# US 2010/0165174 A1 · Automatic focusing method and device in high-noise environment

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- Number: US 2010/0165174 A1
- Document ID: US20100165174A1
- Status: Published application
- Kind: A1
- Application number: 12/541,928
- Filed: 2009-08-15
- Published: 2010-07-01
- Earliest claimed: 2008-12-31
- Assignees: Altek Corporation
- Inventors: MING JIUN LIAW; SHIH YUAN PENG
- Web page: https://patentgrep.com/patent/US20100165174A1

## CPC

- G03B 13/34: Power focusing
- H04N 23/673: {based on contrast or high frequency components of image signals, e.g. hill climbing method}
- H04N 23/676: {Bracketing for image capture at varying focusing conditions}
- G03B: APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR (optical parts of such apparatus G02B; photosensitive materials or processes for photographic purposes G03C; apparatus for processing exposed photographic materials G03D)
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

An automatic focusing method and device in a high-noise environment are used for determining a focusing distance between a digital imaging device and an object to be photographed. The automatic focusing method includes the steps of capturing M pre-photographed images at different object distances respectively; loading the pre-photographed images; superposing every N (N<M) pre-photographed images to create (M−N+1) composite images; redefining the object distances corresponding to the (M−N+1) composite images; calculating high-frequency signals in the focusing regions of the (M−N+1) composite images; determining an optimum focusing object distance based on the relation between the high-frequency signals and corresponding object distances; and adjusting an automatic focusing lens to the optimum focusing object distance and accomplishing focusing.

## Claims

### Claim 1

An automatic focusing method in a high-noise environment, applicable for determining a focusing object distance between a digital image device and at least one object to be photographed, comprising:
taking pre-photographed images at different object distances;
loading the pre-photographed images;
superposing the pre-photographed images respectively to generate a composite image;
calculating an object distance corresponding to the composite image;
calculating a high-frequency signal of at least part of pixels in the composite image; and
determining the focusing object distance for the object to be photographed with the high-frequency signal and the corresponding object distance of the composite image as reference data.

### Claim 2 (depends on 1)

The automatic focusing method in a high-noise environment according to claim 1, wherein the high-frequency signal is calculated by a high-pass filter, a band-pass filter, Fourier transformation, discrete cosine transformation, or discrete wavelet transformation.

### Claim 3

A digital imaging device with automatic focusing in a high-noise environment, applicable for determining a focusing object distance for at least one object to be photographed, comprising:
a storage unit, for storing a plurality of pre-photographed images captured at different object distances;
a microprocessor, electrically connected to the storage unit, for loading the pre-photographed images;
an image superposition unit, arranged in the microprocessor, for superposing the pre-photographed images to generate a plurality of composite images under control of the microprocessor;
an object distance resetting unit, arranged in the microprocessor, for calculating an object distance corresponding to each of the composite images and deriving corresponding object distances of the same number as that of the composite images under control of the microprocessor; and
a high-frequency signal calculation unit, arranged in the microprocessor, for calculating the high-frequency signal of at least part of pixels in each of the composite images and deriving the high-frequency signals of the same number as that of the composite images under control of the microprocessor;
wherein the microprocessor determines the focusing object distance for the object to be photographed by using the high-frequency signals and the corresponding object distances.

### Claim 4 (depends on 3)

The digital imaging device with automatic focusing in a high-noise environment according to claim 3, further comprising an automatic focusing lens and an automatic focusing lens timing control circuit, wherein the automatic focusing lens timing control circuit is electrically connected to the automatic focusing lens and the microprocessor, and the automatic focusing lens timing control circuit receives at least one control instruction from the microprocessor, thereby driving the automatic focusing lens.

### Claim 5 (depends on 3)

The digital imaging device with automatic focusing in a high-noise environment according to claim 3, further comprising a photo-sensing element and a photo-sensing element timing control circuit, wherein the photo-sensing element timing control circuit is electrically connected to the photo-sensing element and the microprocessor, and the microprocessor controls the photo-sensing element timing control circuit to generate at least one control signal for driving the photo-sensing element, thereby enabling the photo-sensing element to generate at least one analog signal.

### Claim 6 (depends on 5)

The digital imaging device with automatic focusing in a high-noise environment according to claim 5, further comprising an analog-digital conversion circuit electrically connected to the photo-sensing element, the photo-sensing element timing control circuit, and the storage unit, wherein the analog-digital conversion circuit converts the analog signal from the photo-sensing element into a digital signal and stores the digital signal into the storage unit under control of the photo-sensing element timing control circuit and the microprocessor.

### Claim 7 (depends on 5)

The digital imaging device with automatic focusing in a high-noise environment according to claim 5, further comprising an automatic exposure parameter determination and control unit arranged in the microprocessor, for determining at least one of an exposure time, an aperture size, and an ISO value used in photographing the object to be photographed based on the environment in which the digital imaging device is photographing.

### Claim 8 (depends on 5)

The digital imaging device with automatic focusing in a high-noise environment according to claim 5, wherein the high-frequency signal calculation unit is a high-pass filter, a band-pass filter, a Fourier transformation unit, a discrete cosine transformation unit, or a discrete wavelet transformation unit.