ADJD-J823 查看數據表（PDF） - Avago Technologies

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ADJD-J823

Color Management Controller with Integrated RGB Photosensor

Avago Technologies 

Factory Calibration

Factory calibration is needed at a system level to create

a ‘snapshot’ of the initial conditions of the system. The

color management algorithm references the snapshot

data. In effect, the calibration data trims out variation in

the entire signal chain from LEDs to sensor to ADC. The

figure below shows the calibration procedure in brief.

First, the device is put into “open loop” mode in which the

color management algorithm is turned off.

Second, the host controller needs to determine the

optimum sensor sensitivity for the given brightness de-

tection level. The sensitivity is a combination of several

internal settings. Searching for the optimum settings can

be performed manually or through an automatic search

routine which is built into the device. The host can start

the routine by issuing a command to the device. The

device will then turn the LEDs (usually at maximum duty

factor) and start the search routine.

Next, the host needs to turn only the Red LEDs on. An

external camera must be set up to capture the CIE co-

ordinates of the RED LEDs. The scaled XYZ readings are

then written to the device. At the same time, the host

needs to instruct the device to sample the RGB sensor

and store the results.

This is repeated for the Green and Blue LEDs.

Lastly, the host needs to instruct the device to start a

calibration calculator. The calculator uses the camera

and sensor readings for each color to develop a map-

ping matrix that maps the RGB sensor to the standard

CIE color space.

The mapping matrix and other configuration data is the

device setup data referred to in the previous section.

Open Loop

Sensor Gain Self-Adjustment

Read and Store Red LEDs Data

Read and Store Green LEDs Data

Read and Store Blue LEDs Data

Compute Calibration Data

Store Calibration Data &

Other Configuration Data

Factory Calibration Flow Chart

For details, refer to application note 5241 ADJD-J823

programming manual



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