Abstract: A dark field digital holographic microscope is disclosed which is configured to determine a characteristic of interest of a structure. The dark field digital holographic microscope comprises an illumination device configured to provide at least: a first beam pair comprising a first illumination beam of radiation (1010) and a first reference beam of radiation (1030) and a second beam pair comprising a second illumination beam of radiation (1020) and a second reference beam of radiation (1040); and one or more optical elements (1070) operable to capture a first scattered radiation and to capture a second scattered radiation scattered by the structure resultant from the first and second illumination beams respectively. The beams of the first beam pair are mutually coherent and the beams of the second beam pair are mutually coherent. The illumination device is configured to impose incoherence (ADI) between the first beam pair and second beam pair.

Abstract: Methods and apparatus are disclosed for determining a characteristic of a structure. In one arrangement, the structure is illuminated with first illumination radiation to generate first scattered radiation. A first interference pattern is formed by interference between a portion of the first scattered radiation reaching a sensor and first reference radiation. The structure is also illuminated with second illumination radiation from a different direction. A second interference pattern is formed using second reference radiation. The first and second interference patterns are used to determine the characteristic of the structure. Azimuthal angles of the first and second reference radiations onto the sensor are different.

Abstract: Methods and apparatus are disclosed for determining a characteristic of a structure. In one arrangement, the structure is illuminated with first illumination radiation to generate first scattered radiation. A first interference pattern is formed by interference between a portion of the first scattered radiation reaching a sensor and first reference radiation. The structure is also illuminated with second illumination radiation from a different direction. A second interference pattern is formed using second reference radiation. The first and second interference patterns are used to determine the characteristic of the structure. Azimuthal angles of the first and second reference radiations onto the sensor are different.

Abstract: Methods and apparatus are disclosed for determining a characteristic of a structure. In one arrangement, the structure is illuminated with first illumination radiation to generate first scattered radiation. A first interference pattern is formed by interference between a portion of the first scattered radiation reaching a sensor and first reference radiation. The structure is also illuminated with second illumination radiation from a different direction. A second interference pattern is formed using second reference radiation. The first and second interference patterns are used to determine the characteristic of the structure. Azimuthal angles of the first and second reference radiations onto the sensor are different.