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

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.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages of the present general inventive concept will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1A is a diagram illustrating a window within a picture;

FIG. 1B is a graph showing a focus value in accordance with a lens moving distance;

FIG. 2 is a graph for explaining the problems of an auto-focusing method according to the related art;

FIG. 3 is a block diagram illustrating an auto-focusing apparatus according to the present invention;

FIG. 4A is a diagram illustrating an auto-focusing digital signal processing section of FIG. 3;

FIG. 4B is an internal block diagram of an optical detection module of FIG. 4A;

FIG. 5 is a flow chart of an auto-focusing algorithm according to the invention;

FIG. 6 is a flow chart showing a process of calculating an auto-focus value in FIG. 5;

FIG. 7 is a diagram illustrating a plurality of active windows to which weights are allocated for the calculation of an auto-focus value;

FIG. 8 is a flow chart showing a process of adjusting a step size in FIG. 5;

FIG. 9 is a diagram showing a typical focus searching process according to the invention;

FIG. 10 is a diagram illustrating eight active windows to be applied to an embodiment of the invention;

FIG. 11 is a diagram showing changes in auto-focus value of the respective active windows for each lens position;

FIG. 12 is a diagram showing a change in overall auto-focus value for each step; and

FIG. 13 is a graph showing an operational example of an auto-focusing algorithm according to the embodiment of the invention.

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; andtransferring 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; anda 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; anda 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; andan 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.