Abstract:
A fluorometer with at least one light source, a measuring station with a holder for at least one specimen, a measuring head, and an evaluation station with a detector for evaluating emission signals emitted by a specimen. The measuring head is formed by three optical blocks (A, B, C) assembled in a modular manner. A different measurement method is able to be carried out with each optical block (A, B, C). All the optical blocks (A, B, C) operate the same detector.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     The present invention claims priority of PCT Application No. PCT/AT02/00157 filed on May 23, 2002, which claims priority of Austrian Patent Application No. A818/2001, filed on May 23, 2001, the entire contents of which are hereby incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     The invention relates to a fluorometer with at least one light source, a measuring station with a receptacle for at least one specimen container, in particular for receiving microplates and polymerase chain reaction tubes (PCR tubes), a measuring head, as well as an evaluation station with a detector, preferably a photomultiplier (PMT), for evaluating the emission signals emitted by a specimen.  
         [0003]     A compact fluorometer measuring head module is known from U.S. Pat. No. 6,084,680 which can be used only for one measurement method (without modification). No time-resolved fluorometry, photometry, luminometry or polarization fluorometry can be measured with this apparatus.  
         [0004]     EP 0 886 136 A1 shows an instrument for cuvettes and for measuring flash fluorometry. The detector is blinded if the flash energy is too intense as the photosensitive layer of the detector is damaged. Two flashlamps with different energy levels are therefore used.  
         [0005]     WO 01/35079 A1 describes a fluorometer with a thermal cycler, i.e. the specimens are heated up and cooled down very intensely and rapidly. The light source is a light-emitting diode with a very limited optical spectrum and energy. This apparatus is designed for only one application.  
       SUMMARY  
       [0006]     The object of the invention is to improve a fluorometer of the type initially mentioned in order that it can be easily adapted to various requirements.  
         [0007]     The object according to the invention is achieved in that the measuring head is formed by at least two, preferably three, optical blocks assembled in a modular manner, a different measurement method being able to be carried out with each optical block and all optical blocks operating the common detector.  
         [0008]     Due to the modular assembly, devices for various measurement methods can be easily omitted or added. Only the parts needed for fluorometry read from above (top-reading fluorometry) are required for the base unit. All other parts can be added in a modular manner as required. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     An embodiment of the invention will now be described in conjunction with the attached drawings where:  
         [0010]      FIG. 1  is a front view of a fluorometer according to the invention;  
         [0011]      FIG. 2  is a top view of a fluorometer according to the invention;  
         [0012]      FIG. 3  is a diagram of the fluorometer configured for fluorometry from above and for polarization fluorometry;  
         [0013]      FIG. 4  is a diagram of the fluorometer configured for fluorometry from below;  
         [0014]      FIG. 5  is a diagram of the fluorometer configured for delayed measurement (time-resolved fluorometry);  
         [0015]      FIG. 6  is a diagram of the fluorometer configured for photometry;  
         [0016]      FIG. 7  is a diagram of the fluorometer configured as a luminometer; and  
         [0017]      FIG. 8  is a diagram of a polarization filter wheel. 
     
    
     DETAILED DESCRIPTION  
       [0018]     The basic equipment for all measurement methods consists of a detector  15  in the form of a photomultiplier PMT, optical block (B), first and second filter slides  6 ,  13  and a light source  1 . Optical block B is used for fluorometry measured from above, i.e. for top-reading fluorometry and for time-delayed fluorometry (time-resolved fluorometry). A first light source  1  ( FIG. 3, 4 ) consists of a halogen lamp with six volts and  20  watts without UV stop, two lenses  2 ,  3  made of non-fluorescent quartz glass, and a heat-protection glass  4  for the suppression of parasitic infrared radiation in a self-contained lamp block. The first light source  1  is used for fluorescence measurement from above and from below and for photometry. The first light source  1  is rigidly connected to a light guide holder  33  for a second light source  29  ( FIG. 5 ) which preferably is formed by a xenon flashlamp and has a motor drive. The light source  1  and the light guide holder  33  can thus be changed automatically.  
         [0019]     Optical block B ( FIG. 5 ) has a supporting block made of black-anodized aluminum in which a diaphragm  7  ( FIG. 3 ) for limiting marginal rays is arranged, as well as a broadband beam splitter  8  arranged at an angle of 45° to the light sources  1 ,  33  or to the specimen  11 . Through this arrangement of the broadband beam splitter  8 , the excitation light is diverted to the specimen and the returning fluorescence light is forwarded from the specimen  11  to the detector  15 . Also provided are an output lens  9  made of non-fluorescent quartz glass (SQ  1 ) which focuses the beam to and from the specimen  11 , a photodiode  16  for synchronizing a flash emitted by a flashlamp of the second light source  29 , and optionally for monitoring the halogen lamp, as well as a lens  12  (SQ 1 ) which guides a return beam from the specimen  11  to the detector  15  through an emission filter  13 , which is formed by a filter slide  13 .  
         [0020]     Attention must be paid in particular to freedom from reflection in the region of the photodiode  16 . The photodiode  16  is mounted diagonally to the light beam to prevent a retroreflection. The area surrounding the photodiode  16  is kept matte black, as otherwise the sensitivity is reduced. Optical blocks A, B, and C are rigidly connected to each other and can be selected with a motor drive.  
         [0021]     Optical block A ( FIG. 4 ) is used for fluorometry measurement from below. Like optical block B, optical block A has a supporting block made from black-anodized aluminum which is rigidly connected to the supporting block of optical block B. The coupling optic SO 1  in turn has a distance of 18 mm to SO 2  or from the upper measuring head and serves to couple and decouple the light guide  19 . The coupling takes place in each case via a lens  22 ,  17 ,  20  (SQ  1 ) in order to focus the beam on the light guide entry area. The distance of 18 mm was chosen in order to have a uniform grid, as the grid spacing for microplates with  96  cavities is  9  mm and a better timing for all the various measurement methods is facilitated by uniform distances. The time slot pattern for many measurements is very important, e.g. fluorometry measured from above can be carried out with injection in the same time slot pattern (injection to measurement) as fluorometry measured from below. The geometric misalignment (18 mm) of the two optics for measurement from above and from below also prevents a reciprocal influencing of the optics. Aluminum surface mirrors  18 ,  21  serve to deflect the light beam by 90°, whereby a very compact structure is achieved, which is needed in order to have injection positions in the immediate vicinity which are required for time-critical measurement methods.  
         [0022]     Optical block C ( FIG. 6 ) is used for photometry, glow luminescence, and flash luminescence. Optical block C also has a supporting block made from black-anodized aluminum rigidly connected to the supporting block of optical block B. The coupling of the light beam for photometry takes place exactly as in optical block A, via the lens  23  and the mirror  24  into the light guide  25 .  
         [0023]     In the case of luminescence measurement and photometry, as shown in  FIG. 7 , the light beam from the specimen  11  is forwarded via a quartz light guide rod  28  to keep the losses for luminometry as small as possible. From the output of the quartz light guide rod  28 , the light beam either travels directly to the detector  15  or via a filter slide  13  to the detector  15 . The filter slide  13  is provided for wavelength-specific luminescence measurements or photometer measurements.  
         [0024]     The second light source  29  ( FIG. 5 ) consists of a xenon flashlamp together with a trigger mechanism, a liquid light guide  30 , which among other things serves to geometrically stabilize the flash, the light guide holder  33  made of black-anodized aluminum, and an uncoupling optic formed by a lens  31 .  
         [0025]     The light sources  1 ,  29 , i.e. the halogen lamp and the xenon flashlamp, are each positioned according to the measurement method. The distance between the two uncoupling optics of the light source  1  and the light guide holder  33  is 18 mm. The positioning of the light source  1  and the light guide holder  33  is carried out by means of a stepping motor. A guide made of black-anodized aluminum with a 9 mm (10 mm) optic opening is provided for the separation between the light source  1  and the light guide holder  33 , and the filters.  
         [0026]     The EM filters (fluorometry emission filters) for time resolved fluorometry and flash luminescence, the polarization filters  5 , and the photometer filters can be installed in the first filter slide  6 . The first filter slide  6  is easily removable and the filters can easily be refitted (filter sizes approx. 12.7 mm). The first filter slide  6  is driven by a stepping motor. The filters are arranged in a grid spacing of 18 mm.  
         [0027]     Additionally, the EM filters for time resolved fluorometry and flash luminescence, the photometer filters and the luminescence filters can be installed in the second filter side  13 . Like the first filter slide  6 , the second filter slide  13  is easily removable, in order that the filters can be easily refitted. The filter size is again approx. 12.7 mm. The second filter slide  13  is driven by a stepping motor and the individual filters are arranged in a grid spacing of 18 mm. The first and second filter slides  6 ,  13  are mechanically coded to prevent confusion.  
         [0028]     The detector  15  is a high-speed front-window photon multiplier for counting modules (high-speed front-window counter) photomultiplier with optional Peltier cooling for higher sensitivity even in the red range of the spectrum. The cooling reduces the thermal-agitation noise of red-sensitive photomultipliers. A pre-amplifier counter, with approx. 500 MHz bandwidth, which can synchronize the flashlamp directly with the counter, is used as a receiver circuit. A photon multiplier which exploits the principle of the channel electron multiplier (CEM) (channel photomultiplier) can also optionally be used.  
         [0029]     An iris diaphragm  10  is continuously adjustable (typically 0.6 mm to 7 mm) by a motor. Various specimen sizes can therefore be measured without neighboring channel influence. A geometric scanning of the specimens is also possible (pattern recognition) as the specimen supporting transport has a step resolution of 0.1 mm in full step or correspondingly smaller in micro step operation as well as in the X and the Y direction.  
         [0030]     The specimen coupling optic SO 1  for fluorescence measured from below is arranged in a block made of matte black-anodized aluminum that holds the fluorometer light guide  19 . The specimen coupling optic SO 1  for fluorescence measured from below is 18 mm away from the measuring position for fluorescence measured from above in order to prevent reciprocal influencing. The fluorometer light guide  19  is twice the focal length from the lens  20 .  
         [0031]     The fluorometer light guide  19  has two optical arms, i.e. emission light guide fibers and excitation light guide fibers. The emission light guide fibers and the excitation light guide fibers are bundled in a statistical mixing ratio of 1:1. During processing, attention must be paid in particular to maximum transmission and intactness of the light guide fibers, as otherwise an increased penetration could result, and this would have a negative effect on the sensitivity of the measuring system. Furthermore, only materials which have no self-fluorescence may be used.  
         [0032]     The overall optical structure which is to be found above the specimen  11  (i.e. optical blocks A, B, C, the light sources  1  and  29 , the iris diaphragm  10 , the detector  15 , the polarization filters  5  and the filter slides  6 ,  13 ) can be adjusted to the respective specimen carrier height by means of a motor drive. This increases sensitivity and reduces the reciprocal influencing of neighboring specimens. This is particularly important in the case of glow luminescences, as the specimens can continue to glow for a very long time. Height adjustment is possible between approx. 10 mm and 25 mm of specimen height.  
         [0033]     The photometer secondary optic SO 2  ( FIG. 6 ) includes a light guide  25  which has the task of bringing light under the specimen  11 . The optic must prepare a very thin beam in order to be able to also measure even small specimens  11 . The beam travels through the light guide  25  which is arranged in a black plastic tube  26  with an internal thread. The plastic tube  26  blocks troublesome marginal rays and acts as a sequence of many diaphragms. An output lens  27  prepares the beam in such a way that good measurement results are achieved even when there is marked meniscus formation in the specimen  11 .  
         [0034]     The system can be equipped with up to four injectors (in order to start/stop etc, the reactions). It must be borne in mind that these positions are in the immediate vicinity of the measuring positions. Rapid transport of the specimen  11  from the injector position to the measuring position is absolutely necessary in the case of various measurement methods. Injector positions are in each case 18 mm away from the measuring position for measurement from above or from the measuring position for measurement from below. In each case, two injectors can be attached in each position. In the case of equipment which injects directly in the measuring position, the measuring optic is very prone to contamination.  
         [0035]     In order to measure fluorescence polarization, a polarization filter  14  ( FIG. 5 ) can optionally be integrated between the second filter slide  13  and the detector  15  developed as a photomultiplier or between optical block B and the second filter slide  13 . The polarization filter  14  can be rotated by a motor, and the polarization shift in the specimen  11  can thus be measured. The polarization filter wheel  32  ( FIG. 8 ) has a position for normal measurements ( 9  mm bore) and an arc of 90°+beam diameter, where a polarization filter  14  is inserted. Through the rotation of the polarization filter wheel, a polarization rotation of 90° can take place. The polarization filter wheel  32  is driven by a stepping motor. A back calculation of the polarization rotation is thus easily possible. Polarizing fluorescence filters or polarization filters and interference filters must be integrated in the first filter slide  6  for the measurements.  
         [0036]     The following is a description of the individual measurement methods.  FIG. 3  is a diagram of a system for measuring fluorometry from above. The first light source  1 , the first filter slide  6 , optical block B, the iris diaphragm  10 , the second filter slide  13  and the detector  15  developed as a photomultiplier are used for this measurement method. For this measurement method, the corresponding energy values for the respective filter combination can be set and checked (beginning and end of the measurement) via reference specimens which are integrated in the specimen carrier plate. This maintains better reproducibility and the ageing or the drift of the first light source  1  or other optical components such as the filter or the detector  15  can be compensated for.  
         [0037]      FIG. 5  is a diagram of a system for measuring time-resolving fluorometry. The second light source  29 , a liquid light guide  30 , a light guide holder  33 , the first filter slide  6 , optical block B, the iris diaphragm  10 , the second filter slide  13 , a reference diode  16  and the detector  15  developed as a photomultiplier are used for this measurement method. Also for this measurement method, the corresponding energy values for the respective filter combination can be set and checked via reference specimens which are integrated in the specimen carrier plate. This also results in better reproducibility and the ageing of the xenon flashlamp of the second light source  29  or other optical components, such as filter(s) and detector(s)  15 , can be compensated for. The ignition points of the second light source  29  (flashlamp) are measured with the reference photodiode and passed, synchronized via an adjustable time-resolving element, to the detector developed as a photomultiplier. The measurement window and the time-resolving window are freely programmable.  
         [0038]      FIG. 4  is a diagram of a system for measuring Fluorometry from below. The first light source  1 , the first filter slide  6 , optical block A, the fluorometer light guide  19 , the bottom-reading secondary optic SO 1 , the second filter slide  13  and the detector  15  are used for this measurement method. In this measurement method, the specimen  11  is measured from below. The corresponding energy values for the respective filter combination can be set and checked via the reference specimens which are integrated in the specimen carrier plate. This is the same procedure as is used in the case of fluorometry measurement from above.  
         [0039]      FIG. 6  is a diagram of a system for measuring Photometry. For this measurement method, the first light source  1 , the first filter slide  6  or the second filter slide  13 , optical block C, the photometer secondary optic SO 2  with the light guide  25 , and the detector  15  are used. This measurement is a so-called flash method, i.e. the specimen  11  is lit from below with a light beam and measured from above. The iris diaphragm must be open for the measurement in order that all of the light which passes through the specimen  11  is caught and no distortion of the measuring results occurs due to different meniscus formations in the specimens  11 . Lamp energy measurements are carried out at the beginning and end of each row (or column). This allows the lamp drift to be back-calculated by software and the measuring results to be improved. Furthermore, a reference channel can be dispensed with.  
         [0040]      FIG. 7  is a diagram of a system for measuring luminometry. For this measurement method, optical block C, the iris diaphragm  10 , the detector  15  developed as a photomultiplier, and preferably the second filter slide  13  are used. The specimen  11  is measured from above in this measurement. As the specimen  11  emits light for a long period in the case of different methods, it is very important to suppress cross-talk from other specimens. This is achieved by adjusting the height to the specimen  11  and by adjusting the variable iris diaphragm  10 . For special applications, special luminescence filters can be used in the second filter slide  13 .  
         [0041]     Polarization fluorometry can take place according to two methods. In a first polarization measurement method, as shown in  FIG. 3 , the first light source  1 , the filter slide  6 , optical block B, the iris diaphragm  10 , the second filter slide  13 , a first polarization filter  5 , a second polarization filter  14 , and the detector  15  are used. Also in this measurement method, the corresponding energy values for the respective filter combination can be set and checked via reference specimens which are integrated in the specimen carrier plate. This results in better reproducibility and the ageing of the lamp of the first light source  1  or other optical components such as filter(s) or detector(s)  15  can be compensated for.  
         [0042]     During integration, attention need not be paid to the precise rotation or justification of the polarization filters  5 ,  14 . Through the rotatability of the second polarization filter  14 , the 0° point (fully open) or the 90° point (fully closed) of the two polarization filters  5 ,  14  relative to each other can be discovered, and the polarization filters are thus automatically adjusted via an integrated reference specimen in the holder of the measuring specimens (plate slide) in the apparatus. During measurement, the polarization of the receiver side can be changed.  
         [0043]     In a second polarization measurement method, the second light source  29 , the filter slide  6 , optical block B, the iris diaphragm  10 , the filter slide  13 , the first polarization filter  5 , the second polarization filter  14  and the detector  15  are used. Also in the case of this measurement method, the corresponding energy values for the respective filter combination can be set and checked via reference specimens which are integrated in the specimen carrier plate. Also as in the preceding method, the polarization of the receiver side can be changed during the measurement. This method has the advantage that polarization fluorescence can also be measured in the UV range. However, the measurement is slower as no constant light is present. The second light source  29  is, as already mentioned, formed by a xenon flashlamp with a maximum of 1000 Hz.  
         [0044]     Fluorescence methods and photometer methods can also optionally be carried out with the second light source  29 , i.e. with a flashlight, which allows deep UV measurements but influences the measurement speed or the measurement accuracy (photometric DNA measurements at e.g. 260/280 NM).