Abstract: A microscope comprises a microscope objective, a camera and an imaging optical system for imaging an object through the objective to the camera along a first optical path. A projection optical system is provided for projecting a test image onto the object through the objective, and the imaging optical system is configured to image the projected test image from the object to the camera through the objective and along at least part of the first optical path. A focus adjustment system is provided for focusing the test image at the camera. Using the same objective and the same camera for both imaging and focusing allows reduction of the cost of the microscope in comparison with known microscopes that provide separate focusing systems.

Abstract: A microscope for performing differential phase contrast (DPC) microscopy comprises an infinity-corrected microscope objective and a tube lens, and at least one lens configured to image a back focal plane of the microscope objective to a conjugate back focal plane outside of the microscope objective. An aperture stop is located at said conjugate back focal plane. The object plane is located between the objective and the illumination source, the illumination source being configurable to illuminate the object from any one of a plurality of locations that are angularly displaced about an axis that is perpendicular to the object plane. The illumination source is placed at a working distance from the object to allow the user unrestricted access to the specimen area. The microscope may use a standard objective, which reduces cost.

Abstract: A microscope comprises a microscope objective, a camera and an imaging optical system for imaging an object through the objective to the camera along a first optical path. A projection optical system is provided for projecting a test image onto the object through the objective, and the imaging optical system is configured to image the projected test image from the object to the camera through the objective and along at least part of the first optical path. A focus adjustment system is provided for focusing the test image at the camera. Using the same objective and the same camera for both imaging and focusing allows reduction of the cost of the microscope in comparison with known microscopes that provide separate focusing systems.

Abstract: The bit error ratio of digital data transmission equipment is measured by applying a bit error ratio test data stream to a signal path through the equipment, and coupling an interfering signal source into the signal path. Measurements of the bit error ratio of the equipment are acquired for different levels of interfering signal, and the gain error introduced by coupling the interfering signal source into the signal path is determined. The bit error ratio of the equipment in the absence of the interfering signal is estimated from the measurements of the bit error ratio and the gain error.