Abstract:
The present invention relates generally to the field of biochemical laboratory. More particularly the invention relates to more reliable, intelligent instrumental features of equipment used as e.g. fluorometers, photometers and luminometers. The object of the invention is achieved by providing an optical measurement instrument where a selectable optical component is identified by the measurement instrument. The instrument therefore has means for identifying an optical component by e.g. reading a code from the component. The object is also achieved by a changeable/selectable optical component such as optical module or filter for a measurement instrument, the component comprising a readable identification means. The identification comprises information on the type/properties of the optical component so that the components suitability for a selected measurement can be verified.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates generally to the field of biochemical laboratory instrumentation for e.g. different applications of measuring properties of samples on e.g. microtitration plates and corresponding sample supports. More particularly the invention relates to the improved, reliable and more intelligent instrumental features of equipment used as e.g. fluorometers, photometers and luminometers. 
   DESCRIPTION OF THE RELATED ART 
   The routine work and also the research work in analytical biochemical laboratories and in clinical laboratories are often based on different tags or labels coupled on macromolecules under inspection. The typical labels used are different radioactive isotopes, enzymes, different fluorescent molecules and e.g. fluorescent chelates of rare earth metals. 
   The detection of enzyme labels can be performed by utilizing its natural biochemical function, i.e. to alter the physical properties of molecules. In enzyme immunoassays colourless substances are catalysed by enzyme to colourful substances or nonfluorescent substances to fluorescent substances. 
   The colourful substances are measured with absorption, i.e. photometric measurement. In the photometric measurement the intensity of filtered and stabilized beam is first measured without any sample and then the sample inside one plate is measured. The absorbance i.e. the absorption values are then calculated. 
   The fluorescent measurement is generally used for measuring quantities of fluorescent label substance in a sample. The most photoluminescence labels are based on molecular photoluminescence process. In this process optical radiation is absorbed by the ground state of a molecule. Due to the absorption of energy the quantum molecule rises into higher excited state. After the fast vibrational relaxation the molecule returns back to its ground state and the excess energy is released as an optical quantum. Due to losses in this process the average absorbed energies are higher than the average emitted energies. 
   A further measurement method is chemiluminescence measurement where emission of a substance is measured from a sample without excitation by illumination. Thus any photoluminometer can also be used as a chemiluminometer. 
   The typical instruments in analytical chemical research laboratories are the different spectroscopic instruments. Many of them are utilizing optical region of electromagnetic spectrum. The two common types of instruments are the spectrophotometers and the spectrofluorometers. These instruments comprise usually one or two wavelength dispersion devices, like monochromators. The dispersion devices make them capable to perform photometric and luminescence measurements throughout the optical spectrum. 
     FIG. 1  illustrates an advanced prior art optical analyser, especially the optical components and the different optical paths. The instrument has two illumination sources, a continuous wave lamp (cw-lamp)  112   a  and a pulse lamp  112   b.  The cw-lamp can be used for continuous wave photoluminescence excitation and for absorption measurements. 
   Infrared part of radiation from the cw-lamp  112   a  is absorbed by a filter  104 , and after transmitting a stray-light aperture plate  105 , the optical radiation is collimated with a lens  11     5 a  through an interference filter  114   a  located in a filter wheel  114 . 
   The light beam is focused with a lens  113   a , similar to the lens  114   a , into a light guide  118 , which isolates the measuring head thermally and mechanically. It also shields the measuring unit for the stray light from the cw-lamp. The optical radiation from an output aperture plate  106  of a light guide  118  is collimated with a lens  107 , similar to the lens  115   a . The radiation beam is reflected by a beam-splitter mirror  141  inside a mirror block  140 , and passed through a sample well  181  and through an entrance window  122  of a photometric detector unit  132 . 
   The mirror block  140  is located on the upper side of the sample. Its function is to reflect the horizontal light beam from the selected lamp downwards to the sample and to reflect a portion of this beam by a mirror  143  into a reference photodiode  119 , and also to allow the emission from the sample to travel upwards to the detector unit  132 . 
   The emission unit comprises optical components, which are lenses  133 ,  135 , a filter  134   a  in filter slide  134 , a combined shutter and aperture slide  136  and the detector unit  132 , such as a photo-multiplier. The detector unit  132  is used in the fast photon counting mode where the pulses from photo-multiplier anode are first amplified and then fed through a fast comparator  191  and gate  192  counter  193 . The comparator rejects the pulses, which are lower than the pre-adjusted reference level. The fast counting electronics is equipped with a gate in the front of the counter. This gate is used in overall timings of the measurements. 
   The pulse-lamp unit is used in time-resolved photoluminescence measurement for long-living luminescence emission. It comprises a second lamp  112   b,  lenses  115   b,    113   b,  and optical filters  114   b  in a filter slide for wavelength isolation. When this second lamp is used the mirror  141  must be rotated by 90 degrees in order to reflect the radiation to the sample. This can be achieved by using different optical modules for the two lamps. 
   There are certain limitations related to the prior art technology. When different optical modules are used for different measurements the optical module and filters are usually changed when the measurement mode is changed. As the optical components are manually handled/selected there is a risk of a human error, which may cause that a wrong filter or optical module is installed. This naturally makes the measurement results less accurate and less reliable. Especially it is not possible to verify later that correct optical components have been used in a determined measurement. A further limitation of the prior art solutions relates to the difficulty to use a large number of different measurement methods as well as to introduce new measurement methods because there is a limited number of optical filters in a filter slide, and a new method and new optical components may also require calibration of the instrument. 
   SUMMARY OF THE INVENTION 
   The object of the present invention is to provide an optical instrument for laboratory measurements, wherein the described disadvantages of the prior art are avoided or reduced. The object of the invention is therefore to achieve a measurement instrument with reliability and/or efficiency for performing measurements from samples. 
   The object of the invention is achieved by providing an optical measurement instrument where an optical component is identified by the measurement instrument. The instrument therefore has means for identifying an optical component by e.g. reading a code from the component. The object is also achieved by a changeable/selectable optical component such as optical module or filter for a measurement instrument, the component comprising a readable identification means. The identification comprises information on the type/properties of the optical component so that the components suitability for a selected measurement can be verified. 
   An optical measurement instrument according to the invention for measuring samples, comprising an illumination source for forming an excitation beam, a detector for detecting an emission beam, optical components with a purpose of directing the excitation beam received from the illumination source into the sample and/or directing an emission beam received from the sample to a detector and/or filtering the excitation and/or emission beam, is characterized in that at least one of said optical components is changeable and the instrument comprises means for identifying said at least one changeable optical component. 
   The invention also applies to a changeable optical component for an optical measurement instrument, the component comprising means for providing identification information on the optical component. 
   The invention also applies to a process for measurement of samples with an optical measurement instrument comprising at least one measurement head, possible means for providing excitation of a sample and means for measuring an emission from the sample, the process comprising the phases of
         selecting a measurement mode,   selecting a filter for filtering excitation beam and/or emission beam,   selecting at least one changeable optical module for a measurement head, the optical module guiding the excitation beam from an illumination source into the sample and/or guiding at least one emission beam from a sample into at least one detector,   performing the selected optical measurement,
 
the process being characterized in that in the step of selecting the optical module and/or filter, a kind of optical module or filter is selected, which has readable identification information for automatic verification of the used optical module/filter.
       

   A method according to the invention for optical measurement of samples comprising the step of transmitting excitation/emission beam between the sample and a measurement head of an optical instrument, comprising transmitting said beam through a selectable optical component, is characterized in that identification information is read from at least one said selectable optical component and the optical component used for the measurement is determined on the basis of read information. 
   Some preferred embodiments are described in the dependent claims. 
   An important advantage of the invention relates to achieving reliable measurement results. As the selectable filters and optical modules are automatically identified there is no risk of using a wrong optical component in the measurement. It is also possible to record the types of the optical components that have been used in each measurement so that they can be later checked if necessary. 
   The invention also allows an easy changeability of the optical components. As the components are identified by the instrument, the user may install the components to the component base (e.g. carousel or slide) in any order without a risk of using a wrong component. 
   The invention also allows easy upgrade of features to the instrument. After new filters or optical modules been installed, the instrument automatically identifies them and selects the suitable measurement parameters. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other advantages of the invention will become apparent from the following detailed description and by referring to the drawings where: 
       FIG. 1  is a schematic block diagram of a prior art optical unit of a measurement instrument, 
       FIG. 2  is a schematic illustration of optical paths and main components of an exemplary optical unit for a measurement instrument according to the invention, 
       FIG. 3  is a schematic block diagram of an exemplary measurement instrument according to the invention, 
       FIG. 4  is a schematic block diagram of an optical unit showing a first embodiment for a double emission measurement according to the invention, 
       FIG. 5  is a schematic block diagram of an optical unit showing a second embodiment for a double emission measurement according to the invention, 
       FIG. 6  is a schematic block diagram of an optical unit showing a third embodiment for a double emission measurement according to the invention, 
       FIG. 7  is a schematic block diagram of an optical unit showing a fourth embodiment for a double emission measurement according to the invention, 
       FIG. 8  is a schematic block diagram of an optical unit showing a fifth embodiment for a double emission measurement according to the invention, 
       FIG. 9  is a schematic block diagram of an optical unit showing a sixth embodiment for a double emission measurement according to the invention, 
       FIG. 10A  illustrates a perspective view of an exemplary top optical module according to the invention, 
       FIG. 10B  illustrates a perspective view of an exemplary bottom optical module according to the invention, 
       FIG. 11  illustrates an exemplary four-position wheel with four optical modules according to the invention, 
       FIG. 12  illustrates an exemplary filter slide according to the invention, 
       FIG. 13  illustrates a first exemplary top head optical module for implementing the invention, 
       FIG. 14  illustrates a second exemplary top head optical module for implementing the invention, 
       FIG. 15  illustrates a third exemplary top head optical module for implementing the invention, 
       FIG. 16  illustrates a fourth exemplary top head optical module for implementing the invention, 
       FIG. 17  illustrates a fifth exemplary top head optical module for implementing the invention, 
       FIG. 18  illustrates a first exemplary bottom head optical module according to the invention for implementing the invention, 
       FIG. 19  illustrates a second exemplary bottom head optical module for implementing the invention, 
       FIG. 20  illustrates a third exemplary bottom head optical module for implementing the invention, 
       FIG. 21  illustrates a fourth exemplary bottom head optical module for implementing the invention, 
       FIG. 22  illustrates a fifth exemplary bottom head optical module for implementing the invention, 
       FIG. 23  illustrates an exemplary process for performing a measurement with an optical measurement instrument according to the invention. 
       FIG. 24  illustrates an exemplary method for performing a measurement according to the invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  was already explained in the description of the prior art. In the following, the principle of an exemplary instrument according to invention is first described referring to  FIG. 2 . Then, an example of a more detailed implementation is described referring to  FIG. 3 , which is a block diagram of exemplary analyser equipment according to the invention. Next there are some exemplary embodiments described for using an analyser with an automatic identification according to the invention for double emission measurements, referring to  FIGS. 4–12 . After this, relating to  FIGS. 13–22  there is a description of exemplary optical cubes suitable for identification according to the invention and which can be used e.g. for the measurements referred to in  FIGS. 4–12 . Finally, examples of a process and a method for performing a measurement according to invention are described referring to flow diagrams in  FIGS. 23 and 24 . 
     FIG. 2  illustrates main components and optical paths of an exemplary optical analyser instrument according to the invention. The instrument comprises an illumination source  211  for the excitation of a sample. The radiation from the lamp  211  is collimated with lens  215  and directed through an interference filter  214 . Different filters can be selected for different wavelengths. The excitation filters are equipped with a code identifying their type. The bar code is read with a bar code reader  219 . The excitation beam is then focused to an end of a fibre optic guide  218 , which guides it to an aperture  246  of an optical module according to the invention. The fibre optic guide is preferably a bundle of fibres, such as 200 pieces of fibres with a diameter of 100 μm. One important purpose of the fibre optic guide is to mix the light of the illumination source in order to avoid an uneven distribution of excitation beam within the sample volume to be measured. The excitation beam is guided through an aperture  246  of the optical module and reflected by a dichroic mirror  241  inside the optical module  240 . The excitation beam is further directed into the sample  281  through an aperture of the optical module and a lens system  223 . A part of the illumination light is reflected by a beam splitter mirror  243  and guided through an aperture into a reference detector  299  in order to give reference information on the actual illumination intensity. While the reference mirror is located in the changeable mirror block, the excitation filter differences can be compensated by modifying the properties of the reference mirror. This way high feedback accuracy is achieved. A beam splitter mirror can be produced e.g. by forming reflective coating for the mirror to be e.g. stripes or dots, which cover only a part of the mirror surface. 
   The emission beam from the sample  281  is directed with the lens system  223  through an aperture into the optical module  240 , where it passes the (preferably) dichroic mirror  241 . The dichroic mirror is preferably designed for each label so that it reflects exitation wavelength but transmits emission wavelengths. The emission beam is then divided inside the optical module into two beams by a second mirror  242 . The mirror is preferably a dichroic mirror, which functions as a filter so that a beam with a wavelength of the first emission is transmitted through the mirror and focused through an aperture  244  according to the invention to the first detector  231   a . The beam with a wavelength of the second emission is reflected and guided focused through another aperture  245  to the second detector  231   b . The second dichroic mirror is therefore also preferably designed for each label/pair of labels so that it transmits first emission wavelengths but reflects second emission wavelengths. 
   The optical modules are equipped with a code identifying their type. The bar code is read with a bar code reader  249 . 
   The first emission beam received from the aperture of the optical module is collimated with a lens  233   a  and directed through an interference filter  234   a  in order to prevent light with a wavelength outside the first emission from passing to the first detector. The first emission beam is then focused with lens  235   a  to the first detector  231   a.  The second emission beam received from another aperture of the optical module is reflected with a mirror  238  to a lens  233   b  where the beam is collimated and directed through a second interference filter  234   b  in order to prevent light with a wavelength outside the second emission from passing to the second detector. The second emission beam is then focused with lens  235   a  to the first detector  231   a.    
   The emission filters are equipped with a code identifying their type. The bar codes are read with bar code readers  239   a  and  239   b.    
   The signals received from the detectors are then amplified and processed to achieve a value for the intensities of the first and second emissions. The excitation and emission parts of the instrument can be used, except for photoluminescence measurements, also to e.g. photometric and chemiluminescence measurements. 
   As already mentioned, an essential feature of the invention is that the filters and optical module can be automatically identified and therefore the correct filter type and optical module type is verified. This allows performing various types of measurements by automatically changing the optical components, and each of the measurements can be reliably performed with the optimal components. The advantages of the invention become more apparent in the following more complete example of an optical instrument according to the invention. 
     FIG. 3  illustrates in more detail an exemplary optical instrument according to the invention. The instrument has a top measurement head  320 , which includes components for providing an excitation beam and for detecting emissions from above the sample. The instrument has also an optional bottom measurement head  360 , which includes components for providing an excitation beam and for detecting emissions from below the sample. The instrument further comprises a sample platform  380 , which has means for moving and a sample tray  389  in order to position successive samples  381  into the measurement volume. There may also be means provided for adjusting the vertical position of the sample platform relative to the top and bottom measurement heads. 
   The instrument has one or two illumination sources. The main illumination source  312   a  includes a pulse lamp, and the optical energy of each pulse is preferably equal. The excitation beam generated by the pulse lamp is collimated with a lens  315  and directed through an interference filter  314 . The filter is placed on a filter slide, so that the excitation filter to be used in a measurement can be selected from several filters. The filters are equipped with codes identifying their types, and the instrument has a code reader such as a bar code reader. The bar code readers are not shown in  FIG. 3  as they were already illustrated in  FIG. 2 . The excitation beam is then focused to an end of a fibre optic guide  318 , which mixes the excitation beam and guides it to an aperture of an optical module  340  according to the invention. The optical module  340  and the lens system  323  directs the excitation beam into the sample  391 . The optical module is not either described here in more detail because it is explained in relation to other Figures. 
   The equipment may also include a second pulse lamp  312   b ,  311   b , which may be a low power lamp, e.g. for simultaneous photometric measurements. The instrument has an optical fibre guide  312   a  for guiding the light from the second lamp. The light can be distributed for the photometric measurement into three filters  314   h ,  314   j  and  314   k  with fibre branches  377   h ,  377   j  and  377   k . These filters are also preferably coded for identification by separate code readers according to the invention. The light beams are collimated with lenses  375   h ,  375   j and  375   k before directing the beams through the filters. The filters can be located on the same or different filter slide as the filter  314   e  for the first illumination source. If the same filter slide is used for filters of both lamps, the simultaneous measurement modes must be taken into account when the location of the filters is planned. These filters are also preferably coded for identification by a code reader according to the invention. After filtering, the beams are collimated into ends of three optical fibre cables  378 , which are led to the bottom measurement head for the photometric measurement. The light beams from the optical cables  378  are focused to three samples  384  with a lens system  379  including lenses for each three beams. After transmitting through the samples the beams are measured with three detectors  322   d ,  322   e  and  322   f , which are e.g. a photo diodes. The three ends of the fibre optic cables, three lenses, three simultaneously measured samples and three detectors are in this case located in a row perpendicular to the plane of the drawing and thus only one of them can be seen in the drawing. 
   It is preferable to have a separate optics for the photometrics measurement so that a photoluminescence measurement and a photometrics measurement can be performed simultaneously from different samples. If simultaneous photoluminescence and photometric measurements are required, the analyzer is preferably equipped with two pulse lamps. However, it is also possible to use an instrument with one lamp for photometrics measurements. For example, an optical switch  317  may have an output for an optical fibre  378   a , which leads light from the lamp  312   a  to the photometrics measurement optics  379 . It is then possible to control the optical switch either to guide the light for providing excitation for an emission measurement or to guide the light the a photometric measurement. 
   An optical fibre  318 T is used for guiding the excitation beam from the optical switch  317  to the optical module  340  of the top measurement head. An optical fibre  318 B is used for guiding the excitation beam from the optical switch  317  to the optical module  350  of the bottom measurement head. The instrument may also have a further lamp so that different lamps can be selected for providing the excitation beam of the top head and the bottom head. In this case, a more versatile optical switch system is required. 
   The emission beam from the sample  381  is directed with the lens system  323  into the optical module  340  where the emission beam is divided into to two beams. A dichroic mirror in the optical module preferably functions as a filter so that a beam with a wavelength of the first emission is transmitted through the to the first detector  331   a,  and a beam with a wavelength of the second emission is reflected to the second detector  331   b . The detector can be e.g. a photo-multiplier tube, which may be used in analogue mode or in photon count mode, or in both modes simultaneously. When the equipment includes two photoluminescence detectors they may be of different types and the detection modes may be different during a measurement. 
   The first emission beam is collimated with a lens  333   a  and directed through an interference filter  334   j  in order to prevent light with a wavelength outside the first emission from passing to the first detector. The first emission beam is then focused with lens  335   a  to the first detector  331   a . The second emission beam is reflected with a mirror  338  to a lens  333   b  where the beam is collimated and directed through a second interference filter  334   k  in order to prevent light with a wavelength outside the second emission from passing to the second detector. The second emission beam is then focused with lens  335   a  to the first detector  331   a . The filters  334   j  and  334   k  are located on same filter slide or they may locate on different filter slides. The filter slide(s) is movable so that the filters used in the measurement can be selected from a number of filters with different pass-band wavelengths. The filter type is verified by reading the code of the filter. 
   In an instrument also comprising a bottom measurement head there are optical switches  337   a  and  337   b  for selecting the detected emission beam from the top or bottom measurement head. An optical fibre  338   a  is used for guiding the first emission beam from the optical module  350  of the bottom measurement head  360  to the optical switch  337   a . Another optical fibre  338   b  is used for guiding the second emission beam from the optical module  350  of the bottom measurement head  360  to the optical switch  337   b.    
   The signals received from the detectors are then amplified and processed to achieve a value for the intensities of the first and second emissions. Measurement signals and reference signals are amplified and read after each excitation pulse and signal corrections are calculated. Basic references are determined with standard solvents after the analyzer has been assembled. If there are more than one excitation pulses used for one well, the corresponding emission signals are digitally integrated. 
   The instrument has also an optional detector  332   c ,  331   c  for chemiluminescence measurements. The detector receives the chemiluminescence radiation from the sample via a thick bundle of optical fibres  318   c . It is preferable to have a separate optics for the chemiluminescence measurement so that a photoluminescence measurement and a chemiluminescence measurement can be performed simultaneously from different samples. In  FIG. 3  the chemiluminescence measurement is made from a sample located behind sample  381 . A photo-multiplier tube can also be used as a detector for the chemiluminescence. The detector can be used in analogue mode or digital mode, or if the properties of the tube allow, both modes may be used simultaneously. 
   The instrument comprises a carousel wheel  328  for the attachment of optical modules  340   a ,  340   b , . . . The wheel can be rotated around its fixing point  329 , and the optical module used in a measurement can thus be selected by controlling the position of the wheel and reading the identification of the installed modules. When the optical modules are equipped with machine readable codes, such as bar codes, the processor of the equipment can thus check with a code reader, which types of optical modules are installed in each location. This way it can be certified that a correct type of optical module is used for each measurement. 
   If the instrument is equipped with a bottom measurement head, there may be a similar optical module  350  used in the bottom measurement head as in the top measurement head. The excitation and emission beams are lead between the two measurement heads with optical fibres  338   a ,  338   b  and  318 B. There is also a lens system  363  for focusing the beams to the sample and ends of the optical fibres. Since the optical module of the bottom measurement head needs not be so frequently changed, it may be manually changeable. Alternatively a processor-controlled carousel can also be used in the bottom measurement head. The optical modules of the bottom measurement head are preferably also identified with a code reader. 
   The optical modules are shown essentially enlarged in  FIG. 3  in order to better illustrate the optical paths in the instruments. The actual size of the optical modules may be as small as 20 mm×20 mm×20 mm. 
   The instrument is also equipped with electronics for amplifying and processing the signals from the detectors, as well as electronics for driving the lamp(s). There is also control electronics provided for controlling the measurements, such as selecting filter(s), selecting the optical module(s), controlling optical switch(es), controlling the position of the sample tray  389  for selecting the sample to be measured, and controlling the positions of the measurement heads  320  and  360  relative to the sample platform  380 . The electronics is not shown in  FIG. 3 , as the required electronics can be designed by a skilled person in the art. 
   In the preferred embodiment the user can adjust various parameters of a measurement. The excitation pulse energy is adjusted by the discharge voltage and by the capacitors of the flash lamp power supply. Total excitation energy of one measurement is controlled by measuring every pulse and comparing the sum to a reference level of the integrator. The parameters of measurements are preferably user adjustable. 
   Next some embodiments of possible measurement modes are described referring to  FIGS. 4–9 . These exemplary embodiments show how the interface for an optical module with apertures gives a possibility for a large variety of different measurement modes. These measurement modes are available with an automatic selection and control of filters, optical switches and just one changeable optical module in each measurement head. The described measurement modes are related but not restricted to photoluminescence measurements. 
     FIG. 4  illustrates a first embodiment of performing a photoluminescence measurement with a measuring instrument according to the present invention. In this embodiment both excitation and detection is made from the above the sample using the top measurement head of the instrument. One of the possible alternative excitation sources  411  gives an excitation pulse, which is guided through an optical system  413  to an optical fibre  418 . The optical system may include filters, lenses and mechanical components as was shown in  FIG. 3 . The excitation beam is mixed in the optical fibre and lead to the optical module  450 . The excitation beam is reflected from the mirror  441  and collimated in the optical system  423  into the sample  481  on the sample plate  480  to be measured. The excitation beam provides excitation for two simultaneous measurements. 
   The excited sample  481  gives two emissions that are measured with detectors A and B. The emission beams are first collimated in the optical system  423 , and the beams lead to the optical module  440 . The emission beams first transmit the dichroic mirror  441 , where after the second dichroic mirror  442  separates the two emission beams. The separation may be based on the wavelength of the emissions, polarization etc. The first emission beam is substantially transmitted through the second dichroic mirror  442  and further collimated and filtered in the optical system  433   a  to be measured in the detector  431   a . The second emission beam is substantially reflected by the second dichroic mirror  442 , and further reflected by the mirror  438 . The beam is collimated and filtered in the optical system  433   b  to be measured in the detector  431   b.    
   One advantage of this first embodiment is that the emissions are guided to both detectors directly i.e. without optical fibre cables. This way an optimal sensitivity of the measurement is achieved. 
   In the first embodiment illustrated in  FIG. 4  the whole measurement is made with the top measurement head, and so it is not necessary to have a bottom measurement head in the instrument in order to perform the double emission measurement. The use of an optical module according to the invention gives therefore a possibility to make versatile measurements efficiently even with a basic instrument, which is not equipped with a bottom measurement head. In the further described embodiments for using the instrument according to the invention, also the bottom measurement head is used. 
     FIG. 5  illustrates a second embodiment of performing a photoluminescence measurement with a measuring instrument according to the present invention. In this embodiment both excitation and detection is made from the below the sample using the bottom measurement head of the instrument. One of the possible alternative excitation sources  511  gives an excitation pulse, which is lead to the optical module of the bottom measurement head with an optical fibre (not shown in the  FIG. 5 ), wherein the excitation beam is mixed. The excitation beam is reflected from the mirror  551  and collimated in the optical system  563  into the sample  581  on the sample plate  580  to be measured. The excitation beam provides excitation for two simultaneous measurements, or alternatively two successive excitations with different wavelengths are made with successive excitation pulses (successive excitation is preferably used only in bottom measurements). 
   The excited sample  581  gives two emissions that are measured with detectors A and B. The emission beams are first collimated in the optical system  563 , and the beams are lead to the optical module  550 . The emission beams first transmit the dichroic mirror  551 , where after the second dichroic mirror  552  separates the two emission beams. The separation may be based on the wavelength of the emissions, polarization etc. The first emission beam is substantially transmitted through the second dichroic mirror  552  and further lead to the detector  531   a  through an optical fibre (not shown in  FIG. 5 ). The second emission beam is substantially reflected by the second dichroic mirror  552 , and lead to the second detector  531   b  through an optical fibre (not shown in  FIG. 5 ). The emission beams are then measured in the detectors  531   a  and  531   b.    
   In the second embodiment illustrated in  FIG. 5  the whole measurement is made with the bottom measurement head. This embodiment is useful for making measurements where the substance to be measured lies essentially on the bottom of the sample tube. With this embodiment it is possible to measure simultaneously two emissions from the bottom surface of such substance and thus the measurement can be performed with optimal efficiency. This embodiment also makes it possible to use the top measurement head for a chemiluminescence measurement. This way both the photoluminescence measurement and the chemiluminescence measurement can be performed the samples without changing the locations of the optical modules or cables between the measurements. In the embodiments that are described in the following, both the top measurement head and the bottom measurement head are used for the photoluminescence measurement. 
     FIG. 6  illustrates a third embodiment of performing a photoluminescence measurement with a measuring instrument according to the present invention. In this embodiment the excitation is made from the above the sample using the top measurement head, and the detection is made from below the sample using the bottom measurement head of the instrument. One of the possible alternative excitation sources  611  gives an excitation pulse, which is guided through an optical system  613  to an optical fibre  618 . The optical system may include filters, lenses and mechanical components as was shown in  FIG. 3 . The excitation beam is mixed in the optical fibre and lead to the optical module  650 . The excitation beam is reflected from the mirror  641  and collimated in the optical system  623  into the sample  681  on the sample plate  680  to be measured. The excitation beam provides excitations for two simultaneous measurements. 
   The excited sample  681  gives two emissions that are measured with detectors A and B. The emission beams are first collimated in the optical system  663 , and the beams are lead to the optical module  650  of the bottom measurement head. The emission beams first transmit the dichroic mirror  651 , where after the second dichroic mirror  652  separates the two emission beams. The separation may be based on the wavelength of the emissions, polarization etc. The first emission beam is substantially transmitted through the second dichroic mirror  652  and further lead to the detector  631   a  through an optical fibre (not shown in  FIG. 6 ). The second emission beam is substantially reflected by the second dichroic mirror  652 , and lead to the second detector  631   b  through an optical fibre (not shown in  FIG. 6 ). The emission beams are then measured in the detectors  631   a  and  631   b.    
   The third embodiment illustrated in  FIG. 6  gives some advantages compared to the second embodiment of  FIG. 5 . When the excitation pulse is exposed from the top measurement head the length of the optical fibre within the optical route of the excitation pulse can be made optimally short. This way the attenuation of the optical fibre can be minimized, and consequently a maximum illumination intensity is achieved. 
   Another advantage of the embodiment of  FIG. 6  is that it is possible to use an optical module where there is no first mirror  651  in the module. This way the attenuation of the emission beam caused by the excitation mirror  651  can be totally avoided. 
     FIG. 7  illustrates a fourth embodiment of performing a photoluminescence measurement with a measuring instrument according to the present invention. In this embodiment the excitation is made from below the sample using the bottom measurement head, and the detection is made from above the sample using the top measurement head of the instrument. One of the possible alternative excitation sources  711  gives an excitation pulse, which is lead to the optical module of the bottom measurement head with an optical fibre (not shown in the  FIG. 7 ), wherein the excitation beam is mixed. The excitation beam is reflected from the mirror  751  and collimated in the optical system  763  into the sample  781  on the sample plate  780  to be measured. The excitation beam provides excitation for two simultaneous measurements. 
   The excited sample  781  gives two emissions that are measured with detectors A and B. The emission beams are first collimated in the optical system  723 , and the beams lead to the optical module  740 . The emission beams first transmit the dichroic mirror  741 , where after the second dichroic mirror  742  separates the two emission beams. The separation may be based on the wavelength of the emissions, polarization etc. The first emission beam is substantially transmitted through the second dichroic mirror  742  and further collimated and filtered in the optical system  733   a  to be measured in the detector  731   a . The second emission beam is substantially reflected by the second dichroic mirror  742 , and further reflected by the mirror  738 . The beam is collimated and filtered in the optical system  733   b  to be measured in the detector  731   b.    
   The fourth embodiment illustrated in  FIG. 7  gives some advantages compared to the first embodiment of  FIG. 4 . When the excitation beam is exposed from the bottom measurement head it is possible to use in the top measurement head an optical module where there is no first mirror  741  in the module. This way the attenuation of the emission beam caused by the excitation mirror  741  can be totally avoided. 
     FIG. 8  illustrates a fifth embodiment of performing a photoluminescence measurement with a measuring instrument according to the present invention. In this embodiment the excitation is made from the above the sample using the top measurement head. The detection if the first emission is made from above the sample using the top measurement head, and the detection of the second emission is made from below the sample using the bottom measurement head of the instrument. 
   One of the possible alternative excitation sources  811  gives an excitation pulse, which is guided through an optical system  813  to an optical fibre  818 . The optical system may include filters, lenses and mechanical components as was shown in  FIG. 3 . The excitation beam is mixed in the optical fibre and lead to the optical module  850 . The excitation beam is reflected from the mirror  841  and collimated in the optical system  823  into the sample  881  on the sample plate  880  to be measured. The excitation beam provides excitations for two simultaneous measurements. 
   The excited sample  881  gives two emissions that are measured with detectors A and B. The first emission beam is first collimated in the optical system  823  and lead to the optical module  840  of the top measurement head. The first emission beam is substantially transmitted by the first dichroic mirror  841  and the second dichroic mirror  842 . The first emission beam is then collimated and filtered in the optical system  833   a  to be measured in the detector  831   a.    
   The second emission beam is first collimated in the optical system  863 , and the beam is lead to the optical module  850  of the bottom measurement head. The emission beam first transmits the dichroic mirror  651 , where after it is substantially reflected in the second dichroic mirror  852 . The second emission beam is lead to the second detector  831   b  through an optical fibre (not shown in  FIG. 6 ). The emission beams are then measured in the detectors  831   a  and  831   b.    
   One advantage of the embodiment of  FIG. 8  is that it is possible to measure simultaneously emissions from both above and below the sample simultaneously. 
   There is also another advantage related to the embodiment illustrated in  FIG. 8 . When the two emissions are measured with different measurement heads it allows the use of only one mirror within the path of the emission beam. In the top measurement head it is possible to use an optical module, which has no second mirror  842 . In the bottom measurement head it is possible to use an optical module, which has no first mirror  851 . It is also possible to use a non-dichroic mirror  852  in the bottom measurement head. This way a very small attenuation is achieved in the measurement of the both emissions. Especially the measurement of the first emission can be measured with high sensitivity, because of the direct optical path between the sample and the detector  831   a.    
     FIG. 9  illustrates a sixth embodiment of performing a photoluminescence measurement with a measuring instrument according to the present invention. In this embodiment the excitation is made from below the sample using the bottom measurement head. The detection of the first emission is made from below the sample using the bottom measurement head, and the detection of the second emission is made from above the sample using the top measurement head of the instrument. 
   One of the possible alternative excitation sources  911  gives an excitation pulse, which is lead to the optical module of the bottom measurement head with an optical fibre (not shown in the  FIG. 9 ), wherein the excitation beam is mixed. The excitation beam is reflected from the mirror  951  and collimated in the optical system  963  into the sample  981  on the sample plate  980  to be measured. The excitation beam provides excitation for two simultaneous measurements. 
   The excited sample  981  gives two emissions that are measured with detectors A and B. The first emission beam is first collimated in the optical system  963 , and the beam is lead to the optical module  950  of the bottom measurement head. The first emission beam is substantially transmitted by the first dichroic mirror  951  and the second dichroic mirror  952 . The first emission beam is further lead to the detector  831   a  through an optical fibre (not shown in  FIG. 9 ). The first emission beam is finally measured in the detector  931   a.    
   The second emission beam is first collimated in the optical system  923 , and lead to the optical module  940 . The second emission beam first transmits the dichroic mirror  941 , where after the second emission beam is substantially reflected by the second dichroic mirror  942 , and further reflected by the mirror  938 . The second emission beam is collimated and filtered in the optical system  933   b  and measured in the detector  931   b.    
   Also the embodiment of  FIG. 9  has the advantage that it is possible to measure simultaneously emissions from both above and below the sample simultaneously. 
   There is also another advantage related to the embodiment illustrated in  FIG. 9 . When the two emissions are measured with different measurement heads it allows the use of only one mirror within the path of the emission beam. In the top measurement head it is possible to use an optical module, which has no first mirror  941 . In the bottom measurement head it is possible to use an optical module, which has no second mirror  952 . It is also possible to use a non-dichroic mirror  941  in the top measurement head. This way a very small attenuation is achieved in the measurement of both emissions. 
     FIG. 10A  illustrates a perspective view of an exemplary optical module  1040  according to the invention. It is designed for a top measurement head, but it is also possible to design a bottom measurement head, which is adapted for such a module. The module comprises a bar code  1049  according to the invention. The Figure also shows an aperture  1046  for the excitation beam from the lamp, an aperture  1044  for the emission beam to the first detector and an aperture for the emission beam to the second detector. In this case, the apertures of the optical module can be changed by changing the respective wall  1064 ,  1065  or  1066  of the optical module. The walls can be attached by e.g. screws (not shown in FIG  10 A). 
     FIG. 10B  illustrates a perspective view of another exemplary optical module  1050  according to the invention. It is designed for a bottom measurement head, but it is also possible to design top and bottom measurement heads, which are adapted for similar modules. The module comprises a bar code  1059  according to the invention. The Figure also shows an aperture  1056  for the excitation beam from the lamp, and an aperture  1058  for providing an optical interface to the sample. In this case, aperture  1056  of the optical module can be changed by changing the respective wall  1066  of the optical module. The wall can be attached by e.g. screws (not shown in FIG  10 B). 
     FIG. 11  illustrates a top view of an exemplary arrangement where four optical modules are attached to a carousel  1128  in a top measurement head. The optical modules are cited  1140   a ,  1140   b ,  1140   c  and  1140   d  with their apertures for the emission to the first detector cited as  1144   a ,  1144   b ,  1144   c  and  1144   d . The instrument preferably has means for turning the carousel around its axis  1129  so the one of the four optical modules can be selected for use by the program of the instrument. If the optical modules are equipped with a code, such as bar code, the control unit of the instrument may check, which modules are available in each position of the carousel. It is preferable that there is an attachment arrangement for the optical modules, which allows the optical modules be easily removed and attached when necessary. Although the carousel of  FIG. 11  is designed for a top measurement head, a bottom measurement head may of course also be equipped with such a carousel for an automatically controlled change of the optical module. Although there are four optical modules shown in  FIG. 11 , there may naturally be a different number of optical modules. Considering the preferable small size of the optical modules, it is possible to provide a carousel with e.g. 8 or 16 optical modules. 
   It is also possible to use another kind of mechanical arrangement for the optical modules instead of a carousel. For example, there may be a slide for the optical modules, wherein the optical modules are placed parallel in a line, and a module to be used can be changed by shifting the slide into a corresponding position. If a slide is used, there may be slides of different lengths with a different number on locations for optical modules. 
     FIG. 12  shows a filter arrangement according to the invention. The filter arrangement may be used for filtering excitation beam, emission beam or light used for photometrics. The filter slide  1234  comprises several filter components. The filter components are preferably manually connected/disconnected to the slide. Such an attachment allows an easy change of the filter components. A filter component  1234 E comprises a filter window  1234   e  and a bar code  1249  for the automatic identification of the filter component. 
   In the following some embodiments of possible optical modules are described referring to  FIGS. 13–22 . These exemplary embodiments show optical modules, which can be used in an optical instrument according to the invention including an interface for receiving two emissions from an optical module. These optical modules can also be used for implementing the measurement modes described in  FIGS. 4–9 , and generally for implementing the process and method according to the invention. 
     FIG. 13  illustrates a cross section view from the side of an exemplary optical module for a top measurement head. This optical module  1340  comprises three dichroic mirrors. The module receives an excitation beam from the aperture  1346 , and mirror  1343  reflects a part of the excitation beam into a reference sensor through the aperture  1347 . The main part of the excitation beam is reflected from the mirror  1341  and thus directed to a sample through the aperture  1348 . 
   The emission from the sample is received into the module through the aperture  1348 . The emissions transmit the dichroic mirror  1341  and reach the further dichroic mirror  1342 . The mirror  1342  splits the emission beam into a first beam that is led to the first detector through the aperture  1344 , and a second beam that is led to the second detector through the aperture  1345 . 
   The optical module illustrated in  FIG. 13  is very suitable for the double emission measurement, which was described in  FIG. 4 . However, this optical module can be used also in many other types of measurements, such as those described in  FIGS. 6–9  or single emission measurements, if an optimized performance is not required. 
     FIG. 14  illustrates a cross section view from the side of another exemplary optical module for a top measurement head. This optical module  1440  comprises one dichroic mirror  1443  and one non-dichroic mirror  1441 . The module receives an excitation beam from the aperture  1446 , and mirror  1443  reflects a part of the excitation beam into a reference sensor through the aperture  1447 . The main part of the excitation beam is reflected from the mirror  1441  and thus directed to a sample through the aperture  1448 . 
   This optical module is designed for measurements where emission measurement is made using the bottom measurement head. The measurement illustrated in  FIG. 6  is an example of such a measurement. Therefore this optical module for the top measurement head does not have any optical paths for emission beams. One advantage of this optical module is that attenuation of the excitation beam is minimal. 
     FIG. 15  illustrates a cross section view from the side of a third exemplary optical module for a top measurement head. This optical module  1540  comprises one dichroic mirror. This optical module is designed for measurements where bottom measurement head is used for excitation. An example of this kind of measurement is illustrated in  FIG. 7 . Therefore this optical module does not have any optical paths for an excitation beam. 
   The emission from the sample is received into the module through the aperture  1548 . The mirror  1542  splits the emission beam into a first beam that is led to the first detector through the aperture  1544 , and a second beam that is led to the second detector through the aperture  1545 . 
   Although this optical module illustrated in  FIG. 15  is very suitable for the double emission measurement, which was described in  FIG. 7 , this optical module can also be used in many other types of measurements, such as single emission measurements, if an optimized performance is not required. 
     FIG. 16  illustrates a cross section view from the side of a fourth exemplary optical module for a top measurement head. This optical module  1640  comprises two dichroic mirrors. The module receives an excitation beam from the aperture  1646 , and mirror  1643  reflects a part of the excitation beam into a reference sensor through the aperture  1647 . The main part of the excitation beam is reflected from the mirror  1641  and thus directed to a sample through the aperture  1648 . 
   The emission from the sample is received into the module through the aperture  1648 . The emission transmits the dichroic mirror  1641 , and it is led to the first detector through the aperture  1644 . 
   The optical module illustrated in  FIG. 16  is very suitable for a double emission measurement, where the first emission is measured with the top measurement head and the second emission is measured with the bottom measurement head. This kind of measurement was described in  FIG. 8 . However, this optical module can be used also in many other types of measurements, such as single emission measurements. 
     FIG. 17  illustrates a cross section view from the side of a fifth exemplary optical module for a top measurement head. This optical module  1740  comprises one nondichroic mirror. This optical module is designed for measurements where excitation is made using the bottom measurement head. An example of this kind of measurement is illustrated in  FIG. 9 . Therefore this optical module does not have any optical paths for an excitation beam. 
   The emission from the sample is received into the module through the aperture  1748 . The mirror  1742  reflects the emission beam, which is further led to the second detector through the aperture  1745 . 
   The optical module illustrated in  FIG. 17  is very suitable for a double emission measurement, where the second emission is measured with the top measurement head and the first emission is measured with the bottom measurement head. This kind of measurement was described in  FIG. 9 . However, this optical module can be used also in many other types of measurements, if an optimised performance is not required. 
   Although the optical modules illustrated in  FIGS. 13–17  are designed for the top measurement head, it is also possible to design the bottom measurement head be adapted to the use of these modules. 
     FIG. 18  illustrates a cross section view from the side of an exemplary optical module for a bottom measurement head. This optical module  1850  comprises three mirrors. The module receives an excitation beam from the aperture  1856 , and mirror  1853  reflects a part of the excitation beam into a reference sensor through the aperture  1857 . The main part of the excitation beam is reflected from the mirror  1851  and thus directed to a sample through the aperture  1858 . 
   The emissions from the sample are received into the module through the aperture  1858 . The emissions transmit the dichroic mirror  1851  and reach the further dichroic mirror  1852 . The mirror  1852  splits the emission beam into a first beam that is led to the first detector through the aperture  1854 , and a second beam that is led to the second detector through the aperture  1855 . 
   The optical module illustrated in  FIG. 18  is very suitable for the double emission measurement, which was described in  FIG. 5 . However, this optical module can be used also in many other types of measurements, such as those described in  FIGS. 6–9  or single emission measurements, if an optimized performance is not required. 
     FIG. 19  illustrates a cross section view from the side of another exemplary optical module for a bottom measurement head. This optical module  1950  comprises one dichroic mirror. This optical module is designed for measurements where excitation is made using the top measurement head. An example of this kind of measurement is illustrated in  FIG. 6 . Therefore this optical module does not have any optical paths for an excitation beam. 
   The emissions from the sample are received into the module through the aperture  1958 . The mirror  1952  splits the emission beam into a first beam that is led to the first detector through the aperture  1954 , and a second beam that is led to the second detector through the aperture  1955 . 
   Although this optical module illustrated in  FIG. 19  is very suitable for the double emission measurement, which was described in  FIG. 6 , this optical module can also be used in many other types of measurements, such as single emission measurements, if an optimized performance is not required. 
     FIG. 20  illustrates a cross section view from the side of a third exemplary optical module for a bottom measurement head. This optical module  2050  comprises one beam splitter mirror  2053  and one further mirror  2051 . The module receives an excitation beam from the aperture  2056 , and mirror  2053  reflects a part of the excitation beam into a reference sensor through the aperture  2057 . The main part of the excitation beam is reflected from the mirror  2051  and thus directed to a sample through the aperture  2058 . 
   This optical module is designed for measurements where emission measurement is made using the top measurement head. The measurement illustrated in  FIG. 7  is an example of such a measurement. Therefore this optical module designed for the bottom measurement head does not have any optical paths for emission beams. One advantage of this optical module is that attenuation of the excitation beam is small. 
     FIG. 21  illustrates a cross section view from the side of a fourth exemplary optical module for a bottom measurement head. This optical module  2150  comprises one non-dichroic mirror. This optical module is designed for measurements where excitation is made using the top measurement head. An example of this kind of measurement is illustrated in  FIG. 8 . Therefore this optical module does not have any optical paths for an excitation beam. 
   The emission from the sample is received into the module through the aperture  2158 . The mirror  2152  reflects the emission beam, which is further led to the second detector through the aperture  2155 . 
   The optical module illustrated in  FIG. 21  is very suitable for a double emission measurement, where the second emission is measured with the bottom measurement head and the first emission is measured with the top measurement head. This kind of measurement was described in  FIG. 8 . However, this optical module can be used also in other types of measurements, if an optimised performance is not required. 
     FIG. 22  illustrates a cross section view from the side of a fifth exemplary optical module for a bottom measurement head. This optical module  2250  comprises two dicroic mirrors. The module receives an excitation beam from the aperture  2256 , and mirror  2253  reflects a part of the excitation beam into a reference sensor through the aperture  2257 . The main part of the excitation beam is reflected from the mirror  2251  and thus directed to a sample through the aperture  2258 . 
   The emission from the sample is received into the module through the aperture  2258 . The emission transmits the dichroic mirror  2251 , and it is led to the first detector through the aperture  2254 . 
   The optical module illustrated in  FIG. 22  is very suitable for a double emission measurement, where the first emission is measured with the bottom measurement head and the second emission is measured with the top measurement head. This kind of measurement was described in  FIG. 9 . However, this optical module can be used also in many other types of measurements, such as single emission measurements. 
   Although the optical modules illustrated in  FIGS. 18–22  are designed for the bottom measurement head, it is also possible to design both the top measurement head and the bottom measurement head be adapted to the use of these modules. 
   The variety of different measurement modes and a variety of different optical modules, with corresponding excitation and emission filters, show the importance of reliable selection and verification of the components used for each measurement in order to guarantee an optimal performance. 
     FIG. 23  illustrates a flow diagram of an exemplary process according to the invention for using an optical instrument for a photoluminescence measurement. In phase  11  the type of measurement is selected. The excitation source and interference filter is then selected according to the measurement type in phase  12 . In this phase also the identification code of the excitation filter is read and thus a correct type is verified. Either the top measurement head or bottom measurement head is selected for providing the excitation beam into the sample, phase  13 . This is made e.g. with an optical switch. 
   In phase  14 , the emission filter is selected for the detector A. In this phase also the identification code of the corresponding emission filter is read and thus a correct type is verified. Either the top measurement head or the bottom measurement head is then selected in step  15  for receiving the emission A and for guiding the emission beam A into the detector A. The optical path is connected to the selected measurement head e.g. by controlling an optical switch. If two emissions are measured the emission filter is also selected for the detector B, steps  16  and  17 . In this phase also the identification code of the corresponding emission filter is read and thus a correct type is verified. Either the top measurement head or the bottom measurement head is selected in step  18  for receiving the emission B and guiding the emission beam into the detector B. The optical path can be connected to the selected measurement head also by controlling an optical switch. 
   If excitation or emission of the measurement is made from above the sample, i.e. the top measurement head is used, then the optical module of the top measurement head is selected and placed into the measurement location, phases  19  and  20 . If excitation or emission of the measurement is made from below the sample, i.e. the bottom measurement head is used, then the optical module of the bottom measurement head is selected and placed into the measurement location, phases  21  and  22 . According to the invention, the identification of optical modules are read, and thus the correct components are selected for use in the measurement. 
   After the optical paths have been selected, the first sample to be measured is selected, phase  23 . The selected sample is then measured,  24 , and the signals received from the detector(s) are processed to produce measurement result(s) for the measured sample, phase  25 . Samples are successively measured by repeating phases  23 – 26  until all samples have been measured. Finally the measurement results are displayed or printed. Preferably the filters and optical module(s) that have been used are also recorded together with the measurement results. This way the used optical components can be checked later if necessary. 
   One should note that several variations of the measurement process according to the invention can be applied. For example, the order of the process phases can be different from the one described above. Also, if an instrument without a bottom measurement head is used, the selection between top/bottom measurement head or selection of the optical module for the bottom measurement head are not required. 
   And if only one excitation source is available, a selection between excitation sources is not required. 
     FIG. 24  illustrates a flow diagram of an exemplary method according to the invention for optical measurement of a sample. In phase  41  an excitation beam is formed in an illumination source, and the excitation beam is filtered with an interference filter in phase  42  to include wavelength(s) for the excitation of two substances in the sample. In this phase also the identification code of the excitation filter is read and thus a correct type is verified. The filtered excitation beam is guided through a small aperture to an optical module according to the invention, wherein the beam is reflected, phase  43 . The excitation beam is then focused into the sample within a volume that is to be measured,  44 . The excitation beam may be an excitation pulse, succession of pulses or a continuous wave beam, depending on the type of measurement. 
   After the (fluorescent) label substances in the sample have been excited, they release emissions, which are received into the optical module according to the invention, phase  45 . The identification code of the optical module has been read and thus a correct type has been verified. The emissions may be in the form of bursts or continuous emissions depending on the excitation. In the optical module the emission beam may first transmit an excitation mirror, and the emission beams are then divided with a dichroic mirror into two emission beams e.g. according to their wavelength in phase  46 . The splitting may be performed in same optical module. 
   The first emission beam received from the first substance of the sample is first guided (focused) through an aperture of the optical module,  47 . The beam is then filtered in by transmitting the first emission beam and blocking other light, e.g. light with different wavelength, and finally the first emission beam is then guided to a first detector, phase  48 . Simultaneously with receiving the first emission, the second emission beam is received from the second substance of the sample, guided through the optical module and focused through an aperture of the optical module,  49 . The beam is then filtered by transmitting the second emission beam and blocking other light, e.g. light with different wavelength, and the filtered second emission is then guided to a second detector, phase  50 . The identification codes of the emission filters have been read and thus correct types have been verified. The emissions are then converted into electrical signals in the detectors, phase  51 , and the signals are processed in order to provide measurement results showing the quantity of the first and second substances within the sample, phase  52 . The types of the optical components are then recorded together with the measurement results. 
   One should note that the inventive method is not restricted to the measurement of two emissions of two substances, but there may be further means for splitting the emission into several emission beams and further detectors for measuring the emission beams. 
   Above, examples of a general measurement process and method were described. Next some typical measurements are described in more detail. In this description the use of an optical instrument according to  FIG. 3  is referred to. 
   FI and TRF Measurements 
   In a prompt photoluminescence, i.e. FI measurement, one excitation pulse is given for each sample to be measured. In a FI measurement an excitation filter and an emission filter are selected as was described above. A suitable optical module is also selected; the optical module may be a general-purpose module, or it may be a module that is especially designed for a determined label substance. 
   After a sample has been chosen for the measurement an excitation pulse is transmitted, and reference R 1  is read wherein R i  is the amount of light that has been used in the excitation of the label. The illumination reference is received from a reference detector  319 . Emission signals S 1   A  and S 1   B  are then read from the detectors. A correction factor for the signals is calculated on the basis of the illumination reference value. The long-term stability of the equipment is fixed to this amount of light when using a determined excitation filter and mirror block. 
   If several excitation pulses are used for one sample, the sequence is repeated and the results are summed or averaged. This leads to improved signal-to-noise ratio of the measurement. 
   A time resolved photoluminescence measurement, i.e. TRF measurement, is equal to the FI measurement except that several excitation pulses are formed for each sample and corresponding emissions are measured. The measurement signals and reference signals are read after each excitation pulse and signal corrections are calculated. Basic references are determined with standard solvents after the analyzer has been assembled. After receiving all emission signals from a sample, the results are preferably digitally integrated. Finally, a linear correction can be made for the digital signal using a reference. 
   Chemiluminescence Measurement 
   In a chemiluminescence measurement no excitation pulse is given. A separate detector can be used for the chemiluminescence measurement, if it is desirable to make chemiluminescence measurements simultaneously with a photoluminescence measurement. In this case the simultaneous chemiluminescence and photoluminescence measurements are made from different samples. However, if a simultaneous measurement is not required, same detector as used for photoluminescence measurements can be used for the chemiluminescence measurement. 
   An emission filter is not needed in a chemiluminescence measurement, so the filter slide can be moved outside the measurement beam. An optical module is selected according to the label; a TR module can be used, but a better measurement quality can be achieved with a block designed for the chemiluminescence measurement. The analogue gates or a digital window for the measurement period is set. After a sample is chosen a first period for measuring illumination is triggered. The length of the measurement period is e.g. 1 ms. Detected signals are read, further measurement periods are triggered, and the corresponding signals are read. The measurement periods are repeated for e.g. 1000 times, which gives 1 second for the total measurement time. Finally the measured signals are summed to achieve the result of the total measurement. 
   In this patent specification the structure of the components in an optical measurement instrument is not described in more detail as they can be implemented using the description above and the general knowledge of a person skilled in the art. 
   An optical instrument includes control means for performing the optical measurement process. The control of the measuring process in an optical measurement instrument generally takes place in an arrangement of processing capacity in the form of microprocessor(s) and memory in the form of memory circuits. Such arrangements are known as such from the technology of analyzers and relating equipment. To convert a known optical instrument into an equipment according to the invention it is necessary, in addition to the hardware modifications, to store into the memory means a set of machine-readable instructions that instruct the microprocessor(s) to perform the operations described above. Composing and storing into memory of such instructions involves known technology which, when combined with the teachings of this patent application, is within the capabilities of a person skilled in the art. 
   Above, an embodiment of the solution according to the invention has been described. The principle according to the invention can naturally be modified within the frame of the scope defined by the claims, for example, by modification of the details of the implementation and ranges of use. 
   The embodiments described above mainly relate to double emission measurements. However, even if the invention has special advantages when applied to double emission measurements, the invention can as well be applied in other types of measurements, such as single emission measurements. 
   It is also to be noted that the invention is not in any way restricted to the applications of the photoluminescence measurement. An experienced user is able the use the present invention also in other measurement technologies in common use in biochemical laboratories. For example, e.g. reflectance, turbidimetric and nephelometric measurement can be measured using a fluorescent measurement technology with the exception that the emission filter must be a gray filter. The different types of filters can then automatically be identified according to the present invention.