CA2082659C

CA2082659C - Method and apparatus for detecting objects

Info

Publication number: CA2082659C
Application number: CA002082659A
Authority: CA
Inventors: Scott Juds; Paul Mathews
Original assignee: AUTO-SENSE Ltd
Current assignee: AUTO-SENSE Ltd
Priority date: 1990-04-10
Filing date: 1991-04-10
Publication date: 1999-03-09
Anticipated expiration: 2011-04-10
Also published as: EP0523185A1; EP0523185A4; WO1991015872A1; EP0523185B1; CA2082659A1; DE69125156D1; DE69125156T2; US5354983A; US5311012A; US5418359A

Abstract

A method and apparatus are disclosed which allow for the detection of an object (14) by the generation of a radiated beam (18) and a subsequent reflection by the object (14) of a portion (20) thereof. The detection of particulate object material (16) due to a reflection of a portion (22) of the generated beam (18) is minimized.

Description

vo 91/15872 PCT/US91/024S6 -1- 2082~'9 ~TUOD AND APPARATUS FOR ~ NG OBJECTS

~9C~rROUND OF T~ rNVFNTION
.

l. Field of the Invention Thi6 invention relate6 to a method and apparatus for the detecting of object6, and more particularly to a method and apparatus which detects objects and provides a detecting signal in response thereto, while minimizing the generation of such a detection signal in response to various objects which may proximately reside near the detector apparatus.

2. DiQ~nQQion Object detection systems are used in a wide variety of applications, including that associated with collision avoidance. In collision avoidance systems, these object detector6 are usually mounted upon the body of a moving vehicle and are made to generate a beam of radiation 6uch that the generated beam i6 caused to strike a clo6e object and be reflected back to the object detector. The receipt of thi~
reflected beam of generated radiation then usually cause6 the object detector to produce an amplified 6ignal to the operator of the vehicle warning the operator that an object i6 close by.
These object detectors have usually defined a modifiable threshold detection di6tance which defined the di6tance an object had to be from the detector in order to be detected.
This threshold distance was modifiable up to an upper limit defined by the constraints associated with the elements of the detector.

While these object detector systems have proven to be invaluable in the operation of motorized vehicles, there have been a substantial number of drawbacks as60ciated therewith.
Perhapfi the largest drawback a660ciated with the6e object W O 91/15872 P ~ /US91/02456 detector6, as used within collision avoidance sy6tem6, is that the6e object detector6 have been 6een to i66ue many false warnings to the operators of these motor vehicles causing undue alarm and improperly interfering with the operator's attention, thereby increa6ing the po66ibility of accidents due to abrupt 6tops or diverted attention. These fal6e detecting 6ignal6 have u6ually been the re6ult of the reflection of the generated beam by 6uspended particulate6 (i.e., snow, fog, rain, or other forms .~. .. . ..."., ., . ~
of atmo6pheric precipitation) which usually lies in close proximity to the object detector between the object detector and the object to be detected, and which causes a reflection of a generated beam back to the detector and cau6ing a false indication of the closeness of the object thereto.

A clo6ely related drawback as60ciated with the object detector6 as u6ed in colli6ion avoidance 6y6tem6 i6 that t the ability to detect a clo6ely po6itioned object i6 highly determinative of the amount of radiation which i6 reflected back to the object detector. That i6, it ha6 been found that these object detector6 have had a great deal of difficulty in detecting very dark object6, 6ince the~e dark object6 absorb much of the radiated energy which i6 generated from the object detectors and which cau6e6 only a very small amount of thi6 energy to be reflected back thereto. Thi6 drawback ha6 been overcome, in many in6tance6, by the u6e of increased amplification or gain (i.e. referred to a6 "Exce66 Gain") by the detector. Thi6 Exce66 Gain increases the amplitude of the signal produced by the detector in response to the received reflected beam of radiation.

While thi6 Exce66 Gain ha6 increased the ability of the object detector to detect very dark object6, it ha6 further amplified the problem associated with the generation of fal~e detection signals by the particulate material which i8 pre6ent in close proximity to the object. That i6, thi6 Exce66 Gain decrea6e6 the thre6hold amount of 6en6itivity needed by the '~O 91/15872 P ~ /US91/02456 _3_ 20826~9 detector in order for the detector to generate a detection 6ignal, thereby increa6ing the probability of a false detection signal. The pre6ent invention is then directed to overcome sub6tantially all of the deficiencie6 a6 6tated above.

SUMMARY OF TUF lNV~ ON

In accordance with one a6pect of the pre6ent invention, an object detector i6 provided for detecting the presence of an object, having a defined thre6hold detector di6tance a660ciated therewith, the object reflecting a beam of radiation therefrom and being remotely located a di6tsnce from the object detector, the object detector having a detecting apparatu6 for receiving the beam of radiation of the object and for generating a detecting 6ignal in re6pon6e thereto and further having an 6uppre~6ing apparatu~, which i6 coupled the detecting apparatu6 for 6uppre6sing the detecting 6ignal if the object i6 located within a predetenmined di6tance, being le66 than 6aid defined thre6hold detection di6tance, from the object detector.

In a 6econd aspect of the present invention, a method i6 provided for detecting the pre6ence of an object, the object reflecting a beam of radiation therefrom and being remotely located a di6tance from the object detector, the method compri6ing the 6tep6 of: acquiring the beam of radiation of the object; defining a thre6hold detection di6tance of 6aid object detector; detenmining the di6tance of the object from the object detector; and generating a detection 6ignal in response to the acquired beam of radiation only if the determined di6tance i6 greater than a predetermined di6tance value, 6aid predetermined di6tance being le66 than 6aid defined thre6hold detection di6tance.

The6e and other a6pect6, feature6, advantages and object6 of thi6 invention will be more readily under6tood by 2 ~ 8 2 6 5 9 reviewing carefully the following detailed de6cription in conjunction with the accompanying drawing6 and 6ubjoined claim6.

RRIF.F DESCRIPTION OF T~. DRA~I~Ç~

For a more complete under6tanding of the pre6ent invention relative to the advantage6 thereof, reference may be made to the following detailed de6cription taken in conjunction with the accompanying drawing6, in which:

Figure l i6 a plan view of a motor vehicle which i6 equipped with an object detector made in ~accordance with the teachings of the preferred embodiment of tbi6 invention and used in a colli6ion avoidance configuration;
. . .

Figure 2 i6 a diagrammatic ~iew of the len6e6, radiation generator, and radiation detector used by the object detector generally 6hown in Figure l;

Figure 3 i6 a block diagram of the object detector shown in Figure l;

~ Figure 4 i6 a graphical illu6tration of the relation6hip of the Exce66 Gain and the range a660ciated with an object detector of the prior art;

Figure 5 i6 a tiagrammatic illu6tration of the reflection6 produced by variou6 object6 placed within the path of the emitted ratiation from the object detector of the preferred embodiment of thi6 invention;

Figure 6 i6 a diagrammatic illu6tration of the lv~ ~rt of an acquired image acro66 the detector portion of the object 6hown in Figure l;

'VO 91/15872 P ~ /US91/02456 Figure 7 is a graphical illustration of the sen6itivity as60ciated with the detecting portion of the object detector shown in Figure l;
r Figure 8 is a graphical illustration of the mathematical convolution of the ~en6itivity graph shown in Figure 7 and of the inten6ity of the reflected radiation received by the object detector shown in Figure l;

Figure 9 i6 a graphical illu6tration of the relation6hip of the Exce66 Gain and the range a660ciated with the object detector shown in Figure l;

Figure 10 i~ a fir6t alternative embodiment of the detector portion of the object detector 6hown in Figure l;

Figure 11 i6 a 6econd alternative embodiment of the detector portion of the object detector shown in Figure l;

Figure 12 i6 a top view of the detector6 6hown in Figure 2;

Figure 13 is a third alternative embotiment of the detector portion of the object detector shown inn Figure l;

Figure 14 i6 a graphical illu6tration of the 6ensitivity a660ciated with the detector portion generally 6hown in Figure 13;

Figure 15 i6 a graphical illustration of the mathematical convolution of the 6ensitivity 6hown in Figure 14 with the inten6ity of the reflected radiation received by the object detector 6hown in Figure l;

Figure 16 is a graphical illu6tration of relationship of the Exce6s Gain and the range associated with 2 0 82 65 9 -6- ..
the object detector shown in Figure 1 and having a 6ensitivity as shown in Figure 14;

Figure 17 is an illustration of one shape of the emitted radiation beam from the detector shown in Figure l;

Figure 18a is a perspective view of one form of the mounting elements for the generation portion of the object detector of the preferred embodiment of this invention;

Figure 18b is a cross-sectional view of the mounting element shown generally in Figure 18a, shown mounted within a printed circuit board;
;"
Figure 18c is a perspective view of a 6econd form of the mounting element shown generally in Figure 18a;

Figure 18d is a cro6s-sectional view of the mounting element shown generally in Figure 18c and depicted as mounted in a printed circuit board;

Figure 18e is a plan view of the mounting element shown generally in Figure 18a; and Figure 18f is a plan view of the mounting element 6hown generally in Figure 18c.

nFTATTFn n~ TpTIoN OF T~ pRF.FP~RFn FMRnl)TM~NTS

Referring now to Figure 1, there i6 6hown an object detector 10 made in accordance with the teachings of the preferred embodiment of thi6 invention and mounted upon a motor vehicle 12 such that the object detector 10 may detect a relatively clo6e object, such as automobile 14, and inform the operator (not shown) of the motor vehicle 12 of the relatively clo6e location thereof. This detection is accomplished in order VO 91/15872 PCI/US91/02A~6 7_ 2082659 to reduce the probability of a collision between motor vehicle 12 and the object 14. Also 6hown in Figure 1 i6 a plurality of particulate objects 16 which are typically interpo6ed between the object to be identified 14 and the object detector 10. This particulate object material 16 may compri6e 6now, fog, rain, mi6t or various other form6 of known atmo6pheric particulate material.

Specifically, in orter for the object detector 10 to detect the occurrence of automobile 14 and to inform the operator of the vehicle 12 of it6 position, object detector 10 is made to generate one (or alternatively a plurality of) radiation beam6 18 and to direct these beams to the object 14 to be detected. Object 14 then reflect6 a portion 20 of each of the beam 18 back to the object detector 10. The object detector 10, upon receiving the beam portion 20 of the generated beams 18, then provides a detecting signal to the operator of the vehicle 12 advi6ing thi6 operator of the relatively clo~e location of the motor vehicle 14. The generation of 6uch a detecting 6ignal i6 dependent upon the relative received intensity of the reflected beam portion 20, and the reflected beam portion i6 compri6ed of reflection6 from various portions of the object 14.

If the motor vehicle 14 is within a relatively close distance from vehicle 12, then the reflected portion 20 of the beam 18 is relatively high in inten6ity, even if the motor vehicle 14 i6 of a relatively dark color. That is, 6hould the reflected beam portion 20 be relatively high in intensity, then the object detector 10 will produce a detecting 6ignal to the operator of the vehicle 12 indicating to this operator that the object 14 is relatively close thereto. However, if the reflected beam portion 20 is of a relatively low inten6ity, then the object detector 10 will not inform the operator of the vehicle 12 of the location of the vehicle 14 6ince the vehicle 14 i6 relatively far away from the vehicle 12.

2082fi59 -8- ~
Thi6 generation of beam 18 and the 6ubsequent reflection of beam portion 20 has been found to work satisfactorily in many instance6 when used for the detection of objects 14 for collision avoidance purpo6es. However, it has been found that this interposed particulate object material 16 al60 reflect6 a certain portion 22 of the generated beam 18 as well. This reflected beam portion 22 may be at a relatively high inten6ity since the particulate object material 16 is relatively close to the object detector 10 which is relatively highly reflective. Since the overall gain of the object detector 10 is u6ually increased in order to detect dark-colored objects, the reflections from objects 16 is made even more effective in causing the generation of the detection signal.
, ~ -This reflective beam ~portion 22 may then be at a high enough intensity upon receipt by the object detector 10 to cause the object detector 10 to generate a detecting 6ignal to the operator of the vehicle 12, informing this operator of the relatively close location of an object to be avoided. This false detection by the plurality of particulate objects 16 which are interposed between the object detector 10 and the vehicle or object to be detected 14 could create a false detecting 6ignal by object detector 10. For thi6 reason, the object detector 10 made in accordance with the te~ch;ng6 of the preferred embodiment of thi6 invention will ignore or negate the beam portion6 22 which are reflected by the plurality of particulate object6 16 a6 shown in Figure 1. This ignoring or negation of the reflected beam portion 22 then provides for a more reliable and error-free generation of detecting 6ignal6 from the object detector 10 to the operator of vehicle 12.

Referring now to Figure 3, there i6 6hown the object detector 10 made in accordance with the teachings of the preferred embodiment of thi6 invention and con~;ning an emitter apparatus 24, a detector apparatus 26, a thresholding apparatus 28, an annunciator apparatus 30 and a controller 32.

VO 91/15872 PCI'/US91/02456 _9_ 2082659 Specificslly, the emitter apparatus 24 and the detector apparatus 26 are coupled to the controller 32 by bu6 34 while the detector apparatus i6 further coupled to the thresholding apparatu6 by bu6 36. The controller 32 i6 coupled to the thresholding apparatus 28 by bu6 38, while the controller is further coupled to the enunciator apparatu6 30 by bu6 40.

In operation, the emitter apparatu6 24 emit6 or generates the beam 18 a6 6hown in ~igure 1. The detector apparatus then receive6 the beam portion6 20 or 22 and provide6 a detecting signal output upon bu6 36 to the thresholding apparatu6 28. Thi6 6ignal on bu6 36 which is generated by the detector apparatus 26 is substsntially associated with the sensitivity of the detector apparatus 26 and ha6 a certain value which is closely associated therewith. l'hat is, the received beam portions 20 or 22 i6 only detected if the detector sensitivity is such that the portions 20 or 22 are received by the detector apparatus 26. The use of the sensitivity of detector 26 will be discussed later.

The thre6holding apparatus 28 then determine6 the relative value of the signal on bus 36 and compares it against a predete_ ~ned thre6hold value. If thi6 value a660ciated with a signal on bus 36 i6 greater than or equal to this thre6hold value, then the thresholding apparatus emit6 an acknowledgement signal upon bus 38 to the controller 32 ~rhich i6 indicative of the relatively clo6e location of an object 6uch a6 automobile 14 in Figure 1. In thi6 manner, the detection 6ignal on bus 36 may be suppressed or blocked in a manner to be discu66ed later.
Upon receiving the signal on bus 38, the controller 32 then i66ues a signal onto bus 40 which is directed to the annunciator apparatus 30. This signal on bus 40 then provides for a visual, audio, or other sort of indication to the operator of the motorized vehicle 12 that an object has been detected by the detector 10. The controller 32 is further coupled to the ~ ~ ~ 2 6 5 9 ~
.~

emitter apparatus and the detector apparatus 26 by bus 34 in order to allow control thereof.

Referring now to Figure 2, there is shown the emitter apparatus 24 and the detector apparatus 26. Specifically, the emitter apparatus 24 contains in one embodiment a light-emitting diode 42 and a lens 44. In the preferred embodiment of this invention, the light-emitting diode 42 emits a beam 18 of infrared radiation through lens 44. The light-emitting diode 42 may be powered by bus 34 and is under the control of controller 32 through bus 34. The detector apparatus 26 contains in one embodiment, photosensors 46 and 48. A beam portion 20a is received or acquired by lens 50 and is directed to a single one of the photosensors 46 whereby an image of the reflected object is impressed thereon. A second beam portion 20b reflected from another area of the object 14 or from one of the objects 16 are also received by lens 50 and are impressed upon the photosensor 48.

Further, it can be seen that the lenses 44 and 50 are separated by a distance 52 and that the photosensors 46 and 48 define a distance 54 which is the largest longitudinal distance associated with any two points, one point being on photosensor 46 and the other point being on photosensor 48.
Further, distance 56 defines the shortest distance from each of the photosensors 46 and 48 to the midpoint of the lens 50. Distances 58 and 60 define distances associated with the object 14 to be detected by the object detector 10. That is, photodetector 46 produces a signal onto bus 36 having a first polarity upon receipt of an image defined by beam portions 20.
Additionally, the photodetector 48 produces a signal onto bus 36 having a different polarity from that of the signal produced by photodetector 46 when the photodetector 48 receives an image signal through beam portions 20. If the object 14 is placed at a distance 60 or greater away from the lens 50, then the signal on bus 36 produced by the photosensor 48 is at a higher level __ A

'~0 91/15872 P ~ /US91/02456 than that of the signal produced by the photo6en60r 46. Should an object 6uch as 14 re6ide between the di6tance6 58 and 60, then both of the photosensor6 46 and 48 will produce a corre6ponting 6ignal having oppo6ite polarity upon the bu6 36 to the thresholding apparatus 28.

In order to fully under6tand the principle6 of thi6 invention, reference i8 now made to Figure 4 which 6how6 graph6 70 and 72 which relates the Exce66 Gain of the photo6en60r6 46 and 48 to a range of di6tance6 as60ciated with the placement of an object 14 to be detected according to the principle6 of the prior art. Generally, when the separation between the len6es 44 and 50, defined as di6tance 52, is negligible, then the Exce66 Gain a660ciated with an object within the di6tance defined by 74 is as 6hown in portion 75 of the a660ciated graph 70, 6ince the beam 18 and the detector field of view a660ciated with len~ 50 begin to inter6ect one another almo6t immediately and the Exce66 Gain increa6es dramatically. When the di6tance 52 i6 larger, as fihown in graph 72, it take 60me di6tance from the len6 defined a6 58 before the beam 18 and the detector field of view a6sociated with the len6 50 overlap, 60 that an object may be detected. That i6, an object mu6t both be illuminated by the beam 18 and in the field of view as60ciated with len6 50 in order to be detected. Therefore, the Exce66 Gain in graph 72 is zero for the di6tance range 70. However, as 600n as the beam 18 and the field of view overlap, the Exce66 Gain curve ri6e6 rapidly and i6 denoted by that portion of graph 72 marked 76.

The portion6 78 and 80 of curves 70 and 72 refipectively demonstrate the fact that the 6ensitivity of the detector6 46 and 48 d; ni6he6 relative to the inver6e 6quare of the di6tance between the object 14 and the len6 50. If, however, both of the photo6en60r6 46 and 48 produce a 6ignal in re6pon6e to the projected image thereon which is of opposite polarity, then portion 82 of curve 72 re6ult6 and demon6trate6 that at relatively long ranges (i.e., those beyond di6tance 60) 20826~9 -12- ~
there i6 no detection of the object by the photodetector6 46 and 48 becau6e the 6ignal received by the detector 46 i6 larger than that received by the detector 48 as 6hown in Figure 2. That i6, more of the reflection6 of the beam 18 will occur upon detector 46 than on detector 48 when the object i6 moved beyond di6tance 60. The6e Exce66 Gain characteri6tic curve6 therefore allow6 one to 6culpture the Exce6s Gain re6pon6e to eliminate the fal6e detection produced by the plurality of particulate object6 16 and i6 u6ed in the object detector 10 of the preferred embodiment of the pre6ent invention.

To further 6ee how the object detector 10 of the preferred embodiment utilize6 thi6 6culpturing of the Exce66 Gain curve6 70 and 72 to eliminate unwanted detection6 occurring by the plurality of particulate or other related object6 16, reference i6 now made to Figure 5 which show6 the relative deployment of len6e6 44 and 50 and the emitter apparatu6 24.
Specifically, at variou6 di6tance6 from the len6 50 (or altern~tively from len6 44), an object produce6 a reflected portion 20 of the beam 18 to the lens 50. The len6 50 then direct6 the received image beam portion 20 and direct6 thi6 beam portion to a 6pecific spatial location which i6 dependent upon the di6tance that the object i6 away from either len6 44 or len6 50. That i6, an object'6 di6tance away from len6 50 (or alternatively len6 44) i6 uniquely a660ciated with the placement of the received image by len6 50. Thi6 i6 clearly 6hown in Figure 5 where object di6tance6 92, 94, 96, 98 and 100, each defining a unique di6tance away from len6 44 (or alternatively len~ 50) cau6e the creation by len6 50 of re6pective image6 102, 104, 106, 108 and 110, each having a unique 6patial placement a660ciated therewith. It 6hould be noted that object di6tance 100 define6 the farthe6t di6tance that the object detector 10 may detect an object 14 within. Thi6 thre6hold di6tance may be increa6ed (to a limiting detection di6tance) or decrea6ed by u6e of the detector6 44 and 50 by known technique6. Detector6 44 and 50 impo6e 60me upper limit on the thre6hold detection ~0 91/15872 P ~ /US91/02456 _ -13-di6tance. Thi6 unique 6patial placement a660ciated witQ t~e6 S 9 di6tance away from either lens 44 or lens 50 of an object is u6ed by the object detector made in accordance with the teachings of the preferred embodiment of thi6 invention in order to dimini6h the false detection a660ciated with the plurality of ~ particulate object6 16 and to 6culpture the Exce6s Gain characteristic of the object detector of the preferred embodiment of thi6 invention.

To 6ee the relation6hip between the unique placement of the image6 a660ciated with an object (6uch a6 automobile 14) by len6 50 and the Exce66 Gain curve6 70 and 72, reference i6 now made to Figure 6 which 6how6 photo6en60r~ 46 and 48 and received image6 120, 122, 124, 126 and 128. Specifically, the further an object moves away from len6 44, the clo6er it6 corre6ponding image come6 to photo6en60r 46. That i6, image 120, in Figure 6, i6 a660ciated with an object which i6 relatively far way from the len6 44 and has a di6tance corre6ponding to portion 82 of graph 72. Image 128, however, i6 a6sociated with an object which i6 relatively clo6e to len6 44 and ha6 a range a660ciated therewith which correspond~ to portion6 76 of graph 72. Image6 122-126 are all a660ciated w~th object6 varying between the di6tance6 defined by image6 128 and 122. The greater the area covered by an image 120-128 upon an individual photo~en60r 46 or 48, the larger i6 the re6ultant produced 6ignal therefrom. Given the known inver6e 6quare relation6hip between the di6tance a660ciated with an object, the degradation of the Exce66 Gain 6ignal6 a6 6hown by graph6 70 and 72 and the ~ t of an object'6 image acro66 detector6 46 and 48 due to the pl~c- t of that object from len6 44, one may alter or control the 6en6itive area which i6 hit or excited by the image 6pot a6 a function of the di6tance away from the corre6ponding object. Thi6 not only allow6 one to define a thre6hold detection di6tance (i.e. a furthe6t di6tance that the object detector 10 may detect an object within but al60 allows W O 91/15872 PCT/US9l/02456 2 0 8 2 6 5 ~ 14-- one to 6culpture the Exces6 Gain as60ciated with the detector apparatu6 60 as to decrea6e the probability of fal6e detection signals being generated.

Specifically, the Exce66 Gain of a photoelectric 6ensor (such as 46 or 48) can be computed by a convolution integral of the following form and i6 u6ually defined to be a measure of the ratio of the available 6ignal (from the detector6 48 and 46) to a threshold value for a reference target a6 a function of di6tance:

GX(R) = -2 ¦ S(y)I(y,R~dy R

where: K = RmaX2 J I(y~ Rmax)dY
~ _ and where:
Rmax = maximum distance range that allow6 the 6en60r 48 to detect a goa white diffu6e reflecting target with all the receive light from the beam 18 impinging upon detector 48.
S(y) = 6en6itivity function of the combination of photo6en60r6 46 or 48 I(y,R) = inten6ity function of the image 6pot for a target at a fixed range di6tance R
In order to calculate the function I(y,R), we fir6t need to find a function for I(y,Rmax). A66uming that the target or the object 6uch a6 14 i6 alway6 in the far field of the len6 50, that i6, the di6tance between the object to be detected and the lens 50 is greater than ten focal length6, then the 6hape dependency within I(y,~ ax) i6 eliminated. Also, given that lense6 44 and 50 are 6ub6tantially identical, then the image diameter will be 6ub6tantially the 6ame a6 the 60urce diameter.
As6uming that a light-emitting diode 42 is mounted in a VO 91/15872 P ~ /US91/024'' ~~ -15- 20826~
reflecting dish and u6ed as a source of radiation and this reflecting dish has a diameter of "d," then the intensity function I(y,Rmax) is approximated by the following:

d/2 I(y) e cos (~Y) , O elsewhere -d/2 Now assuming that RmaX e 1000~ and d e .09O~ we can calculate that K c 106. Since all of the light associated I(y) is capturable, then the integral from negative infinity to positive infinity of I(y)dy is approximately equal to 1. Additionally, we know that distance 54 - (dist~nce 56)(dis~nce 52) R ~ _ Therefore, I(y,R) ~ cos ~y/d - (dis~nce 56)(tist~nce 52) from the limits defined by:
d x (dist~nce 56)(tistance 52) + t/2 ~/R
d x (dist~nce 56)(distance 52) - d/2 and 0 elsewhere ~/R
To further understand the teaching6 of this invention, we next need to determine the sensitivity associated with photodetector6 46 and 48. Referring now to Figure 7, there is shown a graph 130 showing the relative response of the various detectors 46 and 48 relative to the spatial distance acro~s the detector combination. As can be seen, detector 48 produces a signal having a positive polarity, ~n one embodiment of thi6 invention, when detector 48 receives an image from len6 50, while detector 46 produces a signal having a substantially negative polarity when receiving the same image from lens 50.
Both the signals from detectors 46 and 48 appear upon bus 36 to the thresholding apparatus 28. Additionally, as shown in graph - 16 ~ 9 130, there may be additional detectors such as detector 132 which may be used in conjunction with the system. The use of such additional detectors is described herein later. lt has been found that the strategic placement of the detectors 46 and 48 in the manner shown has allowed for the sculpturing of the associated Excess Gain characteristics such that the unwanted detection of objects 16 is substantially eliminated.

Referring now to Figure 8, there is shown a graph 140 comprising the graphical convolution of the sensitivity of the detector combination 46 and 48 as shown in Figure 7 and the previously calculated intensity function denoted as I(y,R). Graph 140 illustrates the relative sensitivity of the detector apparatus 46 and 48 relative to the distance scanned across the individual detectors. Graph portion 142, shown in phantom, denotes the convolution graph if a single large detector, instead of two detector generating signals of opposite polarity, is used. As can be seen, the relative sensitivity of the detector apparatus 26 is decreased for a certain range of distances 143 in close proximity to the object detector 10. This decrease allows for the suppression of the detection signal from the detector apparatus 26.

Referring now to Figure 9, there is shown Excess Gain graphs 150 and 152 which relate the Excess Gain of the detector apparatus 26 to a distance that a detected object (such as automobile 14) is away from the object detector 10 wherein the detector apparatus 26 has a sensitivity substantially similar to that shown in Figure 7.

Graph 152 is obtained by multiplying graph 140 (excluding portion 142) by the previously calculated intensity function of the image which was denoted as I(y,R). Graph 150 is a result of this operation upon the graph 140 having portion 142 and denoting a single large detector. It should be evident of ordinary skill in the art that graph 152 provides a decreased vo gl/15872 P ~ /US91iO2456 ~ -17- 2082~9 Exce6s Gain at a relatively close range 154 relative to object detector 10 and al60 provides an increased Exce66 Gain at a range 156 thereafter. Both range6 154 and 156 are within the detection range 157. The u6e of a 6ingle large detector doe6 not allow for this sculpturing or decrea6e in Exce66 Gain at relatively close range6 to object detector 10 and an increase of gain thereafter within the detection range defined a6 157.

Thi6 decrea6e in Exce6s Gain~ a660ciated with the range 154 increases the reliability of the detection signal produced by the object detector 10. This is due to the fact that the plurality of particulate object6 16 i6 relatively closely placed to the object detector and produce6 a reflected beam portion 22 therefrom. By decrea6ing the Exce66 Gain in thi6 6mall range, one may prevent the6e object6 16 from cau6ing detector 10 to produce a detecting 6ignal. At the same time, however, an object that is desired to be detected within the range defined by range 154 will be detected 6ince it i6 more highly reflective than i6 the individual particular object material 16 and therefore even under reduced Exce6s Gain conditions will be detected by the object detector 10. The use of a single detector, such as taught by the prior art having a single detection signal of a given polarity, provides no 6culpturing, in thi6 manner, and produce6 little safeguard6 again6t fal6e detection cau6ed by the plurality of particulate object6 16.

Referring now Figure 10, an alternative embodiment of the detector apparatus 26 i6 6hown. Specifically, a single large detector 160 may be utilized while 6till having the sculptured arrangement as 6hown in Figure 9. Specifically, a variable optical den6ity filter 162 i6 placed upon the image-receiving surface 164 of the detector 160. Thi6 variable optical den6ity filter 162 block6 60me of the reflected light beam portion6 22 ~i.e. tho6e from the plurality of particulate object6 16). Thi6 u6e of the filter 162 reduce6 the 6en6itivity W O 91/1~872 PCT/US91/02456 2 082 65 ~ -18- 11.~.
of the photodetector 160 to the object 16, thereby producing a reduced Excess Gain to certain portions of the reflected light.
That is, the 6en6itivity of the detector 160 is substantially reduced relative to the plurality of particulate objects 16 which reside in a relatively close range to the photodetector 160 while providing only a 61ight reduction in the overall sensitivity to rather largely reflective objects located at a greater di6tance therefrom. Thi6 cau6e6 the 6culpturing of the a660ciated Exce66 Gain.

Referring now to Figure 11, a third embodiment of the sculptured detector apparatu6 26 u~ed by the object detector 10 i6 shown as containing a single photodetector 170 upon which a mask 172 i6 placed upon the image-receiving portion 174. This mask may be of a variety of geometric 6hapes, but it6 purpo6e is to reduce the area associated with surface 174 in a location 176 corresponding to the acqui6ition or the reception of an image which corre6pond6 to an object which i6 relatively clo6e to the object detector 10. The placement of this ma6k in location 176 then reduce6 the 6en6itivity of the detector 170 to the6e relatively close object6. The ma6k 172 further allow6 a relatively large area of the photodetector 170 to be expo6ed to an acquired image at a location 6uch a6 178 which corre6pond6 to the acqui6ition or reception of an image a660ciated with an object which i6 relatively far from the object detector 10.
Thi6 would allow for a degradation and a 1088 of 6en6itivity of the photodetector 170 to objects within thi6 range. The use of ma8k 172 then allows for the sculpturing of the Excess Gain curve in a range 6uch a6 154 a6cociated with Figure 9.

Referring now to Figure 12, there is shown a top view embodiment of the detector apparatus 26 of the preferred embodiment of this invention and corresponding substantially to that shown in Figure 2. Specifically, detector6 46 and 48 are used in combination thereof to acquire an image from len6 50 and each providing signals of opposite polarity in response thereto ~'0 91/15872 PCI/US9l/02456 onto bus 36 as hereinbefore described. The detectors 46 and 48 may be mounted upon a printed circuit board, such as 179, which would allow the detectors 46 and 48 to be relatively easily incorporated within the detector 10.

Referring now to Figure 13, there i6 shown a third embodiment of the detector apparatus 26 of the object detector 10 made in accordance with the te~ch;ng~ of the preferred embodiment of thi6 invention and conts;n;ng photodetector6 180, 182 and 184 which are separately spaced upon a surface 186.
Photodetector6 180 and 182 sub6tantially corre6pond to the detector6 46 and 48 respectively a6 shown in Figure6 2 and 12.
Detector 184 6ub6tantially corre6ponds to detector 48 since detector 184 produce6 a signal onto bu6 36 having 6ub6tantially the 6ame plurality a6 that signal produced by the photodetector 48. The advantage in u6ing the detector apparatu6 26 configuration shown in Figure 13 is that increa6ed sen6itivity of the detector 26 may be achieved for objects which are farther away from object detector 10 than wa6 po66ible with the configuration6 shown in Figure6 10, 11 and 12. Thi6 i6 due to the placement of the additional photodetector 184 at a 6patial location which allow6 the detector 184 to receive image radiation from len6 50 corre6pond;ng to object6 which are relatively far from len6 50. Therefore, an Excess Gain sculpturing i6 achieved with a relatively long thre6hold detecting di6tance. The sensitivity of the configuration of the detector apparatu6 26, a6 shown in Figure 13, i6 graphically shown in graph 190 of Figure 14 and, as can be seen therefrom, produces a signal of relatively positive polarity at two different range6 acros6 the detector apparatus 26. The strategic placement of the detector 180, 182 and 184 a8 6hown in graph 190 ha6 been seen to achieve tbe needed Exces6 Gain 6culpturing.

Referring now to Figure 14, there is shown graph 200 which is the convolution of the 6en6itivity graph 190 with the 2082659 previou61y calculated inten6ity function of the target object which wa6 denoted a6 I(y,R). As can be seen from graph 200, a relatively larger distance 202 acro66 the detector apparatu6 26 produces a detected object than was po66ible with the sensitivity function a6 6hown in graph 140 of Figure 8, thereby increasing the thre6hold detecting di6tance of thi6 embodiment.

The u6e of the detector apparatus 26 a6 6hown in Figure 13 then produce6 an Exce66 Gain graph 210 a6 6hown in Figure 16 having a decrea6ed Exce66 Gain at a range 214 corresponding to relatively clo6e di6tance6 to object detector 10 while having an increa6ed gain range thereafter and defining a relatively larger threshold detection range than did the Exce66 Gain graph 152 or 150 a6 6hown in Figure 9. Therefore, the u6e of the photodetector 184 in conjunction with photodetector6 180 and 182, a6 6hown in Figure 13, allow6 for the 6culpturing of the Exce66 Gain a660ciated with detector apparatu6 26 but al60 allow6 for object6 to be detected by the detecting apparatu6 26 which are relatively far in di6tance therefrom.

A6 further 6een in Figure 13, the detecting apparatu6 26 may compri6e a plurality of individual detection portion6 220, 222 and 224 which are uniquely a660ciated with a 6eparate beam 18 which i6 generated from the emitter apparatu6 24. That i6, the emitter apparatu6 24 may include a plurality of 6eparate light-emitting diode6 (6uch a6 light-emitting diode 42 of Figure 2) each producing a 6eparate beam 18 of radiation therefrom. Each of the detector portion6 220, 222 and 224 may be configured 60 a6 to receive the portion6 20 or 22 of the 6eparately generated radiator beam 18. In thi6 manner, the detector apparatu6 26 may be configured ~o a6 to be efficiently packaged into a plurality of 6eparate detector portion6 220-224.

Referring now to Figure 17, there i6 6hown a beam 6haping technique re6ident within the invention. Specifically, vo 91/15872 P ~ /US9l/02456 -21- 20~2659 detector apparatus 26 i6 shown as containing the previously di6cus6ed photodetectors 46 and 48. As previou61y explained, each of the photodetectors 46 and 48 produces a signal onto bu6 36 having opposite polarity, when a portion of the reflected radiation 20 or 22 is impinged thereon. By uniquely configuration the shape of the radiated beam 18, it ha~ been found that one may decrea6e the 6en6itivity of the overall detector apparatus 26. This decrea6e in 6en6itivity in certain ranges i6 achieved by choo6ing a flattened or dimpled geometric 6hape 230 in6tead of a 6ub6tantially round 6hape 232. The u6e of 6uch a dimpled 6hape 230 alleviate6 8 "non-uniform target"
problem. Thi6 "non-uniform target" problem i6 due to the object detector 10 -king fal6e detectionc of object6 if the object image fall6 on the detector 46, and it corre6pond6 to an area of relatively low reflectance, while the image appearing upon detector 48 fall6 in an area of relatively high reflectance.
That is, the image upon detector 46 may be due to a highly reflective 6ide marker while the image upon detector 48 may be due to a dark object. By flattening or dimpling the 6hape of the beam 20 a6 6hown by the geometric 6hape 230, thi6 problem i6 alleviated by reducing the depth of the region beyond the uniform target cut-off where a portion of the 6pot 230 is 6till imaged on the additive detector 48. That i6, the differential between the reflectance of the low and high reflectance area6 as60ciated with that portion of the beam 20 appearing on photodetector6 46 and 48 respectively mu6t be relatively large in order for a fal6e detection to occur due to the u6e of thi6 dimpled shape 230. This dimpled 6hape 230 then allow6 for a greater reflectance differential between area6 upon an object to be detected 6ince the beam 20 would have to be more clo6ely placed upon photodetector 48 in order for a detecting 6ignal to be generated. In effect, dimpling or reducing the overall height or diameter of the beam 20 makes the object detector sy6tem 10 more highly convergent.

Reference is now made to Figure6 18a-18d which depict the details of two versions 234, 234a of a mounting apparatus associated with the mounting of the light-emitting diode 42 within the emitter apparatus 24. A first version of the mounting element i6 depicted in Figures 18a, 18b, and 18e a~
simply denoted by the numeral 234. The mounting element 234 includes a cylindrical 6kirt 238 which i6 adapted to be tightly received within an aperture in a printed circuit board 226. A
tapered portion 240 facilitates rapid centering and automatic insertion into the printed circuit board. A ~mall chamber 248 between the 6kirt 238 and 6houlder portion 247 engage6 the top of the printed circuit board and a66ist6 in ensuring proper centering and thus the mounting position of the mounting element 234. The upper portion of the mounting element 234 includes a central cavity 235 therein which i6 es6entially 6ymmetrical in one direction and altered to a central axi6 237. Thus, cavity 235 is defined by a curved end wall6 239 and a pair of generally straight walls 241. End walls 239 include a cut-out or 6calloped portion 242 therebetween and a pair of 6paced-apart, essentially flat 6urfaces 250 having flat flange portions 236.
A light-emitting diode 6uch a~ 42, herein denotet a6 244, is mounted a6 by adhe6ive6 on a flat bottom 6urface within a cavity 235 in a central po6ition coA~;~l with longitudinal axi6 237. A
fine electrical wire 246 i6 connected to the light-emitting diode 244 and extend6 upwardly and laterally through the cut-out portion 242 60 as to be bondable to a printed circuit path on a printed circuit board 226.

As best 6een in Figure 18e, the geometry of the cavity 235 and related features 6een in plan view are symmetrical about the axis 237. Thus, the light-emitting diode 244 produces a beam of infrared light energy which is essentially 6ymmetric about the axi6 237.

The alternative mounting arrangement 234a 6hown in Figures 18c, 18d and 18f is essentially similar to that shown in ~vo 91/15872 P ~ /US91/02456 ,~.

Figure6 18a, 18b and 18e with the following exceptions. The inclination of the end wall6 239 relative to the longitudinal axi6 237 are different from each other, with one wall being inclined at an angle "y" and the other wall being inclined at a 6ub6tantially greater angle "z," where "y" i6 les6 than the angle of "x" 6hown in Figure 18b, and the angle of "z" i6 greater than the angle of "x." A6 a re6ult of thi6 latter-mentioned configuration, the beam 20 produced by the light-emitting diode 244 effectively emerge6 at an angle, here 15~ relative to the longitudinal axi6 137. Due to the geometry of the mounting element6 234, 234a ant particularly the configuration of the end wall6 239 and the flat 6ide6 241, the resultant image applied to the photore6pon6ive 6en60r6 produce6 beam6 20 which cam be directed toward the-center of additional optic6 6uch a6 relay len6e6 (not 6hown). Additionally, the curved end wall6 239 and generally 6traight 6ide wall6 241 of the mounting arrangement6 234 and 234a provide for a dimpled beam 20, thereby reducing the "non-uniform target" problem as hereinbefore de6cribed. Thi6 produced beam 20 will have a general 6hape 230 a6 6hown in Figure 17. The flat flange portion6 of flat ~urface 250 al60 facilitate rotational indexing of an otherwi6e circular part, provide flat surface6 for handling by manual and automatic tool6 6uch a6 tweezer6 and robot gripper6, and cau6e the formation of "6callop6" which allow for the w e of a shorter, relatively les6 expen6ive and more rugged bond wire from the hybrid circuit 6ub6trate upon printed circuit board 226 to the light-emitting diode 244.

It i6 to be understood that the invention i6 not limited to the exact con6truction or method illu6trated and de6cribed above, but that variou6 change6 and modification6 may be made without departing from the 6pirit and 6cope of the invention a6 defined in the following claim6.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGED IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An object detector (10) for modifying the amount of reflected beam acquired by the detecting apparatus to detect objects (14) located within a range of distances from the detector beyond a predetermined distance, comprising emitter apparatus (24, 44) for generating a focused beam of infrared light energy (18), detecting apparatus (26,50) having a field of view that includes said beam (18), for receiving the reflection (20) of the beam (18) from an object (14) located within said range of distances and generating an output signal in response thereto, suppressing apparatus (164, 172, 184) included in the detecting apparatus (26, 50) for variably suppressing the output signal in response to the reception of an acquired beam (20) reflected from an object (10) located closer than the threshold distance, the amount of said suppression increasing as the distance of the detected object (14) from the detecting apparatus (26, 50) decreases, and thresholding apparatus (28) for receiving the output signal and generating a detection signal when the output signal exceeds a predetermined threshold value.

2. The object detector (10) of claim 1, wherein the detecting apparatus (26, 50) includes a photodetector (26) and a lens (50) optically coupled to the photodetector (26) .

3. The object detector (10) of claim 1, wherein the suppressing apparatus (164, 172, 184) comprises a filter (164) placed upon the photodetector (160) to filter the light received by the photodetector (160).

4. The object detector (10) of claim 3, wherein the suppressing apparatus (164, 172, 184) comprises a variable density optical filter (164) for variably blocking a portion of reflection of the beam of radiation (20) received by the photodetector (160) as a function of the distance of the detected object from the detector (160) decreases.

5. The object detector (10) of claim 1, wherein the suppressing apparatus (164, 172, 184) comprises a mask (172) variably covering the photodetector (170) for variably blocking portion of the reflection of the beam of radiation (20) received by the photodetector (170) as a function of the distance of the detected object (14) from the detector decreases.

6. The object detector (10) of claim 1, wherein the detecting apparatus (26, 50) comprises a first photosensor (180) for producing a first signal of a first polarity upon receiving a reflected beam, and a spaced second photosensor (182) for producing a second signal of a second polarity upon receiving a reflected beam, and the suppressing apparatus (164, 172, 184) comprises a third spaced photosensor (184) for producing a third signal of the second polarity upon receiving a reflected beam wherein the output signal comprises the sum of the first, second and third signals.

7. The object detector (10) of any one of claims 1, 2, 3, 4, 5 or 6, wherein the emitter apparatus (24, 44) comprises a light emitting diode (42).

8. The object detector (10) of claim 7, wherein the emitter apparatus (24, 44) further includes a second lens (44) optically coupled to the light emitting diode (42).