KR20090071325A - Photographing apparatus - Google Patents

Abstract

A photographing apparatus is provided to control light against backlight and automatically put lights on a subject while taking a motion picture. An image pickup device detects a reflected light intensity of a subject. A photometry unit(112) detects a brightness level of a subject according to the reflected light detected by the image pickup device. A backlight determination unit determines a backlight status based on the brightness level of the subject. A lighting control unit(122) irradiates light on the subject by controlling a light emitting unit.

Description

Imaging Apparatus {Photographing apparatus}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup device, and more particularly, to an image pickup device that can control illumination according to a backlight condition when capturing a moving picture and correct a dark portion generated in the moving picture.

In recent years, with the rapid development of digital device manufacturing technology and information processing technology, various digital devices are widely spread so that high-performance digital devices at low prices can be easily obtained. Among them, the digital still camera is one of the digital devices widely used. A digital device (hereinafter, an imaging device) equipped with an imaging function such as a digital still camera may be equipped with a flash as an illuminating means for illuminating a subject. In addition, recently, the imaging apparatus is equipped with a video shooting function for shooting a video.

Since the lighting means such as a flash mounted on such an imaging device is a large amount of light and is not a means for continuously illuminating a subject, there is a problem that it is not suitable for video shooting. Therefore, research and development are being conducted on the lighting means and the control means that can emit light continuously during video shooting. As the lighting means, for example, a light emitting diode (LED) or the like capable of illuminating a subject over a plurality of frames of a moving image has been noted. LEDs are characterized by high brightness and low power consumption. However, even when using the LED as a lighting means, there is a disadvantage that a large amount of power is still consumed. Therefore, the technique of reducing the power consumption of an imaging device is also attracting attention by controlling the lighting / lighting off of a lighting means suitably.

Regarding such a technique, for example, Japanese Patent Laid-Open No. 2003-309765 describes a technique relating to a mobile phone equipped with an imaging device and a camera. This technique is characterized in that the lighting means is turned on in accordance with the operation of the operation key by the user with respect to the lighting of the lighting means for illuminating the subject. The document also describes a technique for turning off the lighting means after the lighting means is turned on but before the camera automatically raises the exposure.

As another example, Japanese Patent Laid-Open No. 2003-348440 describes a technique relating to a control method of an imaging device using a lighting device. This technique is characterized in that a user using an imaging device selects and operates an operation button to control the operation of the imaging device, the display device, and the lighting device. In particular, when the operation button is operated, the operation of the imaging device and the lighting of the lighting device are controlled. In addition, according to the literature, users need to judge the necessity of lighting control themselves.

As another example, Japanese Patent Laid-Open No. 2005-165204 describes a technique related to a photographing lighting device, a camera system, and a camera. This technique relates to a method of controlling a current controlled light emitting means that emits irradiated light toward a subject, and detects distance information to a main subject, and calculates the amount of light calculated based on the distance information, exposure time, aperture value, and shooting sensitivity. There is a feature in that the light emitting means is controlled to emit light. The document also describes a technique for controlling the drive current supplied to the light emitting means.

However, even when using the techniques described in the above-mentioned Patent Publication Nos. 2003-309765 and 2003-348440, it is necessary to determine whether the flash is turned on or off by the user's sense and to switch the lighting on / off by manual operation. It is difficult to control the lighting of the illumination light only in the situation where the illumination is necessary. In particular, it is impossible to control such that the illumination light is automatically irradiated by detecting a backlight state during video shooting. In addition, although the technique described in Japanese Patent Laid-Open No. 2005-165204 can control the amount of light in consideration of the distance to the main subject, it does not consider controlling the light emission of the illumination light by detecting a backlight state during video shooting. Therefore, even in combination with the above-described techniques, it is difficult to control the lighting means to be suitable for video shooting, and furthermore, there is a problem that it is not easy to correct the dark part of the video generated by the backlight using the illumination light.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image capturing apparatus that enables excellent shooting by appropriately illuminating a subject when shooting a moving picture.

Another object of the present invention is to provide an image capturing apparatus capable of automatically illuminating a subject when a dark part of illumination occurs when capturing a moving image.

Still another object of the present invention is to provide an image capturing apparatus capable of controlling illumination according to a backlight condition when capturing a moving image and correcting a dark portion generated in the moving image.

The present invention provides an imaging device capable of detecting a luminance level of a subject according to the reflected light intensity detected by the imaging element, and correcting back light based on the luminance level.

An imaging device according to the present invention includes an imaging device for detecting the reflected light intensity of a subject, a light emitting unit capable of emitting light toward the subject while the reflected light intensity is continuously detected by the imaging device a plurality of times, and detected by the imaging device. A metering unit for detecting the luminance level of the subject according to the reflected light intensity, a backlight determining unit for determining the backlight state based on the luminance level of the subject, and a light emitting unit for controlling the light emitting unit when the backlight unit determines the backlight state. A light emission control part for irradiating light is provided.

The illumination light irradiated by the light emitter may be pulse light that periodically blinks. In the case where the illumination light is pulsed light, pulsed light may be continuously irradiated while the reflected light intensity is detected several times in succession by the imaging device.

In the present invention, the backlight determining unit may set some of the pixels included in the image pickup device as the region of interest, and compares the luminance levels of the pixels of the region of interest with the luminance levels of the pixels in the background region other than the region of interest. Can be determined.

In the present invention, the backlight determining unit calculates a center metering value obtained by averaging luminance level values of pixels in a region of interest, calculates a background metering value averaged of luminance level values of pixels in a background region, and then calculates The backlight metering state can be determined by comparing the background metering values.

In the present invention, the backlight determining unit calculates a median average metering value by averaging a plurality of center metering values corresponding to a plurality of synchronization signals sequentially generated to read reflected light intensities of the pixels of the image pickup device, and performs background metering. After averaging the values to calculate the background average metering value, the backlighting state may be determined by comparing the median average metering value with the background average metering value.

In the present invention, the region of interest may be set to an area corresponding to the dark portion of the subject as a result of the detection of the photometer.

In the present invention, the light emission control portion can control the light amount of the light emitting portion, and until the luminance level detected by the light metering portion reaches a predetermined value or reaches the maximum light amount irradiated by the light emitting portion, The light emission control unit may increase the amount of light irradiated by the light emitting unit stepwise in synchronization with a synchronization signal for reading the reflected light intensity.

In the present invention, the imaging device includes a first luminance level detected when the light emitting unit is irradiated with the first light amount, a second luminance level detected when the second light amount is smaller than the first light amount, and the first luminance level. The apparatus may further include a luminance comparator configured to compare the third luminance level detected when irradiated with a third amount of light greater than the amount of light, and the light emission controller may further include a third luminance level ≤ first luminance level or a first result. In the case of the first luminance level ≤ the second luminance level, the illumination by the light emitting portion can be stopped or the amount of light can be reduced.

In the present invention, the luminance comparator may compare the first luminance level and the second luminance level detected within the predetermined time difference or the first luminance level and the third luminance level detected within the predetermined time difference.

In the present invention, the light emission controller may control the light emission unit in synchronization with a synchronization signal for reading the reflected light intensity of the pixels of the image pickup device.

In the present invention, the light emission control unit may control the light emission unit in synchronization with each of the sequentially generated synchronization signals for reading the reflected light intensity of the pixels of the image pickup device.

In the present invention, the imaging device compares the luminance level when the maximum light is emitted while the emission portion emits light in response to the synchronization signals, and the luminance level when the minimum light is emitted, and emits the light emitting portion to back light the state. It may further include an illumination determination unit for determining whether can be corrected.

As described above, the image pickup apparatus of the present invention may correct the dark portion generated in the moving image by controlling the illumination according to the backlight state when the moving image is captured.

EMBODIMENT OF THE INVENTION Hereinafter, the structure and operation | movement of the imaging device which concerns on this invention are described in detail through embodiment of an accompanying drawing.

According to an embodiment of the present invention, the backlight may be determined during video recording, and the backlight may be corrected to correct the dark part of the video during the backlighting. Backlighting refers to the rays of light behind a subject, or the effects of these rays on photography.

■ Functional configuration of the imaging device 100

1 is a block diagram showing a functional configuration of an imaging device 100 according to an embodiment of the present invention. Hereinafter, with reference to FIG. 1, the functional structure of the imaging device 100 which concerns on this embodiment is demonstrated.

As shown in FIG. 1, the imaging device 100 mainly includes a CCD (charge coupled device) 102, a CDS / AMP unit 104, an A / D conversion unit 106, and an image signal generation unit 108. ), Bus 110, light metering unit 112, image signal processing unit 114, recording medium control unit 116, recording medium 118, timing generating unit 120, and light emission control unit ( 122, light source 124, central processing unit (CPU) 126, shutter 128, memory 132, compression processing unit 134, video encoder 136, image display unit 138 ).

○ CCD (102)

The CCD 102 is formed by a plurality of photoelectric conversion elements that convert incident light into an electrical signal. For example, when the CCD 102 receives light incident through the imaging optical system, each element included in the CCD 102 outputs an electric signal according to the light receiving intensity. CCD 102 is an example of an imaging element, and the present invention is not limited thereto. In other words, the imaging device 100 may include other imaging devices, such as a complementary metal oxide semiconductor (CMOS), in addition to the CCD 102.

FIG. 2 is an explanatory diagram showing an example of the divisional configuration of an image region of the imaging device included in the imaging device of FIG. 1.

As shown in FIG. 2, the CCD 102 has an imaging surface divided into a plurality of image regions. In the example of FIG. 2, the imaging plane is divided into 64 image areas. For convenience of explanation, numbers of 0 to 63 are assigned to each image area. In the following description, the i-th image region is sometimes called 'region i'.

In addition, the CCD 102 may have a 'notice area' as shown by a thick line in FIG. 2. The region of interest may be provided in the central portion of the CCD 102 or may be provided in another portion. For example, when the imaging apparatus 100 has a function of detecting a characteristic portion of the subject, the region of interest may be the characteristic portion. The region of interest may also be set as an area determined to correspond to a dark portion in relation to the subject and the background. That is, as a result of light metering, when light is present behind the subject, when a part of the subject is dark, the dark portion of the subject can be set as the region of interest and the light can be corrected for the set region of interest.

In the example of FIG. 2, the region of interest is set as regions 27, 28, 35, and 36 separated by thick lines. In the following description, it is assumed that the region of interest is set in the center portion of the CCD 102. The electrical signal output from each image area of the CCD 102 is input to the CDS / AMP unit 104. However, the present invention is not limited to the region of interest set as described above. In other words, by setting the region of interest to the region determined as the dark portion as a result of the photometry, the backlight correction process for the dark portion can be performed.

○ CDS / AMP part (104)

The CDS / AMP unit 104 of FIG. 1 is composed of a correlated double sampling (CDS) circuit and an amplifier (AMP). The CDS / AMP unit 104 functions to remove low frequency noise components of the electrical signal input from the CCD 102 and to amplify the electrical signals from which the low frequency noise components have been removed to a predetermined level. The electrical signal input by the CDS / AMP unit 104 is input to the A / D conversion unit 106.

○ A / D conversion part 106

The A / D converter 106 is an example of an analog-digital converter that converts an analog signal into a digital signal. The A / D converter 106 converts the electrical signal input by the CDS / AMP unit 104 into a digital signal. The digital signal converted by the A / D converter 106 is input to the image signal generator 108.

○ image signal generator 108

The image signal generation unit 108 functions to generate an image signal from the digital signal converted by the A / D conversion unit 106. The image signal generation unit 108 converts the digital signal input by the A / D conversion unit 106 into a signal (hereinafter, referred to as an image signal) in a format capable of image processing and outputs it. The image signal output by the image signal generation unit 108 is input to the image signal processing unit 114.

○ Bus (110)

The bus 110 is a signal transmission path and means for connecting each component of the imaging device 100. The bus 110 may be, for example, an image signal generation unit 108, a light metering unit 112, an image signal processing unit 114, a recording medium control unit 116, a timing generation unit 120, a CPU 126, The table storage unit 130, the memory 132, the compression processor 134, and the video encoder 136 may be connected to each other, and may transmit a signal from one component to another component.

○ Metering section (112)

The photometric portion 112 is a means for measuring the luminance level (hereinafter sometimes referred to as a luminance signal) of each image region included in the CCD 102. The luminance level is measured based on the electrical signal output from each image area. In addition, the metering unit 112 may calculate a luminance level by assigning a weight to each color of the electrical signal output from each image area. To this end, the light metering portion 112 may be implemented as shown in FIG. 3.

FIG. 3 is an explanatory diagram showing a configuration example of a light metering portion of the imaging device of FIG. 1.

As shown in FIG. 3, the light metering portion 112 includes a plurality of multipliers 1122, 1124, and 1126, an adder 1128, and an accumulator 1130. The multiplier 1122 multiplies the signal intensity R output from the red (R) pixel by the weight coefficient Cr (= 0.3) and inputs it to the adder 1128. The multiplier 1124 multiplies the signal intensity G output from the green G pixel by the weighting factor Cg (= 0.6) and inputs it to the adder 1128. The multiplier 1126 multiplies the signal intensity B output from the blue (B) pixel by the weighting factor Cb (= 0.1) and inputs it to the adder 1128.

The adder 1128 adds the weighted signal intensities inputted from the multipliers 1122, 1124, and 1126 to calculate the luminance signal Y, and inputs the same to the adder 1130. The integrator 1130 integrates the luminance signal Y input from the adder 1128 with respect to some or all of the image regions, and outputs luminance levels with respect to some or all of the image regions. That is, the photometric unit 112 calculates the luminance signal Y for each image area according to Equation 1. For example, the light metering unit 112 may calculate the luminance level of the region of interest and the luminance level of a region other than the region of interest (hereinafter, referred to as a residual region).

Y = Cr * R + Cg * G + Cb * B

○ Image signal processor 114

The image signal processing unit 114 of FIG. 1 is a means for synthesizing image signals for each image region input by the image signal generation unit 108 to generate image data. Image data generated by the image signal processing unit 114 may be stored in the memory 132. The image signal processing unit 114 may also generate moving image data using frames of image data accumulated in the memory 132. In this case, the image signal processing unit 114 cooperates with components such as the compression processing unit 134 and the video encoder 136 to generate moving picture data.

○ recording medium control unit 116 / recording medium 118

The recording medium control unit 116 functions to write data on the recording medium 118 or to read data recorded on the recording medium 118. The recording medium 118 is a means for recording data. For example, the recording medium 118 may be a storage device built into the imaging device 100 or a removable recording medium that can be separated from the imaging device 100. The recording medium 118 is a storage means such as an optical recording medium (CD, DVD, etc.), an optical magnetic storage medium, a magnetic storage medium, or a semiconductor storage medium.

○ Timing Generator 120

The timing generator 120 is a means for controlling the exposure period and charge reading timing of each pixel of the CCD 102 and controlling the noise reduction circuit by the CDS / AMP unit 104. To this end, the timing generator 120 inputs a timing signal to each of the CCD 102 and the CDS / AMP unit 104. In addition, the timing generator 120 inputs a synchronization signal to the light emission controller 122 when the charge is read from the CCD 102.

○ Light emission control part 122 / light source 124

The light emission controller 122 is a means for controlling the operation (on / off) of the light source 124 and the amount of light of the illumination light emitted from the light source 124. The light emission controller 122 can cause the light source 124 to emit light when it is determined that the backlight is in the backlight state by the backlight determination function of the CPU 126 described later.

When the light emission control unit 122 emits the light source 124, the light emission control unit until the luminance level detected by the light metering unit 112 reaches a predetermined value or reaches the maximum amount of light that can be irradiated by the light source 124. 122 may gradually increase the amount of light. However, the light emission controller 122 incrementally increases the light amount in synchronization with the synchronization signal input by the timing generator 120. The sync signal may be a vertical sync signal.

In addition, the light emission controller 122 may control the amount of light of the light source 124 according to the determination result by the illumination determination function of the CPU 126 described later. In addition, the light emission control unit 122 may cause the light source 124 to emit light with the amount of light calculated by the illumination light amount calculation function of the CPU 126 described later.

On the other hand, the light source 124 is an example of the light emitting unit as a means for illuminating the subject when a still image or a moving image is taken. The light source 124 may include, for example, a plurality of light emitting sources that emit light such as red, green, and blue. As such, the light source 124 may be configured by a combination of a plurality of light emitting sources having different luminance, color, or the like, or may include a white light source and a color filter of one color. The light source 124 may be implemented by, for example, a light emitting device such as an LED.

4 is a schematic circuit diagram illustrating an example of a light emission controller of the imaging device of FIG. 1. A circuit configuration of the light emission controller 122 that controls the light source 124 will be described with reference to FIG. 4.

As shown in FIG. 4, the light emission controller 122 includes a power supply terminal 1222, a synchronization signal input terminal 1224, a control signal input terminal 1226, a synchronization circuit 1228, and a current limiting circuit 1230. ) And a ground terminal 1232. The light source 124 is connected between the power supply terminal 1222 and the current limiting circuit 1230. Power is supplied to the power supply terminal 1222. The control signal is input to the control signal input terminal 1226 from the CPU 126. The ground terminal 1232 is grounded.

One end of the light source 124 is connected to a power supply terminal 1222, and power is supplied from the power supply terminal 1222. The other end of the light source 124 is connected to a current limiting circuit 1230, and the amount of current is limited by the current limiting circuit 1230. A synchronous circuit 1228 is connected to the current limiting circuit 1230, and the amount of current flowing in accordance with the control signal input from the synchronous circuit 1228 is controlled. The current limiting circuit 1230 is also connected to the ground terminal 1232.

FIG. 5 is a graph showing the relationship between the output intensity of the control signal of the light emission control unit of FIG. 4 and the light emission amount. Specifically, FIG. 5 shows the relationship between the control signal input to the current limiting circuit 1230 and the light emission amount of the light source 124.

As shown in FIG. 5, when the intensity of the control signal (DA output) input to the current limiting circuit 1230 exceeds a predetermined value, the light emission amount of the light source 124 increases linearly. As shown in FIG. 4, since the current limiting circuit 1230 and the light source 124 are connected in series, the light emission amount of the light source 124 may be controlled by a control signal input from the synchronization circuit 1228.

4, one end of the synchronization circuit 1228 is connected to the current limiting circuit 1230, and the other end is connected to the control signal input terminal 1226. The synchronizing circuit 1228 also receives a vertical synchronizing signal from the synchronizing signal input terminal 1224. This vertical synchronizing signal is a vertical synchronizing signal input from the timing generator 120. The synchronizing circuit 1228 inputs the control signal input from the CPU 126 to the current limiting circuit 1230 in synchronization with the vertical synchronizing signal input from the timing generating unit 120.

FIG. 6 is an explanatory diagram showing a signal synchronization method by the synchronization circuit 1228 of the light emission controller of FIG. 4. 6 shows a vertical synchronizing signal input from the timing generating unit 120, a control signal input from the CPU 126, and a control signal after synchronizing by the synchronizing circuit 1228.

As shown in Fig. 6, in general, the control signal input from the CPU 126 is not synchronized with the vertical synchronization signal when the timing at which its intensity changes. This vertical synchronizing signal shows the timing of reading charges from the top of the CCD 102 down. Therefore, when the amount of illumination light changes between the read start positions A, the luminance level of a part of the image changes in accordance with the change of the amount of illumination light. For example, only about the bottom half of the image can be a bright image. Therefore, it is necessary to synchronize the light amount change timing of the control signal input from the CPU 126 with the charge read timing of the vertical synchronization signal. Therefore, the synchronization circuit 1228 synchronizes the light amount change timing of the control signal with the vertical synchronization signal, and inputs the control signal after synchronization shown in FIG. 6 to the current limiting circuit 1230.

○ CPU (126)

As an example of a controller included in the imaging apparatus 100, the CPU 126 is connected to various components of the imaging apparatus 100 to perform a function of controlling an operation. However, the present invention is not limited thereto, and the control unit of the imaging apparatus 100 may be a circuit board including a semiconductor chip in addition to the CPU 126, or may be software embedded in the circuit board or the semiconductor chip.

The CPU 126 is a central processing means, and controls or calculates each component of the imaging apparatus 100 based on a control program, a processing program, or the like stored in a predetermined storage means (memory 132, the recording medium 118, etc.). Processing and the like can be executed. For example, the CPU 126 may control the operation of the imaging optical system by inputting a control signal to a driving means (not shown) for focus control or exposure control. In addition, the CPU 126 can control each component of the imaging device 100 in accordance with a user operation by an operation means (not shown) such as a shutter 128 or an adjusting dial. Further, the CPU 126 can perform the backlight determination function, the illumination determination function, and the illumination light quantity calculation function based on the program recorded in the predetermined storage means.

○ shutter (128)

The shutter 128 is an input means for allowing a user to notify the imaging device 100 of the shooting timing. The shutter 128 is an example of a user's operation interface. The operation by the shutter 128 is transmitted to the CPU 126, for example.

○ Memory (132)

The memory 132 is a storage means for storing a control program and a processing program for defining the operation of the CPU 126, or used as a cache memory during the calculation processing by the CPU 126. In addition, the memory 132 may store an image signal generated by the image signal generator 108, image data generated by the image signal processor 114, and the like. Furthermore, when a moving picture is taken, a moving picture frame (image data) shot by time division is temporarily stored in the memory 132, and moving picture data generated by the image signal processing unit 114 is stored based on the moving picture frame. do. The memory 132 may be implemented by a semiconductor memory device such as, for example, synchronous DRAM (SDRAM).

In addition, the memory 132 may be implemented as a ring buffer (circular buffer). The ring buffer is a data memory in which a plurality of data storage areas are formed in a ring shape. For example, the number (buffer number) of the entire data storage area is BF, and the buffering number n is distributed in order for each data storage area. Data is stored in the ring buffer in order according to the buffering number n. However, the data storage area in which data is stored after the buffering number n = BF returns to the first buffering number n = 0. In other words, the ring buffer has a ring shape, and after reaching the last data storage area, the old buffer is overwritten with old data.

○ Compression Processing Unit (134)

The compression processing unit 134 is a means for compressing the size of the data by encoding the image data or the video data. The compression processing unit 134 compresses the image data or moving image data read out from the memory 132 or the image data or moving image data input by the image signal processing unit 114. When image data is input, the compression processing unit 134 compresses the image data in a compression format such as JPEG or LZW, for example. In addition, when moving picture data is input, the compression processing unit 134 compresses the moving picture data by, for example, encoding each moving picture frame and performing differential encoding between the moving picture frames.

○ video encoder 136 / image display unit 138

The video encoder 136 is a means for converting the input image data into a format for outputting to the image display unit 138. The video encoder 136 records, for example, live view image data recorded in a memory 132, a video memory (VRAM) (not shown), image data of various setting screens, a recording medium 118, or the like. The converted image data and the like can be read out and converted. The image data input by the video encoder 136 is input to the image display unit 138. The image display unit 138 is a means for displaying image data input from the video encoder 136. The image display unit 138 may include a display device such as a liquid crystal display (LCD) or an electro luminescence display (ELD), for example.

■ video backlight correction processing

FIG. 7 is a flowchart illustrating a flow of a video backlight correction process performed by the imaging device of FIG. 1.

The video backlight correction process is a process for correcting a dark portion of a video generated by the influence of backlight. This process is a technique of correcting a dark part by irradiating an illumination light to a subject, and in particular, has a characteristic of controlling the lighting timing of the light source 124 by detecting a backlight condition. Hereinafter, the image capturing apparatus 100 including the ring buffer type memory 132 will be described.

As shown in FIG. 7, initially, illumination by the light source 124 of the imaging device 100 is in the state (OFF) (S102). Next, the imaging apparatus 100 sets the buffering number (n = 0), the number of buffers (BF = 10) and the initial value (= 0) of the amount of illumination light (S104). The imaging device 100 integrates the luminance signal Y by the light metering portion 112 (S106). Subsequently, the imaging apparatus 100 sets the buffering number n at the current time point to the current buffering number CN (S108).

Subsequently, the imaging apparatus 100 calculates luminance values of each image region (regions 0 to 63), and arranges the calculated luminance values corresponding to the buffering number n (Y [n] [0] to Y [). n] [63]) in operation S110. Subsequently, the imaging apparatus 100 stores the value of the illumination light amount in the form of an array L [n] corresponding to the buffering number n (S112). Next, the imaging device 100 determines the backlight state by the backlight determination function of the CPU 126 (S114). The backlight determination process will be described later.

Next, the imaging device 100 determines whether the light source 124 should be turned on or off by the illumination determination function of the CPU 126 (S116). This illumination determination process is also mentioned later. If it is determined that the light source 124 is to be turned on, the imaging device 100 proceeds to the processing of step S118. On the other hand, when it is determined that the light source 124 is turned off, the imaging device 100 proceeds to the processing of step S122.

In step S118, the imaging device 100 calculates the illumination light amount by the illumination light amount calculation function of the CPU 126 (S118). Subsequently, the imaging device 100 sets the amount of illumination light, and lights up the light source 124 with the amount of illumination light (S120). On the other hand, in step S122, the imaging device 100 sets the illumination light amount to zero (S122). Next, the imaging device 100 sets the amount of illumination light, and turns off the light source 124 (S124).

In step S126, the imaging apparatus 100 compares the buffering number n with the number of buffers BF and determines whether n <BF corresponds (S126). If n <BF, the imaging device 100 proceeds to step S128. On the other hand, if n <BF, the imaging device 100 proceeds to step S130. In step S128, the imaging device 100 increases the buffering number n by one (n = n + 1, S128). On the other hand, in step S130, the imaging device 100 sets the buffering number n to 0 (n = 0, S130).

Next, the imaging device 100 determines the ON / OFF of the shutter 128 (S132). When the shutter 128 is ON, the imaging device 100 ends the video backlight correction processing (S100). On the other hand, when the shutter 128 is OFF, the imaging device 100 proceeds to the processing of step S106. In addition, the above-described processing takes effect when the shutter 128 is pressed (ON). Until then, the image to be shot (preview image) is displayed.

Hereinafter, the backlight determination process (S114), the illumination determination process (S116), and the illumination light quantity calculation process (S118) of the above-described moving image backlight correction process (S100) will be described in detail. These processes can also be executed by the CPU 126.

■ Backlight Judgment Processing (S114)

8 is a flowchart showing the flow of backlight determination processing performed by the imaging device of FIG. This process can be executed by the backlight determining function of the CPU 126, which is an example of the backlight determining unit of the present invention. The present invention is not limited thereto, and the backlight determining unit may be implemented by a semiconductor chip or a circuit board separately provided.

The median average metering value Ysp and the background average metering value Ybg are expressed by, for example, equations (2) and (3). The median average metering value Ysp is a value obtained by averaging the center metering value YS [n] calculated for the image area included in the region of interest shown in FIG. 2 to all the buffering numbers n of the ring buffer. On the other hand, the background average metering value Ybg is a value obtained by averaging the background metering value YB [n] calculated for the remaining area except for the region of interest shown in FIG. 2 to all the buffering numbers n of the ring buffer. .

Here, the center metering value YS [n] is a metering value Y averaged for all the image areas included in the region of interest for each buffering number n, as represented by equation (4). In addition, the background metering value YB [n] is a metering value Y averaged for all the image areas included in the remaining area except the region of interest for each buffering number n, as represented by Equation 5. .

As shown in FIG. 8, the imaging apparatus 100 compares the background average metering value Ybg and the median average metering value Ysp in step S202 (S202). At this time, the imaging device 100 adds the predetermined backlight determination threshold A to the center average metering value Ysp, and compares the added value Ysp + A with the background average metering value Ybg ( S202). In the case of Ybg> (Ysp + A), the imaging device 100 proceeds to step S204. On the other hand, when Ybg> (Ysp + A), the imaging device 100 proceeds to step S206.

In the above-described example, the imaging apparatus 100 compares the background average metering value Ybg and the median average metering value Ysp to determine the backlight state, but the present invention is not limited thereto. That is, the imaging apparatus 100 may determine the backlight state by comparing the center metering value YS [n] corresponding to one frame with the background metering value YB [n].

In step S204, the imaging apparatus 100 substitutes the value 1 representing the backlight state into the variable Rb indicating the backlight determination result (S204). On the other hand, in step S206, the imaging device 100 substitutes the value 0 representing the pure light state into the variable Rb representing the backlight determination result (S206). In step S208, the imaging device 100 outputs the value of the variable Rb as a result of backlight determination (S208).

As described above, in the backlight determination process S114, when the difference between the center average metering value Ysp and the background average metering value Ybg exceeds the predetermined backlight determination threshold A, it is determined as a backlight condition.

■ Lighting judgment processing (S116)

9 is a flowchart showing a flow of an illumination determination process performed by the imaging device of FIG. 1. This process may be executed by an illumination determination function of the CPU 126, which is an example of the illumination determination unit of the present invention. The present invention is not limited thereto, and the illumination determination unit may be implemented by a semiconductor chip or a circuit board separately provided.

As shown in FIG. 9, the imaging device 100 determines whether the backlight determination result Rb by the backlight determination process S114 is 1 (backlight) (S302). If the backlight determination result is Rb = 1, the imaging device 100 proceeds to step S304. On the other hand, when the backlight determination result is not Rb = 1, the imaging device 100 proceeds to step S316.

In step S304, the imaging device 100 determines whether the illumination light amount buffer L [CN] corresponding to the current buffering number CN is 0 (S304). If the illumination light amount buffer L [CN] = 0, the imaging device 100 proceeds to step S314. On the other hand, when the illumination light amount buffer L [CN] = 0 is not reached, the imaging device 100 proceeds to step S306.

In step S306, the image capturing apparatus 100 performs a background average metering value by adding a backlight determination threshold value A and an illumination determination threshold value A 'to the central average metering value Ysp. In comparison with (Ybg), it is determined whether or not Ybg> (Ysp + A + A ') (S306). If Ybg> (Ysp + A + A '), the imaging device 100 proceeds to step S308. On the other hand, when Ybg> (Ysp + A + A '), the imaging device 100 proceeds to step S316. The illumination determination threshold A 'is a value in consideration of the metering value brightened by illumination.

In step S308, the imaging apparatus 100, with respect to the address * X of the maximum illumination light amount buffer, the address (* max) of the illumination light amount buffer which becomes the maximum value among the illumination light amount buffers L [0] to L [BF]. (L [0-BF]) is substituted (S308). Subsequently, the imaging apparatus 100 has the address * min (L [] of the illumination light amount buffer which becomes the minimum value among the illumination light amount buffers L [0] to L [BF] with respect to the address * N of the minimum illumination light amount buffer. 0 to BF]) (S310). Here, the address means a pointer indicating a buffering number, for example.

Subsequently, the imaging device 100 compares the value of the center average metering value Ysp corresponding to the address (* X) of the maximum illumination light quantity buffer and the address (* N) of the minimum illumination light quantity buffer, and Ysp [* X] It is determined whether > Ysp [* N] + C (S312). Here, the photometric value determination threshold C is a threshold determined for determining the effect by illumination. If Ysp [* X]> Ysp [* N] + C, the imaging device 100 proceeds to step S314. On the other hand, when Ysp [* X]> Ysp [* N] + C, the imaging device 100 proceeds to step S316.

In step S314, the imaging device 100 substitutes the value 1 representing the backlight state into the variable Rl representing the illumination determination result (S314). On the other hand, in step S316, the imaging device 100 substitutes the value 0 representing the pure light state into the variable Rl representing the illumination determination result (S316). In step S314, the imaging device 100 outputs the value of the variable Rl indicating the illumination determination result (S318).

In the above-described flow of illumination determination processing (S116), determination of lighting / off is performed in accordance with the difference between the photometric value when illuminated with the maximum illumination light amount and the photometric value when illuminated with the minimum illumination light amount. This is because when the difference between the metering value when illuminated with the maximum illumination light and the illumination value when illuminated with the minimum illumination light does not exceed the metering value determination threshold C, the effect of illumination is not reflected in the metering value. It is judged that it is not, which corresponds to, for example, the case is lit by disturbance.

■ Illumination light quantity calculation processing (S118)

FIG. 10 is a flowchart showing a flow of light amount calculation processing performed by the imaging device of FIG. 1. This process may be performed by the illumination light amount calculation function of the CPU 126, which is an example of the illumination light amount calculation unit of the present invention. The present invention is not limited thereto, and the illumination light amount calculation unit may be implemented by a semiconductor chip or a circuit board separately provided. have.

As shown in FIG. 10, the imaging apparatus 100 sets the buffering number n to 0 (S402). Subsequently, the imaging apparatus 100 determines whether the illumination light amount buffer L [CN] corresponding to the current buffering number CN is 0 (S404). If the illumination light amount buffer L [CN] = 0, the imaging device 100 proceeds to step S406. On the other hand, if L [CN] = 0, the imaging device 100 proceeds to step S408.

In step S408, the imaging apparatus 100 determines whether the current buffering number CN is zero (S408). In other words, the imaging apparatus 100 determines whether CN-1 <0 (S408). If CN-1 <0, the imaging apparatus 100 proceeds to step S412. On the other hand, when CN-1 <0, the imaging apparatus 100 proceeds to step S410.

In operation S410, the imaging apparatus 100 substitutes the value CN-1 from the current buffering number CN by the variable D in operation S410. On the other hand, in step S412, the imaging apparatus 100 substitutes the value BF-1 subtracting 1 from the number of buffers BF into the variable D (S412). That is, the variable D is a buffering number indicating a data storage area in which data is stored before the current buffering number CN.

In step S414, in relation to the variable LIGHT indicating the amount of illumination light, the imaging device 100 performs a center metering value YS [CN] corresponding to the current buffering number CN and a center metering corresponding to the variable D. FIG. A weighted value YS [CN] -YS [D] * comp) is added to the difference between the values YS [D] and substituted into the variable LIGHT (S414). Herein, the illumination light quantity coefficient comp may be, for example, a predetermined integer value.

Subsequently, the imaging device 100 compares the variable LIGHT indicating the illumination light amount with the upper limit value MAX of the illumination light amount, and determines whether LIGHT> MAX (S416). If LIGHT> MAX, the imaging device 100 proceeds to step S418. On the other hand, if LIGHT> MAX, the imaging device 100 proceeds to step S420.

In step S418, the imaging apparatus 100 substitutes the illumination light quantity upper limit value MAX into a variable LIGHT indicating the illumination light quantity (S418). On the other hand, in step S420, the imaging device 100 compares the variable LIGHT indicating the amount of illumination light with the lower limit MIN of the amount of illumination light and determines whether LIGHT <MIN (S420). If LIGHT <MIN, the imaging device 100 proceeds to step S422. On the other hand, when LIGHT <MIN is not, the imaging device 100 proceeds to step S424.

In step S422, the imaging device 100 substitutes the lower limit value MIN of illumination light amount into a variable LIGHT indicating the illumination light amount (S422). In operation S424, the imaging apparatus 100 outputs a variable LIGHT indicating the amount of illumination light (S424). In addition, the variable LIGHT indicating the illumination light amount corresponds to the DA value of FIG. 5.

According to the above-mentioned illumination light quantity calculation process S118, the illumination light quantity according to the difference of the center metering value adjacent to a ring buffer is set.

As described above, the image capturing apparatus 100 according to the exemplary embodiment of the present invention can correct the backlight of the video by using the illumination light. The functional configuration of the imaging device 100 is summarized as follows.

The imaging device 100 includes a light source 124 that transmits illumination light to a subject as illumination means. The imaging apparatus 100 also includes a photometric portion 112 for measuring the luminance level for each image region of the CCD 102 as photometric means. Furthermore, the imaging device 100 is equipped with the backlight determination function of the CPU 126 which determines the backlight state from the metering value obtained through each image area of the CCD 102 as backlight determination means.

The imaging apparatus 100 also includes an image display section 138 that displays image data corresponding to image signals read out from the CCD 102 at predetermined intervals in synchronization with the vertical synchronization signal.

For example, the imaging device 100 executes the backlight determination function of the CPU 126 while continuously displaying a moving image on the image display unit 138 to determine the backlight state, and when it is determined to be the backlight state, the light emission controller 122 The light source 124 can be turned on by this.

In addition, the light emission controller 122 of the imaging apparatus 100 may gradually increase or decrease the amount of light of the light source 124 in synchronization with the vertical synchronization signal of the moving image read out from the CCD 102. In addition, the light metering unit 112 of the imaging device 100 may observe the light amount at a predetermined cycle, and the imaging device 100 may have a light metering value of the light metering unit 112 reaching a predetermined amount or the light emission amount of the light source 124. At this point in time, the increase in the amount of light by the light emission controller 122 can be stopped.

In addition, the light metering unit 112 can output a light metering value corresponding to the dark portion determined by the backlight determination function of the CPU 126. Furthermore, the imaging device 100 associates the light metering value corresponding to the dark portion determined by the backlight backlight determination function of the CPU 126 with the amount of light emitted by the light source 124 at that time, so that the memory 132 and the recording medium ( 118) or other storage means.

In addition, the imaging apparatus 100 includes a photometric value (first luminance level) observed when the light source 124 emits light with a predetermined amount of light, and a photometric value observed when the light source 124 emits light with a light amount smaller than the predetermined amount of light ( Second luminance level) can be compared. Furthermore, the imaging apparatus 100 may compare the photometric value (third luminance level) observed when the light source 124 emits light with a light amount larger than the predetermined amount of light and the above-described photometric value (first luminance level). . And when the first brightness level, the second brightness level, and the third brightness level satisfies the relationship of the third brightness level ≤ first brightness level, or the first brightness level ≤ second brightness level, It is determined that the effect by the illumination light is low, and the light source 124 is turned off.

To this end, the imaging apparatus 100 may further include a luminance comparator for comparing the luminance levels. For example, the CPU 126 of the imaging device 100 may be provided with a brightness comparison function for comparing the brightness. The first, second and third luminance levels may be photometric values corresponding to dark portions (focus areas) determined by the backlight backlight function of the CPU 126 among the luminance level values of the pixels output by the photometric unit 112. have.

In addition, the imaging device 100 can determine the illumination light only when the acquisition time difference between the first brightness level and the second brightness level or the acquisition time difference between the first brightness level and the third brightness level is smaller than a predetermined value. Effect determination can be made. This is because in the case of comparing photometric values having a large acquisition time difference, there is a possibility that the light source 124 may be turned off when an effect due to illumination light occurs due to the movement or change of the subject.

Next, the flow of the backlight correction processing by the imaging device 100 described above is briefly summarized. Normally, the imaging device 100 waits for the user to press the shutter 128 while displaying a moving image (preview image). The imaging device 100 records each frame of the preview image in a predetermined order for a plurality of data storage areas of the memory 132. For example, when the memory 132 has two data storage areas, the imaging apparatus 100 converts the writing area and the reading area in units of frames and repeatedly displays frames to form a preview image.

Simultaneously with the processing of the preview image, the imaging device 100 generates the luminance signal Y from the RGB signal for the predetermined region of the CCD 102, and integrates the pixel unit for each predetermined region for one frame. Calculate the metering value. The imaging device 100 calculates the center metering value corresponding to the region of interest of the CCD 102 and the background metering value corresponding to the remaining region from the metering values calculated for each divided region. The metering values calculated for each divided area are stored in the ring buffer, and all the metering values within a predetermined period are stored. The same applies to the central metering value and the background metering value.

Thereafter, the imaging apparatus 100 determines the backlight state based on the center metering value and the background metering value. At this time, when the center metering value is darker than the background metering value, it is determined as the backlighting state. The imaging apparatus 100 then determines whether the light source 124 is turned on or off. When the backlight is in a backlit state and the light source 124 is turned off, the imaging device 100 unconditionally turns on the light source 124. On the other hand, when the light source 124 is in the lit state, the imaging device 100 determines the illumination effectiveness for the subject based on the metering value when the illumination is dark. If the metering value is not greater than the predetermined value even if the illumination is given, the imaging device 100 determines that the effect of the illumination is not effective, and turns off the light source 124. In addition, the imaging apparatus 100 calculates an amount of light suitable for the light source 124 to emit light based on the center metering value and the background metering value.

According to the above-described functional configuration and processing, even in a backlit state, a moving picture of good quality can be taken by irradiating the subject with illumination light and correcting the dark portion. In addition, it is possible to prevent the background portion (bright portion), which has been a conventional problem in backlight compensation by exposure, from turning white. And even in a backlit state, a moving image and a still image can be made equal exposure. Furthermore, since the lighting effect is automatically determined and turned off, the power saving effect of the imaging device can be obtained. In addition, with respect to the light amount control, since the light amount is corrected according to the luminance difference between the frames, there is an effect that natural back light correction is realized.

In the description of the above-described embodiment, although not shown in the drawings, an imaging optical system for imaging incident light with the CCD 102 may be provided at the front end of the CCD 102 in the imaging device 100. The imaging optical system may mainly include a lens unit, a zoom mechanism, a focus mechanism, an aperture mechanism, and a general barrel for installing a lens. The focus mechanism is formed by a focus lens or the like. The aperture mechanism is a means for adjusting the direction or range of the light beam by changing the size of the aperture. In addition, the zoom mechanism, the focus mechanism and the aperture mechanism may be driven by a separately provided motor driver. As the imaging optical system, for example, a single focus lens, a zoom lens, or the like can be used.

Although the present invention has been described with reference to the above-described embodiments, these are merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the appended claims.

1 is a block diagram showing a functional configuration of an imaging device 100 according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an example of the divisional configuration of an image region of the imaging device included in the imaging device of FIG. 1.

FIG. 3 is an explanatory diagram showing a configuration example of a light metering portion of the imaging device of FIG. 1.

4 is a schematic circuit diagram illustrating an example of a light emission controller of the imaging device of FIG. 1.

FIG. 5 is a graph illustrating a relationship between an output intensity and a light emission amount of a control signal of the light emission controller of FIG. 4.

FIG. 6 is an explanatory diagram showing a signal synchronization method by the synchronization circuit 1228 of the light emission controller of FIG. 4.

FIG. 7 is a flowchart illustrating a flow of a video backlight correction process performed by the imaging device of FIG. 1.

8 is a flowchart showing the flow of backlight determination processing performed by the imaging device of FIG.

9 is a flowchart showing a flow of an illumination determination process performed by the imaging device of FIG. 1.

FIG. 10 is a flowchart showing a flow of light amount calculation processing performed by the imaging device of FIG. 1.

* Explanation of symbols for main parts of the drawings

100: imaging device 128: shutter

102: CCD 130: table storage unit

104: CDS / AMP section 132: memory

106: A / D conversion unit 134: Compression processing unit

108: image signal generator 136: video encoder

110: bus 138: image display unit

112: meter 1128: adder

114: image signal processing unit 1130: integration unit

116: recording medium control unit 1222: power supply terminal

118: recording medium 1224: synchronization signal input terminal

120: timing generator 1226: control signal input terminal

122: light emission controller 1228: synchronization circuit

124: light source 1230: current limiting circuit

27, 28, 35, 36: region of interest 1232: ground terminal

126: CPU 1122, 1124, 1126: multiplier

Claims (10)

An imaging device which detects the reflected light intensity of the subject; A light emitting unit capable of emitting light toward the subject while the reflected light intensity is continuously detected by the imaging device a plurality of times; A light metering unit detecting a brightness level of the subject according to the reflected light intensity detected by the imaging device; A backlight determination unit that determines a backlight state based on the luminance level of the subject; And And a light emission control unit which controls the light emitting unit to irradiate light to the subject when it is determined in the backlight state by the backlight determining unit. The method of claim 1, The backlight determining unit sets some of the pixels included in the image pickup device as a region of interest, and determines a backlight state by comparing the luminance levels of the pixels of the region of interest with the luminance levels of pixels of a background region other than the region of interest. Image pickup device. The method of claim 2, The backlight determining unit calculates a central metering value obtained by averaging luminance level values of pixels in the region of interest, calculates a background metering value averaged of luminance level values of pixels in the background region, and then outputs the center metering value and the An imaging device which compares a background photometric value and determines a backlight state. The method of claim 3, The backlight determining unit calculates a median average metering value by averaging a plurality of center metering values corresponding to a plurality of sync signals sequentially generated to read reflected light intensities of the pixels of the imaging device, and calculates background metering values. And a background average photometric value is calculated by averaging, and then the backlight average state is determined by comparing the central average photometric value with the background average photometric value. The method according to any one of claims 1 to 4, And the region of interest is set to an area corresponding to a dark portion of the subject as a result of detection of the photometer. The method according to any one of claims 1 to 4, The light emission controller may control the amount of light in the light emitting unit. The light emission control unit in synchronization with a synchronization signal for reading the reflected light intensity of the pixels of the imaging device until the luminance level detected by the light metering unit reaches a predetermined value or reaches the maximum amount of light irradiated by the light emitting unit. Wherein the amount of light irradiated by the light emitting portion is increased step by step. The method of claim 1, The imaging device includes a first luminance level detected when the light emitter is irradiated with the first light amount, a second luminance level detected when the second light amount is smaller than the first light amount, and the first brightness level. And a luminance comparison unit for comparing the third luminance level detected when irradiated with a third amount of light larger than the amount of light, The light emission control unit stops the illumination by the light emission unit or reduces the amount of light when the comparison result by the brightness comparison unit is a third brightness level ≤ first brightness level or a first brightness level ≤ second brightness level. Imaging device. The method of claim 7, wherein And the brightness comparison unit compares the first brightness level and the second brightness level detected within a predetermined time difference or the first brightness level and the third brightness level detected within a predetermined time difference. The method according to any one of claims 1 to 3, And the light emission control unit controls the light emission unit in synchronization with each of sequentially generated synchronization signals for reading the reflected light intensity of the pixels of the image pickup device. The method of claim 9, In response to the synchronization signals, the luminance level when the maximum light is emitted while the minimum light is emitted is compared with the luminance level when the minimum light is emitted. An image capturing apparatus, further comprising an illumination determining unit that determines whether or not it can be.

Images