GB1570641A - Object position and surface determining methods and apparatus - Google Patents

Abstract

The position determining device (10) exhibits a mask (16) which can be displaced along an axis (T) located in the reference plane. A light source (20) can be displaced together with the mask (16). A sequence of photocells (26) with a lens (26a) contains photocells (PC1-PC7). The mask (16) contains transparent sections and opaque sections. Planes (P1, P2, P3), in which the radiation-reflecting objects (O1, O2, O3) are located extend in parallel with the said axis (T). The time required by the radiation pattern to pass over a location in the planes (P1, P2, P3) is a measure of the distances (x1, x2, x3). When light source (20) and mask (16) are displaced, the objects (O1 - O3) are successively irradiated by light, with intermediate periods without radiation. During the displacement of the pattern, the sequence of photocells (26) detects an energy reflection by the objects (O1 - O3). An output signal is generated at the rate of the pulse repetition rate and is processed in order to establish the object distance. <IMAGE>

Description

(54) OBJECT POSITION AND SURFACE DETERMINING METHODS AND APPARATUS (71) We, DYNELL ELECTRONICS COR- PORATION, a corporation organised under the laws of the State of New York, United States of America, of 75 Maxess Road, Melville, New York 11746, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates generally to object position and object surface determining methods and apparatus and more particularly to the use of radiant energy for determining distance to and other positional information concerning radiant energy-reflective objects.

In U.S. Patents Nos. 3,936,649 and 3,962,588 applicants herein disclosed methods for generating signals for use in determining positional coordinates of radiant energy-reflective objects and surfaces.

In a preferred practice, a reticle has a succession of contiguous cells, each separately discernible. Light sources are disposed on one side of the reticle in locations of known positional coordinates. A photograph made from an unknown location shows the reticle with the light sources disposed in those cells in respective line-of-sight relation from the unknown location to the light source and enables generation of a pair of signals, each having serial time extents in number corresponding to the number of cells along a distinct axis with indication in one of such time extents identifying the cell in such lineof-sight relation. The information in the signal pair may be employed in triangulation with the light source locations to identify the positional coordinates of the unknown location.For convenience in examin ing the photograph, particularly where the cell succession includes large numbers of cells enhancing resolution, the reticle is encoded by placing discernible elements in selected cells. In this practice, the signals generated from the photograph also include encoding information and one may look to a subsuccession, i.e., fewer than all cells in the succession, to identify the cells in such line-of-sight relation.

In another prior undertaking, set forth in U.S. Patent No. 3,866,052 and involving applicants herein, methods are disclosed wherein, in one practice, an object is illuminated from a common location through successive masks, each of different radiant energy transmissive character. Photographs are made and signals are generated indicating the number of photographs and those photographs inclusive of preselected object surface points, which may then be reconstructed therefrom.

Further prior undertakings of applicants in this field of endeavor are set forth in the specification of British Patent Application No. 35051/76 (Serial No. 1532304).

Prior art systems in which masked sources issue patterned light into space for direction finding are set forth in Johnson et al. U.S.

Patents Nos. 3,799,675 and 3,704,070. In these systems, an observer in the irradiated space may determine his angular orientation with respect to a light source by detecting the sequence (on-off) of received radiation, a fixedly-located source being shuttered on and off for projection through a succession of encoded masks. The latter of these patents notes a prior undertaking in which a single mask may be moved with respect to a fixedly-located source to light-encode the volume.

According to the invention there is provided a method for use in determining positional information of a radiant energyreflective object, comprising the steps of: (a) propagating a divergent radiant energy pattern having mutually different adjacent parts; (b) while maintaining said radiant energy pattern in identical configuration as propagated in step (a), effecting relative translation between the radiant energy pattern and both said object and a collection location and collecting radiant energy reflected by said object to said collection location; and (c) generating an output signal indicative of changes in such collected radiant energy as a function of time.

Another aspect of the invention provides a system for use in determining positional information of a radiant energy-reflective object, comprising: (a) pattern generator means for propagating a divergent radiant energy pattern having adjacent mutually different pattern parts and for maintaining said energy pat tern in identical configuration as propagated upon movement of the pattern generator means; (b) drive means for translating said pattern generator means with respect to said object; (c) collector means fixedly disposed with respect to said object for collecting radiant energy reflected thereto by said object and generating signals indicative of such energy reflected thereto; and (d) signal processing means for providing an output signal indicative of the time spacings between successive of such collector means generated signals.

A photocell array with plural successions of photocells may be arranged in viewing relation to the object along respective different axes to provide output signals in a manner further to indicate object position with respect to such different axes. The radiation pattern is preferably encoded whereby the last-mentioned additional positional information is more readily obtained.

The invention will be further described, by way of example. with reference to the accompanying drawings, wherein: Fig. 1 is a front elevational view of apparatus in accordance with the invention.

Fig. l(a) is a partial sectional view of the Fig. 1 apparatus as seen from plane I(a)-- I(a) of Fig. 1.

Fig. 2 is a schematic sectional view of the Fig. 1 apparatus as seen from plane Il-Il of Fig. 1.

Figs. 2(a) and 2(b) repeat the Fig. 2 schematic showing for unencoded masks having structure different from the unencoded mask of Figs. 1 and 2.

Fig. 3 is an isometric drawing depicting objects located in the field of view of the Fig. 1 photocell array unit.

Fig. 4 is an electrical schematic and block drawing of the photocell array unit of Fig.

1 in combination with processing circuitry in accordance with the invention.

Fig. 5 shows a code-generating circuit and a table explanatory of the code.

Fig. 6 is a front elevational view of a mask structure embodying the Fig. 5 code.

Fig. 6(a) is a schematic diagram explanatory of the Fig. 6(b) signal succession.

Fig. 6(b) shows a signal succession according with radiant energy reflected from an object irradiated through the upper half of the Fig. 6 mask.

Fig. 6(c) is a schematic diagram explanatory of the Fig. 6(d) signal succession.

Fig. 6(d) shows a signal succession according with radiant energy reflected from an object irradiated through the lower half of the Fig. 6 mask.

Fig. 6(e) shows a further signal succession resulting from use of the Fig. 6 mask.

Fig. 7 is a generaI block diagram of a system for processing signals generated in accordance with the invention.

Fig. 8 is a detailed block diagram of a preferred embodiment of the Fig. 7 system.

Fig. 9 is a timing diagram explanatory of operation of the Fig. 8 system embodiment.

Fig. 10 is a detailed block diagram of another system for processing signals generated in accordance with the invention.

Fig. 10(a) is a front elevational view of a further mask structure embodying the Fig.

5 code.

Fig. 11 is a timing diagram explanatory of operation of the Fig. 10 system embodiment.

Figs. 12(a)-12(c) illustrate an optics arrangement for use with photocells stacked along a single axis.

Fig. 13 is a front elevational view of a further encoded mask structure.

Fig. 13(a) is a schematic diagram explanatory of a signal succession obtainable with the mask structure of Fig. 13.

Referring to Figs. 1, 1(a) and 2, position determining apparatus 10 includes an overhanging support 12 adapted by its interior track 14 to receive a mask member 16 and to support the same for translation along translation axis T in Fig. 1. Drive discs 18 are selectively rotatable to so translate member 16 on energization of an electric motor and drive system (not shown). A light source 20, which may include a lamp 20a and lens arrangement, is supported by frame 22 and ribs 24a and 24b for joint translation with mask 16. Photocell array unit 26, having lens 26a and hood 26b, is fixedly supported by its base 28. Unit 26 includes photocells PC1-PCl4, arranged in an illustrative pattern shown in Fig. 1, i.e., in a succession of seven axially axially along and in a succession of two transversely of translation axis T. Mask 16 includes light-transmissive or translucent portions T1-T7 and other portions NT l-NT6, respectively separating portions T1--T7. Portions NT1--NT6 are preferably opaque (non-translucent) but may be otherwise of different light-transmis- sive character than portions T1--T7.

Considering Fig. 2, volume V has planes P1, P2 and P2 parallel to axis T. In one practice in accordance with the invention the format of mask 16 is such that the respective extents of portions T1--T7 and NT1-NT6 are selected to provide that first expanses P1-1, P1-3, P1-5, P1-7, P1-9, P1-11 and P,-13 of plane P1 are irradiated by light source 20 (confront portions T1-T7) while expanses Pl-2, Pl-4, P1-6, P1-8, P1-10 and Pl-12 are not then irradiated (confront portions NT1-NT6), and further such that the respective linewise extents of all of these expanses of plane P1 are all equal, i.e., the linewise extent of P1-1 equals that of P1-2, etc. This selective issuance of divergent radiation from light source 20 into volume V may be achieved by making the light transmissive and non (less)-transmissive extents of the mask portions respectively of equal linewise extent to affect such irradiation of plane P1 as shown in Figs. 1 and 2.

By this mask 16 format, expanses P2-1 (irradiated) and P2-2 (non-irradiated) of plane P2 are also of equal linewise extent as are expanses P3-1 (irradiated) and P3-2 (non-irradiated) of plane P2. With this practice, the invention defines selectively irradiated planes P1, P2 and P3 defining locations separated from reference location R, outwardly of translation axis T, by distances xl, x2 and x3 respectively. The time for the radiation pattern or common part thereof, to sweep by any location in plane P1 will be identical and is indicative of distance x.

Different sweep times will likewise apply for all locations in planes P2 and P2, indicative of distances x2 and x, respectively.

For purposes of explanation, Fig. 2 and the isometric showing of Fig. 3 depict locations of radiant energy-reflective objects Oi, O2 and 0,. With respect to reference location R, object Ol is outwardly thereof at a distance xl (is in plane P1), at an elevation therein above reference location R (aside axis T) at a distance zl and offset from location R along axis T at a distance y1. O3 is defined by distances x2, y2 and z and 03 by distances X3, y2 and z2 as against reference location R.

With mask 16 and light source 20 translated rightwardly from their illustrated solid line Fig. 2 position such that rib 24b is in its rightward phantom position aligned with location R, the entire pattern of radiation generated by the mask and light source can be made to pass by objects Oi, 03 and 03 by subsequent leftward translation of the mask and light source until rib 24b is in its leftward phantom position shown in Fig. 2.

In the course of such translation, object Ol is succesively irradiated by light issuing through mask portions T1-T7 with intervening periods of non-irradiation (or different irradiation) of object Oi as mask portions NT1NTG are disposed between the light source and object Oi. AccordingXy, photocell array unit 26, which is at a fixed location relative to object O, has a photocell thereof (PC7), in line-of-sight relation to object O, through lens 26a, periodicàlly excited.

The frequency or repetition rate of excitation of photocells in unit 26 is mathematic- ally related to x-distance from location R in accordance with the formula: (T) (V) A where V is a velocity of translation of the mask and light source, T is the mask pattern on/off time as sensed by the photocell unit and A is the pattern divergence. By divergence is meant the degree of nonparallelism as between light bundles issuing through light transmisive portions successive along the translation axis. In the example of Fig. 2, A equals: Pol/xl; (P2 x2, (P3-1)/X3; (P1-2)/x1; etc.

In the course of pattern translation, photocell array unit 26 sees objects O003 reflect energy, i.e., effectively blink, at repetition rates which differ proportionally in accordance with the x-distance of such points from location R. Thus, object 02, closer to location R, will blink at a higher rate than object 03, and in turn object Oj will blink at a higher rate than object 02.

Volume V may thus be considered to be comprised of locations all definable by planes parallel to translation axis T and objects at such planes will have distinct re flectance frequency characteristic, based on the format of the mask, whereby the invention lends itself readily to the use of correlation or counting techniques in defining distance alternatively to such mathe- matical formula set forth above. In such correlation practice, the volume may be calibrated by placing objects at known distances from location R and by storing facsimiles of signals reflected thereby to photocell array unit 26. Each such facsimile has a corresponding x-distance counterpart thereto and signals generated by photocell array unit 26 in the course of examining objects having unknown location may be cross-correlated with such facsimile signals until a suitable stored matching signal is found, thus providing x-distance indication for the object. In countng techniques, the number of pulses received in a given unit of time define unique distances, as discussed more fully below.

Turning now to Fig. 4, the rearward side of photocell array unit 26 is shown in com bination with circuit lines LPC1-LPC14 extending individually from the photocells.

All such lines are capacitively coupled, as indicated by capacitor C in line LPC8, to amplifiers, as shown by amplifier 32. The outputs of amplifiers 32 are selectively indicative of the photocell or photocell of array unit 26 which is excited by objectreflected radiant energy. For example, when output line 34 of the amplifier for line LPC7 (not shown) provides an output signal based on reflected energy from object l PC7 has been excited in which case the object is located along line S in Figs. 2 and 3.

The outputs of amplifier 32 as furnished on line 36 may be directly processed for x-distance (plane) information.

With line S determined and plane P1 determined as the x-distance plane containing object Oi, object Oi is thereby locatable in volume V by the intersection of a determined line and plane. With the position of the node of lens 26a, through which such line passes, known relative to reference location R, Object l is readily locatable with respect to such location R.

In the illustrative embodiment, line 36 applies its output in common to filters 38, 40 and 42. Such filters are bandpass filters having bandpass frequency limits indicated in Fig. 4 and facilitate segregation of returns to one photocell from multiple objects at different x-distance. Thus, if an object is between location R and plane P1, filter 38 will conduct the line 36 signal to line 44a.

Signals on lines 44a, 44b and 44c may be examined by the above-discussed correlation techniques for frequency content or may be processed as discussed hereinafter in connection with Figs. 7, 8 and 10. Since the capacitive coupling provided in line LPC8 blocks steady state signal content attributable to background lights background illumination is not of concern as long as saturation is avoided.

In preferred unencoded mask practice in accordance with the invention mask 16 is employed, i.e., a planar mask equally weighted to define a divergent radiant energy pattern which is linewise symmetric in planes parallel to the translation axis. Alternative unencoded mask structures are noted in Figs. 2(a) and 2(b).

In Fig. 2(a), unencoded mask 16' is circular in its extent, concentric with source 20a.

Adjacent light-transmisive and non-transmissive extents thereof (T'1 and NT1l) are of equal arcuate extent. Three different objects 04, 0, and Oo are shown in plane pull. When mask 16t is moved leftwardly from its Fig. 2(a) position, the response from the objects will vary uniquely. For object 6, the response will evidence an on-off-on pattern starting with a long period (tic) which decreases as the movement progresses.

For object 04, the response will show a shorter starting period (TA) which increases as the movement progresses. For object 05, assuming mask 161 to have further counterclockwise extent, its response will show a longer starting period (TB), than that of object 04, which will increase as the movement progresses. Similar reasoning will show that this is true for all planes parallel to plane pl, in the illuminated volume. Thus, it can be seen that each location in the illuminated volume will have a response pattern which may be readily recognized by the previously discussed correlation techniques.

If the entire irradiation pattern is moved by each of objects 04, 0, and O0 in manner covered above in Fig. 2, a special case results in which all objects provide responses with identical patterns delayed in time, such response pattern occurring sequentially as the objects are first illuminated in order Os, 04 and O,i. Thus, the position of all points on plane Plt can be determined from time of occurrence data. This is true of all points in all parallel planes, the response patterns from objects therein also being identical other than exhibiting compression or expansion in time in accordance with their outward distances from the reference plane P0 in Fig. 3 as compared with plane pull.

Considering Fig. 2(b), unencoded mask 1611, while circular has its adjacent lighttransmissive and non-transmissive Cf" 1 and NT1ll) portions of different arcuate extent such that a planar locus pull, defines object locations as to which pattern sweep time, or common part thereof, is the same. The examination of object responses derived in use of mask 1611 is as discussed for mask 16 in connection with Fig. 2.

Considering Fig. 5, circuit 50 thereof includes a shift register comprised of individual stages SR1-SR4 and connects the outputs of stages SR3 and SR4 to EXCLU SIVE OR gate 52, the output of which is applied to register stage SR1 through inverter (I) 54. Clock pulses CP are applied to register stage SRI to shift the shift register contents.Assuming the individual stages to have the contents indicated in the first line of the table of Fig. 5, i.e., register stages SR2 and SR4 to contain ones (ls) and register stages SR1 and SR3 to contain zeros (Os), circuit 50 will have further stage contents as indicated in the remaining table lines in the course of fifteen shift cycles provided by CP1-CP15. If stage SR1 is observed on a four-bit successive basis, its contents will follow the four-bit patterns illustrated leftwardly of the table in Fig. 5. Thus, at CP3, the shift register will contain the pattern 0000 which has decimal weight (DEC.WT.) of zero and this pattern will have shifted successively through SR1 at CP3. By way of further example, at CP8, the register will contain the pattern 1101, having decimal weight of thirteen (13) and this pattern will have passed through SR1 at CP8. In accordance with another aspect of the subject invention, sectors of the examined volume have assigned thereto unique decimal weight patterns of Fig. 5 in manner shown in Fig. 3 in conjunction with plane Pg. A mask is now constructed as shown in Fig. 6 to conform irradiation of volume V to this form of encoding.

Mask 56 of Fig. 6 has upper and lower sets of light transmissive portions T8--T19 and T20--T31, respectively. The upper half of the mask further includes light transmissive encoding portions TE1--TES and the lower mask half has light transmissive encoding portions TESTY9. For purposes of explanation, adjacent light transmissive portions will be considered to define a cell therebetween and, where an encoding portion is disposed between such adjacent portions, such cell will be considered to be "filled", cells without an encoding portion being considered as "empty". As in the case of the Fig. 1 mask, mask 56 provides equal extent planar expanses P,-l, P,-2, etc., each corresponding to a cell of the mask. In Fig.

6(a) empty cells are identified by a zero (0) and filled cells bv a one (1). A photocell receiving energy from an object in line-ofsight relation to light source 20 through portion T8 will yield the output signal shown in Fig. 6(b) as the Fig. 6 mask is translated leftwardly to a position wherein the light source is in line-of-sight relation to the object through portion T19. Desirably, the light source may be an extended filament arranged in parallel with the side edges of mask 56 or the other masks noted above.

Fig. 6(c) illustrates the filled and empty cell configuration for the lower half of mask 56 and Fig. 6(d) sehows the output signal of a photocell receiving energy from an object initially in line-of-sight relation to light source 20 through portion T20 and ultimately, on leftward mask translation, in lineof-sight relation to the light source through portion T3 1. Fig. 6(e) shows the output signal of a photocell receiving energy from an object initially in line-of-sight relation to light source 20 through portion T24 and, utimately, on leftward mask translation in line-of-sight relation to the light source through portion T31.

Taking Fig. 3 together with Figs. 5 and 6 the cell defined by portions T8 and T9 serves, during translation of mask 56 leftwardly from the Fig. 2 solid line position of the mask support elements, to issue radiation only in the zone identified as A in Fig. 3.

Likewise, the cell defined by portions T9 and T10 is the only cell which issues radiation solely in zones B and A of Fig. 3 during such mask translation. An irradiated object in zone A will give rise to photocell generation of the Fig. 6(b) signal, characterized uniquely by its initial four bit indication 0000. An irradiated object in zone B will produce the photocell initial four-bit output 0001. Such four-bit patterns will be seen to correlate with the first two successive codes shown in Fig. 5 leftwardly of the table.By this encoding of mask 56, an irradiated object in each of the zones A-N of Fig. 3 is uniquely recognizable by examining the initial four bits of a photocell output signal and, accordingly, one can readily differentiate the zone, of zones A-H, in which an object is situated without need, as discussed above in connection with Fig. 4, for determining such zone information by examining which photocell is energized in the illustrative orthogonally arranged photocell matrix of Fig. 1 or other photocell matrix of Fig. 1 or other photocell matrix.

Thus, a single photocell may be employed with a spherical lens focusing all energy reflected thereon from zones A-H. On the other hand, a photocell matrix is desirable for another purpose, namely, to facilitate examination of returns from plural objects not readily distinguishable by the Fig. 4 filtering measures. In this situation, photocells are employed in number such that each photocell sees a return from a separate object. This situation exists particularly in examining an object surface.

With object zone identification determined as above, the photocell output signals are now to be examined for their repetition rate contents to obtain distance information concerning the object returning the energy.

One embodiment of apparatus and system for this purpose is shown in block diagram in Fig. 7. Scan sensor 58, which may be a shaft encoder associated with the mechanism for translating mask 56, provides output indication on lines 60 and 62 respectively of the start and end of mask translation. Circuit 64 processes these signals, as discussed below, and applies output signals on lines 66 and 68 to scan return collectors 70a-70n, one such collector being provided for each photocell. The line 66 signal clears the collectors of their prior content and the line 68 signal identifies a preselected time for collector signal processing. Operation of collectors 70a-70n is further controlled by central processing unit 72 directly over collector selection lines 74, 76, 78 and 80 and further through readout (R/O) controller 82 which is connected to unit 72 by data transfer control lines 84, 86 and 88 and to collectors 70n70n by line 90. Collectors 70nr--70n furnish collected information to CPU 72 over lines 92, 94, 96, 98 and 100 (input data bus).

Unit 72 successively generates signals on collector selection lines 7X80 having ad dress content indicative of different ones of collectors 70a-70n. Where such address is that of collector 70cl collector 70a is operative on occurrence of the line 90 signal to furnish its collected information to unit 72 over lines 92-100. As will be discussed more fully below, line 92 provides an output signal when no return has been collected whereupon unit 72 can proceed directly to the next successive collector. Where returns haves been collected, input data bus lines 94--100 provide signals indicative of the time spacing between such returns. On receipt of such time-spacing information, unit 72 functions to compute object x-distance.

Referring to the more detailed block dia gram of Fig. 8, a typical photocell output signal is shown in the upper left-hand corner and will be observed to have inherent noise between object returns. An initial function of collector 70a is to discriminate between photocell output signals which have signal return content and photocell output signals which are constituted simply by noise. The output of photocell PC is applied over line 102 to amplifier 104 whose output is applied jointly to clocked delay 106 and peak detector 108. Peak detector 108 is cleared by a line 66 ON (first preselected voltage level) signal at scan start, prior to receiving the amplifier 104 output, and follows the amplitude of the amplifier output to provide indication on line 110 of the peak voltage level thereof.Divider 112 has its wiper set at approximately fifty percent of peak and applies the same to diode 114. Diode 116 is connected to a source of reference voltage V to establish a threshold level below which the processed signal is considered to be noise. Where the divider wiper voltage level exceeds the threshold voltage, line 118 is equal to the divider voltage level. Com- parator 120 includes input and hysteresis resistors 122 and 124, the former conducting the output of delay 106 to the comparator.

When the output voltage level of delay 106 exceeds the line 118 voltage level by an amount equal to hysteresis feedback voltage, as set by resistors 122 and 124, comparator 120 furnishes an ON signal to AND gate 126.

Delay 106, functioning as an analog shift register or extended delay line, effectively permits the output of amplifier 104 to be examined by peak detector 108 and the line 118 input to comparator 120 to be suitably set prior to receipt by the comparator by the amplified photocell output. During this circuit conditioning time period. AND gate 126 has one input thereof maintained OFF (second preselected voltage level) by line 68.

For this purpose, circuit 64 includes an OR gate 128 with inputs connected to lines 60 (start scan) and 62 (end scan) and its output connected through delay 130 to flipflop 132.

Flip-flop 132 is set and reset by successive pulses on line 134 and is directly reset by inverter 136 on the occurrence of the start scan signal on line 60, which also clears peak detector 108 through line 66, as above noted. Accordingly, line 68 is set OFF by resetting of flip-flop 132 by inverter 136 and, after expiration of delay 130, is set ON by initial setting of flip-flop 132. This line 68 condition persists until line 134 applies to flip-flop 132 the end of scan signal oceurring on line 62. Thus, line 68 is ON for a length of time equal to the scan period but delayed by the circuit conditioning time period.

These conditions are illustrated in the timing diagram in Fig. 9 which shows the start of scan signal in part (a), the end of scan signal in part (b), the scan period in part (C), and the scan period as delayed by delay 106 in part (d).

With the line 68 input to AND gate 126 now ON, the gate 126 output will be ON selectively in accordance with the peaks in the photocell output signal and flip-flop 138, as clocked by its CP input signal, will yield pulse trains on line 140 as illustratively indieated in parts (e)-(h) in Fig. 9. Considering part (e) of Fig. 9, this pulse train has the initial four-bit pattern 0000 corresponding with an object in sector A. The pulse train in part (f) in Fig. 9 is the initial four-bit pattern 1110 corresponding to an object in sector E of Fig. 3. The pulse train in part (g) of Fig. 9 exhibits the pattern 0100 corresponding to an object in sector N.In part (h) of Fig. 9 the pulse train indicates the pattern 0000, as in the case of the pulse train in part (ej however time-compressed and thereby indicating an object in sector A at closer x-distance to reference location R.

The pulse train on line 140 is applied to monostable multivibrator 142 which applies its output pulses to OR gate 144. On trailing edge excursions of the output of OR gate 144, counter 146 is cleared by input thereto from line 148 through monostable multivibrator 302. On leading edge the contents of the counter on lines 146eF146n are gated into memory 150 by the clocking signal on line 152. Counter 146 is incremented by clock pulses CP applied thereto on line 154 and continuously counts such clock pulses between successive clearings. Accordingly, the states of lines 146a-146n are indicative of the time-spacings between successive leading edge excursions of the output of OR gate 144. Writing in of information in memory 150 is enabled by line 156 when line 68 is ON.On each trailing edge excursion of the output of OR gate 14dun, line 158 increments address counter 160 to pro.

vide indication of different memory loca tion signals on lines 160Z160d. The address counter count direction is set to upcount as flip-flop 132 applies an ON signal thereto over lines 68, 156, 162 and 164. An OFF signal to line 164 causes the counter to down-count. Counter 160 is enabled for counting when line 166 is ON. OR gate 168 renders line 166 ON during scanning (line 162 ON) and during memory readout (line 170 ON). Line 170 is ON where all inputs to AND gate 172 are ON. For this purpose, each of the scan return collectors 70a-70n include unique decoder circuitry responsive to the states of lines 74--80. In the case of collector 70a of Fig. 8, such decoding circuitry includes an inverter 174 in series with line 80 with lines 74, 76 and 78 being applied directly to AND gate 172.

On completion of gating of signals into memory 150, unit 72 polls the collectors successively by the lines 74-80 signals through operation of readout controller 82.

Unit 72 generates an ON signal on line 88, thereby setting flip-flop 176, in response to which monostable multivibrator 178 drives line 90 momentarily ON through amplifier 180. With memory 150 being then provided also with an ON input on line 170a (data out enable), address counter 160 is decremented to access the storage locations of memory 150 and issue the stored information to unit 72 over lines 94100. On the trailing edge excursion on the output of monostable multivibrator 178, line 182 sets flip-flop 184 and line 86 goes ON, informing unit 72 of the expiration of the time setting of monostable multivibrator 178. This time is selected to permit the completion of the readout from one memory location of memory 150.Unit 72 examines the data bus lines and then drives line 84 ON to reset flip-flops 176 and 184 and commences a further readout by again rendering line 88 ON. Line 90 again goes ON and the contents of the next successive storage location in memory 150 are applied to lines 94--100.

This cycle continues until line 92 goes ON, informing unit 72 that counter 160 has fully counted down. As will be appreciated, in the event that no energy was reflected onto the photocell of collector 70cur by an object, counter 160 will not have undergone upcounting during the scan period. In this case, line 92 is ON at the outset of polling of collector 70a and unit 72 proceeds directly to polling of the next of the scan return collectors. Counter 160 is initialized by line 301 through line 60 at the beginning of the scan.

As noted above, the signals provided to unit 72 over lines 94-100 comprise the contents of counter 146 between resetting thereof, i.e., the number of clock pulses CP occurring between successive object return outputs of the photocell. With respect to the pulse train shown in part (e) of Fig. 9, unit 72 will be provided with counts clustering around two values, CP1 and CP2, indicative of the spacings respectively associated with empty and filled cells. By selecting the larger of these two measures (CP1), unit 72 effectively strips the encoding from the signals received, and, by averaging the various CPl measures, unit 72 provides the desired measure of x-distance.Considering part (h) of Fig. 9, showing a pulse train return from an object at less x-distance from the reference location, unit 72 will derive the measures CP3 and CP4 from the line 9S 100 signals. Unit 72 will select the larger of these measures as indicative of the xdistance. As will be observed in Fig. 9, CP3 is less than CP1 for such closer x-distance object In the practice last discussed, zone identification is made by observing the initial four bits of a signal with a computing unit performing the function of removing the coding information to provide x-distance information. In the embodiment shown in Fig. 10, signals are generated which are separately indicative of decoded x-distance information and zone identification.In this practice, mask 561 (Fig. 10(a)) is employed wherein the light transmissive encoding portions of mask 56 of Fig. 6 are omitted and the remaining light transmissive portions are retained with certain thereof being of different width from others as shown in Fig. 10(a). In mask 561, a cell is defined by adjacent light transmissive portions, e.g., T81-T91. A cell is considered to be "empty" if the leftward of the adjacent light transmissive portions defining the same is of width W1, as in the case of the cell defined by T81-T91. A cell is considered to be "filled" if the leftward of such transmissive portions is of larger width (W2), e.g., the cell defined by adjacent transmissive portions T121 and T131. As will be seen in Fig.

10(a), the first four cells starting from portion T81 are empty (0), the next three cells are filled (1), etc. The encoding pattern in mask 561 will be further seen to be identical with that of mask 56 insofar as its upper and lower encoded cell succession is identical therewith and defined by Figs. 6(a)-6(d).

Referring now to Figs. 10 and 11, photocell PC applies its output signal to line 186, Fig. 11 illustrating such signal having the encoded pattern 11001. This signal is amplified in amplifier 187 and applied to sample gate 188. Gate 188 is enabled to pass such input signal when line 189 is ON. This condition applies at the outset of each scan by reason of the fact that flip-flop 190 was reset by the reset signal on line 305 through invertor 191 at the end of the preceding decode cycle. With gate 188 open, the ampli fled photocell output signal is applied through signal mixing circuit 192 to clocked delay 193. Delay 193 is in cleared condition at this time since the start scan signal on line 60 is applied thereto by invertor 194.

As in the case above-discussed in connection with Fig. 8, fifty percent of the peak sensed by peak detector 195 (also then cleared by the start scan signal) is furnished by divider 196 and diodes 197 and 198 furnish a voltage level over line 199 to comparator 200. Comparator 200 includes hysteresis resistors 201 and 202 and renders line 203 ON as the delay 193 output exceeds the line 199 voltage level.

Invertor 194 sets flip-flop 204 at the start of each scan. With line 205 of ffip-flop 204 thus OFF, clock pulses from generator 206 are effective to decrement or increment a present counter (delay 207) whereby pulses are provided on line 208 spaced apart by the amount of time delay in delay 193, the first such pulse occurring, as shown in Fig. 11, after delay line and peak detector loading.

Invertor 209 inverts the line 208 signal whereby flip-flop 190 is set over line 210.

This disables sample gate 188, interrupting further entry of the photocell output in delay 193 which thereupon functions as a recirculating loop through line 211.

With flip-flop 190 set as noted above, line 221 to AND gate 222 is ON providing for passage of the output of comparator 200 to line 223. Line 223 triggers monostable multivibrator 224, the output signal of which is processed in phase-locked loop 225 as now discussed.

Loop 225 includes a control flip-flop 226, a voltage-controlled oscillator (VCO) 227, sample gate 228, integrator 229 and filter 230. During the course of delay and peak detector loading, output line 231 of flipflop 226 is maintained OFF by reason of the resetting of flip-flop 226 occurring at the end of the previous scan, such prior line 305 signal being applied to the flip-flop through invertors 191 and 232 and OR gate 233 and invertor 303. Flip-flop 226 is set through inverter 304 as monostable multivibrator 224 renders line 234 ON, with voltage-controlled oscillator 227 thereupon being frequency set to accord with the output pulse rate of monostable multivibrator 224, as sampled in gate 228. Such frequency setting of voltage-controlled oscillator 227 is indicated by its pulsed output signal on line 235.As delay 207 pulses line 208, flipflop 226 is reset through OR gate 233 and invertor 303. It is again set as the recirculating photocell output signal is again furnished by comparator 200 to line 223 whereby successive frequency settings of oscillator 227 occur as phase-locked loop 225 repeats its operation responsive to the recirculated information.

The line 235 signal, indicative of oscillator 227 setting, is squared in sparing circuit 236 and applied over line 237 as a clock for shift register 238. The output of AND gate 222 is clocked into shift register 238 on trailing edge excursions of the line 237 signal (Fig. 11), with ones and zeros being determined based on pulse widths of the line 223 signals. For the exemplary photocell output signal shown in Fig. 11, the input flip-flop of the shift register exhibits the illustrative states shown for line 239 indicating the code 11001. In accordance with the change of state of flip-flop 226, line 240 clocks the signals from shift register 238 into latch circuit 241 where they are available as a digital word on output lines 242.

For purposes of providing direct x-distance indication, the Fig. 10 system applies the output signals of monostable multivibrator 224 to AND gate 243 and enables gate 243 with the output of flip-flop 226. The bursts of pulses on line 234 during line 231 ON states are thus applied to frequency-tovoltage converter 244 and the voltage output thereof is stored by sample and hold circuit 245 and applied to a distance-calibrated voltmeter 246. The enable signal for sample and hold circuit 245 is generated by monostable multivibrator 306 which furnishes an output signal upon leading edge excursions of the output of AND gate 243.

The line 305 reset signal may be delayed at the option of the user of the Fig. 10 system to permit the multiple recirculations shown in Fig. 11. In this case, a readout device for words on line 242 may be observed over a settling period with the final of the repetitive readings serving as confirmation of prior readings.

The invention also contemplates simplified practice where an oscllloscope may be used to display the photocell output, directly furnished by amplifier 187, or, as processed to line 223. In the former case, the amplifier 187 output is seen, desirably on a memory scope, as triggered by the start scan signal on line 60. In the latter instance, the repetitive line 223 signal may be shown on a conventional oscilloscope as triggered by gate 233. The oscilloscope display will evidence the encoding, based on displayed different pulse width, and x-distance, based on time spacing of pulse leading edges.

It is to be understood that the system of Figs. 7, 8 and 10 may be employed also in processing returns from objects irradiated with an unencoded radiant energy pattern.

In that case, unit 72 of Figs. 7 and 8 averages all count measures it receives and need not perform the function of distinguishing lesser and greater count measures. In use of the Fig. 10 system for unencoded applications, one dispenses with the code-detecting circuitry thereof.

As mentioned above, photocell array unit 26 may be constructed as in Fig. 1 for purposes either of practicing the invention with an unencoded radiant energy pattern or, when using an encoded radiant energy pattern, for separating returns from different objects. As also noted above, the photocell array unit may comprise but a single photocell where the radiant energy pattern employed is encoded in both the y and z planes in Fig. 3. Fig. 12(a) shows an optical arrangement permitting the use of a still further arrangement of photocells. Photocell array unit 261 of Fig. 12(a) includes photocells in three rows 261a, 261b and 261c and in six columns 261d.In using the entire expanse of photocell array unit 261 object 0, is viewed solely through spherical lens 214 with object returns filling the full vertical and horizontal extents of the photocell array unit as shown by the solid line horizontal outline and the solid and broken line vertical outline. Such vertical outline may be compressed to be incident solely on photocell row 261b, as indicated by the full solid line object return showing, by use of a backwards cylindrical telescope arrangement comprising spherical lens 214 and cylindrical lenses 216 (double convex) and 218 (double concave). Fig. 12(b) is a plan view showing the unchanged horizontal object return-imaging and Fig. 12(c) is a side elevational view showing the vertical compression of the object returns.

Mask structure 220 of Fig. 13 may be employed in conjunction with the Fig. 12(a) optics arrangement. This mask structure provides a radiant energy pattern encoded horizontally, i.e., along the y-axis of Fig. 3.

While embodying the identical code shown in the upper half of mask 56 of Fig. 6, mask 220 achieves this code, not by the arrangement of empty or filled cells of uniform expanses, but by providing that adjacent transmissive portions define a 0 when spaced apart by distance Dl and define a 1 when spaced apart by distance D2, with Dl and D2 being different measures. For convenience, Fig. 6(a) is repeated in Fig. 13(a) below mask 220 to show such cell encoding. Where the mask is shift code encoded and where the total number of first (empty or short) and second (filled or long) cells, in the cell succession is P, each subsuccession of N cells embodies a distinct sequence of first and second cells, the relationship between P and N being established by the formula 2N--1=P.

Other encoding than shift code encoding may of course be employed, however, with expansion of the subsuccession required to be looked to for identification of a given cell. For example, the mask structure may be encoded such that the sequence of first and second cells in the cell succession is a pure binary progression.

Various changes and modifications evident to those skilled in the art may be introduced in the embodiments and practices discussed above. For example, the invention contemplates measures for translating the radiant energy pattern other than by the described translation of a combined light source and mask.

WHAT WE CLAIM IS:- 1. A method for use in determining positional information of a radiant energyreflective object, comprising the steps of: (a) propagating a divergent radiant energy pattern having mutually different adjacent parts; (b) while maintaining said radiant energy pattern in identical configuration as propagated in step (a), effecting relative translation between the radiant energy pattern and both said object and a collection location and collecting radiant energy reflected by said object to said collection location; and (c) generating an output signal indicative of changes in such collected radiant energy as a function of time.

2. The method claimed in claim 1 wherein said adjacent pattern parts contain respectively different intensities of radiant energy, said step (c) being practiced by generating said output signal as indicative of changes in the intensity of said collected radiant energy as a function of time.

3. The method claimed in claim 1 wherein said step (b) is practiced in part by translating said radiant energy pattern along a preselected axis.

4. The method claimed in claim 3 wherein the step (c) is practiced by so propagating said radiant energy pattern that said adjacent pattern parts contain respectively different intensities of radiant energy and are incident on adjacent equal linewise extents of a plane parallel to said preselected axis.

5. The method claimed in claim 4 wherein said step (c) is practiced by generating said output signal as indicative of the repetition rate of intensity change in said collected radiant energy.

6. The method claimed in claim 5 wherein said step (b) is practiced in part by defining plural energy collecting positions at said collection location disposed along a first axis constituted by said translation axis or an axis parallel thereto, said method including the further step of generating a further output signal indicative of the energy-collecting position on which objectreflected radiant energy is incident.

7. The method claimed in claim 5 wherein said step (b) is practiced in part

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (24)

**WARNING** start of CLMS field may overlap end of DESC **. As mentioned above, photocell array unit 26 may be constructed as in Fig. 1 for purposes either of practicing the invention with an unencoded radiant energy pattern or, when using an encoded radiant energy pattern, for separating returns from different objects. As also noted above, the photocell array unit may comprise but a single photocell where the radiant energy pattern employed is encoded in both the y and z planes in Fig. 3. Fig. 12(a) shows an optical arrangement permitting the use of a still further arrangement of photocells. Photocell array unit 261 of Fig. 12(a) includes photocells in three rows 261a, 261b and 261c and in six columns 261d.In using the entire expanse of photocell array unit 261 object 0, is viewed solely through spherical lens 214 with object returns filling the full vertical and horizontal extents of the photocell array unit as shown by the solid line horizontal outline and the solid and broken line vertical outline. Such vertical outline may be compressed to be incident solely on photocell row 261b, as indicated by the full solid line object return showing, by use of a backwards cylindrical telescope arrangement comprising spherical lens 214 and cylindrical lenses 216 (double convex) and 218 (double concave). Fig. 12(b) is a plan view showing the unchanged horizontal object return-imaging and Fig. 12(c) is a side elevational view showing the vertical compression of the object returns. Mask structure 220 of Fig. 13 may be employed in conjunction with the Fig. 12(a) optics arrangement. This mask structure provides a radiant energy pattern encoded horizontally, i.e., along the y-axis of Fig. 3. While embodying the identical code shown in the upper half of mask 56 of Fig. 6, mask 220 achieves this code, not by the arrangement of empty or filled cells of uniform expanses, but by providing that adjacent transmissive portions define a 0 when spaced apart by distance Dl and define a 1 when spaced apart by distance D2, with Dl and D2 being different measures. For convenience, Fig. 6(a) is repeated in Fig. 13(a) below mask 220 to show such cell encoding. Where the mask is shift code encoded and where the total number of first (empty or short) and second (filled or long) cells, in the cell succession is P, each subsuccession of N cells embodies a distinct sequence of first and second cells, the relationship between P and N being established by the formula 2N--1=P. Other encoding than shift code encoding may of course be employed, however, with expansion of the subsuccession required to be looked to for identification of a given cell. For example, the mask structure may be encoded such that the sequence of first and second cells in the cell succession is a pure binary progression. Various changes and modifications evident to those skilled in the art may be introduced in the embodiments and practices discussed above. For example, the invention contemplates measures for translating the radiant energy pattern other than by the described translation of a combined light source and mask. WHAT WE CLAIM IS:-

1. A method for use in determining positional information of a radiant energyreflective object, comprising the steps of: (a) propagating a divergent radiant energy pattern having mutually different adjacent parts; (b) while maintaining said radiant energy pattern in identical configuration as propagated in step (a), effecting relative translation between the radiant energy pattern and both said object and a collection location and collecting radiant energy reflected by said object to said collection location; and (c) generating an output signal indicative of changes in such collected radiant energy as a function of time.

2. The method claimed in claim 1 wherein said adjacent pattern parts contain respectively different intensities of radiant energy, said step (c) being practiced by generating said output signal as indicative of changes in the intensity of said collected radiant energy as a function of time.

3. The method claimed in claim 1 wherein said step (b) is practiced in part by translating said radiant energy pattern along a preselected axis.

4. The method claimed in claim 3 wherein the step (c) is practiced by so propagating said radiant energy pattern that said adjacent pattern parts contain respectively different intensities of radiant energy and are incident on adjacent equal linewise extents of a plane parallel to said preselected axis.

5. The method claimed in claim 4 wherein said step (c) is practiced by generating said output signal as indicative of the repetition rate of intensity change in said collected radiant energy.

6. The method claimed in claim 5 wherein said step (b) is practiced in part by defining plural energy collecting positions at said collection location disposed along a first axis constituted by said translation axis or an axis parallel thereto, said method including the further step of generating a further output signal indicative of the energy-collecting position on which objectreflected radiant energy is incident.

7. The method claimed in claim 5 wherein said step (b) is practiced in part

by defIning plural energy collecting posi tions at said collection location disposed along a first axis constituted by said translation axis or an axis parallel thereto and along a second axis transverse to said first axis, said method including the further step of generating a further output signal indicative of the energy-collecting position on which object-reflected radiant energy is incident.

8. The method claimed in claim 1 wherein said step (b) is practiced in part by defining plural radiant energy collecting positions at said collection location, said method including the further step of generating a further output signal indicative of the energy collecting position on which objectreflected radiant energy is incident

9. The method claimed in claim 8 wherein said energy collecting positions are arranged in a matrix along first and second axes and wherein said further output signal is generated as indicative of the relation to said first and second axes of said energy collecting position on which object-reflected radiant energy is incident.

10. The method claimed in claim 1 wherein said radiant energy pattern is encoded in the direction of such movement thereof in said step (b), said method including the further step of generating a further output signal indicative of encoding exhibited in such collected radiant energy.

11. The method claimed in claim 10 wherein said radiant energy pattern is additionally encoded in a direction transverse to such movement direction thereof.

12. A method for using a source of radiant energy to obbain information concerning the position of an object in a given volume with respect to a reference- location therein, comprising the steps of: (a) translating said source along an axis in said volume; (b) while so translating said source, selectively issuing radiation divergently therefrom into said volume such that a plane in said volume parallel to said axis is ir- radiated over first expanses thereof mutually spaced from one another by second expanses irradiated differently from said first expanses and such that said first and second expanses are each of equal linewise extent; (c) while maintaining said reference locations fixedly disposed with respect to said object collecting at said reference location radiant energy reflected thereto by said object; and (d) generating an output signal indicative of the repetition rate of such collected radiant energy.

13. The method claimed in claim 12 wherein said radiant energy is light energy and wherein said step (b) is practiced by disposing a masking member between said object and said source and translating said masking member jointly with said source.

14. The method claimed in claim 12 wherein said step (c) is practiced in manner providing for detection of a position at said reference location of incidence of said col lected radiant energy axially along and transversely of said~ axis, said method including the additional step of generating a further signal indicative of such incidence position.

15. A system for use in determining positional information of a radiant energy-reflective object, comprising: (a) pattern generator means for propagating a divergent radiant energy pattern having adjacent mutually different pattern parts and for maintaining said energy pattern in identical configuration as propagated upon movement of the pattern generator means; (b) drive means for translating said pattern generator means with respect to said object; (c) collector means fixedly disposed with respect to said object for collecting radiant energy reflected thereto by said object and generating signals indicative of such energy reflected thereto; and (d) signal processing means for provides ing an output signal indicative of the time spacings between successive of such collector means generated signals.

16. The system claimed in claim 15 wherein said pattern generator means comprises a source of radiant energy and radiant energy masking means supported for joint movement therewith.

17. The system claimed in claim 15 or 16 wherein said pattern generator means propagates said divergent radiant energy pattern encoded in the direction of movement thereof by said drive means.

18. The system claimed in claim 15, 16 or 17, wherein said pattern generator means propagates said divergent radiant energy pattern encoded in a direction transverse to the direction of movement thereof by said drive means.

19. The system claimed in claim 15, 16, 17 or 18, wherein said signal processing means provides a further output signal indicative of the encoding content of said collector means generated signals.

20. The system claimed in claim 15, 16, 17, 18 or 19, wherein said collector means comprises radiant energy-sensitive means generating an electrical signal indicative of change in radiant energy incident thereon and lens means for applying such object-reflected radiant energy thereto.

21. The system claimed in claim 20 wherein said radiant energy-sensitive means comprises a plurality of sensors arranged along the direction in which said drive means moves said pattern generator means.

22. The system claimed in claim 20 or 21, wherein said radiant energy-sensitive means comprises a plurality of sensors arranged transversely of the direction in which said drive means moves said pattern generator means.

23. A method of determining positioinal information substantially as herein described with reference to the accompanying drawings.

24. A system for use in determining the position of a radiant energy reflective object constructed and arranged to operate sub- stantially as herein described with reference to and as illustrated in the accompanying drawings.