Focus detecting system

Claim 2

A focus detecting system comprising: (a) three light receiving means disposed in a plane equivalent to the vicinity of a predetermined focal plane and forwardly and rearwardly of said plane; (b) operational means for operating the difference between the sharpness of the images on the light receiving means at the opposite ends, of said three light receiving means; (c) normalizing signal generating means for operating the difference between the sharpness of the image on the central light receiving means of said three light receiving means and the smaller one of the sharpness of the images on the light receiving means at the opposite ends; and (d) in-focus error signal generating means for finding the ratio of the output of said operational means to the output of said normalizing signal generating means and putting out an in-focus error signal that indicates the degree of deviation of the central light receiving means from an in-focus position.

Claim 3

A focus detecting system according to claim 1, further comprising: (a) first operational means for operating two times the sharpness of the image on the central light receiving means of said three light receiving means; (b) second operational means for operating the sum of the sharpness of the images on the light receiving means at the opposite ends, of said three light receiving means; and (c) effective indication signal generating signal indicative of the fact that the output of said in-focus error signal generating means is effective when the output of said first operational means is greater than the output of said second operational means.

Claim 4

A focus detecting system according to claim 2, further comprising: (a) first reference level generating means; (b) detecting means for detecting that the output of said in-focus error signal generating means is smaller than the output of reference level generating means; and (c) in-focus region signal generating means for judging an in-focus state and generating an in-focus region signal when said detecting means detects that the output of said in-focus error signal generating means is smaller than the output of said reference level generating means and the effective indication signal is put out by said effective indication signal generating means.

Claim 5

A focus detecting system according to claim 3, further comprising: (a) third operational means for operating the sum of the outputs of said three light receiving means; (b) second reference level generating means; (c) fourth operational means for operating the absolute value of the difference between the outputs of the light receiving means at the opposite ends, of said three light receiving means; (d) third reference level generating means; and (c) in-focus judgment impossibility signal generating means for comparing the output of said third operational means with the output of said second reference level generating means and generating an in-focus judgment impossibility signal indicative of the impossibility of in-focus judgment when the output of said third operational means is smaller than the output of said second reference level generating means or for comparing the output of said fourth operational means with the output of said third reference level generating means and generating the in-focus judgment impossibility signal when the output of fourth operational means is smaller than the output of said third reference level generating means.

Claim 6

A focus detecting system according to claim 4, further comprising: (a) near/far indication signal generating means for comparing the sharpnesses of the images on the light receiving means at the opposite ends, of said three light receiving means, thereby detecting whether the focal plane is forwardly or rearwardly of the predetermined focal plane and generating a near/far indication signal.

Claim 7

A focus detecting system according to claim 5, further comprising: (a) means adapted to generate a signal indicating that the output of said in-focus error signal generating means is effective and the output of said near/far indication signal generating means is effective when it is judged by said effective indication signal generating means that the in-focus error signal is ineffective and it is judged by said in-focus judgment impossibility signal generating means that in-focus judgment is not impossible.

Claim 8

A focus detecting system according to any one of claims 1 to 6, wherein the signals generated by said system are used for lens control.

Claim 9

A focus detecting system according to any one of claims 1 to 6, wherein the signals generated by said system are used for display.

Claim 10

A focus detecting system according to any one of claims 1 to 6, wherein each of said light receiving means includes: (a) a light receiver comprising a photoelectric conversion element; and (b) processing means adapted to put out a sharpness signal proportional to the sharpness of the image formed on said light receiver.

Claim 11

A focus detecting system comprising: (a) three light receiving means disposed in a plane equivalent to the vicinity of a predetermined focal plane and forwardly and rearwardly of said plane; (b) operational means for operating the difference between the sharpness of the images on the light receiving means at the opposite ends, of said three light receiving means; (c) normalizing signal generating means for generating a normalizing signal in accordance with the sharpness of the images on the said three light receiving means; (d) in-focus error signal generating means for finding the ratio of the output of said operational means to the output of said normalizing signal generating means and putting out an in-focus error signal; (e) first operational means for operating two times the sharpness of the image on the central light receiving means of said three light receiving means; (f) second operational means for operating the sum of the sharpness of the images on the light receiving means at the opposite ends, of said three light receiving means; and (g) effective indication signal generating means adapted to put out an effecitve indication signal indicative of the fact that the output of said in-focus error signal generating means is effective when the output of said first operational means is greater than the output of said second operational means.

Claim 12

A focus detecting system comprising: (a) three light receiving means disposed in a plane equivalent to the vicinity of a predetermined focal plane and forwardly and rearwardly of said plane; (b) operational means for operating the difference between the sharpness of the images on the light receiving means at the opposite ends, of said three light receiving means; (c) normalizing signal generating means for generating a normalizing signal in accordance with the sharpness of the images on the said three light receiving means; (d) in-focus error signal generating means for finding the ratio of the output of said operational means to the output of said normalizing signal generating means and putting out an in-focus error signal; (e) first operational means for operating two times the sharpness of the image on the central light receiving means of said three light receiving means; (f) second operational means for operating the sum of the sharpness of the images on the light receiving means at the opposite ends, of said three light receiving means; and (g) effective indication signal generating means adapted to put out an effecitve indication signal indicative of the fact that the output of said in-focus error signal generating means is effective when the output of said first operational means is greater than the output of said second operational means.