JPS63284426A - Photoelectric converting device - Google Patents

Abstract

PURPOSE:To accurately adjust white balance over a wide dynamic range by switching the capacity of a charge storage part according to the illuminance of incident light. CONSTITUTION:A photodetector 1 outputs a current I0 corresponding to the quantity of the incident light and supplies it to the capacitor C1 of the storage part 2. A voltage Ec1 which is proportional to the current I0 and inversely proportional to capacity C1 is sent out of the capacitor C1 through the emitter follower circuit of a transmission part 3. A comparator CP, on the other hand, compares the intensity of the incident light detected by the illuminance sensor Lx of an illuminance detection part 4 with a reference voltage RV and outputs a sensitivity switching signal CS when the intensity of the incident light exceeds RV to turn on a switch element SW, which switches the capacity to C1+C2 to lower the sensitivity, expanding the dynamic range.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a photoelectric conversion device, and particularly to a photoelectric conversion device designed to perform accurate photoelectric conversion even in a wide illuminance range.

[Technology background]

Hereinafter, a description will be given of an example of a whitespace device in a color television camera.

White balance refers to the three primary colors in the lighting of the subject, red (
IO2 refers to adjusting the gain of the camera's color signal so that the component ratio of green (G) and real (B) is 1:1:1 for a white subject.

Since the component ratios of the three primary colors vary greatly depending on the type of lighting, adjusting the white balance to match the type of lighting in a color television camera is one of the important adjustments. If this adjustment is incorrect, the entire TV screen will appear reddish or bluish, making it impossible to faithfully reproduce colors.

In order to accurately and automatically adjust this white balance, an outer automatic tracking type white balance device has been proposed (Japanese Unexamined Patent Application Publication No. 54-53924, Japanese Unexamined Patent Publication No. 55-158792, etc.).

These devices detect the illumination of the subject using a light receiving system provided separately from the imaging system, and automatically adjust the white balance. More specifically, two or three light cells each having a color filter arranged in front are provided, two or three different color components are detected from the incident light, and after logarithmically compressing them, each light cell is The configuration is such that the ratio of each color component in the illumination light is detected under equal constraints by taking the difference, and the gain of the color signal amplifier in the imaging signal processing system is controlled according to the ratio to adjust the white balance.

In such a white balance device, the illuminance range of the light incident on the optical sensor is very wide, so the optical sensor is required to have a correspondingly wide dynamic range.

[Problem that the invention seeks to solve]

However, conventional optical sensors have the problem of not being able to sufficiently cover a wide illuminance range. For this reason, using a conventional optical sensor (why)
When configuring a /4 lance device, high accuracy is required for the logarithmic compression amplifier, and a temperature compensation circuit is also required.
This results in increased complexity and higher cost of the equipment.

An object of the present invention is to provide a photoelectric conversion device that can stably obtain photoelectric conversion output over a wide illuminance range.

[Means for solving problems]

A photoelectric conversion device according to the present invention includes an accumulation section that accumulates charges excited by incident light, a sending section that sends out the accumulated charges as a voltage signal, and an illuminance detection section that detects the illuminance of the incident light. It is characterized in that the capacity of the storage section is controlled by the illuminance detection section.

[Effect]

With this configuration, for example, if the capacity of the storage section is made small in the case of weak light, and the capacity of the storage section is increased in the case of strong light, the output voltage of the converter will be inversely proportional to the capacity of the storage section. Therefore, the sensitivity can be switched depending on the illuminance of the incident light, and light in a wide illuminance range can be accurately photoelectrically converted.

Therefore, when applied to the light receiving system of the external automatic tracking white balance device as described above, it becomes possible to perform accurate white balance adjustment over a wide dynamic range.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an outline of an embodiment of a photoelectric conversion device according to the present invention.

This embodiment has a photodetector section 1 that outputs a current I0 according to the amount of incident light and a storage section 2 having a capacitor configuration, and the capacitance of the storage section 2 is switched by a sensitivity switching signal CS. The charges accumulated in the storage section 2 are sent out from the sending section 3 as a voltage signal. These light detection parts 1.
The storage section 2 and the sending section 3 constitute a photoelectric conversion section 5.

The illuminance detection section 4 generates a sensitivity switching signal C according to the illuminance of the incident light.
generate s. This switching signal C'S controls the capacity of the storage section 2 and switches the sensitivity of the photoelectric conversion section 5.

FIG. 2 is a circuit diagram showing details of the block diagram shown in FIG. 1, in which the same parts as in FIG. 1 are given the same reference numerals.

In the figure, the photodetector 1 is an optical sensor that outputs a current "rot" according to the amount of incident light, and the output type R1° is the storage section 2.
is supplied to the capacitor C1.

Now, if the accumulation time is t-t, then the voltage between the plates of capacitor C1 is E0. It can be seen that this voltage EC1 is proportional to the voltage i16 and the storage time t, and inversely proportional to the capacitance C1.

This voltage EC7 is sent to the outside via the emitter follower circuit of the sending section 3.

By the way, the operating range of the photoelectric conversion section is 100,000 to 100,000 (tu).
x), a dynamic range of approximately F3 Q (dB) is required, but conventional optical sensors cannot provide such a wide dynamic range. Therefore, from equation (1), it can be considered that the dynamic range is widened by changing the capacitance C1t- to switch the υ sensitivity.

Therefore, a switch fR is connected to the storage section 2 in parallel with the capacitor C1.
A series circuit consisting of a child SW and a capacitor C2 is connected. This switch element SW has a ninth sensitivity switching function that expands the dynamic range. The switch element SW is controlled on/off by the sensitivity switching signal C8 from the illuminance detection section 4, and changes the capacitance of the storage section 2 to C1 or C1+C2.
It is switched so that

The illuminance detection section 4 generates a sensitivity switching signal CS,
It is composed of an illumination sensor LX and a comparator CP, and turns on a switch element SW when the intensity of incident light detected by the illuminance sensor LX exceeds a reference voltage RV.

Now, assuming that the sensitivity is switched to -100 when the illuminance is 1000 CLux] or higher, the reference voltage RVO value is set to the output value of the illuminance sensor LX when the illuminance is 1000 CLux, and the switch element SW is set to -Lu
Set it to turn on when it is 13 or higher. At this time, the capacitance of capacitors C4 and C2 is t-C1+C2=100C.

If the setting is made so that the voltage between the plates of the parallel capacitors C1 and C2 becomes EC1+c2. That is,
For the same signal current and accumulation time, the sensitivity is 100 minutes - and the dynamic range is 100 times (40 minutes).
al) will be expanded.

Therefore, when the illuminance of the incident light is high, the switching signal C
S increases the capacity of the storage section 2 and lowers the sensitivity of the photoelectric conversion section, and when the illuminance of the incident light is low, the switching signal C
By reducing the capacitance of the storage section 2 and increasing the sensitivity, a photoelectric converter with a wide dynamic range can be obtained.

Note that the charges in the capacitors C1 and C2 are discharged by a reset circuit (not shown).

Next, an example in which the present invention is applied to a white balance device will be described. FIG. 3 is a circuit diagram of a color temperature detection device forming a part of this device.

In the figure, a color component detection section 10 and an illuminance detection section 20
corresponds to the embodiment of the present invention (FIGS. 1 and 2).

The color component detection unit 10 detects the illumination of the subject, and
This diffuser plate 1lt has a diffuser plate 11 that diffuses incident light that has passed through a light receiving system separate from the imaging system to eliminate unevenness of color information.
-The transmitted light is red (2) and green (G).

Each color component is taken out by each blue (B) color filter 12, 13, 14, and photoelectrically converted by a photoelectric converter 15.16.degree. 17.

The photoelectric converters 15 to 17 are the photoelectric converters 5 of this embodiment.
As mentioned above, current to and accumulation time t
This voltage signal is the color component signal SR, SG.

Output as SR. These photoelectric converters 15 to 17 are
A reset signal R8 synchronized with the horizontal synchronization signal of the television causes the charge in the storage section 2 to be released and reset to the initial state.

The illuminance detection unit 20 is arranged at the rear of the above-mentioned diffuser plate 11 and consists of nine illuminance sensors LX and a comparator CP.When the intensity of the incident light detected by the illuminance sensor LX exceeds the reference value By A sensitivity switching signal CS is output to.

The comparison unit 30 compares the color component signals SR, SG, SB with the reference voltages VB, VG, VB, and outputs the color component signals SR, 8G, 8G,
It detects the time it takes for SB to reach the respective predetermined reference voltages VR, VG, and VB, and the red comparator 31. is configured as an OP amplifier. Green comparator 32. It has a blue comparator 33.

The color component signals 8R and SB are input to the inverting terminals of the comparators 31 and 33, and the reference voltages VR and VB are input to the non-inverting terminals. On the other hand, the reference voltage VQ is input to the inverting terminal of the comparator 32, and the color component signal 8G is input to the non-inverting terminal. Therefore, the comparators 31 and 33 are at mHm level until the color component signals SR and 8B reach the reference voltages VR and VB, and after reaching the reference voltages VR and VB.
Output comparison signals CR and CB at L'' level, and conversely,
The comparator 32 outputs the 1L'' level until the color component signal SG reaches the reference voltage vG, and then outputs the ``''H#H# level signal CG.

The output unit 40 calculates the color component ratio of the incident light based on the comparison signals CR, CG, and CB, and outputs the ratio of the red component to the green component as a red output signal Re, and the ratio of the blue component to the green component as a tube blue output signal BC. A logic circuit consisting of an inverter 41 and AND circuits 42 to 45, and a switch 46 that selects red output voltages ER1 and ER2 (ER, (ER2)) according to the output of this logic circuit.
and 47, the blue output voltage EB, and ER2(EB
I < ER2) t'' select switches 48 and 4
9, and smoothing circuits 50 and 51 that smooth the selected red output voltage and blue output voltage, respectively.

The AND circuit 42 performs a logical product of the comparison signal CR and a signal obtained by inverting the comparison signal CG by the inverter 41, and its output becomes a control signal for the switch 46 that selects the output voltage ER1't-. , t, and the AND circuit 43 performs a logical product of the comparison signals CR and CG, and its output is the output voltage ER2? This becomes the switch 470 control signal to select. The red output voltage ER1 or ER2 selected by the switch 46 or 47 is smoothed by the smoothing circuit 50 and output as the red output signal RC.

The blue color has the same configuration, and the AND circuit 44 outputs the comparison signal CB.
and the inverted signal of Ca, and the output thereof controls a switch 48 that selects the output voltage EB, and the AND circuit 45 calculates the logical product of the comparison signals CB and CG with the inverted signal of Ca. The output voltage EB2 is selected by the switch 49t. The blue output voltage EB1 or ER2 selected by the switch 48 or 49 is smoothed by the smoothing circuit 51 and output as the blue output signal BC.

The above is the configuration of the color temperature detection device to which the present invention is applied. Next, the operation of this device will be explained with reference to the waveform diagram shown in FIG.

First, at time t0, when a reset signal R8 is generated (FIG. 4A), the photoelectric converters 15 to 17 are placed in an initial state. After the initial state, the photoelectric converters 15 to 17 generate color component signals 5Rs8a* according to the intensity of each color component of the incident light.
Output sm. Now, if the color temperature of the incident light is low, each color component signal becomes a signal that maintains the 8B (8G) SR relationship and increases with time (FIG. 4B).

At time t, the color component signal Sa reaches the reference voltage vGt-
Therefore, the comparison signal CG of the comparison comparator 32 changes from the @Lm level to the 1H# level (41st!!'Ic) @The reference voltage VG is set so that VR=VB;HVG. There is.

At times t2 and 1s, the color component signals SR and S
Since B exceeds the reference voltages VB and VB (VR-VB), respectively, the comparison signals CR and CB of the comparators 31 and 33 change from the 1H" level to the @L" level (fourth diagram and E).

Comparison signals CR and CG thus obtained.

CB is supplied to the output section 40 and CR for the signal CG.
, red output signal RC according to the ratio of CB to signal CG.
One idiomatic output signal Be is respectively formed.

Next, the operation of the red circuit in the output section 40 will be described.

Time t. ~t, is time T1, time t, ~t2 is time T2
Then, at time ↑, the AND condition of the AND circuit 42 is satisfied, so the switch 46 is not turned on (FIG. 4 F).
), the output voltage ER1 is supplied to the smoothing circuit 50 (fourth
Figure R).

Then, at time T2, the AND condition of the AND circuit 43 is satisfied, the switch 47 is turned on (FIG. 4G), and the output voltage ER2 is supplied to the smoothing circuit 50 (FIG. 4H). After time t2, the AND conditions of AND circuits 42 and 43 are not satisfied, and switches 46 and 47 are both turned off (FIG. 4, F and G), so that the smoothing circuit 500 Å force is in a high impedance yx state (RIG). I Z ) becomes (4th
Figure H).

In this way, the signal shown in FIG. 4H is input to the smoothing circuit 50. The smoothing circuit 50 has a large time constant, so when a plurality of voltage signals of different levels are input, it outputs the average value according to the supply time of each input voltage, and when the input is in a high impedance state. Sometimes the previous voltage state is maintained.

Therefore, the red output signal RC will take a value between the voltages ER, to ER2 depending on T at which the output voltages ER1 and ER2 are input, and 72 hours.

Next, to explain this relationship in detail, let us assume that the amount of light incident on the photoelectric converter 15 is LR, the amount of light incident on the photoelectric converter 16 is LG, and the respective conversion coefficients are AR and AC, then the color component signal S
R and SG are expressed as functions of time t, and 5R=LR@AR threat t 8G=LG·AQ −t. Therefore, the time for signals i9R and SG to reach reference voltages VR and VG is as follows.

Since the red output signal RC is the average value of the voltages ER1 and ER2 input to the smoothing circuit 50 during the time T and 〒2, it can be expressed as follows.

As is clear from equation (3), the red output signal RC has voltages ER, ~E depending on the ratio of the R component and the G component in the incident light.
This is a signal that changes between R2, and when the R component is smaller than the G component, it approaches the voltage ER2rc, and when it is larger, it approaches the voltage ER, and is used to control the gain of the red signal amplifier in the imaging system (not shown). Become.

The above description has been made regarding the operation of the red color circuit, but the same applies to the operation of the blue color circuit. Although detailed explanation will be omitted, in the case of blue color, time T is used as an input signal to the smoothing circuit 51.

At output voltage EB, , time 〒2' (time t, ~1.)
The output voltage EB2 is respectively supplied at (K in FIG. 4).

In this way, at time t3, when all the color component signals exceed the corresponding reference voltages and are synchronized with the horizontal synchronizing signal of the television and the next reset signal R8 is applied, the photoelectric converters 15 to
17 is returned to the initial state, and the same operation is repeated thereafter.

〔Effect of the invention〕

As explained in detail above, the photoelectric conversion device according to the present invention switches the capacity of the charge storage section according to the illuminance of the incident light. In the case of light, by increasing the capacity of the storage unit, it is possible to accurately photoelectrically convert light over a wide illuminance range.

Therefore, for example, if the present invention is applied to a light receiving system of an outer automatic tracking white balance device.

It becomes possible to perform accurate white balance adjustment over a wide dynamic range.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an outline of an embodiment of this invention, Fig. 2 is a circuit diagram showing a circuit configuration of an embodiment of this invention, and Fig. t43 is a white circuit diagram showing an application example of Jin's invention. FIG. 4 is a circuit diagram showing a color temperature detection device constituting a part of the balance device. FIG. 4 is a waveform diagram for explaining the operation of FIG. 3. l...Light detection section 2...Storage section 3...Sending section 4...Illuminance detection section 5...Photoelectric conversion section Agent Patent attorney Seki Yamashita Figure 1 Figure 2 Decoy

Claims (1)

[Claims] (1) It has an accumulation section that accumulates charges excited by incident light, a sending section that sends out the accumulated charges as a voltage signal, and an illuminance detection section that detects the illuminance of the incident light; A photoelectric conversion device characterized in that the capacity of the photoelectric conversion device is controlled by the illuminance detection portion.