MTF measuring stand
PSF / MTF measuring stand
Background
In order to measure the imaging properties of optical components, a special measuring system has been developed at the Institute which makes it possible to determine the imaging properties and thus the optical quality of monofocal and multifocal systems. The measurement is carried out in accordance with EN/ISO11979.
Our measurement services and expert reports are frequently used by industrial customers, for example for the measurement and assessment of monofocal and bifocal intraocular lenses (IOLs) or bifocal contact lenses.
How it works
The basis for measuring the imaging properties of an optical component is the measurement of the point spread function (PSF, DIN/ISO 9334-9336). The PSF is the equivalent of a Dirac pulse for the optical system. By evaluating the image through the optical component, it is then possible to draw conclusions about its optical quality.
The most important criterion here is the resolution, i.e. the maximum line density (or spatial frequency) that can still be clearly recognized when imaging through the optical component. The measure of this resolution ratio is the modulation transfer function (MTF). This in turn can be derived directly from the PSF using a Fouier transformation.
Measurement setup
A laser light source generates highly parallel light using a special optical setup. This parallel light beam is directed onto the component to be tested. The enlarged image of the focus is then measured using a high-resolution and highly sensitive camera. Subsequent signal processing in the PC determines the quality of the optical image.
To measure intraocular lenses (IOL) or contact lenses, the optical properties of the natural environment must also be simulated. In the case of intraocular lenses, this is done using an artificial eye that simulates the refractive power of a typical cornea (in accordance with EN/ISO 11979). In addition, the IOL must be operated in a bath with physiological solution, as the refractive power and thus the imaging errors would be significantly greater if it were operated in air.
In the case of conical lenses, the refractive power and surface geometry must also be simulated using an artificial cornea. A particular challenge here is to protect the lenses from drying out and the associated change in imaging properties.
Services offered
The institute offers services in the field of optical design and optical metrology. With its many years of experience, the working group is an ideal partner for industry and research institutes, particularly in the field of measuring the imaging quality of optical components. The services offered include both measurements and expert opinions.
Based on existing measurements, we also offer an independent forum for comparing the imaging quality of different IOLs. We also offer a cost-effective way for doctors and private individuals to have individual measurements of specific IOLs carried out.