US 4,198,623 AGrant
Touch Entry Interactive Cathode Ray Tube Arrangement
Issue Date:1980-04-15
•7 Claims
•5 Drawing Sheets
Abstract
A display employing a horizontal and vertical grid of parallel infrared light beams in front of a cathode ray tube (CRT) face wherein a finger or other object may be placed against the face of the CRT to mark a spot thereon and the spot so marked will be detected by the interrupted beams. Infrared sources and detectors are located around the periphery of the CRT face and operate in different planes to more closely follow the curvature of the CRT face and thereby minimize parallax errors.
Metadata
Assignee
- Sanders Associates, Inc.
Inventors
- Victor A. Misek
- Albin A. Hastbacka
- Robert J. Beairsto
- Alphonse J. Trasatti
Application Information
Application Number:US 9601422
Filing Date:1978-11-13
Priority Date:1978-11-13
Art Unit:234
Classifications
IPC:
G08C 2100
Field of Search:
340178250364365 P;71218203 CT;549;548742;855
Patent Drawings (5 sheets)
Description
Field of Invention
This invention relates to interactive cathode ray tube (CRT) displays and more particularly to apparatus for indicating a point on the face of the CRT.
Background of the Invention
The use of CRT video display terminals as interfaces to computers has expanded rapidly in the past decade. Keyboards, light pens, joy sticks, and other devices have been used in conjunction with these video display terminals to allow the operator to interface with a host computer in order to enter, edit and select information, prepare engineering designs and many other applications which are too numerous to list. All these interactive video display terminal applications require a physical element such as the keyboards, light pens and joy sticks mentioned above to provide the interaction, but these devices may be cumbersome or otherwise undesirable depending upon specific applications.
Accordingly, in many applications it has been found desirable to provide an arrangement whereby a display operator may interface with a host computer by merely touching the face of the CRT with a finger or other object. This requires sensor arrangements that can accurately determine the point on the face of a CRT that is being touched by a finger.
An arrangement in the prior art for providing this feature utilizes a matrix of intersecting light beams which are all located in one plane in front of a CRT face. However, in the industry, curved face CRTs are used very widely to minimize focus and other problems inherent to flat face CRTs. With curved face CRTs and beams lying in one plane, parallax problems arise which have been objectionable enough that light beam techniques have never been accepted in the industry. With a curved face CRT a light beam is close to the CRT face at the middle of the display area but is spaced further from the face nearer the edges of the screen. Due to parallax caused by this spacing finger or other object not oriented vertically to the CRT face then interrupts a light beam not related to the spot on the screen being touched. This causes operational errors. Accordingly, the use of intersecting light beams has never been accepted in the industry.
Thus, there still exists a need in the art for an arrangement whereby a person may interact with a computer without special equipment such as light pens and without having errors due to factors such as parallax.
Summary of the Invention
In accordance with the teaching of our invention we provide a curved face CRT display coupled to a computer and the equipment operator may interact with the computer by merely touching the face of the CRT with, for example, a finger to perform many functions limited only by the imagination of the programmer who writes the operational software for the system.
Our invention utilizes infrared light sources mounted around the edges of and located close to the curved CRT face. The beam from each source along an edge lies in a first plane and is adjusted to be tangent to but not touching the face of the screen on a first half of the CRT face closest to the last mentioned edge. It can be recognized that these same beams pass further and further from a convex CRT face as they pass over the half of the CRT face furthest from the last mentioned edge. This increasing spacing of the beams from a curved CRT face causes a bad parallax problem which has never been solved. To solve this problem we provide infrared light sources along the opposite edge of the CRT face adjacent the second half of the screen. The beams from the last named sources only pass tangent to the screen over the second half of the screen. Thus, each beam is relatively close to one half of the face of the CRT. This is repeated for the remaining two edges of the screen.
As the face of the CRT is touched, two horizontal beams are interrupted, one close to the CRT face and the other spaced from the CRT face. At the same time two vertical beams are interrupted one close to and one spaced from the CRT face. A programmed microprocessor then utilizes the addresses of the interrupted vertical beams to determine which horizontal interrupted beam is closest to the CRT face at the point touched and the other horizontal interrupted beam is ignored. The same process is repeated utilizing the addresses of the interrupted horizontal beams to determine which interrupted vertical beam is closest to the CRT face at the point touched. The other interrupted vertical beam is ignored. Using the addresses of the interrupted horizontal and vertical beams closest to the CRT face at the point touched, the microprocessor accurately identifies the point being touched despite the finger or other object not being vertical to the face of the screen.
Our invention will become more apparent upon reading the following detailed description in conjunction with the drawing in which:
FIG. 1 shows the spatial relationship of infrared sources spaced around a CRT with respect to the curved face thereof;
FIG. 2 shows the spatial relationship of infrared sources spaced around three of four sides of a curved face CRT as is described herein as the preferred embodiment of the invention;
FIGS. 3 and 4 show a block diagram schematic of our invention; and
FIG. 5 is a timing diagram of signal waveforms in our invention.
Detailed Description
In accordance with the teaching of our invention, we utilize parallel vertical and parallel horizontal infrared light beams but no parallax problems occur with a curved CRT face. To achieve this goal we utilize a multiplicity of infrared sources (Light Emitting Diodes) located around the periphery of the CRT face and we also utilize a like multiplicity of infrared detectors also located around the periphery of the CRT face. These infrared sources (LEDs) and detectors cooperate in pairs.
On each of the four sides of a rectangular face CRT, the infrared sources are located close to the CRT face and are spaced along the side of the tube. The beams from the last named sources are parallel to each other and are coplanar. With the infrared sources being close to the CRT face their beams are tangent to but not touching the half of the CRT face closest to these sources. This orientation is seen in FIGS. 1 and 2 of the drawing. As may also be seen in FIGS. 1 and 2 the beams are spaced further from the screen as they pass over the half of the convex CRT face furthest from the particular infrared sources. As these beams pass over the furthest half of the screen the beams are spaced from the screen by an amount depending on the face curvature of the particular CRT utilized.
It should be noted in FIGS. 1 and 2 that the infrared sources on the remaining two opposing sides of the CRT face are similarly oriented and the previous discussion also applies thereto. The result, as may be seen in FIGS. 1 and 2, is that the planes in which the infrared beams lie on opposing sides of the rectangular CRT face are not coplanar.
The infrared detectors which detect the presence of an infrared beam from a corresponding one of the infrared sources are necessarily spaced from the CRT face as shown in FIGS. 1 and 2 in order to intercept the beam.
As is obvious after understanding the physical non-coplanar orientation of the infrared light beams originating from more than one side of the CRT face, a finger or other object touching the face of the CRT must interrupt more than one infrared beam. For beams originating from two opposing sides of the CRT screen a finger will interrupt one beam close to the CRT face and one beam spaced from the CRT face. This will also occur for two beams originating from the remaining two opposing sides of the CRT screen face. Thus, a maximum of four beams are interrupted. In the embodiment of our invention disclosed herein in detail, however, infrared sources are only located on the left, bottom and right sides of the CRT screen as shown in FIG. 2. Accordingly, infrared detectors are located on the left, top and right sides of the CRT screen. It was chosen to put the vertical oriented detectors on the top to minimize ambient light effects on these detectors.
With this preferred embodiment a finger or other object touching the screen will interrupt three infrared beams; two horizontal oriented non-coplanar beams, one of which lies close to the face of the CRT and the other of which is spaced from the face of the CRT at the point touched, and one vertical beam passing over the point touched and tangent to the center of the CRT face. It can easily be recognized that parallax problems will most likely occur with reference to the interrupted horizontal beam that is spaced furthest from the CRT face. In accordance with the teaching of our invention our novel equipment detects and identifies the interrupted vertical and two horizontal beams and then determines which horizontal beam is spaced farthest from the face of the CRT. It is the farthest spaced interrupted beam that is then ignored to minimize the parallax problem. The identification of the intercepted horizontal beam closest to the CRT face is used to indicate the vertical coordinate of the point on the CRT face that is being touched.
As described previously, two vertical beams may be utilized and, in the manner just described for two horizontal beams, the horizontal coordinate of the point on the CRT face being touched is determined. However, as further described, in the embodiment of our invention described herein infrared sources are only located along the bottom edge of the CRT screen with corresponding infrared detectors being located along the top edge of the screen. This embodiment allows for increased parallax but this is deemed acceptable in the particular application as horizontal rows of alpha-numeric characters are marked with a finger rather than individual points on the CRT face. If finer horizontal resolution is required, infrared sources should be located at both the top and bottom of the screen.
In the embodiment disclosed herein sixty-four collimated infrared sources are described for ease of representation. The exact number utilized may vary and a greater number are to be used for finer resolution of the point on the CRT face being touched. Twenty collimated infrared sources are located along each of the left and right hand edges of the screen and twenty-four sources are located along the bottom edge, with the sources along each edge being equispaced. As previously described, the sources are located near the CRT face as shown in FIG. 2 and the beams from all sources along each edge of the CRT face are parallel to each other and lie in the same plane. However, due to the curved face of the CRT, the beams originating from each edge of the CRT face are coplanar but each plane is non-coplanar with the other planes.
The infrared sources are then sequentially and periodically energized by circuitry described hereinafter and the output of the corresponding ones of the infrared detectors is sampled to determine which beams are broken by a finger or other object touching the face of the CRT. As all sixty-four sources are sequentially energized there will correspondingly be sequential outputs from three infrared detectors. Each infrared source is energized for one-half millisecond within a one millisecond period so each infrared source is energized once every sixty-four milliseconds.
The sequential and periodic scanning of the infrared sources is controlled by oscillator/clock driven digital circuitry and the clock time when a detector determines its corresponding beam has been broken indicates a horizontal or vertical coordinate of the point on the CRT face being touched by a finger. These last mentioned clock times are then processed by a microprocessor and a specific point or a row of information on the CRT face is highlighted to indicate the finger marked point, information, or command to be executed.
The clock count of an interrupted vertical infrared beam indicates to the microprocessor whether the point is on the left half or the right half of the CRT screen. The microprocessor knows from the interrupted infrared beam clock counts which horizontal beam originates from the left hand edge of the screen and which beam originates from the right hand edge of the screen. The microprocessor then selects the horizontal beam originating from the side of the screen corresponding to the interrupted vertical beam. The selected horizontal beam is the one close to the CRT face so vertical parallax is minimized. The horizontal beam spaced furthest from the CRT face is rejected as it would cause unacceptable parallax.
The clock count of the selected horizontal beam and the clock count of the broken vertical beam respectively indicate the vertical and horizontal coordinates of the point being touched by a finger. The microprocessor, which also generates the signals for the information being displayed, then causes the touched point or row of characters, etc. to be highlighted. The microprocessor will also perform other functions if the touched point indicates a command to the microprocessor.
In FIGS. 3 and 4 are shown the detailed block diagram of our invention. In FIG. 3 an oscillator/clock (not shown), well known in the art, is used in conjunction with flip-flop 10 and logic gates 11 and 12 to generate timing signals used to drive the digital circuitry of our invention. The clock signal applied to flip-flop 10, and logic gates 11 and 12 is shown as signal CLK in FIG. 5. Clocking signal CLK has a period of 0.5 milliseconds. Initially, flip-flop 10 is in its zero state with its zero output being high, and this output is connected to the D input of the flip-flop as well as to AND gate 12. The next clock pulse which is applied to toggle input T of flip-flop 10 causes the flip-flop to go to its one state due to the D input being high. The one output of flip-flop 10 is now high, while the zero output, which is coupled around to the D input, is now low. Upon the next clock pulse being applied to toggle input T, flip-flop 10 will be returned to its zero state because its D input is low at this time. The result of the operation of flip-flop 10 is shown in FIG. 5 with the one output signal waveform being shown as F/F1 and the zero output signal waveform being shown as F/FO. It can be seen that the output signals of the one and zero outputs of flip-flop 10 are mirror images of each other and have a period of 1 millisecond. As may be seen in FIG. 3, the one output of flip-flop 10 is one of the two inputs to AND gate 11, while the zero output of the flip-flop is one of the two inputs of AND gate 12. The second input to each of gates 11 and 12 is the clock input. The output of AND gate 11 is the signal .phi.shown in FIG. 5 while the output of AND gate 12 is the signal .phi.2 shown in FIG. 5. The period of both signals .phi.1 and .phi.2 is 1 millisecond and these two signals are 0.5 milliseconds out of phase with each other. Signals .phi.1 and .phi.2 are used to drive circuits of our invention.
As may be seen in FIG. 3, signal .phi.1 is input to six bit counter 13 which counts in binary fashion and provides a six bit binary number on its output leads. The three lower order bits of the six bit binary number output from counter 13 are input to both one-out-of-eight (1/8) decoder 14 and one-out-of-eight (1/8) decoder 15 as shown. Decoders 14 and 15 respond to the three bit binary number input to them to sequentially provide a signal on one out of the eight leads output from each of these circuits. With respect to decoder 14 the eight output leads are used to sequentially select one of the total of eight of one-out-of-eight (1/8) decoders 17 within decoder 16. The three lower order bits output from six bit decoder 13 are applied to each of the decoders 17 within decoder 16. The result is that each of decoders 17 is sequentially selected and, upon each of decoders 17 being selected, their eight output leads are individually and sequentially energized. The end result is that the sixty-four total output leads from decoder 16 are individually and sequentially energized for 0.5 millisecond periods beginning with each .phi.1 pulse and in approximate synchronism with the F/FO signal.
As mentioned heretofore, the sixty-four infrared light emitting diodes are distributed around the left, bottom and right edges of the CRT face with twenty LEDs being located on the left side of the screen, twenty-four LEDs being located along the bottom edge of the screen and twenty LEDs being located along the right side of the screen. All of the LEDs are uniformly spaced along their respective sides of the face of the CRT. Each of the sixty-four LEDs located around the edge of the CRT face is connected to a corresponding one of the sixty-four ouput leads from decoder 16 in FIG. 3. In this manner, decoder 16 is able to periodically and sequentially energize each of the infrared LEDs around the three edges of the CRT. Particularly, output leads 1-24 from decoder 16 sequentially energize each of the twenty-four LEDs located on the bottom edge of the CRT, while leads 25-44 sequentially energize the LEDs along the left hand edge of the screen and output leads 45-64 from decoder 16 sequentially energize the twenty LEDs along the right hand edge of the CRT screen. As mentioned previously, there is an LED energized during each one state of the signal represented in FIG. 5 as F/FO. This is during the second half of each one millisecond period, the first half of which is during each one state of F/F1.
In FIG. 3, decoder 15 has the three higher order bits output from counter 13 input thereto and alike decoder 14, decoder 15 sequentially and periodically energizes each of its eight output leads which are connected to analog switch 18 shown in FIG. 4. The three lower order bits output from counter 13 are also connected to analog switch 18. Particularly, the last-mentioned total of eleven leads input to selector switch 19 within analog switch 18. Selector switch 19 responds to these signals to sequentially select one-out-of-sixty-four inputs thereto and connect the selected input to its output which is wired to switch 20 as shown. As noted in FIG. 4, the sixty-four inputs to selector switch 19 are connected to individual ones of the photo detectors located around the edge of the CRT face. The control signals input to switch 19 cause the switch to periodically and sequentially step at a 1 millisecond rate to connect ones of the photo detectors through to switch 20 for a 1 millisecond period. Switch 19 operates such that as an infrared LED is energized its corresponding photo detector is being connected through to switch 20.
During the 1 millisecond period in which each photo detector is connected to the input of switch 20 the switch is operated to connect the input through to its outputs .phi.A and .phi.B for 0.5 millisecond periods each. This is done under the control of the F/F1 signal applied to control input E from the one output of flip-flop 10 in FIG. 3. In this manner, the detector signal input to switch 20 is switched between its two outputs for 0.5 milliseconds apiece. During the first 0.5 milliseconds of each 1 millisecond period switch 20 switches the input signal to its output .phi.A to sample and hold circuit 21. Circuit 21 is made up of amplifier 22 and capacitor 33 in a manner well known in the art and stores samples of the signals input thereto and provides an output corresponding to the samples. During this first 0.5 milliseconds the LED corresponding to the photo detector connected to switch 20 is not operated and the only signal received by the photo detector, and input to sample and hold circuit 21 is due to ambient light. The output of sample and hold circuit 21 is input to reference circuit 24 as shown. In particular, the output of circuit 21 is applied to comparators 25 and 28. Comparator 25 has two inputs, the second input of which is connected to a voltage divider circuit comprising resistors 26 and 27 which divide voltage V as shown. The purpose of comparator 25 is to monitor the output from sample and hold circuit 21 to determine when the ambient light condition exceeds a predetermined level set by the voltage divider. When the ambient level is too high, there is an output from comparator 25 to the set input S of flip-flop 30 in interface circuit 29 which maintains this flip-flop in its one state for the duration of the time that the ambient level is too high.
During the second 0.5 milliseconds of each one millisecond period the control input E of switch 20 is high and a photo detector is connected via lead .phi.B and amplifier 23 to comparator 28 which compares the photo detector data signal on lead .phi.B with the output of the sample and hold circuit 21. Upon a finger or other object being placed against the screen of the CRT to interrupt an infrared beam, the output of the corresponding photo detector goes high, except for the ambient light level, and this high signal, which is present on lead .phi.B, is inverted at comparator 28 and applied to input D of flip-flop 30 in interface circuit 29. While input D is low and the .phi.2 clock signal appears at clocking input CL of flip-flop 30, the flip-flop is placed in its zero state indicating an interrupted light beam. The one output of flip-flop 30 is applied via a driver amplifier 31 to microprocessor 32 which interprets the low signal as an interrupted beam and then supplies an acknowledgement signal via lead ACK to the reset input R of flip-flop 30 to return the flip-flop to its one state. In order for microprocessor 32 to know which infrared light beam is interrupted as indicated by the low signal output from flip-flop 30, the six bit binary number output from counter 13 in FIG. 3 is applied via driver amplifier 31 to microprocessor 32. From the address information and beam interrupt information input to microprocessor 32, microprocessor 32 identifies three infrared light beams which are interrupted by a finger or other object during each sixty-four microsecond period in which all the light emitting diodes are scanned.
From the interrupt information input to microprocessor 32, the microprocessor first determines which of the twenty-four vertical infrared beams is interrupted and uses this information to determine which interrupt address for the two interrupted horizontal infrared beams should be utilized. If the infrared beam for vertical oriented LEDs 1-12 is interrupted, the microprocessor knows that the object interrupting the beam is touching the left half of the CRT face. Similarly, if the infrared beam of LEDs 13-24 is interrupted, microprocessor 32 knows that the object interrupting the beam is touching the right half of the CRT face. As previously described, the two horizontal interrupted infrared beams are generated by an LED source at each of the left and right hand edges of the CRT face. To minimize parallax errors, microprocessor 32 will only utilize or consider the infrared beam originating from the left edge of the CRT face when the interrupted vertical beam originates from LEDs 1-12; and microprocessor 32 will only consider the infrared beam originating from the right hand edge of the CRT face when the interrupted vertical beam originates from one of LEDs 13-24.
Once microprocessor 32 determines which interrupted horizontal beam to consider, it utilizes the clock information input thereto from counter 13 in FIG. 3, for the interrupted vertical beam and the selected interrupted horizontal beam to calculate the address of the point on the CRT face which is being touched by a finger or other object. Microprocessor 32 then uses this point address to perform various functions. The information displayed at the point touched may indicate a command to be executed and microprocessor 32 then causes the command to be executed. The procedure may be a bit more complicated whereby the first point touched on a screen may indicate a given type of processing to be performed on information displayed at a second point to be touched on the CRT face. Many variations may be implemented limited only by the programming of microprocessor 32. Another function that may be accomplished is to perform a display inversion upon the point touched. In this case, for example, light alpha-numeric characters may normally appear on a dark background and, upon touching the point, the point or a predetermined area of the screen is inverted such that black letters are displayed on a white background to indicate to the operator by visual feedback which point is being processed by the microprocessor.
The following program listing is the program put into microprocessor 32 to implement the invention and is written in assembly language, which is well known in the art. The program is input via an 8080 assembler to an 8080 microprocessor coupled with sufficient memory. Descriptive headings are provided throughout the program listing to identify sub-routines that implement the various functions of the program. These functions are described hereinabove in this specification.
Claims
We claim:
1. Interactive video display apparatus functioning with a video display having a non-planar display area and with associated equipment which generates signals for a display on said display area comprising: a plurality of energy sources located along the edge of the display area of said video display and energized to send beams of energy proximate to at least a portion of said display area; a plurality of detectors located along the edge of the display area but being spaced further therefrom than said plurality of energy sources, each of said detectors receiving at least one energy beam and providing an indication upon the received energy beams being interrupted and wherein an object touching the video display interrupts more than two energy beams at least one of which is close to the surface of said display at the point touched; means responsive to the interrupted beam indication from ones of said detectors for providing identity signals indicating which energy beams are interrupted; and means for processing said identity signals to choose the interrupted energy beams closest to the surface of said display area at the point touched, the identity signals of the chosen interrupted beams defining the coordinates of the video display point being touched.
2. The interactive video display apparatus of claim 1 wherein said identity signal providing means comprises: means for periodically sampling the output of each of said detector means to determine the ambient light conditions around said video display detected by said detector means; and means for determining if the ambient light conditions are so bright as to interfere with the operation of said interactive video display apparatus, and when said ambient light conditions are too bright providing a signal to said processing means which causes no further processing of said identity signals.
3. The invention in accordance with claim 2 further comprising: a counter driven by a clock source; a decoder responsive to said counter and having an output associated with each of said energy sources, said decoder outputs being sequentially and periodically energized to energize said energy sources; and a first selector having an output associated with each of said detectors sequentially and periodically connecting each of said detectors to an output of said first selector, each of said detectors being connected to said first selector output for a first time period during part of which their associated energy sources are energized.
4. The invention in accordance with claim 3 wherein said first selector connects a selected detector to said sampling means for part of said first time period and to said identity signal providing means for the remainder of said first time period during which its associated energy source is energized.
5. The invention in accordance with claim 4 wherein plurality of energy sources each comprise a device for emitting infrared when energized.
6. Interactive video display apparatus functioning with a video display device having a non-planar display area and with associated equipment which generates signals for a display on said display area, comprising: a first plurality of energy sources located along the edge of the display area of said video display and energized to send beams of energy relatively close to at least a portion of the surface of said non-planar display area; a second plurality of energy sources also located along the edge of the non-planar display area of said video display and energized to send beams of energy close to at least a portion of but not touching the surface of said display area, the beams from said second plurality of energy means not being coplanar with said beams of energy from said first plurality of energy sources; a third plurality of energy sources also located along the edge of the display area of said video display and energized to send beams of energy close to at least a portion of but not touching the surface of said display area, the beams from said third plurality of energy sources not being coplanar with said beams of energy from said first and said second energy sources, with an energy beam of one each of said first, second and third plurality of energy sources being interrupted upon touching said display area with a finger or other object; a plurality of detectors with one detector being associated with each energy source of said first, second, and third plurality of energy sources, each detector being located on the opposite side of said display area from its associated one of said first, second or third plurality of energy sources and receiving the energy beam from the associated energy source, said detectors providing an output indication upon the received energy beam being interrupted; and means responsive to said interrupted beam output indication from ones of said detectors upon said display area being touched for providing identity signals indicating which energy beams are interrupted.
7. The invention in accordance with claim 6 further comprising means for processing said identity signals to choose the interrupted energy beams closest to the surface of said display area at the point touched, the chosen interrupted beam identity signals defining the coordinates of the point being touched.
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