Distance measuring device

• US 4,575,211 A
• Filed: 04/16/1984
• Issued: 03/11/1986
• Est. Priority Date: 04/18/1983
• Status: Expired due to Term

• Current Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Original Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Inventors: Sato, Yuichi, Kawabata, Takashi, Tsunekawa, Tokuichi, Matsumura, Susumu
• Primary Examiner(s): Perkey, William B.
• Application Number:
  US06/601,054
• Time in Patent Office: 694 Days
• Field of Search: 354/403, 250/201 AF, 356/1
• US Class Current: 396/123
• CPC Class Codes: G01C 3/10 using a parallactic triangle with variable angles and a base of fixed length in the observation station, e.g. in the instrument
• 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

The disclosed distance measuring device is arranged to project light on an object. Reflected light from the object is received by a photo-electric converter to shift the position of a photo-taking lens to an in-focus position on the basis of a signal produced from the photo-electric converter. The projected light and/or the reflected light is divided into a multiplicity of light fluxes for the purpose of broadening and simplifying the distance measuring range and accuracy.

Claims

1. A distance measuring device, comprising:

light emitting means for projecting a light flux for distance measurement;

an optical member arranged to divide and split said projected light flux emitted by said light emitting means into a plurality of projection light fluxes;

scanning means for scanning with the plurality of projection light fluxes produced by said optical member;

photo-electric converting means arranged to receive reflected light fluxes resulting from said plurality of projected light fluxes, said converting means having a plurality of light receiving areas, each of said light receiving areas being arranged to produce a photo-electric converted signal representing a light flux incident thereon as a result of said scanning with said projected light fluxes; and

a circuit for receiving said photo-electric converted signals and producing distance measurement signals, said circuit being arranged to select, as an in-focus signal, any distance measurement signal that first becomes a value close to an in-focus value from distance measurement signals representing the mean value of the photo-electric converted signals from said light receiving areas of the photo-electric converting means, the output value of the photo-electric converted signals from a central part of the light receiving areas and a plurality of combined output values of the photo-electric converted signals from said light receiving areas from among said plurality of light receiving areas.

2. A light projecting device for distance measurement, comprising:

light emitting means for emitting and projecting light for distance measurement and for rotating such that a light spot therefrom scans between a close distance and a longer distance;

a light projecting lens arranged to direct the light projected by said light emitting means to an object whose distance is to be measured; and

a diffraction grating for diffracting the projected light into a zero order diffracted light and (+) and (-) first order diffracted light to project a plurality of spot lights onto the object.

3. A light projecting device according to claim 2, characterized said diffraction grating having recesses and protrusions adjusted that an intensity of the three lights diffracted by said diffraction grating corresponds to one of the following three cases:

(a) the intensities of the three lights diffracted by the diffraction grating are equal;

(b) intensity of said zero order diffracted light is weaker than intensity of said (+) and (-) first order diffracted light; and

(c) the intensity of said zero order diffracted light is stronger than the intensity of the (+) and (-) first order diffracted light.

4. A light projecting device for distance measurement, comprising:

light emitting means for emitting and projecting light for distance measurement;

a light projecting lens arranged to direct the light projected by said light emitting means to an object whose distance is to be measured; and

a diffraction grating for diffracting the projected light, said diffraction grating having grating lines tilted to a predetermined angle relative to a reference line vertical to the optical axis of said light flux, and a connecting line connecting spots on a surface of an object formed by a zero order diffracted light and (+) and (-) first order lights diffracted by said diffraction grating is tilted relative to the horizontal direction.

5. A light projecting device for distance measurement, comprising:

light emitting means for emitting and projecting light for distance measurement;

a light projecting lens arranged to direct the projected light of said light emitting means to an object whose distance is to be measured; and

a diffraction grating for diffracting the light and projecting a zero order diffracted light and (+) and (-) first order diffracted lights onto an object, said lights diffracted by said diffraction grating being adjusted to any one of the following;

(i) intensities of the three lights diffracted by the diffraction grating are equal;

(ii) intensity of said zero order diffracted light is stronger than intensity of said (+) and (-) first order diffracted lights, or;

(iii) the intensity of said zero order diffracted light is weaker than the intensity of said (+) and (-) first order diffracted light.

6. A distance measurement device, comprising:

light emitting means for projecting light for distance measurement;

a diffraction grating for diffracting the light into a zero order diffracted light and (+) and (-) first order diffracted lights and projecting a plurality of projected light spots onto an object;

driving means for inserting and retracting said diffraction grating into and from a light path of said projected light;

light receiving means having three receiving areas for receiving said three diffracted lights from said diffraction grating to produce signals from said three receiving areas corresponding to the intensity of the diffracted light impinging into a respective area when said diffraction grating is placed within said optical path of the projected light, and to produce signals corresponding to an intensity of light of the diffracted light impinging into a receiving area at a central part out of said three receiving areas when the diffraction grating is not placed within the optical path for the projected light.