Distance detecting apparatus
First Claim
1. A distance detecting apparatus including light projection means for projecting a light beam upon an object, and a light receiving element including a photoelectric transducer element which receives reflected light from an object being photographed, said photoelectric transducer element producing a photocurrent having a value which varies in accordance with the position of light impingement;
- the apparatus comprising;
the photoelectric transducer element being positioned so that an imaging point which is formed by reflected light from an object which is located at infinity is located at a position along the transducer element which is toward the light projection means with respect to the center of the photoelectric transducer element;
means for generating a constant bias current;
means for receiving said constant bias current and said photocurrent;
said means for receiving including a detector circuit for detecting the photocurrent produced by the photoelectric transducer element as superimposed with the constant bias current;
a calculation and output circuit for calculating and outputting information representing a distance to an object being photographed from the photocurrent output which is superimposed with the constant bias current;
said constant bias current generating means further comprising a bias current preset circuit for presetting the constant bias current;
and said bias current preset circuit presetting a bias current ratio so that the output from the calculation and output circuit is substantially proportional to the reciprocal of the distance to an object being photographed over an entire range across which the determination of distances is enabled.
1 Assignment
0 Petitions
Accused Products
Abstract
A light projector projects a light pulse upon an object being photographed. A position sensitive detector (PSD) receives reflected light from the object and produces photocurrents which depend on the position of incidence of the light thereon. The detector (PSD) is positioned so that the center of an imaging spot formed by the reflected light from the object when the latter is located at infinity is located toward the projector with respect to the center of PSD. Apparatus additionally comprising a detector circuit which detects the photocurrents produced by PSD as superimposed with bias currents, a calculation and output circuit which calculates and delivers information representing a distance to the object on the basis of photocurrent outputs which are superimposed with the bias currents, and a bias current ratio preset circuit which presets a bias current ratio so that a calculated output is substantially proportional to the reciprocal of the distance to the object over an entire range of distances across which the determination of a distance is enabled.
11 Citations
43 Claims
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1. A distance detecting apparatus including light projection means for projecting a light beam upon an object, and a light receiving element including a photoelectric transducer element which receives reflected light from an object being photographed, said photoelectric transducer element producing a photocurrent having a value which varies in accordance with the position of light impingement;
- the apparatus comprising;
the photoelectric transducer element being positioned so that an imaging point which is formed by reflected light from an object which is located at infinity is located at a position along the transducer element which is toward the light projection means with respect to the center of the photoelectric transducer element; means for generating a constant bias current; means for receiving said constant bias current and said photocurrent; said means for receiving including a detector circuit for detecting the photocurrent produced by the photoelectric transducer element as superimposed with the constant bias current; a calculation and output circuit for calculating and outputting information representing a distance to an object being photographed from the photocurrent output which is superimposed with the constant bias current; said constant bias current generating means further comprising a bias current preset circuit for presetting the constant bias current; and said bias current preset circuit presetting a bias current ratio so that the output from the calculation and output circuit is substantially proportional to the reciprocal of the distance to an object being photographed over an entire range across which the determination of distances is enabled. - View Dependent Claims (2)
- the apparatus comprising;
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3. A distance detecting apparatus including light projection means for projecting a light beam upon an object, and a light receiving element including a photoelectric transducer element which receives reflected light from an object being photographed, said photoelectric transducer element producing a photocurrent having a value which varies in accordance with the position of light impingement;
- the apparatus comprising;
the photoelectric transducer element being positioned so that an imaging point which is formed by reflected light from an object which is located at infinity is located at a position along the transducer element which is toward the light projection means with respect to the center of the photoelectric transducer element; means for generating a bias current; means for receiving said bias current and said photocurrent; said means for receiving including a detector circuit for detecting the photocurrent produced by the photoelectric transducer element as superimposed with the bias current; a calculation and output circuit for calculating and outputting information representing a distance to an object being photographed from the photocurrent output which is superimposed with the bias current; said bias current generating means further comprising a bias current preset circuit for presetting the constant bias current; said bias current preset circuit presetting a bias current ratio so that the output from the calculation and output circuit is substantially proportional to the reciprocal of the distance to an object being photographed over an entire range across which the determination of distances is enabled; said detector circuit including impedance transformer means for performing an impedance transformation for a signal photocurrent which is delivered from the photoelectric transducer element, said calculation and output circuit including a logarithmic compression diode, an output from the impedance transformer means being supplied to said logarithmic compression diode in the calculation and output circuit.
- the apparatus comprising;
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4. A distance detecting apparatus including light projection means for projecting a light beam upon an object, and a light receiving element including a photoelectric transducer element which receives reflected light from an object being photographed, said photoelectric transducer element producing a photocurrent having a value which varies in accordance with the position of light impingement;
- the apparatus comprising;
the photoelectric transducer element being positioned so that an imaging point which is formed by reflected light from an object which is located at infinity is located at a position along the transducer element which is toward the light projection means with respect to the center of the photoelectric transducer element; means for generating a bias current; means for receiving said bias current and said photocurrent; said means for receiving including a detector circuit for detecting the photocurrent produced by the photoelectric transducer element as superimposed with the bias current; a calculation and output circuit for calculating and outputting information representing a distance to an object being photographed from the photocurrent output which is superimposed with the bias current; said bias current generating means further comprising a bias current preset circuit for presetting the constant bias current; said bias current preset circuit presetting a bias current ratio so that the output from the calculation and output circuit is substantially proportional to the reciprocal of the distance to an object being photographed over an entire range across which the determination of distances is enabled; said bias current preset circuit comprising transistors forming current mirror circuits, resistors coupled to said transistors for presetting the magnitudes of said bias currents, and a constant current source coupled to said current mirror circuits for providing a constant current to each transistor of the current mirror circuits. - View Dependent Claims (6)
- the apparatus comprising;
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5. A distance detecting apparatus including light projection means for projecting a light beam upon an object, and a light receiving element including a photoelectric transducer element which receives reflected light from an object being photographed, said photoelectric transducer element producing a photocurrent having a value which varies in accordance with the position of light impingement;
- the apparatus comprising;
the photoelectric transducer element being positioned so that an imaging point which is formed by reflected light from an object which is located at infinity is located at a position along the transducer element which is toward the light projection means with respect to the center of the photoelectric transducer element; means for generating a bias current; means for receiving said bias current and said photocurrent; said means for receiving including a detector circuit for detecting the photocurrent produced by the photoelectric transducer element as superimposed with the bias current; a calculation and output circuit for calculating and outputting information representing a distance to an object being photographed from the photocurrent output which is superimposed with the bias current; said bias current generating means further comprising a bias current preset circuit for presetting the constant bias current; said bias current preset circuit presetting a bias current ratio so that the output from the calculation and output circuit is substantially proportional to the reciprocal of the distance to an object being photographed over an entire range across which the determination of distances is enabled; said bias current preset circuit establishing a bias current ratio IB2 /(IB1 +IB2) where IB1 and IB2 represent the bias currents generated by the bias current preset circuit, said ratio being chosen such that a calculated output IO from the calculation and output circuit is close to or less than 1/2-Δ
x/2t where 2t represents the total length of said photoelectric transducer element and Δ
x represents the shift of the image point from the center of the photoelectric transducer element in a direction away from the light projecting element.
- the apparatus comprising;
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7. A distance detecting apparatus comprising:
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a projection circuit for projecting a light pulse upon an object, the distance of which is to be determined; a photocurrent detector circuit for receiving reflected light from the object to provide a photocurrent, a bias current preset circuit for generating a bias current; a compression diode coupled to said detector circuit and said preset circuit whereby the photocurrent is superimposed upon said bias current which is in turn preset by said bias current preset circuit; a calculation and output circuit for deriving information representing the distance to the object being photographed from a voltage across said compression diode through which the photocurrent superimposed with the bias current passes; A/D conversion means for providing an A/D conversion of an output from the calculation and output circuit; and a control circuit for delivering control signals to said circuits. - View Dependent Claims (8, 9)
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10. A distance detecting apparatus comprising:
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projection means for projecting a light pulse upon an object; a semiconductor position sensitive element spaced by a baseline length from the projection means and positioned so that the point representing the center of the light reflected from the object which is at an infinity position is located at a position along the element closer to the light projection means with respect to the center of the semiconductor position sensitive element, the element including a pair of electrodes which deliver signal currents with a current ratio which corresponds to an imaging position thereon of reflected light from the object which is located at infinity; a current superimposition circuit for superimposing a bias current on each signal current which is delivered from the pair of electrodes; and a calculation circuit for calculating a distance to the object on the basis of an output from the current superimposition circuit, the bias currents being chosen so that one calculated distance does not correspond to two distances to the object. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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17. A distance detecting apparatus for a camera comprising:
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projection means for projecting light toward an object; a semiconductor position sensitive element for receiving reflected light from an object being photographed as a light beam is projected thereto from said projection means and for producing a pair of signal currents depending on the position thereon of incidence of the reflected light, the semiconductor position sensitive element being positioned so that reflected light from an object being photographed which is located at infinity impinges thereon at a position which is displaced toward the projection means from the center of the element; superimposition circuit means for superimposing bias currents upon the pair of signal currents; a bias current preset circuit for presetting predetermined bias currents which are superimposed upon the pair of signal currents; and a calculation circuit for calculating a distance to an object on the basis of an output from the superimposition circuit means; the predetermined values of said bias currents being selected so that the calculated output is substantially proportional to the reciprocal of a distance to an object to be photographed over an entire range across which the determination of distance is enabled. - View Dependent Claims (18, 19, 20)
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21. A method for operating a distance detecting apparatus comprised of a semi-conductor position sensitive element for receiving reflected light to produce a pair of signal currents whose magnitudes are dependent on the position thereon of light reflected from an object whose distance from the apparatus is being determined, said method comprising the steps of:
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(a) projecting light from a location in close proximity to said position sensitive element toward an object; (b) focusing the light reflected from the object recited in step (a) upon said position sensitive element; (c) positioning said position sensitive element so that the imaging point formed by the reflected light from the object recited in step (a) which is located at a distance which may be considered infinity impinges upon said position sensitive element at a point displaced by a displacement distance from the center of said position sensitive element toward said light projection location; (d) superimposing a respective bias current IB1, IB2 upon each of the current signals developed by the outputs of said position sensitive element; and (e) calculating the distance of the object recited in step (a) utilizing the currents superimposed on said base currents; (f) said bias currents being adjusted so that the calculated distance is substantially proportional to the reciprocal of the distance to said object over the entire surface of the position sensitive element. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29)
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30. A distance measuring apparatus for a camera comprising:
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projection means for projecting a light upon an object to be photographed; a semiconductor position sensitive element spaced a predetermined distance from said projection means for receiving the light reflected from the object to be photographed upon which the light is projected, said element including a pair of electrodes which respectively provide photocurrents depending upon the position at which the light is received along said element; amplifying means each coupled to one of said electrodes for providing only a change in photocurrent depending on the projection by said light projection means from a respective photocurrent outputted by a respective one of the electrodes of said semiconductor position sensitive element; means for generating bias currents; a pair of diodes each receiving the output current of one of said amplifying means and one of said bias currents for outputting a logarithmically compressed voltage; and calculation means to receive the respective outputs from said pair of diodes for calculating object distance;
whereby the output from the calculating means is determined substantially by said bias current when the object to be photographed is at an infinity position and is less influenced by said bias currents and is predominantly influenced by the photocurrents as the distance between the camera and the object to be photographed is reduced. - View Dependent Claims (31, 32, 33, 34, 35, 36)
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37. A distance measuring apparatus for a camera comprising:
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projection means for projecting a light upon an object to be photographed; a semiconductor position sensitive element spaced by a baseline length from said projection means and being positioned so that the center of the light reflected from an object located at an infinity position is located toward the light projection means with respect to the semiconductor position sensitive element for receiving the light reflected from the object to be photographed upon which the light is projected, said element including a pair of electrodes which respectively provide photocurrents whose values depend upon the position at which the light is received along said element; amplifying means for providing only a change in photocurrent depending on the projection by said light projection means from the respective photocurrents outputted by said pair of electrodes of said semiconductor position sensitive element; means for generating bias currents; a pair of diodes each receiving the output current of one of said amplifying means and one of said bias currents for outputting a logarithmically compressed voltage; and calculation means to receive the respective outputs from each of the said diodes for calculating object distance;
whereby said bias current generating means presets said bias currents so that the output from the calculating means is determined by said bias current when the object to be photographed is at an infinity position and is less influenced by said bias currents and is predominantly influenced by the photocurrents as the camera approaches the object to be photographed. - View Dependent Claims (38, 39, 40, 41, 42, 43)
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Specification