WO2007147493A1

WO2007147493A1 - Test light source

Info

Publication number: WO2007147493A1
Application number: PCT/EP2007/005108
Authority: WO
Inventors: Lothar Nofer
Original assignee: Berthold Detection Systems Gmbh
Priority date: 2006-06-22
Filing date: 2007-06-09
Publication date: 2007-12-27

Abstract

The invention describes an apparatus for emitting light of a particular intensity, said apparatus having a light source, having a light transmitter which is assigned to the light source and into which the light source radiates light, and having at least one window through which part of the light radiated into the light transmitter emerges again. The invention provides for the light transmitter to comprise a material which scatters the light that has been radiated in.

Description

Test light source

The invention is based on a device having the features specified in the preamble of claim 1. Such a device is known from US 6,335,997. It has an electronically stabilized light source and a number of optical fibers or fiber optic bundles which are spaced apart. Light from the stabilized light source is transmitted to the optical fibers via their lateral surfaces. Part of the light is emitted by the optical fibers or optical fiber bundles again via their lateral surface. The end portions of the optical fibers or fiber optic bundles stuck covered in tunnels. From one end, a tubular casing, which consists of opaque material, is pushed onto the optical fibers or onto the optical fiber bundle. The different optical fibers or fiber optic bundles wear hose sleeves of different lengths. The optical fibers or fiber optic bundles absorb different amounts of light, and indeed the less, the shorter their length is from the tubular casing. Above the end section, which is not covered by a tubular casing, the tunnels each have a window through which light which exits through the lateral surface of the optical fiber passes through and can be observed. By adjusting the length of the tube sections, it is possible to form surface light sources with different intensities.

Such light sources are needed to verify the temporal stability of photometers, especially those used to determine the intensity of the light emitting samples in which chemical or biological luminescence reactions or fluorescence reactions occur. Such light sources can have extremely low light intensities. In some cases, individual photons are measured with the help of photomultipliers.

In order to be able to check the stability of light measuring devices (luminometers), test light sources are required which, on the one hand, can generate correspondingly low light intensities and, on the other hand, are stable with regard to their intensity and their spectrum over a longer period of time, if possible over several years.

The reproducibility and reliability of photometers for bioanalytics are set high standards not least due to legal regulations. The test light sources must meet the same high standards. Since the sources of light in bioanalytics are generally liquid samples in cuvettes which radiate the light isotropically over a surface which is usually circular in shape, it is desirable to have test light sources which have the same extent as possible and an isotropic radiation behavior which is as consistent as possible as the light-emitting samples show.

The known from US 6,335,997 B1 device does not meet these requirements to the desired extent and is also relatively expensive to manufacture.

Also known and mentioned in US Pat. No. 6,335,997 are radioactively driven light sources. However, even if they are very weak, these are extremely expensive to handle due to legal regulations for transport as well as for import and export. Samples of a microplate format as desired for bioanalytics is difficult to seal in accordance with legal requirements due to their size and geometric conditions.

Furthermore, test light sources are known which have a plurality of individually controlled light-emitting diodes (LEDs), which are arranged in bores of a plate and radiate directly vertically upwards. These test light sources do not radiate isotropically. In addition, it is extremely difficult to stabilize the light intensity of LEDs at the desired low intensities. Furthermore, LEDs have the disadvantage that their optical geometry and their radiation behavior is very different from that of a liquid sample of bioanalytics.

The present invention has for its object to provide a device which is suitable as a test light source for light measuring devices, which are to be used to determine the light intensity of samples in which chemical or biological see luminescence and fluorescence reactions take place. The device should not have the aforementioned disadvantages and in particular show a radiation behavior that comes as close as possible to the radiation behavior of liquid luminescent or fluorescent samples. In addition, the device should be inexpensive to manufacture and easy to handle.

This object is achieved by a device having the features specified in claim 1. Advantageous developments of the invention are the subject of the dependent claims.

The device according to the invention has a stabilized light source, a light transmitter associated with the light source, in which the stabilized light source emits light and at least one window through which a part of the incident light exits again. The light transmitter is formed from a material which scatters the incident light. Materials which diffuse incident light are referred to as translucent or opaque, in contrast to opaque material and unlike transparent material.

The invention has significant advantages: The light passing through the window conveys the image of a diffuse, flat light source, comparable to the surface of a liquid sample which fluoresces or luminesces.

• The shape and size of the window can be adapted to the shape and size of typical fluorescent or luminescent samples.

• The light emerging from the window is largely isotropic due to the scattering in the light transmitter. This property also corresponds to the behavior of a luminescent or fluorescent sample.

• The light transmitter has a certain thickness or depth. The scattering of the radiated light takes place everywhere in the opaque material. Every point of the material on which a photon is scattered is apparently a source of the photon. The photons leaving the window come from different depths of the light transmitter. Also in this respect, the behavior of the opaque light transmitter corresponds to the behavior of a sample of a luminescent or phosphorescent liquid.

• The light transmitter can be a simple solid, z. As a frosted glass or a milky acrylic glass. The scattering property can be achieved by admixing a turbid substance, in frosted glass z. For example, by admixing phosphoric lime, fluorides, tin oxide, titanium dioxide or of cryolite, titanium dioxide is also a suitable cloudy admixture in the case of acrylic glass. By their nature, frosted glass and opaque acrylic glass are sufficiently resistant and have long-term stability, low cost and easy care. Acrylic glass is also particularly easy to machine mechanically and particularly well suited for the purposes of the invention. • The intensity of the light source can be adjusted in different ways:

On the one hand by electronic control of the stabilized light source and on the other hand by diaphragms and by the removal of the at least one window from the stabilized light source. The greater the distance of the window from the stabilized light source, the greater are the losses due to scattering and absorption of the light before it reaches the window.

In the simplest case, the device has only a single window. In this case, the light transmitter is preferably rod-shaped. At the rear end of the rod-shaped light transmitter, the stabilized light source can be arranged and the use the light-emitting surface lying opposite the front end of the rod-shaped light transmitter as a window. The light exit surface at the front end of the light transmitter can be a flat surface, but can advantageously also be a spherical surface, which promotes an isotropic intensity distribution of the exiting light and simulates the geometry of the usual sample vessels.

By choosing the length of the rod-shaped light transmitter and the density of the scattering pigments, the intensity of the exiting light can be adjusted.

Preferably, the rod-shaped light transmitter has a cylindrical outer surface. The lateral surface is preferably covered by a light-impermeable jacket, in particular by a gray or black jacket. On the one hand, it can weaken the light as desired and, on the other hand, form a sharper border for the light exit surface. In an advantageous embodiment of the invention, the jacket is part of a rod-shaped housing, which on the one hand receives the stabilized light source and the light transmitter and on the other hand - in the rear portion of the housing - receives an electronic stabilization circuit for the light source. The stabilization circuit preferably contains as a power source a battery which, when it is running low, can be easily replaced. At the rear end of the housing, a power button can be arranged with which the light source can be easily switched on and off.

As a light source is particularly suitable a light emitting diode whose color can be selected according to the purpose. Preference is given to light-emitting diodes which emit green or blue light.

In an advantageous embodiment of the invention is located between the stabilized light source and the light transmitter nor a diaphragm and / or a screen with which not only the intensity of the light entering the light transmitter, are selectively weakened, but also can be prevented that light comes straight from the light source to the window; rather, an aperture ensures that only stray light reaches the window. In a particularly preferred embodiment of the invention, the light transmitter is a plate which has two facing in opposite directions surfaces and an edge surface connecting them. Preferably, it is a flat, rectangular plate. At least one of the two large surfaces of the plate has at least one window arranged thereon, and the light source is associated with the plate so that the light from the light source can not reach the at least one window in a straight line, but only after it has been scattered that diffuse diffused light emerges from the window. The particular advantage of the plate is that several windows can be arranged on it and that they can be arranged and configured in such a way that conditions as present in bioanalysis when examining luminescent or fluorescent samples can be simulated particularly well , In bioanalytics, the samples are usually in cylindrical or conical recesses of a rectangular sample carrier plate. A typical sample carrier plate is made of plastic and contains a rectangular array of 8 x 12 wells with a diameter of about 7 mm, a so-called 96-well microplate. Also known are sample carrier plates, which have on an approximately equal area as in the 96-well microplate an array of 16 x 24 wells, which only have a diameter of about 4 mm. There are also sample carrier plates with even higher or lower density of the wells. On a plate-shaped Lichtübertrager invention can now provide windows in the same size and in the same relative arrangement, as they have the Wells on known sample carrier plates. In this case, unlike a sample support plate, it is even possible to provide the windows on both sides of the plate-shaped light transmitter, eg. B. 6 mm diameter windows on one side and 4 mm diameter windows on the other side. But you can also provide different sized windows on the same side of the plate-shaped light transmitter and z. B: form a field of 6 mm diameter windows and form another field of 4 mm diameter windows, with the windows in each field preferably arranged regularly, just as the wells are arranged on a sample support plate.

The windows can be advantageously formed by applying a mask to the plate-shaped light transmitter, z. B. imprinted or glued as a film in which the windows are formed by holes in the mask, while the mask itself is opaque. The mask is preferably colored in the same way as sample carrier plates usually may also be. Sample carrier plates usually have a white or black surface.

In bioanalytics, in addition to a sample with low light intensity or next to a blank, there is a sample with high light intensity. Intensity differences of 6 to 8 decades or even more occur in practice. There is a risk that scattered light from a strong sample will distort the result of the intensity measurement of a neighboring weak sample. This influence of a strong sample on the measurement result of a weak sample is called "crosstalk." Even such radiation conditions can be simulated with a test light source according to the invention dazzle and other obstacles, but also by providing a light source of variable intensity or - preferably - several light sources are provided which are set to different levels of light.

For simulating the radiation conditions of fluorescent or luminescent samples, it is also advantageous to provide recesses in the light transmitter at least under some windows. The depressions may be bores. Through different deep holes different filling heights can be simulated.

It is not only possible to provide several light sources in order to achieve different intensities, but also to be able to test with different colors.

The light sources are expediently associated with the edge surface of the plate-shaped light transmitter. Preferably, they are arranged in one or more recesses of the plate. In this case, the arrangement is preferably made in such a way that they radiate their light into them mainly parallel to the two large areas of the plate. This alone prevents the light from the light sources from reaching a window in a straight line; rather, it can only reach the window by scattering. An electrical circuit operating and stabilizing the light sources is preferably likewise arranged in a recess of the plate. Preferably, a battery is provided for the power supply. Also, it is preferably provided in a recess of the plate, expediently together with the electrical circuit. The device then has the overall shape of a plate, which has the advantage that it can be used as conventional sample carrier plates for testing light measuring devices.

The invention is suitable for generating light intensities over a wide range of intensities, starting with very weak intensities of the order of 100 photons per second up to intensities which are 6 to 7 orders of magnitude greater. Such intensity ranges can be produced with light-emitting diodes, if they are operated not only in the steeper region of their current-intensity characteristic in which they are usually operated for lighting purposes or signaling purposes, but if they are also operated in the lower flat part of their characteristic, in which they provide only a low intensity. In the steeper region of the characteristic, the luminous intensity is preferably kept constant by current stabilization by keeping the power consumption Rl ² constant. In the flat part of the characteristic, in the range of low intensity, preferably the voltage applied to the LED is stabilized instead.

Particularly low intensities can be realized on individual windows by providing a groove in the plate between the windows and the light source (s), which ensures greater attenuation of the light level.

To investigate the spectral sensitivity of a light meter, not only light sources with different emission spectrum can be used, but also color filters are used.

The light source used in the device may have a temperature response, that is, the light output of the light source may depend on the temperature of the light source even with stabilized power supply. This applies in particular if a light-emitting diode (LED) is used as the light source, as is preferred. Even if the LEDs are then selected to have the smallest possible temperature coefficient have the luminous efficacy, a dependence of the luminous efficacy on the temperature of the LED is present, the more the effect, the lower the current intensity, with which the LED is operated. As long as an LED is operated with a current intensity of the order of magnitude of 5 mA to 30 mA, the temperature of the LED when used according to the invention should be determined predominantly by the self-heating of the LED, so that its temperature would then be above the normal ambient temperature (room temperature). At currents below 1 mA, especially at currents below 100 μA, the self-heating of the LED is less decisive for the temperature of the LED than the ambient temperature. The LED could then be operated in a temperature range in which the temperature coefficient of the light output has a sign change. Thus, a suitable for the purposes of the invention LED, which is characterized by a relatively low temperature response, below the room temperature has a positive temperature coefficient and above the room temperature, a negative temperature coefficient, ie, that when operating the LED with a constant current, the light output below the room temperature increases with increasing temperature, reaches a maximum at room temperature and falls again as the temperature increases.

In an advantageous embodiment of the invention, the temperature response of the light source, which is supplied with an electric current, compensated by a control circuit is provided for controlling the electric current, which can access information about the dependence of the light output of the light source from the temperature of the light source, are stored in the control circuit or in a memory associated therewith, further provided is a temperature sensor responsive to the temperature of the light source, and in connection with the control circuit or as a part of the control circuit is provided an arithmetic circuit consisting of the measured temperature and From the stored information, which can be accessed by the control circuit, a control variable for the strength of the current calculated, with which the light source is fed.

When the light source is supplied with a setpoint current at a setpoint temperature, it lights up with a setpoint intensity. However, if the actual temperature of the light source deviates from the setpoint temperature, the light intensity also deviates from the setpoint intensity from. The manipulated variable for the current intensity is then calculated by the arithmetic circuit using the stored information about the dependence of the light output on the temperature of the light source so that the current intensity is changed by the control circuit so much that the light source is returned to its desired light intensity which she should have at the setpoint temperature.

The information about the luminous efficacy as a function of the temperature is preferably stored for a number of discrete temperatures, which are selected such that they cover the desired temperature range in which the device is to be operated. Intermediate values of the luminous efficiency for temperatures which lie between the discrete temperatures for which values of the luminous efficacy are stored can be determined by interpolation.

Insofar as the temperature variation of the light source does not depend, or depends only weakly, on the current intensity with which the light source is operated, it is sufficient to record the luminous efficiency curve as a function of the temperature for only a selected current intensity. However, if the temperature response is appreciably dependent upon the amount of current supplied to the light source, then the light output is preferably determined for both a number of discrete temperatures and a number of discrete currents, thus storing not just a characteristic but a map which the arithmetic circuit can access.

As the reference temperature, a temperature is preferably selected in which the light source is predominantly operated, in the case of an LED in particular the room temperature.

Preferably, an LED is selected as the light source, which has a luminous efficacy with a temperature coefficient which is positive below room temperature and negative above room temperature, so that the temperature coefficient has a maximum in the region of room temperature and runs flat there. This has the advantage that, with a choice of the reference temperature in the maximum of the temperature coefficient of the light output, smaller changes in the temperature have little effect on the luminous efficacy and larger changes in the temperature of the LED can be compensated according to the invention. For most applications of the device according to the invention, it is sufficient to determine and store the luminous efficacy for a few temperature values, for example

for 15 ° C, for the temperature, eg 22 ° C, at which the temperature coefficient changes its sign, for 27 ° C and for 32 ° C, possibly also for 37 ⁰ C, if unusually hot ambient temperatures are to be expected. With the values for the luminous efficacy for these few temperature values, it is possible to stabilize the light source well for purposes of the invention.

Light-emitting diodes of a series have production-related and unavoidable not insignificant scattering of the luminous efficacy (specimen scattering). Preferably, therefore, the information about the temperature dependence of the luminous efficiency for each individual light source is determined and stored for this in the control circuit or in the arithmetic circuit. Since you can make do with few measuring points, the effort required for this is acceptable and advisable in view of the gain in stability of the light output or light intensity of the light sources.

Embodiments of the invention are illustrated in the accompanying drawings in which like or corresponding parts are designated by like reference numerals.

FIG. 1 schematically shows a rod-shaped test light source in longitudinal section,

Figure 2 shows a plate-shaped test light source in an oblique view and

FIG. 3 shows the section A-A through the test light source shown in FIG.

Figure 1 shows a test light source with a rod-shaped housing 1, which is divided by a transverse wall 2 into two compartments. In a front compartment is a rod-shaped light transmitter 3 with a crowned tip 4, which protrudes beyond the housing 1. At the rear end of the rod-shaped light transmitter 3 is a bore. 5 provided, which extends from the rear end of the light transmitter 3 in the direction of the tip 4 and an opaque aperture 6 and behind it receives a light source 7, which is preferably an LED whose unillustrated leads through a bore 8 in the transverse wall 2 are guided in the rear compartment of the housing 1, in which - only symbolically represented - the ele- ments of an electrical circuit 9 are housed, including a battery 10 through which the circuit 9 and the LED 7 are supplied with power. The battery 10 may be interchangeable. Otherwise, the circuit may be potted. At the rear end of the housing 1, also indicated only schematically, a push-button switch 11 is provided, by the actuation of which the light source can be switched on and off.

The light transmitter 3 is preferably made of milky acrylic glass. The front edge of the housing 1 defines a window through which the light can finally escape into the tip 4 and finally out of it.

Figures 2 and 3 show a device according to the invention with a plate-shaped Lichtübertrager 3, which has two large, pointing in opposite directions surfaces 12 and 13 and an edge surface 14 connecting them. The upper surface 12 is covered by a mask 19, which is exaggerated in Figure 3 thick. The mask 19 has windows 15 formed as holes. Windows of different sizes are provided. Windows 15 of the same size are grouped into fields in which the windows 15 are arranged in a regular arrangement. Under the windows 15, the plate 3 can have depressions 16. Such recesses 16 need not be provided under all windows 15. As far as depressions 16 are provided, they can be formed differently deep.

In the vicinity of one of the edges of the plate 3 are provided in holes, which are provided in the plate 3, a plurality of juxtaposed light sources 7, in particular LEDs, which by an electrical circuit 9, which comprises a battery 10, and in a recess 17 the plate 3 is housed, operated. The light sources 7 radiate their light mainly parallel to the two surfaces 12 and 13 of the plate 3 in this one. Therefore, the light can not go straight from the light sources 7 to one of the windows 15 and exit through this, but only after scattering on scattering pigments, which are provided in the plate 3, z. B. titanium dioxide pigments in acrylic glass.

The windows 15 furthest from the light sources 7 receive the lowest light intensity. This can additionally be reduced by a slot 18 cut into the plate 3.

LIST OF REFERENCE NUMBERS:

1st case

2nd transverse wall

3. Light transmitter

4th tip

5. Bore

6. Aperture

7. Light source

8. Bore

9. circuit

10. Battery

11. Pushbutton

12. Area

13. Area

14th edge surface

15th window

16th recess

17th recess

18th slot

19. Mask

Claims

Claims:

1. A device for emitting light of a certain intensity with a light source (7), with a light source (7) associated light transmitter (3), in which the light source (7) irradiates light, and with at least one window (15) through which a part of the light in the light transmitter (3) radiated light exits again, characterized in that the light transmitter (3) consists of a light scattering the incident light material.

2. Apparatus according to claim 1, characterized in that the light transmitter (3) is rod-shaped.

3. Device according to claim 2, characterized in that the light source (7) at the rear end of the rod-shaped light transmitter (3) is arranged and that the window (15) at the opposite, front end of the rod-shaped light transmitter (3) is provided.

4. Apparatus according to claim 2 or 3, characterized in that the light exit surface of the light transmitter is formed flat in the window.

5. Apparatus according to claim 2 or 3, characterized in that the light exit surface in the window (15) of the light transmitter (3) is formed crowned.

6. Device according to one of claims 2 to 5, characterized in that the

Light transmitter (3) has a cylindrical outer surface.

7. Device according to one of claims 2 to 6, characterized in that the lateral surface of the light transmitter (3) limits the light exit surface.

8. Device according to one of claims 2 to 7, characterized in that the light transmitter (3) with an opaque jacket (1).

9. Apparatus according to claim 8, characterized in that the jacket (1) is gray or black.

10. Device according to one of claims 2 to 9, characterized in that a rod-shaped housing (1) is provided, which has a front portion in which the light transmitter (3) and the light source (7) stuck, and has a rear area in which an electrical circuit (9) for operating and stabilizing the light source (7) is provided.

11. The device according to claim 10, characterized in that for the power supply of the light source (7) and the circuit (9), a battery (10) is provided.

12. The apparatus of claim 10 or 11, characterized in that directly at the rear end or laterally at the rear end of the housing (1), a switch (11) for switching on the light source (7) is provided, in particular a push button.

13. The device according to claim 1, characterized in that the light transmitter (3) is a plate having two facing in opposite directions surfaces (12, 13) and an edge surface connecting them (14) that on at least one of the two surfaces ( 12) at least one window (15) is arranged and that the light source (7) of the plate (3) is associated so that the light from the light source (7) can not reach the at least one window (15) in a straight line.

14. The apparatus according to claim 13, characterized in that a plurality of windows (15) on at least one of the two surfaces (12) of the plate (3) are provided.

15. The device according to claim 14, characterized in that both the same size and different sized windows (15) on at least one of the two surfaces (12) of the plate (3) are provided.

16. The apparatus of claim 14 or 15, characterized in that at least some of the plurality of windows (15) are arranged regularly.

17. Device according to one of claims 13 to 16, characterized in that the windows (15) by a on the plate (3) applied mask (19) are limited.

18. Device according to one of claims 13 to 17, characterized in that the plate (3) are associated with a plurality of light sources (7).

19. The apparatus according to claim 18, characterized in that the light sources 7 () differ in color.

20. Device according to one of claims 13 to 19, characterized in that the light sources (7) of the edge surfaces (14) of the plate (3) are associated.

2 I.Vorrichtung according to one of claims 13 to 20, characterized in that the one or more light sources (7) in the plate (3) are arranged.

22. Device according to one of claims 13 to 21, characterized in that the one or more light sources (7) radiate their light mainly parallel to the two surfaces (12, 13) of the plate (3) in this.

23. Device according to one of claims 13 to 22, characterized in that one of the light sources (7) operating electrical circuit (9) in a recess (17) of the plate (3) is arranged.

24. Device according to one of claims 13 to 23, characterized in that a battery (10) for powering the one or more light sources (7) and the circuit driving them (9) is provided.

25. The apparatus according to claim 24, characterized in that the battery (10) in a recess (17) of the plate (3) is provided.

26. Device according to one of claims 13 to 25, characterized in that the plate (3) under one or more windows (15) has a recess (16).

27. The device according to claim 26, characterized in that different deep recesses (16) are provided.

28. Device according to one of claims 13 to 27, characterized in that one or more slots (18) in the plate (3) are provided.

29. Device according to one of the preceding claims, characterized in that the light source (7) is electronically stabilized.

30. Device according to one of the preceding claims, characterized in that between the light source (7) and the window (15) an aperture (6) is provided.

31. Device according to one of the preceding claims, characterized in that the light transmitter (3) is color-neutral.

32. Device according to one of the preceding claims, characterized in that the light source (7) is a light-emitting diode.

33. Device according to one of the preceding claims, characterized in that the light source (7) is supplied with an electric current, that a control circuit is provided for controlling the electric current, which is based on information about the dependence of the light output of the light source (7) the temperature of the light source (7) can be accessed, which are stored in the device, that a temperature sensor is provided, which responds to the temperature of the light source (7) and that in conjunction with the control circuit or as part of which an arithmetic circuit is provided which calculates from the measured temperature and the information stored in the device a manipulated variable for the magnitude of the current with which the light source (7) is fed, so that its luminous efficacy is stabilized against fluctuations in its temperature.

34. Apparatus according to claim 33, characterized in that the information about the light output as a function of the temperature for a number of discrete temperatures are stored.

35. Apparatus according to claim 34, characterized in that the information stored for a number of discrete temperatures on the luminous efficacy for a number of discrete currents are determined and stored.

36. Device according to one of claims 33 to 35, characterized in that the light source (7) is an LED, for which the information about the light output for

Amperages are stored below 1 mA.

37. Device according to one of claims 33 to 35, characterized in that the light source (7) is an LED, for which the information about the light output for currents below 100 uA are stored.

38. Device according to one of claims 32, 36 and 37, characterized in that the light source (7) selected LED has a luminous efficacy with a temperature coefficient, which changes its sign at room temperature.

39. Device according to one of claims 33 to 38, characterized in that the information about the temperature dependence of the light output for each individual light source (7) are determined and stored for them.