JPS6033029B2 - Electronic video image synthesis device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to foreground and background composition for film or television use, and more particularly to so-called "sound screens" or special background color screen devices.

This patent application is a joint patent application that was filed on November 8, 1977, and has already been approved.

This is a continuation-in-part of U.S. Patent Application No. 73,874. Of course, it has been proposed for some time to synthesize foreground and background using electronic techniques. Regarding this, 19
My previous "Electronic Composite Photography method" patented on July 27, 1971.
U.S. Patent No. 3,595,987 titled
No. 616,685, filed September 25, 1979, and also my co-filed application,
"Electronic CompoS Ship Ph
ography With Color Control
)", US Pat. No. 4,007,487. The principle of foreground and background compositing, which has been used in all previous devices, consists in using a so-called "blue screen" or other monochromatic background.

A blue screen is used as a foreground gundrop, and its color is very close to pure blue.

Other objects having the same color may also be included in the device. Electronic circuitry is used to detect the pure tone signal and to block or turn off the background video signal when the blue screen is obscured by the foreground. vice versa,
If the foreground signal comes from a blue screen or other objects painted the same color, block the blue foreground color from the screen or other pure blue objects and boost the background video signal to full strength. Must-have. My U.S. Patent No. 3595
No. 987 addresses two problems that arise with devices of the type outlined above. To be more specific, the objects in the foreground are
For example, like blue eyes, although it is close to the blue of the background screen,
If blue containing more green is included, equipment must be used to properly reproduce the blue eye.
It has been found that for normal foregrounds it is sufficient to limit the blue value to the green level present in the detected signal. To recreate the pale blue color of blue eyes, blue jeans, or similar, use my U.S. Patent No. 359,598
No. 7 discloses that by amplifying the green signal to be compared and limiting the blue to the amplified "KG", the green level present in the foreground signal can be For example, blue can be increased to 1.3 tones. U.S. Pat. No. 3,595,987 also discloses an apparatus for reproducing transparent foreground objects, such as smoke, glass, or objects that appear blurred and translucent, such as a foreground rapidly moving hand or arm. . Reproduction of this transparency was handled by controlling the level of the background video signal depending on the magnitude of the difference between the blue and green (or amplified blue signals) present in the foreground signal. In the case of a pure tone signal representing a background screen, of course all background video signals are forced through the gate. However, as the green content increases, the level of the background video signal is reduced.
My U.S. Patent No. 616,685, or U.S. Pat.
No. 007487 discloses certain improvements to this type of electronic color device.

In particular, it discloses a special circuit for removing red and green impure colors from a background screen that should be pure blue. To do this, we use circuitry that is sensitive to the transparency of foreground objects, applies corrections proportional to this transparency to the foreground red and green signals, and based on which we extract the pure spine from the background video signal. The red and green impure colors resulting from the blue screen are removed by subtracting the red and green signals in proportion to the amount of signal obtained from the intended background screen. My U.S. Patent No. 4,007,487 mentioned above
In other circuits disclosed in the above issue, the blue limit is subject to two conditions. These two conditions allow for proper reproduction of foreground pale blue colors and also allow for suppression of "blue flare" or addition of blue color to whites or skin tones due to blue light from the blue screen. The first condition limits blue to green or an amplified green signal, denoted "KG" as described above. At the same time, blue is limited so that the excess of the green signal over the green signal is only the difference between the green and red signals. These two criteria are: for blue eyes or blue jeans, blue, lines,
and red are substantially linear functions in degree, and the amount by which blue exceeds green is substantially equal to the amount by which green exceeds red. Thus, faithful reproduction of foreground light blue signals, such as denim or blue eyes, is achieved by increasing the amount by which blue exceeds the green level only to the signal difference between green and red. On the other hand, the blue flare from a blue screen for white or skin tones does not include the excess of green over red, and the restriction of blue to the green level or KG is warranted, so The blue flare problem will disappear. Although the device described above is suitable for many purposes, it still has some drawbacks. For example, with the device described above, it is practically possible to handle pale blue objects and violet or magenta together in a single scene. That is, it would be impractical to include a blue-eyed queen dressed in purple in the cast. Still, in the devices described above, control of the background video signal is unnecessarily limited. Details are limited. In particular, the above-mentioned devices are unable to provide varying degrees of impressive shading effects as desired by producers and directors, and the background video signal is not sufficiently adaptable to the foreground. Cannot be correlated with green light control. The primary objective of the present invention is to overcome these shortcomings of slave devices and provide a more comprehensive and flexible device for controlling both the foreground green signal and background video signal levels.

It is also an object of the present invention to provide an electronic video image compositing device that includes an anti-veiling device for eliminating discoloration in the composite image caused by screen color components. Another object of the invention is to increase the flexibility of switching in the handling of foreground and background signals of the ``blue screen'' type.

A general feature of the invention is a blue screen (or other monochromatic screen) type electronic device for combining both foreground and background video signals, the foreground blue video signal comprising:
The background video signal as a whole is controlled to be no greater than the foreground green video signal increased by a function of the difference between the foreground red and green video signals. the foreground blue video signal having an intensity level approximately proportional to the foreground blue video signal that is a function of both video signals and which may be varied to provide optimal operation; That is, it is made to vary by electronic circuitry that introduces multiplicative constants and/or additive or offset constants. The electronic device is being used. Other features of the invention change the weight of selected factors or eliminate them if the foreground does not contain violet or magenta, or if the foreground does not contain pale blue or cyan. An electronic regulating circuit or an electronic switching circuit that can be used is used.

A sub-feature of the invention is that special shading operations to create special or impressive effects may be performed by electronic circuitry generating background video control signals. This circuit is also varied by appropriate proportionality constants to adjust for the brightness variations of the "blue screen" background. Using this circuit, the shading can be intensified or completely eliminated, depending on the effect to be achieved. Another sub-feature of the invention is that the two variable electronic controllers for varying the shading control constants are coupled or coupled to the same control knob, so that separate adjustments are unnecessary. . Other similar features of the invention include:
The foreground blue video signal selection switch is coupled or mechanically coupled to the background video signal control switch so that these switches are operated in unison.

To summarize the results achieved regarding the control of the foreground blue video signal and the background video signal, the device is
Let us consider Example A, which switches between three modes, and Example B, which adjusts a variable partial pressure meter to accommodate different foreground color combinations.

The circuit of Example A can switch between modality 1, modality 0, and modality m, where modality 1 is applied to a scene without light blue and violet in the foreground colors, and modality m is applied to a scene in which the foreground color contains pale blue. , and is applied to scenes where the foreground contains both pale and purple colors. Example A--Form 1: No pale blue or purple in the foreground.

The switch is in the 1st position BC≦KG
'11 where Bc represents the clamping of the foreground blue video signal, G represents the foreground line video signal, and K represents a constant that can vary from approximately 0.5 to 1.5.

Ec=K, (B-G)-K2 ■Here,
Ec is the control signal for the background video, Ec=1
When Ec=0, the maximum background video is given, and when Ec=0, no video is given at all. Furthermore, K and K2 are a proportionality constant and a biased constant, respectively. Style 1 is the simplest and most reliable style, adapts well to changes in transparency and has other advantages as well.

Example A--Form B: The foreground has a light blue color but no purple or magenta.

Switch is the second best way B.

≦G+(G-R)+'3}, where R represents the instantaneous value of the foreground red video signal.

A ten sign after the parentheses indicates that only positive values are valid. Ec=K, [(B-G)+-(G-R)+]-K2
(
The control of the foreground blue video signal when the 4-switch is in the second position is as described in my co-pending application referenced above, with the foreground blue video signal being lower than the foreground green video signal.
The difference between the foreground green and red video signals can be large. Since blue, green, and red usually have a linear relationship in light blue, this modification renders light blue foreground objects realistically. The additional term in the control equation {4) for the background video signal is still (G-R), which causes the entire function in parentheses to be zero for pale blue objects, but in that case ( If it is only the term B-G), it should have a finite value as in Format 1.

Example A--Form m: When the foreground includes pale blue and purple or magenta.

BCmiG+(G-R)10(R-G)+ ■EC=K.
[(B-G) Eleven (G-R) Eleven (R-G) +] -K2
[6] In both equations {5} and (2) above, the new term (R-G) modifies the basic equation so that it can be applied to purple or magenta.

In violet or magenta, blue is stronger than green, and
The red in the foreground is still substantially stronger than the green. In the equation-side case, the new term (R-G)+ allows the foreground blue video signal to be larger than the green by this difference, and in the equation-side case, it brings the control voltage Ec to zero. It will be lowered to. Example B As mentioned above, in the circuit of Example B, adaptation to different foreground color combinations is accomplished by varying the selected partial pressure gauges.

The change causes m in the foreground blue limit function, and'
2' Key constants in the background video control signal are controlled. The restriction function for foreground blue is expressed as: BcSG+KB(G-R)10KM(R-G)11
[7] Also, the background video control function is expressed as: Ec=K,
{B'-C[K2 (KRORKGG) ten (1-K2) (
KRRANDKGG)〕}'8
1 where B' represents the filtered foreground blue video signal and K2 is a voltage divider for selectively summing the two terms containing R and G representing the foreground red and green video signals. It is a constant.

The symbol "OR" in the function ■ indicates that the larger of KRR and KGG should be selected, and the symbol "AN" in the function [8}
"D" indicates that the bell will pass through the gate only when both KGG and KRR reach a certain level; therefore, the one between KGG and KRR, i.e. the lower level, should be selected. shows. Function [7l and {8
), we will first consider the meaning of function [71].

K8 and KM represent the action of the partial pressure meter and their values can vary down to zero. When both KB and KM become 0, the function becomes equivalent to the function {7 female equation [1-], and when the magenta control KM becomes zero, the function becomes the same as the equation '3}. When both cyan and magenta are included, function {7) is of course equivalent to equation {5}. Next, considering the background control voltage Ec given by the equation
Controls the dominance of the "R" term or the "rAND" term. Normally, the ``AND'' term is allowed to predominate, because if no foreground cyan or magenta is present, the ``AND'' term is allowed to predominate.
D'' term provides a good transparency range, and under such conditions the partial pressure meter constant K2 is made to be zero or close to zero. However, if magenta or cyan is present, the value of K2 must be increased to near 1 to prevent the background from showing through. Also, some mixing of the two terms can help compensate for any misalignment that may occur in the image camera. As for other features of the invention, the final background video control function will be an advantageous modification of the "original" background video signal given by the above equations, as discussed below. More specifically, it is '1) a nostalgic function to give, for example, an appropriate shading level, '21 a step-like function that can adapt to the changing brightness of a "blue screen", and '3' last. Preferably, it is of the form of a horizontal function that provides a constant background signal regardless of changes in the brightness level of the "blue screen." Other additional features of the invention include the provision of special controls to facilitate the implementation of special effects.

These control devices are: [1] blue screen and foreground;
Contains switches that allow you to provide {2} foreground only without a blue screen, {3: background only spanning the entire screen, and background with '41 foreground erased and an erase hole created in the background. . By "key-in" using a suitable window generation circuit, a window can be generated in the background, thereby allowing the use of a small blue screen on a large stage. On the other hand, a "Key-out" signal derived from the background video control signal is used for certain special effects. If a monochromatic screen other than blue, such as a green screen, is used as a background screen for foreground video, the same principles outlined above generally apply, but the video inputs must be swapped accordingly. No.

The above summary provides a brief description of the circuit.

Other objects, features, and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings. In the drawings, FIG. 1 shows a foreground video signal source 12, a background video signal source 14, and a monitor television device 16 for displaying the composite video output.

A compendium of this entire device is my U.S. Patent No. 35959 mentioned above.
No. 87, it is explained by way of example.

The invention disclosed herein relates to video control circuitry, illustrated by block 18 in FIG. 1 and shown in further detail in FIGS. 2 and 3. For the sake of completeness, a brief description of the major circuit elements shown in FIG. 1 will be provided.

With respect to the foreground video signal source 12, a key element of the device is a monochromatic screen 20, preferably of a color very close to pure blue, now referred to as a cobalt blue screen. This may be any other solid color such as green, but blue is preferred and widely used. This screen is illuminated by lamps 24 and 24, with lamp 26 illuminating a foreground object 28. TV
The camera 30 detects a foreground object 2 with a blue screen 20 as a background.
Scan 8. By the techniques described in some detail below,
A background video signal generated by circuit 14 and contained on film 32 replaces the blue screen during image composition, so that what appears in the video output are foreground objects 28 and background from film 32. The resulting scene is a composite scene, and the composite video is displayed on the monitor 6. Other circuits and elements shown in FIG. 1 include a scan and frame control circuit 34 and a mixer circuit 36 for combining both foreground and background video signals.
and signal E from circuit 18. three gate amplifiers 38 which are controlled by a gate amplifier 38 to pass or block the background video signal from the circuit 14 to any desired degree;
is included. Background video signal source 14 includes a flying spot scanning device 40 and a lens 42 for focusing the light spots on tube 40 onto film 32.

Dichroic mirror 44 separates the light beam into its original, green, and red components, which are converted by photocells into electrical signals and sent to corresponding amplifiers 38 . TV camera 30 forming part of foreground video signal source 12
In addition, there is a partially silvered mirror 48 to reflect some of the image light coming from the foreground toward the motion picture camera 50.

In the foregoing description of FIG. 1, an apparatus in which all elements are well known has been described.

Next, let us examine the logic circuit diagram of FIG. 2 in detail. The new features of the invention are realized by this circuit, and the implementation of equations '1} to 6} above is carried out by this circuit. In FIG. 2, red, green, and blue foreground video signals appear at terminals 52, 54, and 56, respectively.

Similarly, red, green, and blue background video signals are provided to input terminals 58, 60, and 62, respectively. After input amplification by amplifier 64 and, if necessary, DC regeneration by circuit 66, these video signals are passed to voltage follower 6.
8. Since the background video signal is easier to track than the foreground video signal, the circuitry for the background video signal will be described more briefly.

The red, green, and blue background video signals are connected to lines 71 and 7, respectively.
The signal is supplied to multipliers 74, 76, and 78 via 2 and 73.
In these multipliers, the background video signal is made to vary linearly from a maximum level to zero in response to an input signal Bc supplied from a common control lead 80. multiplier 74,
The output background video signals from 76, 78 are then amplified by operational amplifiers 82, 84, 86 whose outputs are reversed. These outputs are then provided to the negative input terminals of output synthesis operational amplifiers 88, 90, and 92, respectively, by which they are combined with the foreground video signal into a composite video output and a composite red, green, and blue signal. teeth,
They appear at terminals 94, 96, and 98, respectively. In the equipment that makes up the components of the circuit shown in Figure 2, all components indicated by the triangular amplifier symbol are part number LHO032 (Na
tio cape I Semicon-duc to r-PartN
o. LHO032).

Of course, under different circumstances, the operational amplifier may be used as a differential amplifier, an inverting amplifier, a voltage follower, or other functional device. Multipliers 74, 76, 7
8 is Motorola part number MC
I595 also allows circuit 66 to perform signatures (
Constructed by Si Liuetics part number DG-190. Now, equation {1
Here, several different terms are used to generate the control signals, the first control signal controls the foreground video signal, and the second control signal controls the background video by Ec. Control. In this regard, switches SI and S
Pay close attention to 2. As indicated in the drawing legend,
The switch SI is shown by the equations '11,'3}' and 'different' according to the switch positions 1, 2, and 3, respectively.
One of three clamp control voltages can be selected. On the same machine, switch S2 is on terminals 1, 2, and 3.
Equations ■, [4}, corresponding to formats 1, 0, and m, respectively
[Provide functions defined by the skin. Note that in equation m, the foreground blue video cannot be larger than the foreground line video modified by the constant K.

In the circuit diagram, conductor 102 supplies foreground blue video to clamp 104. Switch SI provides the clamp voltage on conductor 106 to clamp circuit 104 . When the switch is in position 1, the foreground line video from conductor 108 is fed to operational amplifier 1 10 and the output of amplifier 110 is
The signal is supplied to the first terminal of the switch SI through a resistance circuit including a fixed resistor 112 and a variable resistor 114. If amplifier 110 has a maximum gain of 1.5 and variable resistor 114 has a total resistance value twice that of fixed resistor 112, then if the instantaneous value of the foreground green video is denoted by "G", the voltage divider 114 will be 0. ．．
50 to 1. It can give a range of up to 10 steps. Switch position 2 of switch SI has a clamp limit voltage of G+ (G-R).
Realize the equation (3} that requires that “G
” section connects the green video from conductor 108 to operational amplifier 116.
is obtained by applying it to the negative input terminal of . The resulting -G signal is applied to the negative input terminal of operational amplifier 118 and combined with the (G-R)+ signal from amplifier 120. Note that the inputs to amplifier 120 in this case include the foreground red video signal being provided from the negative input lead 122 and the foreground green video signal being provided from the positive input lead. Block 12 marked "z.c."
6 has a zero clip function that prevents the signal from going negative. The "z.C." flock is in each case
It performs the above function by combining with the operational amplifier in front of it.
A conductor 128 provides the output of zero clip block 126 to the positive input of operational amplifier 118. Thereby,
The output of amplifier 118 will represent the function G+(G-R), which is of course the function given by the equation {3}. This output, after passing through zero clip, block 130, is output to switch terminal 2 of switch SI.
is supplied to The control of the mode m of the foreground blue video is effected by the input to the support point 3 of the switch SI. Comparing equation (5' with equation {31) shows that only one additional term (RG)+ is required. A red video is applied to the input, and a green video is applied to the negative input.As mentioned above, (R-G)
The tens sign after the ten term means that only positive values are used. Zero clip block 136 has this functionality. The polarity of the (RG) tenth term is reversed twice when combined with the other two terms G+(G-R)+ of equation t5}. This inversion occurs within the circuit of FIG.
and 14 rivers, and at that time, zero clip. The output of block 136 is applied to the negative input terminal of amplifier 138, and the output of amplifier 138 is applied to the negative input terminal of amplifier 140. In this way, amplifier 14
The output of 0 will be the desired term given in equation (2). Of course, when set to switch position 3, the blue video is clamped to the level indicated by Equation 3, thereby allowing both pale blue and violet or magenta to be handled together. Now considering switch S2, its function is to control the background video by means of a control signal represented by Ec.

As previously mentioned, this control signal is passed through line 80 to multiplier 7.
4, 76, and 78. As in the case of the switch SI, the switch S2 also has the format 1, 0, m, and the above equations ■, [41, '61' corresponding to the first, second,
The third has three positions. In considering the realization of Equations (2), '41, and [61], we first focus on the foreground video term, and the constants K and K2 will be discussed later.

First, in Equation '21, the foreground video signal is B-
It comes in the form of G.

At this time, green video is applied to the negative input and green video is applied to the positive input. generated by differential amplifier 142. The B-G term resulting from the output of amplifier 142 passes through zero clip block 144 to switch S.
2 is supplied to switch terminal 1 of 2. the second of switch S2
The switch position implements equation [41]. Equation ■ includes the (B-G)+ term, and from around this time it has a positive value (G
-R)+ is subtracted. Of course, it is possible to obtain both of these terms, with the (B-G) ten term appearing at the output of the zero clip, block 144, and the (G-R) ten term appearing at the output of the zero clip, block 126. These two
The terms are combined by an amplifier 146 and the resulting term is applied via a zero clip, block 148, to the second switch position of switch S2. switch S
The third terminal of 2 is used to realize equation '6}.

In this equation, in addition to each term of equation '4} that appears in the second switch position of switch S2, an additional (R
-G) + term is required. The (R-G) tenth term is obtained at the output of zero clip circuit 136 as described above, and is applied to the negative input of differential amplifier 152 via conductor 150.
On the other hand, the other term in equation (2) appears at the output of zero clip circuit 148 and is coupled to the positive input of differential amplifier 152. The output signal of amplifier 152 is applied to terminal 3 of switch S2 via zero clip block 154. In the above description, switches SI and S2 have been explained moment by moment.

However, in both switches SI and S2, contact position 1 is both associated with style 1 and contact positions 2 and 3 are associated with style 0.
and m. Therefore, the mechanical coupling device 18
2 is provided for interlocking switches SI and S2, thereby eliminating the need to turn the two switches to separate positions. By rotating them simultaneously, it is possible to realize three styles: style 1, style b, and style m. However, to increase adaptability,
If fine adjustment of all parameters is desired, switches SI and S2 can be operated separately. Next, the equation that gives the background video control signal Ec is [
Consider the constants K and K2 that appear in each of 21, [4), and '61.

The multiplier factor, constant K, is simply realized by a partial pressure meter, shown as K, in the figure. The wiper arm 156 of the voltage divider K, picks up between the wiper arm of the switch S2 and ground any desired level or any desired proportional amount of the signal appearing at the switch S2. The subtractive or biased term K2 is formed by the voltage divider K2 connected to the negative input of the differential amplifier i58.Of course, the positive input of the amplifier 158 is connected to the wiper arm 156 of the voltage divider K. The output signal of the differential amplifier 158 is transmitted through a zero clip circuit 160 and then through a 1 volt limiter circuit element 162 to a conductor 801, which transmits the control signal to three multipliers 74, 76,
78 to control the background video.

Regarding the shadow control partial pressure gauges K and K2, it was mentioned earlier that by varying them, it is possible to provide very dark and strong shadows, or to eliminate shadows altogether. Differential amplifier 158 and 1 volt
The effect of the variously set pressure dividers K and K2, as well as the function of the limiter circuit 162, will now be considered in relation to these various desired shading conditions. First, it should be noted that equation t6} must give maximum output when the video signal originates from a blue screen.

For convenience, equation {6' is reproduced here. EC
=K, [(B-G) eleven (G-R)+-(R-G)+]
-K2 {61 In the blue screen area, blue has a level of about 0.80 to 0.90, green has a level of about 0.15 to 0.20, and red has a level of about 0.05 to 0. It has a level of .10.

Using these larger values for each color in equation (6) above, we get the following equation (9}, side, (11)
The results shown are obtained. EC: (0.9-0.2)
-(0.2-0.1)-(0.1-0.2)
(9}: (0.7) Iku○・1) One (0) ■=(0.6)
(11) Since the multipliers 74, 76, and 78 require a level of 1.0 volt to turn on to the maximum, and a level of ``ro'' to turn completely off, the constant K, and K2 must be set appropriately to achieve these values under desired conditions.
Incidentally, the following equation is the equation ■, ■, ■
It is useful to realize the shading control function contained in each of the .

Ec=K,(Es)-K2 (12) where Es is the standard background video control signal applied to any one of the three positions of switch S2.

Table 1 Shading control: Set values of partial pressure gauges K and K2 to achieve special shading effects Reference is now made to Table 1.

The first two rows of this table are for standard conditions.
Under these conditions, the voltage E from the wiper of switch S2 has a level of 0.6 for the blue screen. Setting resistor K, such that the multiplier factor is 1.67, and setting K2 to substantially zero, the output of voltage divider K, (amplified by amplifier 158)
becomes 1.0, and the control voltage Ec on control conductor 80 also becomes the desired 1.0. Also, as can be seen from the second horizontal row in Table 1, the set positions of the two partial pressure gauges are the same as before, and the foreground objects are being scanned, so that the voltage E from switch S2 becomes 0. If so, the control voltage Ec on conductor 80 will still be zero and the background video will be completely cut off. To highly enhance the shading, set the partial pressure meter K2 to a fairly large value, for example 2 volts. In that case, the partial pressure meter K, is set to achieve a voltage Ec of 1 volt on the conductor 80 in the "blue screen" area outside the shaded area. As shown in the first row of the ``Shadow Enhancement'' column of Table 1, this can be achieved by setting the partial pressure meter K, to a multiplier factor of 5 and By generating a voltage of 3.0 and biasing this voltage by -2 volts from voltage divider K2, an output of 11 volts is generated from the differential amplifier. amplifier 158
amplifies the signal from the voltage divider K by 10 times, but in the above explanation, it is assumed that this amplification factor is included in the voltage from the voltage divider K, so the voltage is amplified by the voltage from the voltage divider K,
It can be directly compared with the voltage from 2. Of course, you need to be careful about this. The full range of the output voltage of the differential amplifier 158 is, of course, no longer from 1.0 to 0, but from 1.0 to -2, with 0 being only 1/3 of the way to -2. Become. Therefore, a shadow that reduces the blue screen intensity to 70% of the standard intensity will be complete darkness. The above analysis shows that the first
These are sequentially shown in the second and third rows of the "Shadow Enhancement" column of the table. The last column of Table 1 is labeled "No shading".

In the shaded area, equation (2) can only provide a voltage E of 0.1 to switch S2. This number is
It appears in the second row from the bottom of Table 1, in the row labeled "Standard Shading," in the third column labeled Bs2. In order to raise the control voltage Ec on line 80 to a level of 1.0 volts, K, must have the value 10. Under these conditions, the unshaded blue screen produces an output voltage of 6.0, which is of course clipped by circuit 162 to 1.0 volts. Therefore, the implementation of the no-shading effect results in a Liuji effect in which the range of transparency is compressed. Broken line 170 between partial pressure gauge K and K2
} The mechanical connection designation indicates that these partial pressure gauges may be connected by mechanical links, if desired.

However, it is now desirable to operate these partial pressure gauges separately in order to achieve the desired effect. Furthermore, if the two partial pressure gauges were to be interconnected, a pneumatic linkage could be included so that for a substantial adjustment range of partial pressure gauge K, partial pressure gauge K2 could be held at or near the zero level. It is necessary to The two partial pressure gauges can then be rotated together at the appropriate rate. Next, consider another feature of the circuit of the invention.

When a blue screen is being scanned, it is desirable to bring the foreground video all the way down. However, the blue screens used in movies and television are not completely blue. A transparent blue screen will leak some red and green, while a reflective one will reflect some red and green. If the blue value is 100%,
Typical values for green and red are 20% and 10% respectively
It is. If not suppressed, this level of red and green from the foreground will create a veil of gray in the background 8-tone area. Amplifiers 164, 166, 168 are anti-bale amplifiers, and partial pressure meters 170, 172, 174
Has the ability to subtract a manually adjusted voltage to the foreground video color leakage value through the use of . Blue veil prevention control device 1
74 is set in a similar manner to the red and green controls and serves similar anti-veil purposes. However, blue veil does not result from screen leakage, but rather from the way the foreground blue video is controlled and formed. The anti-veil bias is only used when the blue screen in the foreground area is being scanned.

It is turned off when solid foreground objects are being scanned, and reduced in intensity when translucent foreground objects such as smoke, glass, etc. are being scanned. This variation in Beer bias is caused by partial pressure gauges 170, 172, 1
The conductor 8 is applied as a control voltage to the high point of 74.
This is realized using an Ec signal above 0. Of course, it is undesirable for the foreground video to drop below zero, and the zero clip blocks 176, 178, 180 are intended to ensure that this does not occur. If the functionality of these zero clip blocks 176, 178, and 80 were not included, the foreground video anti-veil voltage would be subtracted from the foreground video, resulting in distortions in the colors appearing in the composite image. The circuit of FIGS. 3A and 3B is similar in many respects to the circuit of FIGS. 2A and 2B.

Specifically, an input foreground video signal is provided to terminals 201-204 at the top left side of FIG. 3A, and a foreground video input is provided to terminals 205-208 at the bottom left side of FIG. 3A. Then, both the foreground and background video inputs
Note that there are four input leads. These inputs can include brightness or contour inputs in addition to red, green, and blue. Output terminals 209 and 212 at the far right of FIG. 3B are provided with composite video output signals. Incidentally, as explained below, a switching device can be used to create only the background video, only the foreground video supplemented by a blue screen, only the foreground with the background removed, and only the background with the foreground removed. is transmitted to the output terminal 212 without the output terminal 209. A suitable input synchronization circuit for both the foreground and background video signals is provided by circuit 214. next,
The remainder of Figures 3A and 3B will be discussed, primarily in Figures 2A and 2B.
We will focus on circuits that are significantly different from those shown, and will not consider each individual signal formation in turn.

It should be noted that in this case too, the two main control signals are formed in a conventional manner. One of these control signals is the control voltage Ec, which is EB. EBo defines the strength of all four background signals. The background video signal applied to input terminals 205-208 appears on conductors 215-218 after being amplified. Background control voltage E. G is conductor 22
0 and no individual multiplier circuits 221 and 22
4 to achieve the proper value of the background signal, thereby filling in the periphery of the foreground image provided to input terminals 201-204. One improvement to the circuit of FIG. 3 is the use of tapped delay line 226 to provide signal EBG from line 228 to control line 220 which directly controls multiplier 221 and 224. be.

The delayed delay line allows the timing of the background signal EBG formed from the foreground video signal to be slightly shifted, so that the foreground video signal is accurately synchronized with the background video signal being controlled. Regarding the value of EBG and its effect on the background video signal, when EBG has a value of 1.0, the background video is
No 21, then 224 is passed at full strength.

However, E.B. When becomes 0, the background video is transferred to the multiplier 22
It stops passing through 1 to 224 at all, and EBG is 0 and 1.
If the background video is at an intermediate level between , the background video is passed through by a proportionate amount to give the full range of transparency needed to accurately depict glassware, smoke, or moving objects, for example. Regarding the formation of the modified background video control signal EBc, some of the factors considered in the circuit changes made in FIGS. 3A and 3B are as follows.

m At any one time, we want to reduce noise by making the signal a function of only two input signals, {2
}Providing a more complete range of transparency in the absence of pale blue, cyan, or magenta colors, {3
l Ability to adjust for minor misorientations of the color camera that give undesirable visual effects during the compositing process when special foreground-background situations exist. The new EBc formation circuit is
In addition to the two input voltage dividers KR and KG and the output voltage divider K2, it includes an AND circuit 230 and an OR circuit 232 as important elements.

Partial pressure meter K2 is also used in connection with the quantities appearing in the equations described below. If there is no light blue, cyan or magenta in the foreground, the partial pressure meter K2 will be at the lowest point 23
4 and receives a signal directly from the AND gate 230.

The output of the AND gate 230 is a selection of the lower level of the output signals from the voltage dividers KG and KR. Therefore, circuit 230 is not an "and" gate in the usual digital sense, i.e., an AND gate that is fully on or fully off depending on the level of the digital input signal; This is a circuit that sends out an output signal at the lower level of two input signals. It will now be recalled that one similar slave circuit previously proposed made the background control signal a function only of the background blue video minus the foreground green video or a function of the green video. Unfortunately, it would treat red and green objects differently and could not provide full range transparency for both types of objects. Therefore, if E8G (background control voltage) is a function of B-G, the transparency of the green object will be 5.
For a green object in a situation where 0% is appropriate, the background will still be completely erased, but on the other hand,
In the case of a red object, in the situation of 50% transparency, B-
G has the correct 50% blue content (from the screen), so 50% of the background will be passed through. The function obtained in this case at the output point 234 of the ungate 230 is: Ec, = (1-K2) (K
(RRANDKGG) (13) The output of the OR circuit 232 is the higher level of the two input signals KGG and KRR.

This allows for adaptation to situations where blue is equal to or greater than either red or green, for example in the case of cyan or magenta costumes. Under these circumstances, the voltage divider K2 is above its resistance,
That is, it is moved toward the OR circuit 232 and outputs the signal from the terminal 236. The resulting function is as follows. : E.

2:K2(KRRORKGG (1 illusion) This function (14) has the property of reducing the range of transparency for bright green or bright red.

For certain scenarios, it may be desirable to use a combination of the outputs of both OR circuit 232 and AND circuit 230, in which case voltage divider K2 is set at the midpoint. The resulting function makes it possible to compensate for the misalignment of the guns of a color camera when a white foreground object appears against a white background. Without this compensation, the misalignment can cause dark lines to appear at the foreground-background boundary. The modified foreground blue B′ is the operational amplifier 237
is subtractively combined with the output from the partial pressure meter K2, and the uncorrected Ec appears in the output of the partial pressure meter K.

The resulting function is expressed as: Ec
=K, {B-C[K2 (KRRORKGG) ten (1-K
2) (KRRANDKcG)]} When considering the above equation leg, the control signal E at any one time.

Note that is a function of only two foreground video signals: blue and either red or green. Therefore, compared to the functions formed by the circuits of FIGS. 2A and 28, the noise caused by the combination of several noisy signals is substantially reduced.
It has also been found that the foreground blue video input contains particularly high noise.

Delay circuits 238 and 240 and AND circuit 242
Special noise reduction circuits, including , are used to cancel some of the high frequency noise. This noise cancellation is accomplished by using a delay circuit as circuit 238 with a delay of about 30 nanoseconds and a delay circuit as circuit 240 with a delay of about 60 nanoseconds. This is exactly equal to 1800 for the 17 MHZ, mother MH2 and 0.8 MHZ signals, thus noise around these frequencies will be cancelled. If this specialized foreground blue video noise reduction circuit is used in combination with the last three equations above configured as shown in Figure 3, the noise will have a noticeable negative effect on the resulting composite video output signal. The noise level can be reduced to the point where it no longer contributes. The shading level control device in the circuits of FIGS. 3A and 3B primarily consists of operational amplifier 24.
6 (which acts as a switch) and a voltage divider K.6 (which acts as a switch) and associated with multiplier 248. and Ks.

Conductor 250 provides a control level (typically 1 volt) for the switching of amplifier 246. Specifically, if the input Ec from the voltage divider K, is greater than 1 volt provided on conductor 250, the operational amplifier 246 is disabled and the shadow control voltage divider Ks is ineffective. However, if the voltage Ec from the voltage divider K, drops below 1 volt, the amplifier 246 switches and creates a short circuit between its output and the wiper arm of the voltage divider Ks, so that the multiplier 248 , as explained below, the partial pressure meter Ks
will respond to the set value of . Reference is now made to FIG.

FIG. 4 shows blue brightness levels at various locations within a typical scene that has been tinted blue to provide a "blue screen" effect. Of course, when it comes to blue screen photography, it is impractical or impossible to use an actual blue screen that is uniformly illuminated at all times. Alternatively, a set containing walls, floors, and stairs would typically be included in a "blue screen" set. To improve the uniformity of illumination, arcuate fold-up recesses are used to connect the wall forming the rear of the set with the floor. Of course, the stairs used in the set,
Since the walls, floors, recesses and all the furniture are colored the same pure blue color, the improved device of the present invention allows them to be illuminated to form a background. become. In Figure 4, the relative blue brightness at different points within the set is plotted. The top of the wall has 100% blue brightness, as do the bottom of the wall, the floor, and the surfaces of the stair treads. However, as seen at point 252, the relative brightness at the center of the depression between the wall and floor is only 50% of the relative brightness in the plane of the wall and floor.
decreases to Region 254 is also noteworthy. This region shows the shadow of a pseudomorph on the wall, and its relative blue luminance is about 40
%It has become. It is desirable that the background signal be fully transmitted even in poorly illuminated areas of the "blue screen" background.

If no special circuitry is present, the background control signal is
Assuming it is set to 1 for 00% blue luminance, the background signal is reduced to 50% in the recessed area between the wall and floor, indicated by point 252 in FIG. More generally, non-uniformities in the illumination of the entire scene will be directly reflected in variations in the intensity of the transmitted background. Of course, such a result is undesirable and makes the quality of the composite image extremely poor. FIG. 5 shows a partial pressure meter K, which changes the slope of the unmodified background control signal Bc,
This is a graph showing the effect of More specifically, if K, is set to 1, Ec will be directly proportional to the relative blue luminance, as shown by the straight line with the smaller slope in FIG. If this is shared with the parameters shown in FIG. It will appear as a somewhat bright shadow in the image. To raise Ec to a level of 1.0 or higher for all backgrounds, including arcuate folds, set the partial pressure meter K to a value of 2.

Under this condition, the background control voltage Ec that causes a 50% brightness blue screen to occur is 1.0, as indicated by point 260' in FIG. Of course, walls, floors, and even stair panels with a relative brightness of more than 50% will provide a background control voltage Ec greater than 1, thereby causing an undesirable excessive brightness of the background. . As mentioned above, this problem is
This is overcome by using an IJ meter 284 to keep the modified background control signal EBG at a maximum value of 1.0. FIG. 6 then shows the relationship between the modified or modified background control signal EBc and the unmodified background control signal Ec.

Before going into the details of FIG. 6, it should be noted that if the partial pressure meter K. is set to 2, a shadow having a relative brightness of about 40% will be created, as shown by point 262 in FIG. First, care should be taken to provide a background control voltage. As a result, the intensity of the shadow is greatly reduced so that it hardly appears as a shadow. As mentioned above, the partial pressure meter Ks
, operational amplifier 246, and multiplier 248 overcome this problem. In detail, as mentioned above, the partial pressure meter K
, becomes 1.0 or greater, operational amplifier 246 is disabled and multiplier 248 is no longer provided with an input. Instead, the unmodified control voltage Ec is passed through a straight line multiplier. However, the partial pressure meter K,
As soon as the output of
immediately responds to Ks with a modified background control voltage E8
A step function is introduced into the formation process of G in comparison with Ec. Continuing with the shading example above,
Assume Ks is set to 0.5. In that case, the unmodified background control voltage Ec of level 0.8
produces a modified background control voltage EBG of 0.4. Referring to FIGS. 4 and 5, it goes without saying that this is the original value of the shadow of the actor on the wall. More generally, if the reciprocal of the value of the partial pressure meter K, is used as the value of Ks, all shadows will return to their normal intensity levels. On the other hand, if it is desired to make the shading somewhat stronger, the value of Ks may be selected to be a little smaller by d. As a concrete example, considering a Ks of 0.4, a shadow producing an Ec of 0.8 will produce a modified background control voltage EBG slightly larger than 0.3, thereby making it stronger, i.e. more A dark shadow will appear.

Similarly, by using a value of 0.6 or 0.7 for Ks, the original shading effect is reduced or softened and the shading intensity is reduced. Another important parameter that must be configured is the blue clamp level.

In considering Figure 2, it will be recalled that the blue clamp value obtained from that circuit was: BcSG 10 (G-R) + 10 (R-G) + '5' Similar to this Functions are also formed in Figures 3A and 3B.

The function is obtained mainly by the use of partial pressure gauges KM and KB, where the subscripts "M" and "B"
represent magenta and blue, respectively. Specifically, the circuit of Figure 3 generates a blue lamp with the following values: BcSG 10 KB (G-R) 10 KN (R-G) +
{7) Inspecting Figures 3A and 3B, it can be seen that the blue video is clamped in circuits 241 and 242, and the clamp signal is provided on the negative input lead 244 of operational amplifier 241.

To illustrate the operation of the limiter circuit, the function of the equation occurring at the input to the operational amplifier 245 is equal to 0.5, in which case the input foreground blue and the limit function range from 0 to 1.
．． Assume that there are up to 0. Furthermore, let us first assume that the input foreground blue is 1/4 or 0.25.
Under these conditions, 0.25 is applied to the positive input of operational amplifier 241, and 0.5 is applied to the negative input.
Its output will be -0.25 volts. This negative voltage is
Since it is canceled by the "zero clip" circuit 266, the blue signal at level 0.25 is allowed to pass through the circuit 242 as is. On the other hand, if the blue signal applied to operational amplifier 241 is equal to 3/4 or 0.75, then positive 0.
25 passes through a zero clip circuit 266 to the amplifier 242.
appears at the negative input of , the level of the green signal is reduced to 0.5. This is the assumed level of the limiting function on lead 244. As mentioned above, 3A and 3
The circuit shown in Figure B includes several switches which allow the analysis of the signal being processed and the application of certain special effects.

For example, switch S, when actuated, causes the entire foreground signal, including the blue screen signal, to be transmitted to the output of the device. This is done by disabling the blue clamp Bc and reducing it to zero. switch S
, applies -5 volts to point 268 of the circuit during operation;
This causes the positive terminal of operational amplifier 270 in the blue clamp circuit and the operational amplifier 27 in the background control voltage generation circuit to
A substantially negative voltage is applied to the positive terminal of 2. When the blue clamp voltage is removed and the Bc signal is reduced to zero, the entire foreground video, including the blue screen signal, is transmitted to output terminals 209-212. Switch S2 forms the background enable circuit.

S2 provides 112 volts to the collectors in OR circuit 276 in its normal position. When switch S2 is switched to the ground position, the collectors are grounded and EBG goes to zero. Of course, this disables the background. That is, when S2 is switched, only the superimposed foreground image appears and the background is erased. Switch S3 "gives a representation of the entire background without foreground.

This is done by two switches, both designated S3, the first of which has the reference number 2.
Also indicated by 78, while a second switch for disabling the foreground is indicated by reference numeral 280'. When switch 278 is switched to its operating position, it supplies 112 volts to OR circuit 276, thereby nullifying any Ec signal and bringing EB to its maximum level. so that the entire background video is supplied by giving Switch 280 connects operational amplifier 282
Disable the foreground by connecting the live terminal of to -5 volts. This causes the outputs of amplifier 282 and limiter 284 to decrease to zero, and when this output factor is applied to multipliers 291 and 294, their outputs also decrease to zero. When switch S4 is activated, switch 280 performs some of the same functions as S3.

That is, the foreground video is disabled and erased, and the background is enabled as if the foreground were present. This creates a "hole" or obliterating dark space in the background. To realize some special effects, for example, if it is desired to fill the figure of a foreground person with a monochromatic or mixed-color signal, switch S4 is activated. This will help achieve that purpose.
It is provided at the bottom of the figure, and a video window generating circuit 300 is connected to this key-in terminal.

As shown in the small signal diagram near the key-in terminal 298, when an 11 volt signal is applied to the key-in terminal, the foreground signal is turned off and the background video is turned on. This key-in action is utilized for several useful purposes. For example, if you want to use a blue screen effect only in a certain part of the total representation area, you can use a video window generator to completely nullify the foreground signal for the majority of the image. However,
Control signals are sent to the circuit of FIG. 3A in normal operation for the subarea that is desired to be controlled according to standard blue screen usage. Therefore, for this small field, the window generator reduces the voltage at the key-in terminal 298 to zero, but during the display of the remaining video signal it supplies a signal at the level of 11 volts to the key-in terminal. become. Additionally, if desired, the key-in terminal 298
It is also possible to apply a gradient voltage to the image, thereby making it possible to gradually make the foreground actor invisible. A key-out terminal 302 may also be provided to indicate when the background signal enabling voltage EBo is turned on or off. This can be used for special effects and to generate timing signals to control the duration of signals applied to the device. Incidentally, for completeness of explanation, reference is made once again to equation '8} above.

Now rewrite this equation in slightly modified form: Ec;2. Arc,′{B-1.5[K2(KR
RORKGG) 10 (1-K2) (KRRANDKGG)
]} (IQ This equation is only a slight modification of equation ■.

Specifically, amplifier 272 actually produces a gain of 2.5, so voltage divider K, has a range from 0 to 2.5 volts. Also, a factor of 1.5 is assigned to the constant “C” in Equation 8, and this factor of 1.5 is given by the gain of amplifier 237. In terms of color standards, in the present invention, and in common practice in the film and television industry, the visible spectrum extending from 400 millimicrons to 700 millimicrons is divided into three color bands.

That is, the blue band ranges from 400 to 500 mm, the green band ranges from 500 to 600 mm, and the red band ranges from 600 to 700 mm. The band size from 500 to 700 millimicrons is yellow or “blue lack band size”, and the magenta or “green lack band size” is 400 mm.
The 400 to 600 millimicron band is known as the "red defect" or cyan band.

Finally, the circuits in FIGS. 2 and 3 are implementations of equations '1-{6- and '7} and ■, respectively, and other functions described herein, using specific logic circuits. It should be noted that this is only .

Additionally, of course, both the foreground and background video signal sources can be sourced from an operating TV camera, a videotape, film being scanned by a suitable scanning device, or any combination of these, or any other known video signal source. It will also be appreciated that those skilled in the art may implement the invention using logic circuits of different constructions and other known electronic techniques without departing from the elaboration and scope of the invention. Please note that it should be.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram showing the main elements of the device of the invention. 2b and 2b are detailed logic circuit diagrams of one embodiment of the present invention for implementing the video control equation {1stitch'61. Figures 3a and 3b are logic diagrams of other alternative embodiments of the present invention for implementing Equations 7 and 8. Figures 4, 5, and 6 are
2 is a graph of functions associated with the circuit shown; 12... Foreground video signal source, 14... Background video signal source, 16.
. . . monitor, 18 . . . foreground blue video and background video control circuitry, 34 . . . scanning and beam control circuitry, 1
36...Mixer circuit, 38...Gate amplifier. thing. 4 Takuta J. Tatsutomu. A lot of people. 6. 〆Kyouyu-2・d Mi・Sano Z,. 3 mu. ib

Claims (1)

[Scope of Claims] 1. An electronic synthesis device for monochromatic screen video images, comprising: a source of a color foreground video signal containing signals representing foreground colors including at least red, green, and blue; , a signal source of a background video signal; between a level function value of a first color of one of said scenes and a function value of a second color level and a third color level of said foreground color; apparatus for generating a background control voltage having a value that is a function of the difference; apparatus for controlling the level of a background video signal according to the value of the background control voltage; and a combined foreground video signal and background representing a composite image. Apparatus for combining modified foreground and background video signals to form a video signal and a signal extracted from a background control voltage to remove discoloration in the composite image caused by color components of the screen. and a device for subtracting a background video signal from a background video signal. 2. The electronic video image synthesis device according to claim 1, wherein the background control voltage is dependent on a slope function at low levels, has a horizontal region or limited region at high levels, and has a horizontal region or limited region at high levels; by generating the background control voltage which depends on a step function between so that the level of the background video signal is not affected by changes in the color intensity of the screen and that shading effects are incorporated into the composite image representation accordingly. An electronic video image synthesis device. 3. The electronic video image compositing device of claim 1, wherein the foreground includes colors having a high level of the first color as compared to when the foreground includes colors having a low level of the first color.
A switch device (S_1F) for selectively switching the function that provides the background control voltage
g. 2b), wherein the device for generating the background control voltage includes: 4. An electronic video image composition device according to claim 1, which comprises a device (K_1 and K_2) for generating said background control voltage for reducing the effect of variations in the brightness of a monochromatic screen forming a background with respect to a foreground. An electronic video image synthesis device comprising an apparatus for 5. The electronic video image compositing device according to claim 1, wherein the device for generating the background control voltage includes a device (Ks) for changing the intensity of shadows caused by the foreground in the composite image representation. An electronic video image synthesis device. 6. An electronic video image composition device of the monochromatic screen type, comprising: a source of a color foreground video signal containing signals representing foreground colors including at least red, green, and blue; and a source of a background video signal. and a first of the foreground colors corresponding to the monochromatic screen color.
an apparatus for generating a background control voltage having a value that is a function of the difference between a function value of a color level and a function value of a second color level and a third color level; an apparatus for controlling a background video signal level including reducing the background video signal level to a fraction of its normal level according to a value of the level of a second color of the foreground color; a device for generating a clamp voltage having a value given by the sum of a function value of the difference obtained by subtracting a color of a lesser level from a color of a greater level among the remaining two colors; a device for limiting the value of the background video signal of said first color; and comprising a foreground video signal and a background video signal of reduced intensity in selected areas for displaying partially transparent objects. An apparatus for synthesizing a foreground video signal modified to represent a composite image and an apparatus for synthesizing a background video signal. 7. The electronic video image compositing device of claim 6, wherein the foreground includes colors having a high level of the first color as compared to the case where the foreground includes colors having a low level of the first color.
A control switch device for selectively switching a function providing said background control voltage when including various colors having colors. (S_1Fg.2a), wherein the device for generating the background control voltage includes: (S_1Fg.2a); 8. Device for electronic synthesis of video images according to claim 6, for reducing the effect of variations in the brightness of said monochromatic screen forming the background relative to the foreground (K_1)
and K_2), wherein the device for generating the background control voltage includes: 9. The electronic video image compositing device according to claim 6, wherein the device for generating the background control voltage includes a device (Ks) for changing the intensity of shadows caused by the foreground in the composite image representation. An electronic video image synthesis device. 10. The electronic video image synthesis apparatus of claim 6, wherein the amount of noise introduced into the background control voltage is reduced in response to relative instantaneous values of the second and third color levels. an apparatus for reducing the degree to which the background control voltage depends on either the second or third color, such that the value of the background control voltage is determined only by the instantaneous values of the other two foreground colors; The present invention includes the apparatus for reducing the amount of noise by causing the noise to decrease. Electronic composition of video images. 11 Claim 6
2. The electronic video image synthesis device according to claim 1, wherein the clamping voltage generator selects a value given by the function value of the second color level or the sum of the function value and the difference function value. An electronic video image compositing device comprising a switching device for 12. The electronic video image compositing device according to claim 6, wherein the monochromatic screen has a blue color. 13. The electronic video image synthesis device according to claim 6, for changing the clamp voltage and the background video control voltage simultaneously 180Fig. 2
B) An electronic video image synthesis device comprising: 14. An electronic video image composition device according to claim 8, wherein the device (K_1,
K_2, 158) and a device (Ks) for modifying the background video control voltage to restore the shading effect to a desired level. Electronic composition of video images. 15 Claim 6
An electronic synthesis device for video images of the term E_C=K
_1 {B'-C[K_2(K_R R OR K_GG
)+(1-K_2)(K_R R AND K_GG)
]}where K_1 and K_2 are variable control constants, C is a circuit constant, B' is a signal value representing the first color level corresponding to the color of the monochromatic screen, and R and G are signal values representative of said second and third colors, K_R and K_G are variable control constants, and said background video control voltage, substantially represented by said function E_C, is generated from the video image electronics. Expression synthesizer. 16. The electronic video image compositing device of claim 6, wherein the background control voltage generator turns on the background video signal when the foreground video signal originates from a special color screen, so that foreground objects are a device for generating an original background control voltage E_C that turns off the background video signal when being scanned; a multiplier device for multiplying the original background control voltage by a preset variable factor; and a predetermined low intensity region. a device Ks for reproducing a shadow level of a desired intensity by canceling the effect of the multiplier in the background; and a device for controlling the level of the background video signal using the resulting final background control voltage E_B_G. Electronic composition of special color screen or background type video images, which includes a control voltage generator. 17. The electronic video image synthesis apparatus of claim 16, including a limiter for limiting the final background control voltage to prevent undesirable excessive brightness and brightness changes in the background video signal. An electronic composite of video images, wherein the background control voltage includes a device 284. 18. The electronic video image synthesis device of claim 16, wherein the final background control voltage is dependent on a slope function at low levels and has a horizontal or limiting area at high levels, generating the background control voltage depending on a step function between the video and video signals so that the level of the background video signal is unaffected by changes in the screen intensity and that shading effects are incorporated into the composite image representation accordingly; Electronic image compositing device. 19. An electronic video image synthesis device according to claim 6, wherein the signal representing the blue level of the foreground color is filtered and modified, and the signal representing the blue level of the foreground color is determined by the relative levels of the other two colors. means (238, 240, 242
), wherein said background control voltage generator comprises: