Display apparatus with circuit expanding horizontal retrace interval of horizontal deflection current

• US 6,262,779 B1
• Filed: 02/10/1999
• Issued: 07/17/2001
• Est. Priority Date: 02/10/1998
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Kaizaki, Kazuhiro, Motoshima, Junji, Nakajima, Mitsuo, Sugiyama, Masato, Onozawa, Makoto, Nishinaka, Yuzo
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): NATNAEL, PAULOS M
• Application Number:
  US09/248,001
• Time in Patent Office: 888 Days
• Field of Search: 348/556, 348/557, 348/561, 348/445, 348/913, 348/634, 348/635, 348/637, 348/704, 348/739, 315/364
• US Class Current: 348/704
• CPC Class Codes: H04N 3/223 Controlling dimensions by maintaining the cathode-ray tube high voltage constant H04N3/185
• CPC Class Codes: H04N 3/24 Blanking circuits
• CPC Class Codes: H04N 7/0122 the input and the output signals having different aspect ratios
• CPC Class Codes: Y10S 348/913 Letterbox, e.g. display 16:9 aspect ratio image on 4:3 screen

Abstract

A display apparatus for a television or computer terminal having a cathode ray tube with a deflection coil. The display apparatus includes a signal processing circuit which compresses a display period in a horizontal scanning period of an input video signal and which expands a blanking interval of the horizontal scanning period of the video signal, the signal processing circuit providing an output of the video signal to the cathode ray tube, and a horizontal retrace interval expansion circuit which expands a horizontal retrace line interval of a horizontal deflection current for the deflection coil of the cathode ray tube in accordance with the blanking period expanded by the signal processing circuit. The cathode ray tube displays the input video signal in accordance with the output of the signal processing circuit and the output of the horizontal retrace interval expansion circuit.

Claims

1. A display apparatus comprising:

signal processing means for compressing a display period in a horizontal scanning period of an input video signal and for expanding a blanking period of the horizontal scanning period of the input video signal and provides an output thereof; and

horizontal retrace interval expansion means for expanding a horizontal retrace interval of a horizontal deflection current for a display device in accordance with the expanded blanking period expanded by the signal processing means;

wherein a display device displays the video signal in accordance with an output of the signal processing means and the horizontal retrace interval expansion means.

2. A display apparatus according to claim 1, wherein the horizontal retrace interval expansion means includes a horizontal deflection current output means for outputting a horizontal deflection current having a horizontal retrace line interval which is larger than a horizontal retrace line interval for the inputted video signal in accordance with the expanded blanking period expanded by the signal processing means, the display device displaying the video signal in accordance with the output of the signal processing means and the horizontal deflection current output means.

3. A display apparatus according to claim 2, wherein a ratio of the horizontal retrace line interval to a horizontal period of the displayed video signal is at least 20%.

4. A display apparatus according to claim 3, wherein the ratio of the horizontal retrace line interval to the horizontal period is in a range of 20% to 30%.

5. A display apparatus comprising:

a cathode ray tube having a deflection coil;

a signal processing circuit which compresses a display period in a horizontal scanning period of an input video signal and which expands a blanking interval of the horizontal scanning period of the video signal, the signal processing circuit providing an output of the video signal to the cathode ray tube; and

a horizontal retrace interval expansion circuit which expands a horizontal retrace line interval of a horizontal deflection current for the deflection coil of the cathode ray tube in accordance with the blanking period expanded by the signal processing circuit;

wherein the cathode ray tube displays the input video signal in accordance with the output of the signal processing circuit and the output of the horizontal retrace interval expansion circuit.

6. A display apparatus according to claim 5, wherein the horizontal retrace interval expansion circuit includes a horizontal deflection current output circuit connected to a horizontal deflection coil of the cathode ray tube, the horizontal deflection current output circuit outputting a horizontal deflection current having a horizontal retrace line interval which is larger than a horizontal retrace line interval for the inputted video signal in accordance with the expanded blanking period expanded by the signal processing circuit.

7. A display apparatus according to claim 6, wherein a ratio of the horizontal retrace line interval to a horizontal period of the displayed video signal is at least 20%.

8. A display apparatus according to claim 7, wherein the ratio of the horizontal retrace line interval to the horizontal period is i n a range of 20% to 30%.

9. A display apparatus according to claim 6, wherein the display apparatus is a television, and the signal processing circuit includes a memory for storing the inputted video signal, a conversion circuit which writes the video signal into the memory at a first write-in frequency and which reads out the video signal stored in the memory at a second read-out frequency different from the write-in frequency and which increases the read-out frequency in accordance with the extension of the blanking interval.

10. A display apparatus according to claim 9, wherein when a blanking ratio before extending the blanking interval of the video signal is α

, and a rate of extension of the blanking interval is n, the read-out frequency of the conversion circuit is increased to about (1−

α

)/(1−

nα

) times the write-in frequency.

11. A display apparatus according to claim 6, wherein the display apparatus is a wide aspect television and the cathode ray tube is a wide aspect cathode ray tube, the signal processing circuit including an I/P conversion circuit for converting a standard aspect inputted video signal of an interlaced scanning system into a video signal of a progressive scanning system, a wide conversion circuit for converting an aspect ratio of the video signal converted to the progressive scanning system into a wide aspect ratio, and further comprising a system controller for controlling the horizontal retrace interval expansion circuit so as to extend the horizontal retrace line interval.

12. A display apparatus according to claim 6, wherein the display apparatus is a wide aspect television and the cathode ray tube is a wide aspect cathode ray tube, the signal processing circuit receiving an inputted video signal of one of a standard aspect television signal, a wide aspect television signal and a standard aspect PC signal, the signal processing circuit including a conversion circuit for converting the aspect ratio of one of a standard aspect video signal and a standard aspect PC signal into a wide aspect ratio signal, and further comprising a system controller for controlling the horizontal retrace interval expansion circuit to extend the horizontal retrace interval.

13. A display apparatus according to claim 12, wherein the horizontal period expansion circuit includes a deflection control circuit for the horizontal deflection current output circuit for extending the horizontal retrace line interval by extending the horizontal blanking interval of the video signal, the signal processing circuit including a memory for storing a wide aspect signal, the conversion circuit enabling writing-in of the video signal into the memory at a write-in frequency and reading-out of the stored video signal from the memory at a read-out frequency different from the write-in frequency, wherein the read-out frequency is increased in accordance with the extension of the horizontal blanking interval.

14. A display apparatus according to claim 6, further comprising a video circuit responsive to the signal processing circuit for driving a cathode electrode of the cathode ray tube, and a vertical deflection circuit for driving a vertical deflecting coil of the cathode ray tube.

15. A display apparatus according to claim 14, wherein a ratio of the horizontal retrace line interval to a horizontal period of the displayed video signal is at least 20%.

16. A display apparatus according to claim 14, wherein the ratio of the horizontal retrace line interval to the horizontal period is in a range of 20% to 30%.

17. A display apparatus according to claim 14, wherein a horizontal frequency of the signal outputted from the signal processing circuit is set to be about 31.5 kHz, and the horizontal retrace line interval in the horizontal deflection circuit is set to be at least 6.3 μ

s.

18. A display apparatus according to claim 14, wherein a horizontal frequency of the signal outputted from the signal processing circuit is set to be about 33.75 kHz, and the horizontal retrace line interval in the horizontal deflection circuit is set to be at least 5.9 μ

s.

19. A display apparatus according to claim 14, wherein a power supply voltage of the video circuit for driving the cathode electrode of the cathode ray tube is substantially equal to a power supply voltage of the horizontal deflection output circuit of the horizontal blanking period expansion circuit.

20. A display apparatus according to claim 14, wherein the signal processing circuit includes a time axis conversion circuit for changing a ratio of the horizontal display interval to the horizontal period of the input video signal.

21. A display apparatus according to claim 14, wherein the signal processing circuit includes an I/P conversion circuit for converting a video signal of an interlaced scanning system into a video signal of a progressive scanning system, and a time axis conversion circuit for changing a ratio of the horizontal display interval to the horizontal period of the I/P-converted video signal.

22. A display apparatus according to claim 14, further comprising a synchronizing pulse separation circuit which separates a synchronizing signal from the output of the signal processing circuit for supply to the horizontal deflection circuit.

23. A display apparatus according to claim 14, wherein power supply voltages of the horizontal deflection circuit and the video circuit are substantially equal.

24. A display apparatus according to claim 14, further comprising a variable power supply circuit for supplying power via a primary winding of a flyback transformer of the horizontal deflection circuit.

25. A display apparatus according to the 24, wherein the output voltage of the variable power supply circuit low varies in accordance with an anode voltage control signal.