JPH05103250A - Image pickup device - Google Patents

Abstract

PURPOSE:To attain a speedy and exact focusing even when a luminance differ ence between an object and a background is large at the time of photographing a night scene. CONSTITUTION:When the photographing of the night scene is judged by a night scene judging circuit 30 based on a detection level from a luminance level detecting circuit 28 based on an image pickup signal from an image pickup element 3, and the gain detection level of an AGC and gamma circuit 5 from a gain detecting circuit 11 or a diaphragm value from an encoder 25, either a band-pass filter(BPF) 16 or 31 whose high frequency pass band for a focusing judgement is different is selected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup device such as a video camera or a still video camera.

[0002]

2. Description of the Related Art FIG. 5 shows the structure of an automatic focusing device used in a conventional consumer video camera.

An image sensor 3 passes through a lens 1 and a diaphragm 2.
The light incident on is converted into an electric signal by photoelectric conversion, and after the signal processing such as gain control and gamma processing is performed by the AGC / γ circuit 5 via the sample hold circuit 4, the luminance signal is changed to the ENC (encoder) circuit 6 Entered in.
The color difference signal is also processed by the color signal processing circuit 12 and then input to the ENC circuit 6. Further ENC circuit 6
The signal output from is output from the composite video signal output terminal 7 as a composite video signal. Further, the signal output from the sample hold circuit 4 drives the aperture 2 via the aperture drive circuit 8 so that the photometric circuit 9 always keeps the subject at an optimum signal level.

The signal output from the AGC / γ circuit 5 has a plurality of band pass filters (BPFs) 15 and 16.
Band-limited by the gate circuits 17 and 18 and set on the imaging screen by the gate circuits 17 and 18 (focus detection area)
Only the video signal corresponding to the inside is passed. Gate circuit 1
The image pickup signals corresponding to the inside of the distance measurement area extracted by 7 and 18 are detected by the detection circuits 19 and 20, and
The sample and hold circuits 21 and 22 perform sample and hold (hereinafter, the sampled and held voltage is referred to as a focus voltage), and the focus voltage output from each of the sample and hold circuits is focused or unfocused. Make a decision. That is, the motor speed / direction determination circuit 24 determines the speed and direction of the motor based on this focus voltage, inputs the signal to the focus drive circuit 14, drives the focus motor 13, and operates to focus.

Further, the high-brightness detection circuit 10 detects high brightness by the signal output from the S / H circuit 4, and the high-brightness removal circuit 23, to which the detection signal is input, outputs the AG signal.
The high luminance area of the output signal from the C / γ circuit 5 is removed and B
Input to PF15,16.

[0006]

However, in the above-described automatic focusing apparatus, when the night scene is photographed, there is a large difference in luminance between the subject and the background, so that the image pickup signal tends to have high luminance and the subject is not focused. However, there are drawbacks such as a lack of response and slow response.

An object of the present invention is to provide an image pickup apparatus which solves the above problems.

[0008]

The present invention has the above-mentioned object.
The feature of this lens is to achieve it.
And an image pickup for photoelectrically converting the light condensed by the lens
An element, provided between the lens and the image sensor
Imaging from the diaphragm and the imaging signal output from the imaging means
A detecting means for detecting a brightness signal level in the screen;
Multiple detectors to detect different high-frequency components of image signal
Of the detection means and the output signals of the plurality of detection means
Focus adjusting means for adjusting the focus of the lens;
The brightness state in the imaging screen output from the output means and
Amplification amount of the amplification means for controlling the level of the imaging signal or before
According to the information of the aperture, at least the plurality of detection means
Also comprises means for changing one characteristic
Image pickup device.

Another feature of the present invention is that, in accordance with the brightness state in the image pickup screen and the amplification amount of the amplification means for controlling the level of the image pickup signal or the information of the diaphragm.
Instead of changing at least one characteristic of the plurality of detecting means, the plurality of detecting means are determined according to the brightness state in the image pickup screen and the amplification amount of the amplifying means for controlling the level of the image pickup signal or the information of the diaphragm. The image pickup apparatus is provided with means for changing the level of the image pickup signal given to the.

[0010]

According to the present invention, comfortable and optimum focusing can be obtained even at the time of photographing a night scene where there is a large brightness difference between the subject and the background.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An image pickup apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a first embodiment of the image pickup apparatus according to the present invention. In the figure, the same components as those in FIG. 4 are designated by the same reference numerals, and detailed description thereof will be omitted.

The light that has passed through the lens 1 and the diaphragm 2 and is incident on the image pickup device 3 is photoelectrically converted into an electric signal here, and is input to the A / D conversion circuit 26 through the sample hold (S / H) circuit 4. To be done. In the A / D conversion circuit 26, the analog signal of the image pickup signal is converted into a digital signal at high speed, and A
It is input to the GC / γ circuit 5, where gain control and gamma processing are performed, and a luminance signal and a color difference signal are output. The digitized luminance signal is band-limited by the low-pass filter (LPF) 27, and the luminance level detection circuit 2
8 is input. Here, the brightness level in the image pickup screen is made into a histogram to estimate what kind of shooting state. Figure 2
The solid line represents the histogram of the brightness level at the time of shooting the night view (the dotted line is general shooting). As shown in FIG. 2, in the case of a night view, it is often distributed only at the extremely high brightness level and the extremely low brightness level.
Therefore, when the histogram has a solid line in FIG. 2, it is determined as a night view. In order to determine the night view state more accurately, the night view determination circuit 30 further sets the AG
In the output signal of the gain detection circuit 11 for C, when the gain is very high or when the information of the diaphragm encoder 25 is near the opening of the diaphragm, it is judged as the night view state, and the night view judgment circuit 3
A night scene determination signal is output from 0 and input to the switching circuit 32.

The night view discriminating operation in the above configuration will be described with reference to the flow chart of FIG. When the flow is started, first, when scanning for one screen is completed (S1), a histogram representing the brightness distribution of the screen is created as described above (S2). Subsequently, from the histogram, the number H of points showing the luminance equal to or higher than the high luminance side threshold TH is taken in (S3), and the number L of points showing the luminance less than the low luminance side threshold TL is taken in (S4). ), And the number M of points indicating the intermediate brightness is captured (S5). From these values, the high-luminance point H and the low-luminance point L are above a predetermined value, respectively,
It is determined whether or not the condition that the intermediate luminance point M is equal to or less than a predetermined value is satisfied (S6). If the condition is satisfied, the aperture encoder 18 detects whether the aperture is open (S7), and the aperture is stopped. Is open, AG
The gain of the C circuit 5 is detected by the gain detection circuit 9,
It is determined whether or not the gain is increased (S
8). If the gain is increased, it is determined that the night view is being taken, and the night view shooting determination signal is input to the switching circuit 32 (S9). If any one of the conditions of S6, S7, and S8 is not satisfied, it is determined that normal shooting is performed, and a signal to that effect is input to the switching circuit 30 (S10).

The luminance signal band-limited by the LPF 27 is input to the ENC circuit 6, and is output as a composite video signal together with the color difference signal processed by the color signal processing circuit 12, and further D / A. With the converter 29,
It is converted into an analog signal and output from the composite video output terminal 7.

On the other hand, the signals output from the AGC / γ circuit 5 are supplied to band pass filters (BPF) 15, 16, 31 having different pass band characteristics. BPF15
Is for the low and middle frequencies, BPF 16 is for the high frequencies, and BPF 31 is for the ultra-high frequencies, and the frequency components corresponding to the respective pass bands are extracted and passed. Here, according to the determination signal of the night scene determination circuit 30 described above, BPF 16 for high frequency, B
The switching circuit 32 selects the output signal for the ultra high frequency range of the PF 31.
Do in. That is, when the night scene determination circuit 30 determines that the night scene is photographed, the switching circuit 32 causes the BPF 31
When the output of is selected and it is determined that the shooting is general shooting, B
The output of the PF 16 is selected and input to the gate circuit 18.

Signal and BPF extracted from BPF 15
16 or the signal extracted from the BPF 31, the gate circuits 17 and 18 extract the image pickup signal in the distance measurement area,
After being detected by the detection circuits 19 and 20, respectively, they are sampled and held by the sample and hold circuits 21 and 22 and input to the motor speed / direction determination circuit 24 as a focus voltage. Further, the motor speed / direction determination circuit 24 determines the speed and direction of the motor, and outputs the determination signal
The focus is input to the focus drive circuit 14, the focus motor 13 is driven, and the lens is driven so as to focus.

As described above, even in the case of the night view shooting, it is automatically determined that the night view shooting is performed, and in that case, by selecting the BPF for the ultra-high range and obtaining the focus voltage, focusing The out-of-focus determination can be obtained more accurately. As a result, fast and optimum focusing can be obtained.

[Other Embodiments] FIG. 3 is a block diagram showing the configuration of the second embodiment of the present invention. In the figure, the same components as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.

As in FIG. 1, when the night view determination circuit 30 determines the night view, the night view determination signal is input to the gain switching circuit 33, where the level of the output signal of the AGC / γ circuit 5 is set to an arbitrary gain. Just lower it and input to BPF15 and BPF16. After being input to the BPFs 15 and 16, the focus voltage corresponding to the focus degree is obtained and the focus motor is driven as in the first embodiment. As described above, even in the case of night view shooting, it is automatically determined that it is night view shooting, and the focus voltage is obtained by lowering the level of the digitized image pickup signal to determine whether the object is in focus or out of focus. It can be obtained more accurately, and optimal focus can be obtained quickly.

[0021]

As described above, according to the present invention, rapid and accurate focusing can be obtained even in the case where there is a large difference in luminance between the subject and the background, such as night scene photography.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a histogram of brightness levels in a screen.

FIG. 3 is a block diagram showing a second embodiment of the present invention.

FIG. 4 is a flowchart of a night view determination operation.

FIG. 5 is a block diagram of a general imaging device.

[Explanation of symbols]

 1 Lens 2 Aperture 3 Image Sensor 4 S / H Circuit 5 AGC / γ Circuit 6 ENC Circuit 7 Composite Video Output Terminal 8 Aperture Drive Circuit 9 Photometric Circuit 10 High Brightness Detection Circuit 11 Gain Detection Circuit 12 Color Signal Processing Circuit 13 Focus Motor 14 Focus drive circuit 15 BPF 16 BPF 17,18 Gate circuit 19,20 Detection circuit 21,22 Sample hold 23 High brightness removal 24 Motor speed / direction determination 25 Aperture encoder 26 A / D converter 27 LPF 28 Brightness level detection circuit 29 D / A converter 30 night view discrimination circuit 31 BPF 32 switching circuit 33 gain switching circuit

Claims (2)

[Claims] 1. A lens, an image pickup device for photoelectrically converting light collected by the lens, a diaphragm provided between the lens and the image pickup device, and an image pickup signal output from the image pickup means. Detecting means for detecting a luminance signal level in the image pickup screen, a plurality of detecting means for detecting different high frequency components of the image pickup signal, and focus adjustment of the lens according to output signals of the plurality of detecting means. At least one of the plurality of detecting means is selected according to the focus adjusting means to be performed, the brightness state in the image pickup screen output from the detecting means, and the amplification amount of the amplifying means for controlling the level of the image pickup signal or the information of the diaphragm. And a means for changing two characteristics. 2. A lens, an image pickup device for photoelectrically converting light collected by the lens, a diaphragm provided between the lens and the image pickup device, and an image pickup signal output from the image pickup means. Detecting means for detecting a luminance signal level in the image pickup screen, a plurality of detecting means for detecting different high frequency components of the image pickup signal, and focus adjustment of the lens according to output signals of the plurality of detecting means. Focusing means for performing, and an image to be given to the plurality of detecting means according to the brightness state in the image pickup screen output from the detecting means and the amplification amount of the amplifying means for controlling the level of the image pickup signal or the information of the diaphragm. An image pickup apparatus comprising: a unit for changing a signal level.