Alignment and testing of optical systems for infrared radiation

Beyond the visible

The infrared spectrum is invisible to the human eye. However, it is an important carrier of information. To use this information, suitable camera systems are needed – combinations of wavelength-transparent optics and wavelength-sensitive camera sensors. TRIOPTICS offers special measuring systems for testing and alignment of the IR optics and the complete IR camera system.

Detail of OptiCentric IR and ImageMaster HR IR

Quality control of imaging optics

The dependence of the imaging quality on the lenses and their alignment requires objective quality control. The measuring systems must either operate in the visual spectral range and measure in reflection, or be matched to the wavelength of the sample → video. As with all optics, parameters such as center thickness, centering and MTF are important quality criteria. In addition, non-contact measurement is often required.

Active alignment of camera modules

A good lens alone is not enough to achieve high image quality – the exact alignment of the lens to the camera sensor is also crucial for the image produced. Manual alignment of the optics to the sensor is uneconomical for large quantities. The requirement for low production tolerances also rules out manual alignment. Active alignment is therefore the most suitable manufacturing process for automated camera production

Applications

The different bands of the infrared spectrum are used for different applications:

SWIR and NIR
Spectroscopy: Detection of damage or different fillings for food sorting and quality control, wafer inspection or plastic type detection.

MWIR
High resolution, high contrast static images. Images are often output in black and white or false color without reference to temperature.

LWIR
Display of temperature information in calibrated instruments – classic thermal imaging camera.

Video-insight on IR optics:
Efficient testing throughout the manufacturing process

In this contribution, we present solutions how to make the manufacturing process of IR objective lenses most efficient by using adequate techniques for centration-based alignment testing, IR MTF analysis and non-contact determination of center thicknesses and air spacings.