Calibration of a spatial light modulator

1. A method for calibrating a spatial light modulator comprising an array of individually addressable channels, the method comprising:

selecting a plurality of channel sets from the array of channels, each channel set comprising a plurality of channels;

operating each of the channel sets to provide corresponding first output radiation;

determining a plurality of intensity values, each of the intensity values corresponding to the first output radiation provided by a different one of the channel sets;

selecting a first intensity value from the plurality of intensity values, wherein the first intensity value corresponds to a first channel set in the plurality of channel sets;

determining a difference between the first intensity value and a first target intensity value;

performing a channel set adjustment, the channel set adjustment comprising adjusting a control level of each channel in the first channel set to reduce the determined difference between the first intensity value and the first target intensity value;

selecting a plurality of channel subsets from the first channel set;

providing a correction factor for each channel subset; and

performing a channel subset adjustment, the channel subset adjustment comprising adjusting a control level of at least one channel in each of at least one of the channel subsets in accordance with a corresponding one of the correction factors.

2. A method according to claim 1 , wherein the channel subset adjustment is performed after performing the channel set adjustment.

3. A method according to claim 2 , comprising employing each of the correction factors in a subsequent recalibration of the spatial light modulator, wherein each correction factor remains unaltered during the subsequent recalibration of the spatial light modulator.

4. A method according to claim 3 , wherein the channel subset adjustment is performed without performing the channel set adjustment during the subsequent recalibration of the spatial light modulator.

5. A method according to claim 1 , wherein the channel subset adjustment comprises:

selecting a first channel subset from the plurality of channel subsets;

operating the first channel subset to emit second output radiation;

determining a second intensity value for the second output radiation;

modifying the second intensity value in accordance with the correction factor corresponding to the first channel subset;

determining a difference between the modified second intensity value and a second target intensity value; and

performing the channel subset adjustment on the first channel subset to reduce the determined difference between the modified second intensity value and the second target intensity value.

6. A method according to claim 5 , wherein the first target intensity value is equal to one of the plurality of intensity values other than the first intensity value.

7. A method according to claim 5 , wherein the first target intensity value is determined by a distribution of the plurality of intensity values.

8. A method according to claim 5 , wherein the second target intensity value is equal to the first target intensity value.

9. A method according to claim 1 , wherein each of the channel sets is operated separately to provide corresponding first output radiation.