Liquid crystal display with back-light control function

Claim 2

A liquid crystal display with a back-light control function, comprising: a liquid crystal panel; display panel driving means for periodically displaying on said liquid crystal display panel by periodically supplying thereto a driving signal; a light source formed on a back surface of said liquid crystal display panel; light source driving means for driving said light source; and dimmer means for dimming with a varying time ratio between a light-on duration and a light-out duration in one lighting period by controlling said light source driving means so as to flash said light source periodically, wherein said dimmer means controls said light source driving means so as to set the lighting frequency for flashing said light source such that m flashes occur, where m is an integer larger than n, and not a multiple of n, in n screen display periods of said liquid crystal panel, where n is an integer larger than 2 and where a screen display period is a period for the liquid crystal display to refresh its content once.

Claim 3

The liquid crystal display with the back-light control function as set forth in claim 1, wherein: said dimmer means controls said light source driving means so as to have a lighting frequency such that said light source flashes odd number of at least three times in 2 screen display periods.

Claim 4

The liquid crystal display with a back-light control function as set forth in claim 1, wherein: said light source is a fluorescent tube, and said light source driving means includes a direct current power supply and an inverter circuit for converting a direct current from said direct current power supply into a high frequency alternate current to be applied to said fluorescent tube.

Claim 5

The liquid crystal display with a back-light control function as set forth in claim 1, further comprising: vertical synchronizing signal generation means for generating a display panel vertical synchronizing signal corresponding to a vertical driving frequency of said liquid crystal display panel by said display panel driving means, wherein said dimmer means includes synchronization means for synchronizing the lighting timing of said light source with a driving timing of said liquid display panel, and controls said light source driving means while synchronizing the lighting timing of said light source with the driving timing of said liquid crystal display panel at every predetermined screens.

Claim 6

The liquid crystal display with a back-light control function as set forth in claim 4, wherein: said synchronization means includes an one-half dividing circuit for dividing a frequency of the display panel vertical synchronizing signal into one-half, and said synchronization mean s synchronizes the lighting timing of said light source with the driving timing of said liquid crystal display panel at every 2-screen period.

Claim 7

The liquid crystal display with a back-light control function as set forth in claim 1, further comprising: horizontal synchronizing signal generating means for generating a display panel horizontal synchronizing signal corresponding to a horizontal driving frequency of said liquid crystal display panel by said display panel driving means, wherein said dimmer means includes dividing means for dividing a frequency of the display panel horizontal synchronizing signal so as to set the lighting frequency of said light source by dividing the frequency of the display panel horizontal synchronizing signal.

Claim 8

The liquid crystal display with a back-light control function as set forth in claim 6 further comprising: image processing means for converting a television image of a NTSC system in which 2 vertical periods correspond to 525 horizontal periods into a suitable format to be processed in said display panel driving means, wherein said dimmer means sets the lighting frequency of the light source such that 5 flashes occur in 2 screen display periods by dividing the frequency of the display panel horizontal synchronizing signal by 105.

Claim 9

The liquid crystal display with a back-light control function as set forth in claim 6 further comprising: image processing means for converting a television image of a PAL system in which 2 vertical periods correspond to 625 horizontal periods into a suitable format to be processed in said display panel driving means, wherein said dimmer means sets the lighting frequency of the light source such that 5 flashes occur in 2 screen display periods by dividing the frequency of the display panel horizontal synchronizing signal by 125.

Claim 10

The liquid crystal display with a back-light control function as set forth in claim 6, further comprising: video processing means for converting the television video signal into a suitable format to be processed in said display panel driving means so as to enable both a television image of the NTSC system in which 2 vertical periods correspond to 525 horizontal periods and a television image of the PAL system in which 2 vertical periods correspond to 625 horizontal periods to be displayed on said liquid crystal display panel, wherein said image processing means includes judging means for determining whether the television video signal is of the NTSC system or of the PAL system so as to output a discrimination signal indicating a result of determination, and said dimmer means switches a dividing ratio of said dividing means based on the discrimination signal, and divides the frequency of the display panel horizontal synchronizing signal by 105 when the discrimination signal is of the NTSC system, while divides the frequency of the display panel horizontal synchronizing signal by 125 if the discrimination signal is of the PAL system so as to set the lighting frequency of said light source such that 5 flashes occur in 2 vertical periods irrespectively of a system of the television video signal.

Claim 11

The liquid crystal display with a back-light control function as set forth in claim 6, further comprising: light-on period set means for setting the light-on period in one lighting frequency of said light source, wherein said dimmer means includes count means for counting a number of pulses of the display panel horizontal synchronizing signal and determines the light-on period set by said light-on period set means based on a count of the number of pulses of the display panel horizontal synchronizing signal.

Claim 12

The liquid crystal display with a back-light control function as set forth in claim 10, wherein when said light-on period set means sets the light-on duration so as to prevent a complete light-on and a complete light-out, said light-on period set means does not set the light-on duration shorter than a lower limit of a light-on duration set beforehand nor longer than a upper limit of the light-on duration set beforehand to limit a minimum light-on duration and a minimum light-out duration in one lightning frequency of said light source.

Claim 13

The liquid crystal display with a back-light control function as set forth in claim 10, wherein: said light-on period set means sets a light-on duration by outputting digital control data corresponding to a number of pulses of the display panel horizontal synchronizing signal to said dimmer means, and said dimmer means alters a count value of said count means for counting a number of flashes of said light source in one lighting period of said light source based on the digital control data.

Claim 14

The liquid crystal display with a back-light control function as set forth in claim 12, wherein said light-on period set means includes detection means for detecting an intensity of incident light from an outside, and said light-on period set means is provided with an automatic correcting function for alternating the control data so as to set the light-on duration longer as the intensity of the incident light from the outside increases.

Claim 15

The liquid crystal display with a back-light control function as set forth in claim 12, wherein said light-on period set means monitors a power source voltage of said light source driving means for driving said light source and is provided with an automatic correcting function for alternating the control data so as to set the light-on duration longer when the power source voltage becomes lower than a predetermined level.

Claim 16

The liquid crystal display with a back-light control function as set forth in claim 12, wherein: said light source is a fluorescent tube, and said light-on period set means includes detection means for detecting a temperature on a surface of the fluorescent tube, and is provided with an automatic adjusting function for alternating the control data according to a detection output from said detection means.

Claim 17

The liquid crystal display with a back-light control function as set forth in claim 12, wherein: said light-on period set means includes detection means for detecting a brightness of said light source and is provided with an automatic adjusting function for alternating the control data based on a detection output from said detection means.

Claim 18

The liquid crystal display with a back-light control function as set forth in claim 1, further comprising: television image processing means for converting a television image into a suitable form to be processed by said display panel driving means; computer graphic image processing means for converting a computer graphic image into a suitable form to be processed in said display panel driving means; and image switching means for switching a video signal to be inputted to said display panel driving means either to a video signal processed in said television video processing means or to a video signal processed by said computer graphic image processing means.

Claim 19

The liquid crystal display with a back-light control function as set forth in claim 1, wherein said liquid crystal display panel includes plural display areas respectively having different display periods so as to enable plural images to be displayed simultaneously, and said display panel driving means controls a display in each display area such that a display frequency of one display area is an integer multiple of a display frequency of another display area.

Claim 20

The liquid crystal display with a back-light control function as set forth in claim 1, further comprising: television image processing means for converting a television image into a suitable form to be processed in said display panel driving means; computer graphic video processing means for converting the computer graphic image into a suitable form to be processed in said display panel driving means, wherein said liquid crystal panel includes a first display area for displaying the television image and a second display area for displaying the computer graphic image, and said display panel driving means controls a display in each display area such that a display frequency of one of the first display area and the second display area is an integer multiple of a display frequency of the second display area and the first display area, respectively.

Claim 23

The method as recited in claim 20, further comprising: generating a display panel vertical synchronizing signal corresponding to a vertical driving frequency of said driving step; dividing a frequency of the display panel vertical synchronizing signal into one-half; and synchronizing the lighting timing of said light source with the driving timing of said liquid crystal display panel at every two screen period.

Claim 24

The method as recited claim 20, further comprising: generating a display panel horizontal synchronizing signal corresponding to a horizontal driving frequency of said liquid crystal panel by said driving step; and dividing a frequency of the display panel horizontal synchronizing signal so as to set the lighting frequency of said light source by dividing the frequency of the display panel horizontal synchronizing signal.