Automatic brightness control system and method for a display device using a logarithmic sensor

Claim 2

A display device having an automatic brightness control system, comprising: a lighted display; a sensor disposed to logarithmically sense ambient light near the lighted display; and control circuitry connected to receive a first signal from the light sensor, the control circuitry connected to provide a display luminance to the lighted display, where the control circuitry selects the display luminance from at least one luminance adjustment sequence, where each luminance adjustment sequence has a plurality of luminance values with constant ratio steps, and where the display luminance is controlled by a transfer function that includes a term having a power relation to the ambient light near the lighted display and where an exponent of the term is a fraction.

Claim 3

The display device according to claim 1 , where the fractional power function is adjusted by a constant ratio offset.

Claim 4

The display device according to claim 1 , where the control circuitry further comprises digital-to-analog converter (DAC) circuitry, where the DAC circuitry converts the luminance value into an analog signal.

Claim 5

The display device according to claim 1 , where the control circuitry comprises at least one digital to analog converter (DAC) connected to provide the display luminance to the lighted display, where the sensor provides the first signal with essentially equal DAC increments to the DAC, where the DAC increments correlate to constant ratio steps.

Claim 6

The display device according to claim 1 , where the display luminance provides a brightness level according to the equation, B = Bo · [ B   max B   min ] ( ( SNS - So ) / ( T - 1 ) ) · BGL C where B is a display emitted luminance, Bo is a constant corresponding to a brightness offset on a log-log plot of the relationship between the display emitted luminance and the display background illuminance, Bmax is a maximum display brightness, Bmin is a minimum display brightness, SNS is a selected step number, S O is a midpoint of an SNS range, T is a total number of brightness steps, BGL is a display background luminance due to reflected ambient light, and C is an exponent describing the slope on a log-log plot of the relationship between the display emitted luminance and the display background illuminance.

Claim 7

The display device according to claim 5 , where the relationship between the display emitted luminance and the display background illuminance is according the equation, B=Bo·BGL C .

Claim 8

The display device according to claim 5 where C is in the range of about 0 through about 1.

Claim 9

The display device according to claim 5 , where C is a positive fraction.

Claim 10

The display device according to claim 1 , where the lighted display further comprises: a display panel; and a backlight operatively disposed adjacent to the display panel.

Claim 11

The display device according to claim 9 , where the display panel is an active matrix liquid crystal display.

Claim 12

The display device according to claim 9 , where the backlight comprises at least one of a cold cathode fluorescent lamp, and electro-luminescent lamp, and a light emitting diode (LED).

Claim 13

The display device according to claim 1 , where the lighted display is a backlit display.

Claim 14

The display device according to claim 1 , where the lighted display is a frontlit display.

Claim 15

The display device according to claim 1 , where the lighted display is an emissive display.

Claim 16

The display device according to claim 1 , where the lighted display comprises a pixel light source.

Claim 17

The display device according to claim 15 , where the pixel light source comprises a light emitting diode.

Claim 18

The display device according to claim 1 , where the sensor is a logarithmic sensor.

Claim 19

The display device according to claim 17 , where the logarithmic sensor comprises a logarithmic amplifier connected to a photodiode.

Claim 20

The display device according to claim 1 , where essentially all the luminance values have constant ratio steps in the luminance adjustment sequence.

Claim 21

The display device according to claim 1 , where the control circuitry determines a first display luminance value from a first luminance adjustment sequence, the first display luminance corresponding to the first signal from the light sensor, where the control circuitry determines a second display luminance value from a second luminance adjustment sequence, the second display luminance value corresponding to a user brightness selection, and where the control circuitry selects the display luminance from one of the first and second display luminance values.

Claim 22

The display device according to claim 1 , where a look-up table provides the at least one luminance adjustment sequence.

Claim 23

The display device according to claim 1 , where the control circuitry calculates at least one of a look-up table and the luminance value, the look-up chart to provide the at least one luminance adjustment sequence.

Claim 24

The display device according to claim 22 , where the control circuitry further comprises at least one microprocessor to calculate at least one of the look-up table and the luminance value.

Claim 25

The display device according to claim 1 , further comprising a bezel having a surface adjacent to the display panel, and where the sensor is disposed on the surface.

Claim 26

The display device according to claim 1 , where the display device is part of a navigation radio.

Claim 27

The display device according to claim 1 , where the control circuitry comprises at least one integrated circuit (IC) chip.

Claim 28

The display device according to claim 1 , where the display device is connected to a remote control device.

Claim 29

The display device according to claim 1 , where the display device comprises a display of an electronic device.

Claim 30

The display device according to claim 28 , where the electronic device is one of a communication device, a personal computer, and a personal organizer.

Claim 31

A display device having an automatic brightness control system, comprising: a lighted display; a sensor disposed to logarithmically sense ambient light near the display panel; a user interface; and control circuitry connected to receive a first signal from the sensor, the control circuitry connected to receive at least one user brightness selection from the user interface, the control circuitry connected to provide a display luminance to the lighted display, where the control circuitry selects the display luminance from at least one luminance adjustment sequence, where each luminance adjustment sequence has a plurality of luminance values with constant ratio steps, where the display luminance is controlled by a transfer function that includes a term having a power relation to the ambient light near the lighted display and where an exponent of the term is a fraction and, where the transfer function is adjusted by a constant ratio offset based on the at least one user brightness selection.

Claim 32

A display device having an automatic brightness control system, comprising: a lighted display; a sensor disposed to logarithmically sense ambient light near the display panel; a user interface; and control circuitry connected to receive a first signal from the sensor, the control circuitry connected to receive at least one user brightness selection from the user interface, the control circuitry connected to provide a display luminance to the lighted display, where the control circuitry selects the display luminance from at least one luminance adjustment sequence, where each luminance adjustment sequence has a plurality of luminance values with constant ratio steps, where the display luminance is controlled by a transfer function that includes a term having a power relation to the ambient light near the lighted display and where an exponent of the term is a fraction and, where the transfer function is adjusted by a constant ratio offset based on the at least one user brightness selection.

Claim 33

The display device according to claim 30 , where the control circuitry comprises at least one digital to analog converter (DAC) connected to provide the display luminance to the lighted display, where the sensor provides the first signal with essentially equal DAC increments to the DAC, where the DAC increments correlate to constant ratio steps.

Claim 34

The display device according to claim 30 , where the display luminance provides a brightness level according to the equation, B = Bo · [ B   max B   min ] ( ( SNS - So ) / ( T - 1 ) ) · BGL C where B is a display emitted luminance, Bo is a constant corresponding to a brightness offset on a log-log plot of the relationship between the display emitted luminance and the display background illuminance, Bmax is a maximum display brightness, Bmin is a minimum display brightness, SNS is a selected step number, S O is a midpoint of an SNS range, T is a total number of brightness steps, BGL is a display background luminance due to reflected ambient light, and C is an exponent describing the slope on a log-log plot of the relationship between the display emitted luminance and the display background illuminance.

Claim 35

The display device according to claim 32 , where the relationship between the display emitted luminance and the display background illuminance is according to the equation, B=Bo·BGL C .

Claim 36

The display device according to claim 32 where C is in the range of about 0 through about 1.

Claim 37

The display device according to claim 32 , where C is a positive fraction.

Claim 38

The display device according to claim 30 , where the control circuitry determines a first luminance value from a first luminance adjustment sequence, the first luminance value corresponding to at least one of the first signal and a first user brightness selection, where the control circuitry determines a second luminance value from a second luminance adjustment sequence, the second luminance value corresponding to at least one of the first signal and a second user brightness selection, where the control circuitry selects the display luminance from one of the first and second luminance values, and where the constant luminance ratio offset is based on one of the first and second user brightness selections.

Claim 39

The display device according to claim 30 , where the control circuitry calculates at least one of a look-up chart and the luminance value, the look-up chart to provide the at least one luminance adjustment sequence.

Claim 40

The backlight display device according to claim 30 , further comprising a bezel having a surface adjacent to the display panel, where the sensor is disposed on the surface, and where the user interface is disposed on the bezel.

Claim 41

The display device according to claim 30 , where the control circuitry selects the luminance value from a manual luminance adjustment sequence when at least one user brightness selection includes a manual mode.

Claim 42

The display device according to claim 30 , where the control circuitry selects the luminance value corresponding to a step number from a manual luminance adjustment sequence when at least one user brightness selection includes a manual mode and the step number selection.

Claim 43

The display device according to claim 30 , where at least one user brightness selection includes one of a manual mode and an automatic mode and provides a determination of one of daytime and nighttime, where the control circuitry selects a manual night luminance value as the luminance value when at least one user brightness selection is a nighttime manual mode, the manual night luminance value provided by a manual night luminance adjustment sequence, where the control circuitry selects a manual day luminance value as the luminance value when at least one user brightness selection is a daytime manual mode, the manual day luminance value provided by a manual day luminance adjustment sequence, where the control circuitry selects an automatic night luminance value as the luminance value when the at least one user brightness selection is a nighttime automatic mode, the automatic night luminance value provided by an automatic night luminance adjustment sequence, and where the control circuitry selects an automatic day luminance value as the luminance value when the at least one user brightness selection is a daytime automatic mode, the automatic day luminance value provided by an automatic day luminance adjustment sequence.

Claim 46

The method according to claim 42 , where (a) further comprises: sensing the ambient light on the display panel; providing an analog signal in response to the ambient light; and logarithmically amplifying the analog signal to generate the first signal.

Claim 47

The method according to claim 42 , further comprising providing the display luminance with a brightness level according to the equation, B = B0 · [ B   max B   min ] ( ( SNS - So ) / ( T - 1 ) ) · BGL C where B is a display emitted luminance, Bo is a constant corresponding to a brightness offset on a log-log plot of the relationship between the display emitted luminance and the display background illuminance, Bmax is a maximum display brightness, Bmin is a minimum display brightness, SNS is a selected step number, SO is a midpoint of an SNS range, T is a total number of brightness steps, BGL is a display background luminance due to reflected ambient light, and C is an exponent describing the slope on a log-log plot of the relationship between the display emitted luminance and the display background illuminance.

Claim 48

The method according to claim 44 , where the relationship between the display emitted luminance and the display background illuminance is according to the equation, B=Bo·BGL C .

Claim 49

The method according to claim 42 , where (b) further comprises: determining a first luminance value from a first luminance adjustment sequence, the first luminance value corresponding to the first signal; determining a second luminance value from a second luminance adjustment sequence, the second luminance value corresponding to at least one user brightness selection; and selecting the display luminance from one of the first and second luminance values.

Claim 50

The method according to claim 42 , further comprising: providing a determination of one of daytime and nighttime; where if the determination is nighttime, selecting a night luminance value as the luminance value, the night luminance value provided by a night luminance adjustment sequence, the night luminance value corresponding to the step level commanded by the instrument dimming control or other nighttime control; and where if the determination is daytime, selecting a day luminance value as the luminance value, the day luminance value provided by a day luminance adjustment sequence, the day luminance value corresponding to the first signal.

Claim 51

The method according to claim 47 , further comprising: comparing the first signal to a threshold, where signals below the threshold indicate nighttime, where signals above the threshold indicate daytime; where if the first signal is below the threshold, providing a nighttime determination; and where if the first signal is above the threshold, providing a daytime determination.

Claim 52

The method according to claim 47 , where the display device is provided in a vehicle having at least one headlight, where the at least one headlight is turned-on.

Claim 53

The method according to claim 47 , where the display device is provided in a vehicle having dashboard lights, and further comprising adjusting the night luminance value in response to a dimming level of the dashboard lights.

Claim 54

The method according to claim 47 , further comprising filtering the day luminance to control fluttering from changes in the ambient light.

Claim 55

The method according to claim 42 , where (b) further comprises selecting the luminance value from at least one luminance adjustment sequence provided on a look-up table.

Claim 56

The method according to claim 42 , where (b) further comprises calculating at least one of a look-up table and the luminance value, the look-up table to provide the at least one luminance adjustment sequence.

Claim 59

The display device according to claim 54 , further comprising providing the display luminance with a brightness level according to the equation, B = B0 · [ B   max B   min ] ( ( SNS - So ) / ( T - 1 ) ) · BGL C where B is a display emitted luminance, Bo is a constant corresponding to a brightness offset on a log-log plot of the relationship between the display emitted luminance and the display background illuminance, Bmax is a maximum display brightness, Bmin is a minimum display brightness, SNS is a selected step number, S O is a midpoint of an SNS range, T is a total number of brightness steps, BGL is a display background luminance due to reflected ambient light, and C is an exponent describing the slope on a log-log plot of the relationship between the display emitted luminance and the display background illuminance.

Claim 60

The display device according to claim 55 , where the relationship between the display emitted luminance and the display background illuminance is according to the equation, B=Bo·BGL C .

Claim 61

The method according to claim 54 , where (a) further comprises receiving the at least one user brightness selection from a user interface.

Claim 62

The method according to claim 54 , where (c), when at least one user brightness selection includes a manual mode, further comprises selecting the display luminance from a manual luminance adjustment sequence.

Claim 63

The method according to claim 54 , where (c), when the at least one user brightness selection includes a manual mode and a step number selection, further comprises selecting the display luminance corresponding to the step number selection on a manual luminance adjustment sequence.

Claim 64

The method according to claim 54 , where step (c), when the at least one user brightness selection includes a manual mode, further comprises: providing a determination of one of daytime and nighttime; where if the determination is nighttime, selecting a manual night luminance value as the luminance value, the manual night luminance value provided by a manual night luminance adjustment sequence; and where if the determination is daytime, selecting a manual day luminance value as the luminance value, the manual day luminance value provided by a manual day luminance adjustment sequence.

Claim 65

The method according to claim 60 , where the at least one user brightness selection provides the determination of one of daytime and nighttime.

Claim 66

The method according to claim 60 , where step (c), when the at least one user brightness selection includes an automatic mode, further comprises: providing a determination of one of daytime and nighttime; where if the determination is nighttime, selecting an automatic night luminance value as the luminance value, the automatic night luminance value provided by an automatic night luminance adjustment sequence; and where if the determination is daytime, selecting a automatic day luminance value as the luminance value, the automatic day luminance value provided by an automatic day luminance adjustment sequence.

Claim 67

The method according to claim 54 , where essentially all the luminance values have constant ratio steps in each luminance adjustment sequence.