JP2578763B2 - Imaging device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an imaging device.

[Summary of the Invention]

According to the present invention, a weighting circuit used in a video camera or the like is provided with a pair of gain control circuits whose gains change in opposite directions by a control voltage, so that the weighting amount can be freely adjusted without changing the signal level. It is made possible.

[Conventional technology]

The automatic aperture circuit and the AGC circuit of the video camera operate in response to the luminance information of the screen. At this time, an optimal image is obtained by incorporating more luminance information of a specific part of the screen, usually the central part of the screen. There is such a technique. This is called weighting or the like, and the weighting circuit is configured as shown in FIG. 4, for example.

That is, in the figure, (1) shows an image pickup device such as an image pickup tube, CCD, etc., and from this device (1), the luminance of a waveform as shown in FIG. The signal Sa is taken out, supplied to the processing circuit (2), subjected to gamma correction, addition of a synchronization pulse, and the like, and then output to the terminal (3).

Further, the signal Sa from the element (1) is supplied to the gate circuit (11), and the horizontal blanking pulse Pb is sent from the forming circuit (21) to the gate circuit (11) as a control signal as shown in FIG. The luminance signal Sc from which the noise and the step in the horizontal blanking period have been removed is extracted from the gate circuit (11) as shown in FIG. The signal Sc is supplied to the gain control circuit (12), and the variable resistor (22) supplies a gain control voltage to the gain control circuit (12).
V ₂ is supplied from the control circuit (12) is taken out controlled luminance signal Sc level (gain), the signal Sc is supplied to the adding circuit (13).

Further, the signal Sa from the element (1) is applied to the gate circuit (15).
And a weighting pulse indicating this during a period Td for weighting as shown in FIG. D from the forming circuit (21), in this example, a period Td corresponding to the center of the screen.
Pd is supplied to the gate circuit (15) as a control signal, and the portion of the period Sa of the signal Sa during the period Td is extracted as a weight signal Se from the gate circuit (15) as shown by a solid line in FIG. Then, together with the signal Se is supplied to the gain control circuit (16), the variable resistor (26) from the gain control circuit (16) is supplied control voltage V ₆ of the gain control circuit (16) level Is extracted, and this signal Se is supplied to the adding circuit (13).

Therefore, the signal Sf obtained by adding the signal Se to the signal Sc, that is, the luminance signal Sf weighted in the period Td is extracted from the adding circuit (13) as shown in FIG.

Then, this signal Sf is supplied to a detection circuit (14) and, for example, peak value detection is performed, and this detection signal is supplied to an automatic aperture circuit and an AGC circuit (both not shown) to perform automatic aperture and AGC. In this case, the levels of the signals Sc and Se in the signal Sf can be changed by adjusting the variable resistors (22) and (26), so that the response characteristics of the automatic aperture and the AGC can be changed. For example, if the level of the signal Se in the signal Sf is 0, average photometry is performed, and if the level of the signal Se is increased, center-weighted photometry is performed.

[Problems to be solved by the invention]

However, this weighting circuit causes a problem.

That is, for the sake of simplicity, the signal Sa from the element (1) is completely white (100% level) as shown in FIG. 6A.
And Then, as shown in FIG. B, the voltage V _2,
During a certain period, the level of the signal Sc is set to 100%,
Period, is 50% to, also, the drawing by the voltage V ₆ C
As shown in the figure, during the period, the level of the signal Se is 100%
It is assumed that the period is set to 50%.

Then, since the signal Sf is an addition signal of the signals Sc and Se,
As shown in FIG. D, the period, (or,)
As described above, the level of the signal Sf changes depending on the ratio between the signals Sc and Se in the signal Sf. Further, the ratio between the signal Sc and the signal Se in the signal Sf is the same between the periods, but the level of the signal Sf is different. Therefore, in the above-described weighting circuit, a signal Sf having a different level is generated even if the weighting ratio changes or the weighting ratio is the same.

When the weighting circuit described above is integrated into an IC, the variable resistors (22) and (26) are externally connected,
_Two pins are required to supply V ₂ and V ₆ , which is disadvantageous for IC implementation.

The present invention seeks to eliminate these problems.

[Means for solving the problem]

The present invention relates to an image sensor (1), means for generating a control voltage according to a photometry mode, and a first gain amplifier for controlling a gain of a luminance signal obtained from the image sensor (1) according to the control voltage. A circuit (12), a gate circuit (15) for extracting a signal of an arbitrary period from the luminance signal, and a second gain amplifier circuit (16) for controlling the gain of the signal extracted from the gate circuit (15) according to the control voltage. ) And the first gain amplifier circuit (12)
And an adder circuit (13) for adding the output of the second gain amplifier circuit (16) to the output of the second gain amplifier circuit (16). The gains of the gain amplifier circuits (16) are differentially changed from each other, and
An image pickup apparatus characterized by obtaining a control signal controlled so that the output signal level from 3) is always constant.

[Action]

According to the weighting circuit of the present invention, the gains of the two gain control circuits (12) and (16) are changed differentially with each other by the control voltage V ₂ , and the two gain control circuits (12) and (16) Even if the ratio of the obtained signals Sc and Se is changed, a constant signal is obtained in which the level of the signal Sf of the addition output in the addition circuit (13) does not change.

〔Example〕

In FIG. 1, the control voltage V ₂ from the variable resistor (22)
And the voltage V ₂ is supplied to the gain control circuit (12), (1
6) Commonly supplied. However, in this case, the gain control circuit (12) and (16), the gain is configured so as differentially varied to each other with respect to the change of the voltage V _2, for example, a voltage
When the gain of the circuit (12) is increased by an increase in V _2, the gain of the circuit (16) is set smaller.

In such a configuration, the signal Sa is all white (100% level) as shown in FIG. 2A. Then, as shown in FIG. B, the level of 100% of the signal Sc in the period-by voltage V _2, 50% if was controlled to 0%, this time, the control circuit (12), (16) Since the gains change differentially with each other, the level of the signal Se is controlled to 0%, 50%, and 100% during the period 1 to 3 as shown in FIG. Therefore, the signal S
f becomes as shown in FIG. D, and the level of the signal Sf does not change even if the ratio of the signals Sc and Se in the signal Sf changes. Also,
If the ratio between the signal Sc and the signal Se in the signal Sf is the same, the level of the signal Sf is uniquely determined, and does not become several levels.

Therefore, the weighting ratio can be freely changed without changing the level of the signal Sf. Furthermore, it is only one control voltage V _2, therefore, when formed into an IC, can be reduced by one the number of pins.

FIG. 3 shows a specific example of the gain control circuits (12) and (16) and the adder circuit (13), and the portion enclosed by a chain line is integrated into one IC.

That is, the transistors Q _21, Q ₂₂ and transistor Q _23, Q ₂₄ as a load is configured differential amplifier (42), the transistor Q ₃₃ signal Sc from the gate circuit (11) through the differential amplifier (42), Q Supplied to ₃₄ . Similarly the transistors Q _63, Q ₆₄ transistors Q ₆₁ as a load, the Q ₆₂ is configured differential amplifier (46), the transistor Q ₃₅ signal Se from the gate circuit (15) through a differential amplifier (46), Q
Supplied to ₃₆ .

Then, the transistors Q ₃₃ to Q ₃₆ are intended to constitute a multiplying circuit (33) transistors Q _31, Q ₃₂ which are differentially connected as a constant current source, a signal from the collector of the transistor Q _34, Q ₃₆ Sc a signal Sf that the Se is added is taken, the signal Sf is supplied to the detection circuit (14) through the transistor Q _37.

And in this case, the control voltage from the variable resistor (22)
V ₂ is supplied to the base of the transistor Q _32.

Therefore, when the control voltage V ₂ is high, small collector current of the transistor Q _31, the collector current of the transistor Q ₃₂ is large, along with the gain of the transistor Q _33, Q ₃₄ decreases, the gain of the transistor Q _35, Q ₃₆ Becomes larger, the level of the signal Sc in the signal Sf becomes smaller, and the signal Se becomes smaller.
Level increases (period in FIG. 2). Conversely, when the control voltage V ₂ is low, large collector current of the transistor Q ₃₁ is, the collector current of the transistor Q ₃₂ is small, with the gain of the transistor Q _33, Q ₃₄ is increased, the transistor Q _35, Q The gain of the signal ₃₆ decreases, the level of the signal Sc in the signal Sf increases, and the level of the signal Se decreases (period in FIG. 2).

Therefore, the signal Sf is obtained made of weighted as desired by the control voltage V _2, the level of the signal Sf is constant regardless of the voltage V _2.

In the above description, the control circuits (12) and (16) have the same configuration, and the control circuits (12) and (16) have control voltages that change differentially with each other.
V ₂ , ₂ may be supplied, in which case voltage ₂ is equal to voltage V ₂
From within the IC.

〔The invention's effect〕

Since the gains of the gain control circuits (12) and (16) change differentially with each other, even if the weighting ratio is changed, the signal Sf
Level does not change. Also, the weighting ratio can be controlled by one control pin, which is suitable for IC implementation.

[Brief description of the drawings]

FIG. 1 is a system diagram of an example of the present invention, and FIGS. 2 to 6 are diagrams for explanation thereof. (12) and (16) are gain control circuits.

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Ryuichiro Kawai 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (56) References JP-A-59-61283 (JP, A)

Claims (1)

(57) [Claims] An image pickup device, means for generating a control voltage according to a photometry mode, a first gain amplifier circuit for controlling a gain of a luminance signal obtained from the image pickup device according to the control voltage, A gate circuit for extracting a signal for an arbitrary period from the luminance signal; a second gain amplifier circuit for controlling a gain of the signal extracted from the gate circuit according to the control voltage; an output of the first gain amplifier circuit; An adder circuit for adding an output of the second gain amplifier circuit, wherein a gain of the first gain amplifier circuit and a gain of the second gain amplifier circuit are different from each other with respect to a change in control voltage. An image pickup apparatus which obtains a control signal which is controlled so that the output signal level from the adder circuit is always constant.