Auto-focusing method and auto-focusing apparatus using the same

• US 20070212049A1
• Filed: 03/07/2007
• Published: 09/13/2007
• Est. Priority Date: 03/07/2006
• Status: Abandoned Application

• Current Assignee: Samsung Electro-Mechanics Co., Ltd. (Samsung Group)
• Original Assignee: Samsung Electro-Mechanics Co., Ltd. (Samsung Group)
• Inventors: Koc, Burhanettin, Kim, Sung Deuk, Guroglu, Serkan
• Application Number:
  US11/714,882
• Publication Number:
  US 20070212049A1
• Time in Patent Office: Days
• US Class Current: 396/127
• CPC Class Codes: G02B 13/001 Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras G02B23/243 takes precedence
• CPC Class Codes: G02B 7/346 using horizontal and vertical areas in the pupil plane, i.e. wide area autofocusing
• CPC Class Codes: G03B 13/36 Autofocus systems
• CPC Class Codes: H04N 23/673 based on contrast or high frequency components of image signals, e.g. hill climbing method

Abstract

A auto-focusing method comprises setting a plurality of active windows composed of a central window and a plurality of peripheral windows surrounding the central window and allocating weights to the plurality of active windows so as to calculate an auto-focus value for each step; calculating a rate of change in auto-focus value between a previous step and a current step from the auto-focus value calculated for each step; comparing the calculated rate of change in auto-focus value with preset auto-focus reference values and then changing a step size in accordance with the comparison result; transferring a lens to a position corresponding to the changed step size; repeating the above processes from the setting of the plurality of active windows to the transferring of the lens until the auto-focus value of the previous step becomes larger than that of the current step and then determining whether the maximum auto-focus value is detected or not; and transferring the lens to a position corresponding to the maximum auto-focus value.

Claims

1. An auto-focusing method comprising:

setting a plurality of active windows composed of a central window and a plurality of peripheral windows surrounding the central window and allocating weights to the plurality of active windows so as to calculate an auto-focus value for each step;

calculating a rate of change in auto-focus value between a previous step and a current step from the auto-focus value calculated for each step;

comparing the calculated rate of change in auto-focus value with preset auto-focus reference values and then changing a step size in accordance with the comparison result;

transferring a lens to a position corresponding to the changed step size;

repeating the above processes from the setting of the plurality of active windows to the transferring of the lens until the auto-focus value of the previous step becomes larger than that of the current step and then determining whether the maximum auto-focus value is detected or not; and

transferring the lens to a position corresponding to the maximum auto-focus value.

2. The auto-focusing method according to claim 1,

wherein in the transferring of the lens to the position corresponding to the maximum auto-focus value, the maximum auto-focus value is set to correspond to the auto-focus value of the previous step, and the lens is transferred to a position corresponding to the auto-focus value of the previous step.

3. The auto-focusing method according to claim 1 further comprising

determining whether or not the lens is transferred to a position corresponding to the maximum auto-focus value, in the transferring of the lens to the position corresponding to the maximum auto-focus value.

4. The auto-focusing method according to claim 1,

wherein the calculating of the rate of change in auto-focus value between the previous step and the current step is performed by the following equation:

5. The auto-focusing method according to claim 4,

wherein the preset auto-focus reference values are two threshold values different from each other.

6. The auto-focusing method according to claim 5,

wherein in the comparing of the calculated rate of change, the calculated rate of change in auto-focus value and the threshold values are compared, so that a step size is selected as any one of a fine step size, a medium step size, and a coarse step size in accordance with the comparison result.

7. The auto-focusing method according to claim 4,

wherein the comparing of the calculated rate of change further includes determining whether the auto-focus value passes by the peak or not, when the rate of change in auto-focus value between the previous step and the current step has a negative value.

8. The auto-focusing method according to claim 1,

wherein when the lens is transferred, the position of the transferred lens is detected and stored.

9. The auto-focusing method according to claim 1,

wherein the central window among the plurality of active windows are composed of a plurality of divided regions (windows).

10. The auto-focusing method according to claim 9,

wherein weights are allocated to all the regions corresponding to the plurality of central windows, and a weight is allocated to at least one of the plurality of peripheral windows.

11. The auto-focusing method according to claim 1,

wherein the weights allocated to the active windows are set to differ from each other.

12. An auto-focusing apparatus comprising:

a lens section on which an optical signal is incident, the lens section having a focus lens which is capable of moving vertically;

an image sensor and ISP section receiving the optical signal incident on the lens section so as to convert into an electrical signal and then outputting digitalized image data;

an auto-focusing digital signal processing section including;

an optical detection module receiving the image data from the image sensor and ISP section so as to extract predetermined image components, setting a plurality of active windows composed of a central window and a plurality of peripheral windows surrounding the central window, and allocating weights to the plurality of active windows such that the predetermined image components are integrated to calculate an auto-focus value; and

a CPU receiving the auto-focus value from the optical detection module and calculating the maximum auto-focus value while vertically driving the focus lens of the lens section in accordance with the auto-focus value, the CPU performing an auto-focusing algorithm in which a rate of change in auto-focus value between a previous step and a current step is calculated and then is compared with preset auto-focus reference values such that a step size is controlled to change in accordance with the comparison result; and

a driving section driving the focus lens of the lens section in accordance with a control signal of the auto-focusing digital signal processing section.

13. The auto-focusing apparatus according to claim 12,

wherein the optical detection module includes:

a high-pass filter receiving image data from the image sensor and ISP section so as to extract predetermined image components;

an integrator receiving the predetermined image components extracted from the high-pass filter and integrating and outputting the image components with respect to the respective active windows composed of the central window and the peripheral windows; and

an active region setting section transmitting the start and end addresses of the plurality of active windows to the integrator.

14. The auto-focusing apparatus according to claim 12 further comprising

a position detecting sensor for determining whether or not the lens is transferred to a position corresponding to the maximum auto-focus value.

15. The auto-focusing apparatus according to claim 12,

wherein the predetermined image component is any one of an edge component, a Y-component, and a Y-component with the maximum value.