JPH02243065A - Flicker elimination circuit for image pickup device - Google Patents

Abstract

PURPOSE:To eliminate flicker with inexpensive constitution by discriminating whether or not there is any correlation of 6 and 3 field in a time change of an output of an integration device and controlling a gain variable amplifier with any of control voltages depending on the result. CONSTITUTION:A mean value with the size of a field of an input Vi before 1-7 fields with respect to the video signal input Vi is f0, a-e and f1. When a difference between the values f0 and f1 is a smaller than a prescribed value, a 6-field comparator 52 outputs a control signal CP6 to throw a changeover circuit 54 to the upper position in figure. In other case, the circuit 54 outputs a fixed value. The difference between the values f0 and f1 is small only with a change due to the flicker component repeated at a period of 20Hz or 10Hz period among timewise changes superimposed on the input Vi. Thus, in other cases, the circuit 54 makes a control voltage Vc as a fixed value and the gain of the variable gain amplifier 1 is fixed to the unity. Thus, malfunction of gain change due to a signal change is not caused except a signal change of flicker due to discharge light lighting such as a fluorescent light varied with a period of 20Hz or 10Hz.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a flicker removal device used in a video camera. The present invention is effective in obtaining flicker-free and good images in a VC environment illuminated by a discharge lamp such as a fluorescent lamp or a mercury lamp in a video camera.

[Conventional technology]

Fig. 3 is a block diagram showing the operating principle of a well-known 7-removal circuit published, for example, in the August 1980 issue of NHK Technical Report, and in Fig. 1, ... is the input voltage (vl). a variable gain amplifier that changes the gain of the output voltage (vO) according to the level of the control voltage (Vc); an arithmetic circuit that increases the control voltage (VC) that controls the gain of the variable gain amplifier;・31c video signal input (Vi)'il
l field integral integrated over fields M (
Four roads.

(Incorporated)-1 is a delay circuit that delays the output of each of the 31 fields by 1 field time.
This is a correlation detection circuit that controls the operation to stop.

Next, the operation will be explained. It is well known that in the NT80 system television, the video signal is sampled every 1/60th of a second for one screen and converted into a standard signal. Unlike image pickup tubes, solid-state image sensors, which are often used in television cameras these days, generally have a short afterimage time, and have a short field of incidence of 1/60th of a second.
An output voltage proportional to t and t is obtained. Ten thousand.

Discharge lamp lighting such as fluorescent lamps, which are often used in general homes, is emitted at a frequency that is twice the power frequency U, depending on the power supply frequency VC, as shown in Figure 2 (L). It emits light with a large amount of light that changes over time. For example, in our country,
Two types of commercial power sources are used, 50H and CIOAZ, and nine fluorescent lamps are lit at a power frequency of 50H2 and are lit at a frequency of 100H while repeatedly flickering over time. Since the solid-state image sensor Vi of the television accumulates and averages the amount of t that changes over time every 1/60th of a second, the video signal level output from the solid-state image sensor Vi? "It changes synchronously at 120 Hz, causing flicker.

The conventional example shown in FIG. 3 is configured to correct the 20 Hs Africa caused by such a 5 Q Hs light source (lighted order electric light source).The video signal input (Vi) is
Under conditions where the lamp is illuminated with a discharge lamp such as a fluorescent lamp lit at 50 Hz, the output is proportional to 111t, which is the average of temporally varying incident light every second outside of 60 Hz. Figure 2 shows an example of this change over time. In Figure 2, (LIO), CI, 20), (L 3
The area of 0) and - is proportional to the amount of 60 juice incident per second, and the video signal input rv1) is also per field! I
C(LIO), (L'BG), (L30)---
-+7) It varies in proportion to the horizontal VC. In Figure 3, 1
Field horizontal dividing circuit 131#-rl Video signal input for each field (V11 integrated, (1, 10), (1, 20)
, (L 30)...Obtain an output proportional to the area. The delay circuits←utatn@4 each have a one field period (1v
Since the output of the 1-field integral 101 road 31 is delayed by 1 field integral (Akinma), l&l, tbl, 1o:, +(
11, the l field integral [the output of the ol circuit 31,
4*1v, 2v, 3v, 4v period 1'! 1 delay and you get the tiger one. On the other hand, when the gain rjf variable width converter video signal input (vl) is input, the l field integration [circuit 131 obtains the result of the previous integration of one field, and the delay circuits uD, uJ are each variable gain amplifier I
VC holds the integration result of 2 or 8 fields before the video signal input rv1) which has been input to 11.

Furthermore, as shown in the 21st gVC (Lll-LIO), by repeating the same process for every average raVia field of the incident light amount, the output fb+ of the delay circuit (6) is input to the variable gain amplifier il+. It is proportional to the magnitude of the video signal input (rvi) being played.

Here, the video signal input rvi with the flicker averaged is
) can be found as ((a+b+a)/8), so the 7-return power-return (f+fi) of the video signal input r vl input into the variable gain amplifier.

f-b-(a+b+c)/3, and the video signal input r71) is its flicker component? The value is (1+f) times the average value. Therefore, the arithmetic circuit 121 calculates the gain (Ga) for the variable gain amplifier... at the end of this 7-power component +fl'll-. A voltage (vc) of ili'IIm such as 5/(1+f) is outputted.

In the conventional example in Fig. 8, I-i, in this way, for the video signal input (v1) that is just being input, this is corrected at the end of the 7-field power-return tfl' 8 fields before. What is the effect of correcting the 20 Hz African light source by a discharge lamp light source lit by a 50 Hz power supply?
have.

Further, in this conventional example, the correlation detection circuit 51 is configured to prevent malfunctions due to flicker and acid content caused by changes in the scene.

The correlation detection circuit 151 calculates the difference between the output 1iLl of the delay circuit 1iLl and the output 1dl of the delay circuit 1, and if the difference exceeds a certain value of 1L, the correlation detection circuit 151 calculates the gain of the variable gain amplifier 11 (
Ga) is 1 times and corrected? The control at pressure (VC) is fixed to prevent this from happening. If you set the number of grooves like this, it will be 5oHs.
For 20Hz flicker caused by a discharge lamp light source turned on by a power supply, (a = d), the gain (Ga) of the variable gain amplifier is controlled, and the flicker is corrected. Video signal input due to scene changes, etc. (71)
With the change of , (a ≆ d), so that an erroneous correction signal will not be output.

Furthermore, FIG. 4 shows the operating principle of another conventional example shown in Japanese Patent Publication No. 57-99875. It is a block diagram showing
In the figure, (b) is a delay circuit that delays the video signal by one field. In this embodiment, the video signal input (11)
Since the video signal is configured to be delayed by 1 field using the 1 field delay time vt (b),
The magnitude of the input signal to the variable gain amplifier 1 is proportional to the voltage at the output of the 1-field integral lol path 3I without any time difference. Therefore, the l field integral 10
1 path/31 output rVc) Total 11tlla! If the voltage is selected so that the gain (GaJ) of the variable gain amplifier +11 is Ga-1/(Vc), the output voltage (vO) of the variable gain amplifier 11 is kept constant. but.

The configuration shown in Figure 4 has a problem in that a large and detailed memory circuit is actually required to configure the video signal 1-field delay circuit.

[Problem to be solved by the invention]

Since the flicker removal circuit of the conventional imaging device is constructed as described above, 1For example, in the conventional example shown in FIG. There should be. However, in actual photography, when the power supply frequency is 5QHs, a phenomenon is observed in which the brightness changes even with a period of 50 H2 under illumination such as a fluorescent lamp. This flickering of 501(s) may occur due to deterioration of the fluorescent lamp, etc., which causes the cathode and cathodes to lose their efficiency, or the subject being photographed may be exposed to the same amount of light from the cathodes of the fluorescent lamp, etc. Not accepted,
In other words, if one cathode is illuminated non-uniformly (1,i), then the 6 cathodes will be 50 la
This is caused by the fact that x is flickering.

This 50 Hz light M is the field frequency of N day C (60) (z) and a flicker of l Q Hs is generated between this 10 Hz African component and b.
f3t1 Compared to the above-mentioned 20 Hz 7-frequency component, one frequency is lower, so there is a problem that the visibility is high and the quality of one image is significantly deteriorated because it is noticeable.

In addition, in the conventional example shown in Figure 4, 10 Hz Africa is also 2
Exactly the same as US Africa - Although it is effective in terms of Vc correction, it requires a video signal 1 field delay circuit, so in order to obtain sufficient image quality, a large memo + 7 ( , and the equipment is inexpensive V
C It is difficult and rare to configure.

This invention was made to solve the above-mentioned problems, and is a flicker removal circuit for an imaging device that can perform full effective correction and can be constructed at a low cost. The purpose is to obtain.

[Meager means to solve problems]

A flicker removal circuit for an imaging device according to the present invention includes a variable gain amplifier for adjusting the magnitude of a video signal obtained from an imaging device, and a video signal? Integral 4, which is integrated over one field period, and the 7-res force-component before the 6-pull of the output of the integrator of the video signal input? Lessons to correct (fll
[A computing unit that computes the pressure, a computing unit that computes the control a voltage that corrects the 7 liters force-share of the output of the integrator 8 fields before, and either of the correction outputs output by these two computing units. −
1, a switching means for switching to a control output that does not perform correction, a comparison means for determining whether or not there is a correlation between the time changes in the output of the integrator every six fields, and Comparing means and ft are provided for determining whether or not there is a correlation in time changes for each of the eight fields, and the variable gain amplifier is controlled by any one of the control dI voltages depending on the results of these comparing means. It is.

[Effect]

The flicker removal circuit of the imaging device according to the present invention includes 6
When there is a correlation for each field, the gain of the variable gain amplifier is adjusted by the l1al voltage that corrects the output flicker component 6 fields before the integrator of the video signal input,
When there is a correlation for every 3 fields, the gain of the variable gain amplifier is adjusted by the i control voltage that corrects the 7 loss of the output of the integrator 3 fields before the video signal input, and V when the fields are uncorrelated
K acts to control the switching means so that the output is #Ia without i correction.

[Practical example of the invention]

An embodiment of the present invention will be described below with reference to the drawings. In Figure 1, ... is the video signal input rVi) the output voltage rv with respect to VC.
o) Limit the gain! A variable gain amplifier whose gain is varied depending on the voltage (Yc), 13+ is 1'7f-' which is integrated over a field period of the video signal input (Vi) to obtain the average value of the video signal input (VL). Integral circuit, 1
4D w14J HM- is a delay circuit that delays the output (fO) of the 101-way A31 for one field horizontally by one field period, and (fO) is the video signal input (71).
Since there is a delay of one field period for each output +a+ [b+ 1ollcLliel (f
l) respectively for the video signal input ζVi).

2. Delayed by 3, 4, 5, 6.7 field periods. The vibration device is an addition means.121+ viIal l
bl (+22 of the total 3 fields of foI is 1jLI
lbl iot ldl 181 (f O) total 6
Field's sum t-rice. The f3 threshold is a calculation means, and n is the flicker component I (3 fields before the video signal input (vl) from the ratio of bl and the addition means 2+1).
fs ) as in the conventional example shown in FIG.
b+fo)/3, and the emotion is l(&i and Fl
The flicker component 1f6) six fields before the video signal input tVi) is determined from the fflff half-adder rate as f6ae-(a+b+c+a+e+ro)/6. The calculation means '23124 calculates the gain (Ga) of the variable gain amplifier... for each of the variable gain amplifiers m... as Ga=l/(1+fs) or.

A control dll that says Ga-J/(1+fa)? II Ff (”I (!
) ff" output f Ruo nIJ (+3 is a comparison means for detecting the correlation with the output time of the 1-field integral (b) path 13; 1=in is a switching means, and tel is the 3-field integral '2 jM q of the time difference between the
If the difference between lo+ and 1io) is more than a certain level, the switching means 63 switches the signal (Sakura is a two-signal with a time difference of 6 field periods) (fOJ<!: (if the difference from 1 mouth is more than a certain value) Switch the means.

Next, the operation of the dog tilt example according to the present invention will be explained. In FIG. 1, similar to the conventional example in Figure 3, the K1 field integral 1011i41 is reset at the start point of the field period of the television signal, and the video signal input rv1) is 17
°Is integrated over the dark period. The output of the variable gain amplifier III is the delay circuit 5t4a &
Therefore, for each video signal input t vl), the average size of each field of the video signal input (vl) 1.2, 3, 4, 5, 6, 7 fields before is 1i1
1 (f OJlal 11)+ 10+ 1dJ 1
et(fx) Get Jt.

(fO) and (fz) are video signal input rv1)
Since the half-universal signals are delayed by 1 field and 7 fields, there is a time difference of (7-1)/No-1/lOr seconds between these two signals. Also, (fot and 101 are the same.

Since they are delayed by 1 field and 4 fields, there is a time difference between these two signals of (4-1)/60 1/gO.

If the video signal input (vi) has a heavy flicker component that is reflected at a 10Hz cycle, the video signal input (vi)i will have the same magnitude for every 1/10 ["Y]". Therefore, there is no difference between O) and (fl).

Furthermore, if a flicker component that is repeated at 2 o Hz synchronization is superimposed on the video signal input (r vl), the video signal input (r vl) is If it becomes Satoshi, there will be joy even in the darkness of 0) and 101.
, and there is also a difference between (fol and b1).

If the difference between (O) and (fl) is smaller than a certain value, then 6
Field comparison "I'4 is the switching circuit = rn t-
Control signal tQP6 to switch to the upper side of FIG.
), otherwise the switching circuit I outputs a fixed output. VC ( Since the difference between fO) and b1) becomes small, except in this case, switching circuit 1#
The gain (Ga) of the variable gain amplifier +ll is (Ga-1
) Since the VC is fixed, there is no flicker caused by discharge lamp lighting such as fluorescent lamps that changes with 20 Hz or 10 Hz synchronization.
Malfunctions such as gain changes due to changes in other signals do not occur.

If the difference between (fo) and (fl) is smaller than a certain value, and the difference between tfo) and 101 is smaller than a certain value.

3 field comparison (69 is switching time V11r, ■t
-Kind so that it can be cut to the upper side of Figure 1 (f [lfg issue (
OPs)t-output and selects the output of the arithmetic circuit 1 as the control voltage (Vc); otherwise, the switching circuit line selects the output of the arithmetic circuit 24 as the control voltage (Vc). The time change that is applied to the video signal input (Vl) is 20
In the case of only changes due to the flicker fraction that is repeated in the first period of Hs, the output of the arithmetic circuit is selected because the values of (fol and (0)) are small, but the video signal input r
Time-varying component force superimposed on Vi); If included in change 1 due to flicker component repeated with 10 Hz synchronization, the difference between OJ and 1 ojD becomes large, and the output power of calculation-VIt system; The arithmetic circuit port is configured to correct the flicker component three fields before the video signal input (Vl) and increase the gain (Ga) in the variable gain amplifier (tcG&-1/rl+f3)). A flicker component (fa) t is output 6 fields before the video signal input (vl) between the arithmetic circuits.
- Correct the gain (Ga) of variable gain amplifier Ill to (G
a-1/ (1+fa)) at m
Pressure (tic) is output. Therefore, video signal input r71)
has a flicker share, and this flicker share is
When changing in synchronization with 20 Hz, the output of the arithmetic circuit increases the gain by 1. No. 100's flicker share (fs) (gain (Ga) f (G
a14*L, so that a-17(1+fs)), the video signal input (Vi) has a 7-power-component, and this 7-power-component changes in the @ period of 10b. In the case of including a variable gain amplifier 11i, the output of the arithmetic circuit
j) Gain (Ga) t' rGa so that the flicker is corrected based on the flicker component of the video signal 6 fields ago, which is the same size as the video signal input (Vi) that is just being input. -1/(1+ba6)).

As a result, in the flicker removal circuit of the imitation imager in this embodiment, if the video signal input (71) contains flicker with a component that changes with lOHm, the video signal input rv
It detects that there is a correlation for every 6 fields in t) and operates to remove 7 flickers of the same magnitude as the flicker component 6 fields before, and changes the video signal input (vl) with l OHm. Ingredients: 7.20 without Ritzker
In the case where only the 7 retsker of the share that changes with Hs is included, it is detected in 1 that there is a correlation for every 8 fields in the video signal input (41), and the 7 ritzker of the 3 fields before that is the same as the return. Operates to remove 7 ritzker of size,
If the video signal input (71) does not exhibit flicker of a component that changes with time Vc10 Hm or 20 Hz, the video signal input (vl) must have no temporal correlation for each field. This is detected and produced without changing the gain for correction. In this implementation column, the video signal input (V
i) Switching the constraint to the correction voltage 1 when the flicker contained in it includes a 10Ht component, when it is given 20 barks, and when it does not include a synchronous flicker portion. Thus, a system is realized in which both IQHs flicker and 201m flicker are removed in the same way, and the image quality is not adversely affected.

In addition, it is surrounded by the dotted line in the above example ('hanging x diagram). Addition circuit circle, t22. [Arithmetic circuit convex, 14. delay circuit f4υ
, -, Ran, ■, ni), ■, 8 field comparison circuit 60
．． 6 field comparison circuit 63, switching circuit (4, -
can also be realized using an A/D converter, a microcomputer, and software, and by adopting such a configuration, it is possible to construct the apparatus at a lower cost.

〔Effect of the invention〕

As described above, according to the present invention, lQ in the video signal
Hs Africa and 29Hs flickers are removed in the same way, and malfunctions such as video signal disturbances other than the synchronous flicker caused by the discharge lamp light source are also prevented.Furthermore, since no image frame memory is used, m-image It is possible to realize a flicker removal circuit for an fJI image device that does not adversely affect the quality of the image device and can be manufactured at low cost.

[Brief Description of the Drawings] Figure 1 is a block diagram showing a 7-removal circuit for an imaging device according to an embodiment of the present invention, and Figure 2 is a block diagram showing a circuit for removing power from a fluorescent lamp, etc., which is often used in ordinary homes. This is a schematic diagram showing the time change in the amount of light emitted from discharge lamp illumination.The power supply frequency is 5Q.
It shows the relationship between the field synchronization of the imaging device and the light intensity when the light is turned on at Hz. FIG. 3 is a block diagram showing an example of the configuration of a flicker removal circuit of a conventional ant imaging device, and FIG. 4 is a block diagram showing a configuration of a flicker removal circuit of another conventional imaging device. In the figure, ... is a variable gain amplifier and the video signal input (Vi)
Gain (・, Ga') of output voltage (Vo) for interest rate <
[[l! EE rvc>. 31 is a 101-way L field structure, and a video signal input (Vl
) Violet Integrate over one field period. (Uri. ・The comparison circuit that compares the magnitude of the video signal with a time difference of 3 or 6 fields, (I541) determines the control voltage (Vc) depending on the result of the comparison circuit. The switching circuit that switches In addition, in the figures, the same reference numerals indicate 4- or corresponding parts.

Claims (1)

[Claims] A variable gain amplifier into which a video signal obtained from the image sensor is input, an integrator that integrates the video signal obtained from the image sensor, and this value is determined in advance by calculating the autocorrelation of the output value of the integrator with respect to clock changes. What is claimed is: 1. A flicker removal circuit for an image pickup apparatus, characterized in that a comparing means is provided for comparing with a constant value, and a method for controlling the gain of the variable gain amplifier is switched depending on the amount of autocorrelation.