JPH05191719A - Image pickup device - Google Patents

Abstract

PURPOSE:To obtain the image pickup device with excellent picture quality provided with a gain-increase means. CONSTITUTION:A low brightness aperture correction suppression circuit 18-1 is controlled so that the suppression in the gain increase is larger than that in the normal state in response to the changeover of a gain UP switch 19. Thus, it is prevented that an excess aperture correction signal is given to noise in the gain UP state, the S/N is improved and it is avoided that low illuminant and fog picture quality is caused due to too much aperture correction suppression in the normal state.

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 an electronic still camera, and more particularly to improvement of image quality of a device having a gain increasing means.

[0002]

2. Description of the Related Art Recently, sensitivity competition has become fierce in image pickup devices such as video cameras and electronic still cameras.
Since the camera is designed so that even a little higher sensitivity can be obtained, there is an increasing number of gain-up modes that increase sensitivity. However, by electrically increasing the gain, the signal component also increases, but the noise component also increases at the same rate, resulting in an unsightly image with a lot of noise. Therefore, circuits such as a low-luminance color suppression circuit and a low-luminance aperture correction suppression circuit are provided to prevent deterioration of image quality under low illuminance.

FIG. 6 is a block diagram showing a conventional video camera. In the figure, 1 is a taking lens, 2 is a diaphragm for limiting the amount of incident light, 3 is an image sensor, 4 is a sample hold circuit, 5 is an amplifier circuit, 6 is an AGC (auto gain control) / γ circuit, and 7 is Low luminance color suppression circuit, 8
Is an adder, 9 is a setup level circuit for determining a black level, 10 is an encoder circuit, 11 is a composite video signal output terminal, 12 is an iris driver circuit, 13 is an iris photometry circuit, 14 is an iris encoder, and 15 is a low brightness judgment. A circuit, 16 is an AGC photometry circuit, 17 is an aperture correction circuit, 18 is a low-luminance aperture correction suppression circuit, 19 is a gain-up switch, and 20 is a gain-up determination circuit. The amplifier circuit 5 and the gain-up determination circuit 20 correspond to gain-up means.

Next, the operation of the conventional example will be described step by step.
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, sampled and held by the sample and hold circuit 4, and AGC · γ.
The circuit 6 performs AGC, γ processing, etc., and separates and outputs a luminance signal Y and color difference signals RY and BY. The luminance signal Y of the output of the AGC / γ circuit 6 is the aperture correction circuit 1
7 and the aperture correction signal is generated there. The aperture correction signal is suppressed by the low-luminance aperture correction suppression circuit 18 when the Y signal is low, and is added to the Y signal by the adder 8. The added signal is set up by the setup level circuit, and the encoder circuit 10
Entered in. The chroma signal C output from the AGC / γ circuit 6 is subjected to color suppression when the Y signal is low in the low luminance color suppression circuit 7, and is input to the encoder circuit 10.
The encoder circuit 10 generates a composite video signal from the input Y signal and C signal, and outputs the composite video signal output terminal 11
Output more.

[0005]

However, the conventional example has the following problems (1) to (3).

(1) The low luminance aperture correction suppression circuit is
Since the amount of suppression of aperture correction is determined by the brightness signal level, the amount of suppression of low brightness aperture correction in the gain-up state and the normal state cannot be set individually and optimally according to the noise. For example, when the amount of aperture correction suppression is set in the normal state, the amount of aperture correction suppression is small in the gain-up state because the luminance signal level is high, and the aperture correction signal is attached to noise, resulting in deterioration of image quality. On the contrary, if the low-luminance aperture correction amount is set in the gain-up state, the luminance signal level is low in the normal state, so that the aperture-correction suppression is too high, resulting in a blurred low-illuminance image quality.

(2) The setup level circuit is. Since the setup level does not change between the gain-up state and the normal state, if the setup level is set to the normal state, it tends to sink darkly when shooting low illuminance when the gain is increased. On the contrary, if the setup level is set to the gain-up state, that is, if the setup level is set to a high level, there is a problem that the image quality tends to be flare when a bright outside landscape in a normal state is photographed.

(3) The conventional low luminance color suppression circuit determines the amount of color suppression according to the luminance signal level. Therefore, the low-luminance color suppression amount in the gain-up state and the normal state cannot be optimally set individually according to the noise. Therefore, if the amount of color suppression is set in the normal state, the amount of color suppression will decrease in the gain-up state because the luminance signal level is high.
Color noise is noticeable and the image quality deteriorates. On the contrary, if the low luminance color suppression amount is set in the gain-up state, there is a problem that the luminance signal level is low in the normal state, and the color suppression is too high, resulting in an unnatural image quality without colors.

The present invention has been made in order to solve these problems, and an object of the present invention is to provide an image pickup apparatus having a gain up means and excellent in image quality.

[0010]

In order to achieve the above-mentioned object, in the present invention, an image pickup device has the following (1), (2),
Configure as in (3).

(1) Gain increasing means for increasing the gain of a video signal output from the image pickup means, switching means for switching the gain increasing means to either a normal state or a gain up state, and a low luminance signal level. When the image pickup apparatus includes a low-brightness aperture correction suppression unit that suppresses an aperture correction signal, the low-brightness aperture correction suppression unit is in a normal state in a gain-up state in response to switching of the switching unit. An image pickup apparatus that is controlled so that the amount of suppression is greater than in the case of.

(2) Gain increasing means for increasing the gain of the video signal output from the image pickup means, switching means for switching the gain increasing means to either the normal state or the gain up state, and the black level of the video signal. The setup level means is controlled so that the setup level becomes higher in the gain-up state than in the normal state according to the switching of the switching means. An image pickup device.

(3) Gain increasing means for increasing the gain of the video signal output from the image pickup means, switching means for switching the gain increasing means to either the normal state or the gain up state, and the luminance signal level is low. An image pickup apparatus comprising: a low-luminance color suppressing unit that suppresses a color signal when the gain-up state is suppressed more than in the normal state according to the switching of the switching unit. An imaging device that is controlled to increase the amount.

[0014]

In the configuration (1), the suppression amount of the low-brightness aperture correction suppression means is larger in the gain up state than in the normal state.

In the configuration (2), in the gain up state, the setup level of the setup level means is higher than in the normal state.

In the configuration (3), the amount of suppression of the low-luminance color suppression means is larger in the gain-up state than in the normal state.

[0017]

EXAMPLES The present invention will be described in detail below with reference to examples. (Embodiment 1) FIG. 1 is a "video camera" which is Embodiment 1.
It is a block diagram of. In the figure, each circuit block is the same as that described in the conventional example except for the low-luminance aperture correction suppression circuit 18-1. The low-luminance aperture correction suppression circuit 18-1 is different from the conventional low-luminance aperture correction suppression circuit 18 in that the amount of suppression is controlled according to the switching of the gain up switch 19.

Next, the operation will be described step by step. Light incident on the image sensor 3 through the lens 1 and the diaphragm 2 is photoelectrically converted into an electric signal, sample-held by the sample-hold circuit 4, and the AGC / γ circuit 6
Performs AGC and γ processing, and the luminance signal Y and the color difference signal R-
Separately output to Y and BY. The luminance signal Y of the output of the AGC / γ circuit 6 is input to the aperture correction circuit 17, where an aperture correction signal is generated. The aperture correction signal is a low-luminance aperture correction suppression circuit 18
When the Y signal is low at -1, it is suppressed, and the adder 8 adds the signal to the Y signal. The added signals are set up by the setup level circuit and input to the encoder circuit 10. The chroma signal C output from the AGC / γ circuit 6 is color-suppressed by the low-luminance color suppression circuit 7 when the Y signal is low, and is input to the encoder circuit 10. The encoder circuit 10 generates a composite video signal from the input Y signal and C signal, and outputs it from the composite video signal output terminal 11.

Next, the features of this embodiment will be described. An iris driver circuit 12 drives the diaphragm 2 from an output signal of the sample hold circuit 4 through an iris photometry circuit 13. When the diaphragm 2 is driven, the iris encoder 14 that detects the diaphragm state value detects the diaphragm value, and it can be seen that the diaphragm is open. Further, the AGC gain can be detected from the output signal of the AGC / γ circuit 6 and the output signal of the AGC photometry circuit 16, and the low brightness determination circuit 15 has a low aperture because the diaphragm is open and the AGC gain is high. Determine that. When the low brightness determination circuit 15 determines that the brightness is low, the determination signal is input to the low brightness color suppression circuit 7, the low brightness aperture correction suppression circuit 18-1 and the setup level circuit 9. Then, here, color suppression and aperture correction suppression are performed according to the luminance signal level to prevent image quality deterioration due to noise. In this embodiment, when the gain-up switch 19 which is an external switch designates the gain-up mode, the gain-up determination circuit 20 determines the gain-up, and the determination signal is input to the low-luminance aperture correction suppression circuit 18-1. It

The low-brightness aperture correction suppression circuit 18-1 operates so as to optimize the suppression of the aperture correction when the gain is increased and the brightness is further lowered. The characteristics of the low-brightness aperture correction suppression circuit are shown in FIG. The gain correction amount of the same low luminance signal level is changed as shown in FIG. 2 when the gain up switch 19 is normal and when the gain is increased, that is, the aperture correction suppression amount when the gain is increased is made larger than in the normal state. As a result, it is possible to prevent the aperture correction signal from being excessively attached to the noise when the gain is increased, and it is possible to obtain an image quality with good S / N even when the gain is increased. In addition, the aperture correction suppression will not be too high in the normal state, and the blurred low-illuminance image quality will not occur. As described above, in this embodiment, since the low-luminance aperture correction suppression can be individually changed in the normal state and the gain-up state, optimal low-luminance aperture correction suppression can be obtained and the image quality can be improved. (Second Embodiment) FIG. 3 shows a "video camera" according to a second embodiment.
It is a block diagram of. In the present embodiment, as shown in the figure, the setup level circuit 9-1 includes a gain up switch 1
It is configured so as to be controlled according to the switching of 9.
Other configurations are similar to those of the first embodiment.

Specifically, the setup level circuit 9-1
Is configured such that, when the gain-up switch 19 is switched to the gain-up side, the setup level becomes higher than when the setup level was switched to the normal side.

For this reason, it is possible to eliminate black sunkenness in the gain-up state, and to reduce flare-like images in the normal state, thus improving the image quality.

(Third Embodiment) FIG. 4 is a block diagram of a "video camera" according to a third embodiment. In the present embodiment, as shown in the figure, the low-luminance color suppression circuit 7-1 is configured to be controlled according to the switching of the gain up switch 19. Other configurations are the same as those in the second embodiment.

More specifically, the low-luminance color suppression circuit 7-1 is configured so that when the gain-up switch 19 is switched to the gain-up side, the color suppression amount becomes larger than when the color-suppression amount was switched to the normal side. .. FIG. 5 shows the color suppression characteristic.

For this reason, the color noise in the gain-up state becomes inconspicuous, and an unnatural image with no color does not occur in the normal state, and the optimum image quality can be obtained.

[0026]

As described above, according to the present invention,
The image quality is improved in the image pickup apparatus provided with the gain increasing means. In particular, according to the invention of claim 1, the S / N ratio in the gain-up state is improved, and the blurring and low-illuminance image quality does not occur in the normal state. According to the second aspect of the present invention, black sunkenness in the gain-up state is eliminated, and flare-like images in the normal state are reduced. According to the third aspect of the invention, the color noise in the gain-up state becomes inconspicuous, and an unnatural image with no color in the normal state does not occur.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment.

FIG. 2 is an explanatory diagram of the first embodiment.

FIG. 3 is a block diagram of a second embodiment.

FIG. 4 is a block diagram of a third embodiment.

FIG. 5 is an explanatory diagram of the third embodiment.

FIG. 6 is a block diagram of a conventional example.

[Explanation of symbols]

 5 Amplifier Circuit 18-1 Low Luminance Aperture Correction Suppression Circuit 19 Gain Up Switch 20 Gain Up Judgment Circuit

Claims (3)

[Claims] 1. A gain increasing means for increasing the gain of a video signal output from an image pickup means, a switching means for switching the gain increasing means to either a normal state or a gain up state, and when the luminance signal level is low. An image pickup apparatus comprising: a low-brightness aperture correction suppressing means for suppressing an aperture correction signal, wherein the low-brightness aperture correction suppressing means, in accordance with switching of the switching means,
An image pickup apparatus, which is controlled such that a suppression amount is larger in a gain-up state than in a normal state. 2. A gain increasing means for increasing the gain of a video signal output from the image pickup means, a switching means for switching the gain increasing means to either a normal state or a gain up state, and a black level of the video signal. An imaging apparatus having a setup level means for determining,
The image pickup apparatus, wherein the setup level means is controlled so that the setup level becomes higher in the gain up state than in the normal state according to the switching of the switching means. 3. A gain increasing means for increasing the gain of a video signal output from the image pickup means, a switching means for switching the gain increasing means to either a normal state or a gain up state, and when the luminance signal level is low. An image pickup apparatus comprising: a low-luminance color suppressing unit that suppresses a color signal, wherein the low-luminance color suppressing unit is responsive to the switching of the switching unit, in the gain-up state, an amount of suppression higher than that in the normal state. The image pickup apparatus is characterized in that it is controlled to be large.