GB2131544A - Optical position location apparatus - Google Patents

Abstract

An optical position location apparatus 20 for locating the position of an object in one or more dimensions relies upon one or more sources of radiant energy 28 and distributor devices 32, 40 to disburse the radiant energy over a location region or window 21. Integrated collector assemblies 41 and 42 positioned opposite to the distributors 32 and 40 receive and collect the transmitted radiant energy and through reflection or refraction, transfer radiant energy to a minimum of detection locations 48 to monitor its absence or alteration. The location apparatus 20 is preferably associated with a visual display device displaying the output of a computer. In this case the location of an object located by the apparatus 20 is fed into and used as a control input for the computer. The apparatus preferably includes a liquid crystal stripe filter to select particular regions of the location region or window 21 to be monitored at any instant. <IMAGE>

Description

SPECIFICATION Optical position location apparatus The present invention relates, in general, to electronic sensing equipment and in particular to an optical position location apparatus for locating the position of an object along one or more coordinate axes and for determining other measurable parameters of the object.

There have been several devices in the past which have optically, or through a combination of mechanical and optical devices, had, as a purpose, the location of an object within a one- or twodimensional frame of reference. Unfortunately, more recent attempts into the field of electro-optical "range finders" and/or "locators" have often been associated with problems which severely limit their effectiveness and use on a large scale. Two such devices are disclosed in United States of America Patent Specification No. 3,184,847, and in an article entitled Let Your Fingers do the Talking in Volume Ill, No. 8, BYTE Magazine, August 1 978 issue, on a non-contact touch scanner.

Our earlier British Patent Specification No. 2,083,218 describes and claims an optical position location apparatus and the present invention relates to improvements in the basic apparatus described in our earlier specification.

According to a first aspect of this invention, an optical position location apparatus for locating the position of one or more objects along one or more coordinate axes of a defined location region, comprises: radiant energy emission means; radiant energy detection means; means for distributing the radiant energy emitted by the radiant energy emission means over a location region from a position along a first portion of the region; collector means positioned along a second portion of the location region which is substantially opposite the first portion of the location region, and cooperating with the distributing means to receive the radiant energy distributed by the distributing means and redirect the radiant energy to the radiant energy detection means; and, means for selectively viewing portions of the distributed and received radiant energy to disclose properties of the radiant energy which has been altered as a result of the object being located within the location region, the apparatus being mounted in front of a visual display means so that objects approaching within close proximity of the surface of the visual display means intrude within the location region of the optical position location apparatus and are detected.

According to a second aspect of this invention an optical position location apparatus for locating the position of one or more objects along one or more coordinate axes of a defined location region, comprises: radiant energy emission means; radiant energy detection means; means for distributing the radiant energy emitted by the radiant energy emission means over a location region from a position along a first portion of the region; collector means positioned along a second portion of the location region which is substantially opposite the first portion of the location region, and cooperating with the distributing means to receive the radiant energy distributed by the distributing means and redirect the radiant energy to the radiant energy detection means; and, means for selectively viewing portions of the distributed and received radiant energy to disclose properties of the radiant energy which have been altered as a result of the object being located within the location region, in which the means for selectively viewing portions of the distributed and received radiant energy comprises electronic scanner means interposed within the path of the radiant energy transmission, the electronic scanner means operably exposing the radiant energy detection means to radiant energy transmitted across individual selected portions of the location region, and in which the electronic scanner means comprises a transmission-type liquid crystal stripe filter, the filter comprising a plurality of adjacent, parallel filter elements which are individually rendered substantially opaque or substantially transparent by associated drive electronics.

Particular examples of apparatus in accordance with this invention will now be described and contrasted with the prior art with reference to the accompanying drawings; in which: Figure 1 is a plan of a scanner apparatus; Figure 2 is a perspective view of a scanner-detector device; Figure 3 is a plan of the optical element of a scanner-detector; Figure 4 is a side elevation of the optical element shown in Figure 3; Figure 5 is a circuit diagram of the scanner; Figure 6 is a circuit diagram of the amplifier circuit shown in Figure 5; Figure 7 is a schematic view of an output display when the location region is empty or unobstructed; Figure 8 is a schematic view of an output display when an object is located in the location region; Figure 9 is a schematic view of an output display showing the output signal without the d.c.

restorer portion of circuitry; Figure 10 is a schematic view of an output display with the d.c. restorer portion of the circuit; Figure 11 is a plan of a stepped echelon mirror assembly; Figure 1 2 is another embodiment of a stepped echelon mirror assembly; Figure 1 3 is a plan of another optical scanner apparatus; Figure 14 is a diagrammatic perspective view of an apparatus; Figure 15 is ;t perspective view showing a television monitor to display positional data derived from the apparatus; Figure 1 6 is a circuit diagram showing the use of an oscilloscope to display the cutput waveform of the apparatus; Figure 1 7 is a circuit diagram of a synchronization signal extraction circuit;; Figure 1 8 is a schematic view illustrating the effects of inserting an opaque object to various depths within the detection region of the device; Figure 1 9 is a schematic view of an output display for various depths of penetration as shown in Figure 18; Figure 20 is a circuit diagram of an alternative embodiment of a portion of the amplifier circuit shown in Figure 6; Figure 21 is a side elevation showing the effect of an opaque object interceding into the space defined by mirror elements oriented at three differing skew angles; Figure 22 is a plan of another embodiment of scanner apparatus using liquid crystal stripe mask scanners in conjunction with the optical detector; Figure 23 is a side elevation of an alternative embodiment of the optical element shown in Figure 22;; Figure 24 is a detailed side elevation of the liquid crystal stripe mask and associated electronics; Figure 25 is a plan of another embodiment of scanner; and, Figure 26 is a plan of a portion of the scanner apparatus showing the use of refractive elements.

The optical scanner described with reference to Figures 1 to 1 3 is described and claimed in our earlier Patent Specification No.2,083,218.

Optical position location apparatus 20 is shown in Figure 1 as including radiant energy emission source 28, here comprising a continuously radiating stationary incandescent light bulb, with shields 27 and 29 and scanner-detector 48 with shields 18 and 19, all in a housing 20a. Shields 27 and 29 preclude the emission of light beams to locations other than those along distributor assemblies 32 and 40.

In this particular embodiment, distributor assembly 32 comprises a series of mirrored surfaces forming a stepped echelon such as mirrored surfaces 33, 34 and 35, capable of reflecting the diverging light beams from light source 28 into a substantially parallel light beam pattern across location region 21. Both collectors 41 and 42 are specificaily designed to enable detector-scanner 48 to rotate a substantially equivalent radial scan angle to monitor a respective equivalent linear distance across location region 21.Accordingly, when detector-scanner 48 is rotating, an equivalent angle of rotation allows the scanner-detector to monitor an equivalent portion of the location region "window" 21 regardless of the path a particular light beam follows in being reflected to cross the window, This particular construction linearizes the output display location coordinate as a function of radial scan angle and, therefore, as a function of time in the devices shown in Figures 7 to 10.

Mirrored surfaces 50 and 51 on distributor 32, and 44 and 45 on distributor 40, are provided in order to distribute radiant energy beams across regions external to the location region 21.

Transmission of light from bulb 28 to location 44 at end A of distributor 40 transmits a beam along the edge 24 of red and infra-red passage filter 23, which beam is then substantially collected by mirrored surface 47 and reflected to scanner-detector 48. Since no object can occupy a position outside of window 21 to interfere with this beam, a signal created by an object located at the very edge of the location region, as displayed in Figure 8, cannot merge with the displayed representation of the shields 1 8, 1 9. Thus, objects even at the periphery of location region 21 are readily distinguished from the effect of the shields, as shown by space 1 24 in Figure 8.

Apparatus 20 discloses the specific embodiment of scanner apparatus for locating and measuring an object's parameters in two dimensions wherein two distributors, 32 and 40, are arranged opposite to collectors 41 and 42, respectively. Since light source 28 is a stationary continuous source of electromagnetic radiant energy, a continuous beam pattern is generated, as exemplified by means 30 and 31 along the X-coordinate and beams 14 and 15 being distributed from distributor 32 to collector 41 in the Y-coordinate. Accordingly, the existence of an object such as object 52 (shown in phantom) would block or otherwise alter radiant energy beam 14 as it is reflected from mirrored surface 33 to mirrored surface 36. Thus, when scanner-detector 48 rotates to review that portion of radiant energy which would otherwise be reflected from mirror surface 36, the output display, as shown in Figure 8, would show object 52 a distance of Y1 relative to the radial time distance from shield 1 8.

While the arrangement of distributors and collectors in the embodiment of Figure 1 are substantially orthogonal, the apparatus could equivalently utilize non-orthogonal or angled scanning beam patterns. Red and infra-red passage filter 23 is utilized to pass only the red and infra-red wavelengths across the position location range and exclude all non-red or non-infra-red stray radiation from entering the apparatus. This reduces the sensitivity of the device to undesirable stray radiation, and seals the substantially toroidal housing to prevent entry of contaminants. Other radiant energy filter means may equivalently be utilized including an all-pass (clear) window.

Non-stepped mirror assemblies may be utilized, such as parabolic mirrors 282-285 shown in Figure 25. However, such configurations may require substantially deep curvilinear mirror forms which greatly enlarge the size and costs associated with the device-problems which are overcome by the specially designed stepped echelon mirrors. In addition, refracting means such as lenses or Fresnel type lenses or refracting-reflecting means such as a mirrored prism, may be used in place of distributors 32 and 40 and/or collectors 41 and 42, to transfer diverging light from light source 28 through refraction and/or refraction-reflection into substantially parallel beams across window 21 or, alternatively, to detection means.Figure 26 illustrates use of focusing lenses 290 in conjunction with distributor 40, wherein reflected beam 291 is further columnated into focused beam 292 by lenses 290.

Optical scanner 48 is shown in Figure 2 as comprising motor 53 with axle 54 connected to optical element 56-57 through attachment member 55. Attached for rotation to optical member 56-57 is view restriction means 61 with apertured slot 62 which permits transmission of analyzed light "portions" to impinge upon detector 60 with electrical leads 63.

Scanner 48 as shown in Figures 1 and 2, rotates to receive radiant energy transmissions from collectors such as collector 41, through only a portion of the transmitted beams are permitted to reach detector 60, as limited by slotted aperture 62. In the preferred embodiment, the length of aperture 62 is selected so that the depth of the region viewed by detector 60 is slightly greater than the thickness of the reflective elements of collectors 41, 42. In this manner, slight axial misalignments of the scanner 43 are tolerated without less of desirable signal, yet extraneous radiation is substantially blocked.

In rotating at a constant speed, reflections from collector 41 are first reviewed by the detector as it rotates clockwise. A period of darkness corresponding to light blocking shield 1 9 is next encountered.

This is followed by the scanner reviewing reflections from collector bank 42, and finally by the absence of light corresponding to shield 1 8. This cycle is then repeated continuously. Preferably, shields 1 8 and 1 9 are black and opaque to more effectively absorb unwanted radiation. Photodetector 60 is maintained in a stationary position above rotating mask 61.

Optical element 56-57 comprises an optically transparent sphere, preferably acrylic, cut into two hemispheres. The lower hemisphere 56 is utilized as a balance to facilitate even rotation of the optical device by motor 53 and shaft 54. Hemisphere 57 has back planar surface 57a which is preferably optically polished. The outwardly exposed surface of hemisphere 57, which is shown in Figure 2 receiving radiant energy beams 58 through 60, acts as a converging lens surface. Total internal refraction takes place at surface 57b due to the nominal index of refraction of the material used (acrylic.having an index of 1.5) as opposed to the 1.0 index of the air space maintained by spacer pins 64 and 65, located at the back planar surface 57a.

The optical device is shown in Figure 3 before top section 68 as shown in Figure 4, has been removed, and through Figures 3 and 4, the construction for the optical device which includes spacer pins 64 and 65 and hemisphere portions 56 and 57 are shown. Spherical sections 66 and 67 are opaqued. Alternatively, they may be cut away and the surfaces so exposed may then be opaqued.

In the preferred embodiment of the scanner-detector, Acrylite 210-0 (Trade Mark) or Plexiglas 2423 (Trade Mark) are used in forming the red and infra-red pass filter 23, sealing off the interior of the "donut-shaped" apparatus assembly. A three-quarter inch (19 mm) diameter acrylic sphere will serve for the optical element 56-57, although glass can equivalently be used. The width of slot 62 is 0.014 inches (0.4 mm). With the front "converging lens" width of hemisphere 57 approximating 0.3 inches (7.6 mm), an approximately 0.3 inch (7.6 mm) wide beam of light from the filament of lamp 28 (G.E. No 194) traverses the location region and passes through slot 62 onto photo-detector 60 which must be spectrally compatible with radiant source 28.In the preferred embodiment, photo-detector 60 comprises silicon photodiode Vactec (Trade Mark) VTS-4085H.

In circuit arrangement 70 of Figure 5, input power applied to +V and OV is at 12 volts d.c. at nominal 0.35 amps, regulated to 5 percent. Lamp 71 is directly connected across the 12 volts. Motor 75 is paralleled by capacitor 74 for noise suppression. Preferably, this capacitor should be a wide band RF bypass type such as a 0.1 to 0.01 microfarad metallized polyester capacitor. Resistors 72 and 73 reduce the 1 2 volts d.c. to a nominal positive 5.7 volts d.c. to produce the desired rotational speed in motor 75. This speed is high enough for the desired scanning rate, yet low enough for good motor life and ease in data processing. A wide range of rotational speeds could be produced by using an appropriate d.c. or a.c. motor driven by an appropriate d.c. to a.c. voltage source.In some applications, a synchronous motor is preferred, and for others, a stepping motor is preferred. The former assures a constant scanning rate; the latter, quantizes the location range without the need for software calculations. An appropriate d.c. motor for use in the preferred embodiment of Figure 1 would be a Mabuchi (Trade Mark) RF-51 0T-1 2620 with a nominal rotation speed of 2400 r.p.m. Photocell sensor 76 is operatively connected to amplifier assembly 77.

Amplifier 77 is shown in Figure 6 as including five separate sections of a CMOS 74C04 hexinvertor. Pin 7 of the 74C04 connects to the OV rail and pin 14 of the 74C04 connects to the positive rail at the cathode of diode 81, thus applying 12 volts less one diode drop to the 74C04, establishing Vcc at approximately 11.3 volts. Alternatively, operational amps 86, 91,92, 99 and 100, with appropriate circuit modifications, each comprise a Texas Instruments To081, a section of Texas Instruments TL084, or a National Semiconductor LM308 amplifier. The first portion of amplifier 77 is a voltage gain stage where 2.2 megohm resistor 85 sets the input current to output voltage gain. A 10 picofarad capacitor 84 rolls off the high frequencies to reduce noise. Resistor 85 also maintains photodiode reverse bias voltage.The output of this stage is coupled by back-to-back, polarized 10 microfarad capacitors 87-88 or alternatively by a 10 microfarad non-polarized capacitor, to second stage input resistor 89. Second operational amplifier 91 is connected to one megohm feedback resistor 90, and with 100 kilohm resistor 89, it yields a nominal voltage gain of 1 0. This output is coupled through capacitor 95 of 0.1 microfarad to 10 kilohm resistor 96, op amp 92 and diode 97 (IN914). Op amp 92 and diode 97 act to clamp the signal so that it cannot go positive of the bias point of the amplifier (nominal 1/2 Vcc). The 470 kilohm resistor 93 holds the output of the capacitor 95 against the clamp level. Elements 92, 93, 96 and 97 constitute a d.c. restorer.The d.c. restored signal (where the most positive d.c. level is 1/2 Vcc) is coupled to a Schmitt trigger 98-101. Op amps 99 and 100 are coupled in the Schmitt trigger to 4.7 megohm feedback resistor 101 and 220 kilohm input resistor 98. 1.5 megohm resistor 94 biases the Schmitt trigger point referred to the input of resistor 98 to slightly negative of the d.c. base line set by the d.c. restorer. Resistor 101 sets the hysteresis along with the 220 kilohm resistor 98 which also affects the input sensitivity. The two 470 ohm resistors, 102 and 103, together with diodes 104 and 106 (IN914) protect the output against static electric discharges or other accidental stress. A 10 microfarad electrolytic capacitor 105 serves as a power supply filter.

Diode 81 protects against damage due to accidental polarity reversal, and can further serve as a rectifier for embodiments using a.c. applied power.

In the circuit arrangement of Figure 6, diode 76 acts as a current source which is light controlled.

In operation, when the scanner-detector 48 of Figure 1 is facing or focusing upon shields 1 8 and 19, the d.c. restorer clamps the signal to 1/2 Vcc. This is the plus-most input to the Schmitt trigger portion of the circuit. The bias resistor 94 of 1.5 megohms, causes the Schmitt trigger to have a net plus input under this condition, and the output is, therefore, near the +12 volt rail (maximum output) of Figure 7. When the scanner looks across the unimpeded range at a view or reflection of lamp 28, the signal level at the photodiode swings relatively negative. The output proximate to capacitors 87 and 88 goes relatively positive and the output at capacitor 95 goes relatively negative. The output after the d.c.

restorer therefore swings negative of the nominal Vcc restorer level. The net input to the Schmitt trigger 98-101 goes negative of the lower trigger level, and the final output goes to the zero volt rail (minimum voltage value-base position) of output as shown in Figure 7. Should an object such as object 52 appear which absorbs or blocks radiation for part of the scan as shown in Figure 1 , where radiation beam 14 would be blocked, then for that portion of the scan, the output of the photo-detector returns to its "dark" level, the output out of the first gain stage goes relatively negative, the second gain stage output goes relatively positive and the signal restorer returns to the 1/2 Vcc base line as shown in Figure 7 with the output going to its first logic position (maximum output position) as shown by outputs 200, 201 in Figure 8.

Accordingly, Figure 7 of the drawings displays the positions of shields 1 8 and 1 9 when no object is interfering with the distribution of radiant energy across the location region. Shield portions 11 3 and 111 in Figure 7 are merely continuations of the same substantially large shield 19 while signal representation 112 displays the logic one display (maximum output position) of smaller shield 1 8 about scanner-detector 48. The position along the X- or X-coordinate axis when an object does register, by altering the light input to photodiode 60 is shown by the variable X (11 5), and variable Y (114), respectively.

Figure 8 depicts a typical output waveform of the device when an object is located within the location region window 21, such as object 52 shown in Figure 1. Logic one level outputs 119 through 121 correspond to the light blockage resulting from shields 1 8 and 1 9 as described above. Additional logic one level outputs 200 and 201 are shown located within the X and Y scan regions 115, 116, respectively. These outputs correspond to the light blockage resulting from an object located within the location region window 21.

Because of the relationship between the scanner rotational angle and the range position along the X and Y coordinate axes, it is possible to deduce from the location and the width of such logic one level outputs 200 and 201 the location and size of the interfering object 52 within the location window 21. Specifically, the offset of the rising edge of output 200 from the zero or beginning point of the X scan 11 5, which offset distance is designated as X1 in Figure 8, corresponds to the location of the nearest edge of interfering object 52 to the zero axis point along the X axis of the location region window 21. Hence, by knowing the functional relationship between the scan angle in degrees represented by this offset X1 and the corresponding linear displacement along the X axis of the location region window 21 , the actual location of object 52 may be determined. In a similar fashion, the location of object 52 along the Y axis may be deduced from the offset Y1 of the rising edge of signal 201 from the zero or null position of Y scan 114.

Additional information may be obtained from the output waveform as shown in Figure 8 relating to the size of interfering object 52 relative to the X and Y axes. Specifically the width of signal 200, shown as delta X in Figure 8, corresponds to the width of object 52 relative to the X axis. Similarly, the width of signal 201, delta Y, corresponds to the size of object 52 relative to the Y axis. Hence, by knowing the relationship between the angular displacement represented by delta X and delta Y and the corresponding linear displacement along the X and Y axes, the size of the object 52 may be determined.

Figure 8 further depicts offset region 210 located between the falling edge of output 119 and the depicted beginning point of X scan 11 5. Similarly, offset region 211 is shown between the end point of X scan 11 5 and the rising edge of signal 120, with offset region 212 located between the falling edge of signal 120 and the beginning point of Y scan 114. Finally, offset region 213 is shown between the end point of Y scan 114 and the rising edge of signal 121.

These offset regions 210 through 213 correspond to uninterruptable light signals which are transmitted external to the location region window 21, such as along its immediate external periphery, from the light source 28 to the scanner-detector 48. The existence of these light signals results in a fixed duration logic zero output just prior to and just following the X and Y scan. These signals may thus be utilized to provide calibration of the detection and/or interpretation circuitry, such as to define the existence and exact size of the X and Y scans 11 5, 11 6. It should be noted that, although such noninterruptable signals are provided for the beginning and ending points of both the X and Y scans in the embodiment whose output is shown by Figure 8, other embodiments may utilize fewer than all of these possible calibration signals as desired.

Figure 9 of the drawings depicts the relative voltage levels existent in a typical output signal prior to operation of the d.c. restorer portion of the circuit. Specifically, the logic one output level 141 is shown as being less than the supply voltage, V (131), and greater than one-half of the supply voltage, 1/2 V (132). The logic zero level 140 is shown as being greater than zero volts but less than one-half of the supply voltage, 1/2 V (132). In this manner, the signal can be seen to "straddle" the one-half supply voltage level.

After operation of the d.c. restorer circuit, the logic zero level 1 45 of the resulting waveform is near to the zero voltage reference, as depicted in Figure 10. In addition, the resulting logic one level 135 is substantially equal to one-half of the supply voltage, 1/2 V (132).

This resulting signal is then amenable to processing by the Schmitt trigger portion of the circuit as previously described. Depicted on Figure 10 are the relative voltage levels C and D relating to the break points of a typical Schmitt trigger stage. As can be seen, this resulting waveform is readily amenable to processing by such Schmitt trigger devices in order to accurately indicate the transition points relating the desired position data.

Figure 11 shows the specially designed 29 facet stepped echelon mirror assembly in which the peaks of the mirrors are a constant dimension from one another in succession, here 0.2 inches (5.08 mm).

In the embodinient of Figure 11, the following angular reiationships exist: All beta angles=90 degrees Alpha Deg. Min. Alpha Deg. Min. Alpha Deg. Min.

1. 27 15 11. 34 10 21. 41 10 2. 28 00 12. 34 55 22. 41 50 3. 28 40 13. 35 35 23. 42 30 4. 29 20 14. 36 20 24. 43 15 5. 30 00 15. 37 00 25. 43 55 6. 30 45 16. 37 40 26. 44 35 7. 31 25 17. 38 20 27. 45 20 8. 32 05 18. 39 05 28. 46 00 9. 32 50 19. 39 45 29. 46 40 10. 33 30 20. 40 25 The position of the peaks are further defined by vertical dimensions from a horizontal datum.

These are tabulated below (the values in inches are also marked on Figure 11).

Vertical Dimension Vertical Dimension Alpha ins. mm. Alpha ins. mm.

1. 1.147 29.13 16. 1.468 37.29 2. 1.246 31.65 17. 1.411 35.84 3. 1.332 33.83 18. 1.344 34.14 4. 1.406 35.71 19. 1.269 32.23 5. 1.469 37.31 20. 1.184 30.07 6. 1.520 38.61 21. 1.090 27.69 7. 1.560 39.62 22. .987 25.07 8. 1.589 40.36 23. .875 22.23 9. 1.608 40.84 24. .754 19.15 10. 1.617 41.07 25. .622 15.80 11. 1.616 41.05 26. .482 12.24 12. 1.605 40.76 27. .331 8.407 13. 1.585 40.26 28. .171 4.343 14. 1.555 39.50 29. 0 0 15. 1.516 38.51 In Figure 12 of the drawings, an 1 8 facet stepped echelon mirror is shown in which peaks are spaced 0.375 inches (9.52 mm) apart. In Figure 12, the angles are as follows: All beta angles=90 degrees Alpha Deg. Min. Alpha Deg. Min. Alpha Deg. Min.

1. 16 56 7. 32 44 13. 40 34 2. 20 56 8. 34 20 14. 41 34 3. 24 05 9. 35 47 15. 42 30 4. 26 42 10. 37 08 16. 43 23 5. 28 58 11. 38 22 17. 44 12 6. 30 57 12. 39 30 18. 45 00 As with Figure 11 , the positions of the peaks are further defined by vertical dimensions from a horizontal datum. These are tabulated below (the values in inches are also marked on Figure 12).

Vertical Dimension Vertical Dimension Alpha ins. mm. Alpha ins. mm.

1. 1.043 26.50 10. 1.159 29.44 2. 1.209 30.71 11. 1.058 26.87 3. 1.311 33.30 12. .944 23.98 4. 1.368 34.75 13. .816 20.73 5. 1.392 35.36 14. .676 17.17 6. 1.388 35.25 15. .523 13.28 7. 1.360 34.54 16. .360 9.144 8. 1.311 33.30 17. .185 4.699 9. 1.243 31.57 18. 0 0 It should be realised that facets such as 191 in Figure 11 or 1 55 and 1 56 in Figure 1 2 can be substantially planar in form or curved as shown in phantom, so as to "focus" the light reflected thereby.

Additionally, the number of surfaces being utilized in a particular application can be optimized relative to produceability, economics, edge losses, resolution and echelon assembly depth. However, the particular design of Figure 11 makes possible a linear output display due to the capability of the detector-scanner to "review" or focus upon respective equivalent distances across the location region window as a function of respective substantially equivalent radial scan angles. The particular construction of this stepped echelon mirror assembly also makes possible the control of intensity so that intensity is substantially equivalent across the window 21 regardless of the coordinate position being reviewed. For shallower mirrors than that of Figure 11, such as Figure 12, a trignometric or other function must be used in conjunction with the display device since the location of an object will now be a non-linear function of the radial scan angles at which the object is detected.

In terms of resolution, it is necessary to develop pitch spacing between the facets of a particular mirror assembly which is smaller than the smallest object desired to be resolved. Alternatively, the mirror facets can be skewed to parallelogram form to eliminate shadows. Specifically, as shown in Figure 21, minor shadow regions 253 may occur between the reflective regions 254. Such shadow regions may result from eiement-to-element shading of the individual mirror facets, or from edge effects of the Fresnel mirror configuration. No radiant energy is transmitted or received in association with these shadow regions.Although the shadow regions 253 are of little consequence with respect to objects which have dimensions substantially greater than the width of the shadow regions 253, it may be possible for narrow objects to fall completely within such a shadow region and thereby go undetected. For example, if object 52 is inserted within the reflective region 254a of the standard stepped echelon mirror shown in side view in Figure 21(a), it will result in a light blockage corresponding to shaded region 263, and will be detected. However, if the item is inserted into one of the shadow regions 253, no light blockage results, as shown by region 264, and the object will not be detected.

In order to overcome the possibility of objects which are perpendicular to the location regicn 21 going unnoticed, the individual mirror elements may be skewed such that the faces of the facets form parallelograms as shown in side view in Figure 21(b). By selection of an appropriate skew angle, it is possible to create a configuration such that even narrow objects will provide at least partial blockage of one or more reflective areas 253b, as shown by shaded region 265, even if other portions of the object fall within the shadow regions 254b, such as region 266. Excessive skew, however, may result in decreased accuracy and resolution, for all objects inserted may then intercept two adjoining regions.

This is illustrated by Figure 21(c), wherein object 52 will be detected within two adjoining regions as a result of areas 267, with region 268 being unregistered. Finally, although in the preferred embodiment the skew of the mirror facets of the detectors is designed to be the equivalent, mirror image of the skew of the facets of the distributors, such that light beams of parallelogram cross-section are distributed and received, other configurations are possible. For example, it is possible to provide opposite relative skew to the facets of the collector in order to provide further blending.

In another embodiment optical element 57 is stationary facing toward shield 29, and shield 1 8 is removed. Mask 61 is not required. Detector 60 is Fairchild Semiconductor CCD1 10 "Linear Image Sensor" or equivalent, and in combination with appropriate circuitry and element 57 constitutes both selective viewing means and detection means.

In another embodiment the means for selectively viewing portions of transferred radiant energy occurs at other locations along the radiant energy transmission path. For example, instead of utilizing a rotating "scanner-detector", as previously described, a stationary detector may be utilized with a projecting-scanner-emitter. Referring to Figure 2, in the scanner-emitter embodiment, former photocell 60 becomes light-source 60, with elements 61,62 and 53 through 57 assuming the same structures as previously described.

Scanner-emitter 48 would replace scanner-detector (48) between banks 41 and 42 to transmit radiant energy across "window" 21 in a direction opposite to the arrow heads shown in Figure 1.

Transmissions and/or alterations,in the energy thus transmitted are picked up by stationary photocell assembly 28 within shields 27 and 29. In this embodiment, the collector assemblies become distributor assemblies and vice versa.

Alternatively, electrochemical, electromechanical, mechanical, or electronic shutter means such as liquid crystal display elements or aperture slots moved by loud speaker, solenoid, or piezo-electric transducers, may be interposed at appropriate positions along the radiant energy transmission path, to enable selective viewing of the transmitted radiant energy emissions. Figure 22 illustrates such an alternative embodiment utilizing an electronic scanning means cooperating with the detector. Liquid crystal stripe filters 270 are located within the path of the radiant energy beams. As shown in Figure 24, the stripe filters comprises a multiplicity of parallel, adjacent transmission-type liquid crystal elements 271.These individual stripes are oriented to lie in optical alignment between the radiant energy detector and the collectors 42,41 such that each individual mirror facet of collectors 42,41 is in alignment with one or more of the filter stripes 271.

In operation, a single element, such as element 272, is rendered transparent to the radiant energy while other elements 271 are rendered opaque to such energy. Thus, the transmitted radiant energy is absorbed by stripe filter 270, with the exception of that portion of such energy which corresponds to a single location beam 273. By successively causing individual elements 271 to be sequentially rendered transparent in this manner, an electronic scan of the received radiant energy results.

In the preferred embodiment illustrated in Figure 22, stripe filters 270 are located proximate to the detector near the point of convergence of the light beams. In this manner, the linear dimensions of the stripe filter 270 may be held to a minimum, thereby reducing production costs. In addition, as illustrated in Figure 22, in the preferred embodiment the liquid crystal stripe filter 270 is plated for insertion into cooperating socket 273. Drive electronics 274 are mounted proximate to socket 273 and connected by printed circuit wiring 276 applied to the mounting substrate 275, resulting in united, inexpensive construction. The liquid crystal stripe filters 270 may be either multiplexed or direct drive types.

The drive electronics 274 in the preferred embodiment cause an element-by-element scan first of the liquid crystal stripe filter 270 located within the x-axis radiant energy field, and then of the corresponding filter 270 located within the y-axis field. This operation may be repeated continuously, allowing light from only a single x- or y-axis relative position to reach the detector at a given time. In this manner, only a single radiant energy detection element need be utilized. Alternatively, the stripe filters 270 may be simultaneously scanned, with individual detectors utilized in conjunction with each to simultaneously determine both the x- and y-coordinate positions. Scan rates of twice the frequency are thus possible.

Figure 23 shows a preferred embodiment for a single detector configuration for use in conjunction with, for example, the electronic scanner shown in Figure 22. An optical element 56 intercepts radiant energy which passes through the transparent elements of stripe filters 270, and reflectively and refractively transmits such energy to detector 277. Optical element 56 is preferably made of plastic, such as acrylic which has an index of refraction of approximately 1.5. Other plastics or glass may be used. Optical element 56 comprises a sphere 281 into which a 450 cone 280 is milled.

The resulting conical surface of cone 280 is preferably optically polished.

The light passed by the stripe filters 270 strikes element 56 and is refracted by the spherical element 281, striking the surface of the milled cone 280. Because of the differences in indexes of refraction of the material of sphere 281 and the ambient air, total refraction occurs at the surface of cone 280, thereby directing the light substantially axially through sphere 281. This light is further refracted by sphere 281, and is focused thereby onto the detection element 277. Because of the radial symmetry of optical element 56, light from any radial direction is similarly refracted and reflected axially and detected by element 277. Alternatively, other methods known in the art may be utilized to collect and detect the radiant energy passed by stripe filters 270.

Figure 1 3 represents yet another embodiment of the present apparatus wherein a plurality of light emitting diodes are provided which function as both the radiant energy emission means and as the distributor means. Specifically, a multiplicity of light-emitting diodes are arranged along each of two of the axes of the location region window 1 86 such that the radiant energy output of the devices is transmitted in substantially parallel beams across the location window 1 86. These diodes are represented in Figure 13 by, for example, LED 1 63, 1 64, 1 65, 1 66, 1 67 and 1 68. The beams so generated may be further columnated by utilization of picket frame 1 81, containing a plurality of apertures 1 80. Integrated collector banks 1 61 and 1 62 serve to equivalently reflect transmitted light, (or the absences thereof) to detection device 1 82 which consists of back-to-back photodetectors 1 83 and 184. Alternatively, the detector configuration shown in Figure 23 may be used. Picket frames 181, which could be macro or micro louvers and which completely encircle the location region 186, serve to restrict the emitted light into parallel beams.

In order to selectively view or scan portions of the radiant energy and to establish a frame of reference relative to which one of the LED beams is being blocked, should an object appear within window 186, the LEDS themselves are pulsed in successive order at a desired rate to create a scantime signal similar to that of the embodiment of Figure 1. Through such a technique, as well as through the alternative use of a scanner-emitter or stripe filter mask scanners, only one or two photodetector devices are required to "interpret" the transmission and alteration characteristics resulting from the location of an object within location region 1 86.

Figure 14 depicts use of the optical position location apparatus 20 in conjunction with a television monitor 201 to create an interactive data input device. Specifically, apparatus 20 is mounted directly to the front surface of monitor 201 such that the toroidal housing 20a surrounds the television screen 209. The output 204 of the apparatus is in one embodiment connected by means of lead 207 directly to the input 205 of a microprocessor system 202. Alternatively, a programmable interval timer 203 may be inserted between points A and B of Figure 14, such that the device output 204 is supplied to the programmable interval timer 203, and the output of such interval timer 203 is then applied to the microprocessor input 205. Finally, the interactive loop is completed by supplying the television monitor 201 with an appropriate output 206 generated by the microprocessor 202.

In use, the microprocessor 202 presents, for example, a menu of selections to the monitor 201.

These selections appear as identified regions 208, 211 on the television screen 209. The user may then select among these options and indicate a finger 210. Alternatively, a suitable stylus may be used.

When the user's finger 210 touches the television screen 209, it also is interceding within the location region 21 of the position apparatus 20. Data corresponding to the location of this interceding object 210 is transmitted to appropriate analyzing circuitry. In one embodiment, the output goes directly to the microprocessor 202. In another embodiment, a programmable interval timer 203 is inserted. The interval timer 203 generates outputs corresponding to the respective lengths of the "on" and "off" portions of the signal received. As previously discussed, these "on" and "off" time periods correspond to the location and size of the interceding object 21 0. Although the microprocessor 202 may perform the requisite timing interpretations itself, use of a programmable interval timer 203 may be preferable in order to reduce computational overhead of the microprocessor 202.

By correlating the received data pertaining to the location of object 210 and the displayed menu selections 208,211, the microprocessor may determine which of the selections has been chosen, and an appropriate response may be initiated. In a preferred embodiment, the selection chosen may be highlighted as shown by menu element 211 in order to provide visual feedback to the operator that a selection has been, or shortly will be, recognized by the microprocessor 202. In this manner, an inexpensive yet extremely flexible and user-friendly data input or programming device results which frees the user from the need for cumbersome, confusing or intimidating keyboard input.

Under certain circumstances it may be desirable to have available a display corresponding to the location of an interceding object other than that previously described. In one embodiment shown in Figure 15, an interface 220 is provided which generates an output on television monitor 201 corresponding to the positioned location of an interceding object 210. For example, that portion 21 2 of the television picture corresponding to the location of any interceding object 210 may be highlighted.

In this manner, a direct graphic representation of both the size and location of any interceding objects results.

Figure 1 6 illustrates yet another means for visually displaying the output data of optical position location device 20. Specifically, outputs of the device such as those shown in Figure 5 may be supplied to the input of an oscilloscope 222 by means of input lines 225. In order to achieve a stable, constantly updated display, it is necessary to repetitively trigger the oscilloscope 222 at the same point on each successive output waveform. This may be accompl;shed by use of a synchronization signal extractor circuit 221, whose output is supplied by means of sync lines 224 to the synchronization signal input of oscilloscope 222. A stable representation 223 of the output waveform is thereby displayed on the face of the oscilloscope cathode ray tube, from which desired data may be measured.

A preferred embodiment for the synchronization signal extractor circuit 221 of Figure 1 6 is shown in Figure 1 7. The circuit includes a negative integrator comprising amplifier 230, feedback resistor 233 in parallel with feedback capacitor 232, and input resistor 231. The negative integrator is connected to a detection and peak clamping circuit comprising transistor 234, storage capacitor 236, and bleed resistor 237. The output is generated across collector resistor 235.

In operation, the output of amplifier 230 is initially at a high, positive level. Upon application of a positive input, the negative integrator performs a negative time average integration of the input signal, resulting in a declining output voltage from amplifier 230. The values of input resistor 231, feedback resistor 233, and feedback capacitor 232, as well as the gain of amplifier 230, are selected so that the saturation time of the resulting negative integrator is somewhat greater than the duration of the longest high-level input expected. As shown in Figure 8, such high-level inputs result when the light is blocked from the detector element, such as by shield 1 8 of Figure 1. In the preferred embodiment, the longest duration high-level input will correspond to light blockage caused by one of the light blocking shields, such as by shield 18 of Figure 1.

Peak storage capacitor 236 is charged positively by bleed resistor 237. The time constant of the resulting circuit is chosen to be substantially greater than the duration of a full rotation of the optical scanner. In the preferred embodiment, this time constant may be 10 times the duration of a single rotation. In this manner, bleed resistor 237 will not cause the voltage of storage capacitor 236 to change appreciably during a single cycle of the circuit operation.

In addition to serving in conjunction with capacitor 236 and resistor 237 as a peak holding circuit transistor 234 serves as a detector element. Specifically, the synchronization signal extractor circuit is designed to recognize the longest duration high-level input corresponding, as discussed, to one of the light blocking shields. This longest duration input causes the output of amplifier 230 of the negative integrator to reach its lowest level of ouptput. At this time, transistor 234 turns on briefly, restoring the peak level to capacitor 236. In addition, the resulting collector current through collector resistor 235 causes an output voltage signal which may be utilized to trigger oscilloscope 222. In this manner, an identical reference point within each succeeding waveform is established.

In addition to determining the location and size of an object relative to the coordinate axes of the device, one embodiment of the present invention is capable of further approximating the depth of penetration of an opaque object or, alternatively, the height of objects which are shorter than the depth of the measuring field itself. Such determinations may be extrapolated from data pertaining to the intensity of the received signals. As shown in Figure 1 8, the individual light rays which comprise the location determining rays previously discussed may have a fixed and significant "thickness" or depth normal to a plane described by the measurement axes themselves. In the preferred embodiment, this may be on the order of .3 to .5 inches, although it will be seen that other depths are possible.The light which is distributed by, for example, distributors 40 and 32 of Figure 1 may preferably have substantially equal intensity throughout the depth of the resulting beams. In this manner, for opaque objects wider than the particular light beam, the intensity of the unblocked light which is received by the detector will correspond inversely to the average depth of penetration of the object. For example, object 52b inserted approximately halfway into the location region 21 will intercept approximately one-half of the incident light rays 242, and correspondingly will permit the remaining one-half of the light rays 243 to pass to the detector. As shown in Figure 19, the resulting outputs 200b, 201 b corresponding to the unobstructed portion 243 of the incident light 242 will have a correspondingly reduced level when compared to the output 200a, 201 b which would result from complete blockage such as by item 52d.

In order to utilize such depth of penetration data, it is necessary to retain the analog d.c. level of signals 200, 201. In the circuit shown in Figure 6, such intermediate levels are removed by the Schmitt trigger circuit previously described. Therefore, in the preferred embodiment for use in conjunction with depth of penetration indication, the Schmitt trigger is replaced by the circuit shown in Figure 20.

Specifically, inverters 99 and 100 are configured as linear amplifier stages by use of input resistors 98, 251, and feedback resistors 250, 252, respectively. Output resistor 102 is retained, although bypass resistor 94 is deleted. The resulting linear circuit is inserted between nodes 260 and 261 in Figure 6 in lieu of the Schmitt trigger configuration.

Finally, it may be desirable to utilize techniques known in the art to provide for automatic gain control and compensation of the linear output data, in order to correct for variations in the output of the radiant energy emission means 28. The previously discussed calibration beams passing external to the location region 21, corresponding to offset regions 210-213 of Figure 8, may advantageously be utilized for this purpose.

Claims (57)

Claims

1. An optical position location apparatus for locating the position of one or more objects along one or more coordinate axes of a defined location region, comprising: radiant energy emission means; radiant energy detection means; means for distributing the radiant energy emitted by the radiant energy emission means over a location region from a position along a first portion of the region; collector means positioned along a second portion of the location region which is substantially opposite the first portion of the location region, and cooperating with the distributing means to receive the radiant energy distributed by the distributing means and redirect the radiant energy to the radiant energy detection means; and, means for selectively viewing portions of the distributed and received radiant energy to disclose properties of the radiant energy which have been altered as a result of the object being located within the location region, the apparatus being mounted in front of a visual display means so that objects approaching within close proximity of the surface of the visual display means intrude within the location region of the optical position location apparatus and are detected.

2. An apparatus according to claim 1, which also includes computing means coupled to the visual display means so that an output of the computing means drives a display on the visual display means, and in which the output of the optical position location apparatus is supplied to the computing means so that the location of the object intruding within the location region supplies input data associated with the display to the computing means.

3. An apparatus according to claim 2, in which the display is a menu of the computing means and in which a particular selection from the menu is selected by positioning an object adjacent that particular selection on the display.

4. An apparatus according to any one of the preceding claims, in which the radiant energy detection means is operably coupled via signal processing means to the visual display means so that the visual display means displays the location of an object in the location region.

5. An apparatus according to claim 1, 2 or 3, in which the visual display means is a cathode ray tube display apparatus.

6. An apparatus according to any one of the preceding claims, in which the radiant energy emission means comprises a plurality of individual radiant energy sources, and in which the distributing means comprises the mounting of the individual sources in spaced relationship along the first portion of the location region whereby a plurality of substantially discrete beams results.

7. An apparatus according to claim 6, in which the plurality of the radiant energy sources comprises light emitting diodes.

8. An apparatus according to claim 7, in which the radiant energy detection means comprises one or two photodetectors cooperating with the collector means, the means for selectively viewing portions of the distributed and received radiant energy comprising means for sequentially energizing the light emitting diodes.

9. An apparatus according to any one of the preceding claims, in which the means for selectively viewing portions of the radiant energy includes scanner means which rotate relative to the collector means selectively to transfer to the radiant energy detection means radiant energy received by the collector means from specific locations of the location region.

10. An apparatus according to claim 9, in which the scanner means comprises: optical element means, the optical element means directing the radiant energy received from the collector means to the radiant energy detection means; motor means, the motor means operably connected to the optical element means whereby the optical element means is made to rotate with respect to the collector means; the rotating optical element means thereby scanning portion-by-portion across one coordinate axis of the location region described by one respective collector means and then, in turn, scanning across each of the remaining coordinate axes described by the remaining collector means, in sequence.

11. An apparatus according to claim 10, wherein the scanner means further comprises means for view restriction, the view restriction means cooperating with the optical element means to restrict the portion of radiant energy received by the radiant energy detection means to a defined beam; the beam comprising only the radiant energy received by that localized portion of the collector means which is instantaneously in optical alignment with the combination of the rotating optical element means, the view restriction means, and the radiant energy detection means; the radiant energy received by individual localized portions of the collector means being thereby sequentially and selectively monitored by the radiant energy detection means.

12. An apparatus according to claim 11, wherein the view restriction means comprises apertured mask means, the apertured mask means having a dimensioned aperture therein or being located in optical alignment with the optical element means and the radiant energy detection means.

1 3. An apparatus according to claim 1 0, 11 or 12, wherein the scanner means further comprises shield means, the shield means substantially preventing radiant energy approaching from positions other than those associated with the collector means, from impinging on the optical element means and reaching the radiant energy detection means.

14. An apparatus according to claim 10, 11, 1 2 or 13, in which the optical element means comprises a substantially spherical element having fabricated therein a substantially diagonal-cut plane portion for redirecting the received radiant energy to the radiant energy detection means.

1 5. An apparatus according to any one of claims 10 to 14, which includes amplifier means, the motor means being coupled to the radiant energy emission means, to the radiant energy detection means and to the amplifier means in an electrical circuit; the motor means further including electrical filter means in parallel connection therewith to reduce commutator noise from the motor means; the motor means further including speed control means to produce a desired rotational speed in the motor means; the motor means further being connected in parallel connection to the amplifier means; and, the amplifier means being operably connected to the radiant energy detection means to receive signals from it.

1 6. An apparatus according to any one of claims 1 to 7, in which the means for selectively viewing portions of the distributed and received radiant energy comprises mechanical shutter means interposed within the path of the radiant energy transmission, said mechanical shutter means operably exposing the radiant energy detection means to radiant energy transmitted across selected individual portions of the location region.

17. An apparatus according to claim 16, in which the mechanical shutter means comprises an apertured slot assembly operably controlled by shutter control means.

1 8. An apparatus according to any one of claims 1 to 7, in which the radiant energy detection means and the means for selectively viewing portions of the distributed and received radiant energy are integrated into a substantially singular component, the singular component comprising a linear image sensor.

1 9. An optical position location apparatus for locating the position of one or more objects along one or more coordinate axes of a defined location region, comprising: radiant energy emission means; radiant energy detection means; means for distributing the radiant energy emitted by the radiant energy emission means over a location region from a position along a first portion of the region; collector means positioned along a second portion of the location region which is substantially opposite the first portion of the location region, and cooperating with the distributing means to receive the radiant energy distributed by the distributing means and redirect the radiant energy to the radiant energy detection means; and, means for selectively viewing portions of the distributed and received radiant energy to disclose properties of the radiant energy which have been altered as a result of the object being located within the location region, in which the means for selectively viewing portions of the distributed and received radiant energy comprises electronic scanner means interposed within the path of the radiant energy transmission, the electronic scanner means operably exposing the radiant energy detection means to radiant energy transmitted across individual selected portions of the location region, and in which the electronic scanner means comprises a transmission-type liquid crystal stripe filter, the filter comprising a plurality of adjacent, parallel filter elements which are individually rendered substantially opaque or substantially transparent by associated drive electronics.

20. An apparatus according to any one of the preceding claims, wherein the radiant energy emission means, the distributing means, the collector means, and the radiant energy detection means are operably positioned within an enclosed generally annular housing member, the location region comprising the aperture enclosed by the housing member.

21. An apparatus according to any one of the preceding claims, in which the apparatus includes only one radiant energy emission means, only one distributing means, only one collector means, and only one radiant energy detection means for determining the location and/or other parameters of the one or more objects along only one coordinate axis.

22. An apparatus according to any one of claims 1 to 20, in which the apparatus includes two substantially separate distributing means, two substantially separate collector means respectively aligned with the two distributing means, and radiant energy detection means for determining the location of the one or more objects along two coordinate axes.

23. An apparatus according to any one of the preceding claims, in which the intensity of radiant energy received from a portion of the location region corresponding to the presence of the one or more objects is used to determine other measurable parameters of the one or more objects, such as the depth of penetration of the object.

24. An apparatus according to any one of the preceding claims, in which the radiant energy comprises infra-red radiation.

25. An apparatus according to any one of claims 1 to 23, in which the radiant energy comprises unpolarized visible light.

26. An apparatus according to any one of the preceding claims, in which the means for selectively viewing a portion of the radiant energy comprises a light projecting scanner-emitter which rotates relative to the distributing means selectively to transmit light at different locations across the location region.

27. An apparatus according to any one of the preceding claims, in which the detection means comprises photodetector means cooperating with the collector means, The photodetector means producing electrical responses relative to the radiant energy received, thereby disclosing the existence of any alterations of radiant energy properties corresponding to objects in the location region, the instantaneous angular position of the scanner-emitter at the time of occurrence of the electrical response being functionally related to the position of the object within the location region.

28. An apparatus according to claim 1 9 or any one of the preceding claims, when dependent upon claim 19, in which the radiant energy emission means comprises a plurality of individual radiant energy sources, and in which the distributing means comprises the mounting of the individual sources in spaced relationship along the first portion of the location region whereby a plurality of substantially discrete beams results.

29. An apparatus according to claim 28, in which the plurality of the radiant energy sources comprises light emitting diodes.

30. An apparatus according to any one of claims 1 to 27, in which the radiant energy emission means comprises a substantially stationary, continuous emitter.

31. An apparatus according to any one of the preceding claims, in which the radiant energy detection means is a silicon photocell.

32. An apparatus according to any one of claims 1 to 30, in which the radiant energy detection means is a photodiode operated in the reverse biased mode.

33. An apparatus according to any one of claims 1 to 30, in which the radiant energy detection means comprises a phototransistor.

34. An apparatus according to any one of the preceding claims, in which the radiant energy emission means includes blockage means to intercept and absorb radiant energy directed to locations other than those occupied by the distributing means.

35. An apparatus according to any one of the preceding claims, wherein the invention further includes signal output means, the signal output means comprising: detector buffer means, the detector buffer means responding to the electrical output signal of the radiant energy detection means and generating a corresponding buffer output signal; and, signal output means connected to the output of the detector buffer means whereby the signal output means responds to the buffer output signal to create a device output signal representative of the altered parameters of the received radiant energy.

36. An apparatus according to claim 35, wherein the detector buffer means comprises: amplifier means, the amplifier means generating the buffer output signal which is a first variable voltage output signal; the amplifier means including gain determining means and electrical filter means for suppressing input signals having undesired frequencies.

37. An apparatus according to claim 35 or 36, wherein the signal output means comprises output discriminator means which produces a first discriminator output signal when the buffer output signal corresponds to the absence of an object within the relevant portion of the location region; and which produces a second discriminator output signal substantially distinct from the first output signal when the buffer output signal corresponds to the presence of an object within the location region.

38. An apparatus according to claim 37, wherein the output discriminator means comprises d.c.

restorer means, being arranged to add or subtract a given voltage to the buffer output signal, producing a d.c. restored signal; and Schmitt trigger means which produce a first, logic-one level output when the d.c. restored signal rises above a first predetermined voltage level, and produce a second, logic-zero level output when the d.c. restored signal falls below a second predetermined voltage level.

39. An apparatus according to claim 35 or 36, wherein the signal output means comprises analog output means which produce an output signal whose magnitude is substantially related to the intensity of the radiant energy received by the radiant energy detection means.

40. An apparatus according to claim 39, wherein the analog output means comprises linear amplifier means.

41. An apparatus according to claim 1 9 or any one of the preceding claims when dependent upon claim 19, wherein the radiant energy detection means is operably coupled via signal processing means to visual display means for visual interpretation of the radiant energy detected by the radiant energy detection means.

42. An apparatus according to claim 1, wherein the apparatus further comprises radiation filter means interposed between the distributing means and the collector means for the purpose of precluding interference from daylight and other radiant energies of wavelengths other than those of the intended radiant energy being emitted, distributed and collected for detection.

43. An apparatus according to claim 42, wherein the filter means comprises a red-and-infra-red transmitting filter interposed between the distributing means and the collector means.

44. An apparatus according to any one of the preceding claims, wherein the distributing means distributes radiant energy at positions outside of the location region so as to describe radiant energy routes which cannot be altered or broken by objects Iccated within the location region, the radiant energy traversing such resulting unalterable radiant energy routes and being detected by the radiant energy detection means and thereby creating reference signals.

45. An apparatus according to any one of the preceding claims, wherein the distributing means comprise a stepped echelon mirror assembly including a plurality of faceted mirror elements, the faceted mirror elements are individually oriented with respect to the radiant energy emission means and to the location region to receive a portion of the radiant energy emitted by the radiant energy emission means and thereafter transmit it across a selected portion of the location region.

46. An apparatus according to any one of the preceding claims, wherein the collector means comprise a stepped echelon mirror assembly including a plurality of faceted mirror elements, the faceted mirror elements are individually oriented with respect to the location region and the radiant energy detection means to receive radiant energy from a selected portion of the location region and thereafter transmit it to the radiant energy detection means.

47. An apparatus according to claim 45 or 46, wherein the faceted mirror elements are oriented with respect to the radiant energy emission means, the radiant energy detection means and the location region such that the radiant energy is transmitted across the location region in substantially parallel beams spaced substantially evenly across the location region.

48. An apparatus according to claim 46 when dependent upon claim 9, wherein the faceted mirror elements are oriented with respect to the location region and to the scanner means so that the faceted mirror elements individually receive radiant energy from portions of the location region which are substantially parallel to one another and which are spaced substantially evenly across the location region, each of the faceted mirror elements further being in optical alignment with the scanner means for substantially equal incremental angular portions of the rotation of the scanner means, the separation between the centres of each of the faceted mirror elements corresponding to substantially equal incremental angular portions of the rotation of the rotating scanner means, whereby a substantially linear relationship exists between the instantaneous angular position of the rotating scanner means, and the transverse location of that selected portion of the location region from which radiant energy is being instantaneously received by the radiant energy detection means via the stepped echelon mirror assembly.

49. An apparatus according to claim 45, 46, 47 or 48, in which the reflective surfaces of the faceted mirror elements comprise longitudinally skewed parallelograms with sides transversely angled to the axes, whereby adjacent reflected beams overlap relative to a datum normal to the plane described by the coordinate axes of the distributing means and collector means, resulting in substantially continuous illumination across the location region.

50. An apparatus according to any one of claims 45 to 49, wherein the stepped echelon mirror assembly comprises 29 individual faceted mirror elements, each of which is substantially 5 mm wide with respect to a datum line defining a linear axis, and which range in depth relative to a datum line parallel to the linear axis and contiguous to the outermost edge of the outermost extending faceted mirror element, a distance varying between 4.1 mm and 4.3 mm in substantially curvilinear fashion.

51. An apparatus according to any one of claims 45 to 50, wherein each of the faceted mirror elements receives a substantially equal portion of radiant energy from the radiant energy emission means.

52. An apparatus according to any one of claims 45 to 51, wherein one or more of the faceted mirror elements include curved mirror surfaces for providing reflective focusing of the radiant energy.

53. An apparatus according to any one of claims 1 to 44, in which the distributing means comprise a non-stepped mirror assembly for receiving radiation from the radiant energy emission means and distributing the radiant energy across the location region.

54. An apparatus according to any one of claims 1 to 44 or 53, in which the collector means comprise a non-stepped mirror assembly for receiving the radiant energy distributed over the location region and reflecting the radiant energy to the radiant energy detection means.

55. An apparatus according to any one of the preceding claims, in which one or more of the distributing means includes refractive means positioned along the first portion of the location region, the radiant energy being focused across the location region by refraction.

56. An apparatus according to any one of the preceding claims, wherein one or more of the collector means includes refractive means.

57. An apparatus according to any one of the preceding claims, in which the apparatus further includes: a fixed optical element; the fixed optical element comprising a substantially hemispherical, transparent section; the fixed optical element having a conical portion removed from its centre, the axis of the removed conical portion corresponding to the axis of the hemispherical section; the resulting conical surface in the optical element being optically polished, whereby incident radiant energy entering the optical element from various radial positions is refracted and redirected by the optical element and leaves the optical element substantially along the axis; the radiant energy detection means being located along the axis of the optical element to receive the redirected radiant energy.