A mass spectrometer for analysis of a sample 5. A laser 1 is provided to illuminate at least part of the surface of the sample 5. Laser light is conducted via an optical fiber 2 and a zoom optical system 3 to the sample. A variable ion optical system 9,10,11 is provided to extract and focus ions released from the sample 5 onto a detector 12. The optical and ion optical systems operate continuously and synchronously to vary the fields of laser illumination and view of the sample such that they are substantially confocal and equal in diameter on the surface of the sample. The sample may be a MALDI sample.