LED Test
The demands towards the stability of wavelength and luminance of LEDs used in numerous industrial sectors grow continuously. In the fields of home automation and automobiles, an automated testing of wavelength and intensity is required, because mono-chromatic and homogenous instrument lightning has to be ensured.
Such high quality demands and the need for a high number of produced items cannot be met by conducting random tests. Previous inspection systems have been able to conduct the testing satisfyingly and reliably but they have not been able to handle different layouts of circuit boards easily.
NOFFZ Computertechnology has developed a LED inspection tool, which is equipped with a high-resolution camera, suitable algorithms and look-up tables for inspection of LEDs being placed on various and different types of circuit boards. Exchangeable cassettes and adapters allow the inspection of different types of circuit boards without installing optical fibres.
A complete tester system including an exchangeable adapter system and an inspection area of 11.81” x 7.87” is also available. In addition to that, it is possible to conduct a complete functional testing of the circuit board by means of this single adapter.
LabVIEW and TestStand by National Instruments are deployed as the testing software. Due to the NOFFZ sequencer it is possible to realize a simple testing solution based on LabVIEW or to implement a flexible and extensive solution by means of TestStand.
Because of the intuitive GUI it is possible to calibrate the system via suitable reference LEDs and to execute automatic detection of all LEDs installed on a circuit board under test. LEDs are tested as a group, which is assigned adequate reference values for the required wavelength and homogeneity. Within a group, each LED is assigned a product number and a LED number. Limiting values for luminance measurements can be assigned to each group individually.
The automated test mode allows testing and optical inspection of the LEDs at high speed, including control via various established bus systems.
LEDs are empowered based on a PWM signal, whose frequency can be defined individually for each LED group. This frequency also provides a basis for the shutter timing of the inspection camera. Shutter times, which can be adjusted for adaption according to the particular lightning, are defined as a multiple of the periodic time of the PWM signal.
Such high quality demands and the need for a high number of produced items cannot be met by conducting random tests. Previous inspection systems have been able to conduct the testing satisfyingly and reliably but they have not been able to handle different layouts of circuit boards easily.
NOFFZ Computertechnology has developed a LED inspection tool, which is equipped with a high-resolution camera, suitable algorithms and look-up tables for inspection of LEDs being placed on various and different types of circuit boards. Exchangeable cassettes and adapters allow the inspection of different types of circuit boards without installing optical fibres.
A complete tester system including an exchangeable adapter system and an inspection area of 11.81” x 7.87” is also available. In addition to that, it is possible to conduct a complete functional testing of the circuit board by means of this single adapter.
LabVIEW and TestStand by National Instruments are deployed as the testing software. Due to the NOFFZ sequencer it is possible to realize a simple testing solution based on LabVIEW or to implement a flexible and extensive solution by means of TestStand.
Because of the intuitive GUI it is possible to calibrate the system via suitable reference LEDs and to execute automatic detection of all LEDs installed on a circuit board under test. LEDs are tested as a group, which is assigned adequate reference values for the required wavelength and homogeneity. Within a group, each LED is assigned a product number and a LED number. Limiting values for luminance measurements can be assigned to each group individually.
The automated test mode allows testing and optical inspection of the LEDs at high speed, including control via various established bus systems.
LEDs are empowered based on a PWM signal, whose frequency can be defined individually for each LED group. This frequency also provides a basis for the shutter timing of the inspection camera. Shutter times, which can be adjusted for adaption according to the particular lightning, are defined as a multiple of the periodic time of the PWM signal.
Advantages
- High flexibility for LED inspection on different types of circuit boards
- High number of tested items
- Measuring of luminance and wavelength with high precision
- Intuitive GUI
- Due to the assignment of LED numbers and product numbers simple identification of LEDs producing measurement data outside the limiting values of the specification is possible
- Variable shutter times for adaption to the particular lighting
- Optional: functional testing of the circuit board
Conclusion
The LED test toolkit is a modern system for testing LEDs on different circuit boards, offering high precision and a high number of tested items. It can be adapted to the ever changing demands towards modern test systems in every respect.