Acousto-optical tunable filter element

Abstract

An acousto-optical filter element (114) is provided which has an acousto-optical crystal (118) having an acoustic signal transmitter (120) for generating acoustic signals in the acousto-optical crystal (118). The acousto-optical crystal (118) is designed to selectively spatially deflect light of a target wavelength from an input light beam (116) entering into the acousto-optical crystal (118), as a function of a high frequency applied to the acoustic signal transmitter (120), and to thereby produce a target light beam (126) having the target wavelength. In addition, the acousto-optical filter element (114) includes a spatial filter element (132) which is located in the target light beam (126) and is designed to selectively suppress the intensity of the target light beam (126) in a plane perpendicular to the propagation direction of the target light beam (126).

Description

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS[0001]This application is a Continuation of International Application No. PCT / EP2008 / 055355, filed Apr. 30, 2008, which is based upon and claims the benefit of priority from prior German Patent Application No. 10 2007 024 075.0, filed May 22, 2007, the entire contents of all of which are incorporated herein by reference in their entirety.FIELD OF THE INVENTION[0002]The present invention relates to an acousto-optical filter element according to the definition of the species set forth in claim 1. The present invention also relates to an adjustable light source which includes an acousto-optical filter element in accordance with the present invention, as well as to a microscope for capturing image information from a specimen that includes an adjustable light source in accordance with the present invention. Moreover, the present invention relates to an acousto-optical beam splitter which includes an acousto-optical filter element in accordanc...

AI Technical Summary

Benefits of technology

[0021]This transformation of the AOTF transfer function from the frequency domain into the spatial domain makes it possible for unwanted components to be removed by using appropriate spatial filtering.

[0031]In addition, the acousto-optical filter element may include a calibration device to rapidly and conveniently record the transfer function of the acousto-optical filter element, and to adjust the acousto-optical filter element accordingly. Thus, the calibration device may include a tunable, coherent test light source, for example, whose light beam may be coupled as an input light beam into the acousto-optical filter element, respectively the acousto-optical crystal. In addition, the calibration device may include a detector which is designed to measure an intensity of the target light beam.

[0034]The described acousto-optical filter element in one of the illustrated specific embodiments offers numerous advantages over conventional acousto-optical filter elements. Thus, in particular, the spectral transfer function may be selectively influenced, which has an especially positive effect on the laser spectroscopy and the laser microscopy. The acousto-optical filter element may be used to efficiently suppress excitation light and, in this manner, to substantially improve the signal-to-noise ratio.

Problems solved by technology

Supplying excitation light having one or a plurality of predefined wavelengths presents a significant challenge to numerous known microscopes, regardless of the method used.

When working with conventional laser microscopes, the excitation light is supplied by one or a plurality of excitation lasers; typically, however, merely a limited wavelength region, respectively a limited selection of spectral lines being available.

As a result, the microscopes are limited in their application to certain specimen types, specific microscopy methods, and / or to specific dyes used in staining the specimen.

In many cases, this limited application spectrum is not satisfactory.

However, a difficulty encountered when working with the known acousto-optical filters is that, in practice, there is not a unique correlation between an incoupled radio frequency of one acoustic wave and a specific target wavelength.

This means that the transfer function of an AOTF has numerous secondary maxima, which may be considerably less pronounced than the central principal maximum at the frequency f0, respectively the wavelength λ0 of the light, but can have the effect of interfering with the spectroscopy, however.

However, wavelength-selective elements, which are supposed to separate the actual excitation light from the detection light, are often so highly wavelength-selective that they merely separate the actual detection light (for example, fluorescent light of the specimen) from a specific excitation wavelength λ0), but do not ensure an adequate separation in the case of excitation light outside of the wavelength λ0.

This can lead to excitation light reaching the detector which, in turn, seriously degrades the signal-to-noise ratio of the specimen image.

Thus, in the case of a fluorescence spectroscopy, the actual fluorescence signals, in particular, can be weaker by orders of magnitude than the excitation light, so that the actual signal is seriously degraded by the excitation light that also reaches the detector.

This difficulty is especially evident when working with microscopes where excitation light and detection light are separated with the aid of acousto-optical beam splitters, AOBS.

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