JPS62107593A - White balance unadjustment compensation circuit - Google Patents

Abstract

PURPOSE:To correct the white balance of an automatic following type if white balance setting is not executed by selecting a fixed or variable white balance correction signal in accordance with a selective operation and giving priority to the variable white balance correction signal so as to select when a fixed type white balance correction circuit is not adjusted. CONSTITUTION:A selection circuit C selectively derives the variable white balance correction signal and the fixed one if a flip-flop 20 is set and reset, respectively, and gain-controls both color level control circuits 8 and 9. The flip-flop 20 is preset by turning on a power source, reset by starting a white balance setting operation to set by switching to an automatic position P1. Accordingly even if a selection switch SW is set at any positions after the power source is turned on, the fixed type white balance is executed unless the white balance correction of the automatic following type is carried out and the operation is set to the automatic position P1 after white balance setting is done.

Description

DETAILED DESCRIPTION OF THE INVENTION A) Field of Industrial Application This paper relates to a white balance correction circuit for a color video camera.

(b) Conventional technology There are two types of white balance correction for color video cameras: fixed type and tracking type.

Fixed white balance correction circuits have been used in many color video cameras in the past, and detect two types of color difference signal levels when a white lens cap is attached or when a white subject is imaged, and calculate the level. By latching the white balance correction signal such that 0 becomes 0, the gain of the color level control circuit is thereafter fixedly defined based on this latch output.

In addition, the automatic tracking type white balance correction circuit that is becoming popular in recent video cameras is
Publication No. 86 (: As shown.

In this method, two light-receiving elements equipped with color filters of different colors are arranged facing the subject, and by comparing the light-receiving output levels, the color temperature is detected and a white balance correction signal is derived. This circuit constantly detects color temperature, which can change from moment to moment, and always performs optimal white balance correction.

Each of the two types of white balance correction circuits described above has its own advantages, and it is desirable that they be selectable depending on the shooting condition.

Therefore, we decided to use a camera-integrated VTR manufactured by Matsushita Electric Industrial Co., Ltd.
“The NV-M3 has two types of white balance correction circuits, automatic (tracking type) and fixed, to selectively switch between the two types of white balance correction circuits mentioned above.
Position (: Equipped with a switchable method selection switch.

(c) Problems to be Solved by the Invention However, in the conventional example described above, if the user sets the method selection switch to the fixed side without performing the white balance setting operation, an incorrect white balance correction signal may be generated. As a result, the white balance will be completely disrupted.

In view of the above-mentioned points, the present invention provides: 1 selection operation: selecting the fixed or variable white balance correction signal accordingly; The present invention is characterized in that a selection circuit is provided that preferentially selects the variable white balance correction signal at the time of adjustment.

Therefore, according to the present invention, when the method selection switch is set to the fixed side without setting the white balance, the variable white balance correction signal is selected, and the white balance becomes a tracking type.

(f) Example The following will explain an example in which the date of publication can be illustrated.

As shown in FIG. 1, the first embodiment includes a fixed white balance correction circuit (Al) and an automatic tracking white balance correction circuit IBI, and white balance correction is performed using a fixed white balance correction signal only when setting the white balance. It is something that is done.

First, myself! ItI'I tracking type white Bakunsu'hli city circuit prisoner) is.

”National T1110hniQal E
xport”l101.31N01F61), 198
The video shows a concentrator (1) consisting of two photodiodes each having a red filter and a blue filter arranged in front, respectively, using a well-known circuit disclosed in detail in P2O-97 of No. 5. The front C of the camera is fixed, and a variable white balance correction signal is derived based on the photoelectric conversion output C. That is, the red photoelectric conversion current 1r, the blue photoelectric conversion current 1'b, the red control voltage yr, and the blue control voltage v'
What is the relationship with b?

Vr −Kr (kT/(1) j; hL I b/
I rlVorVb-K 1) (kT/q) MuI
r/r b+yQ b (where Kr, Kl are constants, vor, yo'b are bias voltages). Therefore, each photoelectric conversion current is the first one. Second logarithmic amplifier +21 (
3) is input.

This logarithmically amplified output V1. V2 is V''' (k T/q) mI rV2 m(c
r/q) #o xb and the first stage of the first stage. By inputting the second differential amplifier (4051C), its outputs V15 and V4 are.

v+5-Kr(kT/q)Th xr7rb +vor
-vrv4-Kb(kT/q)mu xb/kr +vo
b=vb. Therefore, the red control voltage is derived from the first differential amplifier (4), and the blue control voltage is derived from the second differential amplifier (5) as a variable white balance signal.

On the other hand, the video camera inputs the imaging output of the 00D solid-state image sensor (6) to the process circuit (7) to derive a red signal (rl and luminance signal) and a blue signal (b). Red lights and green lights are respectively 1st. 2nd cup level control circuit (
The signal is input to 81 (91) and adjusted to an output level "f:,:A" for white balance correction, and is input to a matrigesses circuit (10) together with the post-secondary luminance signal, where it is converted into one color difference signal.

In addition, this embodiment is equipped with a fixed white balance correction signal (Bl), a red signal [rl] after level control, and a blue signal [bl
and the luminance signal V1 respectively. Second. It inputs to the third detection circuit 11 (13) and performs peak detection of each 4IIF level. This detection output is
It is input to the comparison circuit σ41α9, and from the first comparison circuit (
A first comparison output corresponding to the detection output of the color difference signal (ry) is derived from the second comparison circuit, and a second comparison output corresponding to the detection output ρ of the color difference signal (1)-3') is derived from the second comparison circuit. Ru. This fixed white balance correction circuit (Bl) sets and derives a white balance correction signal such that the one-car comparison output level is 0' when a white subject is imaged or a white lens cap is attached. Therefore, Jl!1.Second latch circuit (161 (171) latches the first and second comparison outputs at the moment when the white balance set operation is completed in the white imaging state. (II, during this white balance set operation period, the box 1.2nd comparison output is directly derived as a fixed white balance correction signal, and during other periods, the 1st and 2nd latch outputs are derived as a white balance correction signal. ing.

Furthermore, the selection circuit (0) of this embodiment includes a first switching circuit that derives a red control output and a second switching circuit that derives a blue control output c! The single switching circuit C22 uses the output of the flip 70 knob 4 as a control input, and outputs the variable white balance correction signal when the flip 70 knob 20 is in the set state, and outputs the variable white balance correction signal when the flip 70 knob 20 is in the reset state. When the fixed white balance correction signal is selected and derived 1
Both color level control circuits (8) (91) perform gain control.The state of this flip-flop □□□ is controlled in conjunction with the operation of the method selection switch (SW). (8W) is the fixed position (
Pl), automatic position (P2), and set position [1, (P5), and the set position (P3) is
During the period when the contact piece at the fixed position (P2) is manually operated against the bias of the spring (during the white balance setting period), only C can be set.1 When manual operation is released, this selection switch (SW) Fixed position (P 2
) l: Forced to return. The flip-flop (to) is preset when the power is turned on, reset by starting the white balance set operation, and set to the automatic position (Pl).
It is set by switching to MU.

Therefore, in this embodiment, the 1 selection switch (S
Automatic tracking white balance correction is performed regardless of whether W) is set to the fixed position (P2) or automatic position (Pl). There is no prohibition of balance correction; after the white balance is set, fixed white balance correction is performed unless the automatic position (Pl) is set.

The latch circuit asas of this embodiment consists of an AD conversion circuit, a memory, a DA conversion circuit, and a latch pulse generation circuit (
21) Latch pulse 1 issued when the white balance set operation is completed: Therefore, the AD conversion data of the comparison output is stored in the memory, and the stored data is read out from now on and DA converted to be derived.

The above-mentioned memory is usually provided with a backup circuit for storing its contents for a certain period of time. Therefore,
It would be convenient to check the memory backup when the power is turned on and allow fixed white balance correction in case the power is temporarily cut off.

Therefore, in the second embodiment shown in FIG. 2, when the 1 selection switch (SW) is set to the fixed position (P2) 1: when the power is turned on, or when it is set to the fixed position (P2) after the power is turned on. , the flip 70 knob is reset if the memory stores the comparison value. In this embodiment, the first . 2nd memory (161)) (1
71)) When the memory contents of 1. Second
By converting to DA conversion, the first. Second switching circuit α
(To) The output of α9 and the reference potential are compared in a backup detection circuit. Therefore, this backup detection circuit 24) deactivates the backup detection output only when both DA (i conversion outputs) are at the reference potential. This reset pulse generation circuit (c) receives the backup detection output and generates a reset pulse when the power is turned on with the selection switch (SW) in IiJ set to the fixed position. The circuit is configured to immediately emit a reset pulse when the selection switch (SW) is set to a fixed position while the backup detection output is being input after the power is turned on.In the end, the reset pulse generation circuit (c) , a reset pulse is derived in synchronization with the rising edge of the AND output of the two operators.

This reset pulse is input to the reset terminal of the flip-flop (1) via the OR circuit (5). Nao 82
The figure shows the main circuit of the second embodiment, and the components not shown are common to the first embodiment.

Further, the reference number 126) is a backup circuit that supplies the tA1 memory (16b) and the second memory (17b) (two backup voltages) for about two hours after the power is turned off.

(G) Effects of the Invention According to the present invention [-], even if the selection switch is set to the fixed position, when the white balance set is not performed, the automatic tracking type white balance correction is performed. , the effect is great.

[Brief explanation of drawings]

FIG. 1 is a circuit block diagram showing a first embodiment of the present invention.
Further, FIG. 2 shows a main circuit block diagram showing the second embodiment. Prisoner... Automatic tracking white balance correction circuit, (BL...
Fixed white balance correction circuit, (O)...selection circuit.

Claims (1)

[Claims] (1) A fixed white balance correction circuit that stores a white balance correction signal when shooting a white subject or when a white lens cap is attached in conjunction with the white balance set operation, and thereafter derives a fixed white balance correction signal based on the memorized output. an automatic tracking white balance correction circuit that detects color temperature using a light receiving element placed toward the subject and derives a variable white balance correction signal, and selects the fixed or variable white balance correction signal in accordance with a selection operation. and a selection circuit that preferentially selects the variable white balance correction signal when the fixed white balance correction circuit is not adjusted, and a color level control circuit that uses the output of the selection circuit as a control input. Unbalanced compensation circuit.