- SS-HQ1 Application Notes -
Ver.1.0.0 January 7, 2005
116
Window0
Window2 Window4 Window3
Window1
Window0
Window2 Window4 Window3
Window1
10.6.3. Backlight Compensation
The SS-HQ1 system offers a backlight compensation function. This backlight compensation mode can be
switched ON and OFF in BLCOFF (CAT14_Byte1_Bit2).
As for the compensation method, it can be set to weighted average mode or compensation gain fixed mode by
switching BLCSEL (CAT13_Byte4_Bit0).
Weighted average mode
The screen is divided into five detection windows. Each window's integral
value for exposure is multiplied by the weighting value for backlight
compensation based on the weighted average. It is suitable for when the
main subject remains motionless on screen. (See “Fig 10.6-2 AE
Detection Windows of OPD”.)
For windows 0 to 4, the weighting to be applied can be assigned separately.
The range is 0[h] to 0F [h]. Each window's weighting value is specified in the
parameters shown in the "Table 10.6-6 Detection Windows Weighting
Values." For details on how to specify OPD detection windows, see "10.5
OPD Window Setting and Display."
Fig 10.6-2 AE Detection Windows of OPD
Note
If set so that the size of window 4 is extremely small and the weighting of windows 0 to 3 is 0, it will cause
rounding errors from the internal calculation. Care should be taken because this worsens the accuracy of AE
operation, resulting in an effect like oscillation.
Table 10.6-6 Detection Windows Weighting Values
(CAT14_AE2)
Parameter
Description
Settings range
AEW0 (Byte6_bit0-3)
Window 0 weighting value
00[h] to 0F[h] (0 to 1x)
AEW1 (Byte6_bit4-7)
Window 1 weighting value
00[h] to 0F[h] (0 to 1x)
AEW2 (Byte7_bit0-3)
Window 2 weighting value
00[h] to 0F[h] (0 to 1x)
AEW3 (Byte7_bit4-7)
Window 3 weighting value
00[h] to 0F[h](0 to 1x)
AEW4 (Byte8_bit0-3)
Window 4 weighting value
00[h] to 0F[h] (0 to 1x)
Compensation Gain Fixed Mode
Compensation gain fixed mode can be accessed by making BLCSEL = 1[h].
Backlight compensation is performed in compensation gain fixed mode by reducing the luminance integral
average value only by the compensation gain (fixed value) specified in the parameter FBLCGAIN
(CAT14_Byte5). In this mode, the supported gain range for compensation by means of FBLCGAIN follows
FBLCGAINSEL (CAT14_Byte4_bit1), determined as shown in the "Table 10.6-7 FBLCGAIN and
FBLCGAINSEL."