KR20070069653A - Apparatus and method for controlling auto exposure of digital camera - Google Patents

Abstract

An apparatus and a method for controlling auto exposure of a digital camera are provided to attach a liquid crystal filter to an optical signal input terminal of a camera lens to control transmissivity of a optical signal inputted through the lens and enable auto exposure control of a desired pixel region of a camera image. An apparatus for controlling auto exposure of a digital camera includes a liquid crystal filter(14), a liquid crystal driver(15), and a controller(16). The liquid crystal filter includes a plurality of cells interposed between two glass substrates and each of the cells controls transmissivity of an optical signal inputted to a photo-electric converter(13) of the digital camera. The liquid crystal driver varies arrangement of liquid crystal molecules of the cells of the liquid crystal filter by adjusting a voltage difference of electrodes for the cells to control transmissivity of light which is transmitted through each cell of the liquid crystal filter. The controller controls the liquid crystal driver to analyze a camera image signal transmitted from the photo-electric converter in a software manner when an auto exposure control mode is set to control transmissivity of optical signals transmitting cells of the liquid crystal filter, which correspond to a pixel region having an illumination level higher than a predetermined illumination level.

Description

Apparatus And Method For Controlling Auto Exposure Of Digital Camera}

1 is a block diagram showing an automatic exposure control apparatus of a digital camera according to the present invention.

FIG. 2 is a diagram illustrating an implementation position of a liquid crystal filter in FIG. 1. FIG.

FIG. 3 is a flowchart illustrating an automatic exposure control operation (when a pixel area for exposure control is selected by software) of a digital camera according to an embodiment of the present invention.

4 is a flowchart illustrating an automatic exposure control operation (when a pixel area for exposure control is selected by a user) of a digital camera according to another embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

11 lens portion 12 optical filter portion

13 photoelectric conversion unit 14 liquid crystal filter unit

15 liquid crystal drive unit 16 control unit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to exposure control of a digital camera. In particular, an automatic exposure control of a camera image is possible by adjusting a transmittance of an optical signal input by inserting a filter using a liquid crystal in front and rear of a camera lens. An automatic exposure control apparatus and method of a digital camera.

Recently, along with high sensitivity miniaturization and light weight of electronic components, the size has gradually decreased and the demand for digital cameras is rapidly increasing in place of cameras using general film according to consumer's desire. Camera phones with digital camera functions have been developed and are widely used.

In addition, the consumer's desire for good images in digital cameras has led to the need for a number of additional features, which has led to the use of flash, Macro, Auto Focus, Optical Zoom, Many functions such as auto exposure have been developed and used.

In this case, the automatic exposure function is a basic function of the camera and is not satisfied to this day. In particular, there is a problem in that performance is lowered even in a too bright place.

For example, when you take a picture with the sun and the sun in the background, or when you take a picture by the window, if you set the exposure level on the background, the image of the actual subject (subject) will be darkened. There was a problem where the background was shot in white.

In order to compensate for this, conventionally, the function of the mechanical shutter and the aperture are used, but in this case, the overall brightness is lowered. There is a problem in that noise occurs on the screen because the brightness is adjusted using the control.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object thereof is to insert a liquid crystal filter into an optical signal input terminal of a digital camera, for example, a front / rear end of a camera lens to adjust the transmittance of an optical signal input through the lens. In this way, it is possible to automatically adjust the exposure of the desired pixel area for the camera image.

Another object of the present invention is to enable exposure control without deterioration and noise by applying an optical control method using a liquid crystal filter to a digital camera.

Features of the present invention for solving the above objects, the lens unit for receiving the optical signal for the subject and background, the optical filter unit for blocking the optical noise and infrared components of the optical signal input through the lens unit and And a photoelectric conversion unit for converting an optical signal passing through the optical filter unit into an electrical signal and transmitting a pixel array signal having a predetermined size. The digital camera is a filter in which a liquid crystal is injected between glass plates and formed into a plurality of cells. A liquid crystal filter unit adjusting the transmittance of the optical signal input to the photoelectric conversion unit for each cell; By adjusting the voltage difference of the electrode for each cell of the upper and lower glass plates constituting the liquid crystal filter unit, by changing the arrangement of the liquid crystal molecules for each cell injected between the glass plates, the transmittance of light passing through each cell of the liquid crystal filter unit A liquid crystal drive unit for controlling; Perform a digital signal processing on the camera image signal, which is a pixel array signal transmitted from the photoelectric conversion unit, to generate camera image data and then output a series of image codecs to the screen display, but the automatic exposure control mode is set. When the camera image data is analyzed by software, each cell corresponding to the liquid crystal driver to adjust the transmittance of an optical signal passing through each cell of the liquid crystal filter corresponding to the pixel area having a luminance equal to or greater than a predetermined illuminance level value. An automatic exposure control apparatus of a digital camera including a control unit for controlling the voltage difference of the electrode with respect to the.

Here, the liquid crystal filter unit may be implemented between the lens unit and the optical filter unit to be embedded in the camera module, or may be configured at the front end of the lens unit and implemented outside the camera module.

The control unit may further include a pixel area and transmittance control level selected to control exposure in the camera image output to the screen display unit when the automatic exposure control function is selected by the user while the camera image data is output to the screen display unit. And controlling the voltage difference of the electrode for each corresponding cell of the liquid crystal driver to adjust the transmittance of the optical signal passing through each corresponding cell of the liquid crystal filter unit according to the information.

Another feature of the present invention is to convert the optical signal for the subject and background input through the lens unit when entering the shooting mode into a pixel array signal of a predetermined size, which is an electrical signal, and then performs image codec processing to generate camera image data. Outputting to the screen display unit; If the automatic exposure control mode is set, analyzing the camera image data by software to measure illuminance for each pixel, and extracting a pixel region in which illuminance is measured above a predetermined illuminance level value; The arrangement of the liquid crystal molecules with respect to the cell region of the liquid crystal filter corresponding to the pixel region is outputted so that the camera image data of which the illumination intensity of the extracted pixel region is adjusted is output to the screen display unit. An automatic exposure control method of a digital camera including a process of controlling transmittance is provided.

In the above-described automatic exposure control method of the digital camera, when the automatic exposure control function is selected by the user while the camera image data is output to the screen display due to entering the shooting mode, a pixel to be controlled in the camera image Providing a cursor and / or button input function to enable selection of an area and a transmittance adjustment level; When the pixel area and the transmittance adjustment level to adjust the exposure are selected by the user, camera image data whose illumination is adjusted according to the selected pixel area and the transmittance adjustment level information is output to the screen display unit. And varying the arrangement of the liquid crystal molecules with respect to the cell region of the corresponding liquid crystal filter to control the transmittance of the optical signal passing through the cell region.

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

In the present invention, by adding a liquid crystal filter to the front and rear of the lens of the digital camera, and controlling the contrast of the liquid crystal filter to implement the automatic exposure function by adjusting the amount of light input through the lens, the digital camera for this purpose is attached One drawing has the configuration as shown in FIG.

That is, as shown in FIG. 1, the automatic exposure control apparatus of the digital camera according to the present invention includes a lens unit 11, an optical filter unit 12, a photoelectric conversion unit 13, and a liquid crystal filter unit 14. ) And a liquid crystal drive unit 15 and a control unit 16.

The lens unit 11 includes a lens and a lens holder, and serves to receive an optical signal (light) for a subject and a background, and an optical low pass filter unit 12 controls the lens unit 11. It blocks the optical noise and infrared component of the optical signal.

The photoelectric conversion unit 13 is implemented as an image pickup device of a charge-coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) method, and converts an optical signal passing through the optical filter unit 12 into an electrical signal to have a predetermined size. The pixel array signal is transmitted to the controller 16.

The liquid crystal filter unit 14 is a filter in which a liquid crystal, which is an intermediate material between a solid and a liquid, is injected between glass plates and implemented in the form of a plurality of cells. As shown in (a) of FIG. 2, the lens 11-1 and the lens holder ( 11-2) is formed between the rear end of the lens unit 11, that is, between the lens unit 11 and the optical filter unit 12 to be built into the camera module, or as shown in Figure 2 (b) The lens 11-1 and the lens holder 11-2 may be configured at the front of the lens unit 11 to be implemented outside the camera module, and according to the arrangement change of the liquid crystal molecules for each cell. 13) serves to adjust the transmittance of light, which is an optical signal input to each cell.

The liquid crystal drive unit 15 changes the arrangement of liquid crystal molecules for each cell injected between the glass plates by adjusting the voltage difference between the electrodes of the upper and lower glass plates constituting the liquid crystal filter unit 14, thereby changing the liquid crystal filter unit 14. It controls the transmittance of light passing through each cell of).

The controller 16 performs various digital signal processing including compression / expansion on the camera image signal, which is a pixel array signal transmitted from the photoelectric conversion unit 13, to generate camera image data classified into luminance and chroma signals. It performs a series of image codec processing that outputs it to the screen display, and when the automatic exposure control mode is set, it analyzes digitally processed camera image data by software to measure illuminance (brightness) for each pixel and then set the predetermined illuminance. After extracting the pixel region measured above the level value, the electrode for each corresponding cell of the liquid crystal drive unit 15 to adjust the transmittance of light passing through each cell of the liquid crystal filter unit 14 corresponding to the extracted pixel region. To control the voltage difference.

The controller 16 may further include a pixel area selected to adjust exposure in the camera image output to the screen display when the automatic exposure control function is selected by the user while the digital image processed camera image data is output to the screen display; In order to adjust the transmittance of light passing through the corresponding cells of the liquid crystal filter unit 14 according to the transmittance adjustment level information, the voltage difference of the electrode of the corresponding cells of the liquid crystal driver 15 is controlled.

The automatic exposure control operation of the digital camera based on such a configuration will be described with reference to FIG. 3 as follows.

First, when the digital camera enters the shooting mode after initialization of the digital camera (step S30), an optical signal for a subject and a background to be photographed is input through the lens unit 11, and the input optical signal is an optical filter. The optical noise and infrared components are removed by the unit 12 and then input to the photoelectric conversion unit 13 (step S31).

Thereafter, when the photoelectric conversion unit 13 converts the optical signal input through the optical filter unit 12 into an electrical signal and transmits a camera image signal, which is a pixel array signal of a predetermined size, to the control unit 16 (step S32). ), The controller 16 performs a variety of digital signal processing including compression / expansion by performing a series of image codec processing on a camera image signal which is a pixel array signal to generate camera image data classified into luminance and chroma signal. After that, it is outputted to the screen display unit (step S33).

In the state where the camera image data is output to the screen display unit as described above, the controller 16 checks whether the automatic exposure control mode is set (step S34), and when the automatic exposure control mode is set, the camera image data processed digitally. Is analyzed by software to measure illuminance (brightness) for each pixel, and then it is checked whether there is a pixel area whose illuminance is measured above a predetermined illuminance level value (step S35).

At this time, if there is a pixel area whose illuminance is measured above a predetermined illuminance level value, the pixel area is extracted, and then the transmittance of light passing through each cell of the liquid crystal filter unit 14 corresponding to the extracted pixel area is adjusted. To control the voltage difference of the electrode for each corresponding cell region of the liquid crystal driver 15, the liquid crystal driver 15 controls the upper and lower glass plates constituting the liquid crystal filter unit 14 under the control of the controller 16. By adjusting the voltage difference of the electrode with respect to the corresponding cell region of, the arrangement of liquid crystal molecules with respect to the corresponding cell region of the liquid crystal filter unit 14 is changed to adjust the transmittance of the optical signal passing through the cell region ( Step S36).

The transmittance of the optical signal with respect to some cell regions (ie, cell regions corresponding to pixel regions in which illuminance is measured above a predetermined illuminance level value) of the liquid crystal filter unit 14 formed at the front or rear end of the lens unit 11 as described above. After the adjustment is performed, the optical signal in which the amount of light with respect to the optical signal in some cell areas is adjusted through the lens unit 11 and the optical filter unit 12 is similar to the operation of the camera module when entering the shooting mode. When the optical signal is converted into the electrical signal by the photoelectric conversion unit 13 and the pixel array signal having a predetermined size is transferred to the control unit 16, the control unit 16 receives a camera image that is a pixel array signal. By performing a series of image codec processing on the signal, the camera image data in which the illuminance of the pixel area in which illuminance was measured above the preset illuminance level value is adjusted is generated to display the screen. On is output (step S37).

Subsequently, when the user presses the camera shutter while the camera image data in which the illuminance of some pixel areas is adjusted is displayed on the screen display unit according to the above-described automatic exposure control operation, the controller 16 controls the camera image data in which the automatic exposure is adjusted. Is captured and stored in the memory, thereby completing a series of photographing operations (step S38).

On the other hand, when the automatic exposure control mode is not set in step S34, or when there is no pixel area whose illuminance is measured above the predetermined illuminance level value in step S35, a general camera photographing operation is performed (step S39).

In the above-described embodiment, when the automatic exposure control mode is set, the camera image data processed by the digital signal is analyzed by software to perform automatic exposure control on a pixel area in which illuminance is measured above a predetermined illuminance level value. Although a series of operations have been described, another embodiment of the present invention may be implemented to perform exposure control on an arbitrary pixel area selected by a user. FIG. The following description is made with reference to 4.

First, when the digital camera enters the shooting mode after the initialization of the digital camera (step S40), an optical signal for a subject and a background to be photographed is input through the lens unit 11, and the optical signal thus input is an optical filter. The optical noise and infrared components are removed by the unit 12 and then input to the photoelectric conversion unit 13 (step S41).

Subsequently, when the photoelectric conversion unit 13 converts the optical signal input through the optical filter unit 12 into an electrical signal and transfers a camera image signal, which is a pixel array signal of a predetermined size, to the control unit 16 (step S42). ), The controller 16 performs various digital signal processing including compression / expansion by performing a series of image codec processing on the camera image signal which is a pixel array signal to generate camera image data classified into luminance and chroma signal. This is then output to the screen display (step S43).

In such a state that the camera image data is output to the screen display unit, the controller 16 checks whether the automatic exposure control function is selected by the user (step S44).

In this case, when the automatic exposure control function is selected by the user, the controller 16 provides a cursor and / or button input function to select a pixel area and a transmittance adjustment level to adjust the exposure in the camera image output on the screen display unit. After that, when the pixel region and the transmittance adjustment level to adjust the exposure are selected by the user (step S45), the light passing through each corresponding cell of the liquid crystal filter unit 14 according to the selected pixel region and the transmittance adjustment level is selected. In order to adjust the transmittance, the voltage difference of the electrode for each corresponding cell region of the liquid crystal driver 15 is controlled. The liquid crystal driver 15 configures the liquid crystal filter unit 14 under the control of the controller 16. By adjusting the voltage difference of the electrode with respect to the corresponding cell region of the upper and lower glass plates, the arrangement of liquid crystal molecules with respect to the corresponding cell region of the liquid crystal filter unit 14 is changed to The transmittance of the optical signal passing through the cell region is adjusted (step S46).

The transmittance of the scientific signal with respect to a part of the cell region of the liquid crystal filter unit 14 formed at the front end or the rear end of the lens unit 11 (that is, the cell region corresponding to the pixel region whose illuminance is measured above a predetermined illuminance level value). After the adjustment is performed, the optical signal of some cell regions (cell regions corresponding to the pixel regions selected for exposure control) through the lens unit 11 and the optical filter unit 12 similarly to the operation of the camera module when entering the shooting mode described above. The optical signal of which the amount of light is controlled is input to the photoelectric conversion unit 13, and the optical signal is converted into an electrical signal by the photoelectric conversion unit 13 to transmit a pixel array signal having a predetermined size to the control unit 16. Then, the controller 16 performs a series of image codec processing on the camera image signal which is a pixel array signal, thereby adjusting the illumination of the pixel area selected by the user for the exposure control. To generate data, and outputs to the screen display (step S47).

Subsequently, when the user presses the camera shutter while the camera image data in which the illuminance of some pixel areas is adjusted is displayed on the screen display unit according to the above-described automatic exposure control operation, the controller 16 controls the camera image data in which the automatic exposure is adjusted. By capturing the data and storing it in the memory, a series of shooting operations are completed (step S48).

On the other hand, when the automatic exposure control function is not selected in step S44, a general camera shooting operation is performed (step S49).

For example, in a state in which camera image data generated by processing image codec processing on a camera image signal input through the photoelectric conversion unit 13 is output on the screen display unit, a specific portion of the camera image is so bright that the subject and the background are displayed. If the overall brightness of the image including the dark appears, the control of the voltage difference of the electrode for each cell region of the liquid crystal driver 15 controls the cell region of the liquid crystal filter unit 14 corresponding to the pixel region including the specific part. By lowering the transmittance of the light passing through the brightness of the entire image including the subject and the background can be brightly adjusted. In addition, even when the user does not want to capture a specific portion of the camera image output on the screen display or wants to capture a flow, the liquid crystal filter corresponding to the pixel region including the specific portion by controlling the liquid crystal driver 15 as described above. By controlling the transmittance of light passing through the cell region of the unit 14, it is possible to capture a desired image.

In addition, the embodiment according to the present invention is not limited to the above, and various alternatives, modifications and changes can be made within the scope apparent to those skilled in the art in connection with the present invention, for example In the above-described embodiment, the image codec function is described as being implemented in the control unit. However, in another embodiment of the present invention, the control unit and the image codec unit may be separately implemented. In this case, the image codec unit performs the image codec function performed by the controller.

As described above, the present invention enables the transmittance of the optical signal input through the lens by inserting a liquid crystal filter into the optical signal input terminal of the digital camera, for example, the front and rear of the camera lens, so that the desired pixel area of the camera image can be adjusted. The exposure can be automatically adjusted, and by applying the optical control method using the liquid crystal filter, the use efficiency of the camera can be maximized, such that exposure can be controlled without deterioration and noise generation.

Claims (5)

A lens unit receiving an optical signal for a subject and a background, an optical filter unit for blocking optical noise and infrared components of the optical signal input through the lens unit, and converting an optical signal passing through the optical filter unit into an electrical signal In the digital camera comprising a photoelectric conversion unit for transmitting a pixel array signal of a predetermined size, A filter implemented by injecting liquid crystal between glass plates into a plurality of cell shapes, the filter comprising: a liquid crystal filter unit configured to adjust transmittance of an optical signal input to the photoelectric conversion unit for each cell; By adjusting the voltage difference of the electrode for each cell of the upper and lower glass plates constituting the liquid crystal filter unit, by changing the arrangement of the liquid crystal molecules for each cell injected between the glass plates, the transmittance of light passing through each cell of the liquid crystal filter unit A liquid crystal drive unit for controlling; Perform a digital signal processing on the camera image signal, which is a pixel array signal transmitted from the photoelectric conversion unit, to generate camera image data and then output a series of image codecs to the screen display, but the automatic exposure control mode is set. When the camera image data is analyzed by software, each cell corresponding to the liquid crystal driver to adjust the transmittance of an optical signal passing through each cell of the liquid crystal filter corresponding to the pixel area having a luminance equal to or greater than a predetermined illuminance level value. Automatic control device for a digital camera comprising a control unit for controlling the voltage difference of the electrode with respect to. The method of claim 1, The liquid crystal filter unit may be implemented between the lens unit and the optical filter unit to be embedded in the camera module, or may be configured at the front end of the lens unit and implemented outside the camera module. Device. The method of claim 1, The controller may be configured to display pixel area and transmittance adjustment level information selected to control exposure in the camera image output to the screen display unit when the automatic exposure control function is selected by the user while the camera image data is output to the screen display unit. And controlling the voltage difference adjustment of the electrode for each corresponding cell of the liquid crystal driver to adjust the transmittance of the optical signal passing through each corresponding cell of the liquid crystal filter unit. Converting an optical signal of a subject and a background input through the lens unit into a pixel array signal having a predetermined size as an electric signal when entering the shooting mode, and outputting camera image data generated by performing image codec processing on a screen display unit; ;  If the automatic exposure control mode is set, analyzing the camera image data by software to measure illuminance for each pixel, and extracting a pixel region in which illuminance is measured above a predetermined illuminance level value; The arrangement of the liquid crystal molecules with respect to the cell region of the liquid crystal filter corresponding to the pixel region is outputted so that the camera image data of which the illumination intensity of the extracted pixel region is adjusted is output to the screen display unit. Automatic exposure control method of a digital camera comprising the step of controlling the transmittance. The method of claim 4, wherein When the camera exposure data is output to the screen display due to entering the shooting mode, when the automatic exposure control function is selected by the user, a cursor to select the pixel area and the transmittance adjustment level to adjust the exposure in the camera image; / Or providing a button input function; When the pixel area and the transmittance adjustment level to adjust the exposure are selected by the user, the image area corresponding to the pixel area and the transmittance adjustment level corresponding to the pixel area are output to the screen display unit. And varying the arrangement of liquid crystal molecules with respect to the cell region of the liquid crystal filter to control the transmittance of the optical signal passing through the cell region.

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