KR20040073182A - Photographing apparatus having function of back light compensation and control method thereof - Google Patents

Abstract

PURPOSE: A pickup device capable of performing a BLC(Back Light Compensation) is provided to automatically select a BLC area according to peripheral environmental changes, and to compensate for a brightness level for the selected BLC area, thereby photographing a clearer image. CONSTITUTION: A BLC mode selection key(260a) applies a selection signal for an automatic mode that automatically selects a predetermined number of BLC areas. A CCD pickup unit(230) converts an optical signal of a subject to be pictured into an electrical signal. A signal processor(250) detects a brightness signal from the electrical signal. An iris(210) controls lightness. A controller(290) controls the signal processor(250) to calculate a brightness level for the BLC areas when the selection signal is received, selects the first BLC area having the lowest brightness level, and outputs an iris driving control signal to compensate for the lowest brightness level. An iris driver(212) controls an open/shut rate of the iris(210).

Description

Image capturing apparatus capable of backlight compensation and its control method {Photographing apparatus having function of back light compensation and control method}

The present invention relates to an image pickup device capable of back light correction and a control method thereof, and more particularly, to back light interference by automatically setting an area requiring back light correction when imaging a subject in a back light state. An imaging apparatus and a control method thereof are minimized.

When photographing a subject using a digital imaging device such as a digital still camera or a surveillance camera for Closed Circuit Television (CCTV), if there is an external light emitter such as natural light or a fluorescent lamp around the subject, the subject may not be backlit by the external light emitter. It is placed so that it is not clear and is dark.

This allows the subject to be photographed in the normal photographing mode without setting the backlight compensation mode, so that the opening and closing degree of the aperture is adjusted according to the high luminance level with respect to the external light emitting body incident through the aperture of the imaging device without considering the low luminance level of the subject. Because. That is, in the general image capturing mode, the aperture ratio of the aperture is reduced according to the high luminance level of the external light emitting body, thereby reducing the amount of light incident on the CCD.

In order to solve this problem, a back light compensation function (hereinafter referred to as "BLC") is inherent in the imaging device. BLC function is to reduce the effects of external light emitters and other interference to the subject to ensure the sharp image quality of the subject to correct the backlight so that the image having the optimal sharpness is captured.

Such a BLC function is generally performed when the BLC mode is selected by a predetermined operation key provided in the main body of the imaging apparatus. When the BLC mode is selected to enter the BLC mode, the conventional imaging apparatus provides an on-screen display (OSD) screen as shown in FIG. 1 as a display device such as a liquid crystal display (LCD).

Referring to FIG. 1, the OSD screen is divided into 48 regions, and the BLC region for performing the BLC function is selected by manually operating a predetermined direction key provided in the main body. In the case of FIG. 1, four BLC regions shown in black have been selected by manipulation of a predetermined direction key or the like, and the conventional imaging apparatus controls the opening and closing degree of the aperture to perform backlight compensation for the selected BLC region. As a result, the amount of light flowing through the iris is controlled, and thus the BLC function is performed.

However, in the above-described conventional imaging apparatus, when performing the BLC mode, a suitable BLC region must be manually selected according to the surrounding environment such as the position of the subject, the imaging apparatus, and the presence or absence of an external light emitter. In this case, since the BLC region is selected at the user's discretion, it is difficult to select a suitable BLC region, and the BLC function is degraded unless the appropriate BLC region is reselected whenever the surrounding environment changes. Therefore, in the case of performing the BLC mode using the conventional imaging apparatus, a user may have inconvenience in having to manually reselect a suitable BLC region whenever the surrounding environment changes.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide an image pickup apparatus capable of performing back light correction and a control method thereof so that a sharp subject is picked up by automatically selecting a BLC region according to a change in the surrounding environment such as an external light emitter or a subject position. .

1 is a view showing an OSD screen for implementing a BLC function provided from a conventional imaging device;

2 is a block diagram schematically showing an image pickup apparatus capable of backlight compensation according to a preferred embodiment of the present invention;

3 is a view for explaining an OSD screen implemented by the OSD processing unit of FIG.

4 is a flowchart for explaining a BLC control method of the image pickup apparatus shown in FIG. 2;

5A and 5B illustrate an embodiment of an OSD screen implemented by the OSD processor of FIG. 2.

Description of the main parts of the drawing

200: imaging device 210: aperture

230: CCD imaging unit 250: signal processing unit

260a: BLC mode selection key 270: OSD processing unit

290: control unit

In order to solve the above technical problem, the imaging apparatus according to the present invention includes a mode selection key for applying a selection signal for an automatic mode for automatically selecting a predetermined number of backlight compensation areas from a plurality of preset backlight compensation areas; And an imaging unit for converting an optical signal of an incident object into an electrical signal, a signal processing unit for detecting a luminance signal from the electrical signal, an aperture for adjusting an amount of light incident to the imaging unit, and the automatic mode selection signal When received, the signal processor controls the signal processing unit to calculate a brightness level for each of the backlight compensation areas, selects a first backlight compensation area having the lowest brightness level among the calculated brightness levels for each of the backlight compensation areas, and A control unit for outputting an aperture control signal to correct the lowest luminance level of the selected first backlight compensation region and the aperture driver; Depending on the signal and a diaphragm drive section for adjusting the opening rate of the iris.

In more detail, when the first backlight compensation area is selected, the controller selects at least one second backlight compensation area from the backlight compensation areas having a brightness level within a brightness level that is greater than a minimum brightness level by a predetermined ratio. After calculating the average luminance level with respect to the luminance levels of the selected first and second backlight compensation areas, the aperture driving control signal is output to the aperture driver to correct the calculated average luminance level.

The control unit may select at least one second backlight compensation region such that the sum of the first and second backlight compensation zones is within 30% to 40% of the plurality of preset backlight compensation zones. And sequentially selecting from the backlight compensation area having the lowest brightness level and the minimum brightness level difference, wherein the predetermined ratio is within 110%, and each of the backlight compensation areas is at least one backlight compensation adjacent to each of the backlight compensation areas. The area and the predetermined area overlap.

The display apparatus may further include an OSD processing unit configured to OSD process the plurality of backlight compensation regions and output the OSD to the display device when the automatic mode selection signal is received.

On the other hand, in order to solve the above technical problem, the image pickup device according to the present invention converts the optical signal of the subject into an electrical signal, and performs a backlight compensation for the subject by detecting the luminance signal from the electrical signal A control method of an imaging device, comprising: detecting a luminance signal from the electrical signal, applying an automatic mode selection signal for automatically selecting a predetermined number of backlight compensation areas from a plurality of backlight compensation areas, and When the automatic mode selection signal is received, calculating a brightness level for each of the backlight compensation areas, and selecting a first backlight compensation area having the lowest brightness level among the calculated brightness levels for each of the backlight compensation areas. And an aperture control signal for controlling the opening and closing rate of the iris to correct the lowest luminance level of the selected first backlight compensation region. And a step of outputting.

More specifically, after the step of selecting the first backlight compensation region, determining whether a backlight compensation area having a brightness level within a brightness level within a predetermined ratio greater than the lowest brightness level exists in the plurality of backlight compensation areas; Selecting at least one second backlight compensation area having a brightness level within a brightness level greater than a minimum brightness level by a predetermined ratio and an average brightness level with respect to the brightness levels of the selected first and second backlight compensation areas; It further includes the step of calculating.

In the selecting of the second backlight compensation area, the second backlight compensation area is selected so that the sum of the first and second backlight compensation areas is within 30% to 40% of the plurality of preset backlight compensation areas. Select at least one, and sequentially select from the backlight compensation region having the lowest luminance level and the minimum luminance level difference, and the predetermined ratio is within 110%. The method may further include, after the receiving of the automatic mode selection signal, OSD processing the plurality of backlight compensation regions and outputting the OSD to the display device.

According to the present invention, the brightness level of the subject is adjusted by automatically selecting the BLC area and controlling the opening and closing rate of the aperture, so that even when the surrounding environment is changed, optimal backlight compensation is always performed without having to manually reset the BLC area. Can be.

Hereinafter, with reference to the accompanying drawings will be described in detail the present invention.

2 is a block diagram schematically showing an image pickup apparatus capable of backlight compensation according to a preferred embodiment of the present invention.

2, the imaging apparatus 200 according to the present invention includes an aperture 210, an aperture driving unit 212, an aperture driving control unit 214, a pulse generator 220, a CCD imaging unit 230, and signal conversion. A unit 240, a signal processor 250, a key input unit 260, an OSD processor 270, a storage unit 280, and a controller 290 are provided.

The aperture 210 adjusts the amount of light incident from the outside according to the aperture diameter value of the aperture 210, that is, the degree of opening and closing, and is driven by the aperture driver 212. In addition, the aperture driving unit 212 is controlled by the aperture driving control unit 214 operated by the aperture driving control signal generated from the control unit 290.

The pulse generator 220 controls charge accumulation pulses so that charges are accumulated in a region of the CCD corresponding to the subject, and charges are prevented from accumulating in the region of the CCD corresponding to the external light emitter. Output to CCD imaging unit 230.

The CCD imaging unit 230 converts and outputs an optical signal of an incident object to an electric image signal according to the charge erasing pulse output from the pulse generator 220. The signal converter 240 converts the electrical analog signal output from the CCD imager 230 into a digital signal through correlation double sampling and automatic gain adjustment.

The signal processor 250 performs a process such as encoding and compression on the digitally converted signal. In addition, the signal processor 250 processes the digital video signal output from the signal converter 240 to separate the luminance signal and the color difference signal. In addition, when the BLC mode selection key 260a and the BLC automatic mode to be described later are sequentially selected, the signal processor 250 calculates the luminance levels for each of the BLC regions divided into a predetermined number and outputs the luminance levels to the controller 290.

The key input unit 260 is a user interface for generating a command for selecting or performing a function supported by the imaging apparatus 200 to the controller 290. To this end, the key input unit 260 has a BLC mode selection key 260a for backlight compensation as well as a plurality of keys (not shown) for applying performance command signals for various functions.

After the BLC mode selection key 260a is selected and one of the BLC auto mode and the BLC manual mode is selected by the key operation of the key input unit 260, the OSD processing unit 270 displays the nine BLC areas (Fig. 3). The OSD screen divided into 1 to 9) is output to a display device such as an LCD (Liquid Crystal Display).

Here, the BLC auto mode is a mode that performs a BLC function by automatically selecting a BLC area requiring backlight compensation according to the luminance level of each BLC area, and the BLC manual mode is a BLC for a BLC area requiring backlight compensation selected by a user. This mode is to perform a function. In addition, the display device may be an external display device provided in the scratch device 200 or connected by a communication interface (not shown).

Referring to FIG. 3, the regions shown by the diagonal lines are adjacent BLC regions of a plurality of BLC regions (for example, 1 and 2, 2 and 3, 4 and 5, 5 and 6, 7 and 8, 8 and 9). It indicates that some of the duplicates. This is because a more accurate BLC function can be performed by displaying a part of each BLC region overlapping, which will be described later.

The storage unit 280 stores location information of the BLC area divided into a predetermined number.

The controller 290 controls the overall operation of the imaging apparatus 200 according to a control program stored in the storage 280 or other storage medium (not shown) and the key manipulation of the key input unit 260. For example, the controller 290 reads out location information of each BLC area from the storage 280 and then outputs an area control signal corresponding to the read location information to the pulse generator 220.

Hereinafter, the operation of the control unit related to performing the BLC function will be described in more detail.

FIG. 4 is a flowchart for explaining a BLC control method of the image pickup apparatus shown in FIG. 2.

2 to 4, when the power is turned on to the imaging apparatus 200, and when a signal in which the BLC mode selection key 260a is selected is received (S405 and S410), the controller 290 is illustrated in FIG. 3. The OSD processor 270 is controlled to provide an OSD screen as a display device (S415). The OSD screen is divided into a predetermined number of BLC areas, and the number of divisions is not limited. In the present invention, a case in which nine areas (shown as 1 to 9) are divided will be described as an example.

In addition, OSD processing of a part of each BLC region by overlapping the OSD screen of FIG. 3 may include a difference in luminance level between the average luminance level and the selected BLC region when calculating the average luminance level of the BLC regions automatically selected by the controller 290. This is to obtain a clearer subject image by adjusting the opening / closing ratio of the aperture 210 by minimizing.

When the BLC automatic mode selection signal is received by the key operation of the key input unit 260 after performing step S415 (S420), the controller 290 controls the pulse generator 220 to generate charge erasing pulses for each BLC region. The control unit 250 controls the signal processor 250 to calculate a luminance level of each BLC region by calculating a luminance signal from the incident and photoelectrically converted signal according to the charge erasing pulse (S425).

When the luminance level of each BLC region is calculated, the controller 290 selects the first BLC region having the lowest luminance level among the calculated luminance levels of each BLC region (S430). For example, when the luminance level of each BLC region of the signal processor 250 has the same value as that of FIG. 5A, the controller 290 corresponds to the BLC region indicated by 7 of FIG. 3, that is, the lowest of '70IRE'. A BLC region having a luminance level is selected. Institute Radio Engineers (IRE) indicate the brightness of an image signal.

When the first BLC region is selected, the controller 290 determines whether there is a BLC region having a luminance level within a luminance level that is greater than a minimum luminance level by a predetermined ratio (S435). 2BLC region is selected (S440).

In more detail, the controller 290 determines the presence or absence of the BLC region having a luminance level within a predetermined ratio of 110%, that is, within the (lowest luminance level x 1.1), and determines the luminance level within the (lowest luminance level x 1.1). A predetermined number of second BLC regions having a low luminance level are further extracted from the BLC regions. In addition, the controller 290 may control the OSD processor 270 to visually display the selected BLC area.

In this case, the controller 290 selects at least one second BLC region such that the sum of the first and second BLC regions is within 30% to 40% of the divided BLC regions, and the minimum luminance level and the minimum luminance level are selected. Selected sequentially from the BLC region having the difference.

For example, after performing step S435, in the present invention, the controller 290 further extracts two second BLC regions so that one third of the nine BLC regions, that is, three first and second BLC regions are selected. can do. In addition, in the case of having a total of 15 BLC regions, it is possible to further extract 5 to 6 second BLC regions.

Referring to FIG. 5A, the controller 290 determines whether there is a luminance level existing within 110% of '70IRE', that is, within '77IRE'. In the case of FIG. 5A, the controller 290 further selects a BLC region having '75IRE' corresponding to the BLC region indicated by 8 of FIG. 3.

Referring to FIG. 5B, the control unit 290 selects the first BLC region having the lowest luminance level '70IRE' in step S430, and then performs step S435. In operation S435, since there is no BLC region having a luminance level within 1.1 times that of '70IRE', that is, within '77IRE', the controller 290 does not select the second BLC region.

When the first and / or second BLC region for performing the BLC function is automatically selected, the controller 290 determines an average value of luminance levels of the selected BLC region, that is, the first and second BLC regions, output from the signal processor 250. After the calculation (S445), the aperture driving control signal for correcting the calculated average luminance level is output to the aperture driving control unit 214 (S450).

In operation S450, a value for correcting the calculated average luminance level is a reference luminance level, for example, a value of about '100IRE', and the controller 290 controls the aperture driving controller 214 to control the aperture 210. The luminance level of the selected BLC region incident through is approximately '100IRE'. As a result, the luminance level of the entire BLC region is also slightly increased.

The aperture driving control unit 214 generates an aperture driving signal according to the aperture driving control signal output from the controller 290, and the aperture driving unit 212 adjusts the opening and closing degree of the aperture 210 according to the aperture driving signal. Thus, the BLC function is automatically performed by adjusting the amount of light incident through the aperture 210.

On the other hand, if the BLC mode selection key is not selected in step S410, the control unit 290 executes a routine for the normal shooting mode for imaging the subject without performing the BLC function (S455).

In addition, when a BLC manual mode selection signal other than the BLC automatic mode selection signal is received in step S420, the controller 290 receives a selection signal for a predetermined number of BLC areas manually selected by the user (S460). When a predetermined number of BLC region selection signals are received, the controller 290 controls the OSD processor 270 to visually display the selected BLC region.

After calculating the average luminance level for the selected BLC region (S465), the aperture driving control signal for correcting the calculated average luminance level is output to the aperture driving controller 214 (S450).

In addition, if the BLC manual mode is selected in step S420, it is also possible to perform the BLC function during the production process or by using a predetermined number of BLC areas preset by the user.

When the BLC mode is selected in step S410, after performing step S420 without outputting the OSD screen as shown in FIG. 3, it may be designed to provide an OSD screen according to whether the BLC auto mode is selected in step S420. That is, it is also possible to perform step S460 by providing an OSD screen only when the BLC automatic mode selection signal is not received in step S420.

Meanwhile, the image pickup apparatus 200 according to the present invention as described above outputs the OSD screen as shown in FIG. 3 only when the BLC manual mode is selected after the BLC mode selection key 260a is selected, and the BLC automatic mode is selected. In this case, it can be designed to automatically implement the BLC function without outputting the OSD screen.

In addition, either the BLC automatic mode or the BLC manual mode selected in step S420 is stored in the storage unit 280, and when the power is newly turned on, the controller 290 uses the mode stored in the storage unit 280 to perform the BLC function. Do it.

In addition, the imaging apparatus 200 according to the present invention selects at least one BLC region automatically or manually according to a change in the surrounding environment such as the position of an external light emitter or a subject, and according to the average luminance level of the selected BLC region 210. Perform optimal BLC function by controlling the opening and closing rate of.

In addition, the imaging apparatus 200 according to the present invention may be applied to a digital imaging apparatus such as a CCTV system, a digital still camera, a digital camcorder, and the like. After performing the BLC mode, the BLC region is automatically reselected according to the change of the surrounding environment. Function can be performed.

Although the present invention has been described in detail through the representative embodiments, those skilled in the art to which the present invention pertains can make various modifications without departing from the scope of the present invention. Will understand. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined by the claims below and equivalents thereof.

As described above, according to the image pickup apparatus capable of backlight compensation and its control method, the luminance level of the selected backlight compensation area is corrected by automatically selecting the backlight compensation area according to the change of the surrounding environment such as the external light emitter and the position of the subject. By this, a clear subject can be captured. That is, even when the surrounding environment is changed, the optimal backlight compensation can be performed without having to manually reselect the backlight compensation area.

Claims (12)

A mode selection key for applying a selection signal for an automatic mode for automatically selecting a predetermined number of backlight compensation areas from a plurality of preset backlight compensation areas; An imaging unit for converting an optical signal of an incident subject into an electrical signal; A signal processor detecting a luminance signal from the electrical signal; An aperture to adjust the amount of light incident on the image pickup unit; When the automatic mode selection signal is received, the signal processor is controlled to calculate a brightness level for each of the backlight compensation areas, and the first backlight has the lowest brightness level among the calculated brightness levels for each of the backlight compensation areas. A controller which selects a correction area and outputs an aperture driving control signal to correct the lowest luminance level of the selected first backlight compensation area; And And an aperture driver for adjusting the opening and closing rate of the aperture according to the aperture driving control signal. The method of claim 1, When the first backlight compensation area is selected, the controller selects at least one second backlight compensation area from the backlight compensation areas having a brightness level within a brightness level that is greater than the lowest brightness level by a predetermined ratio, and the selected first and second And calculating the average luminance level with respect to the luminance level of the two backlight compensation region and outputting the aperture driving control signal to the aperture driver to correct the calculated average luminance level. The method of claim 2, The control unit selects at least one of the second backlight compensation area such that the sum of the first and second backlight compensation areas is within 30% to 40% of the plurality of preset backlight compensation areas, and the lowest luminance. And a backlight compensation area having a level and a minimum luminance level difference are sequentially selected. The method of claim 2, And the predetermined ratio is within 110%. The method of claim 1, And wherein each of the backlight compensation areas overlaps a predetermined area with at least one backlight compensation area adjacent to each of the backlight compensation areas. The method of claim 1, And an OSD processing unit for OSD processing the plurality of backlight compensation regions and outputting the plurality of backlight compensation regions to a display device when the automatic mode selection signal is received. In the control method of the imaging device for converting the optical signal of the subject by the image pickup device into an electrical signal, and detecting the luminance signal from the electrical signal to perform a back light compensation for the subject, Detecting a luminance signal from the electrical signal; Applying an automatic mode selection signal for automatically selecting a predetermined number of backlight compensation areas from the plurality of backlight compensation areas; Calculating a brightness level for each of the backlight compensation areas when the automatic mode selection signal is received; Selecting a first backlight compensation area having the lowest brightness level among the calculated brightness levels for each of the backlight compensation areas; And And outputting an aperture driving control signal for controlling the opening and closing rate of the iris to correct the lowest luminance level of the selected first backlight compensation region. The method of claim 7, wherein After the step of selecting the first backlight compensation area, determining whether a backlight compensation area having a brightness level within a brightness level within a predetermined ratio greater than the lowest brightness level exists in the plurality of backlight compensation areas; Selecting at least one second backlight compensation area from the backlight compensation areas having a brightness level within a brightness level greater than the lowest brightness level by a predetermined ratio; And And calculating an average luminance level with respect to the luminance levels of the selected first and second backlight compensation areas. The method of claim 8, The selecting of the second backlight compensation region may include at least one second backlight compensation region such that the sum of the first and second backlight compensation zones is within 30% to 40% of the plurality of preset backlight compensation zones. The control method of the image pickup apparatus, characterized in that the selection is sequentially selected from the backlight compensation region having the minimum luminance level and the minimum luminance level difference. The method of claim 8, And the predetermined ratio is within 110%. The method of claim 7, wherein And wherein each of the backlight compensation areas overlaps a predetermined area with at least one backlight compensation area adjacent to each of the backlight compensation areas. The method of claim 7, wherein And after the automatic mode selection signal receiving step, OSD processing the plurality of backlight compensation areas to output them to a display device.