JPS62262579A - Correction and control circuit for scanning crt electron beam - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a scanning CRT (shadow constant) which periodically traverses a CRT target screen horizontally and vertically and periodically generates a series of visible image frames thereon. (Answer) Concerning a correction circuit for electron beams. That is, the control circuit of the present invention performs dynamic focus correction (dy
namic focus COrreCt i On), and can also be applied to achieve desired bin cushion modifications for CRTs.

(Prior Art and Problems) In a CRT device, the electron beam has to travel different distances to the CRT screen depending on its horizontal and vertical deflection, so when the beam crosses the CRT screen, it is difficult to direct the beam to the CRT screen. It is known that adjustments are necessary for proper focusing. This is typically done by applying a predetermined varying dynamic focus voltage to the CRT focusing control grid electrode. Bafaro U.S. Pat. No. 4, assigned in recognition of the present invention.
．． No. 214,188 describes such a dynamic focus β
One example of a positive circuit is disclosed, in which the horizontal and vertical parabolic signals corresponding to the electron beam position are effectively summed together to form a resultant focusing voltage to be applied to the CRT focusing north pole. A signal is generated. Although this system is certainly an improvement in providing a fixed DC voltage to the CRT focusing electrode, the actual desired variation in focusing voltage as a function of horizontal and vertical beam position is It has been found that it cannot be accurately represented by a composite signal generated by summing vertical parabolic signals. Also, any adjustment made to either of the parabolic input signals to be summed will result in a change in the center focus voltage and all other focus voltages, thereby causing each time either input signal is adjusted. The next focus voltage readjustment became necessary.

U.S. Patent No. 4,230,972 issued to Buffer 0
No. 6, also assigned to the assignee of this invention,
An improved dynamic focus correction circuit is disclosed in which vertical and horizontal parabolic signals are multiplied to provide a composite product signal to the focusing electrode of a CRT. This conventional system more closely provides the desired variation in focusing electrode voltage as a function of electron beam position. However, the said No. 4,230,97
The focus correction circuit shown in the '2 patent is difficult to adjust to achieve the desired focus voltage change for any CRT. This means that any adjustment of either the vertical or horizontal parabolic input signal to be multiplied will change the overall dynamic focusing product signal, and many adjustments will be required before a reasonable compromise on focusing voltage changes can be accepted. This is because it requires repetition. The system of patent No. 4.230.972 is
Another effective DC adjustment to the jq product signal is contemplated by multiplication of the vertical and horizontal parabolic signals to produce individually adjustable predetermined DC output levels that determine the center screen focus. Note, however, that adjusting either the vertical or horizontal signals to be multiplied will require subsequent readjustment of the center screen focus. Adjusting the magnitude of each of the horizontal parabolic input signals separately required many adjustment iterations before a compromise focused voltage change that approximated the desired change was achieved.

It should also be noted that effective multiplication of the vertical and horizontal beam position parabolic signals was also used in the bin cushion correction circuit for CRT correction. One example of such a bin cushion correction circuit is the Oliver
No. 4,496,882, issued to et al., also assigned to the same assignee as the present invention. In such a bin cushion correction circuit,
Many similar iterative adjustments of the horizontal and vertical radial signals were required to produce the desired change in bin cushion correction voltage as a function of electron beam position.

OBJECTS OF THE INVENTION It is an object of the present invention to provide an improved scanning CRT electron beam control circuit applicable to dynamic focus and/or bottle cushion correction, which can overcome the above-mentioned drawbacks of conventional correction circuits. It is. A more specific object is to provide an improved correction circuit that is more easily adjustable to obtain a desired correction signal that varies as a function of electron beam position.

SUMMARY OF THE INVENTION In one embodiment of the invention, a control is applicable to dynamic focus modification and/or bin cushion modification of a scanning CRT electron beam that defines at least one image frame on a target screen. A circuit is provided. the! II
The control circuit is configured to generate a first signal that varies in magnitude according to the horizontal position of the scanning electron beam used to generate at least one image frame on the CR-r.
means for generating a second signal that varies in magnitude according to the vertical position of the scanning electron beam used to generate the image frame;
coupling means for receiving the first and second signals and generating a composite signal that varies in magnitude as a function of an effective combination of magnitudes of the signals; and at least responsive to the composite signal. and apply the desired CR to the CRT' electrode.
circuit means for receiving and providing an electron beam modification signal, the desired modification signal varying in magnitude between a local maximum value and a minimum value during generation of said image frame at least in accordance with the amplitude of said composite signal; and the circuit means includes centering means for clamping at least one of the maximum and minimum values of the modified signal to an adjustable DC signal level.

OPERATION As mentioned above, the present invention requires the use of at least vertical and horizontal beam position signals and effective adjustable clamping of the composite correction signal. Preferably, the combining means is a multiplier means and the composite signal is a product signal corresponding to the product of the first and second signals. Additionally, additional top/bottom correction signals related to the vertical position of the electron beam may be used to provide a composite signal that is dependent on the product signal and the top/bottom signal. The composite signal determines the appropriate desired correction signal applicable for dynamic focus correction. The top/bottom correction signal may be added to the product signal to provide a composite signal whose magnitude determines the desired correction signal. The first signal associated with horizontal position and the second and top/bottom signals associated with vertical position also include repeating parabolic signals indicative of electron beam position. It is generally understood how the parabolic signal is generated in response to horizontal and vertical synchronization pulses that effectively define the boundaries of the CRT image frame to be generated.

A feature of the present invention is that the present invention allows the CRT
Non-repetitive adjustment of the focusing voltage is allowed. This is provided by center adjustment means that adjustably peak clamps the modified signal so that this clamped peak level does not change with subsequent adjustments to the modified signal. This provides a 1q advantage to the system if the combiner is either an adder or a multiplier. Further, the first and second clamping means generate first and second signals whose peak values are clamped as the first and second signals, respectively. The multiplier means clamps the first and second
effectively multiplying the signals to generate the product signal. First,
Because the second signals are typically significantly different in frequency, the product signal has a higher frequency carrier signal with a modulation envelope defined by the lower frequency signal. Peak clamping of the first and second signals causes the product signal to have one envelope boundary that is approximately constant and the other envelope boundary that varies in response to the low frequency vertical parabolic signal. This product signal is combined with a top/bottom correction signal that varies with vertical beam position to generate a composite signal that determines the desired correction signal.

A method of generating a non-repetitive focusing correction signal for a CRT lighting beam using the present invention includes the following steps. First, the clamped horizontal and vertical parabolic signals applied to the multiplying multipliers are adjusted to a minimum variation so that the multipliers produce a constant, unchanging product output signal. The top/bottom correction signal corresponding to the vertical beam position signal is also adjusted to a minimum change. The center adjustment means are then adjusted so that the CRT electron beam has optimum convergence at the center of the screen providing the image frame. Next, increase the magnitude change (full width) of the top/bottom correction signal to
Center the top of the image frame given to the screen,
and/or for optimal convergence at the bottom center. Next, the large jagged variation of the clamped horizontal parabolic signal given as input to the multiplier is increased and adjusted to be optimal at the top and/or bottom left and right corners of the given image frame on the CRT screen. so that the focus can be obtained. Next, the fourth and final step in the focusing adjustment is to increase the magnitude variation (carrier) of the clamped vertical signal provided as input to the multiplier to obtain the best fit for the right-center side of the image frame. Ensure that convergence is obtained. This method of focus adjustment does not require readjustment of center, top/bottom, corner or side alignment. This represents a greatly improved technique for more easily obtaining the desired focused voltage variation for a CRT electron beam. The present invention provides a method for determining the convergence voltage variation as a function of beam position, which closely corresponds to the optimum convergence voltage variation required for a particular CRT.
It makes it possible to obtain the desired focusing voltage changes and on the other hand to greatly reduce the effort required for the focusing adjustment.

How the above objects and advantages of the present invention are achieved, as well as the operation of the structure contemplated by the present invention, will be more clearly understood from the following description, which fully explains its operation.

EXAMPLE FIG. 1 shows a dynamic focus adjustment system 10 for a scanning CRT electron beam. The system includes a dynamic focus correction circuit that generates a desired focus correction signal 100 at an output terminal 11 connected to a CRT focus electrode 12 of a CRT (cathode ray tube) 13. A scanning electron beam 13AG is used to generate an image on the tcRT target screen 14 containing successive visible image frames. Further details of the CRT 13 are omitted here because they are conventional and can be easily understood. Place the image on the target screen 14
It is known that due to the horizontal and vertical deflections of the electron beam required for scanning, it is necessary to adjust the focusing of the beam 13A to obtain a bright and sharp image on the target screen 14. This can be accomplished by providing a focused voltage signal that varies in magnitude depending on the vertical and horizontal position of the electron beam.

FIG. 2a shows a front view of target screen 14 where the desired voltage potential for CRT focus correction signal 100 is expressed as a function of beam position on the target screen for a particular CRT. Second
Figure a crosses the top of the screen, indicated by the letter T, to the upper left corner, J, and upper right corner (6 for TLC and TRC>).
00 volts is desired, and +100 volts is desired for top center (TC) and bottom center (BG>).
+200 volts are desired at the center of the target screen (LC) and right side center (SRC), and zero volts is desired at the center of the target screen (C). Although this focusing voltage variation is typical of CRTs, the absolute values of these voltages may differ in magnitude for each CRT. The bottom of the screen, indicated by the letter B, repeats the voltage pattern at the top of the screen. As mentioned above, U.S. Pat. the desired changes). However, this patent does not provide a system that can be easily and non-repetitively adjusted to obtain the desired focus voltage change as a function of electron beam position.

Returning to FIG. 1, the explanation will continue. A vertical synchronization pulse is applied to an input terminal 15 which is connected as an input to a vertical parabola circuit 16 which generates a periodic vertical parabola signal corresponding to a terminal 17 . Similarly, a horizontal synchronization pulse is applied to an input terminal 18 which is connected as an input to a horizontal parabolic circuit 19 which generates a periodic horizontal parabolic signal at an output terminal 20. terminal 15
The vertical and horizontal sync pulses applied to and 18 are
corresponds to the synchronization pulses used by the electron beam deflection circuits to determine the vertical and horizontal position of the beam to form the desired image frame by frame on the target 14, which is conventional for CRT electron beam control; should be understood. The vertical and horizontal parabolic signals reflect the electron beam 13A as the deflection circuit actually sweeps the beam across the target screen 14.
The size changes depending on the vertical and horizontal position of.

Vertical and horizontal parabolic circuits 16 and 19 are conventional as they are typically used in vertical and horizontal beam deflection control circuits that determine the position of the electron beam. Therefore, details of the construction of circuits 16, 19 are omitted. The vertical parabolic signal at terminal 17 typically has a frequency of 60 to 80)-IZ, as before, and 15
The peak-to-peak change amplitude of V is a parabolic signal. terminal 20
The horizontal parabolic signal at has a peak-to-peak width variation of the IOV and a frequency of preferably 50-80 KHz, somewhat higher than the conventional 15 KHz CRT horizontal sweep frequency. Even if only the normal 15 KH2 horizontal sweep frequency is used, the CRT horizontal parabolic signal frequency is typically much higher than the vertical parabolic signal frequency J2.

The horizontal parabolic signal at terminal 20 is coupled to input terminal 22 via DC isolation coupling capacitor 21 to provide a signal 3W101 that is symmetrical with respect to ground potential.

Similarly, the vertical parabolic signal at terminal 17 is coupled to input terminal 25 via isolation capacitor 24 to provide signal 102. Input terminals 22 and 25 are each connected to terminals 30 and 3, respectively.
Adjustable tap (wiper) arm 2 connected directly to 1
Fixed resistance element of potentiometer with 8 26.27
is grounded through. A potentiometer that receives a horizontal parabolic signal at terminal 20 is called an "angle" potentiometer, and a potentiometer that receives a vertical parabolic signal at terminal 17 is called a "lateral °" potentiometer. Angular and lateral potentiometers receive a parabolic signal at terminals 20 and 17, respectively. Signals corresponding to the adjustable portions of signals 101 and 102, respectively, are connected to terminals 30 and 31.
It is used to give. the adjustable portion of the signal at terminals 20 and 17, respectively. Each wiper arm is adjustable between ground and some resistance above ground, which can be applied to -30 and 31.

The waveforms of signals 100, 101 and 102 at terminals 11, 20 and 17 are schematically illustrated in graphs j, d and a of FIG. In all the graphs in Figure 3,
The vertical axis represents magnitude (amplitude) and the horizontal axis represents time. The frequency of the vertical parabolic signal in graph a is 60~
80 Hz is preferred, and the frequency of the horizontal parabolic signal in graph d of FIG. 3 is between 50 and 80 KHz. However, due to the large imbalance in these frequencies, the horizontal and vertical frequencies are not shown as enlarged as the horizontal frequencies are shown in much smaller proportions to maintain clarity of the drawing. Generally speaking, terminals 30 and 31
The signals at correspond to adjustable portions of the horizontal parabolic signal 101 and the vertical parabolic signal 102 at terminals 20 and 17, respectively.

Terminal 30 connects terminal 30 and integrated circuit multiplier 34
This is an input to a peak clamp circuit including a capacitor a32 connected between the input terminal 33 of multiplier 3
4 may be a Motorola M01496 multiplier or other similar device. A resistor 35 is connected between the +24V voltage source and terminal 33, and a diode 36 has its anode connected to terminal 33 and its cathode connected to terminal 37. The terminal 37 is connected to a +24VN pressure source via a resistor 38, and to the ground potential via a resistor 39 in parallel with a bypass capacitor 40. Elements 32 and 35-4
0 receives the signal at terminal 30 and passes this signal to resistor 35.
38 and 39 configure a peak clamp circuit that clamps the peak to a predetermined DC level set by 38 and 39. The signal 103 shown in graph e of FIG. 3 corresponds to this clamped signal and shows the clamp level 41.

Clamp level 41 is chosen such that the signal 103 at terminal 33 has a positive jaggedness regardless of the normal adjustment of the angular potentiometer, although this adjustment affects the peak-to-peak jaggedness 104 shown in graph e. be done.

A similar clamp circuit is drawn for the vertical parabolic signal at terminal 31. 'This similar clamp circuit includes a capacitor 42 connected between terminals 31 and 43. diode 4
The cathode of 4 is connected to terminal 43, and the anode of this diode is connected to ground via resistor 45 and to the +24V voltage source via resistor 46. Terminal 43 is resistor 43A
It is grounded through and connected to the base of the NPN transistor 47. The NPN transistor 47 has its emitter grounded via a resistor 48 and its collector connected to the four input terminals of the multiplier 34 .

A high frequency bypass capacitor ff150 is connected between the collector and base terminals of transistor 47 so that this transistor amplifies only the relatively low frequencies of the vertical parabolic signal and does not amplify the noise or any high frequency horizontal signals at the base of this transistor 47. It looks like this. resistance 51
is connected between a voltage source of +2 to 4 V and the collector of transistor 47. Components 42-46 constitute a peak clamp circuit for the signal at terminal 31, while transistor 47 inverts and amplifies this clamp signal and provides the inverted signal as an input to multiplier 34.

If an MC1496 integrated circuit is used as multiplier 34, additional circuitry is required to convert the high AC level signal of transistor 47 to a suitable low level AC input to multiplier 34.

The operation of the vertical clamp circuit can be explained by reference to FIG. 3, where an unclamped vertical parabolic signal 102 at terminal 17 is shown in graph a. The corresponding peak-clamped adjustable-magnitude vertical parabolic signal 105 at terminal 43 has a minimum peak clamped to a positive DC level 53, as shown in graph b of FIG.

The amplified, inverted signal provided by transistor 47 at terminal 49 is shown as signal 107 in FIG. 3, graph C. Signal 107 inverts signal 105 to match level 53 or the highest level 107A of signal 107;
Although amplified, this signal Q107 never goes below ground potential during normal adjustment of the side potentiometer.

As previously mentioned, the clamped input signals g103 and 107 provided as inputs to multiplier 34 do not have negative magnitudes; they both have maximum values clamped to a predetermined positive peak magnitude level. Additionally, the magnitude of AC signals 103 and 107 provided as inputs to multiplier 34 is adjustable depending on the settings of the angular and side potentiometers. This causes the multiplier 34 to output at the output terminal 54 a product signal 108 (
Graph g) in FIG. 3 is given. The minimum value of this product signal is determined by clamp levels 41 and 53, with a fixed peak level 5 relative to the minimum peak level of product signal 108.
5 occurs.

Graph f in FIG. 3 shows a vertical parabolic signal 107 at terminal 49.
The output of multiplier 34 at terminal 54 is shown when the side potentiometer is adjusted to give a nearly zero jagged change to . Graph q of FIG. 3 shows the product signal 108 at terminal 54 when the side potentiometer is adjusted to provide a vertical parabolic variation signal 107 as shown in graph C as an input to multiplier 34. Here, the graph Q is the multiplier 3
4, i.e., a vertical parabola varying in response to signal 107 forms the upper envelope boundary 109 for the product signal 108, and a fixed peak level 55 forms the lower envelope boundary. We should not pay attention to this. Signal 108 corresponds to a chitria signal that varies according to horizontal parabolic signal 103, ie, has the same frequency. Here, the Q-A signal is located between the envelope boundaries 109.55 shown in the graph q.

The change in the upper envelope boundary 109 is controlled by the side potentiometer and is determined by the setting of the side potentiometer and the gain of transistor 47, such that the amount of change in the envelope boundary 109 is easily controlled by adjustment of the side potentiometer.

Multiplier 34 is a vertical and horizontal parabolic signal 107.1
03 and at terminal 54 the product signal 10B which is a function of the vertical and horizontal parabolic input signals applied to terminal 22.25.
occurs. In a broad sense, multiplier 34 can be viewed as a signal combiner in which the product signal 108 corresponds to an output signal that depends on each of the input signals 107.103.

This is because the present invention contemplates an adjustable peak clamp of the modified signal 100, which minimizes the number of repetitions of adjustment in the vehicle installation, even when corresponding to multiplier 34 or adder/subtractor circuits.

Signal 1 at terminals 33 and 49 of multiplier 34
Because of the 03 and 107 peak clamps, this multiplier is approximately a single quadrant.
Works as a multiplier. This provides a fixed minimum reference level (envelope boundary) 55 for the product signal 108, with the upper envelope boundary 109 of the product signal 108 depending on the magnitude of the adjustable vertical parabolic signal 107 at the end, child 49. It is determined. The operation of multiplier 34 can also be understood by considering it as a modulator in which signal 107 modulates the maximum peak of the carrier having the frequency of signal 103 and the minimum peak of multiplier output signal 108 held at a fixed level 55. Can be analyzed.

The multiplier output terminal 54 is connected to the PNP transistor 6
0, and the emitter and base of this transistor are connected to →−24 through resistors 61 and 62, respectively.
V voltage source.

The collector of the transistor 60 is grounded through a resistor 63 and directly connected to a composite terminal 64 to which a composite signal 110 (graph i in FIG. 3) is applied. This composite signal 110 is a sum/difference signal of the product signal 109 at terminal 54 and an additional top/bottom correction signal Q111 (graph h in FIG. 3) applied to one transistor of transistor 60. This top/bottom correction signal has an adjustable tap wiper arm 66 coupled to the emitter of transistor 60 via a series resistive element 65 and a series capacitor 67, resistor 68 connected between terminal 25 and ground. Provided by top/bottom adjustment means consisting of top/bottom potentiometers.

The top/bottom adjustment means consisting of elements 65-68 are connected to terminal 2.
A top/bottom correction signal 111 is applied to the emitter of transistor 60 that varies as an adjustable proportion of the magnitude change of vertical parabolic signal 102 at 5.5. At the collector of transistor 60 including composite terminal 64, the top/bottom correction signal 111 at the emitter of transistor 60 and transistor 60.
A composite signal 110 is obtained in response to the product signal 108 at the base of .

The top/bottom signal 111, shown in graph h of FIG. 3, includes an adjustable magnitude 112. The top/bottom signal varies around the DC bias level 113 determined by elements 60-63, and the signal 11
The magnitude of the 1 change is determined by the top/bottom potentiometer settings. The composite signal j4110 at terminal 64 is the top/bottom signal 111 added to the inverted and amplified version of signal 108 for operation of transistor 60.
corresponds to This composite signal 110 is shown in the graph i in FIG.
It is shown as. The upper envelope 111' of this signal
, which appears to match the upper modulation envelope, but
varies directly as a function of the top/bottom signal 111, the bottom envelope 114 of which is determined by the top envelope 109 of the product signal 108 at terminal 54. The key feature of this signal is that the top envelope 111' is completely a function of the top/bottom signal change, whereas the bottom envelope 111' is a function of the product of the inputs of multiplier 34. . This makes it impossible for the top/bottom envelopes of signal 110 to be adjusted independently. That is, when the partial envelope is adjusted to the desired magnitude change by the top/bottom potentiometer, the magnitude of the bottom envelope 114 is equal to that of the top envelope 111'.
It can be adjusted independently by the side and angle potentiometers without changing.

Terminal 64 from which composite signal 110 is obtained is coupled as an input to the base of NPN transistor 70.

The emitter of the transistor 70 is grounded via a DC bias resistor 71 connected in parallel with a bypass capacitor #72. The collector of transistor 70 is connected to the emitter of NPN transistor 73. transistor 73
The collector of is connected directly to an output terminal 74 which is connected via a load resistor 75 to a voltage source of +900V and via a bias resistor 76 to the base of a transistor 73. The base of the transistor 73 is the bias resistor 7
It is grounded via 7. transistors 70 and 7
3 amplifies and inverts the composite signal 110 at terminal 64;
A high gain cascode transistor configuration is formed that provides this amplified and inverted signal to terminal 74.

Terminal 74 is coupled via an adjustable peak clamp circuit to output terminal 11 from which the desired dynamic convergence voltage signal 100 is obtained. This clamp circuit connects terminals 74 and 11
The container connected between ♀80. and the cathode is connected to terminal 11 and the anode is the "center" potentiometer, 4 which is connected in series with a voltage drop resistor 82B between the +900V positive voltage source and the -300V negative voltage source 8.
2, adjustable tap arm (wiper) of 8
It has a diode 81 connected to 2A. Further, the terminal 11 is connected to a -300V negative voltage source via a resistor 83. The anode of the diode 81 is a resistor 84 connected in series.
and grounded via capacitor ff185.

The center potentiometer provides an adjustable peak clamp level at terminal 11, thereby controlling the desired output signal 10.
0 as a settable predetermined minimum peak threshold 8, shown as corresponding to zero volts in FIG.
6 so that it can be clamped. Resistor 84 and capacity ff
185 helps maintain this clamping action, while capacitor 80 provides DC isolation between the signals at terminals 74 and 11. Voltage drop resistor 82B ensures that only a maximum voltage of +300V is applied to wiper 82A.

The desired focus control voltage signal 100 at terminal 11 is illustrated in graph j of FIG. This corresponds approximately to the signal 110 shown in graph i which has been amplified, inverted and clamped to a minimum peak level corresponding to the adjustable threshold 86 provided by the center potentiometer.

The center potentiometer is CRT target screen 1
Allows proper focusing at the center of 4. Peak clamp circuits 80-85 ensure that subsequent adjustments to composite signal 110 do not affect center screen focus after initial adjustment to optimal center screen focus.

The dynamic A-scatter correction system of the present invention has a dynamic focus voltage of non-1! /! The manner in which the stepback adjustment is implemented to obtain the target screen voltage shown in FIG. 2a will now be described in detail.

Initially, the top/bottom potentiometers and the corner, side potentiometers are each adjusted such that the wiper arm of each of these potentiometers does not provide an AC signal change. Therefore, the output of multiplier 34 at terminal 54 is a fixed DC level 55, and the composite signal at terminal 64 is also at a DC level determined by DC level 55 and the bias circuit for transistor 60. This provides a fixed DC level at the output terminal 11, the magnitude of which is adjustable by means of a central potentiometer. The center potentiometer is then adjusted to obtain optimal focusing at the center of the target screen 14. This is preferably caused by having the electron beam 13A draw a figure on the target screen body and adjusting the center potentiometer until the optimum focus of the figure is 1q at the center of the target screen. As shown in FIG. 2a, this typically results in a pyropotential output at terminal 11, but any other desired nominal output depending on the circuit and CRT characteristics may be obtained. This adjustment sets the clamp level 86 of the signal 100. Once this center screen adjustment is performed,
Optimal focusing at the center of the CRT target screen 14
No other adjustments are required to adjust the q.

After center screen adjustment, the top/bottom potentiometers are adjusted to provide an AC signal change at pressure terminal 11 that varies in response to vertical parabolic signal 102 at terminal 25. This results in a signal 115 at terminal 11 shown in graph k of FIG.

The minimum value of signal 115 is determined by the center potentiometer threshold clamp level 86, and the positive peak of this signal is determined by the top/bottom potentiometer settings. The peaks of signal 115 in graph k correspond to the focused voltage it at the top center and bottom center of each image frame to be applied onto target screen 14. In the graph, this is shown by the TC and BC designations at the top center and bottom center. In this situation, the graphics on the target screen at the top center, bottom center of the target screen 14 are visible, and the top/bottom potentiometers are adjusted until optimal focusing of these graphics is obtained. Typically this is approximately 100 m below the center screen clamp level 86 (pilo bolt).
Occurs on the bolt. Figure 2b shows the focused voltage applied across the target screen 14 after this adjustment. where +1 above the zero center screen voltage
It is noteworthy that 00 volts are obtained in the top and bottom center screen areas.

Following the top/bottom adjustment, adjust the corner potentiometers to obtain optimal focus at the corners of the target screen 14.

It is known that for the upper left and right corners as well as the lower left and right corners, a voltage of about 600 volts above the center screen voltage is desirable for optimal focusing. To accomplish this, the corner potentiometer is adjusted and the figure on the target screen 14 is monitored at the top or bottom corner until optimal focus is obtained.

Once this is achieved, the output voltage signal at terminal 11 is
This corresponds to the waveform of the signal 116 shown in graph 1 of the figure. The signal 116 is such that the gear signal includes a horizontal parabolic signal and the top and bottom envelope boundaries are connected to the transistor 6.
The modulation signal appears to be determined by the top/bottom vertical parabolic signal 111 applied to the zero emitter electrode.

This is similar to conventional systems that rely on applying horizontal and vertical parabolic signals, but results in the inability to produce the desired voltage change across the target screen as shown in Figure 2a. You should be careful.

The generated focusing voltage as a function of beam screen position is shown in Figure 2C.

The next step to achieve the desired focused voltage change on the target screen is to adjust the side potentiometers to provide a vertical parabolic signal of varying magnitude as the input signal to multiplier 34. During this time, the center sides of the target screen 14 (center 5LC on the left side, center 5RC on the right side) are monitored so that optimal focusing of the figures at these positions is achieved. In this case, optimal focusing occurs at a focusing voltage of about 200 volts above the center screen voltage. After this voltage adjustment, the graph j in Figure 3
A signal 100 shown in FIG. 1 is realized and available at terminal 11. Signal 100 is actually signal 116 shown in graph 1
Effective damping of the upper envelope boundary (dampinc+) of
including. This attenuation is 1q depending on the magnitude of the vertical parabolic signal 107 provided as input to the multiplier 34 at terminal 49. However, adjusting the vertical parabolic input signal 107 at terminal 49 has no effect on any of the previous target screen adjustment voltages, so the center, top/bottom center, and top/bottom corners can be adjusted using either the side potentiometer or the optimal They remain at their previous settings when adjusted for side-center focusing. This provides non-repetitive adjustment of the CRT's focusing voltage to produce the desired voltage change of the target screen as shown in FIG. 2a.

Note that FIG. 2C does not show the target screen focus voltage after adjusting the angular potentiometers but before providing any vertical parabolic input to the side potentiometers or multiplier circuit 34. In graph j of FIG.
It appears to be somewhat higher than the focusing voltage in C). However, this is because the variation of the focused voltage signal 100 with an actual horizontal frequency of 50-80 K)-1z compared to a vertical frequency of 60-80 Hz is not shown to the correct scale in Fig. 3. . With an accurate horizontal school, there will be virtually no change in magnitude. However, this would reduce the clarity of FIG. 3 since the individual horizontal movements of the beams on the target screen would not be able to be shown in FIG.

Although specific embodiments of the invention have been shown and described, other modifications and improvements will occur to those skilled in the art.

One such variation is to use the circuit shown in FIG. 1 to obtain similar target screen voltage changes for bin cushion correction. Also, instead of using vertical and horizontal parabolic signals as input signals at terminals 17 and 20, vertical and horizontal slope sweep signals with appropriate changes in polarity at the midpoint are used, and multiplier 34 and top/bottom adjustment devices ( Similar results were obtained using elements 65 to 68).
It is also possible to do so. Additionally, the modified signal peak-clamp output characteristics of the present invention reduce the number of adjustment cycles that would otherwise be required in conventional systems, such as the system of the aforementioned U.S. Pat. No. 4,214,188, where the signal is multiplied However, it is possible to improve the desired correction signal by adding 1q without adding the desired correction signal. All such variations that support the basic principles disclosed and claimed herein are within the scope of the invention.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram of a dynamic focusing correction system according to one embodiment of the present invention, and FIGS. 2a, 2b, and 2c respectively show focusing voltage as a function of screen position of the electron beam. 3a to 3a are each waveform diagrams illustrating signals provided by the system shown in FIG. 1; FIG. 10... Dynamic focusing correction system, 13A... CRT-electron beam, 16... Vertical parabolic circuit, 19... Horizontal parabolic circuit, 26... Angle adjustment device, 27... Side adjustment device , 34... Multiplier, 65... Top/bottom potentiometer, 80-85.
...Central potentiometer.

Claims (1)

Claims: 1. A modified control circuit for a scanning CRT electron beam (13A) that defines at least one image frame on a CRT target screen (14), comprising:
First means (19--
22, 26, 32-33, 35-40), a second beam whose size varies according to the vertical position of the scanning electron beam used to generate the image frame;
second means (16-17,
24, 27, 42-51) are coupled to the first and second means for receiving the first and second signals (103, 107) and for determining the effective magnitude of the first and second signals. coupling means (34) for generating a composite signal (108) that varies in magnitude as a function of the combination, and receiving a desired CRT electron beam modification signal (100) to the CRT electrodes in response to at least said composite signal (108); , circuit means (60-64, 70-85) for providing the desired modification signal (100), the magnitude of which varies at least according to the magnitude of the composite signal during the generation of the image frame. varying between local minimum values, said circuit means adjusting at least one of the maximum/minimum values of said modified signal (100) to an adjustable DC signal level (86);
), comprising center adjustment means (80-85) for clamping at the center of the control circuit. 2. The combining means (34) receives the first and second signals (103, 107) and includes a multiplier means (34) for generating a product signal (108) as the composite signal.
), wherein the magnitude of the product signal varies as a function of the effective product of the first and second magnitudes. 3. Furthermore, the circuit means (60-64, 70-85)
a top/bottom correction signal (1) which varies in magnitude according to the vertical position of said scanning electron beam (13A);
11) to said circuit means;
5-68), the magnitude of the desired modification signal (100) being determined according to the magnitude of both the top/bottom modification signal (111) and the product signal (108);
A control circuit according to claim 2. 4. The circuit devices (60-64, 70-85) convert the top/bottom correction signal (111) into the product signal (108).
a valid signal summation circuit (60-6) for generating a composite signal (110) which is effectively added to the
4), the control circuit according to claim 3. 5. Each of said first and second means generates a first and second signal (103, 107) respectively clamped to a peak value as said first and second signal. 35-40) and the second (42, 43-51
), and wherein said multiplier means (34) multiplies the first and second signals of said peak value clamp to generate said product signal (108). control circuit. 6. The product signal (108) is the first signal (103
) the magnitude of the peak level fixed as one envelope boundary of the effective carrier signal (55)
, and another envelope boundary (109) of said carrier signal.
6. A control circuit according to claim 5, comprising a signal having another peak level that varies according to said second signal (107). 7. A control circuit according to claim 6, wherein said first and second signals (103, 107) include horizontal and vertical electron beam position parabolic signals. 8. independently adjusting the amount of change in magnitude of each of said first (103) and second (107) signals multiplied by multiplier means 34, thereby increasing the magnitude of said product signal (108); Separate corners to adjust (26)
Control circuit according to claim 3, comprising: and side (27) adjustment means. 9. The corner and side adjustment means (26, 27) each include:
The product signal magnitude can be set to be initially constant with respect to the electron beam position, and then the product signal magnitude can be set according to the beam position and the independent settings of said angular and lateral adjustment means (26, 27). 9. A control circuit according to claim 8, which adjusts its magnitude to vary. 10. The control circuit of claim 9, wherein the first and second signal magnitudes each have periodic parabolic waveforms representing horizontal and vertical positions of the electron beam.