ELECTRO-OPTICAL POSITION DETERMINING SYSTEM

Abstract: A position determining system for providing electrical signals representative of the positions of a light source movable within a defined area. The system may be im­ plemented for purposes of data entry or for purposes of object location or surveying. When embodied in a data entry tablet, the invention provides signals representative of the positions of a stylus movable within the area of the tablet and comprising first and second photodetectors spaced along a base line by a predetermined distance, and means associated with each photodetector and operative to provide a movable narrow field of view for each photodetector. Means are provided for monitoring the angular position of each of the fields of view with respect to the base line and for providing a signal indication of the respective angular positions. A stylus having a light emitter at the tip thereof is movable within the area of the tablet and provides light detectable by each of the photodetectors. Each of the photodetectors provides a respective signal when the field of view of the corresponding photodetector receives light from the emitter. Means are provided which are operative in response to the signal indication of the angular position of each of the movable means at which light from the emitter is respectively detected to provide a signal representing the position of the emitter within the area of the tablet.

Description: FIELD OF THE INVENTION This invention relates to an apparatus for determining the position of at least one radiation source according to the first part of claim 1. Furthermore, this invention relates to an apparatus for providing signals representative of one or more positions of at least one light source according to the first part of claim 10, as well as to a data entry system according to the first part of claim 23, an apparatus for determining the position of a radiation source, according to the first parts of claims 31 and 32, respectively. This invention further relates to a method for determining a position of a radiation source according to the first part of claim 33. BACKGROUND OF THE INVENTION Systems are known for determining the position or location of an object within a defined area. Such systems find utility for the entry of graphic and other information into a computer, and are often embodied into a data entry tablet which includes means for sensing the position of a stylus or other point movable within a defined area, and for providing an electrical signal which is representative of successive stylus positions, thereby to denote lines, curves and figures drawn by the stylus on the tablet. Another known use for position determining systems is for land surveying and wherein means are provided for sensing the position of a target movable within a defined area, and for providing a signal representative of the sensed target positions and from which survey information can be derived. A related data entry device is known as a cursor controller or "mouse", which is usually in the form of a small housing movable over a surface and which provides corresponding movement of a cursor on a display screen. Movement of the cursor can be employed for data entry of graphical information and can also be used as a pointer for identifying a position on the screen or information displayed on the screen, such as for interactive computer usage. In general, mouse movement is provided by a ball that rolls over a surface, the ball movement being sensed by mechanical or optical means. Motion can also be sensed via a specially prepared sensible surface over which the mouse is moved. For example, a checkerboard pattern has been employed on a surface, and light reflected from the surface is detected by a photodetector which provides pulse signals indicative of motion with respect to the surface pattern. A review of several different types of mouse cursor controllers is provided in an article entitled "Interfacing Mice to Computers", Machine Design , January 12, 1984, pp. 84-91. Graphic input devices are known using pairs of scanned light beams, as shown, for example, in U.S. Patents 3,553,680; 3,613,066; 3,364,389; and 4,294,543. In this type of entry device, first and second narrow light beams are scanned across a surface and means are provided for sensing the light beams at intersecting points. within the surface, the angular position of the two beams at the detected intersections representing the position within the defined area. Another known technique employs orthogonal light beams provided across a display surface, the interruption of selected orthogonal pairs of beams providing an identification of the data entry point. Examples of surveying and related systems for automatic position determination are shown in U.S. Patents 3,714,657; 3,400,398; 3,437,825; and 3,443,095. Range measuring systems are shown for example in U.S. Patents 2,830,487; 3,759,614; and 3,961,851. From US-A-4,470,122 an integrated electro-optical position sensing apparatus is known which utilizes driven sensors to scan the area of interest. The sensors are scanned in reciprocating, arcuate scanning paths orientated to scan across the position of a radation-emitting module. The driven sensors are connected to a common vertically journalled shaft and driven by drive-motors which are also connected to this shaft. The sensors are positioned within the interior of a housing that includes stationary sensor windows that are elongated in the lengthwise dimension and position, so as to be in general registration with the arcuate scanning movements of the sensors. Each sensor consists of a transducer rigidly secured to a light channelling shroud having a slot. The transducer-light channelling shroud combination is driven by the drive motors. The sensors themselves are driven to scan a predefined area. From US-A-4,209,254, a system is known, wherein a set of radiation-emitting sources are disposed on a movable object and sequentially activated to determine the line of light of the movable object. It is an object of the invention to improve the accuracy of the state of the art apparatus and method. This object will be solved with the apparatus comprising the features of the first part of claim 1 by the features of claim 1's second part, with the appparatus comprising the features of the first part of claim 10 by the features of claim 10's second part, with the data entry system comprising the features of the first part of claim 23 by the features of its second part. Furthermore, this object will be solved with the apparatus comprising the features of the first parts of claim 31 and 32, by the features of their respective second parts. This object will also be solved with the method according to the first part of claim 33 by the features of its second part. SUMMARY OF THE INVENTION The system may be implemented for purposes of data entry or for purposes of object location or surveying. When embodied in a data entry tablet, the invention provides signals representative of the positions of a stylus movable within the area of the tablet and comprising first and second photodetectors spaced along a base line by a predetermined distance, and means associated with each photodetector and operative to provide a movable narrow field of view for each photodetector. Means are provided for monitoring the angular position of each of the fields of view with respect to the base line and for providing a signal indication of the respective angular positions. A stylus having a light emitter at the tip thereof is movable within the area of the tablet and provides light detectable by each of the photodetectors. Each of the photodetectors provides a respective signal when the field of view of the corresponding photodetector receives light from the emitter. Means are provided which is operative in response to the signal indication of the angular position of each of the movable means at which light from the emitter is respectively detected to provide a signal representing the position of the emitter within the area of the tablet. In one presently preferred embodiment, a rotating cylinder is provided for each photodetector, the cylinder having a slit providing a narrow field of view or line of sight which is rotatable at a constant and known angular velocity. The time of rotation of each of the cylinders is monitored with respect to a start or reference position such that the time elapsed between the start position and the time at which light from the emitter is detected by each of the photodetectors is known. The elapsed time is a measure of the angular position of the rotating cylinder with respect to the detected position of the emitter and from this angular information, the position of the emitter with respect to the detectors is readily determined by known geometrical relations. Alternatively, the angular position of each of the rotating cylinders can be determined by use of respective shaft angle encoders which provide signal indications of the rotational position of the respective cylinders and therefore the respective fields of view. In this latter instance, angular position is measured directly, and the rotational velocity of the fields of view need not be constant or known. The rotatable field of view can be provided by other means such as an opaque shield rotatably movable around each detector and operative to occlude light from the light source when in the line of sight between the source and the detector. A timing cycle can be commenced by the sensed change in received light upon passage of the leading or trailing edge of the shield. The moving field of view can also be provided by a linearly movable silt or other view limiting shield. In another embodiment, a single photodetector is employed and is rotatable about an axis and operative to detect light from a source movable within a defined area at each of two predetermined positions in the path of rotation. The position of the light source in relation to the detector positions is then determined. In an alternative embodiment, a pair of light emitters is provided along a straight edge which is movable within the tablet area and the position of each of the emitters is determined in the manner described above to provide an indication of the position of the straight edge within the tablet area. Additional commands can be provided in conjunction with the position data of the emitter or emitters to provide data corresponding with the position of the stylus or straight edge at intended portions of the tablet area. DESCRIPTION OF THE DRAWINGS The invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings in which: Fig. 1 is a pictorial representation of a preferred embodiment of the invention; Fig. 2 is a diagrammatic representation of a prefered embodiment of the invention; Fig. 3 is a diagrammatic representation of one means for sensing cylinder rotation; Fig. 4 is a diagrammatic representation of another means for sensing cylinder rotation; Fig. 5 is a block diagram of the processing logic; Fig. 6 is a diagrammatic representation of an alternative embodiment; Fig. 7 Is a diagrammatic representation of an alternative embodiment of the invention; Fig. 8 is a pictorial representation of a detector and view limiting shield means employed in the embodiment of Fig. 7; Fig. 9 is a diagrammatic representation of a further embodiment employing a view limiting shield which is linearly movable; Fig. 10 is a diagrammatic representation of a rotatable mirror employed for directing received light to an associated detector; Fig. 11 is a diagrammatic representation of an alternative rotating mirror arrangement for directing received light to an associated photodetector; Fig. 12 is a diagrammatic representation of an embodiment of the invention employing fiber optic cables for directing light from two sensed positions to a single photodetector; Fig. 13 and Fig. 14 are elevation and top views, respectively, of another embodiment utilizing a rotatable single detector and useful especially for land surveying purposes. Fig. 15 is a diagrammatic representation of an embodiment of the invention employing three light receiving locations. DETAILED DESCRIPTION OF THE INVENTION Referring to Figs. 1 and 2, there is shown a data tablet having a defined area 10 within which a stylus 11 is movable. The stylus has a light emitter 13 such as a light emitter diode (LED) on the tip thereof. It should be understood, however, that the light provided by emitter 13 is not limited to light having a frequency in the visible range, and, in fact may preferably have a frequency in the infrared frequency range. First and second photodetectors 12 and 14 are provided along an edge of the tablet, the detectors being spaced apart by a predetermined distance L which defines a known base line. A pair of opaque cylinders 16 and 18 are provided around respective photodetectors 12 and 14, each of the cylinders having a respective slit 20 and 22, axially provided thereon to provide a narrow field of view or line of sight for light receivable by the respective photodetectors from the emitter 13. Each of the cylinders is rotatable by suitable motive means such as respective electric motors. The angular position of each of the rotating cylinders is determined, in one embodiment, by measurement of the elapsed time of rotation of each of the cylinders with respect to a start or zero reference position. As illustrated in Fig. 3, a start position for each of the cylinders is defined by a fiducial mark 28 on the cylinder and which is sensed by sensor 29 to produce a signal which causes a clock counter in processing logic 30 (Fig. 5) to be started to provide a count representative of the angular position of the associated rotating cylinder with respect to the start position. The processing logic 30 also receives the outputs from photodetectors 12 and 14. The time elapsed between the start position and the time at which light from the emitter is detected by each of the photodetectors is determined by logic 30 by use of known geometrical relationships. The elapsed time is a measure of the angular position of the rotating cylinders with respect to the detected position of the emitter and, from this angular information, the position of the emitter with respect to the detectors is readily determined. The logic 30 provides an output signal representative of the position of the emitter within the tablet area, and this signal can be provided to a display or other utilization apparatus. An alternative embodiment is illustrated in Fig. 4 in which the angular position of each of the rotating cylinders is directly provided. Referring to Fig. 4, a shaft angle encoder is coupled to the cylinder 16, the encoder being operative to provide a signal representative of the rotational position of the associated cylinder. The encoder comprises an encoder disc 34 attached to and rotatable with the cylinder, and a light sensor 36 operative to receive light from source 38 which is directed through the disc 34. The sensor 36 provides signals which represent the rotation of the disc and cylinder 16. The encoder signals are employed by logic 30 in association with the photodetector signals to calculate the position of the emitter in relation to the detectors. A further embodiment is illustrated in Fig. 6 in which a pair of light emitters 40 and 42 is provided in spaced relation along a straight edge which is movable within the tablet area. In the illustrated embodiment, the light emitters 40 and 42 are provided on a template 44 which is movable within the tablet area. The position of each of the emitters is determined in the manner described above to provide an indication of the straight edge defined by the spaced emitters within the area of the tablet. The template can include a standard frame into which various template sheets are insertable, each providing symbols and forms as desired. It may be desirable to distinguish between the respective emitters 40 and 42. This can be accomplished in several different ways, including the employment of different frequencies of light emission by the respective emitters, or by pulsing the emitters at different rates. If such coding of the light emissions is employed, the circuitry associated with the light sensors will include means for distinguishing between the respective light emissions. In addition to the entry of the position of a stylus point or an edge and the display of such point or edge positions, additional information can be entered for display in association with the positional data or for other associated use. For example, characters such as numbers, letters and symbols 46 can be provided on the template 44 of Fig. 6 and such items can be displayed in association with the position and orientation of the defined edge by entry of such items. Such date entry can be, for example, by means of an optical pen 48 for selecting characters. Once the orientation of the defined edge or orientation of the template is known, in the manner described above, the position of each symbol, number or letter within the template is also known and can be readily entered into a data system for display such as by optical pen or other known means. In the above embodiments, each detector has a rotating slit associated therewith for defining the respective narrow field of view. A further embodiment is shown in Fig. 7, which depicts a pair of detectors 49 each having a transparent cylinder 50 disposed therearound with an opaque segment 52 on the cylinder. Each of the detectors can be similarly embodied as illustrated in Fig. 8. The detectors receive light from the light source 13 at all times except when temporarily occluded by the interposition of the opaque shield in the light path. The line of sight between the light source and detector can be specified at the leading edge or trailing edge of the moving shield. The arcuate length of the shield can be of any extent less than 360°. During the interval at which the shield occludes the light, the clock counters can be reset for the next timing cycle. In operation, a start signal can be provided as the leading edge of the shield enters the light path, causing a change in the sensed light, and a timing interval commenced for that rotational cycle of the cylinder. Alternatively, the passage of the trailing edge of the shield out of the light path can signify the commencement of a timing cycle. The moving field of view can be otherwise coordinated with the detector and need not be by a rotating field of view, as described above. In the embodiment of Fig. 9, an opaque shield 54 is provided having a slit 56 therein. The shield being linearly movable in reciprocating fashion past the associated detector. Each detector includes a similar reciprocating shield. The line of sight between each detector and the light source is determined by the alignment of the respective slits with the respective light paths. In the embodiment of Fig. 10, a rotating mirror 58 is employed to direct light from the light source 13 to the photodetector 49. Upon alignment of the reflecting surface 60 of the rotating mirror with the incident light, light is directed to the detector to specify the line of sight for the position determining computation. Another mirror implementation is shown in Fig. 11, in which the mirror 62 is rotatable about the axis, and upon alignment of the reflecting surface 64 with the incident light, light is reflected to the detector 49, which in this implementation is top mounted such as on a support arm 66. A further embodiment is illustrated in Fig. 12 in which a single photodetector 49a is employed. A pair of fiber optic cables 68 are provided, each coupling light from a respective sensing position to the single detector. The outer end 70 of each fiber optic cable 68 is disposed to receive light from the light source 13 as selectively provided by the moving field of view, such as a rotating cylinder 72 having a slit thereon, as in the embodiment of Fig. 3 described above. Other means can be provided for transmitting or reflecting light received from the respective light sensing positions to the single photodetector, such as a mirror or mirror assembly. The inner end 74 of each fiber optic cable is in light coupling relation to detector 49a. It will be appreciated that the embodiments discussed above may be designed for use in land surveying but are more suitable for use with data entry tablets. However, the embodiment of the invention shown in Figs. 13 and 14 is especially suited for land surveying. A single photodetector 49b is mounted on the end of a boom 80 having a counterweight 82 at the other end thereof, the boom being mounted for rotation on a tripod 84 or other suitable support, and rotated at a known velocity by means of a motor 86. A light source 13a is provided at the point remote from the detector, the light from this source being detectable by the single detector at each of two positions, as illustrated in Fig. 14. In the illustrated embodiment, the positions are shown at diametrically opposite positions of a rotary cycle. A narrow field of view for the detector is provided by any convenient means, such as a rotating slit as described above. Thus, a line of sight between the light source and each light sensing position of the detector is specified, and the position of the light source then determined. A smaller version of this single detector embodiment can also be employed for data tablet or other data entry purposes. In all the embodiments discussed heretofore, it is assumed that there is a clear "line of sight" between the light source and the two light receiving locations. This would usually be the case with data entry tablets of the type described, where the selected area is always located on one side of the "base line" which extends between the two selected light receiving locations. However, in applications where the "selected area" to be monitored completely surrounds the base line extending between the two light receiving locations, or where there may not always be a clear "line of sight" between the light source and both of the light receiving locations (such as in land surveying where the line of sight might be blocked by a tree or other non-movable objects), complete surveillance of the selected area may not be possible. Therefore, according to another embodiment such as diagrammatically illustrated in Fig. 15, a third light receiving location may be provided to assure complete surveillance of the area. In the illustration of Fig. 15, those elements which are the same as elements shown in the embodiment of Fig. 2, carry common reference numbers. As shown, a first base line L₁ is defined by light receiving diodes 12 and 14 which scan selected area 88 extending on both sides of base line L₁ as indicated by light pen 11A and 11B on the right side and light pen 11C on the left side. Normally almost all locations in the select area 88 would satisfactorily be scanned by light receiving diodes 12 and 14 such that the position of a light source could readily be determined. However in the event an object 89 which is opaque to light source 11B was located so as to block the line of sight between light pen 11B and light receiving diode 14 (which line of sight is represented by line segments 90 and 92). The light receiving diode 12 would not have an input to help determine the location of light pen 11B, and consequently the location of light pen 11B along the line of sight 94 could not be determined. However, according to the embodiment of the present invention shown in Fig. 15, there is also included a third light receiving diode 96 which is located at a known position and distance with respect to base line L₁. As is also clear from the illustration of Fig. 15, there are secondary base lines L₂ and L₃ established between the light receiving diodes 12 and 96, and 14 and 96 respectively. Consequently, the position of light pen 11B may readily be determined by processing the information from light receiving diode 12 and 96 with respect to base line L₂ in the same manner as the information from light receiving diode 12 and 14 was processed with respect to base line L₁. In a similar manner, if the line of sight between the light source and light receiving diode 12 is blocked, information from light receiving diode 14 and light receiving diode 96 may be used with respect to base line L₃ to determine the position of the light source. A third light receiving diode would also be necessary if the light source were to lie along an extension of a base line extending between two light receiving diodes even if there was no blockage of light paths. For example as shown in Fig. 15 light pen 11A lies along an extension of L₃ and consequently, it is impossible to determine the distance of the light source from either light receiving diode 14 or light receiving diode 96. However, in this example the location of light pen 11A may readily be determined by processing the information received from light receiving diode 12 and light receiving diode 96 with respect to base line L₂. Light pen source 11C is included to illustrate that the surveillance area or selected area completely surround the light receiving locations. Furthermore, although the light receiving diode 12, 14 and 96 are arranged in Fig. 15 so as to form an equilateral triangle to simplify the processing of data or calculations, the three locations of the light receiving diodes could form a right triangle or any other irregular triangle so long as the location and distance of rich light receiving diode is known with respect to every other light receiving diode. This invention is not to be limited by what has been particularly shown and described except as indicated in the appended claims.

Claims: Apparatus for determining the position of at least one radiation source (11/13; 11a, 11b, 11c; 13a; 40, 42) located and movable within a selected area (10) comprising: radiation detecting means (12, 14; 49) at first and second locations, respectively, for monitoring radiation emitted by said at least one movable radiation source (11/13; 11a, 11b, 11c; 13a; 40, 42), said first and second location spaced a first predetermined distance (L) apart along a base line; said radiation detecting means (12, 14; 49) suitable for detecting radiation emitted by said at least one movable radiation source (11/13; 11a, 11b, 11c; 13a; 40, 42) located within said selected area (10); means for determining a first angle between said base line (L) and a first line extending between said first location and said at least one movable radiation source (11/13; 11a, 11b, 11c; 13a; 40, 42) and for determining a second angle between said base line (L) and a second line extending from said second location and said at least one movable radiation source (11/13; 11a, 11b, 11c; 13a; 40, 42); and processing means (30) responsive to said determining means for providing signals representative of the position of said at least one movable radiation source (11/13; 11a, 11b, 11c; 13a; 40, 42) within said selected area (10); characterized in that said radiation detecting means (12, 14; 49) is nonscanning and operates independently of said at least one movable radiation source (11/13; 11a, 11b, 11c; 13a; 40, 42); said determining means includes means disposed in combination with said radiation detecting means (12, 14; 49) for providing a moving field of view (16/20, 18/22; 50/52; 54/56; 58/60; 62/64) at each said first and second locations, said moving field of view means including a moving reference point (28); and means (29, 36, 38) for determining the position of said moving reference point (28) of said moving field of view means (16/20, 18/22; 50/52; 54/56; 58/60; 62/64) with respect to a start position when said moving reference point (28) coincides with said first and second lines, respectively. The apparatus of claim 1, characterized in that said at least one movable radiation source (11/13; 11a, 11b, 11c; 13; 40, 42) includes first and second radiation sources (40, 42), said second radiation source (42) spaced apart from said first radiation source (40) a second predetermined distance, the pair of radiation sources (40, 42) indicative of a straight edge movable within said selected area (10); said radiation detecting means (12, 14; 49) are adapted to detect light means emitted by said first and second light sources (40, 42), respectively; said determining means is further operative for determining a third angle between said base line (L) and a third line extending between said first location and said second radiation source (42) and for determining a fourth angle between said base line (L) and a fourth line extending between said second location and said second radiation source (42), said third line occurring when radiation from said second radiation source (42) is detected by said radiation detecting means (12) at said first location and said fourth line is occurring when radiation from said second radiation source (42) is detected by said radiation detecting means (14) at said second location; and said means responsive to said determining means further provides signals representative of the position of said second radiation source (42) within said selected area (10) and the position of said straight edge indicated by said pair of radiation sources (40, 42) within said selected area (10). The apparatus of claim 1, characterized in that said moving field of view means (16/20, 18/22; 52/54; 58/60; 62/64) moves arcuately around said first and second locations. The apparatus of claims 1, 2 or 3 wherein said radiation detecting means (12, 14; 49) comprises a photodetector positioned at each said first and second locations. The apparatus of claims 1, characterized in that said radiation detecting means comprises a photodetector (12, 14; 49) positioned at each said first and second locations; and said moving field means comprises a pair of opaque members (16, 18; 54) located one each between said selected area (10) and said corresponding photodetector (12, 14; 49) at said first and second locations, each of said opaque members (16, 18; 54) having a slit (20, 22; 56) for transmitting a narrow beam of radiation from said movable radiation source (11/13) therethrough, said moving field means including means for repetitively moving each said opaque member (16, 18; 54) and said slit (20, 22; 56) thereof along a known path to provide said moving field of view of said selected area. The apparatus of claim 1, characterized in that said radiation detecting means comprises a photodetector (49) positioned at each said first and second locations; and said moving field means comprises a pair of transparent members (50) located one each between said selected area (10) and said corresponding photodetector (49) at said first and second locations, each of said transparent members (50) having an opaque segment (52) for blocking radiation from said movable radiation source (11/13), said moving field means including means for repetitively moving each said transparent member (50) and said opaque segment (52) thereof along a known path to provide said moving field of view of said selected area. The apparatus of claim 1, characterized in that said radiation detecting means comprises a photodetector (49) positioned at each said first and second locations; and said moving field means comprises a pair of mirrors (58; 62) located one each between said selected area (10) and said corresponding photodetector (49) at said first and second locations, each of said mirrors (58; 62) having a reflecting surface (60; 64) for reflecting radiation from said movable radiation source (11/13) onto said photodetector (49), said moving field means including means for repetitively moving each said mirror (58; 62) and said opaque segment (60; 64) thereof along a known path to provide said moving field of view of said selected area. The apparatus of claim 5, characterized in that said known path is a straight line adjacent to first and second locations. The apparatus of claims 5, 6, or 7, characterized in that said known path is a circular path around said first and second locations. Apparatus for providing signals representative of one or more positions of at least one light source (11/13; 11a, 11b, 11c; 40, 42) movable within a selected area (10) comprising: first and second photodetecting means (12, 14; 49) disposed at first and second locations, respectively, for detecting radiation emitted by said at least one movable light source (11/13; 11a, 11b, 11c; 40, 42), said first and second locations spaced a first predetermined distance (L; L1) apart along a base line; means for determining a first angle between said base line (L) and a first line extending between said first photodetecting means (12; 49) and said at least one movable radiation source (11/13; 11a, 11b, 11c; 40, 42) and for determining a second angle between said base line (L) and a second line extending between said second photodetecting means (14; 49) and said at least one movable radiation source (11/13; 11a, 11b, 11c; 40, 42); and processing means (30) responsive to said determining means for providing signals representative of the position of said at least one movable radiation source (11/13; 11a, 11b, 11c; 40, 42) within said selected area (10); characterized in that said first and second photodetecting means (12, 14; 49); are nonscanning and operate independently of said at least one movable radiation source (11/13; 11a, 11b, 11c; 40, 42); means (16/20, 18/22; 50/52; 58/60; 62/64) are associated with each said photodetecting means (12, 14; 49) for providing a moving field of view therefor, said moving field of view moving arcuately around each said photodetecting means (12, 14; 49) independently of movement of said at least one radiation source (11/13; 11a, 11b, 11c; 40, 42); said moving field of view means (16/20, 18/22; 50/52; 58/60; 62/64) includes means for monitoring angular positions (28, 29, 34, 36, 38) of each of the arcuately moving fields of view with respect to the base line and providing signal indications thereof; a first signal is generated by said first photodetecting means (12; 49) upon receipt of radiation from said at least one movable radiation source (11/13; 11a, 11b, 11c; 40, 42) through the field of view (16/20; 50/52; 58/60; 62/64) of the first photodetecting means (12, 14; 49); a second signal is generated by said second photodetecting means (14; 49) upon receipt of radiation from said at least one light source (11/13; 11a, 11b, 11c; 40, 42) through the field of view (18/22; 50/52; 58/60; 62/64) of the second photodetecting means (14, 49); and said processing means (30) is operative in response to said first and second signals to provide said signal representing the position of the at least one light source (11/13; 11a, 11b, 11c; 40, 42) within the selected area (10). The apparatus of claim 10 characterized in that said at least one movable radiation source (11/13; 11a, 11b, 11c; 40, 42) includes first and second radiation sources (40, 42), said second radiation source (42) spaced apart from said first radiation source (40) by a second predetermined distance and emitting radiation detectable by each of said photodetecting means (12, 14; 49), the first and second radiation sources (40, 42) defining a straight edge movable within the selected area (10); said first and second photodetecting means (12, 14) are further operative to provide signals representative of radiation received from said second radiation source (42) through said first and second fields of view, (16/20, 18/22; 50/52; 58/60; 62/64); said signal providing means (30) is further operative in response to said signal indication of said angular position monitoring means (28, 29, 34, 36, 38) to provide signals representing the position of said second light source (42) and the position of said straight edge indicated by said pair of radiation sources (40, 42) within said selected area (10; 88). The apparatus of claims 3 or 10 characterized in that said arcuately moving fields of view (16/20, 18/22; 50/52; 58/60; 62/64) are rotating fields of view. The apparatus of claim 12, characterized in that said means for providing a rotating field of view (16/20, 18/22; 50/52; 58/60; 62/64) is operative to provide said rotating field of view at a predetermined angular velocity. The apparatus of claim 13, characterized in that the predetermined angular velocity is constant. The apparatus of claims 1 or 10, characterized in that said at least one light source (11/13; 11a, 11b, 11c; 40, 42) is a light emitting diode. The apparatus of claim 10, characterized in that said means for providing said arcuately moving field of view (16/20, 18/22; 50/52; 58/60; 62/64) associated with each said first and second locations includes a movable reference point (28). The apparatus of claims 3 or 17, characterized in that said means for providing said arcuately moving fields of view (16/20, 18/22; 50/52; 58/60; 62/64) associated with each of said first and second locations includes at least a portion of an opaque cylinder (16, 18) having an axial slit (28) therein at least partially surrounding each said first and second locations, and wherein each said axial slit (28) represents said movable reference point. The apparatus of claims 4 or 17, characterized in that each said arcuately moving fields of view is provided by transparent shield means (50) having an opaque segment (52) with distinct boundaries at least partially surrounding said first and second locations, respectively, said shield means (50) movable with respect to said first and second locations to interrupt radiation travelling towards said first and second locations, and wherein each said distinct boundary on each said transparent shield means (50) is said movable reference point. The apparatus of claim 11, characterized in that radiation emitted by each of said first and second radiation sources (40, 42), respectively, is coded, and wherein the photodetecting means (12, 14; 49) is operative to distinguish between coded radiation from said first and second radiation sources (40, 42). The apparatus of claims 2 or 11, characterized by a template (44) including said straight edge formed by said first and second radiation sources (40, 42), said template (44) including a plurality of information characters and symbols (46) thereon; means (48) for selecting one of said plurality of information characters and symbols (48); and means for providing a signal representative of said selected one of said plurality of information characters and symbols (48). The apparatus of claims 1 or 10, characterized in that said selected area (10, 88) is a data entry tablet and said at least one movable radiation source (11/13) is a stylus (11) having a radiation emitter (13) on the tip thereof, said stylus (11) being movable on the surface of the data entry tablet (10, 88). The apparatus of claim 10 characterized by: third photodetecting means (96) for monitoring radiation emitted by said at least one radiation source (11a, 11b, 11c) disposed at a third location said third location spaced a second predetermined distance (L2) along a secondary base line from said second location and spaced a third predetermined distance (L3) along a secondary base line from said first location; means (16/20, 18/22; 50/52; 58/60; 62/64) associated with said third photodetecting means (96) for providing a moving field of view therefor, said moving field of view moving arcuately around said third photodetecting means (96) independently of movement of said at least one radiation source (11a, 11b, 11c), said moving field means (16/20, 18/22; 50/52; 58/60; 62/64) including means for monitoring angular positions (28, 29, 34, 36, 38) of the arcuately moving field of view and providing signal indications thereof; said third photodetecting means (96) operative to generate a third signal upon receipt of radiation from said at least one light source (11a, 11b, 11c) through the field of view associated with said third photodetecting means (96), and said means for providing a position signal (30) further includes means operative in response to a signal indication of said angular positioning monitoring means associated with said third photodetecting means (96) to provide a signal representing the position of the at least one radiation source (11a, 11b, 11c) within said selected area (88). A data entry system for providing signals representative of one or more positions of a stylus (11) movable within a defined area (10, 88), comprising: a light emitter (13) associated with said movable stylus (11) providing emitted radiation; first and second photodetecting means (12, 14; 49) at first and second locations, respectively, for detecting radiation emitted by said light emitter (13), said first and second locations spaced a first predetermined distance (L) apart along a base line; means for determining a first angle between said base line (L) and a first line extending between said first location and said light emitter (13) and for determining a second angle between said base line (L) and a second line extending from said second location and said light emitter (13); and means (30) responsive to said determining means for providing signals representative of the position of said light emitter (13) within said selected area (10); characterized in that said first and second radiation detecting means (12, 14; 49) are nonscanning and operate independently of said light emitter (13); means (16/20, 18/22; 50/52; 58/60; 62/64) are associated with each said photodetecting means (12, 14; 49) for providing a rotating narrow field of view therefor, said narrow field of view means rotating independently of movement of said stylus (11); means for monitoring an angular position (28, 29, 34, 36, 38) of each of said narrow field of view means (16/20, 18/22; 50/52; 58/60; 62/64) with respect to the base line and providing signal indications thereof; a first signal is generated by said first photodetecting means (12; 49) when said first photodetecting means (12; 49), said narrow field of view means (16/20, 18/22; 50/52; 58/60; 62/64) associated therewith and radiation from said light emitter (13) are collinear; a second signal is generated by said second photodetecting means (14; 49) when said second photodetecting means (14; 49), said narrow field of view means (16/20, 18/22; 50/52; 58/60; 62/64) associated therewith and radiation from said light emitter (13) are collinear; and said means (30) is operative in response to the signal indications of said angular position monitoring means (28, 29, 34, 36, 38) and said first and second signals generated by said first and second photodetecting means (12, 24; 49), respectively, to provide said signal representing the position of the stylus (11) wherein the defined area (10). The data entry tablet of claim 23, characterized by first and second radiation emitters (40, 42) spaced apart a predetermined distance and providing radiation detectable by said first and second photodetecting means (12, 14; 49), the pair of light emitters (40, 42) defining a straight edge movable within the area of the tablet; said first and second photodetecting means (12, 14; 49) being operative to detect radiation emitted by said first and second radiation emitters (40, 42) and provide first and second signals representative thereof, respectively; and said processing means (30) being operative in response to said first and second signals and signals from said angular position monitoring means (28, 29, 34, 36, 38) to provide signals representing the position of each radiation emitter (40, 42) and the straight edge within the area (10; 88) of the tablet. The data entry tablet of claim 24, wherein said narrow field of view means (16/20, 18/22; 50/52; 58/60; 62/64) associated with each said first and second photodetecting means (12, 14; 49) is operative to provide a rotating narrow field of view at a predetermined angular velocity. The data entry tablet of claim 24, characterized in that said light emitter (13) is a light emitting diode. The data entry tablet of claim 24, characterized in that said narrow field of view means (16/20, 18/22; 50/52; 58/60; 62/64) is an opaque housing (16, 18; 54) having a slit (20, 22; 56) therein to provide the narrow field of view for radiation receivable by said first and second photodetecting means (12, 14; 49) from the light emitter (13). The data entry tablet of claim 25, characterized in that each of said radiation emitters (40, 42) is coded; said first and second photodetecting means (12, 14; 49) are operative to provide respective coded first and second signals to distinguish between said respective radiation emitters (40, 42). The data entry tablet of claim 25, characterized by a template (44) having a straight edge and including informational characters thereon, said radiation emitters (40, 42) being positioned at opposite ends of said straight edge of said template (44); and means (48) for reading at least one information character of said template (44). The apparatus of claims 1 or 10, characterized in that said selected area (10) is a land area to be surveyed, and said at least one movable radiation source (13a) is a reference pole selectively emitting radiation of predetermined characteristics, said reference pole being movable over said land area. Apparatus for determining the position of a radiation source (13a) located and movable within a selected area (10), comprising: radiation detecting means (49b) for monitoring radiation emitted by said movable radiation source (13a), said radiation detecting means (12, 14; 49) being nonscanning and operating independently of said movable radiation source (13a); and said radiation detecting means (49b) suitable for detecting radiation emitted by said movable radiation source (13a) located within said selected area (10); characterized by means (16/20; 50/52; 58/60; 62/64) disposed in combination with said radiation detecting means (49a) for providing a moving field of view for said radiation detecting means (49a), said moving field of view means (16/20; 50/52; 58/60; 62/64) including a moving reference point (28); means (80) for supporting the combination of said radiation detecting means (49b) and said moving field of view means (16/20; 50/52; 54/56; 58/60; 62/64) at a predetermined distance from a pivot point; means (84, 86) for rotating the combination of said radiation detecting means (49b) and said moving field of view means (16/20; 50/52; 54/56; 58/60; 62/64) around said pivot point; radiation emitted by said movable radiation source (13a) is detected by said radiation detecting means (49b) at first and second locations during rotation around said pivot point due to movement of said moving field of view means (16/20; 50/52; 54/56; 58/60; 62/64) about said radiation detecting means (49b); means for determining (29, 36, 38) the position of said moving reference point (28) of said moving field of view means (16/20; 50/52; 54/56; 58/60; 62/64) with respect to a start position at said first and second locations; means for determining a first angle between said predetermined distance and a first line extending between said first location and said movable radiation source (13a) and for determining a second angle between said predetermined distance and a second line extending from said second location and said movable radiation source (13a); and processing means (30) responsive to said determining means for providing signals representative of the position of said movable radiation source (13a) within said selected area (10). Apparatus for determining the position of at least one radiation source (11/13) located and movable within a selected area (10), comprising: radiation detecting means (49a) for monitoring radition emitted by said at least one movable radiation source (11/13), said radiation detecting means (49a) suitable for detecting radiation emitted by said at least one movable radiation source (11/13) located within said selected area; means for determining a first angle between a base line (L) and a first line extending between a first location and said at least one movable radiation source (11/13) and for determining a second angle between said base line (L) and a second line extending between a second location and said at least one movable radiation source (11/13); and processing means (30) responsive to said determining means for providing signals representative of the position of said at least one movable radiation source (11/13) with said selected area (10); characterized by a pair of fiber optic cables (68) for transmitting radiation emitted by said at least one movable radiation source (11/13), said fiber optic cables (68) having first ends adjacent said radiation detecting means (49a) for coupling radiation thereto and second ends disposed at said first and second locations, respectively, said first and second locations spaced a predetermined distance (L) apart along said base line; means (72) disposed in combination with said second ends of said fiber optic cables (68) for providing a moving field of view at each first and second locations, said moving field of view means including a moving reference point (28); and means for determining (29, 36, 38) the position of said moving reference point (28) of said moving field of view means (72) with respect to a start position when said moving reference point coincides with said first and second lines, respectively, characterized in that said radiation detecting means (49a) is nonscanning and operates independently of said at least one movable radiation source (11/13). A method for determining a position of a radiation source (11/13; 11a, 11b, 11c; 40, 42) movable within a selected area (10; 88) comprising the steps of: emitting radiation having selected characteristics from said movable radiation source (11/13; 11a, 11b, 11c; 40, 42) located within said selected area (10; 88); uniformly scanning said selected area (10; 88) from first and second locations spaced a predetermined distance (L) apart along a base line, said step of uniformly scanning further comprising steps of positioning stationary first and second photodetecting means (12, 14, 49) at said first and second locations, respectively, sequentially exposing incremental segments of each said first and second photodetecting means (12, 14; 49) to said selected area (10; 88) by movable field of view means (16/20, 18/22; 50/52; 54/56; 58/60; 62/64), said sequential exposures occurring independently of movement of said radiation source (11/13; 11a, 11b, 11c; 13a; 40, 42), and monitoring said exposed incremental segments of each said first and second photodetecting means (12, 14; 49) with respect to a movable reference point (28) associated therewith; detecting emitted radiation from said radiation source (11/13; 11a, 11b, 11c; 40, 42) at each said first and second locations, said detecting occurring independently of movement of said radiation source (11/13; 11a, 11b, 11c; 40, 42); correlating said monitored incremental detection segments of said first and second photodetecting means (12, 14; 49) with said detected radiation at each said first and second locations, respectively, to determine a first line of sight between said detected radiation and said first location and a second line of sight between said detected radiation and said second location, respectively; determining a first angle between said base line and said first line of sight and a second angle between said base line and said second line of sight; and computing the position of said radiation source (11/13; 11a, 11b, 11c; 40, 42) within said selected area (10, 88) from said first and second angles and said predetermined distance.

Inventors: LAPEYRE, JAMES M.
Applicants: THE LAITRAM CORPORATION
Application year: 1986
Main classification: G06K11
IPC codes: G01S3, G06F3, G01S5, G01B11