An optical system used in a charged particle beam inspection system. The optical system includes one or more optical lenses, and a compensation lens configured to compensate a drift of a focal length of a combination of the one or more optical lenses from a first medium to a second medium.

An apparatus for detecting movements of a sample with respect to an objective comprises imaging optics which include the objective, which have an image plane and which are configured to image light from at least one reference object that is connected to the sample arranged in front of the objective into reference object images in the image plane. The apparatus further comprises a camera which is arranged in the image plane of the imaging optics and which is configured to record the reference object images at consecutive points in time, and an optical device arranged between the objective and the camera in a plane that is Fourier-conjugated with respect to the image plane. The optical device is configured to mask out low spatial frequencies of reference object images which the imaging optics image into the image plane.

A compact microscope including an enclosure, a support element, a primary optical support element located within the enclosure and supported by the support element, at least one vibration isolating mount between the support element and the primary optical support element, an illumination section, an objective lens system, a sample stage mounted on the primary optical support element, an illumination optical system to direct an illumination light beam from the illumination section to the sample stage, and a return optical system to receive returned light from sample stage and transmit returned light to a detection apparatus, wherein the illumination optical system and return optical system are mounted on the primary optical support element.

A variable focal length lens device includes: a lens system whose refractive index changes in accordance with a drive signal to be inputted; an objective lens disposed on the same optical axis as the lens system; an image detector configured to detect an image of a measurement target through the lens system and the objective lens: a resonance-lock controller configured to tune the drive signal to a resonance frequency of the lens system; and a resonance-lock delay controller configured to divide a change in a frequency of the drive signal by a change amount set by the resonance-lock controller to step-by-step changes for n times by a preset reference value to delay the change in the frequency of the drive signal.

A method for determining a tilting of a coverslip in a microscope, which has an object lens facing the coverslip, includes defining at least three measuring points which span a plane on a surface of the coverslip. The following steps are carried out for each of the measuring points: directing a measuring light beam through the object lens to the respective measuring point; producing a reflection light beam by at least partial reflection at the respective measuring point; directing the reflection light beam through the object lens onto a position-sensitive sensor and detecting an incidence position thereon; and determining a distance of the respective measuring point from the object lens along an optical axis thereof based on the detected incidence position. Based on the determined distances, a tilting of the plane spanned by the at least three measuring points relative to the optical axis is determined.

Before an observation region of an imaging optical system (14) reaches an observation position in the cultivation container (50), a vertical position of the cultivation container (50) at the observation position is precedently detected by an auto-focus displacement sensor. In a case where an objective lens is moved in an optical axis direction on the basis of the position, an error between the precedently detected vertical position of the stage (51) at the observation position and a vertical position of the stage (51) at a time point when the observation region of the imaging optical system (14) is scanned up to the observation position is acquired, and the objective lens is moved in the optical axis direction on the basis of the error.

An apparatus is provided for monitoring a focal state of a microscope having an object plane and a main imaging area. The apparatus has an auxiliary light source providing an auxiliary light beam and coupling the auxiliary light beam into the microscope in such a way that the coupled auxiliary light beam runs within a plane which is spanned outside of the main imaging area by a straight line running in the object plane and a normal to the object plane, and that the coupled auxiliary light beam is inclined at an angle to a normal to the object plane. A part of the coupled auxiliary light beam reflected by a reference boundary surface in the microscope impinges on a registration device in an area of incidence. The registration device registers position changes of the area of incidence on the registration device.

An automatic focus system for an optical microscope that facilitates faster focusing by using at least two cameras. The first camera can be positioned in a first image forming conjugate plane and receives light from a first illumination source that transmits light in a first wavelength range. The second camera can be positioned at an offset distance from the first image forming conjugate plane and receives light from a second illumination source that transmits light in a second wavelength range.

An embodiment of an autofocus system (100, 400) is configured to receive a first signal (102a, 402a) corresponding to a first wavelength range and to receive a second signal (102b, 402b) corresponding to a second wavelength range. The autofocus system (100, 400) is further con-5 figured to determine an output signal (106, 406) comprising a focus setting information using the first signal (102a, 402a) and the second signal (102b, 402b).

A method and system for autofocusing an objective lens in a microscope system are disclosed. A decentered aperture is disposed in an optical path between an objective lens and an image plane of an image capturing device and a plurality of reference images are captured. Each reference image is captured when the objective lens is positioned at a corresponding z-position of a plurality of z-positions along an axis of travel of the objective lens and the optical path is at least partially occluded by the decentered aperture. At least one reference image of the plurality of the reference images is associated with a best focus position. The plurality of reference images are analyzed to develop a plurality of pattern locations, wherein each pattern location represents a position of a pattern formed on the image plane when a corresponding reference image was captured. The objective lens is positioned in accordance with the best focus position and the plurality of pattern locations.