# US 2014/0153120 A1 · Accurate auto-focus method

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- Number: US 2014/0153120 A1
- Document ID: US20140153120A1
- Status: Published application
- Kind: A1
- Application number: 13/777,064
- Filed: 2013-02-26
- Published: 2014-06-05
- Earliest claimed: 2012-11-30
- Assignees: Hon Hai Precision Industry Co., Ltd.
- Applicants: Hon Hai Precision Industry Co., Ltd.
- Inventors: KUO-HUNG LIN
- Web page: https://patentgrep.com/patent/US20140153120A1

## CPC

- G02B 7/38: measured at different points on the optical axis {, e.g. focussing on two or more planes and comparing image data}
- G02B 7/36: using image sharpness techniques {, e.g. image processing techniques for generating autofocus signals (image data processing per se G06T; in cameras having a solid state image sensor H04N23/67)}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

An auto focus method includes: assigning searching boundaries L=InitL, R=InitR, and acquiring the resolutions f(L), f(R); defining the focused positions X1, X2 by the golden section method, and acquiring the resolution f(X1), f(X2); determining whether or not f(X1) is greater than f(X2); moving L adjacent to R when f(x1) is less than f(x2); moving R adjacent to L when f(x1) is greater than f(x2); acquiring the focused positions L, x1, x2, and R, and the resolution of the focused positions when L≠InitL and R≠InitR; acquiring an optimal focus point according to the focused positions L, X1, X2, and R, and the resolution of the focused positions.

## Claims

### Claim 1

An auto-focus method configured for controlling a focusing lens of a lens module to move to an optimal focused position Xp, comprising:
assigning searching boundaries InitL, InitR of the focusing lens to L, R respectively;
acquiring the resolutions f(L), f(R) of images captured by the lens module when the focusing lens is positioned on the two searching boundaries InitL, InitR, wherein f(X) represents the resolution of the image captured by the lens module when the focusing lens is positioned on a focused position X, X is a variable value greater than InitL and lower than InitR;
defining two focused positions X1, X2, wherein X1=L+(1−τ)×(R−L), X2=L+τ×(R−L), and T=0.618;
acquiring the resolutions f(X1), f(X2);
comparing f(X1) with f(X2) to determine whether or not f(X1) is greater than f(X2);
determining that L=X1, X1=X2, and X2=L+τ×(R−L) when f(X1) is lower than f(X2);
determining that R=X2, X2=X1, and X1=L+(1−τ)×(R−L) when f(X1) is greater than f(X2);
determining whether or not L≠InitL and R≠InitR are established;
acquiring the focused positions L, X1, X2, and R and the resolutions f(L), f(X1), f(X2), and f(R) when L≠InitL and R≠InitR are established; and
calculating the optimal focused position Xp according to the focused positions L, X1, X2, and R and the resolutions f(L), f(X1), f(X2), and f(R).

### Claim 2 (depends on 1)

The auto-focus method of claim 1, wherein L and R are variables, InitL and InitR are constants, and X1 and X2 are variables.

### Claim 3 (depends on 1)

The auto-focus method of claim 1, further comprising: returning to compare f(X1) with f(X2) when L≠InitL and R≠InitR are unestablished.

### Claim 4 (depends on 1)

The auto-focus method of claim 1, wherein calculating the optimal focused position Xp comprises:
orderly sampling three groups of the focused positions and the resolutions from the focused positions L, X1, X2, and R and the resolutions f(L), f(X1), f(X2), and f(R), and substituting each three groups of the focused positions and the resolutions into a parabolic equation to calculate four groups of peak coordinates (Xn1, f(n1)), (Xn2, f(n2)), (Xn3, f(n3)), (Xn4, f(n4)); and
acquiring the optimal focused position Xp according to:
Xp=(L*f(L)+X1*f(X1)+X2*f(X2)+R*f(R)+Xn1*f(n1)+Xn2*f(n2)+Xn3*f(n3)+Xn4*f(n4))/(L+X1+X2+R+Xn1+Xn2+Xn3+Xn4).

### Claim 5 (depends on 1)

The auto-focus method of claim 1, wherein calculating the optimal focused position Xp is according to: Xp=(L*f(L)+X1*f(X1)+X2*f(X2)+R*f(R))/(L+X1+X2+R).

### Claim 6 (depends on 1)

The auto-focus method of claim 1, wherein calculating the optimal focused position Xp comprises:
orderly sampling three groups of the focused positions and the resolutions from the focused positions L, X1, X2, and R and the resolutions f(L), f(X1), f(X2), and f(R), and substituting each three groups of the focused positions and the resolutions into a parabolic equation to calculate four groups of peak coordinates (Xn1, f(n1)), (Xn2, f(n2)), (Xn3, f(n3)), (Xn4, f(n4)); and
acquiring the optimal focused position Xp according to:
Xp=(Xn1*f(n1)+Xn2*f(n2)+Xn3*f(n3)+Xn4*f(n4))/(Xn1+Xn2+Xn3+Xn4).

### Claim 7 (depends on 1)

The auto-focus method of claim 1, wherein L=X1 represents that X1 is assigned to L, X1=X2 represents that X2 is assigned to X1, and X2=L+τ×(R−L) represents that X2 is defined via reassigned L.

### Claim 8 (depends on 1)

The auto-focus method of claim 1, wherein R=X2 represents that X2 is assigned to R, X1=X2 represents that X2 is assigned to X1, and X1=L+(1−τ)×(R−L) represents that X1 is defined via reassigned R.