JPS63284434A - Color temperature detector - Google Patents

Abstract

PURPOSE:To accurately detect the temperature of light over a wide illuminance range by comparing plural color component levels that incident light contains with a reference level which varies with the illuminance of the incident light. CONSTITUTION:A color component detection part 1 decomposes the incident light into primary color components and converts them photoelectrically to output color signal components SR, SG, and SB. An illuminance detection part 2 detects the illuminance of the incident light and generates a switching signal SS when its intensity decreases a constant value to control a reference signal generation part 3. The generation part 3 outputs reference voltages VR, VG, and VB for detecting the levels of the signals SR, SG, and SB. A comparison part 4 compares the signals SR, SG, and SB with the voltages VR, VG, and VB and an output part 5 outputs color temperature information corresponding to the color temperature of the incident light as a red output signal RC and a blue output signal BC according to comparison signals CR, CG, and SB. Thus, the temperature of the light over a wide illuminance range is accurately detected.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a color temperature suitable for a white balance device of a color television camera, etc., which detects color components in illumination of a subject and automatically performs white balance. This detection device is capable of accurately detecting light within a crowd illuminance range.

[Technology background]

White balance in color television cameras is one of the important signal adjustments. White balance means that the component ratio of the three primary colors red, green, and blue in the illumination of the subject (i.e., the light surrounding the subject) is 1:1:1 for a white subject.
The component ratio of the three primary colors varies depending on the type of lighting, so if the white balance is incorrectly adjusted, the entire image will have a bluish tinge. It has a tinge of tinge and a tinge of red, making it impossible to faithfully reproduce the colors.

Therefore, an outer automatic tracking white balance device has been proposed as a device that accurately and automatically adjusts this white balance (Japanese Patent Laid-Open No. 54-5392
4, Japanese Patent Application Laid-Open No. 55-158792, etc.), these devices detect the peripheral light of the subject using a light receiving system installed separately from the imaging system, and automatically adjust the white balance. In more detail, two or three optical sensors each with a color filter arranged on the front are installed, two or three different color components are detected from the peripheral light, and after logarithmically compressing them, each The configuration is such that the ratio of each color component in the outer peripheral light is detected under equal constraints by taking the difference, and the gain of the color signal amplifier of the imaging system is controlled according to the ratio to perform 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, in the above-mentioned devices, high accuracy is required for the logarithmic compression amplifier in order to deal with peripheral light in a wide illuminance range, and correction circuits such as temperature correction are required, making the device complicated. This led to increased costs and increased costs.

An object of the present invention is to provide a color temperature detection device that can obtain accurate color temperature information over a wide illuminance range.

[Means for solving problems]

The color temperature detection device according to the present invention detects the color temperature of incident light by comparing the levels of a plurality of color components contained in the incident light with a reference level that changes depending on the illuminance of the incident light. It is characterized by what it did.

[Effect]

With this configuration, for example, by lowering the reference level in the case of weak light and increasing the reference level in the case of strong light, it is possible to accurately detect light in a wide illuminance range.

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

〔Example〕

FIG. 1 is a block diagram showing the basic configuration of an embodiment of a color temperature detection device according to the present invention.

In the figure, a color component detection section 1 and an illuminance detection section 2 are as follows:
This is a detection unit that detects the intensity of each color component in the incident light and the illuminance of the incident light.

The color component detection unit 1 separates the three primary colors in the incident light into each component and photoelectrically converts the three primary colors into each component, and outputs voltages corresponding to the charges accumulated in the converter as a red component signal SR, a green component signal SG, and a blue component signal S.
On the other hand, the illuminance detection section 2 detects the illuminance of the incident light and generates a switching signal SS when the intensity becomes below a certain value to control the reference signal generation section 3. It is.

The reference signal generator 3 generates color component signals SR, SG, SB.
Reference voltages VR, VG, and VB for detecting the levels of are supplied to the comparator 4, and the levels of the reference voltages are selectively switched in accordance with a switching signal SS.

Therefore, the comparison unit 4 is supplied with reference voltages VR, VC, and VB at levels corresponding to the illuminance of the peripheral light.

The comparison unit 4 compares the color component signals SR, SG, SB and the reference voltage V.
R, VG, and VB are compared, and the comparison signals CR, CG, and CB are
In this embodiment, the color component signals SR,
Since SG and SB are voltage signals that increase in accordance with the accumulated charge, the length of time it takes to reach the reference voltages VR, VG, and VB corresponds to the intensity of each color component of the incident light.

The output unit 5 outputs color temperature information corresponding to the color temperature of the incident light based on the comparison signals CR, CG, and CB. Since the signal is obtained by converting the intensities of SG and SB into time lengths, compare these time lengths to find the ratio between each color component.
It is configured to output a signal corresponding to the ratio as color temperature information. In this example, the green comparison signal CG
The red comparison signal CR for this signal CGK is based on
and the blue comparison signal CB, and convert them into voltage signals and output them as a red output signal RC and a blue output signal BC, respectively.

Because of the above configuration, it is better to increase the reference voltage when the incident light is strong, and lower the reference voltage when the incident light is weak. A color temperature detection device that can detect the color temperature of incident light within a certain period of time and has a wide dynamic range can be obtained.

Next, the detailed configuration of the block diagram of FIG. 1 will be explained with reference to the circuit diagram of FIG. 2. Note that the same parts as in FIG. 1 will be described with the same reference numerals.

In the figure, the color component detection unit 1 has a diffusion plate 11 that diffuses the incident light that has passed through the light receiving system to eliminate the bias of color information Dt. , green C)
, f(B)O Each color component is extracted by each color y4szl-12,13°14, and the photoelectric converter 15.16.17
photoelectrically converted.

The photoelectric converters 15 to 17 output charges accumulated by photoexcitation as voltage signals, as will be described in detail in FIG.
, becomes SB. Therefore, these color component signals SR, SG
, 8B are voltage signals that increase according to the amount of accumulated charge.

The reset circuit 18 receives a comparison end signal CG from the comparison section 4, which will be described later, and a signal H synchronized with the horizontal synchronization signal of the television.
A reset signal R8 having a constant pulse width of 8 and K is generated, and the photoelectric converters 15 to 17 have their accumulated charges erased by this reset signal R8 and return to their initial states.

The illuminance detection unit 2 consists of an illuminance sensor 21 and a comparator 22 arranged at the rear of the diffuser plate 11 described above, and detects when the intensity of the incident light detected by the illuminance sensor 21 becomes less than the reference value RV. Outputs switching signal SS.

The reference signal generator 3 generates reference voltages VR and VG according to the illuminance of incident light under switching control by a switching signal SS.

VB is output, and the switch 31 selects either the stain voltage V or v2 (v, <v2), and the selected voltage v1 or v2 is passed through a voltage divider 32 consisting of a resistor voltage divider circuit or the like.
and outputs reference voltages V R * V G # V B for red), green @), and blue 01). In this case, each reference voltage is VRxVBsa-! -VG.

The comparison unit 4 compares the color component signals SR, 8G, SR and the reference voltage V.
OP Comparator for red color with amplifier configuration 41. Green comparator 42. It has a blue comparator 43.

The color component signals SR and SB are input to the inverting terminals of the comparators 41 and 43, and the reference voltages VR and VB are input to the non-inverting terminals. On the other hand, the reference voltage VG is input to the inverting terminal of the comparator 42, and the color component signal SG is input to the non-inverting terminal. Therefore, the comparators 41 and 43 are at @H# level until the color component signals SR and SB reach the reference voltages VB and VB, and then at @L level.
The comparator 42 outputs comparison signals CR and CB of "level", and conversely outputs a comparison signal CG of "Lj level" until the color component signal SG reaches the reference voltage VG, and then outputs a comparison signal CG of "@H" level. Output.

Further, the AND circuit 44 outputs color component signals SR, SG, and 8B.
It detects that all of the corresponding reference voltages VR, VG, and VB are different in level, and outputs a comparison end signal CE to the color component detection section 1.
5, the signal obtained by inverting the comparison signal CB by the inverter 46, and the AND condition for each comparison signal.

The output unit 5 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 RC1 and the ratio of the blue component to the green component as a blue output signal BC. A logic circuit consisting of an inverter 51 and AND circuits 52 to 55, switches 56 and 57 that select the red output voltages ER and En2 (ERl (En2) according to the output of this logic circuit, and the blue output voltage El, and En2(En,
<En2) switches 58 and 59 for selecting
It is comprised of smoothing circuits 60 and 61 that smooth the selected red output voltage and blue output voltage, respectively.

The AND circuit 52 performs a logical product of the comparison signal CR and a signal obtained by inverting the comparison signal CG by the inverter 51, and its output becomes a control signal for the switch 56 that selects the output voltage ER1. Further, the AND circuit 53 performs a logical product of the comparison signals CR and CG, and its output becomes a switch 570 control signal for selecting the output voltage ER2. Thus the switch 56
or red output voltage ER1 or LR selected by 57
2 is smoothed by a smoothing circuit 60 and output as a red output signal RC.

The blue color has a similar configuration, and the AND circuit 54 outputs the comparison signal CB.
and the inverted signal of CG, and its output controls a switch 58 that selects the output voltage EB, and the AND circuit 55 performs a logical product of comparison signals CB and CG, and its output controls the switch 59 that selects the output voltage EB2. The blue output voltage EB, t or LR2 selected by the switch 58 or 59 is smoothed by the smoothing circuit 61,
It is output as a blue output signal BC.

The above is the configuration of the embodiment of the present invention.Next, the operation of this embodiment will be explained with reference to the waveform diagram of FIG.

First, time t. When the reset signal R8 is generated (FIG. 3A), the photoelectric converters 15 to 17 are brought to their initial states. After the initial state, the photoelectric converters 15 to 17 generate color component signals SR, SG, and S according to the intensity of each color component of the incident light.
Output B. Now, if the color temperature of the incident light is low,
Each color component signal becomes a signal that maintains the relationship of 5B (SG (SR) and increases with time (FIG. 3B).

At time t, color component No. 3 SG exceeds the reference voltage VG, so the comparison signal CG of the comparator 42 changes from the L state to the H state (FIG. 3C). Here, the reference voltage VC is
As shown in FIG. 2, the voltage is set to v2.

At times t2 and t3, the color component signals SR and S
B are the reference voltages VR and VB (VR, , VB), respectively.
Therefore, the comparison signals OR and CB of the comparators 41 and 43 change from the Ha state to the L state (the third
Diagram and E).

The comparison signals CR, CG, and CB obtained as follows are
A CR for the signal CG is supplied to the output section 5.

Red output signal RC, depending on the ratio of CB to signal CG,
A blue output signal BC is respectively formed.

Next, the operation of the red circuit in the output section 5 will be described.

Time t. -t, is time T1, time t, ~t2 is time T2
Then, at time T1, the AND condition of the AND circuit 52 is satisfied, so the switch 56 is not turned on (FIG. 3F).
), output voltage ER, is supplied to the smoothing circuit 60 (third
Figure H).

Then, at time T2, the AND condition of the AND circuit 53 is satisfied, the switch 57 is turned on (FIG. 3G), and the output voltage ER is supplied to the smoothing circuit 60 (FIG. 3H) at time t2. ．． After that, the AND conditions of AND circuits 52 and 53 are not satisfied, and both switches 56 and 57 are turned off (
3F and G), the input of the smoothing circuit 60 becomes a high impedance state (HIGHZ) (FIG. 3H).

In this way, the signal shown in FIG. 3 is input to the smoothing circuit 60. The smoothing circuit 60 has a large time constant, so when multiple voltage signals with 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, the smoothing circuit 60 outputs the average value according to the supply time of each input voltage. Retains the previous voltage state.

Therefore, the red output signal RC takes a value between the voltages ER and ER2 depending on the time T and T2 at which the output voltages ER and LR2 are input.

To explain this relationship in detail, let us assume that the incident light amount of the photoelectric converter 15 is LR1, the incident light cover of the photoelectric converter 16 is LG, and the respective conversion coefficients are AR%AG, then the color component signals 8R, S
G is expressed as a function of time t, 5R-LR-AR-
t 8G-LG・AG-t Therefore, the signals SR and SG are at the reference voltage V
The time to reach R 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 60 during times T and T2, it can be expressed as follows.

As is clear from equation (1), the red output signal RC has a voltage ER-ER depending on the ratio of the R component and the G component in the incident light.
2. If the R component is small compared to the G component, it approaches the voltage ER2, and if it is large, the voltage E
When the gain approaches R, and the gain of a red signal amplifier (not shown) in the imaging system is controlled, it becomes K.

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, the time T is used as an input signal to the smoothing circuit 61.

At time T2 (time t, ~1.), output voltage El, and output voltage EB2 are supplied (FIG. 3K).

Since all the color component signals exceed the corresponding reference voltages at time t3, the AND condition of the AND circuit 44 of the comparator 2 is satisfied, and the comparison end signal CE is supplied to the reset circuit 18. In this state, when the signal H8 synchronized with the horizontal synchronization signal of the television is applied to the reset circuit 18 at time t4, the reset signal R8 is generated again, and the photoelectric converters 15 to 17 return to the initial state again, and from then on, the same operation is performed. The operation is repeated.

By the way, in such a front state, when the illuminance of the incident light decreases and the output of the illuminance sensor 21 decreases by more than the reference value Rv, the illuminance detection section 2 generates a switching signal SS. The switch 31 switches from the selection of the stain pressure v2 to the selection of V (V, <V, ) according to the switching signal 88I/c], and the reference signal generator 3 generates low-level reference voltages VR, VG. ,V
Output B. It is clear from equation (1) above that even if the reference voltage is switched in this way, the output will not change unless the ratio is changed.

Therefore, if the illuminance of the incident light is reduced and the reference voltage 4 is lowered, the processing time in the comparison section 4 and the output section 5 will not be prolonged, and regardless of the illuminance K of the incident light, the incident light will always be incident at a substantially constant period. The color temperature of the light can be detected and an accurate output signal can be obtained from the smoothing circuit.

The above is the configuration and operation of one embodiment of the present invention.

Next, an example of the photoelectric converter shown in FIG. 2 will be explained with reference to FIG. 4.

In FIG. 4, A is a schematic plan view of a photoelectric converter, and B is a schematic plan view of a photoelectric converter.
is its I-1m sectional view, and C is its equivalent circuit diagram.

In FIGS. 4 and 4B, the optical sensor is formed on an n-silicon substrate 101 and electrically isolated by an element isolation region 102.

The photoelectric sensor includes an n-collector region 103, a p-pace region 1
04 and π consisting of 105 emitter regions 105? - a capacitor electrode 107 for controlling the potential of the p base region 104 by sandwiching the oxidized vX 106 and the transistor;
It is composed of.

Then, the emitter electrode 108, the protective film 109, the n1 region 111 for ohmic contact, and the collector electrode 112.
are formed respectively.

The basic operation of the optical sensor is to first put the p-base region 104 biased at an initial potential into a floating state, and accumulate holes in the p-base region 104 among the electron-hole pairs generated by photoexcitation (accumulation operation). .

Next, a positive voltage is applied to the capacitor electrode 107 to forward bias between the emitter and the paste, and the accumulated voltage generated by the accumulated holes is read out to the floating emitter side (read operation). .

Next, ground the emitter side and connect the capacitor electrode 107.
A positive voltage reset pulse is applied to the p-pace region 10.
By increasing the potential of 4, a current flows from the collector side to the emitter side, and the holes accumulated in the p space region 104 disappear. As a result, the positive voltage for refreshing
When the pulse falls, the p pace region 104 returns to its initial state (refresh operation).

The basic configuration of this optical sensor is disclosed in Japanese Patent Application Laid-Open No. 1986-12.
It is described in Publication No. 759.

FIG. 5 shows another configuration example of a photoelectric converter applicable to the present invention. In the figure, 201 is a Pynox power supply, 202
is a photodiode, 203 is an operational amplifier, 204 is an integrating capacitor, and 2o5 is a reset switch.

As shown in FIG. 5, when the reset signal R8 is input to the reset switch 205, the reset switch 205 closes and the terminal voltage of the integrating capacitor 204 is short-circuited and discharged. When the reset signal R8 ends, the reset switch 2
05 opens, and a photocurrent corresponding to the light incident on the photodiode 202 flows from the z4ias power supply 201 to the photodiode 202.
is stored in the integrating capacitor 204 through the output terminal 2.
06 as a color component signal.

In addition, in the above embodiment, the red @) component of the incident light,
Although the configuration is configured to detect green (6) components and blue components, the present invention is not limited to this, and it may be possible to detect two or four or more color components.

〔Effect of the invention〕

As explained in detail above, the color temperature detection device according to the present invention compares the levels of a plurality of color components included in incident light with a reference level that changes depending on the illuminance of the incident light. By setting the reference level low when the illuminance of the incident light is low, and setting the standard level high when the illuminance of the incident light is high, it is possible to accurately detect the color temperature of light over a wide illuminance range. can.

Therefore, if the present invention is applied to, for example, a light receiving system of an external 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 embodiment of the present invention; Fig. 2 is a circuit diagram showing a circuit configuration of an embodiment of the invention; Fig. 3 explains the operation of the embodiment of Fig. 2. FIG. 4 is a diagram showing an example of the configuration of the photoelectric converter shown in FIG. FIG. 5 is a circuit diagram showing another example of the configuration of the photoelectric converter shown in FIG. 2. 1... Color component detection section, 2... Illuminance detection section, 3...
Reference signal generation section, 4... Comparison section, 5... Output section. Agent Patent Attorney Seki Yamashita Figure 1 Figure 4 (A) Figure 5 Procedural amendment form) % formula % 2. Name of the invention Color temperature detection device 3. Person making the amendment Relationship with the 41G patent Applicant name (100) Canon Co., Ltd. 4, Agent address 40 Mori Building, Toranomon, 5-13-1 Toranomon, Minato-ku, Tokyo (1) ``3. Detailed description of the invention'' in the first line of page 2 of the specification ” and add the item name.

Claims (1)

[Claims] (1) A color temperature detection device that detects the color temperature of the incident light by comparing the levels of a plurality of color components included in the incident light with a reference level that changes depending on the illuminance of the incident light.