JPH0642721B2 - Imaging method - Google Patents

Description

The present invention relates to an image pickup system using a nondestructive readable image pickup means.

In particular, the present invention relates to an image pickup system capable of appropriately processing the output of an image pickup means having a large dynamic range.

[Prior Art] Various imaging devices capable of nondestructively reading an imaging signal have been considered. A typical example of such an element is an image pickup element using an electrostatic induction transistor or a bipolar phototransistor.

Each pixel of such an image pickup device has an advantage that the dynamic range is extremely large because it has a width increasing function.

Therefore, there is an effect that an image pickup signal can be obtained from a very dark subject to a bright subject without requiring special illumination or the like.

[Problems to be solved by the invention]

However, even if the image pickup means has a large dynamic range, the signal processing system for processing the dynamic range has a drawback that it cannot cope with the dynamic range. Therefore, conventionally, the output of the image pickup means is simply attenuated by an attenuator and processed. However, this has a drawback that the S / N of a signal with a small level deteriorates.

It is an object of the present invention to provide an imaging method capable of solving the above-mentioned drawbacks of the prior art.

Moreover, it aims at providing the imaging system suitable for still image imaging.

[Means for solving problems]

In the image pickup system of the present invention, a detection step for detecting the level of a predetermined image signal in a nondestructive readable image pickup means, a gain adjustment step for adjusting the output gain of the image signal according to the level of the image signal, and the gain After the adjustment step, the image signal is read out from the image pickup means again, and the processing step for performing signal processing with the gain is included.

[Action]

An image signal is once formed by a nondestructive readable image pickup means, and this is read to detect the level. In this state, the subject brightness is considered to be within the dynamic range of the image pickup means.

Next, adjust the gain of the signal processing system according to this level,
The output of the image pickup means can be processed at the optimum operating point of the signal processing system.

After that, the image signal is read again from the image pickup means and processed in the signal processing system.

On the other hand, the output of the image pickup means has the best S / N and can be processed in a form with less distortion and the like, and an image signal suitable for print processing can be obtained.

〔Example〕

 The present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a configuration example of an image pickup apparatus according to the present invention, in which 1 is an image pickup element of a video camera, 2 is an AGC circuit for adjusting a gain of an output signal from the image pickup element 1, and 3 is an image pickup element. 1 is a driver circuit, 4 is a clock circuit which generates a clock signal at a timing corresponding to a standard television speed, and 5 is an integrating circuit which integrates the luminance signal via the AGC circuit 2 in synchronization with the clock signal,
Reference numeral 6 is a comparator for comparing the integration result of the integration circuit 5 with two reference levels, 7 is a register for temporarily storing gain data output from an operation circuit 8 described later, and PS is provided separately from the image sensor 1. Light receiving element for photometry, LM is a photometric circuit that calculates subject brightness based on the output of the light receiving element, 8 is an arithmetic circuit that calculates gain data based on the output of the comparator 6, and 9 is a system controller (hereinafter referred to as a system controller). (Abbreviated) 10 is a trigger switch.

Further, 11 is an exposure control means including a diaphragm and a shutter,
Reference numeral 12 is a signal processing circuit which processes the signal passed through the AGC circuit 2 to form a standard television signal such as an NTSC signal. Reference numeral 13 is a recording circuit.

With such a configuration, the operation will be described based on the flow of FIG. Now, set the trigger switch 10 (not shown) to # 10.
When turned on at 0, the expected gain data G = from the arithmetic circuit 8
G ₁ , n = 1 is stored in the register 7 (# 101).
Further, the exposure control means 11 controls the amount of light incident on the image pickup device 1 according to the exposure control data from the syscon 9 based on the output of the photometric circuit LM, and accumulates the information signal (# 10).
2). After that, the exposure control means shields the image sensor from light by the control signal from the syscon (# 103), and this information signal is read (# 104). Then, the luminance signal in the above information signal via the AGC circuit 2 is integrated in the integrating circuit 5 in synchronization with the clock signal from the clock circuit 4 (# 105), and the result of the integration is compared by the comparator 6 with the reference level. Compared to. That is, the comparator 6 determines whether or not the integration result of the luminance signal is within a predetermined range. Specifically, the output Ls of the comparison circuit is at a high level (H) if Lmin is less than or equal to the reference value where the lower threshold level is Lmin and the upper threshold level is Lmax, and Hs is at a high level (Lmin or more). H).

The arithmetic circuit 8 calculates the next gain value G _{n + 1} of the AGC circuit 2 as G _n +.
It is calculated by (sgn) × ΔG / 2 ² . here,
G _{n + 1} , G _n and ΔG are logarithmic representations of the gain, and G _{n + 1}
Is the next gain, G _n is the current gain, and ΔG is the variable range of the gain, which is set to a constant value. Also, (sgn) is L
When the s level is a high level (H), (sgn) =-1,
It is a function such that (sgn) = 1 when the Hs level is high. n is an integer (# 106 to # 110). In this way, the gain of the AGC circuit 2 is optimally controlled by the bisection method (# 111). When both Hs and Ls are low level, that is, when the output of the image pickup device 1 from the output of the integrating circuit 5 is between Lmin and Lmax, that is, in the proper range, the gain G ₁ is maintained.

After that, the same image information is read again from the non-destructible image sensor 1 (# 112). At this time, since the exposure control means shields the element 1 from light, the image information is hardly changed.

The level of the read image information is within the dynamic range of the process processing circuit because the gain has already been adjusted in the AGC circuit, and is recorded after being corrected or KNEE corrected at the optimum operating point. It is recorded as a still image in the circuit 13.

In the above embodiment, the reading of the output signal from the image pickup device 1 may be performed at a faster speed during photometry than during recording.

As described above, in this embodiment, when the level of the amount of light incident on the image pickup device 1 is the initial exposure amount, it may be too high and saturated, or conversely, it may be too low and unmeasurable. The next exposure amount of the image pickup device 1 is logarithmically regulated to an appropriate range by the bisection method. Therefore, the time required for the level of the output signal of the image pickup device 1 to fall within the range in which the amount of incident light can be estimated can be shortened.

Further, when the amount of incident light from the output signal of the image sensor 1 can be estimated, the level range of the output signal of the image sensor 1 can be calculated and obtained.

Therefore, according to this embodiment, the time required for the entire photometry is shortened, and the amount of incident light can be obtained in a short time. Moreover, since it is not necessary to employ another photometric means such as SPC or a mechanical structure such as a mechanism for controlling the diaphragm,
The video camera can be made compact, and the operability is excellent because it is enough to operate the photometric switch.

〔effect〕

According to the present invention, the signal of the image sensor having a wide dynamic range can be recorded at an optimum level in an extremely short time, and the shutter timing of still image capturing can be released as compared with the conventional one using the ALC circuit. Never.
Moreover, since the process can be processed at the optimum operating point as compared with the one in which the output of the image sensor is always attenuated and the process is processed, the gradation of the image can be appropriately reproduced.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a flow chart of the embodiment.

Claims (1)

[Claims] 1. A detection step for detecting the level of a predetermined image signal in a non-destructive readable image pickup means, a gain adjustment step for adjusting the output gain of the image signal according to the level of the image signal, and the gain adjustment step. After that, the image pickup method has a processing step of reading the image signal again from the image pickup means and performing signal processing with the gain.