Optics: measuring and testing – Photometers – Heat absorbing
Reexamination Certificate
1999-09-17
2001-01-23
Font, Frank G. (Department: 2877)
Optics: measuring and testing
Photometers
Heat absorbing
C356S220000, C356S222000
Reexamination Certificate
active
06177988
ABSTRACT:
BACKGROUND OF THE INVENTION
a) Field of the Invention
The invention is directed to an arrangement for the measurement of optical radiation of radiation sources, especially radiation power.
b) Description of the Related Art
Power measuring devices for measuring optical radiation of radiation sources, especially also of laser radiation sources, can vary, for example, between power measuring devices for directionally radiating sources, also called power meters, such as bolometers, photodiodes, and power measuring devices for diffusely radiating sources (high-divergence sources) such as Ulbricht spheres.
Both types, both diffusely and directionally radiating fiber applicators with lengths of up to 10 cm and diameters up to 20 mm, are used in photodynarric therapy (PDT). Knowledge of the radiation power delivered by the applicator being used is crucial for the successful course and conclusion of treatment. At the present time, the principle of Ulbricht spheres is applied for power measurement.
An Ulbricht sphere of the type mentioned above is described in “ABC der Optik [The ABC's of Optics]”, VEB Brockhaus Verlag, Leipzig, 1961, 484-485, in connection with luminous flux meters. This Ulbricht sphere is constructed in such a way that the most uniform possible distribution of the emitted radiation takes place in the interior of the sphere. A part of the diffusely reflected radiation is converted by a suitable detector whose receiver surface is small in comparison to the inner surface of the sphere, e.g., by a photodiode, into an electric signal which is proportional to the radiation output. Further, this measuring device is disadvantageous in that the measurement values are also dependent on the size of the radiation sources to be measured and on their position in the sphere.
For this reason, in order to suppress possible radiation characteristics of expanded radiation sources, the Ulbricht sphere must be as large as possible, the inner surface must reflect as diffusely as possible, and the receiver must be small in comparison to the inner surface and must be protected from direct radiation. Taking into account the requirement for measurement of the above-mentioned applicators with a length of 10 cm and a diameter of 20 mm, an Ulbricht sphere necessary for this purpose is difficult to integrate in an existing device or device design already by virtue of its size and, moreover, increases the cost of manufacture.
OBJECT AND SUMMARY OF THE INVENTION
Accordingly, it is the primary object of the invention to provide a measuring arrangement which makes it possible to measure with great accuracy the optical radiation of a radiation source irrespective of the position of the radiation source in the measuring arrangement and independent from or dependent on its radiation characteristic in an economical manner, with a limited space requirement and without a diffusely reflecting inner surface.
The above object is achieved in accordance with the invention, by an arrangement for measuring the power or energy of optical radiation of radiation sources, especially laser radiation, having a housing. The arrangement comprises a module defining an open or at least partially closed hollow space. The module has inner and outer walls. The inner and outer walls of the module are entirely or partially occupied by detectors for generating measurement signals which are proportional to measured parameters of the radiation sources. The detectors are connected together in such a way that their generated measurement signals are further processed to form at least one resultant sum signal or the detectors are connected to a downstream processing device to form at least one resultant sum signal. The at least one resultant sum signal is relatively independent from the position, arrangement and radiating characteristic of the examined radiation source in the module. At least one opening or guide-through is provided in the module for inserting the radiation source to be examined.
Accordingly, in contrast to the known Ulbricht sphere, the measurement arrangement according to the invention is based on the principle of detecting and converting all radiation output acting on the arrangement, wherein virtually the total radiation output emitted by the radiation source is converted into proportional electrical measurement signals by corresponding detectors or converters.
In an advantageous embodiment form of the invention, said detectors for generating the measurement signals are constructed from one or more photoelectric detectors or receivers extensively covering the inner surface of the module. Large-area photodetectors are advantageously provided in the module. A direct conversion of the emitted radiation of the radiation source into processible electric measurement signals is carried out by means of an arrangement of this type. The detectors are connected in such a way that the measurement signals generated by them are summed and a conversion of radiation power to (electrical) signal which is as linearly proportional as possible is carried out. In this way, virtually the entire output of the radiation source can take part in signal formation. The sum signal formed in this way is sent to the input of the evaluating device.
Measurement gauges which react to heat or detectors which convert expansions caused by heat into electrical measurement signals, e.g., strain gauges, can also be arranged in or on the module as detectors. The detectors or measurement gauges are connected in such a way that the electrical signals generated by them are summed. These electrical signals are then likewise supplied to the evaluating device for further processing.
In another embodiment form, a processing of the individual measurement signals of the detectors can also be carried out in such a way that conclusions can be reached about the radiating characteristics of the radiation source. In this connection, the measurement signals are evaluated individually taking into account the position of the respective detectors within the module.
According to a further arrangement according to the invention, the walls of the module are constructed so as to be reflecting in that they are provided with one or more reflectors. Accordingly, the module comprises, for example, a base plate, a plate for receiving the radiation source to be investigated, and a reflector which is connected with the base plate, wherein the surface of the base plate facing the reflector and the inner surface of the receiving plate are extensively occupied by said detectors for generating measurement signals. In this way, among other things, a relatively large component of the radiation striking the detectors can contribute directly, or via additional optical elements, to the formation of the measurement signal.
The reflector itself is advantageously formed of a reflecting cylinder surface and a plane reflecting surface which is inclined relative to the base surface.
The evaluating circuit comprises an electronic summing circuit, known per se, for summing the signals generated by the receivers. Therefore, one electrical signal is generated for the totality of radiation released in the interior of the module, wherein this electrical signal is proportional, e.g., to the radiation power and is itself independent from the spatial position of the radiation source inside the module and from the size and radiating characteristic of the radiation source.
The housing enclosing the entire arrangement and the module, in at least one of its bounding surfaces, advantageously have an opening, wherein receiving means for receiving the radiation source to be measured project into the opening. Above all, these receiving means protect the interior of the module, which is the actual measuring space of the arrangement, from damaging outside influences.
The receiving means for the radiation source to be measured advantageously comprise a first tube which is transparent for the radiation and which is fixedly connected with the housing and is exchangeable.
For purposes of gauging and calib
Dubnack Steffen
Ernsperger Stefan
Luemkemann Frank
Weigand Heino
Carl Zeiss Jena GmbH
Font Frank G.
Nguyen Sang H.
Reed Smith LLP
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