Optical: systems and elements – Mirror – With support
Reexamination Certificate
2000-12-08
2001-10-30
Sikder, Mohammad (Department: 2872)
Optical: systems and elements
Mirror
With support
C359S871000, C359S197100, C359S212100, C359S223100, C359S225100
Reexamination Certificate
active
06309078
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to systems for optical imaging in wide-field epifluorescence microscopy, and particularly to the use of alternative wavelength-selective mirrors, such as dichroic mirrors, that pass light of one wavelength range along one optical pathway, while reflecting light of another wavelength range along another optical pathway.
BACKGROUND OF THE INVENTION
In the field of epifluorescence microscopy biochemical material samples that have been Lagged with fluorescent markers often are imaged with a beam of light that excites markers within the samples to fluoresce. The fluorescence light emitted from the sample depends on the markers that have been used with the sample. While a sample is illuminated with excitation light, a microscope images fluorescence light emitted from the sample onto an image detector, such as a CCD array or image tube, in a camera, to determine the spatial distribution of fluorescence light intensity.
It is apparent that the emitted fluorescence light must be distinguished from the excitation light to the detect spatial distribution of fluorescent markers in the sample. This requires spatially separating from a common optical pathway at the sample the respective optical pathways of the incoming excitation light and the outgoing fluorescence light. This is ordinarily accomplished using a wavelength-selective mirror, that is, a device that accepts an excitation light beam emitted by an excitation light source along a source pathway and directs it along the common pathway, and receives fluorescence light emitted by an excited sample along the common pathway and directs it along a detector pathway to a camera. While other types of wavelength-selective devices might be used, dichroic mirrors are particularly suitable for this application because, in addition to their optical property of reflecting light having one wavelength and passing light of different wavelengths, they are typically thin and lightweight.
Often it is desirable to use several different wavelength-selective mirrors in an epifluorescence microscope to accommodate different excitation and emission wavelengths. This requires some mechanism to switch from one mirror to another.
One way of switching mirrors is to use a sliding elongate carriage that has two or more alternative mirrors mounted thereon adjacent one another so that, as the carriage is moved back and forth along its elongate axis, one of the mirrors is selected to interrupt the common pathway of the excitation and emission light beams. However, such mechanisms have relatively slow switching speeds because of the inertia that must be overcome to replace one mirror with another. This limits the speed with which epifluorescence microscopy can be used to process samples. The starting and stopping of such linear devices also tends to impart vibrational energy to the entire imaging instrument.
Another known way of switching mirrors is to mount them on a rotating carousel whose axis of rotation is parallel to the optical axis of the light beam whose wavelengths require separation. This reduces the vibration problem, but makes less certain the registration of different images produced by different fluorescence wavelengths. It also suffers from the problem of inertia where the mirrors are required to start and stop, thereby limiting the speed with which measurements can be made.
Consequently, there is a need for a faster mechanism for switching wavelength-selective mirrors, particularly in wide-field, imaging epifluorescence microscopy where the registration of images at different wavelengths is important.
SUMMARY OF THE INVENTION
The aforementioned need has been met in the present invention by providing, in an epifluorescence imaging microscope, a substantially planar wavelength-selective mirror holder disposed askew to a common optical pathway, the holder having a plurality of mirrors mounted thereon and having an axle attached normal thereto for rotating the holder so as to place a selected one of the mirrors in the common optical pathway. A motor is connected to the axle for rotating the mirror holder, either selectively or continuously. When a selected mirror is placed in the common optical pathway, the pathway is split so that an excitation light beam of one wavelength traveling along a source optical pathway from a light source is reflected by the mirror along the common optical pathway toward a sample, while fluorescence light produced by the sample and directed back along the common optical pathway passes through the mirror to travel along a detector optical pathway to a detector.
Accordingly, it is a principal object of the present invention to provide a novel and improved method and apparatus for selecting wavelength-selective mirrors for placement in a common optical pathway to split that pathway based on the wavelength of light traveling along the pathway.
It is another object of the invention to provide a method and apparatus for selecting wavelength-selective mirrors in an epifluorescence microscope system.
It is a further object of the invention to provide a method and apparatus for rapidly selecting wavelength-selective mirrors in an epifluorescence microscope system.
It is yet another object of the invention to provide a method and apparatus for selecting wavelength-selective mirrors.
The foregoing and other objects, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings.
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Dromaretsky Alexander
Osipchuk Yuri
Axon Instruments, Inc.
Birdwell Janke & Durando, PLC
Sikder Mohammad
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