Source: http://www.google.com/patents/US4970384?ie=ISO-8859-1
Timestamp: 2014-12-18 05:49:30
Document Index: 531004211

Matched Legal Cases: ['art 47', 'art 48', 'art 47', 'art 47', 'art 47', 'art 50', 'art 51', 'art 50', 'art 50', 'art 50', 'art 50', 'art 50', 'Application No. 47757']

Patent US4970384 - Optical sensor for detecting distance to an object including anamorphic ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsAn optical sensor discriminating the presence of an object or detecting distance to an object which includes a light projecting element for projecting light to a detection area, a light receiving element for receiving light reflected from an object present in the detection area and an anamorphic light...http://www.google.com/patents/US4970384?utm_source=gb-gplus-sharePatent US4970384 - Optical sensor for detecting distance to an object including anamorphic light receiving lensAdvanced Patent SearchPublication numberUS4970384 APublication typeGrantApplication numberUS 07/391,246Publication dateNov 13, 1990Filing dateAug 9, 1989Priority dateFeb 6, 1987Fee statusLapsedAlso published asDE3803529A1, DE3803529C2, US4876446Publication number07391246, 391246, US 4970384 A, US 4970384A, US-A-4970384, US4970384 A, US4970384AInventorsYoshiaki Kambe, Yoshihiko Okuda, Atsuyuki Hirono, Akira Nagaoka, Takayasu ItoOriginal AssigneeMatsushita Electric Works, Ltd.Export CitationBiBTeX, EndNote, RefManPatent Citations (7), Referenced by (15), Classifications (12), Legal Events (5) External Links: USPTO, USPTO Assignment, EspacenetOptical sensor for detecting distance to an object including anamorphic light receiving lensUS 4970384 AAbstract An optical sensor discriminating the presence of an object or detecting distance to an object which includes a light projecting element for projecting light to a detection area, a light receiving element for receiving light reflected from an object present in the detection area and an anamorphic light receiving lens for expanding a condensed light spot received on the light receiving element in a direction perpendicular to a direction of movement of the light spot on the light receiving element. The light receiving element outputs a detection signal which discriminates the presence of the object in the detection area. The light receiving element can be rectangular in shape and comprise two or more triangular shaped photodiodes which output detection signals that can be processed to determine a distance between the object and the light receiving element. A movable prism can also be provided to compensate for movement of the object other than towards or away from the light receiving element to avoid erroneous distance measurement which might otherwise occur.
2. An optical sensor according to claim 1, wherein said position detecting means receives said condensed light spot of said light receiving lens means and provides a pair of position signals IA and IB, the at least three photodiodes being disposed such that at least two of the photodiodes are positioned on opposite sides of at least another one of the photodiodes which is positioned therebetween, said signal IA being obtained from said at least two photodiodes, and said signal IB being obtained from said at least another one of the photodiodes.
9. An optical sensor utilizing triangulation, the sensor comprising means for projecting light to a detection area, means for receiving light reflected from an object present in said detection area, sensor function setting means capable of energizing said light projecting means, and means for processing output signals from said light receiving means to provide an object detection signal; said light receiving means including an anamorphic light receiving lens which condenses said reflected light upon said light receiving means mostly in a moving direction of a condensed light spot on the light receiving means upon variation in a distance of the object from the sensor so as to have said condensed light spot expanded in a direction perpendicular to said moving direction, and a position detecting means comprising a plurality of light receiving elements respectively extending in said moving direction of the condensed light spot as adjoined to one another in said expanded direction of the light spot and within the extent of the expanded light spot respectively with an adjoining line lying diagonally with respect to the moving direction of the light spot from one end to another end of the light receiving means in the moving direction of the light spot; wherein said light receiving elements of said position detecting means comprise at least three photodiodes arranged to dispose at least two of said photodiodes on opposite sides of at least a third one of the photodiodes positioned therebetween, the photodiodes providing a pair of position signals IA and IB to provide said output signals of the light receiving means as a signal ratio IA /IB, said signal IA being obtained from said at least two photodiodes and said signal IB being obtained from said at least a third one of the photodiodes.
10. An optical sensor according to claim 9, wherein said at least three photodiodes comprise five photodiodes, three of which comprise a first group of photodiodes and two of which comprise a second group of photodiodes, said first group of the photodiodes outputting said position signal IA and said second group of the photodiodes outputting said position signal IB, the condensed light spot formed by said anamorphic lens being simultaneously received on said first and second groups of photodiodes, each of said first group of photodiodes having a wicth in said transverse direction which increases from one end to an opposite end of said position detecting means in said longitudinal direction and each of said second group of photodiodes having a width in said transverse direction which decreases from said one end to said opposite end of said position detecting means.
11. An optical sensor according to claim 9, wherein said at least three photodiodes comprise seven photodiodes, four of which comprise a first group of photodiodes and three of which comprise a second group of photodiodes, said first group of the photodiodes outputting said position signal IA and said second group of the photodiodes outputting said position signal IB, said condensed light spot formed by said anamorphic lens being simultaneously received on said first and second groups of photodiodes, each of said first group of photodiodes having a width in said transverse direction which increases from one end to an opposite end of said position detecting means in said longitudinal direction and each of said second group of photodiodes having a width in said transverse direction which decreases from said one end to said opposite end of said position detecting means.
In the optical wiring board 12 as in the above, a light Po emitted from the light emitting element 15 is provided as an input to the optical wave guide 28 through the input mirror portion 35 as seen in FIG. 4, and the light P0 is divided at a predetermined ratio to the respective optical wave guides 29-32 to propagate therethrough, as shown in FIG. 3. First branch light P1 in the wave guide 29 is directed to a light input surface 46 of the operation indicating member 43 of a light diffusion block type at the end portion of the guide 29, the light thus reaching the member 43 being caused to be scattered in all radial directions so that it can be visually determined that the optical sensor 10 is in an operating state. Second branch light P2 is directed to the output mode setting member 44 disposed at the end portion of the optical wave guide 30. This output mode setting member 44 comprises a shiftable flat plate part 47 and an operating part 48 secured onto the flat part 47, and this flat plate part 47 is formed so as to be non-reflective only at a part of a surface of the plate part 47 facing the end portion of the wave guide 30 while the rest of the surface of the plate part is formed so as to be reflective, so that the reflection factor at the output mode setting member 44 can be varied by having the member 44 slid to displace the non-reflective surface part with respect to the opposing end portion of the wave guide 30, whereby the branch light P2 is modified in response to the amount of displacement of the output mode setting member 44. An optical wave guide 33 is provided with one end thereof opposed to the setting member 44 so as to be jointly disposed with the branch wave guide 30 in the thickness direction of the wiring board 12 and the other end thereof extends away therefrom, as seen best in FIG. 1, to a sideward direction so as to terminate at a mirror portion 36. Accordingly a modulated light P2 ' responsive to the set position of the setting member 44 is directed through the wave guide 33, the modified light being reflected at the mirror portion 36 and received by the light receiving element 19 opposing the other end of the wave guide 33, as seen best in FIG. 6.
Third branch light P3 is directed through the optical wave guide 31 to an optical input part of the sensitivity setting member 45 disposed at an end portion of the optical wave guide 31. This member 45 comprises a sensitivity setting knob 52 provided with a disk part 50 perforated to have many small holes 49 of a predetermined distribution of varying density as seen in FIG. 8 and with an operating part 51, and a reflection plate 53 opposed to the end portion of the wave guide 31 with the disk part 50 interposed there between. The small holes 49 in the disk part 50 are distributed in the present instance to gradually increase or decrease in the circumferntial direction, so that the reflection factor of the reflection plate 53 with respect to the third branch light P3 which has passed through the small holes 49 of the disk part 50 will be varied depending on the amount of rotation or angular position of the sensitivity setting knob 52. An optical wave guide 34 is provided with one end thereof opposed to the member 45 so as to be jointly disposed with the branch wave guide 31 passing the third branch light P3 in the thickness direction of the wiring board 12 and the other end thereof extends away therefrom also in the sideward direction to terminate at a mirror portion 37. Accordingly a modulated light P3 ' responsive to the angular position of the sensitivity setting member 45 will propagate through the optical wave guide 34 to be reflected at the mirror portion 37 and be received by the light receiving element 18 opposing the other end of the wave guide 34, as seen in FIG. 5.
Fourth branch light P4 propagates through the optical wave guide 32 to be reflected by the mirror portion 38 at an end portion thereof and be received by the light receiving element 20 opposing this wave guide 32.
Instead of such provision of the output mode setting member 44 as in the above, it may be possible to provide an output mode setting member 44a which is provided with a stepped portion as shown in FIGS. 9 and 10, so that the member 44a will have different distances d1 and d2 to the end portion of the wave guide 30 depending on the displaced position of the member 44a, the distance d1 being relatively larger as seen in FIG. 9 to render the modulation level to be lower while the distance d2 being relatively smaller as in FIG. 10 to elevate the modulation level. The disk part 50 of the sensitivity setting member 45 may have a shape other than a true circle such as a non-circular configuration that will form an involute curve so that opposing area between the disk part 50 and the end portion of the wave guide 31 or 34 will be varied as the setting member 45 is rotated, whereby the sensitivity variation can be realized without perforating the disk part.
In the optical sensor 10 of the foregoing arrangement, further, it should be readily appreciated that the object in the detecting area can be detected in accordance with the received light output of the light receiving element 17, the detection can be modified in the mode by properly processing at a signal processor the output signal of the light receiving element 19 which receives light through the optical wave guide 33 for the modulated light P2 ', mirror portion 36 and hole 26, and a proper sensitivity setting voltage can be generated through a comparison of the output from the light receiving element 18 which receives light through the wave guide 34 for the modulated light P3 ', mirror portion 37 and hole 25 with the output of the light receiving element 20 which receives light through the wave guide 32 for the branch light P4, mirror portion 38 and hole 27.
In this arrangement, light is projected from the light projecting means 700, and a reflected light back from an object OJ1, OJ2 or OJ3 in a detection area at a distance R1, R2 or R3 from the projecting means 700 is condensed as it passes through the anamorphic light receiving lens 742 to form a condensed light spot S1, S2, or S3 on the position detecting means 721, on which each condensed spot takes a position correpsonding to the distance of the object as seen in FIG. 30, and the position detecting means 721 provides an output current in which the ratio IA /IB of outputs of both photodiodes 721a and 721b varies depending on the position of the condensed light spot. That is, the distance of the object can be obtained on the basis of the ratio IA /IB of the output current. Here, the condensed light spots S1-S3 are respectively expanded to be linear in the direction perpendicular to the moving direction M of the spot responsive to the distance of the object, as seen in FIG. 31, whereby the distribution of the intensity of illumination by the linear condensed light spot on the detecting means 721 is made substantially always constant even when the object OJ moves to traverse the detection area in a direction vertical to the plane of FIG. 30 or, in particular, when the object is present at a position which deviates from the optical axis of the light from the light projecting means 700 vertically with respect to the plane of the drawing, as will be seen in FIGS. 32(a) to 32(c), as well as in FIGS. 33(a) to 33(c). In other words, the detection of the object traversing the optical axis in a vertical direction with respect to the plane of the drawing results in variation in the intensity of illumination LU such as in curves of FIG. 33 but in such constant illumination distribution, so that the ratio IA /IB of detected position signals IA and IB provided by the photodiodes 721a and 721b will not vary and accurate position and distance signals can be always obtained.
It is also advantageous to employ position detecting means 821, 821a and 821b such as shown in FIGS. 34 to 36, in which the means comprise three or more of the photodiodes adjoined. When, for example, the position detecting means 821 comprises three photodiodes as in FIG. 34 and the condensed light spot S is provided closer to a longitudianl end of the means 821 as in FIG. 37, the distribution of illumination LU of the linear condensed light spot is made by the anamorphic lens to be substantially constant over the entire detecting means 821 but is unable to be made completely constant. Provided that the object OJ in the detection area moves to traverse the optical axis in the vertical direction with respect to the plane of the drawings, the level of illumination LU will be as shown in FIGS. 38(a) to 38(c) in which, in particular, the state shown in FIG. 38(a) shows that the output of the left side end photodiode rises to be higher so as not to be able to obtain accurate IA /IB information. In this case, as shown in FIGS. 34 to 36 in which a plurality of sharply angled triangular photodiodes are interengaged with each other in the longitudinal direction of the means 821, 821a and 821b, i.e., in the moving direction M of the condensed light spot, because the photodiodes in each means are so arranged that one output signal IA is obtained from a group of photodiodes including ones which are disposed on both widthwise sides while the other output signal IB is obtained from the other photodiode or the other group of photodiodes disposed inwardly there of, it is made possible that the distance signal IA /IB of an object which moves in the direction transverse to the optical axis in the detection area becomes larger than a value accurately corresponding to an actual distance R. That is, the output of the position detecting means 821 is discriminated at a signal processing means to correspond to a distance larger than the actual distance. However, it is possible to reliably prevent from occurring any erroneous operation that may occur upon an uneven signal generation such as in FIG. 38(a) with respect to an object which only starts moving to traverse the detection area rather than moves in a direction of approaching the light receiving means. Furthermore, in operating the position detection, it will be possible to employ an operating means such as has been disclosed in U.S. Pat. No. 4,633,077 (or German Patent No. 3,407,210 or Italian Patent Application No. 47757-A/84) of an earlier invention of the same assignee as in the present case.
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