The invention relates to an imaging system 1 with two modalities, the system has a catheter 40 with an optical lens system 50 situated at an end of the catheter and optically connected to optical guide means 15 a. The lens system has a numerical aperture which is changeable between a first 1NA and second 2NA numerical aperture, 2NA being larger than 1NA. The imaging system also has an imaging unit 5 being arranged for optical imaging with the catheter 40. A first imaging modality 1IM and a second imaging modality 2IM are optically connectable with the optical lens system 50 of the catheter 40. The imaging system can change between imaging in two modes: (1) the first numerical aperture 1NA of the optical lens system 50 and the first imaging modality 1IM of the imaging unit 5, and (2) the second numerical aperture 2NA of the optical lens system 50 and the second imaging modality 2IM of the imaging unit 5. The invention can provide fast and flexible in- vivo imaging because the change between the first and the second imaging modality can be performed quite fast, and accordingly the first and second imaging modality can be chosen to complement each other.