An apparatus for controlling a plurality of optical traps (OT1,OT2,OT3), the apparatus comprising - trapping beam optics (TL1,TL2,TL3) configured to provide a plurality of simultaneously active trapping beams (TB1,TB2,TB3), - controllable mirrors (M1,M2,M3) configured to receive and redirect the trapping beams (TB1,TB2,TB3) for individually controlling a respective position (X,Y) of a plurality of simultaneously active optical traps (OT1,OT2,OT3) formed by focusing of the redirected trapping beams in a sample volume; - light detectors (PSD1,PSD2) configured to receive light (L11,L20) from the sample volume corresponding to the optical traps (OT1,OT3); - detector beam optics configured to overlap a path of a detector beam with one of the trapping beams, wherein the detector beam has a distinct wavelength (λA) from that of the overlapping trapping beam; and - a wavelength filter disposed in a light path between the sample volume and a first light detector, and configured to pass light with the wavelength (λA) of the detector beam to the first light detector; wherein - the trapping beam optics (TL1,TL2,TL3) are configured to provide at least three simultaneously active trapping beams (TB1,TB2,TB3), wherein a first of the trapping beams is provided with a first polarization (//), and the other trapping beams (TB2,TB3) are provided with a second polarization (⊥), orthogonal to the first polarization (//); - the detector beam optics are configured to overlap the detector beam with one of the other trapping beams having the second polarization (⊥) wherein the wavelength (λA) of the detector beam is distinct from that of the said other trapping beams (TB2,TB3); and - the apparatus comprises a polarization filter disposed in a light path between the sample volume and a second light detector, and configured to pass light with the first polarization (//) to the second light detector; - characterized in that the light detectors (PSD1,PSD2) are configured to monitor at least two of the optical traps by measuring the light with the wavelength (λA) of the detector beam at the first detector and measuring the light with the first polarization (//) at the second light detector. - trapping beam optics (TL1,TL2,TL3) configured to provide a plurality of simultaneously active trapping beams (TB1,TB2,TB3), - controllable mirrors (M1,M2,M3) configured to receive and redirect the trapping beams (TB1,TB2,TB3) for individually controlling a respective position (X,Y) of a plurality of simultaneously active optical traps (OT1,OT2,OT3) formed by focusing of the redirected trapping beams in a sample volume; - light detectors (PSD1,PSD2) configured to receive light (L11,L20) from the sample volume corresponding to the optical traps (OT1,OT3); - detector beam optics configured to overlap a path of a detector beam with one of the trapping beams, wherein the detector beam has a distinct wavelength (λA) from that of the overlapping trapping beam; and - a wavelength filter disposed in a light path between the sample volume and a first light detector, and configured to pass light with the wavelength (λA) of the detector beam to the first light detector; wherein - the trapping beam optics (TL1,TL2,TL3) are configured to provide at least three simultaneously active trapping beams (TB1,TB2,TB3), wherein a first of the trapping beams is provided with a first polarization (//), and the other trapping beams (TB2,TB3) are provided with a second polarization (⊥), orthogonal to the first polarization (//); - the detector beam optics are configured to overlap the detector beam with one of the other trapping beams having the second polarization (⊥) wherein the wavelength (λA) of the detector beam is distinct from that of the said other trapping beams (TB2,TB3); and - the apparatus comprises a polarization filter disposed in a light path between the sample volume and a second light detector, and configured to pass light with the first polarization (//) to the second light detector; - characterized in that the light detectors (PSD1,PSD2) are configured to monitor at least two of the optical traps by measuring the light with the wavelength (λA) of the detector beam at the first detector and measuring the light with the first polarization (//) at the second light detector.