KR20090087694A - Auto focus system and auto focus method using the same - Google Patents

Abstract

An auto focus system and an auto focus method using the same are provided to obtain a reliable auto focus signal by using an IR signal even under a low brightness condition. A lens unit(202) includes a plurality of lenses. An IR cut filter(203) is arranged on an optical axis. An iris(204) is arranged on the optical axis. A photographing device(205) photographs an image of a subject passed through the lens unit and the iris. An IR cut filter driving unit(206) is connected to the IR cut filter. The IR cut filter is selectively located on the optical axis according to the brightness around the subject by the IR cut filter driving unit.

Description

Auto focus system and auto focus method using the same {Auto focus system and auto focus method using the same}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an autofocus system, and more particularly, to an autofocus system having improved reliability at low luminance by selectively turning on and off an infrared cut filter, and an autofocus method using the same.

In general, a digital image processing apparatus refers to a device that processes an image such as a digital camera, a personal digital assistant (PDA), a camera phone, or uses a motion recognition sensor.

The digital image processing apparatus receives a desired image through the image pickup device, displays the input image on the image display device, displays the image, saves the image as an image file according to the photographing selection of the photographer, and prints the stored image file. .

The digital image processing apparatus is provided with an auto focus (AF) system. The autofocus system sets the composition toward the subject you want to shoot, and then automatically focuses and shoots as long as the shutter-release button is activated.

In general, conditions for successful autofocus include high contrast and high signal-to-noise ratio (hereinafter referred to as S / N). If the contrast is low, or the S / N is low, autofocus will not work properly at low brightness. Accordingly, in order to increase the reliability of autofocus at low luminance, there is a method of increasing contrast using an infrared signal (IR signal) or maintaining S / N by maintaining ISO.

1 illustrates a system 100 for performing autofocus using a conventional infrared signal.

Referring to the drawings, light passing through the plurality of lens units 101 travels along the optical axis O, and light (mainly visible light) other than the infrared region passes through the infrared reflecting mirror 102 inclined at a predetermined angle. It is incident on the charge coupled device 103.

On the other hand, the light in the infrared region is reflected by the infrared reflecting mirror 102, proceeds along the optical axis O 'perpendicular to the optical axis O, and is focused on the auxiliary lens unit 104 for AF direction selection. Incident on the CCD 105 for autofocus.

By the way, the conventional system 100 for performing auto focus is a means for separating and applying an infrared signal and visible light, there is a problem that the structure is complex, expensive and complicated control.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and the structure and method according to the autofocus system, and the autofocus using the same so as to obtain a reliable autofocus signal at low brightness by selectively turning on and off the infrared cut filter The main task is to provide a method.

In order to achieve the above object, an autofocus system according to an aspect of the present invention,

Lens unit consisting of a plurality of lenses; And,

An infrared cut filter disposed on the optical axis;

An iris disposed on the optical axis;

And an imaging device configured to capture an image of the subject passing through the lens unit and the iris.

The infrared cut filter is installed so as to be selectively positioned on the optical axis according to the brightness around the subject by the infrared cut filter driving unit connected thereto.

In addition, when the luminance around the subject is lower than the set reference luminance, the IR cutoff filter is turned on to be positioned on the optical axis.

When the luminance around the subject is higher than the set reference luminance, the IR cutoff filter is turned off to be positioned on the optical axis.

In addition, the infrared cut filter is characterized in that the hinge is coupled by the driving force of the infrared cut filter driving unit, or is coupled to the sliding selectively disposed on the optical axis.

Auto focus method according to another aspect of the present invention,

Determining a first shutter-release signal;

Turning on / off the infrared cut filter on the optical axis in comparison with the luminance around the subject and the set reference luminance;

Inputting an image of an image;

Auto process processing;

Determining a second shutter-release signal; And

And capturing and storing the image.

In addition, when the luminance around the subject is lower than the set reference luminance,

The infrared cut-off filter is turned off by the driving force of the infrared cut-off filter driver so that the infrared cut-off filter is not positioned on the optical axis to receive light in the infrared region and light other than the infrared region.

Furthermore, when the luminance around the subject is higher than the set reference luminance,

The infrared cut filter is turned on by the driving force of the infrared cut filter driving unit, and is positioned on the optical axis to block the incidence of light in the infrared region.

As described above, the autofocus system of the present invention and the autofocus method using the same provide reliable autofocus using IR signals even in low luminance conditions by turning on / off the infrared cut filter according to the luminance state around the subject. You can get a signal.

Hereinafter, preferred embodiments will be described in detail with reference to the accompanying drawings.

2 illustrates an auto focus system 200 according to an embodiment of the present invention.

Referring to the drawings, the auto focus system 200 includes a plurality of lens units 202, an IR cut filter 203, an iris iris, and a barrel 201. CCD 205 is arranged in sequence.

The lens unit 202 receives light from an external light source to process an image, the iris 204 adjusts the amount of incident light according to the degree of opening and closing, and the CCD 204 controls the lens unit 202. The amount of light inputted through the lens is accumulated and the image captured by the lens unit 202 is output in accordance with the vertical synchronization signal.

The infrared cut filter 203 may be positioned on the optical axis selectively by the infrared cut filter driver 206 according to whether the luminance around the subject is higher and lower than the reference luminance set, for example, the day mode or the night mode. It is installed.

The infrared blocking filter 203 is positioned on the optical axis by rotating by hinge coupling by the driving force provided from the infrared blocking filter driver 206 or sliding by sliding by the driving force provided by the infrared blocking filter driver 206. It is not limited to any one way.

At this time, the auto focus system is an optical system for automatically focusing on a subject. The compact digital camera does not have a separate auto focus sensor, but focuses by analyzing the contrast of the image obtained through the image charge coupled device / complementary metal oxide semiconductor (CCMOS) image sensor. TTL phase difference detection method is used.

The auto focus method is largely classified into an active system and a passive system. In active systems, the camera emits ultrasound or infrared light for distance measurement, while passive systems focus using light that is naturally reflected from the subject.

The auto focus control device has only one focus area (focus point), and recently has several focus areas. That is, having multiple auto focus areas on a frame provides a multi auto focus function that automatically detects and focuses on a subject. In an auto focus system that provides a multi-auto focus function, when a subject is included in each auto focus area, the auto focus area is displayed as an AF-OK area.

3A illustrates a case where an autofocus system at high brightness is applied according to an embodiment of the present invention, and FIG. 3B is a graph illustrating AF values for AF positions of the autofocus system of FIG. 3A.

Hereinafter, the same reference numerals as in the above-described drawings indicate the same members having the same function.

3A and 3B, light passing through the plurality of lens units 202 travels along the optical axis O, passes through the iris 204, and enters the CCD 205.

At this time, when the luminance around the subject is higher than the reference luminance set by the photographer, for example, in the daytime mode, the infrared cut-off filter driving unit 206 drives the infrared ray filter to pass only light (mainly visible light) outside the infrared region. The cutoff filter 203 is turned "ON" to be positioned on the optical axis O. Accordingly, light in the infrared region may be blocked by the infrared cut filter 203.

4A illustrates a case where an autofocus system at low brightness is applied according to another embodiment of the present invention, and FIG. 4B is a graph illustrating AF values for AF positions of the autofocus system of FIG. 4A.

4A and 4B, when the luminance around the subject is lower than the reference luminance set by the photographer, for example, in the night mode, the light passing through the plurality of lens units 202 travels along the optical axis O. And enters the CCD 205 through the iris 204.

At this time, since the luminance around the subject is low, to compensate for this, the infrared cut filter 203 is turned “OFF” by the driving force of the infrared cut filter driving unit 206 so as not to be positioned on the optical axis O. do. Accordingly, light in the infrared region and light (mainly visible light) other than the infrared region can be incident on the CCD 205 together.

As such, the infrared blocking filter 203 is not positioned on the optical axis O under low luminance conditions, so that not only the light in the infrared region but also the light in the infrared region is used, thus providing a reliable autofocus signal (AF). Signal).

FIG. 5A is a photograph of turning on an infrared cut filter at low luminance in an autofocus system according to an exemplary embodiment of the present invention, and FIG. 5B is a diagram illustrating an AF value of an AF position of the autofocus system of FIG. 5A. It is a graph shown.

Referring to FIGS. 5A and 5B, when the luminance around the subject is lower than the reference luminance, when the infrared cut filter 203 of FIG. 2 is positioned on the optical axis O, the amount of incident light is small. The auto focus value (AF value) for the (auto focus position, AF position) does not represent a peak value, and comes out low overall, resulting in a blurring AF-NG phenomenon.

In this AF-NG phenomenon, although the luminance around the subject is low, the infrared cut filter 203 is positioned on the optical axis O, so that light in the infrared region is blocked by the infrared cut filter 203, and thus the infrared light is blocked. This is because only light (mainly visible light) other than the area is used.

FIG. 6A is a photograph of turning off the IR cut filter at low luminance in the autofocus system of FIG. 5A, and FIG. 6B illustrates an AF value for an AF position of an autofocus system of the autofocus system of FIG. 6A. It is a graph.

6A and 6B, when the luminance around the subject is lower than the reference luminance, the infrared cut filter 203 of FIG. 2 is not positioned on the optical axis O, so that light outside the infrared region (mainly visible light) In addition, the light in the infrared region is incident together.

As a result, as the amount of incident light including the IR signal increases, the AF- where the focus value (AF value) according to the focus position (AF position) shows a peak in any area according to the position of the focus lens unit and the image is clearly displayed. OK phenomenon occurs.

Since the AF-OK phenomenon has a low luminance around the subject, the infrared cut filter 203 is not positioned on the optical axis O, so that not only light outside the infrared region (mainly visible light) but also light in the infrared region You can get it because you use it all together.

FIG. 7 is a flowchart illustrating a process of an autofocus system for turning on / off an infrared cut filter according to an exemplary embodiment of the present invention.

First, it is determined whether the first shutter release signal S1 is input while the subject is composed. (S10) If the first shutter release signal S1 is not input, the first shutter release is again performed. The operation of inputting the signal S1 is repeated.

On the other hand, if the first shutter-release signal S1 is input, it is determined whether the brightness around the subject is bright or dark (S20).

At this time, when the luminance around the subject is lower than the reference luminance set by the photographer, the infrared cutoff filter is turned off.

That is, when the brightness around the subject is dark, the infrared cut filter driving unit is driven so that the infrared cut filter connected thereto is not positioned on the optical axis. (Mostly, visible light)

On the contrary, when the luminance around the subject is brighter than the reference luminance, the infrared blocking filter connected to the infrared blocking filter driver is turned on so as to be positioned on the optical axis, thereby blocking the incident light in the infrared region as in the daytime mode. .

In this way, the infrared cut-off filter is turned on or off on the optical axis by comparing the luminance around the subject with the reference luminance, and then the image is captured by the CCD image pickup device to input the image of the image.

Subsequently, after going through an auto process S60 for setting an optimal focus lens position (S60), it is determined whether the second shutter-release signal S2 is input (S70).

After the second shutter-release signal S2, which is a shooting start signal, is input, the sharpest image is captured and stored, and then the operation is terminated (S80). On the other hand, the second shutter-release signal S2 If is not input, the operation of inputting the second shutter release signal S2 again is repeated.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

1 is a block diagram showing a conventional auto focus system,

2 is a block diagram showing an auto focus system according to an embodiment of the present invention;

3A is a block diagram illustrating a case where an autofocus system at high brightness is applied according to an embodiment of the present invention;

3B is a graph illustrating AF values according to AF positions of the autofocus system of FIG. 3A;

4A is a block diagram illustrating a case where an autofocus system at low brightness is applied according to another embodiment of the present invention;

4B is a graph illustrating AF values according to AF positions of the autofocus system of FIG. 4A;

5A is a photograph of turning on an infrared cut filter at low luminance in an autofocus system according to an embodiment of the present invention;

5B is a graph illustrating AF values according to AF positions of the autofocus system of FIG. 5A;

FIG. 6A is a photograph of turning off the IR cut filter at low luminance in the autofocus system of FIG. 5A; FIG.

6B is a graph illustrating AF values according to AF positions of the autofocus system of FIG. 6A;

7 is a flowchart illustrating a process of an autofocus system for turning on / off an infrared cut filter according to an exemplary embodiment of the present invention.

<Brief description of the major symbols in the drawings>

200 ... Auto Focus System 201 ... Tube

203 Lens section 203 Infrared cut filter

204 Iris 205 Imaging Device

206 ... infrared cut off filter driver

Claims (6)

Lens unit consisting of a plurality of lenses; And, An infrared cut filter disposed on the optical axis; An iris disposed on the optical axis; And an imaging device configured to capture an image of the subject passing through the lens unit and the iris. The infrared cut filter is installed so as to be selectively positioned on the optical axis according to the brightness around the subject by the infrared cut filter driving unit connected thereto. The method of claim 1, When the luminance around the subject is lower than the set reference luminance, the IR cutoff filter is turned on to be positioned on the optical axis. The autofocus system, characterized in that the infrared cut-off filter is turned off so as not to be located on the optical axis when the luminance around the subject is higher than the set reference luminance. The method of claim 1, And the infrared cut filter is hinge-coupled by the driving force of the infrared cut-off filter driver or is slidingly coupled to the infrared cut filter and selectively disposed on an optical axis. Determining a first shutter-release signal; Turning on / off the infrared cut filter on the optical axis in comparison with the luminance around the subject and the set reference luminance; Inputting an image of an image; Auto process processing; Determining a second shutter-release signal; And Capturing and storing the image; Autofocus method in an autofocus system comprising a. The method of claim 4, wherein If the luminance around the subject is lower than the set reference luminance, An autofocus method in an autofocus system, characterized in that the infrared cutoff filter is turned off by the driving force of the infrared cutoff filter driving unit, so that the infrared cutoff filter is not positioned on the optical axis to receive light in the infrared region and light outside the infrared region. The method of claim 4, wherein If the brightness around the subject is higher than the set reference brightness, An autofocus method in an autofocus system, characterized in that the infrared cutoff filter is turned on by the driving force of the infrared cutoff filter driving unit and positioned on the optical axis to block incidence of light in the infrared region.

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