Display device with a display mode identification function and a display mode identification method

• US 6,046,737 A
• Filed: 07/31/1996
• Issued: 04/04/2000
• Est. Priority Date: 02/14/1996
• Status: Expired due to Fees

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Nakamura, Masanori
• Primary Examiner(s): NGUYEN, CHANH DUY
• Application Number:
  US08/690,072
• Time in Patent Office: 1,343 Days
• Field of Search: 345/213, 345/204, 345/1, 345/3, 345/132, 345/211, 345/212, 345/214, 345/148, 345/150, 348/511, 348/536, 348/554, 348/588, 348/476, 348/473
• US Class Current: 345/213
• CPC Class Codes: G09G 2320/08 Arrangements within a display terminal for setting, manually or automatically, display parameters of the display terminal
• CPC Class Codes: G09G 3/2092 Details of a display terminals using a flat panel, the details relating to the control arrangement of the display terminal and to the interfaces thereto suitable for both CRT and flat panel G09G5/003; specific for a CRT G09G1/165
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers
• CPC Class Codes: G09G 5/005 Adapting incoming signals to the display format of the display terminal
• CPC Class Codes: G09G 5/006 Details of the interface to the display terminal specific for a display terminal using a CRT G09G1/167; using a flat panel G09G3/2096; circuits for interfacing with colour displays G09G5/04
• CPC Class Codes: G09G 5/008 Clock recovery
• CPC Class Codes: G09G 5/18 Timing circuits for raster scan displays specially adapted for television H04N ; synchronisation between the display unit and other display units, videodisc player G09G5/12

Abstract

The present invention relates to a display device and a method for identifying a display mode for a display device which receives a synchronous signal and a video signal. The display device measures a frequency or cycle of the synchronous signal, compares the measured frequency or cycle of the synchronous signal with a reference frequency or cycle to identify the display mode, and changes the reference frequency or cycle including a first and second reference value selectively for the step of comparing. According to the present invention, the display mode is stably identified.

Claims

1. A display device, having a display screen, which receives display signals including at least a synchronous signal and a video signal transmitted at predetermined times relative to the synchronous signals and displays the video on the display screen, the display device comprising:

an identification section for measuring a frequency or a cycle of the synchronous signal and for comparing the frequency or the cycle with predetermined first and second reference frequencies or cycles to identify a display mode which specifies the predetermined timing from a plurality of display modes with predetermined settings, said predetermined reference frequency or cycle defining a dividing point among the range of frequencies or cycles from one display mode to another display mode of said plurality of display modes so that when said measuring frequency or cycle is identified as being greater than or less than said first or second reference frequency or cycle, said one or said another display mode is identified as the correct display mode to provide a stable display, said second reference frequency or cycle being set by controlling the identification section to selectively change the reference frequency or cycle from said first reference frequency or cycle to said second reference frequency or cycle within the range between the display modes when said first reference frequency or cycle results in unstable display.

2. A display device according to the claim 1, further comprising:

a dot clock generation circuit for generating a dot clock signal having a frequency in accordance with the display mode detected by the identification section; and

a display controller for displaying a video signal through sampling the video signal based on the dot clock signal with a predetermined timing from said synchronous signal.

3. A display device according to the claim 1, wherein;

said identification section stores a first reference frequency or cycle between the frequency or cycle of the synchronous signals corresponding to the plural display modes and a second reference frequency or cycle of a frequency which is higher or lower than the first frequency, and the first and second reference frequencies or cycles are selectively switched.

4. A display device according to the claim 3, wherein:

said identification section selects the second reference for detecting the display mode when the frequency or cycle of the supplied synchronous signal is in a nearby region of the first reference.

5. The method according to claim 3, wherein said identification section stores a third reference frequency or cycle so that said first, second and third reference frequencies or cycles are selectively switched.

6. A display device according to one of the claims 1-4,

said synchronous signal includes a horizontal synchronous signal or a vertical synchronous signal.

7. The display device according to claim 1, further comprising a switch so that a user can control said identification device to select the reference frequency or cycle upon detecting an unstable display.

8. The display device according to claim 1, further comprising a reference switching signal generator for automatically controlling said identification section to switch the reference frequency when use of said reference frequency or cycle is likely to cause unstable display.

9. The display device according to claim 8, wherein said reference switching signal generator receives a count value for said measured frequency and compares said count value to predetermined count values to determined if said reference frequency or cycle will cause unstable display.

10. A method of identifying a display mode of supplied display signals, comprising, the steps of:

measuring a frequency or cycle of a supplied synchronous signal,

identifying the display mode for said supplied synchronous signal from a plurality of display modes with predetermined settings including a step of comparing said frequency or cycle to a first reference frequency or cycle set between said display modes;

comparing the frequency or cycle of the supplied synchronous signal with a predetermined second reference frequency or cycle that is different from said first reference frequency or cycle, said first and second reference frequencies and cycles being between the same two frequencies or cycles of two said display modes when detecting that the display is unstable, said unstable display indicating that said first reference frequency or cycle has a value too close to the value of said frequency or cycle of said supplied synchronous signal, said second predetermined reference frequency or cycle defining a dividing point so that when said frequency or cycle of said supplied synchronous signal is found to be greater than or less than said second predetermined reference frequency or cycle, one of said two display modes is chosen as the correct display mode for stable display.

11. The method according to claim 10, wherein said first reference frequency or cycle is set at a midpoint value between two cycles of each pair of adjacent display modes of said plurality of display modes, and said second reference frequency or cycle is set outside of said midpoint value and within said range of frequencies or cycles between each said pair of adjacent display modes.

12. A method of identifying a display mode with predetermined settings of supplied display signals including a supplied synchronous signal and video signal, comprising:

measuring a frequency or cycle of the supplied synchronous signal;

comparing the frequency or cycle of the supplied synchronous signal with one reference frequency or cycle which is a middle value between adjacent display modes; and

comparing the frequency or cycle of the supplied synchronous signal with another reference frequency or cycle, which is different from the one reference frequency or cycle, to stably identify the display mode when a display mode is identified unstably when comparing the frequency or cycle of the supplied synchronous signal with said one reference frequency or cycle,

said another frequency or cycle defining a dividing point in a range of frequencies or cycles defined from one said adjacent display mode to another said adjacent display mode so that when said frequency or cycle of the supplied synchronous signal is greater than or less than said another frequency or cycle, one of said adjacent display modes is chosen as the correct display mode for stable display.

13. A method for identifying a display mode with predetermined settings for a display device which received a synchronous signal and a video signal, comprising steps of:

measuring a frequency or cycle of the synchronous signal;

comparing the measured frequency or cycle of the synchronous signal with a first reference frequency or cycle to identify the display mode from a plurality of display modes; and

changing the reference frequency or cycle including selecting one of a plurality of predetermined reference values to be used for the step of comparing when said first reference frequency or cycle results in unstable display, wherein said plurality of predetermined reference values are different from each other and are set in the range between the frequencies or cycles of two adjacent display modes of the plurality of display modes, said first reference frequency or cycle being set between said frequencies or cycles of said two adjacent display modes, said selected reference frequency or cycle defining a dividing point on the range of frequencies or cycles defined from one said adjacent display mode to another said adjacent display mode so that when said measured frequency or cycle is found to be greater than or less than said selected reference frequency or cycle, one of said adjacent display modes is chosen as the display mode for stable display.