WO2012092944A1

WO2012092944A1 - Method and device for determining the radiance of an infrared radiation source

Info

Publication number: WO2012092944A1
Application number: PCT/EP2011/006178
Authority: WO
Inventors: Sven Linow
Original assignee: Heraeus Noblelight Gmbh
Priority date: 2011-01-07
Filing date: 2011-12-08
Publication date: 2012-07-12
Also published as: DE102011016102A1

Abstract

The invention relates to a method for determining the radiance of a radiation source in at least one first wavelength range, wherein the absolute spectrally integrated radiance is measured in a second wavelength range, the type of radiation source is assigned at least one correction factor with which the absolute spectrally integrated radiance in the second wavelength range is corrected, with the result that the corrected value of the absolute spectrally integrated radiance in the second wavelength range corresponds to the at least one radiance in the first wavelength range. The invention also relates to a device for determining the radiance of a radiation source in at least one first wavelength range by means of such a method, wherein the device comprises a detector, which measures the absolute spectrally integrated radiance in a second wavelength range, the device comprises a storage unit, in which at least one correction factor is stored, the device comprises a computing unit, which can be used to calculate, from the absolute spectrally integrated radiance in the second wavelength range, the radiance of the radiation source in the at least one first wavelength range with the correction factor, and the device comprises an output unit, by means of which the result of the calculation can be output and/or can be displayed.

Description

METHOD AND DEVICE FOR DETERMINING THE RADIATION DENSITY OF AN INFRARED RADIATION SOURCE

The invention relates to a method and a device for determining the spectral radiance of a radiation source in at least a first wavelength range.

Methods for measuring electromagnetic radiation, in particular of light, also in the infrared range are known in the prior art. Frequently, however, not only is the absolute value of the radiance of interest integrated over an entire range of the spectrum, but also the spectral distribution of the intensity of the radiation. The intensity of electromagnetic radiation acts differently at different wavelengths. Spectroscopic measurements provide sufficient data for this purpose. The recording of a spectrum especially over a large wavelength range is very expensive.

For many safety regulations, the radiance in different wavelength ranges of relevance. Limits are defined via these radiances, which must not be exceeded.

The EU Artificial Optical Radiation Directive 2006/25 / EC and the Machinery Directive 2006/42 / EC prescribe the measurement and assessment of the radiation emitted by installations, in particular in the infrared range. In particular, CEN 12198-1, -2 and -3 and CEN 14255 and IEC 62471 each define procedures or procedures that are not technically feasible in the infrared.

The relevant measurements for infrared electrical heating systems concern [2006/25 / EC, IEC 62471: 2008]

1. the determination of blue light hazard in the range of 380 nm to 700 nm (VIS).

2. the determination of the risk of retinal combustion in the range of 380 nm to 1400 nm (VIS and IR-A).

CONFIRMATION COPY 3. the determination of the risk of retinal combustion in the range of 780 nm to 1400 nm (IR-A) for sources with a weak visual stimulus.

4. the determination of the risk of corneal burning in the range of 780 nm to 3000 nm (IR-A and IR-B).

5. the determination of the risk of burning of the skin in the range of 380 nm to 3000 nm (VIS, IR-A and IR-B).

For cases 1. 2. and 3. the spectral radiance has to be determined at suitable measuring locations. In addition, the spectral radiances are to be folded by means of spectral weights for blue light hazard or spectral weighting for retinal combustion.

A particularly detailed discussion of possible measurement methods can be found in the European standard CEN 14255-2, Annex E. The terms used in this specification are used in their definition in accordance with the IEC 62471: 2009 standard and are not reintroduced herewith and are hereby incorporated by reference.

The radiance or the spectrally weighted radiance for the determination of the retinal hazard (380 nm to 1400 nm) may be determined by one of the following methods A, B and C according to CEN 14255-2, Annex E; the radiance or the spectrally weighted radiance for the determination of blue light hazard (380 nm to 780 nm) can be determined by one of the following methods D to Q according to CEN 14255-2, Annex E; radiance or spectrally weighted radiance for determination of retinal hazard with low visual stimulus (780 nm to 1400 nm) may be determined by one of the following methods A, B and C according to CEN 14255-2, Annex E; In this case, the discussion of cases A, B and C is sufficient, since the other cases represent variations of the same methods:

Method A (radiometer calibrated in effective radiance (thermal damage to the retina)):

1. Measurement of the actual diameter D of the radiation source, the viewing distance r and the viewing angle Φ.

2. Calculation of the observation diameter of the radiation source, see CEN 1 255-2, equation (13). 3. Calculation of the angular extent of the radiation source, see CEN 14255-2, equation (14).

4. Measurement of the thermal retinal beam density in the wavelength range from 380 nm to 1400 nm with a radiometer calibrated for the measurement of the thermal retinal beam density. The required acceptance angle for the detector depends on the angular extent of the radiation source, d. h .: If the angular extent is smaller than or equal to 1, 7 mrad, the acceptance angle must be equal to 1.7 mrad. If the angular extent is greater than 1.7 mrad, the acceptance angle must not exceed the angular extent. In no case may the acceptance angle exceed 100 mrad. For an inhomogeneous radiation field, the acceptance angle must be sufficient to resolve inhomogeneities down to 1.7 mrad.

5. Measurement of exposure duration.

6 Calculation of the applicable limit using exposure time and angular spread.

7. Comparison of the measured thermal retinal radiance with the applicable

Limit.

A measuring device using this method is not commercially available for the wavelength range up to 1400 nm.

Method B (spectroradiometer with scanning monochromator):

1. Measurement of the actual diameter of the radiation source, the viewing distance and the viewing angle.

2. Calculation of the observation diameter of the radiation source, see CEN 14255-2, equation (13).

3. Calculation of the angular extent, see CEN 14255-2, equation (14).

4. Measurement of the spectral radiance in the wavelength range from 380 nm to 1 400 nm with a scanning spectroradiometer. The required acceptance angle for the detector depends on the angular extent of the radiation source. 5. Calculation of the thermal retinal radiance for the wavelength range from 380 nm to 1 400 nm, see CEN 14255-2, equation (9), which requires a convolution of the spectral radiance with the spectral weighting.

6. Measurement of exposure duration.

7. Calculation of the applicable limit using the exposure time and the angular extent.

8. Comparison of the measured thermal retinal radiance with the applicable

Limit.

A spectroradiometer with scanning monochromator scans the different radiation wavelengths step by step. Radiation density and radiance dose can be measured with suitable input optics or diaphragms. The result of the measurement is a spectrum that can be used to perform calculations of the weighted and unweighted radiance. Reliable results can only be obtained if the radiation flux density is constant during the sampling time.

Such a spectroradiometer with scanning monochromator must, to be technically feasible, have the following additional properties:

1. Appropriately sensitive detectors must be available to cover the required spectral range.

2. The instrument is suitable for calibration and the calibration should not be significantly altered during the performance of the measurement task, ie during the evaluation of the radiation of at least one unit.

3. The device must be easy to handle and survive in harsh industrial environments over the long term.

At least two different detectors must be used to cover the spectral range, so that the device will be extended by a detector changer, possibly a grating changer or the like. The response of semiconductor detectors generally varies greatly with wavelength, requiring regular adjustments of the optical system and calibration of the measuring equipment: in addition to the meter, the user must have an optical laboratory with suitable personnel to ensure the operation of this apparatus. The disadvantage is therefore the complex operation of such a spectroscopic radiometer, because the cost of the measurement quickly exceeds the cost of the device under test.

Method C (Spectroradiometer with Array Detector):

3. Calculation of the angular extent, see CEN 14255-2, equation (14).

4. Measurement of the spectral radiance in the wavelength range from 380 nm to 1 400 nm with an array spectroradiometer. The required acceptance angle for the detector depends on the angular extent of the radiation source.

5 Calculation of the thermal retinal beam density for the wavelength range from 380 nm to 1400 nm, see CEN 14255-2, equation (9), in which a folding of the spectral radiance is prescribed with the spectral weighting.

6. Measurement of exposure duration.

8. Comparison of the measured thermal retinal radiance with the applicable

Limit.

A spectroradiometer with array detector measures all different wavelengths at the same time, no mechanical scanning is necessary. There are two different types of devices:

1-dimensional detector arrays in which the measured spectrum is projected onto a series of detectors (e.g., a photodiode array) using a grating and

2-dimensional detector arrays that allow significantly improved stray light rejection as compared to 1-dimensional detector arrays. The measured spectrum is subdivided into a set of subspectra which are separated (geometrically separated) by means of a Echelle grating and cross-dispersion Vorzerlegers on a 2-dimensional array of detectors, for example, a camera chip is projected.

The result of the measurement is a radiation spectrum that can be used to perform evaluated and unweighted radiance calculations. Radiation density and radiance dose can be measured with suitable input optics or diaphragms. Reliable results can be obtained if the radiation intensity has changed or remained constant during the measurement, provided that such measurements are within the response time of the instrument.

However, when examining the market for existing IR measuring devices, it becomes apparent that such devices are not available for the required spectral range - industrially usable devices today have a spectral sensitivity of, for example, 550-1000 nm, Si 512 / 850-1650 nm, InGaAs 256, / 850 - 1650 nm, InGaAs 512/1100 - 2100 nm, InGaAs 256/1200 - 2200 nm, InGaAs 256/1300 - 2500 nm (current product portfolio of Polytec, Waldbrunn).

No device covers the required spectral range, nor cover two devices from the spectral range. The process can not be implemented as desired. The existing semiconductor detectors must be calibrated regularly. In addition to the measuring device, the user must therefore have, as in the case of method B, an optical laboratory with suitable personnel in order to ensure the operation of this apparatus. Another disadvantage is the complex operation of such a spectroradiometer, since the cost of the measurement quickly exceed the cost of the device to be examined.

For this purpose, a laboratory operation with suitable personnel is provided for each user of the method, since such structures can be transported only with great difficulty and are to be readjusted after transport.

Rather, the measurement object is to be positioned in front of the measuring device and suitable in all spatial directions and angles to procedures - this is of course only partially solvable for larger objects, such as electric arc furnaces for steelmaking.

For the radiance in the VIS (blue light hazard), or only in IR-A (endangerment of the retina with little visual irritation), EN 14255-2: 2005 offers the same procedures as for measuring the radiance in the VIS and IR-A. Therefore, even for the implementation of these standards, there is no manageable device that can actually incorporate or implement all the characteristics mentioned in EN 14255-2: 2005. However, it is conceivable that with the use of two Spektroradiometern with array detectors and suitable optics, the measurement task can be carried out satisfactorily overall, since the devices required here are actually intended for manual operation and as directed here sizes are to be determined. The measurement must then be performed once for the range of about 380 nm to 900 nm and a second time with identical position and orientation in the spectral range from about 900 nm to 1400 nm.

From the spectra, the required quantities can then be determined by evaluating the spectral data with defined weighting functions and subsequent numerical integration. The effort to implement the proposed method remains high and costly.

A measurement of the radiance proposed in IEC 62471: 2009 is derived from the measurement of the irradiance, if suitable diaphragms are used. Especially at small angles - the standards go to 11 mrad - as sensitive as possible detectors are used.

The measurement of the radiance is not required for purely thermal radiators with low surface temperature, since the limits of the standards and directives are not reached at temperatures up to 1500 ° C. In addition, as well as when using arc discharges, in arc furnaces, in "Are" and "Flashlamps", as for example in "Flash-Iamp assisted" RTP, these measurements are necessary.

Certain radiation sources exhibit non-gray behavior. Such sources are on the one hand discharge lamps, as they are used in the flash-Iamp assisted RTP, but they can also be ceramic surfaces, which are used as emitters of infrared radiation. Examples are the IR emitters disclosed in DE 824 976 C and in DE 101 63 087 B4. For the latter, the process according to the invention which is presented below can only be implemented if the emission spectra are not known because of the lack of disclosure of the oxides used. Further IR emitters are disclosed in DE 102 17 011 A1, in which many oxides are listed without any assignment of the oxides to spectral effects, and US Pat. No. 5,447,786, in which rare-earth oxides are disclosed as selectively radiating materials - here this applies same. The state of the art thus shows that although there are proposed solutions, these are too complex for the practitioner, too unwieldy, too expensive or, in some cases, not feasible at all. A disadvantage of the prior art is therefore that the cost of implementing the proposed method is very high, the cost is very high and the proposed methods are partially not even feasible.

The object of the invention is to overcome the disadvantages of the prior art. In particular, the simplest possible, variable and well deployable under difficult conditions method and apparatus for this purpose should be provided. The task is also to provide a method that allows to determine with reasonable effort and simple device, the required data in sufficient quality to meet the requirements for the assessment of the risk emanating from such machines to comply.

The object of the invention is achieved in that the absolute spectrally integrated radiance is measured in a second wavelength range and the type of radiation source is assigned at least one correction factor with which the absolute spectrally integrated radiance is corrected in the second wavelength range, so that the corrected value of absolute spectrally integrated beam density in the second wavelength range of at least one beam density in the first wavelength range corresponds.

It can be provided that the second wavelength range comprises the at least one first wavelength range.

Furthermore, it can be provided that the type of radiation source defines the emission spectrum.

It can also be provided that at least one of the first wavelength ranges is in the infrared wavelength range, preferably the first and second wavelength ranges are in the infrared wavelength range.

A development of the invention provides that the corrected value of the absolute spectrally integrated radiance in the second wavelength range corresponds to the radiance in the first wavelength range with an accuracy of 50%, preferably with an accuracy of 25%, particularly preferably with an accuracy of 10%.

It can also be provided that the absolute spectrally integrated radiance in the second wavelength range is multiplied by at least one correction factor, so that the corrected Value of the absolute spectrally integrated radiance in the second wavelength range corresponds to at least one radiance in the first wavelength range.

According to a development of the method according to the invention, it can be provided that the corrected value or the corrected values of the absolute spectrally integrated radiance in the second wavelength range is output as radiance or radiance in the first wavelength range or, preferably, on a display, an expression and / or a electronic data output.

An advantageous embodiment of the method provides that the type of radiation source is determined on the basis of preset groups, with gray emitters in particular forming a group or being defined as part of a common group.

Furthermore, it can be provided that different correction factors are assigned for different first wavelength ranges, in particular for the visible spectrum from 380 nm to 700 nm (VIS) for determining the blue light hazard, for the spectrum from 380 nm to 1400 nm (VIS and IR-A). for determining the hazard of retinal burns, for the spectrum from 780 nm to 1400 nm (IR-A) for determining the risk of retinal burns, for the spectrum from 780 nm to 3000 nm (IR-A and IR-B) for determining the hazard of corneal burns and / or for the spectrum from 380 nm to 3000 nm (VIS, IR-A and IR-B) to determine the risk of skin burns.

It can also be provided that the absolute, spectrally integrated radiance is measured in a second wavelength range with a detector, which is preferably cooled with water. Water cooling allows comparable measurements even at higher beam densities.

It can be provided that the detector absorbs spectrally flat, preferably in the range between 200 nm and 20 pm, more preferably between 300 nm and 10 pm.

An inventive development of the method provides that the second wavelength range in which the absolute spectrally integrated radiance is measured, between 200 nm and 20 μητι, preferably between 300 nm and 10 pm.

It can also be provided that the radiance of the radiation source is determined in at least a first infrared wavelength range. A further embodiment of the invention can provide that the type of radiation source is determined and / or input or the correction factor is input.

Particularly advantageous methods may be distinguished by the fact that, depending on the correction factor, the measured absolute spectrally integrated radiance in the second wavelength range and the at least one first wavelength range, a signal is generated which indicates whether a limit value is exceeded with respect to the at least one first wavelength range.

It can also be provided that a measuring device which is used to measure the absolute spectrally integrated radiance in the second wavelength range is calibrated before the measurement.

Methods according to the invention can also be characterized in that a measuring device which is used to measure the absolute spectrally integrated radiance in the second wavelength range is aligned for the measurement with respect to the radiation source.

It can also be provided that in the measurement of the absolute spectrally integrated radiance in the second wavelength range, the measuring device used to measure the absolute spectrally integrated radiance in the second wavelength range is aligned differently with the radiant source, preferably the maximum measured value for calculating the radiance is used in the first wavelength range.

Inventive methods for determining safety-relevant emissions of infrared irradiation devices can also provide that the required quantities are measured with a device provided for this purpose, in particular the relevant temperature which determines the thermal spectrum is determined and the intensities are determined on the basis of attached tables.

The object of the invention is also achieved by a device for determining the radiance of a radiation source in at least a first wavelength range with such a method, wherein the device comprises a detector which measures the absolute spectrally integrated radiance in a second wavelength range, comprising a memory unit the at least one correction factor is stored, comprising a computing unit with which the radiance of the radiation source in the at least one first wavelength range from the absolute spectrally integrated radiance in the second wavelength range with the Korrek- is calculatable and comprises an output device, via which the result of the calculation can be output and / or displayed.

It can be provided that the detector comprises a thermocouple or a plurality of thermocouples, which absorb the radiation in the second wavelength range during the measurement.

Devices according to the invention can also be characterized in that a reflector is arranged in front of the detector, which reflects radiation from the radiation source onto the detector.

Furthermore, it can be provided that the detector and preferably also the reflector is connected to a cooling device or are, in particular to a water cooling.

A further embodiment of the invention provides that the device comprises an input device with which the type of radiation source can be input and that a correction factor is assigned to each type of radiation source.

Finally, provision can be made for different correction factors to be stored in the memory for different first wavelength ranges, in particular for the visible spectrum from 380 nm to 700 nm (VIS) for determining blue light hazard, for the spectrum from 380 nm to 1400 nm (VIS and IR). A) for the determination of the risk of retinal burns, for the spectrum from 780 nm to 1400 nm (IR-A) for the determination of the risk of retinal burns, for the spectrum from 780 nm to 3000 nm (IR-A and IR-B) for detection the endangerment of corneal burns and / or for the spectrum from 380 nm to 3000 nm (VIS, IR-A and IR-B) to determine the risk of skin burns.

The invention is based on the surprising finding that the measuring method and the apparatus are not adapted to the spectral range in order to carry out the measurement directly in the desired range, but the entire spectrum is measured in order to determine the radiance in the desired range when the radiation source is known Wavelength range to calculate. This considerably simplifies the method and the device, so that it is even possible to use it even under difficult industrial conditions. In addition, a single method or a single device is sufficient to determine the different beam densities in the most varied wavelength ranges. If the provisions for the regulations change, new correction factors and possibly new limit values can simply be used, or in the memory of the device instead of consuming the filters and using expensive new filters. The invention thus provides a simple universal measuring device. The basic nature of the radiation source is usually well known or can be determined beforehand under laboratory conditions.

An essential inventive idea is therefore to completely dispense with the complex spectrally resolved measurement and instead to perform a complete and good measurement of spectrally integrated information in reverse. This is technically possible with components available today in an industrial environment without requiring additional laboratory operation, and without the measurement becoming more expensive than the device to be measured.

A method according to the invention therefore makes it possible to record as many relevant data as possible by means of a measurement, to evaluate the data directly by means of a few previously determined values and properties of the system to be evaluated by comparison with tables and thus to perform the measuring task directly, on site and quickly and inexpensively , For this purpose, a cost-effective measuring device is proposed, which does not have to be operated by specialists and which provides the required tables for general cases.

In the following, embodiments of the invention will be explained with reference to five diagrams, without, however, limiting the invention. Showing:

FIG. 1 shows a diagram of the emitted radiant power evaluated with the spectral weighting (for thermal damage) as a function of the temperature of a gray radiator;

Figure 2 is a graph of the proportion of the weighted radiance in the specified wavelength bands in the total radiance of a gray radiator, ie the correction factor.

FIG. 3: a diagram of the relative spectral sensitivity of the eye for the day after CIE and the transmission of a filter;

FIG. 4 shows a diagram of the emitted radiation power, evaluated with the spectral weighting (for thermal damage) and reduced by the filter function from FIG. 3, as a function of the temperature of a gray radiator; and FIG. 5 shows a diagram of the correction factors for determining the radiance for the specified spectral ranges from the total measured spectrally integrated radiance for filtered radiation according to FIG. 3.

For the range of visible light deep into the infrared range (IR), for example, thermocouples are suitable, which absorb the radiation as heat, and whose temperature is a direct measure of the recorded radiation power and thus for the irradiance. The electromagnetic radiation is absorbed by the sensor and converted into heat, which is then measured by the thermocouples as a temperature. The thermocouples thus measure the absolute spectrally integrated irradiance of a radiation source over a large wavelength range. The thermocouples or the sensor can be coated with a black layer that absorbs as much electromagnetic radiation and converts it into heat. Depending on the expected radiation power, suitable thermocouples may be used, for example platinum-rhodium / platinum thermocouples (type S) may be used at high temperatures, while iron-copper / nickel (type J) or for medium irradiance nickel may be used for radiation sources with lower irradiance -Chrom / nickel (type K) sufficient and can be used.

So that the thermocouples are in a defined thermal state and the measurement is not falsified by other heat sources or heat sinks, a water cooling is provided, which cools the detector. A strong cooling capacity of the water cooling is advantageous, since it is then ensured that the heat flows from the thermocouples into the detector remain the same regardless of other heat flows and thus the individual measurements are well comparable.

On the front of the detector screens are provided which specify the detection angle of the measuring apparatus. The water cooling also extends through the apertures and thus keeps their temperature constant. As a result, the thermocouples are shielded from disturbing heat flows from the direction of the aperture.

The detector further comprises a computing and storage unit and a display. The computing and storage unit is an electronic computer with an electronic memory, as these are available as commercially available integrated circuits or as a computer. In the storage unit, different correction factors are available for different types of radiation sources 0% to 100%, or from 0 to 1, respectively, with which the absolute spectrally integrated radiant intensity measured with the sensor is multiplied by the spectrally weighted effective radiant intensity generated by a radiation source and incident at a certain angular extent to calculate a desired spectral range. The calculation takes place in the arithmetic unit.

The arithmetic unit displays the result on the display so that it can be read by a user of the device. On the display, a time average and the current values of the weighted radiance of a radiation source can be displayed. In addition, the display can also display the wavelength range to which the value of the radiance of a radiation source refers. Finally, a limit can be displayed. It is advantageous if a colored coding or additional characters on the display shows whether the limit value has been adhered to well (green numbers), the measured value is close to the limit value (yellow numbers) or the measured value exceeds the limit value (red numbers ), or which class corresponds to the measured value. As a display, a simple LCD display can be used, which is controlled by the arithmetic unit. The type of radiation source can be selected via an input device (not shown), for example a keyboard or also via a wheel for scrolling, from different types of radiation sources, which are displayed on the display, before the actual measurement.

For the measurement, the device is aligned with the aperture for beam limitation in the direction of a radiation source, so that a radiating surface element of the radiation source is located above the opening of the reflector. The emanating from the surface element electromagnetic radiation falls partly through the aperture directly on the thermocouples.

The thermocouples absorb some of the electromagnetic radiation and heat up. The heat generated is largely dissipated via the water cooling.

This very quickly establishes a balance between the heat supplied by the electromagnetic radiation and the heat dissipated by the water cooling. This balance depends on the structure of the device, but is also a measure of the recorded radiance. The influence of the structure of the device can be eliminated via a calibration stored in the arithmetic unit.

Different radiation sources have different radiation characteristics for different wavelength ranges. Typical examples are gray emitters, which behave like black emitters in accordance with Planck's law of radiation, whereby the emissivity indicates how exactly the gray emitter of the radiation characteristic of the black emitter equivalent. Since with gray emitters the different wavelengths are all equally influenced, the emissivity for the present measurement of the irradiance of a radiation source is irrelevant, so that for all gray emitters in particular only a temperature-dependent correction factor can be used. For radiation sources with a different radiation characteristic, such as band radiators, other correction factors must be stored in the memory.

The correction factors can be determined by once (already at the manufacturer of the device or at the user) by spectroscopic method, the entire spectrum of such a radiation source is recorded. Subsequently, the ratio of the total irradiance in the spectrum absorbed by the thermocouples to the irradiance in the desired wavelength range is formed. This quotient is the correction factor.

For devices for measuring the radiance in the wavelength ranges VIS + IR-A and IR-A, the total, angle-independent irradiation. For this purpose, a suitable spectrally broadband absorbing detector is used.

Here, preferably a spectrally flat thermopile detector (with thermocouples) can be used which absorbs at least spectrally flat at least in the range 380 nm to 10 μm, preferred are those detectors which absorb spectrally flat in the range from 200 nm to 20 μm.

This is modified by the required apertures to limit the angular extent under which measurements are taken - details in IEC 62471:

This device can now measure the total radiance

20000nm

= 200nm, whereby for relevant radiation sources the measured value is only insignificantly lower (1 to 10%) than

0 The water cooling diaphragms are essential so that they do not influence the measuring result of the detector due to their own thermal load. The detector itself is also provided with cooling due to the possible high radiation load.

Such a detector, for example, also complies with the requirements of IEC 62471, but without allowing spectrally resolved measurements.

FIG. 1 shows in a diagram the irradiance already evaluated with the spectral weighting as a function of the temperature of a gray radiator in different normalized, fixed wavelength ranges,

L _R = R (Ä) CÄÄ L (Ä) R (Ä) AÄ

which are typically to be determined to meet certain standards or regulations.

Particularly relevant measurements according to 2006/25 / EC and IEC 62471: 2008 concerning infrared electric heating systems

3. the determination of the risk of retinal combustion in the range of 780 nm to 1400 nm (IR-A) for sources with a weak visual stimulus.

FIG. 2 shows the proportion of the already spectrally weighted radiance of a gray radiator, which is radiated in the relevant wavelength ranges as a function of the temperature, relative to the irradiance of the gray radiator in the entire spectrum. If the absorbed electromagnetic radiation is detected over a large wavelength range, as is the case with the use of thermocouples, and the measurement at temperature Turen the radiation-emitting source of 100 ° C to 3000 ° C takes place, as is usually the case in industrial processes, the proportion of not absorbed by the sensor irradiance is very small and thus negligible. The proportion of Figure 2 can then be used as a correction factor. If necessary, this missing part can also be taken into account in the correction factor.

The following are general examples of various devices / measuring devices according to the invention. Measuring device for effective radiance in VIS + IR-A and IR-A. It is the entire angle-dependent, or over a defined angle range occurring radiation needed. For this purpose, a broadband detecting detector is used together with a device which generates the required angular resolution by means of water-cooled diaphragms.

Carrying out the measurement:

1. Calibrate the meter so that it indicates the irradiance in W / m ² . Since no adjustment is necessary, if aging of the surfaces is prevented, it can be externally calibrated at usual intervals.

2. The apertures are arranged so that they capture the angular extent of the considered source. For this purpose, they must be set between the normatively set limits.

3. Measure by aligning the meter at all points to be rated to measure the maximum intensity. These values are documented.

4. In addition, required geometric data are measured or determined. For the

Measuring task are the spotlights visible from the measuring position, or sources and their temperature relevant to the detector. For the normative task position, distance and angular orientation of the sources are to be documented.

5. In addition, data for the spectral information is to be included. This is the temperature of the considered source for thermal emitters for each spot. In the case of band radiators or thermal radiation that passes through a filter, suitable data must be recorded to characterize these elements.

6. Subsequently, the measured values can be converted into the required beam densities by means of the diagrams according to FIGS. 1 to 5 or by means of tables. 6. These values can then be used to carry out the risk assessment in accordance with the valid standard or guideline.

The presented method yields measured values that represent an absolute spectrally integrated radiance. From these measured values, the relevant variable integrated over a specific spectral range should be determined as simply as possible. This can be done with knowledge of the emission spectrum using tables or diagrams. In the following, this is explained for special cases.

For the nomenclature of the spectral emission and the relationships cited here reference is made to the literature.

1st example, gray thermal radiator:

This is by far the most technically relevant form of the infrared radiation source. The classic infrared radiators with a heating element made of tungsten, carbon, silicon carbide, a high-alloy steel, such as Inconel, Kanthai, Nikrothal, but also of molybdenum disilicide, be it electrically heated, or heated as a jet pipe with natural gas, can all be used as gray radiators to a very good approximation be accepted. The usual secondary radiant materials, such as ceramic linings, chamottes, insulating mats, but also temperature-resistant steels can be considered in good approximation as gray emitters.

In this case, the emission spectrum of a surface element is determined only by its temperature.

The emitted radiation power of a surface element can in each case be determined directly from the diagrams for the individual spectral ranges shown in FIG. 3, in which the numerical value associated with the temperature is multiplied by the emissivity of the surface element.

The radiance of a particular spectral band can be determined by multiplying the measured radiance by the correction factor for that spectral band and for the temperature of the emission source, reading the correction factor from FIG.

The tables can be determined directly under the assumption of gray radiators by (numerical) integration of the wavelength and temperature-dependent emission calculable from Planck's formula over the respective spectral ranges. 2nd example, band emission:

The method is identical to that of the previous example, however, new tables must be determined, in the evaluation of Planck's formula in each case the wavelength and temperature-dependent emissivity of the radiation source is taken into account.

For radiation sources that exhibit non-gray behavior, the spectral distribution of the emission of the radiation source must be taken into account when preparing the tables and diagrams for the measurement procedure presented here. Such sources are on the one hand discharge lamps, as they are used in the flash-assisted RTP, but they can also be ceramic surfaces that are used as emitters of infrared radiation.

However, the emission spectra must be determined only once, or if the emission of the surface depends on the temperature, also at different temperatures. However, this can be done under laboratory conditions.

Then the measured emissivities for weighing Planck's formula are used as sources for sources and the correction factors for weighting the measurement results are again obtained by numerical integration.

For plasma sources, the measured spectra can be used directly as a basis for numerical integration over the required spectral ranges.

3rd example, filters:

In the case of filters which influence the radiation, the method according to the invention can be used when the spectral transmission of the filter has been previously determined and the filter itself does not contribute to the emission, ie it is sufficiently cool or only in IR-B or IR. C emitted. For this purpose, the spectral transmission of the filter can be determined once for example by means of Fourier transform spectroscopy.

In addition, for dielectric filters, a suitable weighting function must be determined, which evaluates the variation in absorbance at different angles under the radiation passing through the filter onto the meter. With predominantly perpendicular transmission, this function is almost equal to 1. Then the Planck formula is evaluated and weighted with the spectral absorption of the filter before the numerical integration for the spectral regions takes place.

FIG. 3 shows the relative spectral sensitivity of the eye for daytime vision according to CIE and the transmission of a filter. As a filter for so-called anti-glare infrared radiators are often used gold-based chandelier coatings, these have their significant absorption in the VIS and have in the infrared in IR-A and IR-B only a small absorption. The absorption in the IR-C is due to the quartz glass as a carrier material.

The emission strengths of the individual spectral ranges, weighted with the filter function and weighted with the spectral weighting function, are shown in FIG. FIG. 5 shows the correction factors required for determining the radiance for the specified spectral ranges from the total measured spectrally integrated radiance.

All of these methods according to the invention, which cover virtually every technically relevant form, are inherent in that the additional expenditure required for the generation of the tables or diagrams has to be performed only once.

The correction factors determined therefrom for the individual spectral bands can also be stored directly in the evaluation unit for further automation of the measurement, so that the required value is displayed directly. However, since several values are required for one measured value, it is more advantageous to carry this out subsequently.

The features of the invention disclosed in the foregoing description, as well as the claims, figures and embodiments may be essential both individually and in any combination for the realization of the invention in its various embodiments.

Claims

claims

1. A method for determining the radiance of a radiation source in at least a first wavelength range, characterized in that

the absolute spectrally integrated radiance is measured in a second wavelength range and

the type of radiation source is assigned at least one correction factor, with which the absolute spectrally integrated radiance is corrected in the second wavelength range, so that the corrected value of the absolute spectrally integrated radiance in the second wavelength range of the at least one radiance corresponds to the first wavelength range.

2. The method according to claim 1, characterized in that

the second wavelength range encompasses the at least one first wavelength range.

3. The method according to claim 1 or 2, characterized in that

the type of radiation source defines the emission spectrum.

4. The method according to any one of the preceding claims, characterized in that at least one of the first wavelength ranges in the infrared wavelength range, preferably the first and the second wavelength range in the infrared wavelength range.

5. The method according to any one of the preceding claims, characterized in that the corrected value of the absolute spectrally integrated radiance in the second wavelength range of the radiance in the first wavelength range with an accuracy of 50%, preferably with an accuracy of 25%, particularly preferably with an accuracy of 10% corresponds.

6. The method according to any one of the preceding claims, characterized in that the absolute spectrally integrated radiance in the second wavelength range is multiplied by at least one correction factor, so that the corrected value of the absolute spectrally integrated beam density in the second wavelength range corresponds to at least one beam density in the first wavelength range.

7. Method according to one of the preceding claims, characterized in that the corrected value or the corrected values of the absolute spectrally integrated radiance in the second wavelength range are output as radiance or radiances in the first wavelength range, preferably on a display device, an expression and / or via an electronic data output.

8. The method according to any one of the preceding claims, characterized in that the type of radiation source is determined by means of preset groups, in particular gray emitters form a group or be defined as part of a common group.

9. The method according to any one of the preceding claims, characterized in that for different first wavelength ranges different correction factors are assigned, in particular for the visible spectrum from 380 nm to 700 nm (VIS) to determine the blue light hazard, for the spectrum from 380 nm to 1400 nm (VIS and IR-A) for determining the risk of retinal burns, for the spectrum from 780 nm to 1400 nm (IR-A) to determine the risk of retinal burns, for the spectrum from 780 nm to 3000 nm (IR-A and IR -B) for determining the risk of corneal burns and / or for the spectrum of 380 nm to 3000 nm (VIS, IR-A and IR-B) to determine the risk of skin burns.

10. The method according to any one of the preceding claims, characterized in that the absolute spectrally integrated radiance is measured in a second wavelength range with a detector, which is preferably cooled with water.

1 1. A method according to claim 10, characterized in that

the detector absorbs spectrally flat, preferably in the range between 200 nm and 20 μητι, more preferably between 300 nm and 10 μητ

12. The method according to any one of the preceding claims, characterized in that the second wavelength range in which the absolute spectrally integrated radiance is measured is between 200 nm and 20 pm, preferably between 300 nm and 10 pm.

13. The method according to any one of the preceding claims, characterized in that the radiance of the radiation source is determined in at least a first infrared wavelength range.

14. The method according to any one of the preceding claims, characterized in that the type of radiation source is determined and / or input or the correction factor is entered.

15. The method according to any one of the preceding claims, characterized in that depending on the correction factor, the measured absolute spectrally integrated radiance in the second wavelength range and the at least one first wavelength range, a signal is generated which indicates whether a limit based on the at least one first wavelength range is exceeded.

16. The method according to any one of the preceding claims, characterized in that a measuring device which is used to measure the absolute spectrally integrated radiance in the second wavelength range is calibrated prior to the measurement.

17. The method according to any one of the preceding claims, characterized in that a measuring device, which is used for measuring the absolute spectrally integrated radiance in the second wavelength range, is aligned for the measurement with respect to the radiation source.

18. The method according to claim 17, characterized in that

when measuring the absolute spectrally integrated radiance in the second wavelength range, the measuring device used to measure the absolute spectrally integrated radiance in the second wavelength range is aligned differently from the radiant source, preferably using the maximum measured value to calculate the radiance in the first wavelength range.

19. An apparatus for determining the radiance of a radiation source in at least a first wavelength range with a method according to one of the preceding claims, characterized in that

the apparatus comprises a detector which measures the absolute spectrally integrated radiance in a second wavelength range, comprises a memory unit in which at least one correction factor is stored, a computation unit with which the radiance of the radiation source of the absolute spectrally integrated radiance in the second wavelength range the at least one first wavelength range can be calculated with the correction factor, and an output device via which the result of the calculation can be output and / or displayed.

20. The apparatus according to claim 19, characterized in that

the detector comprises a thermocouple or a plurality of thermocouples that absorb the radiation in the second wavelength range during the measurement.

21. Device according to one of claims 19 to 21, characterized in that

the detector is or are connected to a cooling device, in particular to a water cooling.

22. Device according to one of claims 19 to 22, characterized in that

the device comprises an input device with which the type of radiation source can be input and that a correction factor is assigned to each type of radiation source.

23. Device according to one of claims 19 to 23, characterized in that

for different first wavelength ranges different correction factors are stored in the memory, in particular for the visible spectrum from 380 nm to 700 nm (VIS) to determine the blue light hazard, for the spectrum from 380 nm to 1400 nm (VIS and IR-A) to determine the hazard of retinal burns, for the spectrum from 780 nm to 1400 nm (IR-A) for the determination of the risk of retinal burns, for the spectrum from 780 nm to 3000 nm (IR-A and IR-B) for the determination of the risk of corneal burns and / or for the spectrum from 380 nm to 3000 nm (VIS, IR-A and IR-B) to determine the risk of skin burns.