JP2005197838A - Display apparatus using picture tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the occurrence of a luminance step on a fluorescent screen of the picture tube in under scanning without reducing a display area in the vertical direction. <P>SOLUTION: When a video image is displayed on a color CRT 11 by under scanning because of a difference in the aspect ratio, a microcomputer 16 sets a short vertical blanking period of a vertical blanking signal in a color demodulation circuit 5 synchronously with a horizontal synchronizing signal HD and a vertical synchronizing signal VD separated by a synchronizing separator circuit 4 to widen a display area in the vertical direction and slowly changes a start position and an end position of the vertical blanking at a long time period to suppress the occurrence of a luminance step on the fluorescent screen of the picture tube in the under scanning without reducing the display area in the vertical direction. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a display device using a picture tube that suppresses the occurrence of a step difference in the emission luminance of a phosphor in a long-time video display during underscan relative to the aspect ratio of the phosphor screen of the picture tube.

In general, picture tubes are widely used as display devices in electronic devices such as television receivers and personal computers.
When the underscan operation is performed with respect to the aspect ratio of the fluorescent screen of the picture tube, the electron beam is concentrated at the center of the fluorescent screen. Since the emission luminance of the phosphor in the picture tube decreases with the elapse of the electron beam irradiation time, if the underscan operation is continued for a long time, the emission luminance of the phosphor in the scanning region decreases with respect to the non-scanning region.
For this reason, when the underscan operation is continued for a long time and then the shift to the just scan or overscan operation is performed, the light emission luminance of the phosphor is reduced at the center of the phosphor screen of the picture tube. It appears as a boundary between the video display area and the non-display area or as a luminance step.

For this reason, in conventional receivers, the phase of the synchronization signal supplied to the deflection circuit during the underscan operation is controlled with respect to the aspect ratio of the phosphor screen of the picture tube, so that it is displayed on the phosphor screen of the picture tube. The position of the image to be changed was changed. As a result, even when the underscan operation is continued for a long time, the boundary between the image display and the non-display on the phosphor screen of the picture tube changes, so that it is possible to suppress the occurrence of a luminance step on the picture tube phosphor screen.
FIG. 6 shows a configuration of a main part in a conventional example that performs such processing. A vertical synchronization signal VD separated by a synchronization separation circuit on the front end processor side (not shown) is input to an UP-CONV (double speed processing unit) 51, subjected to double speed processing as necessary, such as progressive display, and then BEP (back End processor) 52.
The vertical synchronization signal VD that has been subjected to the processing of locking to the input signal by the back-end processor 52 is output to the DEF / CONV (deflection circuit) side via the V-Phase (vertical phase control circuit) 53.

The vertical synchronizing signal VD input to the V-Phase (vertical phase control circuit) 53 is controlled by a control signal input to the I / O EXP (input / output expander) 54 through IIC-BUS by a microcomputer (not shown) or the like. The phase of the vertical synchronization signal is controlled.
In the case of this conventional example, in order to change the phase of the synchronizing signal supplied to the vertical synchronizing circuit, an image is displayed on the underscan display area Db on the fluorescent screen of the picture tube as shown in FIG. The shaded area is a non-display area due to the existing vertical blanking period.
In this case, since the phase of the vertical synchronizing signal is changed, the video portion indicated by a circle in the display area also changes. Further, in this conventional example, the V-Phase (vertical phase control circuit) 53 and the I / O EXP (input / output expander) 54 are required, which increases the cost.

As another conventional example, there is an example disclosed in JP-A-7-46510. In this conventional example, the vertical blanking period is repeatedly changed in a long cycle in addition to the disclosure in which the vertical synchronization signal is repeatedly changed in a long cycle as in the conventional example shown in FIG.
JP-A-7-46510

  The conventional example disclosed in Japanese Patent Application Laid-Open No. 7-46510 simply changes the length of the vertical blanking period repeatedly in a long cycle. Therefore, when the vertical blanking period is increased, it is normally displayed. When the display area in the vertical direction to be narrowed and the image is displayed on the full screen, there is a disadvantage that the upper end or part of the lower end in the vertical direction is missing and displayed.

(Object of invention)
The present invention has been made in view of the above points, and suppresses the occurrence of a luminance step on the phosphor screen of the picture tube even if the underscan operation is continued for a long time without narrowing the vertical display area. An object of the present invention is to provide a display device using a picture tube.
In addition, the present invention can be realized easily and at low cost, and suppresses the occurrence of a luminance step on the fluorescent screen of the picture tube even if the underscan operation is continued for a long time without narrowing the existing vertical display area. An object of the present invention is to provide a display device using a picture tube.

A display device using the picture tube of the present invention includes a display area setting means for enlarging the display area of the video signal in the vertical direction during an underscan operation with respect to the aspect ratio of the phosphor screen of the picture tube,
Vertical blanking position changing means for repeatedly changing the vertical blanking start position and end position in a long time in the state of the display area expanded in the vertical direction by the display area setting means;
It is characterized by comprising.
With the above configuration, at least normal display is performed even when the vertical blanking start position and end position change by repeatedly changing the vertical blanking start position and end position over a long period of time in the display area enlarged in the vertical direction. A state in which an image can be displayed in the display area in the vertical direction should be secured, and the occurrence of a luminance step on the phosphor screen of the picture tube can be suppressed.

  According to the present invention, by changing the vertical blanking start position and end position at a predetermined timing in the display area enlarged in the vertical direction, even if the vertical blanking start position and end position change, at least normal display is performed. It is possible to secure a state in which an image can be displayed in the vertical display area to be generated, and to suppress the occurrence of a luminance step on the phosphor screen of the picture tube.

  Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 to 5 relate to Embodiment 1 of the present invention, FIG. 1 shows the overall configuration of a television receiver of Embodiment 1 of the present invention, and FIG. 2 shows three primary color signals to which a vertical synchronizing signal is added. 3 shows one and the vertical deflection signal in that case, FIG. 3 shows the state of image display by the picture tube (color CRT) at the time of underscan in this embodiment, and FIG. 4 changes the vertical blanking period in this embodiment. FIG. 5 shows the processing contents in the modification of FIG. 4.
FIG. 1 shows an example in which a display device using a picture tube of the present invention is applied to a television receiver. The television receiver 1 (hereinafter simply abbreviated as “receiver 1”) has a tuner 2, and a high-frequency signal of a channel selected by the tuner 2 is taken out and converted into an intermediate frequency signal.

Note that the tuner 2 and the like in this embodiment are a normal NTSC television broadcast with an aspect ratio of 4: 3 and a television broadcast with an aspect ratio of 16: 9, specifically, high-definition television (high vision). It is compatible with broadcasting.
The intermediate frequency signal output from the tuner 2 is amplified by the video amplifying circuit 3, further subjected to video detection, and input to the synchronization separation circuit 4 and the color demodulation circuit 5.
The synchronization separation circuit 4 extracts the horizontal synchronization signal HD and the vertical synchronization signal VD from the color television signal, and the extracted horizontal synchronization signal HD and vertical synchronization signal VD are input to the double speed processing circuit 6. Further, the color demodulation circuit 5 performs demodulation processing from the input color television signal to generate a color difference signal, and the generated color difference signal is input to the double speed processing circuit 6.

In the case of a television receiver 1 that supports progressive display, the double speed processing circuit 6 performs double speed scanning processing when receiving an NTSC television broadcast, and the horizontal speed processing circuit 6 performs horizontal scanning at double speed. The converted color difference signal is input to the primary color output circuit 7.
Further, the horizontal synchronization signal HD and the vertical synchronization signal VD of the synchronization separation circuit 4 are also input to the double speed processing circuit 6, and when the color difference signal is doubled as in the case of the color difference signal, the horizontal synchronization signal HD is also Doubled.
The horizontal synchronization signal HD ′ and the vertical synchronization signal VD output from the double speed processing circuit 6 are input to the horizontal deflection circuit 8 and the vertical deflection circuit 9, respectively. The horizontal deflection circuit 8 and the vertical deflection circuit 9 are respectively connected to the horizontal synchronization signal HD. 'And a sawtooth-shaped horizontal deflection signal and vertical deflection signal synchronized with the vertical synchronization signal VD are generated, and the generated horizontal deflection signal and vertical deflection signal are used as a color picture tube (hereinafter referred to as color CRT) 11. To the deflection yoke 12.

The color difference signal input to the primary color output circuit 7 is converted into the three primary color signals by the primary color output circuit 13 configured by a matrix circuit, and then the three primary color signals are output to the CRT drive circuit 14.
The CRT drive circuit 14 amplifies the input three primary color signals and applies them to the cathodes constituting the red, green and blue electron guns of the color CRT 11. Then, the electron beam corresponding to the level of the three primary color signals applied to the cathode is magnetically deflected in the horizontal direction and the vertical direction by the horizontal deflection signal and the vertical deflection signal, and the red, green and blue colors of the color CRT 11 are obtained. A color image captured by the television camera is reproduced by irradiating each of the fluorescent screens with light, respectively emitting red, green and blue light.

Further, the receiver 1 receives an NTSC television signal, and displays a fluorescent display screen (fluorescent screen) by a normal overscan on a color CRT 11 having a vertical and horizontal image display size set to an aspect ratio of 4: 3. (It is also abbreviated as “display surface”) It is set to display the image of the effective number of scanning lines in the standard number of scanning lines (525 lines) on the full vertical and horizontal screen, and when the high-definition signal is received, In order to maintain an aspect ratio of 16: 9, it is possible to display an image by narrowing a display area corresponding to the number of effective scanning lines in the number of scanning lines (1125) in the vertical direction while the screen is full in the horizontal direction. Underscan.
As will be described later, the display area for displaying the video having the effective number of scanning lines is set as an existing display area Db, and in this embodiment, the number of scanning lines above and below the number of scanning lines in the display area Db can be displayed. An enlarged display area Da obtained by enlarging the display area is set as a reference display area.

In the case of an NTSC television signal, the color CRT 11 having an aspect ratio of 4: 3 is displayed on the full screen in the vertical and horizontal directions as described above by the vertical blanking period corresponding to the normal display.
The receiver 1 has a built-in microcomputer (hereinafter abbreviated as microcomputer) 16 that controls the receiver 1, and in this embodiment, the aspect ratio of the phosphor screen of the color CRT 11 is 4: 3. Therefore, when a high-definition signal having an aspect ratio of 16: 9 is received, the vertical deflection circuit 9 is underscanned to display the high-definition signal image in the display area narrowed in the vertical direction as described above. Send control signals for

When a control signal is input from the microcomputer 16, the vertical deflection circuit 9 generates an underscan vertical deflection signal, and the underscan vertical deflection signal is output to the deflection yoke 12. In this case, the electron beam has a narrower scan width in the vertical direction than in the case of NTSC. More specifically, the image of the high-definition signal is displayed at an aspect ratio of 16: 9 by narrowing the upper and lower sides of the vertical display size of the color CRT 11 by about 1/8, and about 1/4 in total. To do.
In this embodiment, in order to suppress the occurrence of a luminance step, the display area in the vertical direction is enlarged in advance than the existing display area Db (see FIG. 3).
For this purpose, the microcomputer 16 takes in the horizontal synchronization signal HD and the vertical synchronization signal VD generated by the synchronization separation circuit 4, and counts, for example, the number of horizontal synchronization signals HD within the period of the vertical synchronization signal VD by an internal counter circuit. Thus, it is determined whether the currently input television signal is the NTSC system or the high-vision system. In both systems, the vertical synchronization signal VD is almost the same, but the period of the horizontal synchronization signal is 15.75 kHz for the former and 33.75 kHz for the latter, so that it can be easily discriminated.

Based on the determination result, an underscan control signal is sent to the vertical deflection circuit 9 to generate an underscan vertical deflection signal and, for example, to a vertical blanking signal generation circuit connected to the color demodulation circuit 5 The width of the vertical blanking period of the standard vertical blanking signal is determined by adding a pulse signal to the standard vertical blanking signal output from the vertical blanking signal generation circuit in reverse of the polarity. For example, a vertical blanking signal (this is called, for example, a reference vertical blanking signal) shortened forward and backward by the limit value is inserted (synthesized) into the color difference signal.
Then, the color difference signal in which the reference vertical blanking signal is inserted is applied to the color CRT 11 as a three-primary color signal indicating one signal component in FIG. By displaying the image to be displayed, the image can be displayed in the enlarged display area Da that is slightly larger in the vertical direction than the existing display area Db in the vertical direction at the time of the existing underscan shown by the two-dot chain line in FIG.

That is, in this display state, the existing video display at the time of underscan is secured, and a little extra video is displayed in the vertical direction. In this way, by expanding the display area in the vertical direction, the display area Db is more effective than the existing display area Db that displays the number of effective scanning lines or the effective number of scanning lines without displaying all the images actually transmitted from the broadcasting station. Display in a wide display state.
Further, in the state in which the existing display area Db is ensured in this way, the microcomputer 16 is vertical with a natural number multiple of the horizontal line as a step width (variable step Δ in the flowchart of FIG. 4) in synchronization with the horizontal synchronization signal HD. The blanking start position and the vertical blanking end position (hereinafter abbreviated as vertical blanking start / end position, etc.) are slowly changed. As will be described later with reference to the flowchart of FIG. 4, the display area from the enlarged display area Da to the display area Db is changed by slowly changing the vertical blanking start / end position (or vertical blanking period) over a long period of time. By using this to display images, the occurrence of a luminance step or the like is suppressed. In this embodiment, it is assumed that the vertical blanking period is lengthened when a variable step Δ is added to the vertical blanking start or end position. The vertical blanking signal and the vertical deflection signal added to the three primary color signals in this case are as shown in FIG.

As shown in FIG. 2A, the CRT drive circuit 14 outputs the three primary color signals to the CRT 11, and the vertical deflection circuit 9 outputs the vertical deflection signal shown in FIG. The
As shown in FIG. 2A, a vertical blanking signal Sv is added to each signal component of the three primary color signals. In this embodiment, the period of the vertical blanking signal Sv, that is, the vertical blanking period. Is slowly changed from Ta to Tb.
As shown in FIG. 2 (A), the vertical blanking period Ta corresponding to the case of the enlarged display area Da is a time before and after the start and end positions of the vertical blanking in the vertical blanking period Tb. The time is shifted by a width L to make a short time width. The vertical blanking period Ta widened by the time width L is synchronized with a timing shifted by a short time width of e, for example, from the rising and falling edges of the sawtooth triangular wave of the vertical deflection signal.

The upper end in the enlarged display area Da in FIG. 3 corresponds to the vertical blanking end position, and the lower end corresponds to the vertical blanking start position.
From this state, the microcomputer 16 is perpendicular to the vertical blanking signal generating circuit of the color demodulating circuit 5 by a variable step Δ corresponding to several lines from one horizontal line (abbreviated as one line) every time a predetermined time elapses. By slowly changing the vertical blanking period, for example, by increasing the blanking period, it is possible to prevent the occurrence of a luminance step on the phosphor screen and the occurrence of a “burn-in phenomenon”. Further, the timing for changing the vertical blanking period by the variable step Δ is performed in synchronization with the horizontal synchronization signal HD, for example, in synchronization with the horizontal blanking period.
Note that the hatched portion in FIG. 3 is displayed in black without displaying the video in the vertical blanking period. Further, the hatched portion of the dotted line becomes an image display area due to a change in the vertical blanking period, or becomes a range (area) where the image is displayed black without being displayed.

As described above, in this embodiment, even if the vertical blanking period is changed, the display area of the video in that case always includes the existing display area Db, and thus does not change the existing display area Db. Secure video in the existing display area.
Next, the operation of displaying an image while preventing the occurrence of a luminance step on the phosphor screen during underscan according to the present embodiment will be described with reference to the flowchart of FIG.
As shown in step S1, when the power is turned on (powered on) by operating the power switch of the receiver 1, each circuit of the receiver 1 is in an operating state and receives a television signal. In that case, the microcomputer 16 counts the horizontal synchronization signal HD input from the synchronization separation circuit 4 and sets the scan range of the vertical deflection signal of the vertical deflection circuit 9 according to the counting result. Further, the microcomputer 16 determines whether or not the under scan is set (or selected) from the measurement result as shown in step S2.

If the underscan setting is not set according to the determination result in step S2, that is, in the case of an NTSC television signal, the video displayed as shown in step S3 is the vertical blanking start / Displayed at the end position (vertical blanking period). After this display (that is, immediately before an operation to turn off the power is performed), as shown in step S4, a process for setting the vertical blanking start / end position which is a reference at the time of underscan is performed and the power is supplied. Is turned off.
On the other hand, if it is determined as a high-definition signal by the determination in step S2, the displayed video is the start / end of the vertical blanking which becomes a reference for underscan which is set longer than the normal display vertical blanking period. Display by position (vertical blanking period).

This display state is an enlarged display area Da in FIG. Then, from this state, the microcomputer 16 starts an internal timer and measures the passage of time. Then, when a predetermined time has elapsed, the process proceeds to step S5, and as shown in step S5, a variable step Δ corresponding to one to several lines is added to the vertical blanking start / end position which is a reference at the time of underscan. Is displayed. In this case, the vertical blanking period is lengthened by the variable step Δ from the enlarged display area Da of FIG.
Therefore, an image is displayed in a display area slightly narrower than in the case of the enlarged display area Da.

In this state a, for example, when a normal display switch operation or the like is performed, the underscan is canceled as shown in step S6. That is, an image is displayed in the vertical blanking period during normal display. In this case, information on the current addition state a is further stored in the internal memory of the microcomputer 16 as a last state, for example. In this case, the timer time measurement is also stopped.
When the normal display switch operation is canceled or the underscan display operation is performed, underscan is again set (selected) as shown in step S7. In this case, the video is displayed in the state a. Also, the time measurement operation by the timer is resumed.
When a predetermined time elapses by the timer in the display state of state a, as shown in step S8, the microcomputer 16 displays an image in the state b in which Δ is further added from the state a to the blanking start / end position.

When a predetermined time has elapsed from this state b, the microcomputer 16 determines whether or not the vertical blanking start / end position in this state exceeds the limit value as shown in step S9. If this determination result does not exceed the limit value, the process returns to step S5 or S6, and is repeated until the lower limit is reached as described in step S10. In this case, the lower limit is the display area Db in FIG. 3 or a display area slightly wider than this.
By performing the processing from step S5 to S10 in this way, the vertical blanking start / end position is slowly changed between the enlarged display area Da and the display area Db (in this case, the upper end of the display area). And the lower end slowly move in synchronism with the lower side and the upper side, and the display area slowly changes from a wide state to a narrow state), thereby effectively preventing the occurrence of a luminance step or the like.

On the other hand, if it is determined in step S9 that the limit value is exceeded, the process from step S5 to S10 is performed in the reverse direction after processing is performed so as not to exceed the limit value in step S11.
First, in step S11, video display is performed in a state c obtained by subtracting a variable step Δ from the vertical blanking start / end position of the previous state b. In this state c, the timer is started. In this state c, for example, when a normal display switch operation or the like is performed, the underscan is canceled as shown in step S12. That is, an image is displayed in the vertical blanking period during normal display. In this case, information on the current subtraction state c is further stored in the internal memory of the microcomputer 16 as, for example, a last state. In this case, the timer time measurement is also stopped.

When the normal display switch operation is canceled or the underscan display operation is performed, underscan is set (selected) again as shown in step S13. In this case, the video is displayed in the state c. Also, the time measurement operation by the timer is resumed.
Then, when a predetermined time elapses by the timer in the display state of state c, as shown in step S14, the microcomputer 16 displays an image in a state d in which Δ is further subtracted from the state c to the blanking start / end position.
When a predetermined time elapses from this state d, the microcomputer 16 determines whether or not the vertical blanking start / end position in this state exceeds the limit value as shown in step S15. If this determination result does not exceed the limit value, the process returns to step S11 or S12, and is repeated until the upper limit is reached as described in step S16.

Note that the upper limit in this case is, for example, the position of the upper end and the lower end corresponding to the enlarged display area Da in FIG. 3, or the position of the end of the display area narrower than that by a variable step Δ. On the other hand, if the limit value is exceeded in step S15, the video is displayed in step S17 with the variable step Δ added to the vertical blanking start / end position in state d so as not to exceed the limit value. Then, it returns to step S5 or step S6, and performs the process mentioned above.
By performing such processing, the vertical blanking start / end position is slowly and repeatedly performed over a long period, so that the boundary between the video display and non-display on the phosphor screen is maintained even if the underscan operation is continued for a long time. Since the line changes, it is possible to effectively prevent the occurrence of a luminance step on the phosphor screen.

Further, in this embodiment, it is possible to effectively prevent the occurrence of a luminance step on the phosphor screen with a simple configuration or method. Further, it can be realized at a low cost.
Further, in this embodiment, when the vertical blanking start / end position is changed, the vertical blanking start / end position is moved in the vertical direction in synchronization with the horizontal synchronizing signal HD by one horizontal line or by a variable step Δ which is a natural number multiple thereof. Therefore, as in the conventional example (Japanese Patent Application Laid-Open No. 7-46510), one of the images at the middle position of the horizontal line that occurs when the upper end or the lower end of the display area is moved without being synchronized with the horizontal synchronization signal HD. It is possible to reliably eliminate the jagged display of the part and maintain a high-quality display state.

In the operation of FIG. 4, the vertical blanking start position and the end position are synchronized or interlocked with the state of the enlarged display area Da in FIG. 3 and the variable step Δ is added together to narrow the display area, or the variable step Δ is changed. The display area was widened by subtraction.
On the other hand, when the variable step Δ is added to one side in synchronization with or interlocked with the vertical blanking start position and end position, it may be subtracted from the other.
FIG. 5 shows the operation in this case. In the case of FIG. 5, the vertical blanking start / end positions as the first reference are set to the positions of the lower end of the enlarged display area Da and the upper end of the display area Db in FIG.

Steps S1 to S3 in FIG. 5 are the same as those in FIG. 4, and step S4 ′ subsequent to step S3 is set to the vertical blanking start / end position as a reference in FIG. 4 as described above.
If the microcomputer 16 determines that an underscan is detected in step S2 after the power supply in step S1 is turned on, the process proceeds to step S25. From step S25 to step S30, in the processing from step S6 to step S10 in FIG. 4, a process of adding a variable step Δ is similarly performed for the vertical blanking start position, and the reverse is performed for the vertical blanking end position. A process of subtracting the variable step Δ is performed. More specifically, if underscan is set or selected in step S2, the vertical blanking start / end position set in step S4 ′ is set as the reference, and the video is displayed in that state. Is displayed. Then, the microcomputer 16 starts a timer.

When the predetermined time has elapsed, the process proceeds to step S25, and as shown in step S25, the variable blank Δ is added to the vertical blanking start position which is a reference at the time of underscan, and the variable step Δ is subtracted to the end position in the state a. To do.
In this state a, for example, when a normal display switch operation or the like is performed, the underscan is canceled as shown in step S26. That is, an image is displayed in the vertical blanking period during normal display. In this case, information on the current addition / subtraction state a is further stored in the internal memory of the microcomputer 16 as, for example, the last state. In this case, the timer time measurement is also stopped.
When the normal display switch operation is canceled or the underscan display operation is performed, underscan is set (selected) again as shown in step S27. In this case, the video is displayed in the state a. Also, the time measurement operation by the timer is resumed.

When a predetermined time elapses by the timer in the display state of state a, as shown in step S28, the microcomputer 16 further displays an image in state b after adding Δ at the blanking start position and subtracting Δ at the end position from state a. indicate.
When a predetermined time has elapsed from this state b, the microcomputer 16 determines whether or not the vertical blanking start / end position in this state exceeds the limit value, as shown in step S29. If this determination result does not exceed the limit value, the process returns to step S25 or S26, and is repeated until the limit value is reached as described in step S30.
By performing the processing from step S25 to S30 in this way, the display area from the lower end of the enlarged display area Da to the upper end of the display area Db slowly changes upward due to the change in the vertical blanking start / end position, Effectively prevents the occurrence of brightness differences.

On the other hand, if it is determined in step S29 that the limit value is exceeded, in step S31, processing is performed so as not to exceed the limit value, and then processing in steps S25 to S30 is performed in the reverse direction.
First, in step S31, an image is displayed in a state c in which the variable step Δ is subtracted from the vertical blanking start position in the previous state b and Δ is added to the end position. In this state c, the timer is started. In this state c, for example, when a normal display switch operation or the like is performed, the underscan is canceled as shown in step S32. That is, an image is displayed in the vertical blanking period during normal display. In this case, information on the current subtraction state c is further stored in the internal memory of the microcomputer 16 as, for example, a last state. In this case, the timer time measurement is also stopped.

When the normal display switch operation is canceled or the underscan display operation is performed, underscan is set (selected) again as shown in step S33. In this case, the video is displayed in the state c. Also, the time measurement operation by the timer is resumed.
Then, when a predetermined time elapses by the timer in the display state of state c, the microcomputer 16 displays the video image in a state d in which Δ is further subtracted from the state c to the blanking start position and Δ is added to the end position as shown in step S34. .
When a predetermined time elapses from this state d, the microcomputer 16 determines whether or not the vertical blanking start / end position in this state exceeds the limit value as shown in step S35. If this determination result does not exceed the limit value, the process returns to step S31 or S32 and is repeated until the limit value is reached as described in step S36.

On the other hand, if it is determined in step S35 that the limit value is exceeded, in step S37, the video is displayed with a variable step Δ addition at the vertical blanking start position in state d and Δ subtraction at the end position so as not to exceed the limit value. Is displayed. Thereafter, the process returns to step S25 or step S26 to perform the above-described processing.
By performing such processing, as in the case of the processing of FIG. 4, the vertical blanking start / end position is slowly and repeatedly performed in a long cycle, so that even if the underscan operation is continued for a long time, the fluorescence Since the boundary between the video display and non-display on the screen changes, it is possible to effectively prevent the occurrence of a luminance step on the phosphor screen.
As described above, according to the present embodiment, it is possible to effectively prevent the occurrence of a luminance step on the phosphor screen with a simple configuration or a simple method. Further, in this case, it is possible to prevent a part of the video from being displayed unnaturally in the middle of the upper and lower ends of the video, and to maintain a high quality state.

FIG. 4 or FIG. 5 shows a typical case of changing the vertical blanking start and end positions in synchronization (interlocking) with each other, and it is not always necessary to synchronize or interlock with each other. , It should be repeated.
In the above description, the microcomputer 16 is controlled to change the vertical blanking start and end positions in the color demodulation circuit 5, but may be performed in other circuit portions.
For example, as shown by a dotted line in FIG. 1, a pulse (generated by counting output of the horizontal synchronizing signal HD) from the microcomputer 16 is applied to, for example, a transistor that constitutes the CRT drive circuit 14 and generates a vertical blanking signal. Even if the start and end positions of the vertical blanking period are changed, the same effect is obtained.
Further, in addition to the CRT drive circuit 14, it may be performed in the double speed processing circuit 6, or may be performed in the primary color output circuit 7.

Further, the vertical blanking start position and end position are switched at the time of underscan operation with respect to the aspect ratio of the fluorescent screen of the picture tube. In this case, not only the main / sub power supply OFF / ON but also the picture receiver. Control may be performed by switching the input and the display time.
In the above-described embodiment, the case of the receiver 1 including the tuner 2 and the like has been described. However, the present invention is not limited to this, and can be widely applied to display devices using a picture tube. . In the above description, the case of underscan that narrows the display area in the vertical direction is described. However, the vertical blanking start / end position (or vertical blanking period) is also used when the display area is narrowed in the horizontal direction. Is replaced with the horizontal blanking start / end position (or horizontal blanking period).

  The present invention can be used as a display device in an electronic apparatus such as a television receiver or a personal computer.

1 is a block diagram showing the overall configuration of a television receiver according to a first embodiment of the present invention. FIG. 4 is an operation explanatory diagram showing one of three primary color signals to which a vertical synchronization signal is added and a vertical deflection signal in that case. Explanatory drawing of the operation | movement of the video display by a picture tube (color CRT) at the time of underscan in a present Example. The flowchart which shows the processing content which prevents generation | occurrence | production of a brightness | luminance level | step difference by changing the vertical blanking period by a long period by a present Example. The flowchart which shows the processing content in the modification of FIG. The block diagram which shows the circuit peripheral part which prevents the brightness | luminance level | step difference in the receiver of a prior art example. Explanatory drawing of the operation | movement which displays the image | video at the time of underscan in the prior art example of FIG.

Explanation of symbols

1. Color television receiver (receiver)
DESCRIPTION OF SYMBOLS 2 ... Tuner 3 ... Video amplifier circuit 4 ... Synchronization separation circuit 5 ... Color demodulation circuit 6 ... Double speed processing circuit 7 ... Primary color output circuit 8 ... Horizontal deflection circuit 9 ... Vertical deflection circuit 11 ... Color cathode ray tube (color CRT)
DESCRIPTION OF SYMBOLS 12 ... Deflection yoke 13 ... Primary color output circuit 14 ... CRT drive circuit 16 ... Microcomputer (microcomputer)
Da ... Enlarged display area Db ... Existing display area Agent Patent attorney Susumu Ito

Claims (5)

Display area setting means for enlarging the display area of the video signal in the vertical direction at the time of underscan operation with respect to the aspect ratio of the phosphor screen of the picture tube;
Vertical blanking position changing means for repeatedly changing the vertical blanking start position and the vertical blanking end position in a long time in the state of the display area enlarged in the vertical direction by the display area setting means;
A display device using a picture tube, comprising:   2. The vertical blanking position changing means changes the vertical blanking start position and the vertical blanking end position in a substantially synchronized manner within a range enlarged in the vertical direction in the display area. A display device using the picture tube described in 1.   The vertical blanking position changing means increases or decreases the display area by substantially synchronizing the vertical blanking start position and the vertical blanking end position within a range expanded in the vertical direction in the display area. The display device using a picture tube according to claim 1, wherein the display device is changed as follows.   The vertical blanking position changing means moves the display area in the vertical direction by substantially synchronizing the vertical blanking start position and the vertical blanking end position within a range expanded in the vertical direction in the display area. The display device using a picture tube according to claim 1, wherein the display device is changed so as to be changed.   The vertical blanking position changing means changes the vertical blanking start position and the vertical blanking end position in steps of a natural number times a horizontal line within a range expanded in the vertical direction in the display area. A display device using the picture tube according to claim 1.

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