Digitally active distance measurement apparatus for camera or the like

• US 5,294,802 A
• Filed: 11/24/1992
• Issued: 03/15/1994
• Est. Priority Date: 11/25/1991
• Status: Expired due to Term

• Current Assignee: Olympus Optical Corporation Limited (Olympus Corporation)
• Original Assignee: Olympus Optical Corporation Limited (Olympus Corporation)
• Inventors: Kunishige, Keiji
• Primary Examiner(s): Nelms, David C.
• Assistant Examiner(s): DAVENPORT, TERESA
• Application Number:
  US07/980,688
• Time in Patent Office: 476 Days
• Field of Search: 250/561, 250/201.6, 356/1, 356/4
• US Class Current: 250/559.31
• CPC Class Codes: G01S 17/10 using transmission of interrupted, pulse-modulated waves determination of distance by phase measurements G01S17/32
• CPC Class Codes: G01S 7/486 Receivers
• CPC Class Codes: G02B 7/32 using active means, e.g. light emitter including both an active and a passive focus detecting device G02B7/285; using ultrasound G02B7/40

Abstract

In the first aspect, light reflected by an object upon projection of a beam on the object is received by a light-receiving section. A photocurrent corresponding to the irradiated position is detected by a photocurrent detection section and is compared with a predetermined level by a comparison/determination section. An ordinary photocurrent output from the photocurrent detection section prior to projection of the beam is digitally converted by a set/clear section of each bit of a digital value. The converted value is stored in a memory section. In projection of the beam, the ordinary photocurrent corresponding to the output from the memory section is extracted from the photocurrent output from the photocurrent detection section by an ordinary photocurrent extraction section without using a hold capacitor. In the second aspect, light is repeatedly projected from a projecting section on an object, and light reflected by the object is repeatedly received by a light-receiving section. After an object distance is calculated by an analog distance measurement arithmetic section in the light-receiving section, it is A/D-converted into digital data. This digital data representing the object distance is digitally accumulated in an adder section, thereby obtaining an object distance from a plurality of distance measurement arithmetic values without using an integral capacitor.

Claims

1. A distance measurement apparatus for a camera, comprising:

an infrared-emitting diode for projecting an infrared-ray on a distance measurement object a plurality of number of times;

an optical position detection element for receiving light reflected by the distance measurement object upon incidence of the infrared-ray thereon and outputting a photocurrent corresponding to an irradiated position of the light and an ordinary photocurrent;

a first A/D converter for detecting the ordinary photocurrent of said optical position detection element prior to projection operations performed by said infrared-emitting diode the plurality of number of times, and converting a detected ordinary photocurrent into a digital signal;

a first digital memory circuit for storing the digital signal converted by said first A/D converter;

a current extraction circuit for setting a current having a value corresponding to a storage value of said first digital memory circuit in the projection operations, and extracting a set current from the photocurrents output by said optical position detection element;

an analog arithmetic circuit for outputting an analog distance signal corresponding to a distance to the distance measurement object, using an output current of said optical position detection element from which the set current corresponding to the ordinary photocurrent is extracted by said current extraction circuit;

a second A/D converter for converting the analog distance signal into a digital distance signal;

a second digital memory circuit in which latest outputs from said second A/D converter are sequentially added and accumulated every time the projection operation is performed; and

a processing circuit for performing digital processing corresponding to arithmetic averaging of data accumulated in said second digital memory circuit upon completion of the projection operations performed the plurality of number of times.

2. A distance measurement apparatus comprising:

projecting means for projecting an infrared-ray on a distance measurement object;

light-receiving means for receiving light reflected by the distance measurement object upon projection of the infrared-ray on the distance measurement object, and outputting a photocurrent corresponding to an irradiated position of the light and an ordinary photocurrent;

first A/D converting means for detecting the ordinary photocurrent output from said light-receiving means prior to a projection operation by said projecting means, and converting a detected ordinary photocurrent into a digital signal;

first digital memory means for storing the digital signal converted by said first A/D converting means;

current extracting means for extracting a current component corresponding to a storage value of said first digital memory means from the photocurrents output by said light-receiving means during the projection operation;

analog arithmetic means for outputting an analog distance signal corresponding to a distance to the distance measurement object, using an output current from said light receiving means upon processing by said current extracting means;

second A/D converting means for converting the analog distance signal into a digital distance signal; and

second digital memory means for storing an output from said second A/D converting means.

3. A distance measurement apparatus comprising:

projecting means for repeatedly projecting light on a distance measurement object;

light-receiving means for receiving light reflected by the distance measurement object upon projection of the light on the distance measurement object and outputting a photocurrent containing an ordinary photocurrent component;

ordinary photocurrent extracting means for storing the photocurrent as the ordinary photocurrent component output by said light-receiving means during non-projection of said projecting means, extracting the ordinary photocurrent component from the photocurrent during projection of said projection means by using a storage value, and outputting a signal corresponding to the projection, the ordinary photocurrent component being digitally stored;

arithmetic means for calculating an analog object distance using the signal output by said ordinary photocurrent extracting means; and

accumulating means for accumulating outputs from said arithmetic means in accordance with repeated projection by said projecting means and outputting an average object distance of all projection operations, said accumulating means converting an analog output from said arithmetic means into digital data, and accumulating converted digital values.

4. An apparatus according to claim 3, wherein said light-receiving means, said ordinary photocurrent extracting means, said arithmetic means, and said accumulating means are formed as an integrated circuit on a single substrate.

5. A distance measurement apparatus comprising:

projecting means for projecting a beam toward an object;

light-receiving means for receiving light reflected by the object upon incidence of the beam thereon and outputting a photocurrent signal containing an ordinary photocurrent component;

analog-to-digital converting means for performing analog-to-digital conversion of the photocurrent signal as the ordinary photocurrent component output by said light-receiving means during non-projection of said projecting means;

memory means for storing a digital value of the ordinary photocurrent component converted by said digital-to-analog converting means;

current extracting means for extracting the ordinary photocurrent component from the photocurrent signal output by said light-receiving means during projection of said projecting means on the basis of the digital value stored in said memory means; and

arithmetic means for calculating a distance to the object using an output current from said light-receiving means from which the ordinary photocurrent component is extracted by said current extracting means.

6. An apparatus according to claim 5, wherein said light-receiving means includes a position sensing device for generating a pair of photocurrents in accordance with an irradiated position of a reflected light, and

said analog-to-digital converting means, said memory means, and said photocurrent extracting means are arranged for each of the pair of photocurrents.

7. An apparatus according to claim 5, wherein

said light-receiving means comprises a plurality of photodiodes for generating photocurrent signals in accordance with light-receiving amounts of a reflected light, and

said analog-to-digital converting means, said memory means, and said photocurrent extracting means are arranged for each of said plurality of photodiodes.

8. An apparatus according to claim 5, wherein said analog-to-digital converting means includes a sequential comparison type converter.

9. An active distance measurement apparatus comprising:

an infrared-emitting diode for projecting an infrared-ray on a distance measurement object through a projection lens;

an optical position detecting element for receiving, through a light-receiving lens, light reflected by the distance measurement object upon projection of the infrared-ray on the distance measurement object, and outputting a photocurrent corresponding to an irradiated position and an ordinary photocurrent;

an A/D converter for detecting the ordinary photocurrent output by said optical position detecting element prior to a projection operation by said infrared-emitting diode, and converting the ordinary photocurrent into a digital signal;

a digital memory circuit for storing the digital signal converted by said A/D converter;

a current extraction circuit for extracting a current corresponding to a storage value of said digital memory circuit from the photocurrents output by said optical position detecting element during the projection operation; and

an arithmetic circuit for outputting a signal corresponding to a distance to the distance measurement object, using an output from said optical position detecting element from which the current is extracted by said current extraction circuit.

10. An active distance measurement apparatus comprising:

projecting means for projecting an infrared-ray on a distance measurement object through a projection lens;

means for receiving, through a light-receiving lens, light reflected by the distance measurement object upon projection of the infrared-ray on the distance measurement object, and outputting a photocurrent corresponding to an irradiated position and an ordinary photocurrent;

means for storing the ordinary photocurrent output by said light-receiving means as a digital signal prior to a projection operation by said projecting means;

means for extracting a current corresponding to a storage value of said storing means from the photocurrents output by said light-receiving means during the projection operation; and

means for calculating a distance to the distance measurement object, using an output from said light-receiving means from which the current is extracted by said extracting means.

11. A distance measurement apparatus comprising:

projecting means for projecting a beam toward an object;

light-receiving means for receiving light reflected by the object upon projection of the beam on the object and outputting a photocurrent signal containing an ordinary photocurrent component;

a flip-flop group, a digital output of which a value is sequentially changed in synchronism with a clock pulse;

digital-to-analog converting means for converting the digital output from said flip-flop group into an analog current having a value corresponding to the value of the digital output, and extracting the analog current from the photocurrent signal output by said light-receiving means;

voltage transforming means for converting the analog current output by said digital-to analog converting means into a voltage signal;

comparing means for comparing the voltage signal converted by said voltage transforming means with a reference voltage;

digital memory means for storing a comparison result from said comparing means in association with a change in the value of the digital output by said flip-flop group in a state prior to projection by said projecting means, thereby storing the ordinary current component as a digital value; and

arithmetic means for extracting the ordinary photocurrent component from the photocurrent signal output by said light-receiving means on the basis of the digital value stored in said digital memory means during projection of the beam by said projecting means, and calculating a distance to the object using a signal current component obtained in an extracting operation.

12. An apparatus according to claim 11, wherein said light-receiving means has two output means, and said arithmetic means has differential amplifying means for receiving outputs from said two output means.

13. A distance measurement apparatus comprising:

projecting means for projecting light on an object;

light-receiving means for receiving light reflected by the object upon projection of the light on the object, and outputting a photocurrent signal containing an ordinary photocurrent component;

ordinary photocurrent extracting means for storing the photocurrent signal as the ordinary photocurrent component output by said light-receiving means in non-projection of said projecting means, extracting the ordinary photocurrent component from the photocurrent signal in projection of said projecting means, using a storage value, and outputting a signal corresponding to projection, the ordinary photocurrent component being stored as a digital value; and

arithmetic means for calculating an object distance using the signal output by said ordinary photocurrent extracting means.

14. An apparatus according to claim 13, wherein said ordinary photocurrent extracting means comprises analog-to-digital converting means including:

digital-to-analog converting means for generating a current value corresponding to a digital value;

comparing means for comparing to detect a coincidence between the current value generated by said digital-to-analog converting means and the photocurrent signal output by said light-receiving means; and

memory means for storing the digital value obtained when said comparing means detects the coincidence.

15. A distance measurement apparatus comprising:

projecting means for projecting distance measurement light on an object; and

light-receiving means for receiving light reflected by the object upon projection of the distance measurement light on the object to obtain a distance signal corresponding to a distance to the object, said light-receiving means including;

(a) means for detecting an ordinary light component contained in the reflected light in advance, and storing the ordinary light component in the form of a digital signal; and

(b) means for eliminating the ordinary light component from an output from said light-receiving means on the basis of a storage value in said memory means during projection by said projecting means.

16. A distance measurement apparatus for a camera, comprising:

an infrared-emitting diode for projecting an infrared-ray on a distance measurement object;

an optical position detection element for receiving light reflected by the distance measurement object upon incidence of the infrared-ray thereon, and outputting a photocurrent corresponding to an irradiated position;

an analog arithmetic circuit for outputting an analog distance signal corresponding to a distance to the distance measurement object, using an output from said optical position detection element;

an A/D converter for converting the analog distance signal into a digital distance signal;

a control circuit for operating said infrared-emitting diode, said optical position detection element, and said analog arithmetic circuit so as to perform distance measurement operations a plurality of number of times;

a memory circuit in which latest outputs from said A/D converter are sequentially added and accumulated whenever each of the distance measurement operations performed the plurality of number of times is performed; and

a processing circuit for performing digital processing corresponding to arithmetic averaging of data accumulated in said memory circuit upon completion of the distance measurement operations performed the plurality of number of times.

17. A distance measurement apparatus comprising:

projecting means for repeatedly projecting a beam toward an object;

light-receiving means for receiving light components reflected by the object upon repeated projection of the beam, and outputting a photocurrent signal;

arithmetic means for outputting an analog current signal corresponding to a distance to the object, on the basis of a signal corresponding to the photocurrent signal output by said light-receiving means;

a flip-flop group, a digital output of which a value is sequentially changed in synchronism with a clock pulse;

digital-to-analog converting means for generating an analog converted current corresponding to the value of the digital output from said flip-flop group, and extracting the analog converted current from the analog current signal output by said arithmetic means;

voltage transforming means for generating a voltage signal corresponding to the analog converted current output by said digital-to-analog converting means;

comparing means for comparing the voltage signal from said voltage transforming means with a reference voltage;

digital memory means for storing a comparison result from said comparing means in association with a change in the value of the digital output from said flip-flop group, thereby storing a digital value corresponding to the analog current signal output by said arithmetic means; and

accumulating means for adding the digital value stored in said memory means in accordance with the repeated projection by said projecting means to output an accumulated value of outputs from said arithmetic means upon completion of all projection operations.

18. An active distance measuring means comprising:

(a) projecting means for projecting an infrared-ray on a distance measurement object;

(b) light-receiving means for receiving light reflected by the distance measurement object upon radiation of the infrared-ray on the distance measurement object, and outputting an analog signal corresponding to a distance to the distance measurement object;

(c) converting means for converting the analog signal output by said light-receiving means into a digital signal;

(d) control means for operating said projecting means, said light-receiving means, and said converting means a plurality of number of times;

(e) memory means in which latest digital outputs from said converting means are sequentially added and accumulated whenever the plurality of number of times is performed; and

(f) arithmetic means for performing arithmetic operations corresponding to arithmetic averaging of the data stored in said memory means.

19. An active distance measurement apparatus for projecting distance measurement light on an object a plurality of number of times, receiving light reflected by the object, and obtaining a digital distance signal corresponding to an object distance, comprising:

memory means for adding and accumulating the digital distance signal whenever each of the distance measurement operations performed the plurality of number of times is performed; and

processing means for performing digital processing corresponding to arithmetic averaging of the data stored in said memory means.

20. An active distance measurement apparatus comprising:

(a) projecting means for projecting distance measurement light on an object a plurality of number of times;

(b) light-receiving means for receiving light reflected by the object whenever each of projection operations performed the plurality of number of times is performed and outputting digital data corresponding to a distance to the object; and

(c) arithmetic means for adding and accumulating a plurality of digital data from said light-receiving means and obtaining a final object distance on the basis of an accumulation content.

21. A distance measurement apparatus comprising:

projecting means for repeatedly projecting a pulsed light on an object;

light-receiving means for receiving light reflected by the object upon projection of the pulsed light on the object and outputting a photoelectric signal;

arithmetic means for calculating a distance to the object, using a value corresponding to the photoelectric signal output by said light-receiving means; and

accumulating means for accumulating outputs from said arithmetic means in accordance with repeated projection by said projecting means, said accumulating means converting an output from said arithmetic means into a digital value, and accumulating a converted digital value.

22. An apparatus according to claim 21, wherein said arithmetic means outputs an analog current corresponding to the distance, and

said accumulating means comprises:

analog-to-digital converting means including;

(a) digital-to-analog converting means for generating a current value corresponding the digital value,

(b) comparing means for comparing to detect a coincidence between the current value generated by said digital-to-analog converting means and the analog current output from said arithmetic means, and

(c) memory means for storing the digital value when said comparing means detects the coincidence; and

adding means for adding the digital value stored in said memory means in synchronism with the repeated projection.

23. An apparatus according to claim 21, wherein said light-receiving means, said arithmetic means, and said accumulating means are integrated on a single substrate.

24. An active distance measurement system comprising:

projecting means for projecting distance measurement light on an object; and

light-receiving means for receiving light reflected by the object and outputting object distance data, said light-receiving means being constituted by a one-chip IC and including at least;

(a) a light-receiving element for receiving the reflected light from the object;

(b) an analog arithmetic circuit for outputting an analog distance signal corresponding to a distance to the object in accordance with an output from said light-receiving element;

(c) an A/D converter for converting the analog distance signal from said analog arithmetic circuit into a digital distance signal; and

(d) a transfer circuit and a terminal for transferring the digital distance signal from said A/D converter to an external processing circuit.