KR800000398B1 - Defect compensation systems - Google Patents

Abstract

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Description

Defect Compensation Device for Color Image Recording and Playback Equipment

1 is a block diagram of a video disc player device including a defect compensation device according to an embodiment of the present invention.

2 is a block diagram of a modification of the arrangement of FIG. 1 in accordance with an embodiment of the invention.

The present invention relates to an image defect compensator suitable for use in a color video recorder for reproducing a composite color video signal having an interpolated luminance and chroma signal component, in particular, comb filter separation and defect masking of the composite signal component. It relates to a screen defect compensator which includes the use of a double delay device for signal accumulation for the purpose of masking.

In US Patent No. 3,842,194, issued October 15, 1974 to Jon K. Clemens, a video disc recording and reproducing apparatus is described, wherein the information recorded here is the surface of a disc substrate coated with conductive coating. Helix grooves have the form of geometric change at the bottom.

The reproducing needle including the conductive electrode fixed to the insulating support is placed on the recording groove. As the disk rotates, the needle electrode interacts with the disc coating to form a varying capacitance in accordance with the geometric change of the groove bottom passing under the needle electrode. A suitable circuit connected to the needle electrode shifts the capacitance change into an electrical signal change representing the recorded information.

In a suitable form of the capacitive video disk system described above, the recorded information includes a carrier frequency modulated according to the video signal and is represented in the form of a continuous groove bottom depth change between maximum and minimum depths. In this form of FM carrier recording, the FM detector threshold must be included in the player to obtain a video signal from the recorded FM signal.

To illustrate, the FM detector in the player includes a zero crossing detector that provides output pulses of standard width and amplitude that respond to respective zero crossings of the input signal. This zero-cross detector output is applied to a low pass filter having a pass band that matches the recorded video signal band to develop the desired video signal.

In the operation of a video disc player of the type described above to reproduce a recorded video signal for image display purposes, the problem observed in the image being shown is that it appears intermittently in the form of white or black spots and stripes instead of appropriate image information. These screen defects change in appearance length, width, and holding time. This is not a disruption of the whole video information, but the intermittent appearance of such video combining would be very painful for the viewer. The present invention relates substantially to a compensation device and method for reducing or eliminating such image defects.

The interpretation of this problem turns out that a number of different causes are attributing to the different types of nuisance image points and lines. Some of these causes are related to the record itself defect. Other causes relate to those conditions in a given disc's characterization (ie, the needles come into contact with different types of debris in different areas of the disc groove). It is related to the long use of the disc to be played. Although no more detailed description of image defects exists, there are many other types of causes that will cause problems with non-huge high levels.

Bidebodisc in an application entitled "Method and Apparatus for Defect Detection and Compensation" entitled US Patent No. 477,102, filed June 6, 1974 by John K. Clemens and Michael D. Ross. An apparatus has been announced to effectively mask the effects of signal defects during playback. In this arrangement, the defect detection is performed under comparison between the selected maximum and minimum levels and the instantaneous level of the video signal emitted from the output of the player's FM detector. Substantially this minimum level corresponds to the instantaneous video signal level calculated by this FM detector in response to the input signal frequency at the FM signal deflection range limit. Based on the gain characteristics of this arrangement, which increases the ability of the fault detector to quickly and clearly recognize the onset of faults, the lowpass has a cutoff frequency well above the record video signal frequency with the highest input to the voltage level comparator. It becomes a wideband video signal generated in the filter. Voltage level variations outside the predetermined level region provide a fault indication that drives to control the switched substitution of information from the preceding image line for current information. Because of the general reduction in successive image lines, the assignment of preceding line information is driven with the occurrence of defects, making the image viewer almost unrecognizable.

In order for the information about the preceding picture line to be useful as a substitute for defect masking for current line information, the player device needs to interact with any suitable form of signal accumulation. According to the principle of the present invention, the signal accumulation of the defect compensating device as proposed in the above-mentioned applications No. 477, 102 to Clemens et al. Has realized a relatively economical form. Preferred surrogate signal information here flows out of the 1H delay line with respect to the comb filter circuit used for luminance chromaticity signal separation.

In US Patent No. 3,872,497 of "Signal Converter" dated March 18, 1975 to a number of others, including John G. Amery, an array of comb-type filter circuits for use in video disc player devices was disclosed. These arrangements convert a reproduced composite signal of the "embedded carrier" type (the chromaticity information of the modulated subcarrier in it is buried in the middle band spectrum of the wider luminance signal) into an output synthesized signal similar to that of NTSC. It has a characteristic to make. A comb filter is used to separate the embedded carrier chromaticity signal component from the intermediate band luminance component. Heterodyning step before comb-filtering actually eliminates the "jitter" of the reproduced signal from the clutter of comb-type filter separation operations and uses a single 1H delay line type for the comb-type filter. This is done in a way that enables the use of a relatively inexpensive, relatively narrowband structure for a single delay line.

In the defect compensation device approaching the present invention, as in US Patent No. 3,872,497, luminance / chromatic signal separation is provided, and the 1H delay line used in the comb filter device is used as a substitute signal source for defect masking.

According to an exemplary embodiment of the present invention, the composite color video signal leaked by the FM detector from the FM carrier signal recorded to be reproduced is applied to the modulator to generate an amplitude modulated carrier wave. An electronic switching device for controlling the conversion of the player's operation to normal or defective type supplies the modulator output to the input of the 1H delay line under "normal" conditions. The comb filter circuit processes the delay line input and output to obtain separate luminance and chroma signal components that are processed to be used to control color image display. A fault detector that monitors the FM detector output provides control of the electronic switching device in the event of a fault. That is, in the presence of a fault, the normal supply of the modulator output to the delay line input is stopped, and the surrogate signal flowing out of the delay line output is supplied to the delay line input (instead of the modulator output). The surrogate signal deviation includes the differential phase shift of the carrier and the color subcarrier sideband components of the delay line output for effective defect masking.

In a variation of the arrangement described above, according to another embodiment of the present invention, switching between "normal" and "substitute" signals generates signals present at the video frequency.

The synthesized video signal from the FM detector output is typically supplied to the amplitude modulator input, but under fault detection, the detected portion of the amplitude modulated carrier output of the delay line is substituted.

In the following, the present invention will be described in more detail with reference to the accompanying drawings. In the video disk apparatus of FIG. 1 of the figure, an input FM signal to the signal processing circuit of the player is generated at the terminal R by the video disk pickup circuit 11. As shown, the video disk pickup apparatus is the capacitive type already described above, the structure and the circuit arrangement of the video disk pickup apparatus are also the capacitive type, and the structure and the circuit arrangement of the video disk pickup circuit 11 are described in US Patent No. 3,842,194. General form as shown.

The recording form of the disc to be played out is the frequency-modulated carrier from which the reproduced signal information flows out of terminal R, and the instantaneous carrier frequency shifted within the fixed deviation region has a frequency band (eg, 0 to 3.0) below the deviation region. MHz, which is limited by the amplitude of the video signal occupied (i.e., 3.9 to 6.5 MHz), and displays a continuous image.

The input FM signal at terminal R is fed to a zero crossing detector 15 via a limiter 13 (used to reduce or eliminate the extrapolation width modulation of the input FM signal). This zero-cross detector 15 includes a known type of circuit for providing a fixed amplitude, width, and polarity output pulse in response to each zero-crossing of the limited input FM signal. The pulse output of the zero crossing detector 15 is supplied to an output filter device including a first low pass filter 31 and a second low pass filter 17. In practice, the passband of the output lowpass filter 17 matches the band occupied by the recorded video signal information (eg 0 to 3MHz). The passband of the first low pass filter 31 is wider than the passband of filter 17, and the cutoff frequency (eg, 6 MHz) is higher than the highest recorded video signal frequency. Filter 31 is used as the wideband input filter for the defect detector 30.

The zero crossing detector 15 and its output filtering device form a so-called continuous FM detector and provide an output in the form of a video signal corresponding to modulation of the input FM signal.

As shown, the video signal information reproduced from the disc is Dalton etch. Dalton H. Pritchard, as disclosed in US Pat. No. 3,872,498, issued March 18, 1975, includes a synthetic color video signal encoded in a “buried carrier” form.

The following parameters are assumed to be an indication of the embedded carrier type of the recorded composite color video signal. Where the parameters are (1) where the line frequency (f _M ) corresponds to the United States standard for color TV broadcasting, the color subcarrier frequency is (f's) -195 / 2fs or approximately 1.53 MHz and (2) between 0 and 500 KHz. Subcarrier amplitude modulation modulated by red and blue chrominance signals (RY, BY), ie chromaticity signal, (3) luminance signal, bandwidth of 0.3 MHz, (4) color synchronization component (standard NTSC During the horizontal blanking "back porch" (corresponding to the color synchronization component), a burst of oscillation at the embedded carrier frequency f's in amplitude and reference phase, and the like.

The composite color video signal output of filter 17 is applied to modulator 19, which also accepts carrier waves from carrier wave input terminal J to produce amplitude modulated carrier wave outputs. The carrier frequency f _C at terminal J corresponds to the conversion of the output subcarrier frequency f _S and the embedded subcarrier frequency f ' _{S which} is suitable for transmission on the color TV receiver chromaticity channel. By way of illustration, the desired output, subcarrier frequency (f _S ) corresponds to an NTSC value of 455/2 f _H or approximately 3.58 MHz, so that the frequency (f _C ) of the picture suitable for a carrier at terminal J is 325 f _H or approximately 5.11 MHz. Substitute.

Preferably, modulator 19 is simply balanced, balanced for composite video, and not balanced for f _C input from terminal J. The percentage of modulation of the carrier to be implemented in modulator 19 is kept at a relatively low value (e.g. 20%) due to the proper relationship of input levels. The disc play condition results in undesirable "jitter" of the frequency of the reproduced synthesized signal. As described more fully in US Pat. No. 3,872,497, the carrier at terminal J has substantially the same “jitter” such that the frequency of the heterodyneization and difference of modulator 19 is virtually free of jitter.

Residual band filter 21, coupled to the output of modulator 19, passes the region pass band and the unbalanced carrier. In the lower band (including the modulated differential frequency), the color subcarrier is the desired frequency (f) for output use. _S ) Preferably the carrier frequency f _C falls at the midpoint of the top of the slope of the characteristic of the filter 21 such that a small part of the upper band is also passed.

The output of the residual side waveband filter 21 is supplied to the "normal" signal input terminal N of the electronic switching device 23. The electronic switching device 23 performs the following alternating actions. That is, (1) the signal appearing at the "normal" signal input terminal N is connected to the switching device output terminal 0, or (2) the signal appearing at the "substitute" signal input terminal S is connected to the switching device output terminal 0. Do it. Switching between the "normal" and "substitute" states, respectively, is made by a control signal supplied to the control signal input terminal P.

The output signal at output terminal 0 of the switching device is fed to amplifier 40 which acts as a delay line driver (which is the output of filter 21 in the "normal" type of player operation). To illustrate, amplifier 40 comprises an emitter ground input stage using transistor 41 and a collector ground output stage using transistor 43 having a negative feedback provided between output transistor emitter and input transistor base via feedback resistor 45. Amplifier 40 provides a low impedance source to signal the 1H delay line 50 (of Amperex DL 56 in the figure).

By appropriate selection of the parameters of the output terminal (coil 53 divided by resistor 55) and the input terminal (coil 51 for adjustment), the passband of delay line 50 is slightly higher than the fc of the output color subcarrier (e.g. 5.11 MHz). It is adjusted to achieve a frequency band that extends from the lowest sideband frequency f _S -500MHz to slightly lower (eg 3.08MHz). The delay conveyed by delay line 50 corresponds to the period at line frequency f _H. Therefore, under the "normal" condition, the signal information at the delay line output represents the image information from the image line immediately preceding the image line to indicate the information at the delay line input. The bandwidth indicated for the delay line 50 surrounding the frequency band (e.g. 3.08 to 4.08 MHz) distributed by the interpolated luminance and chroma signal components, and the comb-type filter technique (e.g. As in US Pat. Nos. 3,872,498 and 3,872,497, the intercalated components can be separated.

For this purpose in the device of the figure, a comb filter circuit 70 is provided. The coupling from the output of amplifier 40 was made to feed the delay line input to the comb filter circuit 70. The delay line output is supplied to the comb filter circuit 70 through an amplifier 60. Amplifier 60 provides sufficient signal gain to compensate for the signal attenuation introduced by delay line 50, so that the delayed signal is supplied to the comb filter circuit at a level compared to the non-delayed signal input level. Amplifier 60 includes an emitter ground input stage using transistor 61 and a collector ground output stage using transistor 63. The amplifier output is shown across the emitter resistance provided by the resistance element of potentiometer 64. The fixed amount of negative feedback provided via feedback resistor 65 connected between the output transistor emitter and the input transistor base is supplemented by the adjustable amount of negative feedback provided through series coupling of resistor 66 and capacitor 67. This series combination 66 and 67 is connected between the adjustment terminal of potentiometer 64 and the input transistor base, and the tap adjustment controls the amplifier gain with the optimum level adjustment.

The comb filter circuit 70 provides a pair of outputs to terminals C and L, respectively. Normally, the output at terminal C belongs to the comb filter characteristic of the type which generates a peak value in the odd multiple of the line frequency band and generates an invalid region in multiples of the line frequency, and the frequency transition surrounding the desired output subcarrier frequency (f _S ). Chroma signal components occupying the defined position (f _S ± 500 MHz). The output at terminal L, similar to a comb-shaped filter having a form characteristic that generates an invalid region in the odd multiple of the line frequency band and generates a peak value in multiples of the line frequency, includes a luminance signal component having an intermediate band without embedded subcarrier components. do. ,

Separate components appearing at terminals C and L are applied to signal processing circuit 75 for processing in a form suitable for delivery to color television 80. The color image screening will be developed according to the recorded image information. Where signal delivery is required to the antenna terminals of the television as shown, the signal processing circuit may include a device for recombining the separated components such that the composite signal forms a new composite signal that modulates the appropriate RF carrier. .

The device descriptions in the figures so far relate to player operation under "normal" conditions. Consider a modified form of operation that is suitable for effective masking of screen defects in sequence. Detection of onset of signal defects requiring a player-operated variant is a function of the defect detector 30.

According to the above-described defect detection principle of Mr. Clemens et al., The defect detector 30 interacts as an input filter with a wideband (eg 0 to 6 MHz) low pass filter 31 that receives the pulse output of the zero crossing detector 15. The output pulse filtering of the detector 15 by the defect detector input filter 31 generates a signal, the instantaneous amplitude of which is linearly proportional to the instantaneous frequency of the signal input limited to the zero cross detector 15. The instantaneous detection input frequency change between fmax and fmin (limiting the deflection range of the recorded FM signal) will actually be derived from the instantaneous amplitude of the filter output between the fixed voltage limits (Vmax and Vmin). However, if the instantaneous frequency of the input to detector 15 is only transitioned above fmax, but if the instantaneous amplitude of filter 31 rises above Vmax only, the instantaneous frequency of detector input will drop only below fmin, and the instantaneous amplitude of filter output Will fall below Vmin.

The voltage level comparators 33 and 35 connected to the output of the filter 31 make the same case when the instantaneous amplitude of the output of the filter 31 is out of range from Vmax to Vmin. The high level comparator 33 shows a defect indication during each deviation period of the output amplitude of the filter 31 above the first comparison voltage level set in the vicinity of Vmax. The low level comparator 35 shows a similar characteristic defect indication during each departure period of the filter 31 output amplitude below the first comparison voltage level set in the vicinity of Vmin. Preferably, the first and second comparative voltage levels are set slightly higher than Vmax and slightly lower than Vmin, respectively. This is to ensure that the actual advantage of the desired video information (especially the possibility of having a slight error in the rotational speed of the playing disc slightly out of the effective deflection range of the defect indication) is not a defect result. Inclusion of these tolerances in the comparative level setting does not impair the accuracy of defect detection. This is because the annoying defect to be detected typically should result in actual deviation at frequencies ranging from fmax to fmin. Adder 37 combines the outputs of the two comparators 33 and 35 to provide terminal D with a single fault indication pulse output indicating deviation in either direction from fmax to fmin.

The wideband response of filter 31 drives its output to approximate and follow a sharp onset of signal defects. In other words, under the occurrence of signal defects, the deviation of this filter output beyond the comparative threshold will drive the initial start of the fault indication pulses and be implemented with a short rise time. With the appropriate fast response provided for the device for the combined compensation control (e.g., electronic switching device 23), the player can transition to a compensation form of operation before the output of the narrowband (late response), and the output signal filter 17 Was distributed.

The wideband response of filter 31 also drives its output to closely follow the return of the input signal frequency within a range. Therefore, the termination of the defect indication pulse output of the comparator precedes the associated disturbance termination at the output of the slower response filter 17. This results in the player returning too soon in his mode of operation and indicating that the fault indication pulse output of adder 37 is used as a control signal for the switching device 23. In order to avoid too early termination of defect compensation, it is desirable to provide a device that effectively extends the defect indication pulse at the termination time along the end of the associated disturbance at the output of filter 17.

The switch control signal generator 39 responsive to the defect display pulse at terminal D performs the desired stretching function in signal generation to control the switching state of the electronic switching device 23. A detailed description of a device suitable for performing the function of the switch control signal generator 39 is given on June 6, 1974. wheat. A.L. Baker is a signal switching device of patent application No. 477,103 filed in the United States. This arrangement includes an envelope detector for the fault indication pulse, a resistive load for the fault detector providing a selected discharge time constant for the detector capacitor, and a comparator that references the detection output for the selected threshold voltage.

The switching waveforms developed by the generator 30 for appropriately extended intervals under the detection of signal defects by the detector 30 are applied to the control input terminal P of the switching device 23 to transfer the player to the combined form of operation. In fault-type operation, the "normal" signal path collapses between N and 0, and the "substitute" signal path operates between terminals S and 0. A description of a switching circuit advantageous for performing the function of the switching device 23 is given in US application 477,103 filed by Baker. In Baker's switching device, the "normal" and "substitute" signal paths, respectively, do not include signal phase inversion. In other words, it should be assumed that this characteristic is for the signal path in the switching device 23.

According to the principles of the present invention, the amplitude modulated carrier flowing out of the output of the same delay line 50, which provides a delayed signal for the operation of the comb filter circuit 70, is a "substitute" signal supplied to terminal S of the switching device 23. Used.

Substitute signal outflows are carried out by full-bandpass network 90. The input of this full-pass network is coupled to the output of amplifier 60, and the output is coupled to the switching terminal S. This full-pass network 90 is an antipolar output generated across the emitter resistor 93 and collector resistor 94 and includes a transistor 92 arranged in a divider structure. Each of these outputs is coupled by a resistor 95 connected between the transistor collector and S and by a network formed by a series coupling of capacitor 96 and inductor 97 connected between the transistor emitter and terminal S. The input signal voltage divider includes a potentiometer 91 having an adjustable tap connected to the base of transistor 92. This adjustable input tap provides the ability to make optimal adjustments to the surrogate signal level for effective defect masking.

Preferably, the parameters of the full pass network 90 are chosen to provide substantially the same gain over the entire frequency in the frequency band passed by the delay line 50 (e.g., approximately 3.08-5.11 MHz). On the other hand, it provides a phase characteristic with a difference of substantially 180 ° between the phase shifts introduced at the decay frequencies f _C and f _S. The phase transition of the output carrier frequency f _C in network 90 in the figure is substantially 0 °, while the preferred phase transition of carrier frequency f _S in network 90 is substantially 180 °. As each of these phase transitions, the transition between the current line information appearance at the switch output terminal 0 and the appearance of the preceding line information occurs as the phase continuity for the f _S color subcarrier carrier component and the phase continuity for the f _C carrier component.

Furthermore, the phase transition indicated for the subcarrier frequency component results in a net phase transition of 180 ° at the output subcarrier frequency for the recycle signal passing from the output of amplifier 60 through the circuits 90, 23 and 40 to the delay line input. Therefore, it is confirmed that the following results are obtained during the defect form of operation (when information represents the same image line between the input and output of the delay line). The components at the color subcarrier frequency may appear at the chromaticity signal output terminal C of the comb filter circuit 70, whereby the embedded carrier frequency components will be removed from the signal at the luminance output terminal L.

The specific terminal connection to the DL 56 delay line shown in the above description selects the signal output type inverted from the delay line 50. In this form, the signal component at an odd half of the line frequency (such as the subcarrier frequency) and continuing through the continuous line will appear in phase between the input and output of the delay line during "normal" operation. Because of the phase shift introduced by amplifier 60, this signal will appear at the output of amplifier 60 in inverse relation to the signal at the delay line input. When the two inputs of the comb filter circuit 70 are in this reversed phase, a signal passes through terminal C and is closed at terminal L. On the contrary, when the two inputs of the comb-type filter circuit are in phase relationship, the signal is closed at the terminal C, and the signal passes through the terminal L. In the form of a faulty operation in which the output of amplifier 60 is recirculated to the delay line input, the phase shift described above at subcarrier frequencies within the 90-23-40 channel passes through the subcarrier component to terminal C as desired and is closed at terminal L. The inverse relationship to the comb filter input is established.

The "substituted" signal leaked from the output of amplifier 60 has a narrower bandwidth (e.g., approximately 3.06-5.11MHz) than the "normal" signal bandwidth (e.g. 2.11-5.11MHz) due to the bandwidth limitation of the DL56 delay line shown. . Therefore, the resulting luminance signal components will lose some high frequency components (eg 2MHz and above) and will fall into the rejection notch at the embedded carrier frequency (eg 1.53MHz). This resultant chroma signal component is comb-type filtered without any intervening luminance component. Notwithstanding these drawbacks, the substitutions performed during the defects in the practice of the present invention include sufficient information of appropriate characteristics to provide a very effective masking of troublesome screen defects. Moreover, this desirable result makes it possible to make relatively small expenses for surrogate signal sources.

In addition, the economical substitute signal source provided by the present invention can be used in various forms of the defect detector, although the above-described defect detector 30 such as Mr. Clemens et al. Provides a particularly advantageous compensation device. As shown, the narrowband video signal output filter 17 is shown to receive the output of the thermal cross detector 15 via a defect detector input filter 31. In one variation, filter 17 may directly receive detector 15 output. However, the arrangement shown with the filters 31 and 17 in series will meet the switching speed requirements added to the devices 39 and 23. A larger delay in switching in the form of a defect relative to the beginning of the defect indication pulse is better in series. This is because the delay for filter 31 is common to the switching signal channel and the video output signal in this arrangement. ·

Figure 2 illustrates a variant of the arrangement of Figure 1 already described, which involves the use of switching between normal and surrogate signals in the video signal form. The arrangement arrangement of FIG. 2 includes an electronic switching device 123, which is similar to the form of the electronic switching device of FIG. 2, and performs the following alternating actions. That is, (1) create a signal path between the "normal" signal input terminal N and the switching device output terminal 0, or (2) create a signal path between the "substitute" signal input terminal S and the output terminal 0. Switching between the normal and surrogate states of each is performed by a control signal supplied from the switch control signal generator 139 to the control signal input terminal P. This control signal generator 139 is of the type described in U.S. Application No. 477,103 and, in response to the output of the fault detector (e.g., fault detector 30 of the FIG. 1 arrangement), transfers the video disc player to a fault masking form of operation. Provide appropriate time-switching waveforms. In addition, the "normal" signal path between terminals N and 0 is closed and the "substitute" signal path between terminals S and 0 is activated.

Output terminal 0 of the switching device 123 is connected to the modulated signal input terminal M of the amplitude modulator 119, and carrier input terminal J is also coupled to the output of the carrier source 120. The stationary frequency f _C of the carrier supplied to terminal J by source 120 corresponds to the subcarrier frequency f ' _S and the desired output subcarrier frequency f _S as shown in FIG. 1, and is equal to 325f _M or approximately 5.11. Corresponds to MHz. Preferably, the frequency of the carrier generated by the source 120 varies around the transmission frequency in accordance with the "jitter" of the frequency of the synthesized video signal reproduced during record reproduction. For this reason, the carrier source 120 can perform appropriate control, for example, by a phase closed loop circuit of the type described in US Pat. No. 3,872,497.

The output of modulator 119 is applied to amplifier 140, which is used to drive the 1H delay line 150. As shown, elements 140, 150, and 160 will be of the particular type described above for the associated elements 50, 60, and 70 in the FIG. 1 arrangement. The input signal and the delay line output signal (e.g. useful for the output of the output amplifier 160) are supplied to a suitable comb-type filter circuit (not shown in FIG. 2), so that the desired luminance / as described in connection with FIG. Chromatic signal separation can be achieved. For one particular form of explanation, such comb filter circuits are referred to in US 506,446, filed September 16, 1974.

In contrast to the arrangement of FIG. 1, each input to the switching device 123 is in the form of a composite video signal. This "normal" input signal (i.e., the signal applied to terminal M and transmitted to the signal input terminal M modulated during the normal operation of the player) corresponds to the output of the zero crossing detector (such as detector 15 in the FIG. 1 arrangement). And the output of the player's FM detector emanating from the low pass filter 117 (eg having a 0 to 3 MHz bandwidth) in the FIG. 12 array. This surrogate input signal (a signal applied to terminal S and delivered to the signal input terminal M modulated during the defect masking or the surrogate operation mode of the player's operation) is a delayed composite video signal emanating from the output of delay line 150.

To obtain a "substitute" signal, the output of the delay line output amplifier is applied to an amplitude modulation detector 200 which reproduces the composite video signal from the amplitude modulated carrier output of the delay line. The output of the detector 200 is (1) a low pass filter 210 having a cutoff frequency selected to close the passage of sideband components and carriers at the output of the detector 200 and (2) (e.g., for luminance delay purposes in a color TV receiver). And (3) are supplied to the switching device input terminal S via a signal path including in series a delay element 220 and (3) a DC closing connection element such as the capacitor 230 shown in series.

The above half-cycle delay ensures that the components of the output color subcarrier frequency during the defect masking type can appear properly in the chromatic signal output of the comb filter circuit of the player. On the other hand, components at the embedded carrier frequency can be removed from the luminance signal output. This effect has already been described in relation to the FIG. 1 arrangement.

It has been known that by closing the terminal S passage of the DC component (long period change) of the output of the detector 200, errors can be avoided at the brightness level of the surrogate material which tends to fail the defect masking. To assess the nature of this problem, it is contemplated to use a relatively inexpensive form of glass delay line illustrated by the DC56 line shown in FIG. At one output of such a delay line, the main component corresponding to the delay line input signal, as well as the response to the delay line input signal after three to three rows of delay line, obtains the components. When an amplitude modulated carrier in accordance with a composite video signal passes through this delay line, the component of the carrier magnitude passed by this delay line is related to the peak of the ripple frequency response that characterizes this delay line. It will depend on the precise location of the carrier frequency. Under the modulated carrier output detection of the delay line output, the magnitude of the DC component of the reproduced composite video signal thus depends on this exact position.

In the video disc player of the above-described apparatus, the change in the average turn table speed results in a long-term change in the average value of the embedded subcarrier frequency of the synthesized video signal reproduced during reproduction, and also provides a phase closed loop system for output subcarrier stabilization. The combination of carrier 120 having a definite effect on the magnitude of the DC component of the detected change in delay line output is confronted with a pseudo long term change in carrier frequency position with respect to the ripple peak of the line's response characteristics. This results in a change compared to the average frequency value of the carrier applied to modulator 119.

The deficiency masking effect of the corresponding signal leaked from the output of the delay line of the above-described type is such that the DC component of the detected delay line output and the long term pseudo change can be suppressed in the surrogate signal path by arbitration of the coupling capacitor 230. At the time, it has been found to be improved. The AC coupling in the surrogate signal path of the arrangement arrangement of FIG. 1 does not provide a significant pseudo component suppression effect because the delay signal supplied to the switching device 23 is in the form of a modulated carrier. As described in US application 559,098 filed by James C. Schopp on March 17, 1975, for example, the use of an oscillator reference type speed control device for crystal control results in an average turntable speed. When the ripple is strictly done, the weft component variation range is small enough to achieve proper defect masking by the first degree arrangement. But Al J as dated September 10, 1974. When loose tolerances are received with respect to the average turntable speed, for example from the use of economical speed controllers of power line frequency reference type, as shown in US application 504,486 filed by Mr. Ham Hammond, A two degree arrangement would be preferred.

Claims (1)

As described in the text and illustrated in the drawings, in a system for reproducing a recorded continuous color video signal, An apparatus for extracting a color image reproduction composite video signal comprising a modulated color subcarrier for forming a chromaticity signal having a frequency of a portion of the luminance signal and an intermediate interpolated frequency and the luminance signal during record reproduction; A signal providing circuit comprising a 1H delay line having an input and an output, and a switching circuit responsive to control of an output of said delay line or an output of said composite video signal outflow circuit for providing a signal to an input of said delay line. And a control circuit responsive to an abnormal state of the output of the composite video signal outflow circuit for controlling the operation mode of the signal providing circuit; A color image recording comprising a comb-like filter circuit comprising a signal synthesis circuit coupled to an input and an output of said delay line for separating said luminance and chroma signals and for providing comb filter separation of said luminance and chroma signals; Defect compensator for regeneration device.

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