

19. A method according to claim 18, wherein said step of distinguishing includes:

generating a detection signal whenever the voltage of said video signal is greater than said reference level signal; and

wherein said step of calculating includes a formula;

space="preserve" listing-type="equation">y=mx+b

wherein y is a minimum voltage potential value for said reference level signal to enable comparator means to distinguish between a modified video signal indicative of the combination of said low intensity image and the bright image and a modified video signal indicative of the combination of said high intensity image and the dark image;

wherein x is the potential difference between a bright image reference level signal and a dark image reference level signal;

wherein b is the potential value of said bright image reference level signal; and

wherein m is a constant indicative of a luminance level for one of a plurality of different kinds of image projection systems.

20. A method according to claim 19, wherein said step of decreasing includes:

using video sensing means for generating said video signal, said video sensing means responsive to an exposure rate signal for changing the value of said video signal;

adjusting the exposure rate to change the strength of said video signal to facilitate detection of the video image under different background light conditions.

21. A method according to claim 20, further comprising:

setting said exposure rate signal initially to a minimum value;

determining whether said modified video signal is generated in response to said video signal;

increasing the value of said exposure rate signal by an incremental value when said modified video signal is not generated in response to said video signal; and

repeating the steps of setting, determining and increasing said exposure rate signal until said modified video signal is generated in response to said video signal.

22. A method according to claim 21, further comprising:

using gain means for changing the value of said video signal, said gain means responsive to a gain control signal for changing the value of said video signal;

setting said gain control signal initially to a maximum value;

determining whether said modified video signal is generated in response to said video signal when said exposure rate signal is set at a maximum value;

decreasing the value of said gain control signal by an incremental amount when said modified video signal is generated in response to said video signal;

repeating the steps of setting, determining and decreasing said gain control signal until said modified video signal is not generated in response to said video signal.

23. A method according to claim 22, further comprising:

determining whether said exposure rate signal is set at a maximum value;

determining whether said gain control signal is set at a maximum value;

generating an alarm indication when said modified value signal is not generated when said rate signal and said control signal are set to the maximum values;

setting said exposure rate signal to said minimum value when said modified video signal is generated when said rate signal and said control signal are set to their maximum values;

increasing said exposure rate signal by said incremental value;

determining whether said modified video signal is generated in response to said video signal;

repeating the last two mentioned steps until said modified video signal is generated in response to said video signal.

24. A method according to claim 23, further comprising:

using comparator means for generating an information signal to change the liquid crystal image reflecting from the viewing surface, said computer means being responsive to said modified video signal and to a reference level signal; and

setting said reference level signal to a minimum value.

25. A method according to claim 24, further comprising:

setting said reference level signal to a maximum value; and

generating a video signal indicative of a bright image.

26. A method according to claim 25, further comprising:

determining whether said information signal is generated in response to said video signal;

decreasing the value of said reference level signal by a large incremental value when it is determined said information signal is not generated;

repeating the last two mentioned steps of determining and decreasing until said information signal is generated;

increasing the value of said reference level signal by said large incremental value;

storing the value of said reference level signal;

decreasing the value of said reference level signal by a small incremental value;

determining whether said information signal is generated;

repeating the last two mentioned steps until said information signal is generated; and

storing the value of said reference level signal as a bright image reference level.

27. A method according to claim 26, further comprising:

setting said reference level signal to a maximum value; and

generating a video signal indicative of a dark image.

28. A method according to claim 27, further comprising:

determining whether said information signal is generated in response to said video signal;

decreasing the value of said reference level signal by a large incremental value when it is determined said information signal is not generated;

repeating the last two mentioned steps of determining and decreasing until said information signal is generated;

increasing the value of said reference level signal by said large incremental value;

storing the value of said reference level signal;

decreasing the value of said reference level signal by a small incremental value;

determining whether said information signal is generated;

repeating the last two mentioned steps until said information signal is generated; and

storing the value of said reference level signal as a dark image reference level.

29. A system for calibrating an optical computer input system to facilitate the modifying of a video image generated by computer means displayed by display means and projected onto a viewing surface by projection means, comprising:

light sensing means having a field of view that is substantially larger than said video image reflecting from the viewing surface and being mounted for movement relative to the viewing surface and the projection means so that said field of view is able to capture all of the video image reflecting from the viewing surface for generating a reflected light information signal indicative of the luminance levels of the light images reflecting from the viewing surface;

signal processing means coupled to the computer and said light sensing means for converting said reflected light information signal into computer coordinate information to modify the video image generated by the computer means;

signal calibration means for automatically adjusting the strength of said reflected light information signal for different background lighting conditions to enable said signal processing means to accurately process said signal so that it is reliably converted into computer coordinate information to modify the video image generated by the computer means;

said signal calibration means including discrimination means for facilitating comparing signals indicative of a plurality of light images having a plurality of different luminance levels reflecting from the viewing surface; and

microprocessor means for controlling said discrimination means to enable the comparison between light images indicative of said video image reflecting from the viewing surface and light images indicative of externally generated spots of control light reflecting from the viewing surface;

wherein the reflected light images indicative of said video image having different luminance levels ranging between a maximum luminance level and a minimum luminance level.

30. A system according to claim 29, wherein said signal calibration means further includes:

signal amplifying means for increasing the strength of the reflected light information signal to facilitate discriminating between signals indicative of the various light images reflecting from the viewing surface;

wherein the reflected light images indicative of said video image having different luminance levels ranging between a maximum luminance level and a minimum luminance level; and

wherein the reflected light images indicative of said control light have at least two different luminance levels to help facilitate directing the control light to desired locations on the video image without generating said reflected light information signal.

31. A system according to claim 30, wherein the projection means has optical properties for projecting the video image through a particular optical path onto the viewing surface to be reflected therefrom;

and

wherein said viewing surface is disposed in a room having ambient light therein;

said optical properties of the projection means in combination with the ambient light and the distance the viewing surface is disposed from the projection means causing the light images reflecting from the viewing surface to have maximum and minimum luminance levels relative to one another;

wherein said microprocessor means includes reference level signal means for generating a reference level signal and a black level signal to help facilitate discrimination between signals indicative of the various light images reflecting from the viewing surface; and

wherein said discrimination means includes comparator means responsive to said reference level signal to enable the accurate comparison of the various light images reflecting from the viewing surface relative to ambient light conditions and the optical properties of the projection means.

32. A system according to claim 31, wherein said at least two different luminance levels including a positioning luminance level that will not be processed as being indicative of a control signal to modify the video image and a processing luminance level that will be processed as being indicative of a control signal to modify the video image.

33. A system according to claim 32, wherein said microprocessor means includes exposure time means for generating an exposure time signal to help said light sensing means to generate said reflected light information signal, said exposure time signal having a maximum duration time period and a minimum duration time period to permit the duration of said light information signal to be controlled for signal processing purposes;

wherein said light sensing means is responsive to said exposure time signal to enable said light information signal to be generated in response to light images of a given luminance level;

wherein said microprocessor means includes signal strength means for generating a gain selection signal to control the strength of said reflected light information signal for signal processing purposes; and

wherein said signal amplifying means is responsive to said given selection signal to enable discrimination between the signals indicative of the various light images reflecting from the viewing surface.

34. A system according to claim 33, wherein said microprocessor means includes a plurality of calibration algorithms to help facilitate the alignment of said light sensing means relative to the proper detection of said reflected video image and said reflected control image when it is superimposed on said reflected video image.

35. A system according to claim 34, wherein said plurality of calibration algorithms includes:

field of view algorithm means for user interactive alignment of the light sensing means under normal ambient light and harsh ambient light conditions; and

light sensitivity algorithm means for adjusting the light sensitivity of said signal calibration means to facilitate detection and tracking of certain ones of the externally generated spots of control light reflecting from the viewing surface.

36. A system according to claim 35, wherein said field of view algorithm means includes:

signal detection means responsive to said light information signal for selecting the duration of said exposure time signal, said exposure time signal being incremental relative to said gain selection signal from said minimum duration time period to a duration time period sufficient to cause said light sensing means to generate an output signal of sufficient magnitude to permit signal processing and for causing the gain selection signal to be increased from a minimum gain selection level to a maximum gain selection level for each selected duration of the exposure time signal until said light sensing means generates said output signal of sufficient magnified to permit signal processing.

37. A system according to claim 36, wherein said field of view algorithm means further includes reference level means for selecting a desired one of a plurality of different reference level sufficient to enable said output signal to be discriminated;

said desired reference level being set at about zero to enable the selection of exposure time and gain selection signal levels.

38. A system according to claim 37, wherein said microprocessor means includes storage means for storing camera coordinate information indicative of the size of a captured video image and for storing predetermined camera coordinate information indicative of expected maximum and minimum camera coordinate values of the video image reflecting from the viewing surface.

39. A system according to claim 35, wherein said light sensitivity algorithm includes:

reference level factor means responsive to said reference level signal for determining a reference level factor to help distinguish between different types of auxiliary light information signals;

black level factor means responsive to said black level signal for determining a black level factor to eliminate substantially ambient background noise from an information signal including said auxiliary light information signals; and

gain level factor means responsive to gain selection signal for determining a gain factor to adjust the value of said light information signal to a sufficient value to enable it to be compared with said reference level signal.