JPH11215426A - Automatic focusing system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an automatic focusing system by which an object can be focused, even at a dark place or in the case of the object where there is no contrast. SOLUTION: In this automatic focusing system, luminance data in response to digital image data are outputted as an AE evaluation value, and an AF area is set to at lest part of areas of a screen of an image-pickup element 13. Whether or not the AE evaluation value is smaller than a predetermined value is discriminated. When the AE evaluation value is smaller than the predetermined value, an extended AF area is set, the AF evaluation value obtained integrating high frequency component of luminance data of the digital image data in the AF area is outputted, and while a focus lens system 101a is moved, the AF evaluation value is sampled, and the focusing is discriminated based on the sampling result of the AF evaluation value to drive the focus lens system 101a to the focal position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an autofocus device, and more particularly, to an autofocus device applied to a digital camera or the like.

[0002]

2. Description of the Related Art Conventionally, as an auto-focusing device in an image pickup apparatus such as a video camera, a high-frequency component of a picked-up video signal obtained from an image pickup device (CCD) is converted to an HPF or BPF.
Through the PH, the data of the imaged video signal passed through the HPF or the BPH is transmitted for a certain period (for example, one field).
Generally, a method of integrating each time and detecting it as a focus evaluation value and controlling the distance between the lens and the imaging device so that the value becomes a peak is generally used.

In such a system, a detection range (focus area) of a focus evaluation value on an image pickup screen is generally fixed to a fixed size at the center of the screen.

[0004]

However, in the conventional method, if the focus area is set to be large, when a subject at a different distance within the same screen is photographed, or when the background of the subject has a high contrast, etc. However, it is uncertain which subject to focus on, and there is a problem that the target subject of the photographer is not always focused. For example, when the background of a subject has a high contrast, the background may be focused depending on the ratio of the area of the subject to the background in the focus area.

It is conceivable that the focus area is reduced so that only the subject at the center of the screen is focused.
There is a problem that a subject frequently moves out of a small focus area due to camera shake of a photographer or slight movement of the subject, which tends to cause a malfunction.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to provide an autofocus apparatus capable of focusing a subject even in a dark place or a subject having no contrast.

[0007]

According to a first aspect of the present invention, there is provided an autofocus apparatus which converts subject light passing through a lens system including a focus lens system into an electric signal and converts the light into image data. An image sensor for outputting,
A / D conversion means for outputting digital image data obtained by A / D conversion of the image data, AE evaluation value output means for outputting luminance data corresponding to the digital image data as an AE evaluation value, and a screen of the image sensor AF area setting means for setting at least a part of the area as an AF area; determining whether the AE evaluation value is smaller than a predetermined value; and determining whether the AE evaluation value is smaller than a predetermined value. AF area enlargement setting means for setting an AF area obtained by enlarging the AF area; and an AF evaluation value output for outputting an AF evaluation value obtained by integrating a high frequency component of luminance data of digital image data in the AF area. Means, while moving the focus lens system,
An AF evaluation value sampling unit that causes the F evaluation value output unit to sample the AF evaluation value; a focus driving unit that determines focusing based on a sampling result of the AF evaluation value and drives the focus lens system to a focus position. ,
It is provided with.

According to a second aspect of the present invention, there is provided an auto-focusing device for converting an object light through a lens system including a focus lens system into an electric signal and outputting the electric signal as image data, A / D conversion means for outputting the converted digital image data, AE evaluation value output means for outputting luminance data corresponding to the digital image data as an AE evaluation value, and at least a partial area of an imaging screen of the imaging device AF to set as AF area
Area setting means, and an AF obtained by integrating high-frequency components of luminance data of digital image data in the AF area
An AF evaluation value output unit that outputs an evaluation value; an AF evaluation value sampling unit that causes the AF evaluation value output unit to sample the AF evaluation value while moving the focus lens system; and an AF evaluation value sampling unit. A focus driving unit that determines focusing based on a sampling result of the AF evaluation value and drives the focus lens system to a focus position; and the AF evaluation value is equal to or less than a reference value before sampling by the AF evaluation value sampling unit. A case of setting an AF area obtained by enlarging the AF area
F area enlargement setting means.

According to a third aspect of the present invention, there is provided an image pickup device for converting subject light through a lens system including a focus lens system into an electric signal and outputting the electric signal as image data, and a signal level of the image data. Variable gain means for correcting the image data, A / D conversion means for outputting digital image data obtained by A / D conversion of the image data, and AE evaluation value output for outputting luminance data corresponding to the digital image data as an AE evaluation value Means, an AF evaluation value output means for outputting an AF evaluation value obtained by integrating a high frequency component of the luminance data of the digital image data, and an AF evaluation value output means for moving the focus lens system.
AF evaluation value sampling means for sampling an evaluation value; focus driving means for determining focus by sampling the AF evaluation value and driving the focus lens system to a focus position; In some cases, the apparatus further comprises gain control means for controlling to increase the gain of the variable gain amplifying means during sampling of the AF evaluation value.

According to another aspect of the present invention, there is provided an auto-focusing device for converting an object light through a lens system including a focus lens system into an electric signal and outputting the electric signal as image data, and a signal level of the image data. Variable gain means for correcting the image data, A / D conversion means for outputting digital image data obtained by A / D conversion of the image data, and AE evaluation value output for outputting luminance data corresponding to the digital image data as an AE evaluation value Means, an AF evaluation value output means for outputting an AF evaluation value obtained by integrating a high frequency component of the luminance data of the digital image data, and an AF evaluation value output means for moving the focus lens system.
AF evaluation value sampling means for sampling an evaluation value, focus driving means for determining focus based on the sampling result of the AF evaluation value, and driving the focus lens system to a focus position, and sampling of the AF evaluation value sampling means And gain control means for controlling the gain of the variable gain amplifying means to increase during the sampling of the AF evaluation value when the AF evaluation value is equal to or less than the reference value.

According to a fifth aspect of the present invention, there is provided a focus lens device, wherein: an image pickup device for converting subject light through a lens system including a focus lens system into an electric signal and outputting the electric signal as image data; A / D conversion means for outputting D-converted digital image data, AE evaluation value output means for outputting luminance data corresponding to the digital image data as an AE evaluation value, and integration of high frequency components of luminance data of the digital image data AF evaluation value output means for outputting an AF evaluation value obtained as a result, AF evaluation value sampling means for causing the AF evaluation value output means to sample the AF evaluation value while moving the focus lens system, Focus driving means for judging focus based on a sampling result and driving the focus lens system to a focus position , Based on the AE evaluation value, a normal AE control means for normal AE control, the normal AE
AE for AF that sets AE for AF area separately from control
Setting means, wherein A is set by the AF AE setting means.
AF is executed after the AE for the F area is executed.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a configuration diagram of a digital camera to which the autofocus device according to the present embodiment is applied. In FIG. 1, reference numeral 100 denotes a digital camera. The digital camera 100 includes a lens system 101, a mechanical mechanism 102 including an aperture / filter unit, a CCD 103, and a CDS.
Circuit 104, variable gain amplifier (AGC amplifier) 105,
A / D converter 106, IPP 107, DCT 108, coder 109, MCC 110, DRAM 111, PC card interface 112, CPU 121, display unit 12
2, operation unit 123, SG (control signal generation) unit 126, strobe device 127, battery 128, DC-DC converter 129, EEPROM 130, focus driver 131, pulse motor 132, zoom driver 133,
It comprises a pulse motor 134 and a motor driver 135. Also, the PC card interface 11
2, a detachable PC card 150 is connected.

The lens unit includes a mechanical mechanism 102 including a lens 101 system, a diaphragm and a filter section, and a mechanical shutter of the mechanical mechanism 102 performs simultaneous exposure of two fields. The lens system 101 is formed of, for example, a varifocal lens, and includes a focus lens system 101a and a zoom lens system 101b.

The focus driver 131 is connected to the CPU 12
1 according to the control signal supplied from the
2 to move the focus lens system 101a in the optical axis direction. The zoom driver 131 includes a CPU 121
Pulse motor 132 according to the control signal supplied from
To move the zoom lens system 101b in the optical axis direction. In addition, the motor driver 135 includes the CPU 121
The mechanical mechanism 102 is driven in accordance with a control signal supplied from the controller, and for example, an aperture value of the aperture is set.

The CCD (Charge Coupled Device) 103 converts an image input through the lens unit into an electric signal (analog image data). The CDS (correlated double sampling) circuit 104 is a circuit for reducing noise in the CCD type image pickup device.

The AGC amplifier 105 corrects the level of the signal that has been correlated double-sampled by the CDS circuit 104. The gain of the AGC amplifier 105 is determined by the CPU 1
21 allows the setting data (control voltage) to be transferred to the AGC amplifier 1 via a D / A converter built in the CPU 121.
05 is set. A / D
The converter 106 converts analog image data input from the CCD 103 via the AGC amplifier 105 into digital image data. That is, the output signal of the CCD 103 is converted into a digital signal at the optimum sampling frequency (for example, an integer multiple of the subcarrier frequency of the NTSC signal) by the A / D converter 105 via the CDS circuit 104 and the AGC amplifier 105. Is done.

The digital signal processor IPP
(Image Pre-Processor) 107, DCT (Discrete Cos)
ine Transform) 108 and coder (Huffman Enco
A der / Decoder) 109 performs various processing, correction, and data processing for image compression / decompression on the digital image data input from the A / D converter 106 by dividing the digital image data into color difference (Cb, Cr) and luminance (Y). Apply. Image compression / decompression unit 107
Performs, for example, orthogonal transformation, which is a process of JPEG-compliant image compression / decompression, and Huffman encoding / decoding, which is a process of JPEG-compliant image compression / decompression.

Further, an MCC (Memory Card Controlle)
An r) 110 temporarily stores the compressed image and records the image on the PC card 150 via the PC card interface 112 or reads the image from the PC card 150.

The CPU 121 uses the RAM as a work area in accordance with a program stored in the ROM, and controls all operations inside the digital camera in accordance with an instruction from the operation unit 123 or an external operation instruction such as a remote controller (not shown). . Specifically, the CPU 121 performs an imaging operation, an automatic exposure (AE) operation, an automatic white balance (AWB)
It controls the adjustment operation and the AF operation.

A camera power source is a battery 128, for example, NiCd, nickel metal hydride, lithium battery, etc.
The signal is input to the C-DC converter 129 and supplied to the inside of the digital camera.

The display unit 122 is implemented by an LCD, an LED, an EL, or the like, and displays photographed digital image data, decompressed recorded image data, and the like. Operation unit 1
Reference numeral 23 includes buttons for externally performing function selection, shooting instructions, and other various settings. EEPRO
In M130, adjustment data and the like used when the CPU 121 controls the operation of the digital camera are written.

The digital camera 100 (CPU 1
21) converts image data obtained by imaging a subject into a PC
Recording Mode for Recording on Card 150 and PC Card 15
The display mode includes a display mode for displaying image data recorded at 0, a monitoring mode for directly displaying captured image data on the display unit 122, and the like.

FIG. 3 shows a control voltage (Control Voltage) and an output gain (Measured) of the AGC amplifier 105.
FIG. 2, the horizontal axis represents the control voltage (Control Vol.) Of the AGC amplifier 105.
stage, and the vertical axis indicates the output gain (Me
asured Gain). The data of the characteristic curve shown in FIG. 2 is digitized and stored in the EEPROM 130.

FIG. 2 is a diagram showing an example of a specific configuration of the IPP 107. As shown in FIG. 2, the IPP 107 separates the digital image data input from the A / D converter 106 into R, G, and B color components.
A signal interpolating unit 1072 for interpolating the separated R, G, B image data, a pedestal adjusting unit 1073 for adjusting the black level of each of the R, G, B image data, and each of the R, B images A white balance adjustment unit 1074 for adjusting the white level of the data; a digital gain adjustment unit 1075 for correcting each of the R, G, and B image data with a gain set by the CPU 121; a gamma conversion unit 1076 for performing γ conversion, a matrix unit 1077 for separating RGB image data into color difference signals (Cb, Cr) and a luminance signal (Y), a color difference signal (Cb, Cr), and a luminance signal (Y) And a video signal processing unit 1078 that creates a video signal based on the video signal and outputs the video signal to the display unit 122.

Further, the IPP 107 includes a Y operation unit 1079 for detecting luminance data (Y) of the image data after the pedestal adjustment by the pedestal adjustment unit 1073, and a Y operation unit 1
079, a BPF 1080 that passes only a predetermined frequency component of the luminance data (Y) detected, and an integrated value of the luminance data (Y) that has passed through the BPF 1080 is used as an AF evaluation value as C value.
An AF evaluation value circuit 1081 that outputs to the PU 121, an AE evaluation value circuit 1082 that outputs to the CPU 121 a digital count value corresponding to the luminance data (Y) detected by the Y operation unit 1079 as an AE evaluation value, and a white balance adjustment unit 1074 Calculation unit 1083 for detecting luminance data (Y) of each of R, G, and B image data after gain adjustment by
And an AWB evaluation value circuit 1084 that counts the luminance data (Y) of each color detected by the Y operation unit 1083 and outputs the result to the CPU 121 as an AWB evaluation value of each color.
And CPUI which is an interface with the CPU 121
/ F 1085 and a DCTI / F 1086 which is an interface with the DCT 108.

FIG. 4 shows an example of a light receiving surface of the CCD 103. Such a CCD screen is, as shown in FIG.
It is composed of 640 v lines × 480 h lines. Further, the CCD screen is divided into blocks composed of 80 × 80 CCD elements.

FIG. 5 shows an example of the AE area.
The AE area includes an area obtained by dividing the CCD screen shown in FIG. 4 into six AE areas 1 to 6. Where AE
Area 5 includes AE area 6 and AE area 1
4 are rectangular areas, some of which are AE
Areas 6 and 5 overlap. The above-described AE evaluation value circuit 1082 outputs an AE evaluation value obtained by performing a weighting operation on the luminance values of the six AE areas 1 to 6 described above. More specifically, the Y operation unit 1079 outputs the luminance data of each pixel of the image data to the AE evaluation value circuit 1082,
The AE evaluation value circuit 1082 calculates a value obtained by integrating the luminance data in each of the AE areas 1 to 6 as a luminance value, and weights the calculated luminance value of each of the AE areas 1 to 6 to an AE evaluation value. To the CPU 121.

FIG. 6 shows an example of an AF area (AF area 1) for obtaining a normal AF evaluation value. This AF area is the same as the AE area 6 of the AE area shown in FIG. ing.

FIG. 7 shows an AF area (AF area) for obtaining an AF evaluation value in a dark place or a subject having no contrast.
An example of the area 2) is shown, and this AF area is the same area as the AE area 5 of the AE area shown in FIG.

The Y operation section 1079 detects the luminance data (Y) of the image data, the BPF 1080 allows only the high frequency component to pass therethrough, and outputs the AF evaluation value circuit 1081
Outputs to the CPU 121 an AF evaluation value obtained by integrating a high frequency component of the passed luminance data (Y) in the AF area.

Next, the operation of the digital camera will be described.

Generally, A for sampling the AF evaluation value
When the F area is enlarged, if the subject is three-dimensional (a subject having a depth), the accuracy of AF deteriorates, so that the AF area cannot be increased so much. Also, even when the subject is small, it is not possible to focus only on the subject.
On the other hand, to perform AF on a dark place or a subject without contrast, it is possible to focus on a darker place or a subject with less contrast by increasing the area for sampling the AF evaluation value. Therefore, in the present embodiment, when the subject is dark or has no contrast, the focusing operation is performed even if the accuracy is lower than the AF error caused by the three-dimensional subject, so that the sampling area of the AF evaluation value is increased. ing.

In the AE control, the CPU 121 controls the shutter speed and the AGC amplifier 105 so that the AE evaluation value becomes a reference value. In the present embodiment, the present invention will be described on the assumption that the aperture is fixed (F4; Av4).

In the AF control, the CPU 121 sets the shutter speed and the gain of the AGC amplifier 105, and then drives the pulse motor 132 via the focus driver 131 for a specified pulse in the 1 Vd period to drive the focus lens system 101a. While moving, the AF evaluation value is sampled, and the peak position of the sampled AF evaluation value is set as the focus position, and the focus lens system 101
a is driven to the in-focus position.

FIG. 8 is a flowchart for explaining the AF area setting operation executed by the CPU 121.

In FIG. 8, first, the AF of the IPP 107
In registers aflwdx and aflwdy that set the area,
Data for setting AF area 1 (see FIG. 6)
_Aflwdx and from_aflwdy are set, and the AF area 1 (see FIG. 6) is set as the AF area (step S1). Then, the luminance value Lv (lv_value) is equal to the lower limit value af_dark_th.
It is determined whether it is smaller than rd (step S2), and the luminance value Lv
If (lv_value) <af_dark_thrd, the AF area 1 is used to perform AE setting processing during AF execution (see FIG. 9). On the other hand, the luminance value Lv (lv_value) <af_
If it is dark_thrd, it is determined that the image is dark, and it is determined whether the AF evaluation value now_af_a is smaller than a lower limit af_dark_now_af_a (step S3), and now_af_a <af
If it is _dark_now_af_a, it is set to AFNG (step S4). On the other hand, now_af_a <af_dark_no
If not w_af_a, the process proceeds to step S5,
Register aflwdx for setting the AF area of the IPP 107,
Data from_dark_aflwdx and from_dark_aflw for setting AF area 2 (see FIG. 7) in aflwdy, respectively
dy, AF area 2 (see FIG. 6) is set as the AF area, and A
E setting processing (see FIG. 9) is performed.

FIG. 9 is a flowchart for explaining the AE setting operation performed by the CPU 121 during AF execution.

In FIG. 9, first, a luminance value Lv (lv_lv_lv_lv_lv_lv_lv_lv_lv_lv_lv_lv_lv)
value) (step S10). Next, the manual exposure correction value (exp_value) is set to "0" (step S11), and a backlight correction value (offset value) is obtained (step S12). Then, the exposure value ev_value is
Exposure value ev_value = Luminance value Lv (lv_value) + Backlight correction value (offset_value) + Manual exposure correction value (exp_
value) (step S13).

Then, the exposure value ev_value is changed to av_value
It is determined whether or not the exposure value ev_value is larger than (aperture value F4 = Av4) + monita_lo_tv (minimum shutter time 1/30 at the time of monitoring) (step S14).
If e (aperture value F4 = Av4) + monita_lo_tv (minimum shutter time 1/30 at the time of monitoring), the shutter speed value tv_value is set to the exposure value ev_value.
While -av_value (aperture value F4 = Av4) is set (step S15), if the exposure value ev_value is not more than av_value (aperture value F4 = Av4) + monita_lo_tv (minimum shutter time 1/30 at the time of monitoring), The shutter speed value tv_value is set as monita_lo_tv (1/30 of the minimum shutter time during monitoring) (step S
20), and proceed to step S16.

In step S16, a flicker check of the fluorescent lamp is performed, and the CCD shutter time is set (step S17). In order to shorten the time for outputting a luminance signal from the CCD 103, when the output from the CCD 103 is controlled such that the luminance signal is output only from a certain predetermined CCD element row of the CCD 103, the amount of the output is reduced accordingly. The shutter speed setting data is shifted and set.

Then, the gain setting value agc_value is changed to ag
c_tv_value (AGC correction value for quantization error at shutter time) + av_value (aperture value F4 = Av4) + shutter speed value tv_value-exposure value ev_value (step S18). Then, the AGC amplifier 105
Set the gain setting value agc_value (step S1)
9). The maximum AGC set value during monitoring is 2E
With v = + 12 dB, the maximum AGC set value during AF execution is
+ 3Ev = 18 dB.

By the way, if the gain of the AGC amplifier 105 is excessively increased during monitoring, AE, AWB
Therefore, it is not possible to increase the gain of the AGC amplifier 105 excessively. (If the AGC is increased, most of the image expressible portion of the CCD is increased by the AGC, so that the image expression is biased. The evaluation values for AE and AWB do not become normal values, which adversely affects the control of AE and AWB.

On the other hand, in the AF control, the magnitude (level) of the AF evaluation value itself is not required.
Since it is sufficient to increase or decrease the AF evaluation value with respect to the focus (the relative change only needs to be known), if there is a possibility that the focus may not be adjusted in a dark place or a subject without contrast, the AGC amplifier 105 may be used. Increase the gain and A
Performing F can increase the possibility of focusing. Therefore,
In the present embodiment, when the AF is performed on a subject having no contrast or when there is no contrast, the AF is performed with a gain higher than the gain of the AGC amplifier 105 at the time of monitoring, thereby reducing the possibility of focusing. High.

The AF area is generally smaller than the AE area.
When the F is performed, the high-frequency component extracted by the BPF 1080 is integrated from the luminance signal obtained by processing the digital image signal and the AF evaluation value is output, so that the appropriate exposure is performed when only the AF area is dark. Since the AF evaluation value is calculated based on the luminance signal that is not performed, the increase / decrease of the AF evaluation value with respect to the focus becomes small, or the AF accuracy is deteriorated. Therefore, in the present embodiment, when performing AF,
Not the AE control value in the AE area, but the A
By executing AF after switching to E control, A
The F area exposure is set to be appropriate.

[0046]

According to the first aspect of the present invention, there is provided an auto-focusing device which converts an object light via a lens system including a focus lens system into an electric signal and outputs the same as image data, and A / D conversion of the image data. A / D conversion means for outputting the obtained digital image data, AE evaluation value output means for outputting luminance data corresponding to the digital image data as an AE evaluation value, and at least a partial area of the image sensor screen as an AF area. AF area setting means for setting;
AF area enlargement setting means for judging whether the AE evaluation value is smaller than a predetermined value, and setting an AF area obtained by enlarging the AF area when the AE evaluation value is smaller than a predetermined value; AF evaluation value output means for outputting an AF evaluation value obtained by integrating the high frequency component of the luminance data of the digital image data in the AF area; and AF evaluation value output means while moving the focus lens system. And a focus driving unit that determines the focus based on the sampling result of the AF evaluation value and drives the focus lens system to a focus position. When AF is performed on an object having no contrast, the area for sampling the AF evaluation value is increased to increase the darkness. It is possible to make focusing even in places or subjects without contrast.

According to a second aspect of the present invention, there is provided an auto-focusing device which converts an object light through a lens system including a focus lens system into an electric signal and outputs the same as image data, and A / D conversion of the image data. A / D conversion means for outputting the converted digital image data, AE evaluation value output means for outputting luminance data corresponding to the digital image data as an AE evaluation value, and at least a part of the area of the imaging screen of the imaging device as an AF area. AF area setting means for setting as; AF evaluation value output means for outputting an AF evaluation value obtained by integrating a high frequency component of luminance data of digital image data in the AF area; and while moving the focus lens system, AF evaluation value sampling means for causing the AF evaluation value output means to sample the AF evaluation value;
Focus driving means for determining focus and driving the focus lens system to the in-focus position based on the sampling result of the AF evaluation value by the F evaluation value sampling means, and the AF evaluation value is used as a reference before sampling by the AF evaluation value sampling means. If the value is equal to or smaller than the value, the AF area is enlarged.
And AF area enlargement setting means for setting an area. Therefore, when performing AF on a dark place or a subject having no contrast, the area for sampling the AF evaluation value is increased by increasing the area. It is possible to focus on a dark place or a subject without contrast.

According to the third aspect of the present invention, there is provided an image pickup device for converting subject light through a lens system including a focus lens system into an electric signal and outputting the electric signal as image data, and a signal level of the image data. Variable gain means for correcting, A / D conversion means for outputting digital image data obtained by A / D conversion of image data, AE evaluation value output means for outputting luminance data corresponding to the digital image data as an AE evaluation value, AF evaluation value output means for outputting an AF evaluation value obtained by integrating a high-frequency component of luminance data of digital image data, and AF evaluation for causing the AF evaluation value output means to sample the AF evaluation value while moving the focus lens system Focusing is determined based on the value sampling means and the sampling result of the AF evaluation value, and the focus lens system is moved to the focused position A focus driving means for driving, A
In the case where the E evaluation value is low luminance, a gain control means for controlling to increase the gain of the variable gain amplifying means during sampling of the AF evaluation value is provided. At the time of performing AF on a subject, the possibility of focusing can be increased by performing AF by increasing the gain of the variable gain amplifier compared to at the time of monitoring.

Further, in the auto-focusing device according to the fourth aspect, an image pickup device that converts subject light through a lens system including a focus lens system into an electric signal and outputs the electric signal as image data, and a signal level of the image data. Variable gain means for correcting, A / D conversion means for outputting digital image data obtained by A / D conversion of image data, AE evaluation value output means for outputting luminance data corresponding to the digital image data as an AE evaluation value, AF evaluation value output means for outputting an AF evaluation value obtained by integrating a high-frequency component of luminance data of digital image data, and AF evaluation for causing the AF evaluation value output means to sample the AF evaluation value while moving the focus lens system Focus sampling is determined based on the value sampling means and the sampling result of the AF evaluation value, and the focus lens system is focused. A focus driving means for driving the location, before sampling the AF evaluation value sampling means,
When the AF evaluation value is equal to or less than the reference value, a gain control unit that controls to increase the gain of the variable gain amplifying unit during sampling of the AF evaluation value is provided. At the time of performing AF on a subject, the possibility of focusing can be increased by performing AF by increasing the gain of the variable gain amplifier compared to at the time of monitoring.

Further, in the focus lens device according to the fifth aspect, an image pickup device that converts subject light through a lens system including a focus lens system into an electric signal and outputs the same as image data, and converts the image data into an A / D signal. A / D conversion means for outputting the converted digital image data, AE evaluation value output means for outputting luminance data corresponding to the digital image data as an AE evaluation value, and integration of high frequency components of the luminance data of the digital image data. AF evaluation value output means for outputting the obtained AF evaluation value; AF evaluation value sampling means for causing the AF evaluation value output means to sample the AF evaluation value while moving the focus lens system;
Focus driving means for judging the focus based on the sampling result of the evaluation value and driving the focus lens system to a focus position, normal AE control means for performing normal AE control based on the AE evaluation value, and normal AE control AE setting means for setting an AE for the AF area separately from the AF area.
After executing the AE for the AF area by the AE setting means for
Since the AF is executed, when the AF is executed, the AE control is switched to the AE control in the AF area instead of the AE control in the AE area, and then the AF is executed. Focusing is possible even when only the image is dark (focusing accuracy can be maintained).

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a digital camera according to an embodiment.

FIG. 2 is a diagram illustrating an example of a specific configuration of the IPP of FIG. 1;

FIG. 3 shows a control voltage (Control V) of an AGC amplifier.
FIG. 6 is a diagram illustrating a relationship between the output gain (Measurement Gain) and the output gain (Measured Gain).

FIG. 4 is a diagram illustrating an example of a CCD screen.

FIG. 5 is a diagram illustrating an example of an AE area.

FIG. 6 is a diagram illustrating an example of an AF area.

FIG. 7 is a diagram illustrating an example of an AF area.

FIG. 8 is a flowchart illustrating an AF area setting operation performed by a CPU.

FIG. 9 is a flowchart illustrating an AE setting operation performed by the CPU during AF execution.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 Digital camera 101 Lens system 101 a Focus lens system 101 b Zoom lens system 102 Mechanical mechanism including autofocus 103 CCD (charge coupled device) 104 CDS (correlated double sampling) circuit 105 Variable gain amplifier (AGC amplifier) 106 A / D Converter 107 IPP (Image Pre-Processor) 108 DCT (Discrete Cosine Transform) 109 Coder (Huffman Encoder / Decoder) 110 MCC (Memory Card Controller) 111 RAM (Internal Memory) 112 PC Card Interface 121 CPU 122 Display Unit 123 Operation Unit 125 motor driver 126 SG unit 127 strobe 128 battery 129 DC-DC converter 130 EEPROM 131 focus driver 132 pulse motor 133 zoom driver 134 Motor 135 Motor driver 150 PC card 1071 Color separation unit 1072 Signal interpolation unit 1073 Pedestal adjustment unit 1074 White balance adjustment unit 1075 Digital gain adjustment unit 1076 Gamma conversion unit 1077 Matrix unit 1078 Video signal processing unit 1079 Y operation unit 1080 BPF 1081 AF evaluation Value circuit 1082 AE evaluation value circuit 1083 Y operation unit 1084 AWB evaluation value circuit 1085 CPU I / F 1086 DCTI / F 1075r, 1075g, 1075b Multiplier

Claims (5)

[Claims] 1. An image pickup device that converts subject light through a lens system including a focus lens system into an electric signal and outputs the image signal as an image signal, and an A / D that outputs A / D converted digital image data of the image signal. D conversion means, AE evaluation value output means for outputting luminance data corresponding to the digital image data as an AE evaluation value, and AF area setting means for setting at least a partial area of a screen of the image sensor as an AF area. An AF area expansion setting for determining whether the AE evaluation value is smaller than a predetermined value, and setting an AF area obtained by expanding the AF area when the AE evaluation value is smaller than a predetermined value; Means for outputting an AF evaluation value obtained by integrating a high-frequency component of luminance data of digital image data in the AF area;
F evaluation value output means; AF evaluation value sampling means for causing the AF evaluation value output means to sample the AF evaluation value while moving the focus lens system; and focusing is determined based on a sampling result of the AF evaluation value. And a focus drive unit for driving the focus lens system to a focus position. 2. An image pickup device for converting subject light through a lens system including a focus lens system into an electric signal and outputting the electric signal as image data, and an A / D for outputting digital image data obtained by A / D converting the image data. D conversion means; AE evaluation value output means for outputting luminance data corresponding to the digital image data as an AE evaluation value;
AF area setting means for setting as an F area; and A for outputting an AF evaluation value obtained by integrating a high frequency component of luminance data of digital image data in the AF area.
F evaluation value output means, AF evaluation value sampling means for causing the AF evaluation value output means to sample the AF evaluation value while moving the focus lens system, and AF evaluation value sampling by the AF evaluation value sampling means Focus driving means for judging focusing based on the result and driving the focus lens system to a focus position, and before sampling by the AF evaluation value sampling means,
An AF area enlargement setting means for setting an AF area in which the AF area is enlarged when the AF evaluation value is equal to or less than a reference value. 3. An image sensor for converting subject light through a lens system including a focus lens system into an electric signal and outputting the electric signal as image data; a variable gain means for correcting a signal level of the image data; A / D conversion means for outputting digital image data obtained by A / D conversion of the digital image data; AE evaluation value output means for outputting luminance data corresponding to the digital image data as an AE evaluation value; AF evaluation value output means for outputting an AF evaluation value obtained by integrating the components; AF evaluation value sampling means for causing the AF evaluation value output means to sample the AF evaluation value while moving the focus lens system; Focus drive that determines focus based on the sampling result of the evaluation value and drives the focus lens system to a focus position Means for controlling the gain of the variable gain amplifying means during sampling of the AF evaluation value when the AE evaluation value is low luminance. Focus device. 4. An image pickup device that converts subject light through a lens system including a focus lens system into an electric signal and outputs the electric signal as image data; a variable gain unit that corrects a signal level of the image data; A / D conversion means for outputting digital image data obtained by A / D conversion of the digital image data; AE evaluation value output means for outputting luminance data corresponding to the digital image data as an AE evaluation value; AF evaluation value output means for outputting an AF evaluation value obtained by integrating the components; AF evaluation value sampling means for causing the AF evaluation value output means to sample the AF evaluation value while moving the focus lens system; Focus drive that determines focus based on the sampling result of the evaluation value and drives the focus lens system to a focus position Means, before sampling by the AF evaluation value sampling means,
An auto-focusing device, comprising: a gain control unit that controls to increase the gain of the variable gain amplifying unit during sampling of the AF evaluation value when the AF evaluation value is equal to or less than a reference value. 5. An image pickup device for converting subject light through a lens system including a focus lens system into an electric signal and outputting it as image data, and an A / D for outputting digital image data obtained by A / D converting the image data. D conversion means, AE evaluation value output means for outputting luminance data corresponding to the digital image data as an AE evaluation value, and AF for outputting an AF evaluation value obtained by integrating a high frequency component of the luminance data of the digital image data. An evaluation value output unit; an AF evaluation value sampling unit that causes the AF evaluation value output unit to sample an AF evaluation value while moving the focus lens system; Focus driving means for driving the lens system to a focus position; and performing normal AE control based on the AE evaluation value. A normal AE control unit, and an AF AE setting unit for setting an AF area AE separately from the normal AE control. After the AF AE setting unit executes the AF area AE, An auto-focusing device that performs the following.