LED testing process and correction methods therefor

An LED testing process performed on a panel of LEDs, the process comprising the steps of:

• measuring at least one optical parameter of an LED under test on the panel, light from said LED being emitted within a field of view of an optical detector;
• determining a number of inactive LEDs on the panel within the field of view;
• obtaining a correction factor, said correction factor being derived from a correction function which depends on the number of inactive LEDs which are arranged within the field of view of the detector when the optical detector detects light emitted by the LED under test;
• and
• applying the correction factor to the measured optical parameter.

A system for generating a correction function for an LED testing process for a panel of LEDs, the system comprising:

• an optical detector having a field of view;
• a reference LED having known optical properties;
• an actuator for positioning the optical detector to detect light emitted by the reference LED, or by an active LED having identical optical properties to the reference LED, and reflected from one or more inactive LEDs of the panel within the field of view;
• a mask for varying a number of said inactive LEDs within the field of view such that uncorrected values of at least one optical parameter of the detected light are derivable as a function of the number of inactive LEDs within the field of view;
• and
• at least one processor for calculating differences between the uncorrected values and a reference value, the reference value being determinable by detecting light emitted by the reference LED or the active LED in the absence of any other LEDs to generate a correction function, the correction function being based on the number of inactive LEDs which are arranged within the field of view when the optical detector detects light emitted by an LED under test.

A system for generating a correction function for an LED testing process for a panel of LEDs, the system comprising:

• an optical detector having a reflective internal surface and an input port defining a field of view, the optical detector being configured to measure at least one optical parameter of light detected by the optical detector;
• a reference LED having known optical properties and being positionable to illuminate the internal surface of the optical detector;
• a diffusely-reflecting reference surface over which the input port is positionable to detect reflected light from the reference surface;
• and
• an actuator for positioning the input port over the panel at a plurality of locations to thereby vary a number of LEDs within the field of view, to illuminate said LEDs with light reflected from the internal surface of the detector, and to detect light reflected from said LEDs;
• wherein:
• the input port is positionable over the diffusely-reflecting reference surface to measure the at least one optical parameter and to thereby obtain a reference value for the at least one optical parameter;
• and
• the input port is positionable over the plurality of locations to obtain a plurality of uncorrected values for the at least one optical parameter.

A method of generating a map of correction factors for an LED testing process, the method comprising the steps of:

• detecting light emitted by a reference LED and reflected from one or more inactive LEDs which neighbor a location on a panel of LEDs, the location being varied such that uncorrected values of at least one optical parameter are derivable as a function of location;
• detecting light emitted by the reference LED, or by an active LED having identical optical properties to the reference LED, in the absence of any other LEDs, to determine at least one reference value for said at least one optical parameter;
• and
• calculating differences between the uncorrected values and said at least one reference value to generate the map of correction factors, the map of correction factors being based on the number of inactive LEDs which are arranged within the field of view of the detector when the detector detects light emitted by the LED under test.