Basler ace acA1920-155, Руководство пользователя, Страница: 268 / 326

Features AW00123404000
258 Basler ace USB 3.0
Using the Luminance Lookup Table for Cameras with 12 bit ADC Data and Pixel
Format Set for 8 Bit Output
As mentioned above, when the camera is set for a pixel format where it outputs 12 bits, the lookup
table is used to perform a 12 bit to 12 bit conversion. But the lookup table can also be used in 12
bit to 8 bit fashion. To use the table in 12 bit to 8 bit fashion, you enter 12 bit values into the table
and enable the table as you normally would. But instead of setting the camera for a pixel format that
results in a camera output with 12 bits effective, you set the camera for a pixel format that results
in 8 bit output (e.g., Mono 8). In this situation, the camera will first use the values in the table to do
a 12 bit to 12 bit conversion. It will then drop the 4 least significant bits of the converted value and
will transmit the 8 most significant bits.
Changing the Values in the Luminance Lookup Table and Enabling the Table
You can change the values in the luminance lookup table (LUT) and enable the use of the lookup
table. The following example refers to using 12 bit ADC data:

Use the LUT Selector to select a lookup table. (Currently there is only one lookup table
available, i.e., the "luminance" lookup table described above.)

Use the LUT Index parameter to select a value in the lookup table. The LUT Index parameter
selects the value in the table to change. The index number for the first value in the table is 0,
for the second value in the table is 1, for the third value in the table is 2, and so on.

Use the LUT Value parameter to set the selected value in the lookup table.

Use the LUT Index parameter and LUT value parameters to set other table values as desired.

Use the LUT Enable parameter to enable the table.
You can set the LUT Selector, the LUT Index parameter and the LUT Value parameter from within
your application software by using the Basler pylon API. The following code snippet illustrates using
the API to set the selector and the parameter values:
// Select the lookup table
camera.LUTSelector.SetValue(LUTSelector_Luminance);
// Write a lookup table to the device.
// The following lookup table causes an inversion of the sensor values
// ( bright -> dark, dark -> bright )
for ( int i = 0; i < 4096; i += 8 )
{
camera.LUTIndex.SetValue( i );
camera.LUTValue.SetValue( 4095 - i );
}
// Enable the lookup table
camera.LUTEnable.SetValue(true);
You can also use the Basler pylon Viewer application to easily set the parameters.
For more information about the pylon API and the pylon Viewer, see Section 3.1 on page 43 .