Arrangement for and method of determining cantilever deflection in a scanning probe microscopy system

An arrangement for determining cantilever deflection in a scanning probe microscopy system, the scanning probe microscopy system including a scan head supporting a probe, the probe including the cantilever and a probe tip, wherein at least one side of the cantilever or the probe tip comprises a specular reflective surface, and wherein the arrangement comprises:

• an optical source for providing an optical beam, wherein the arrangement is configured for impinging the optical beam onto the specular reflective surface such as to yield a reflected beam which is reflected from the specular reflective surface;
• and
• an optical sensor, wherein the arrangement is configured for receiving the reflected beam with the optical sensor for forming a light spot on the optical sensor, the optical sensor being configured for providing a sensor signal from which location information of a location of the light spot on the optical sensor is obtainable;
• wherein the optical sensor comprises an array of photo diode elements, wherein each photo diode element is configured for providing a photo diode signal to be included in the sensor signal, and wherein each photo diode element comprises a photo sensitive surface having an effective area dimension in a plane transverse to the beam direction which is smaller than the cross sectional area of the reflective beam, such that the effective area is smaller than the size of the light spot,
• wherein a first subset of contiguous photo diodes of the array of photo diodes comprises photo diode elements sensitive in a first wavelength range, and wherein a second subset of contiguous photo diodes of the array of photo diodes comprises photo diode elements sensitive in a second wavelength range, wherein the photo diode elements forming the first subset are different from the photo diode elements forming the second subset.