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US 4,544,255 AGranted
Focus detector
AssigneeNippon Kogaku K. K.
InventorKen Utagawa
Life of this patent
Estimating the term…
Abstract
A focus detector adaptable to a camera or other similar optical instrument is disclosed. The focus detector includes a pair of concave mirrors as refocusing optical system for forming secondary images the positional relationship of which is detected for focus detection. In order to eliminate the adverse effect of aberrations on the secondary image formation and to improve the accuracy of focus detection, the concave mirrors are inclined to satisfy a particularly determined condition on the incident angle to the mirrors. The condition is that the incidence angle should be less than about .sqroot.0.04/R wherein R is the maximum diameter of the mirror measured in mm.
Claims24
A focus detector for detecting whether or not an image-forming optical system is forming a primary image of an object on or near a predetermined image-forming plane, said focus detector comprising:
- (1) first and second concave mirrors disposed behind said predetermined image-forming plane and inclined at different inclination angles from each other so as to refocus the primary image within a predetermined detection area on or near the predetermined image-forming plane thereby forming first and second secondary images respectively,
- said inclination angles being so determined that each of the incidence angles (randian) of the beams coming from the center of said predetermined detection area and incident on the respective centers of said concave mirrors is smaller than about .sqroot.0.04/R wherein R is the maximum diameter in mm of said concave mirrors;
- and
- (2) photo-electric detection means for detecting the relative positional relationship between said first and second secondary images and forming a focus detection signal from the result of the detection.
1 more element
A focus detector for detecting whether an image-forming optical system is forming a primary image of an object on or near a predetermined image-forming plane, said focus detector comprising:
- (1) a field lens disposed in the vicinity of said predetermined image-forming plane;
- (2) first and second concave mirrors for reflecting the beam transmitted through said field lens and refocusing said primary image thereby forming first and second secondary images, said first and second concave mirrors being inclined at different angles from each other so as to positionally separate said first and second secondary images from each other;
- (3) first and second photo-electric element arrays for receiving said first and second secondary images respectively;
- (4) detection means for forming a focus detection signal from the outputs of said first and second photo-electric element arrays;
- (5) an elongated transparent block,
- the reflecting surfaces of said first and second concave mirrors being formed on one end surface of said transparent block perpendicular to the length thereof;
- one of said first and second photo-electric element arrays and said field lens being disposed close to the opposite end surface of said block,
- said block having a light pass-through surface substantially parallel to the length of said block, the other one of said field lens and said arrays being disposed opposed to said light pass-through surface;
- and
- (6) reflection means disposed within said block to form an optical path binding said concave mirrors and said light pass-through surface.
7 more elements
A focusing detector for detecting whether or not an image-forming optical system is forming a primary image of an object on or near a predetermined image-forming plane, said focus detector comprising:
- (1) a block made of a transparent material having a refractive index higher than 1;
- (2) a field lens disposed in the vicinity of said predetermined image-forming plane and being in close contact with a first portion of the outer surface of said block;
- (3) first and second concave mirrors for refocusing said primary image to form first and second secondary images respectively,
- said concave mirrors being juxtaposed and inclined at different angles from each other so as to positionally separate said first and second secondary images from each other, and
- the reflecting surfaces of said concave mirrors being formed on a second portion of the outer surface of said block;
- (4) first and second photo-electric element arrays arranged close to a third portion of said block outer surface for receiving said first and second secondary images respectively;
- (5) detection means for forming a focus detection signal from the outputs of said first and second photo-electric element arrays;
- (6) first optical path-forming means disposed within said block to guide the light passed through said field lens to said first and second concave mirrors;
- and
- (7) second optical path-forming means disposed within said block to guide the light reflected by said first and second mirrors to said first and second photo-electric element arrays.
7 more elements
A focus detector for detecting whether or not an image-forming optical system is forming a primary image of an object on or near a predetermined image-forming plane, said focus detector comprising:
- (1) a focus detection optical system including a field lens disposed in the vicinity of said predetermined image-forming plane, and first and second refocusing optical systems disposed behind said field lens to refocus said primary image thereby forming first and second secondary images respectively;
- and
- (2) first and second photo-electric element arrays to receive said first and second secondary images respectively, each of said photo-electric element arrays being composed of plural photo-electric elements arranged in array, the pitch at which said elements are arranged being locally changed in such manner that the images of the individual elements of said first array formed through said first refocusing optical system and said field lens and the images of the individual elements of said second array formed through said second focusing optical system and said field lens can substantially overlap each other on said predetermined image-forming plane with regard to the corresponding elements of said arrays.
A single lens reflex camera comprising:
- (1) a phototaking optical means;
- (2) a quick-return mirror for reflecting a portion of the light transmitted through said phototaking optical means and allowing the remaining portions of the light to pass through it;
- (3) an auxiliary mirror for reflecting the light passed through said quick-return mirror downwardly to form a primary object image through said phototaking optical means at a position under said mirror and in the vicinity of said predetermined image-forming plane;
- (4) a bottom plate disposed under said quick-return mirror, said plate being provided with an opening formed therein;
- (5) a field lens disposed in the vicinity of said predetermined image-forming plane;
- (6) first and second concave mirrors for reflecting the light passed through said opening and said field lens and refocusing said primary image to thereby form first and second secondary images, said first and second concave mirrors being inclined at different angles from each other so as to positionally separate said first and second secondary images from each other;
- (7) first and second photo-electric element arrays for receiving said first and second secondary images respectively;
- (8) detection means for forming a focus detection signal from the outputs of said first and second photo-electric element arrays;
- (9) an elongated transparent block disposed under said bottom plate with the longitudinal axis of the block being substantially parallel to said bottom plate,
- the reflecting surfaces of said first and second concave mirrors being formed on one end surface of said block perpendicular to the longitudinal axis of said block,
- said first and second photo-electric element arrays being disposed close to the opposite end surface of said block, and
- said block having a light pass-through surface extending substantially parallel to the longitudinal axis of said block, on which surface the light transmitted through said field lens is incident;
- and
- (10) reflection means disposed within said block to reflect the light coming from said light pass-through surface toward said concave mirrors.
11 more elements
A focus detector for detecting whether an image-forming optical system is forming a primary image of an object on or near a predetermined image-forming plane, said focus detector comprising:
- (1) an elongated transparent block having a first light pass-through surface at one end approximately perpendicular to the length thereof and a second light pass-through surface substantially parallel to said length, the light passed through said image-forming optical system entering said block through one of said first and second light pass-through surfaces;
- (2) reflection means disposed within said block to form an optical path binding said second light pass-through surface and the other end surface opposite to said one end;
- (3) first and second concave mirrors formed on the other end surface of said block for reflecting the light entering said block and for refocusing said primary image thereby forming first and second secondary images, said first and second concave mirrors being inclined at different angles from each other so as to positionally separate said first and second secondary images from each other;
- (4) first and second photo-electric element arrays disposed close to the other of said first and second light pass-through surfaces;
- and
- (5) detection means for forming a focus detection signal from the outputs of said first and second photo-electric element arrays.
3 more elements
A focusing detector for detecting whether or not an image-forming optical system is forming a primary image of an object on or near a predetermined image-forming plane, said focus detector comprising:
- (1) a block made of a transparent material having a refractive index higher than 1, said block having, on an outer surface thereof, first, second and third portions different in location from each other, the light which is passed through said image-forming optical system entering said block through said first portion;
- (2) first and second concave mirrors for refocusing said primary image to form first and second secondary images respectively,
- said concave mirrors being juxtaposed and inclined at different angles from each other so as to positionally separate said first and second secondary images from each other, and
- the reflecting surfaces of said concave mirrors being formed on said second portion of said block;
- (3) first and second photo-electric element arrays arranged close to said third portion of said block for receiving said first and second secondary images respectively;
- (4) detection means for forming a focus detection signal from the outputs of said first and second photo-electric element arrays;
- (5) first optical path-forming means disposed within said block to guide the light passed through said first portion to said first and second concave mirrors;
- and
- (6) second optical path-forming means disposed within said block to guide the light reflected by said first and second mirrors to said first and second photo-electric element arrays.
6 more elements
A single lens reflex camera comprising:
- (1) a phototaking optical means;
- (2) a quick-return mirror for reflecting a portion of the light transmitted through said phototaking optical means and allowing the remaining portions of the light to pass through it;
- (3) an auxiliary mirror for reflecting the light passed through said quick-return mirror downwardly to form a primary object image through said phototaking optical means at a position under said mirror;
- (4) a bottom plate disposed under said quick-return mirror, said plate being provided with an opening formed therein;
- (5) first and second concave mirrors for reflecting the light passed through said opening and refocusing said primary image to thereby form first and second secondary images, said first and second concave mirrors being inclined at different angles from each other so as to positionally separate said first and second secondary images from each other;
- (6) first and second photo-electric element arrays for receiving said first and second secondary images respectively;
- (7) detection means for forming a focus detection signal from the outputs of said first and second photo-electric element arrays;
- (8) an elongated transparent block disposed under said bottom plate with the longitudinal axis of the block being substantially parallel to said bottom plate,
- the reflecting surfaces of said first and second concave mirrors being formed on one end surface of said block approximately perpendicular to the longitudinal axis of said block,
- said first and second photo-electric element arrays being disposed close to the opposite end surface of said block, and
- said block having a light pass-through surface extending substantially parallel to the longitudinal axis of said block, on which surface the light transmitted through said opening is incident;
- and
- (10) reflection means disposed within said block to reflect the light coming from said light pass-through surface toward said concave mirrors.
10 more elements
A focus detector for detecting whether or not an image-forming optical system is forming a primary image of an object on or near a predetermined image-forming plane, said focus detector comprising:
- (1) a focus detection optical system including first and second refocusing optical systems for refocusing said primary image thereby forming first and second secondary images respectively;
- and
- (2) first and second photo-electric element arrays to receive said first and second secondary images respectively, each of said photo-electric element arrays being composed of plural photo-electric elements arranged in array, the pitch at which said elements are arranged being locally changed in such manner that the images of the individual elements of said first array formed through said focus detection optical system and the images of the individual elements of said second array formed through said focus detection optical system have the same pitch on said predetermined image-forming plane.
Dependencies are inferred from the claim text.