Auto-focusing method
First Claim
1. A method of carrying out auto-focusing by displacing a lens along the direction of an optical axis of said lens in accordance with a correlation between outputs from a pair of solid-state image sensors, said method comprising the steps of:
- passing light through said lens and impinging the light passed through said lens on both of said solid-state image sensors;
scanning each of said pair of solid-state image sensors thereby producing respective outputs A(n) and B(n);
converting said outputs A(n) and B(n) into digital data A'"'"'(n) and B'"'"'(n);
calculating Fourier transforms F1 (u), F2 (u), G1 (u) and G2 (u) using the following equations, ##EQU8## where N is the number of photoelectric elements in each of said pair of solid-state image sensors, u=0, 1, 2, . . . , M, and M is an integer which is equal to or smaller than (N/2)-1;
calculating the following values F0, G0, F(u) and G(u) from said F1 (u), F2 (u), G1 (u) and G2 (u), ##EQU9## calculating the following value f*g, using said F0, G0, F(u) and G(u), in a timed sequence at a predetermined time period for variable t, ##EQU10## determining an amount of displacement of said lens in accordance with a value of said variable t which gives a maximum value for said f*g, whereby if said amount of displacement thus determined is outside of a predetermined range, said lens is displaced to an in-focus position according to said amount of displacement thus determined.
1 Assignment
0 Petitions
Accused Products
Abstract
An auto-focusing method includes a scanning step for scanning a pair of solid-state image sensors on which light from a subject of interest impinges as passing through a focusing lens, an A/D conversion step, a Fourier transformation step, a convolution operation step, a peak detection step for determining an amount of displacement of said lens from the results of said convolution, and a lens displacement step for displacing said lens according to the displacement amount thus determined. The present auto-focusing method is least susceptible to noises and not adversely affected by differences in contrast of the subject of interest.
17 Citations
5 Claims
-
1. A method of carrying out auto-focusing by displacing a lens along the direction of an optical axis of said lens in accordance with a correlation between outputs from a pair of solid-state image sensors, said method comprising the steps of:
-
passing light through said lens and impinging the light passed through said lens on both of said solid-state image sensors; scanning each of said pair of solid-state image sensors thereby producing respective outputs A(n) and B(n); converting said outputs A(n) and B(n) into digital data A'"'"'(n) and B'"'"'(n); calculating Fourier transforms F1 (u), F2 (u), G1 (u) and G2 (u) using the following equations, ##EQU8## where N is the number of photoelectric elements in each of said pair of solid-state image sensors, u=0, 1, 2, . . . , M, and M is an integer which is equal to or smaller than (N/2)-1; calculating the following values F0, G0, F(u) and G(u) from said F1 (u), F2 (u), G1 (u) and G2 (u), ##EQU9## calculating the following value f*g, using said F0, G0, F(u) and G(u), in a timed sequence at a predetermined time period for variable t, ##EQU10## determining an amount of displacement of said lens in accordance with a value of said variable t which gives a maximum value for said f*g, whereby if said amount of displacement thus determined is outside of a predetermined range, said lens is displaced to an in-focus position according to said amount of displacement thus determined. - View Dependent Claims (2, 3, 4, 5)
-
3. The method of claim 2 wherein said value of variable t giving a maximum value for f*g is determined by comparing said L(I) each other and designated as I(MAX) which is then compared with a pair of predetermined values C1 and C2 thereby indicating a too close condition if I(MAX) is larger than C1, a too far condition if I(MAX) is smaller than C2 and an in-focus condition if I(MAX) is larger than C1 but smaller than C2.
-
4. The method of claim 3 wherein the lens is moved only when said I(MAX) is either larger than C1 or smaller than C2 and said amount of displacement of said lens is determined according to said I(MAX).
-
5. The method of claim 4 further comprising the step of displaying a focusing condition determined by said step of comparing I(MAX) with C1 and C2.
-
Specification