JP2000347644A - On-screen display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an on-screen display device capable of providing stable on-screen display irrespective of strength of a received electric wave. SOLUTION: A synchronization signal detected at a receiving part 30 is supplied to a PLL 31 and a signal having frequency equal to frequency of the synchronization signal is generated. Dot clock frequency stored in a ROM 34 is selected on the basis of the signal and a dot clock(DC) is generated at a dot clock generator 35. On the basis of the DC, a timing for providing on-screen display is determined at a timing generator 36 and a pattern picture signal generated at a pattern generator 37 is supplied to a display 33 through a switch 32.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an on-screen display device, and more particularly to an on-screen display device capable of performing stable on-screen display regardless of the intensity of a received radio wave.

[0002]

2. Description of the Related Art In some cases, a display is mounted on an automobile and used for displaying navigation information and television broadcast. Further, in order to simplify the operation of the navigation system and the television receiver, it is also common to superimpose the operation buttons of these devices on the television broadcast receiver to display them on-screen and to operate them using a touch screen. Is being done.

FIG. 1 is an example of a display screen in which an English character "F" is displayed on a television screen on an on-screen display, and FIG. 2 is a basic configuration diagram of a conventional on-screen display device. That is, the on-screen display device includes a pattern generator 21 for generating an on-screen pattern, a television receiver 22 for receiving a television wave and generating a video signal, and a horizontal synchronization signal detected by the television receiver 22. A dot clock generator 23 that generates a dot clock based on the timing, a timing generator 24 that counts dot clocks generated by the dot clock generator 23 and determines a display position of a pattern, and outputs from the pattern generator 21 under the control of the timing generator 24 A switch 25 for switching between a pattern signal to be output and a video signal output from the television receiver 22, and a display 26 for display.

Display of an image on the display 26 is performed by repeating horizontal scanning from left to right of the display 26 from top to bottom, for example, 525 times, so that the upper left end is located at the coordinates (i, j). When the "j" -th dot pulse of the "i" -th scanning line is detected to display the English character "F", the switch 25 is operated to change the pattern generated from the pattern generator 21 to "j + m". It is sent to the display 26 until the dot pulse is detected.

Conventionally, a PLL (Phase Lock) has been used as a dot clock generator as an on-screen display device.
(ed. Loop), a dot clock supplied thereto is counted by a timing generator, and a horizontal synchronizing signal is used to set / reset the timing generator (see Japanese Patent Application Laid-Open No. Hei 6-113223).

[0006]

However, in the on-screen display device having the above-described structure, the intensity of the radio wave received by the television receiver 22 fluctuates with the movement of the automobile. In some cases, the synchronization signal cannot be detected. If the synchronization signal cannot be detected, the set / reset of the timing generator is not performed normally, so that the display position of the pattern cannot be prevented from deviating.

The present invention has been made in view of the above problems, and has as its object to provide an on-screen display device capable of performing stable on-screen display regardless of the intensity of a received radio wave.

[0008]

According to a first aspect of the present invention, there is provided an on-screen display device comprising: a receiving section for receiving a television broadcast wave; and a PLL for generating a signal having the same frequency as a synchronization signal detected by the receiving section. , A storage / selection unit for selecting a dot clock frequency corresponding to the frequency output from the PLL from a plurality of dot clock frequencies stored in advance, and a dot clock having a dot clock frequency set by the storage / selection unit A dot clock generator that transmits a dot clock, a timing generator that determines the display position of a previously stored pattern in a television screen based on the dot clock transmitted by the dot clock generator, and a dot clock that is transmitted by the dot clock generator. A video signal of a pattern stored in advance based on the A pattern generator, a television image signal generated by the image receiving unit or a display for displaying the pattern image signal generated by the pattern generator, and a timing generator that is generated by the image receiving unit when it is determined that the display position is not the display position. A switch for supplying a television image signal to the display and supplying a pattern image signal generated by the pattern generator to the display when the timing position is determined by the timing generator to be the display position.

In the present invention, the dot clock frequency stored in the storage / selection section is selected based on a signal having the same frequency as the frequency of the synchronization signal by the PLL, and a dot clock having this dot clock frequency is generated. Therefore, the generation of the dot clock is continued even when the synchronization signal is not detected in the image receiving unit. An on-screen display device according to a second aspect of the present invention includes a receiving unit that receives a television broadcast wave, a PLL that generates a signal having the same frequency as a synchronization signal detected by the receiving unit, and a frequency that is output from the PLL. A multiplying unit for generating a dot clock by multiplying by a predetermined multiple, a timing generator for determining a display position of a previously stored pattern on a television screen based on the dot clock generated by the multiplying unit, and a dot clock A pattern generator that generates a video signal of a pattern stored in advance based on a dot clock transmitted by the generator, and a display that displays a television video signal generated by the image receiving unit or a pattern video signal generated by the pattern generator. , The timing generator has determined that it is not a display position The television video signal generated by the image receiving unit comprises a switch and is supplied to the display a pattern image signal generated by the pattern generator when it is determined to be displayed position is supplied to the display timing generator.

According to the present invention, since a signal having the same frequency as the frequency of the synchronization signal is generated by the PLL and the dot clock is generated by multiplying the signal, a synchronization signal is not detected in the image receiving unit. Also, the generation of the dot clock is continued.

[0011]

FIG. 3 is a block diagram of a first embodiment of the on-screen display device according to the present invention, in which a synchronization signal S generated by a receiving unit 30 is transmitted to a PLL 31 and a receiving unit 30 is output. Is generated through the switch 32 and is guided to the display 33. The PLL 31 detects the synchronization frequency F of the synchronization signal S and stores the synchronization frequency F in the ROM (Re
ad Only Memory) 34. ROM3
4, the dot clock frequency D to be output corresponding to the plurality of synchronization frequencies F supplied to the address is stored in advance, and the dot clock frequency corresponding to the synchronization frequency F detected by the PLL 31 this time is read from the ROM 34. D is output.

The dot clock generator 35 is a variable frequency pulse generator, and outputs a dot clock C having a frequency corresponding to the dot clock frequency D output from the ROM 34. The dot clock C is applied to the timing generator 36 and the pattern generator 37. The timing generator 36 counts the dot clock, operates the switch 32 by the timing signal T at the display position of the pattern, and supplies a signal supplied to the display 33. From the video signal V to the pattern signal P output from the pattern generator 37.

A bit pattern of a pattern to be displayed on the screen is stored in the pattern generator in advance. When the pattern display timing is reached, the bit patterns stored in advance are sequentially read out in synchronization with the dot clock. It is supplied to the display 33 via the switch 32. In the first embodiment, RO
Since the frequency of the dot clock is set by M34, even if the reception state is deteriorated and the synchronization signal is not detected in the image receiving unit 30, the deviation of the display position of the pattern is prevented.

FIG. 4 is a block diagram of a second embodiment of the on-screen display device according to the present invention. The same components as those in the first embodiment of FIG. 3 are denoted by the same reference numerals. In the second embodiment, the ROM 34 of the first embodiment is used.
A multiplying circuit 40 is used in place of the dot clock generator 35. The multiplying circuit 40 sets a predetermined number (for example, 4) between adjacent synchronization pulses output from the PLL 31.
00) The dot clock is multiplied to generate a dot clock, and the timing generator 36 and the pattern generator 37 are controlled based on the dot clock.

In the second embodiment, even when the PLL 31 cannot receive the synchronization signal from the image receiving unit 30, the PLL 31 uses the flywheel effect of the PLL to continue the transmission at the previous frequency, thereby providing the multiplication circuit 40 with the multiplication circuit 40. The supply of the signal is continued. FIG. 5 is a configuration diagram of a third embodiment of the on-screen display device according to the present invention.
The same components as those of the first embodiment are denoted by the same reference numerals.

That is, in the first and second embodiments, the dot clock frequency is maintained constant between adjacent synchronization signals. However, the aspect ratio of the in-vehicle display is 9: 1.
6, the aspect ratio is 3: 4.
In order to display this image, not only must the video signal be appropriately compressed and expanded, but also the dot clock for on-screen display needs to be expanded and compressed.

In the third embodiment, a companding section 40 is provided between the ROM 34 and the dot clock generator 35 in order to perform companding processing also on the dot clock.
The companding processing unit 50 is constituted by, for example, a microprocessor and controls the frequency of the dot clock according to the display position on the display. 6A and 6B are diagrams for explaining the necessity of the companding process. FIG. 6A shows an image displayed on a display having an aspect ratio of 3: 4, and FIG. 6B shows an image displayed on a display having an aspect ratio of 9:16. Shows the image when displayed.

That is, when an image having an aspect ratio of 3: 4 is displayed on a display having an aspect ratio of 9:16, for example, decompression processing is performed at both left and right ends (regions I and III), and at the center (region II). It is necessary to display an unprocessed image. FIG. 7 is a flowchart of a companding processing routine executed by the compensating processing unit 40 in the above case,
For example, it is executed every time the frequency F is output from the ROM 34.

That is, in step 70, the dot clock is read, and in step 71, the index j indicating the display position is incremented. In step 72, the display area is determined based on the index j. If it is determined in step 72 that the right and left ends (regions I and III) are present, a predetermined correction value ΔF is added to the frequency F output from the ROM 34 in step 73 to correct the frequency F.

If it is determined in step 72 that the center is located at the center (region II), the frequency F output from the ROM 34 is set as it is in step 74. Finally, in step 75, the frequency F is output to the dot clock generator 35, and this routine ends. In addition,
As compared with the second embodiment, a companding unit 50 may be inserted between the PLL 31 and the multiplying circuit 40, and the transmission frequency of the multiplying circuit 40 may be controlled by the companding unit 50.

FIG. 8 is a block diagram of a fourth embodiment of the on-screen display device according to the present invention. The same components as those in the first embodiment of FIG. 3 are denoted by the same reference numerals. That is, the fourth embodiment differs from the first embodiment in that the electric field intensity determination unit 80 that determines the electric field intensity output from the image receiving unit 30 does not display a television image on the display 33, A graphic mode dot clock generator 81 for generating a dot clock in the graphic mode for displaying only the image data, and a dot clock switch 82 for switching the supply source of the dot clock applied to the timing generator 36 and the pattern generator 37 are additionally provided.

When the electric field strength is larger than a predetermined threshold value, it is determined that the pattern can be displayed on-screen in the television image. Is set in the dot clock generator 35. When the electric field strength is smaller than the predetermined threshold, the television image is displayed, and it is determined that the synchronization signal cannot be detected. Set to generator 81.

That is, in the fourth embodiment, when the electric field is weak, the display of the television image is stopped, and only the pattern is displayed. In addition, also with respect to the second embodiment,
Electric field strength determination unit 80, graphic mode dot clock generator 81, and dot clock switch 8
2, when the electric field strength is smaller than a predetermined threshold, it is possible to stop displaying the television image and display the pattern in the graphic mode.

[0024]

According to the on-screen display device of the present invention, it is possible to generate a dot clock even when the electric field intensity of the television broadcast wave is reduced and a synchronization signal is not detected. It is possible to prevent the display position from shifting.

Further, even when an image having a certain aspect ratio is displayed on a display having a different aspect ratio, it is possible to prevent deviation of the on-screen display position. Further, when the electric field strength decreases, the display of the television screen is stopped, and the pattern can be displayed in the graphic mode.

[Brief description of the drawings]

FIG. 1 is a display example of an on-screen display.

FIG. 2 is a basic configuration diagram of a conventional on-screen display device.

FIG. 3 is a configuration diagram of an on-screen display device according to a first embodiment of the present invention.

FIG. 4 is a configuration diagram of an on-screen display device according to a second embodiment of the present invention.

FIG. 5 is a configuration diagram of a third embodiment of the on-screen display device according to the present invention.

FIG. 6 is a diagram illustrating the necessity of a companding process.

FIG. 7 is a flowchart of a companding processing routine.

FIG. 8 is a configuration diagram of a third embodiment of the on-screen display device according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 30 image receiving unit 31 PLL 32 switch 33 display 34 ROM 35 dot clock generator 36 timing generator 37 pattern generator 40 multiplier circuit 50 companding processing unit 80 electric field strength determination unit 81 graphic dot clock Generator 82: dot clock switch

Claims (6)

[Claims] 1. A receiver for receiving a television broadcast wave, a PLL for generating a signal having the same frequency as a synchronization signal detected by the receiver, and a dot clock frequency corresponding to a frequency output from the PLL. A storage / selection unit that selects from a plurality of dot clock frequencies stored in advance; a dot clock generator that transmits a dot clock having a dot clock frequency set by the storage / selection unit; A timing generator that determines a display position of a pre-stored pattern in a television screen based on a dot clock transmitted by the video signal generator; and a video signal of a pattern stored in advance based on the dot clock transmitted by the dot clock generator. And a pattern generator that generates A television image signal generated by the image receiving unit, or a display that displays a pattern image signal generated by the pattern generator; and a display generated by the image receiving unit when the timing generator determines that the display position is not a display position. A switch for supplying a television video signal to the display, and supplying a pattern video signal generated by the pattern generator to the display when the timing position is determined to be the display position. Display device. 2. A dot clock frequency output from the storage / selection unit, which is provided between the storage / selection unit and the dot clock generator, and corrected according to the number of dot clocks transmitted from the dot clock generator. 2. The on-screen display device according to claim 1, further comprising a compander for setting the corrected dot clock frequency to the dot clock generator. 3. An electric field intensity judging unit for judging that an electric field intensity of a television broadcast wave received by the image receiving unit is equal to or more than a predetermined threshold value, and a graphic mode operation for displaying only a pattern on the display. A graphic mode dot clock generator that generates a dot clock; and a timing generator that generates a dot clock generated by the dot clock generator when the electric field intensity is determined by the electric field intensity determination unit to be equal to or greater than a predetermined threshold. And to the pattern generator,
A dot clock switch that supplies a dot clock generated by the graphic dot clock generator to the timing generator and the pattern generator when the electric field intensity determination unit determines that the electric field intensity is equal to or less than a predetermined threshold. The on-screen display device according to claim 1, further comprising: 4. A receiver for receiving a television broadcast wave, a PLL for generating a signal having the same frequency as a synchronization signal detected by the receiver, and a frequency output from the PLL by a predetermined multiple. A multiplying unit for multiplying to generate a dot clock; a timing generator for determining a display position of a pre-stored pattern on a television screen based on the dot clock generated by the multiplying unit; A pattern generator that generates a video signal of a pattern stored in advance based on a dot clock that is generated, a television video signal generated by the image receiving unit, or a display that displays a pattern video signal generated by the pattern generator Is determined not to be the display position by the timing generator. Supply the television image signal generated by the image receiving section to the display when the image is received, and display the pattern image signal generated by the pattern generator to the display when the timing generator determines the display position. An on-screen display device comprising: a supply switch. 5. A transmission frequency of the multiplying unit, which is provided between the PLL and the multiplying unit and is determined based on an output of the PLL, is corrected according to the number of dot clocks transmitted from the dot clock generator. 5. The on-screen display device according to claim 4, further comprising a compander for supplying the corrected dot clock frequency to the timing generator and the pattern generator. 6. An electric field intensity judging unit for judging that an electric field intensity of a television broadcast wave received by the image receiving unit is equal to or more than a predetermined threshold value, and in a graphic mode operation for displaying only a pattern on the display. A graphic mode dot clock generator that generates a dot clock; and the timing generator generates the dot clock generated by the multiplying unit when the electric field intensity is determined by the electric field intensity determination unit to be equal to or greater than a predetermined threshold. The pattern generator supplies the dot clock generated by the graphic dot clock generator to the timing generator and the pattern generator when the electric field intensity is determined by the electric field intensity determination unit to be equal to or less than a predetermined threshold. Dotk to supply On-screen display device according to claim 4 or 5 further comprising a Kkusuitchi.