An optical system for optically imaging a sample including a nanoscale object comprising: an imaging lens; an illumination source configured to provide an excitation light; a detector; and a substrate for supporting the sample, wherein a sample interface, arranged to reflect the excitation light, is formed between the sample and a first side of the substrate facing the sample when a sample is applied on the substrate, wherein the optical imaging system is arranged such that the excitation light is sent into the substrate via the imaging lens and such that the detector receives a reference light and a scattered light, wherein the reference light comprises a part of the excitation light reflected at the sample interface and collected by the imaging lens and the scattered light comprises a part of the excitation light scattered by the nanoscale object and collected by the imaging lens,wherein the optical system is configured such that the nanoscale object is imaged at the detector, in response to the excitation light, by an optical contrast of an interference pattern between the reference light and the scattered light, wherein the substrate comprises an optical coating disposed on the first side of the substrate such that the sample is in contact with the optical coating when the sample is applied on the substrate, and wherein a degree of reflection of the excitation light at the sample interface is such that the optical contrast is larger compared to the optical contrast obtained with the sample interface formed without the optical coating; the optical system further comprising; a first optical element, configured to be a polarising beam splitter, and configured to separate a path for the excitation light into the imaging lens and a path for the reference light and the scattered light into the detector; a structured waveplate between the first optical element and the imaging lens, wherein the structured waveplate comprises an inner region configured to impart a first retardation to the excitation light and an outer region configured to impart a second retardation to the excitation light. an imaging lens; an illumination source configured to provide an excitation light; a detector; and a substrate for supporting the sample, wherein a sample interface, arranged to reflect the excitation light, is formed between the sample and a first side of the substrate facing the sample when a sample is applied on the substrate, wherein the optical imaging system is arranged such that the excitation light is sent into the substrate via the imaging lens and such that the detector receives a reference light and a scattered light, wherein the reference light comprises a part of the excitation light reflected at the sample interface and collected by the imaging lens and the scattered light comprises a part of the excitation light scattered by the nanoscale object and collected by the imaging lens,wherein the optical system is configured such that the nanoscale object is imaged at the detector, in response to the excitation light, by an optical contrast of an interference pattern between the reference light and the scattered light, wherein the substrate comprises an optical coating disposed on the first side of the substrate such that the sample is in contact with the optical coating when the sample is applied on the substrate, and wherein a degree of reflection of the excitation light at the sample interface is such that the optical contrast is larger compared to the optical contrast obtained with the sample interface formed without the optical coating; the optical system further comprising; a first optical element, configured to be a polarising beam splitter, and configured to separate a path for the excitation light into the imaging lens and a path for the reference light and the scattered light into the detector; a structured waveplate between the first optical element and the imaging lens, wherein the structured waveplate comprises an inner region configured to impart a first retardation to the excitation light and an outer region configured to impart a second retardation to the excitation light.