JPS6052171A - Image pickup device - Google Patents

Abstract

PURPOSE:To expand the dynamic range of an optical signal possible for being transduced to an electric signal by using an optical filter means, transducing logarithmically optical intensity to input to an image pickup element. CONSTITUTION:The optical filter means consists of half mirrors 4, 5 arranged at a prescribed interval on a straight line to a direction to which an incident light L is made incident. The optical filter means converts the light intensity of the incident light L logarithmically and outputs light having plural different light intensity. The light having different intensity from the half mirrors 4, 5 is fed to CCD2a-CCD2c respectively as image pickup elements. The electric signal converted at each CCD is given respectively to an adder 6, where the signals are added. The dynamic range of the optical signal possible for being transduced into electric signals is expanded in the the way of the processing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an imaging device, and particularly to a charge-coupled device (hereinafter referred to as a CO
The present invention relates to an imaging device, such as a television camera or an electronic camera, which uses an image sensor (referred to as D) as an imaging device, and is configured to logarithmize the input/output characteristics of the imaging device to widen the dynamic range.

[Technical background of the invention and its problems]

In recent years, CC has been used in television cameras, electronic cameras, etc.
A device used as a D@ image sensor has been developed.

As is well known, a CCD stores charges in a potential well created in a semiconductor, and transfers them along the semiconductor surface by applying a transfer voltage from the outside and sequentially moving the lowest potential position, thereby accumulating signals. This is a functional element that has both a scanning function and a scanning function. When a CCD is used as an image sensor, a charge proportional to the intensity of light incident on the light-receiving surface is stored in each potential well as an image signal.

The relationship between the output level and the input intensity of light incident on this CCD is shown in Figure 1. If the horizontal axis is on a logarithmic scale, the output level increases linearly as the input intensity increases. At , the output level becomes saturated and becomes a constant value. In this figure, the range of input intensity from the noise level N to the saturation level S indicates the dynamic range of the COD (indicated by a code). Normally, this dynamic range D is about 30 dB.

By the way, the dynamic range generally required for imaging is 60 to 90 dB, so in conventional imaging devices using COD, the necessary intensity range of incident light falls within the above-mentioned 30 dB dynamic range. There was a problem in that the incident sight had to be adjusted by adjusting the aperture.

[Purpose of the invention]

In view of the above-mentioned points, the present invention logarithmizes the input/output characteristics of an image sensor, thereby expanding the dynamic range of an optical signal that can be converted into an electrical signal. It is an object of the present invention to provide an imaging device that can easily electrically control the aperture and the dynamic range in the fourth stage path.

[Summary of the invention]

The imaging device of the present invention logarithms the intensity of incident light,
An optical filter means that outputs a plurality of different light intensities is configured, a plurality of lights of different intensities are received from the medium using a plurality of image pickup devices, and the converted electrical outputs are added by an adding means. By doing so, an electric signal with an expanded dynamic range is obtained, and this signal is processed in a subsequent circuit so that the aperture and dynamic range can be controlled electrically.6 [Embodiments of the Invention] Hereinafter, the present invention will be described in detail based on the drawings.

FIG. 2 is an explanatory diagram showing the basic concept of the imaging device of the present invention.

In this figure, reference numeral 1 is a nonlinear filter with a transmission characteristic such that the intensity of transmitted light is 1 Jol (x + 1) with respect to the intensity X of incident light.
By arranging the element row 2 on the light receiving surface, it is possible to obtain an electric signal with an expanded dynamic range from the CCD 2.

FIG. 3 shows an example of a specific configuration of the imaging device according to the present invention, in which a half mirror 4 tilted at 45° with respect to the direction of the incident light is provided behind the photographic lens 3 into which the incident light is incident.
, 5 are arranged on the same straight line and spaced apart from each other by a predetermined pressure. Here, each of the half mirrors 4 and 5 has a characteristic that the difference in intensity between the reflected light and the transmitted light is a little less than 130 dB. A CCD 2 a is arranged in a direction perpendicular to the direction of incident light corresponding to the half mirror 4, a CCD 2 b is arranged in a direction perpendicular to the direction of the incident light corresponding to the half mirror 5,
CCD 2 c behind the half mirror 5 in the direction of the incident light
is located. Each CCD 2a, 2b.

2C has a dynamic range of 30dB.

The outputs of the CCDs 2a, 2b, and 2c are input to an adder 6, and the adder 6 is configured to provide an added output at its output terminal 7.

In such a configuration, the incident light passes through the photographing lens 3, part of it is reflected by the half-mirror -4, and part of it is transmitted. The light reflected by the half mirror 4 is received by the CCD 2a, while the transmitted light is incident on the half mirror 5.

The light reflected by the half mirror 5 is received by the CCD 2b,
The transmitted light is received by CCD'2c. half mirror
If the reflected light of 4 is OdB, the transmitted light is -30 dB.
Therefore, the reflected light from half mirror 5 is -30 dB.
Then, the transmitted light that passes through the half mirror 5 -j, (,p) becomes -60aB. Therefore, the three CCD
2a.

The intensity of the light received at 2b and 2c is OdB.

-30dB, -60dB, each CCD2a, 2b
.

OdB detected at 2C, -30dB, -60c!
The symbol D is input to the adder 6 and added. In this case, each CCD 2a, 2b for the intensity X of the incident light.

The input/output characteristics of 2C are expressed as shown in FIG. However, the input X on the horizontal axis in FIG.
The broken line shows the input/output characteristics of CCD2c. Therefore, the addition output obtained at the output terminal 7 is an output having a logarithmic characteristic of lo, 9 (3:+1) with respect to the input X (logarithmic scale), as shown in FIG.
It will have a dynamic range of 90 dB.

In addition, in the above device, the number of CCDs and the half mirror
By increasing the number of ccDs, the dynamic range can be further widened, and instead of a half mirror, the sensitivity of the C and CD itself may be lowered to -30 dB and -60 dB to reduce the noise of the ccD.

In order to electrically control the aperture (gain control) and dynamic range by transmitting the output whose dynamic range has been expanded in this way to the subsequent circuit, the following will be described.

In this case, controlling the diaphragm is to vary the intensity X of the incident light, so if the input intensity is X and variable magnification is used,
Electrically subtract (or add) the DC voltage of lo9 A
Then, as shown in Figure 6, move the graph showing the input/output characteristics of log(r+1) parallel to the y-axis, and then perform detection to extract only the output that is thicker than the zero level. It's a good thing. In FIG. 6, symbol y1 indicates a portion deleted by detection. Also,
As shown in Figure 7, the dynamic range is controlled using log data to match the input range of the display unit (television monitor).
The slope of the graph of (3:+1) is multiplied by 8 and B1o1/(x+
This can be done by doing 1).

Therefore, when controlling the aperture and the dynamic range, the slope of the logarithmic input/output characteristic 11 is changed by changing the dynamic range as shown in FIG. All you have to do is move it and set it as a characteristic.

In this case, the output y is the displayable range Y on the display device
The aperture and dynamic range may be adjusted so that the input X matches the input range X that is desired to be displayed.

For this reason, in order to control the aperture and the dynamic range, a circuit configuration as shown in FIG. 9 may be used.

That is, in the process in which the incident light passes through the CCD section 8 having logarithmic characteristics and is input to the adder 6, the gain of the adder 6 is controlled by the gain control section 9, which changes the control voltage (variable negative voltage - ■ voltage division). The aperture control can be performed by controlling by
The signal is input to the dynamic range control section 11 and the dynamic range is controlled to match the input range of the display section 12 by varying the attenuation rate (variation of the resistor voltage division ratio).

Furthermore, in order to carry out automatic aperture control, an automatic gain control (AGC) circuit may be added to the circuit configuration shown in FIG. 9 to obtain a circuit configuration as shown in FIG. 10.

In FIG. 10, the output from the detection unit 1o shown in FIG. AGC voltage) is obtained and inputted as negative feedback to the adder 6. In this case, the amount of automatic aperture is made possible by varying the amount of negative feedback, and the response speed of the automatic aperture is made possible by changing the cutoff characteristic of the low-pass filter 13.

In addition, the above-mentioned aperture control and automatic aperture control.

Since it is naturally possible to control the dynamic range during playback after recording, it is also possible to adjust the dynamic range while viewing the image on the receiving side in a television camera, or during reception or playback in an electronic camera.

〔Effect of the invention〕

As described above, according to the present invention, the optical filter means is used to logarithmize the light intensity and input it to the image sensor, so that the optical signal has logarithmic characteristics. The dynamic range of the signal can be expanded, and the aperture can be controlled (variable gain) through electrical processing after conversion.

Automatic aperture control (AGc) and dynamic range control (variable display range) can be easily performed.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram showing the relationship between input intensity and output of an image sensor, FIG. 2 is an explanatory diagram showing the basic concept of the imaging device of the present invention, and FIG. 3 is an implementation of the imaging device according to the present invention. A configuration diagram showing an example, Figures 4 and 5 are characteristic diagrams showing the input/output characteristics of the device shown in Figure 3, and Figure 6 is an explanation showing the principle when controlling the aperture with the device shown in Figure 3. Figure 7 is an explanatory diagram showing the principle when controlling the dynamic range with the apparatus shown in Figure 3, and Figure 8 shows the principle when controlling and displaying the aperture and dynamic range using the apparatus shown in Figure 3. Explanatory diagram showing, No. 9
This figure is a block diagram of an imaging apparatus configured based on the W and theory described in FIG. 8, and FIG. 10 is a block diagram showing a configuration in which an automatic aperture control section is added to the apparatus of FIG. 9. 2a, 2b, 2c = -CCD (J maximum 4g7
4.5... Half mirror (optical filter means), 6... Adder, L... Incident light, Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5

Claims (3)

[Claims] (1) Optical filter means configured to logarithmically change the intensity of incident light and output it at a plurality of different light intensities, and each receive a plurality of lights of different intensities from the optical filter means. What is claimed is: 1. An imaging device comprising: a plurality of imaging devices for converting electrical signals into electrical signals; and an adding means for adding up the outputs of these imaging devices, and the output from the adding means is used as a video signal. (2) The imaging device according to claim 1, wherein the plurality of image sensors are composed of a plurality of charge-coupled devices. (3) The optical filter means is composed of a plurality of half mirrors arranged at predetermined intervals on the same straight line with respect to the direction of the incident light, and these half mirrors sequentially reflect and transmit the light to 3. The imaging device according to claim 1, wherein light of different intensities is obtained and input to the plurality of charge-coupled devices.