Patent Description:
In the field of microscopy, light sources such as a light-emitting diodes (LEDs) are used to illuminate a sample to be imaged. In order to shield the sample from the illumination light when the light source is switched on, the light source is often followed by a light blocking shutter that can be moved into the illumination light path and retracted therefrom.

For a number of reasons, it may be important to measure the intensity of the illumination light applied to the sample. For example, knowing the illumination light intensity is crucial when sensitive biological samples need to be protected from excessive light exposure. Furthermore, the illumination light intensity can be used to determine an aging condition of the light source in the context of predictive maintenance.

In order to detect the illumination intensity in conventional microscopes, light sensors such as photodiodes are used. Usually, the light sensor is positioned near but outside an illumination light path to prevent the light sensor from blocking the light propagating towards the sample. Accordingly, the light sensor measures only off-axis light such as scattered light. As a result, only a small portion of the illumination light intensity is measured which may work well for high light intensities. However, low light intensities cannot be measured accurately.

There is an alternative solution wherein the microscope comprises an optomechanical component such as a deflection mirror that is movable into the illumination light path to deflect the illumination light onto the light sensor located outside the illumination light path. However, providing an additional optomechanical element is technically complex and disadvantageous in term of costs and installation space. Documents <CIT> and <CIT> disclose known light source modules for a microscope.

It is therefore an object to provide a light source module for a microscope and a method that allow the intensity of illumination light emitted from a light source to be easily yet accurately detected.

The aforementioned object is achieved by the subject-matter of the independent claims. Advantageous embodiments are defined in the dependent claims and the following description.

A light source module for a microscope comprises a light source unit configured to emit illumination light along an illumination light path, at least one light blocking shutter configured to be moved into and out of the illumination light path, and at least one light sensor configured to detect an intensity of the illumination light propagating along the illumination light path. The at least one light sensor is integrated with the at least one light blocking shutter to be moved therewith into and out of the illumination light path.

According to the solution presented herein, a light sensor such as a photodiode is integrated with a light blocking shutter which can be inserted into and retracted from an illumination light path. Therefore, it is possible to detect the intensity of the illumination light emitted by the light source unit with high precision, even if the intensity is low. This is in contrast to existing solutions where a light sensor is fixedly arranged outside the illumination light path so that the light sensor is only able to detect off-axis light such as scattered light, rendering the measurement inaccurate at low intensities. The light sensor inserted into the illumination light path is preferably arranged so that its light receiving surface lies on the optical axis defining the illumination light path.

Furthermore, the light sensor is part of the movable light blocking shutter which is included in the microscope anyway. Therefore, it is not necessary to provide additional components that are specifically designed to enable high-precision intensity measurement. This is advantageous in term of costs and installation space.

The light blocking shutter may be formed from a plate-shaped component, in particular in form of circuit board in which the light sensor is integrated. For example, control elements that are needed anyway can be accommodated on the printed circuit board to save space.

In a preferred embodiment, the light source unit comprises a plurality of light sources configured to emit a plurality of light components, wherein the light source module further comprises a beam combining device configured to combine the plurality of light components to the illumination light. Preferably, the light source is configured to emit the plurality of light components with different wavelengths. The beam combining device may comprise mirrors and/or dichroic mirrors configured to merge the different light components as desired.

The at least one light blocking shutter may comprise a single light blocking shutter located along the illumination light path downstream of the beam combining device. A single shutter can be used to efficiently measure the intensity of an illumination light beam combined from multiple light components.

In addition, or alternatively, the at least one light blocking shutter may comprise a plurality of light blocking shutters corresponding to the plurality of light sources, wherein each light blocking shutter is located along the illumination light path upstream of the beam combining device and immediately downstream of the light source which is associated with this light blocking shutter. Using multiple shutters allows the light intensities emitted by multiple light sources independently in an efficient manner.

The microscope may comprise at least one driving unit which is configured to move the at least one light blocking shutter into and out of the illumination light path. Using a driving unit to insert the light blocking shutter into the illumination light path and to retract therefrom, facilitates the operation of the light source module. For example, the driving unit may comprise a motor such as a step motor without being limited thereto. As an exemplary alternative, an electromechanical actuator such as a solenoid may be used to move the light blocking shutter into and out of the illumination light path.

The microscope may further comprise a controller which is configured to control the light sensor integrated with the light blocking shutter and/or the light unit source unit. In case that the light blocking shutter is formed by a circuit board, the controller may be integrated with the circuit board which is advantageous in terms of costs and installation space.

In a preferred embodiment, the controller is configured to cause the light sensor to detect the intensity of the illumination light propagating along the illumination light path and to cause the light source unit to adjust the intensity of the emitted illumination light depending on the detected intensity. Such an embodiment can be advantageously used to protect light sensitive samples from excessive light exposure. The controller may further be configured to obtain calibration data and to cause the light source unit to adjust the intensity of the emitted illumination light based on the calibration data.

According to another aspect, a method for illuminating a sample by means of a light source module in a microscope is provided. The method comprises the following steps: emitting illumination light along an illumination light path onto the sample by means of a light source unit of the light source module; detecting an intensity of the illumination light propagating along the illumination light path by means of at least one light sensor which is integrated with at least one light blocking shutter of the light source module, wherein the at least one light blocking shutter is configured to be moved into and out of the optical path.

A detection of the intensity of the illumination light may be controlled according to the following sequence of steps: In a first step, the light blocking shutter is moved into the illumination light path with the light source unit turned off. In a second step, the light source unit is turned on to emit the illumination light along the illumination light path. In a third step, the intensity of the illumination light is detected by means of the light sensor integrated with the light blocking shutter. In a fourth step, the light source unit is turned off to stop the emission of the illumination light. In a fifth step, the light blocking shutter is moved out of the optical path.

According to a preferred embodiment, a predictive maintenance procedure may be executed by controlling the light source unit to emit the illumination light with a maximum intensity; comparing the intensity detected by means of the light sensor to a pre-stored nominal intensity, and generating predictive maintenance information based on a result of the comparison. For example, predictive maintenance information about the light source unit can be obtained, in particular information about aging phenomena, in case that the detected light intensity is significantly lower than the pre-stored nominal intensity.

According to another aspect, a method for calibrating the light source module is provided. The calibration method comprising the following steps: emitting the illumination light by means of the light source unit along the illumination light path with the at least one light blocking shutter being moved out of the illumination light path; detecting the intensity of the illumination light propagating along the illumination light path by means of a reference light sensor device; varying a power supplied to the light source unit until the intensity of the illumination light detected by the reference light sensor device is equal to a predetermined reference intensity; storing a value of the power, at which the illumination light detected by reference light sensor device is equal to the reference intensity, as a reference power value; moving the light blocking shutter into the illumination light path and measuring the intensity of the illumination light, which is emitted by the light source unit at the reference power value, by means of the light sensor integrated with the light blocking shutter as a reference intensity value; and determining a calibration characteristic based on the reference power value and the reference intensity value.

The obtained calibration characteristic is particularly advantageous to control the light source module in a range of lower light intensities where the characteristic often proves to be non-linear. This calibration may be performed for each light source module of an entire production series. The calibration characteristic may be stored in the respective light source module and can later be used when operating the light source module.

<FIG> and <FIG> are block diagrams showing a microscope <NUM> according to an embodiment. The microscope <NUM> may be implemented as an inverted microscope without being limited thereto. It is to be noted that <FIG> and <FIG> show only those components of the microscope <NUM> which are helpful to understand the operating principle of the solution presented herein. Needless to say, that the microscope <NUM> may include additional components not explicitly shown in the block diagrams of <FIG> and <FIG>.

As shown in <FIG> and <FIG>, the microscope <NUM> comprises a light source unit <NUM> which emits illumination light <NUM> along an optical axis O defining an illumination light path <NUM>. The light source unit <NUM> may include a single light source or a plurality of separate light sources as explained below with reference to <FIG> and <FIG>. For example, the light source(s) may be implemented as LED(s). The illumination light path <NUM> is directed towards a sample <NUM> held by a transparent sample carrier <NUM> that is arranged on a microscope stage <NUM>. According to the inverted configuration, the microscope <NUM> comprises an objective <NUM> that images the sample <NUM> from below the microscope stage <NUM> through a stage opening <NUM> onto an image sensor (not shown in <FIG> and <FIG>).

The microscope <NUM> further comprises a light blocking <NUM> that is configured to be moved into and out of the illumination light path <NUM>. The moving direction of the light blocking shutter <NUM> may be perpendicular to the optical O as indicated by a double arrow in <FIG> and <FIG>, respectively. The microscope <NUM> may have a driving unit <NUM> such as a motor, for example as a step motor, which moves the light blocking shutter <NUM> into and out of the illumination light path <NUM>. Alternatively, the driving unit <NUM> may be formed by an electromechanical actuator such as a solenoid. The light blocking shutter <NUM> serves to shield the sample <NUM> from the illumination light <NUM> when the light source unit <NUM> is turned on and emits the illumination light <NUM> along the illumination light path <NUM>. Thus, <FIG> shows a first operating state in which the illumination light <NUM> emitted from the activated light source unit <NUM> is prevented from reaching the sample <NUM> by the light blocking shutter <NUM>. In contrast, <FIG> shows a second operating state in which light blocking shutter <NUM> clears the illumination light path <NUM> so that illumination light <NUM> emitted from the light source unit <NUM> is incident on the sample <NUM>.

The microscope <NUM> comprises a light sensor <NUM> which is adapted to detect the intensity of the illumination light <NUM> propagating along the illumination light path <NUM>. More specifically, the light sensor <NUM> is integrated with or arranged at the light blocking shutter <NUM> and thus movable therewith into and out of the illumination light path <NUM>. Accordingly, the light blocking shutter <NUM> and the light sensor <NUM> may form an integrated unit which can be inserted into the illumination light path <NUM> to selectively prevent the illumination light <NUM> from reaching the sample <NUM> and to measure the intensity of the illumination <NUM> at the same time. For example, the light blocking shutter <NUM> may be formed by a circuit board, and the light sensor <NUM> may be mounted on a surface of the circuit board facing the light source unit <NUM> that emits the illumination light <NUM>. This enables a light sensitive surface of the light sensor <NUM> to detect a significant portion of the illumination light <NUM> which would be incident on the sample <NUM> when the illumination light path <NUM> is cleared by retracting the light blocking shutter <NUM> therefrom.

As a result, the intensity of the illumination light <NUM> can be measured with high accuracy, even if the intensity is low. This distinguishes the solution presented herein from conventional systems in which the light sensor is fixed outside the illumination light path so that the light sensor is dependent on detecting only off-axis light such as scattered light, which makes the measurement inaccurate at low intensities.

In addition, as the light sensor <NUM> is integrated with the light blocking shutter <NUM>, which is a component already present in the microscope <NUM>, a highly accurate intensity measurement can be achieved without having to provide additional components such as an optomechanical used in existing microscopes. This is advantageous in term of costs and installation space.

Although the light blocking shutter <NUM> is illustrated in <FIG> and <FIG> as a single shutter, it is to be noted that the microscope <NUM> may also have multiple, preferably identical, light blocking shutters, in particular in case that the light source unit <NUM> includes multiple light sources. In such a case, each light blocking shutter may be assigned in a one-to-one configuration to a specific light source. It should be noted in particular that all embodiments disclosed herein refer to both a single light source configuration and a multiple light source configuration, unless explicitly stated otherwise. This applies in particular to the calibration method explained below.

According to the embodiment shown <FIG> and <FIG>, the microscope <NUM> includes a controller <NUM> which is adapted to control operations of the light source unit <NUM>, the motor <NUM> and the light sensor <NUM> integrated with the light blocking shutter <NUM>. In particular, the controller <NUM> may cause the light sensor <NUM> to measure the intensity of the illumination light <NUM>. For this purpose, the controller <NUM> outputs a drive signal to the motor <NUM>. Based on the drive signal, the motor <NUM> moves the light blocking shutter <NUM> together with the light sensor <NUM> from a non-operating position shown in <FIG>, in which the light blocking shutter <NUM> is retracted from the illumination light path <NUM>, into an operating position shown in <FIG>, in which the light blocking shutter <NUM> is inserted in the illumination light path <NUM>. Subsequently, the controller <NUM> turns the light source unit <NUM> on, if it has not already done so, and causes the light sensor <NUM> to perform a measurement of the intensity of the illumination light <NUM> emitted from the light source unit <NUM>. In turn, the controller <NUM> receives a detection signal from the light sensor <NUM>.

The light source unit <NUM>, the light blocking shutter <NUM> with its integrated light sensor <NUM>, the motor <NUM>, and the controller <NUM> are included in a light source module <NUM>. The light source module <NUM> may be configured as an essentially self-contained unit of the microscope <NUM>. For example, the illumination light <NUM> output from the light source module <NUM> may be transmitted through an optical fiber to the sample <NUM>.

<FIG> is a block diagram showing an embodiment of the light source module <NUM> in which the light source unit <NUM> comprises multiple light sources 102a, 102b, 102c, and 104d. For simplicity, components of the microscope <NUM>, which are arranged in the illumination light path <NUM> downstream of the light module <NUM>, are omitted in <FIG>.

The multiple light sources 102a, 102b, 102c, 102d may be configured to emit a plurality of light components 104a, 104b, 104c, 104d, respectively. The light sources 102a, 102b, 102c, 102d may be LEDs of different colors. Specifically, the LEDs may generate illumination light of different wavelengths adapted to excite various fluorophores included in the sample to emit fluorescent light. According to the embodiment shown in <FIG>, the multiple light components 104a, 104b, 104c, 104d emitted by the light sources 102a, 102b, 102c, 102d are collinearly combined into a resulting light beam which eventually illuminates the sample. To this end, the light source module <NUM> may comprise a beam combining device <NUM> that is adapted to merge the light components 104a, 104b, 104c, 104d to light beam irradiated onto the sample. The beam combining device <NUM> may comprise multiple components which serve to couple the different light components 104a, 104b, 104c, 104d sequentially into the illumination light path <NUM> in which the combined light beam ultimately propagates to the sample.

More specifically, the beam combining device <NUM> includes a deflection mirror 326a which faces the first light source 102a and reflects the first light component 104a emitted therefrom into the illumination light path <NUM>. In addition, the beam combining device <NUM> includes a first dichroic beam splitter 326b facing the second light source 102b. The first dichroic beam splitter 326b reflects the second light component 104b emitted by the second light source 102b into the illumination light path <NUM> and transmits the first light component 104a already propagating along the illumination light path <NUM>. In addition, the beam combining device <NUM> includes a second dichroic beam splitter 326c facing the third light source 102c. The second dichroic beam splitter 326c reflects the light component 104c emitted by the third light source 102c into the illumination light path <NUM> and transmits the light components 104a and 104b already propagating along the illumination light path <NUM>. In addition, the beam combining device <NUM> includes a third dichroic beam splitter 326d facing the fourth light source 102d. The third dichroic beam splitter 326d reflects the light component 104d emitted by the fourth light source 102d into the illumination light path <NUM> and transmits the light components 104a, 104b, and 104c already propagating along the illumination light path <NUM>.

According to the embodiment shown <FIG>, the light blocking shutter <NUM> is formed by a single shutter which is arranged in the illumination light path <NUM> downstream of the beam combing device <NUM>, in particular downstream of the last dichroic beam splitter 326d. As explained above with reference to <FIG> and <FIG>, the light blocking shutter <NUM> including the light sensor <NUM> is movable into and out of the illumination light path <NUM> by means of the motor <NUM> that is driven by the controller <NUM>. In addition to a microcontroller (µC) <NUM>, the controller <NUM> may include a motor driver <NUM> connected to motor <NUM>.

Instead of or in addition to the single light blocking shutter <NUM>, as shown by dashed lines in <FIG>, it is also possible to provide multiple light blocking shutters 318a, 318b, 318c, and 318d with integrated light sensors. In that case, each light blocking shutter 318a, 318b, 318c, and 318d may be assigned to one of the multiple light sources 102a, 102b, 102c, 102d. In particular, each light blocking shutter 318a, 318b, 318c, 318d may be located along the illumination light path <NUM> upstream of the beam combining device <NUM> and immediately downstream of the respective light source 102a, 102b, 102c, 102d. In other words, each light blocking shutter 318a, 318b, 318c, 318d is positioned with the light receiving surface of its light sensor facing the associated light source 102a, 102b, 102c, 102d in order to detect only illumination light emitted from that light source. As noted above, the light blocking shutters 318a, 318b, 318c, 318d may preferably be substantially identical components.

The controller <NUM> may further comprise multiple light source drivers (amplifiers) 332a, 332b, 332c, and 332d, each of which being coupled to one of the multiple light sources 102a, 102b, 102c, and 102d. Thus, each light source 102a, 102b, 102c, 102d is controlled by the microcontroller <NUM> and the associated light source driver. Furthermore, a personal computer (PC) <NUM> may be provided enabling a user to operate the configuration shown in <FIG>. For example, based on desired illumination light intensities input by the user via the PC <NUM>, the microcontroller <NUM> outputs control signals to the light source drivers 332a, 332b, 332c, 332d. Then, the light source drivers 332a, 332b, 332c, 332d cause the light sources 102a, 102b, 102c, 102d to emit the different light components 104a, 104b, 104c, 104d with the desired light intensities. Furthermore, the light sensor integrated with the light blocking shutter <NUM> and/or the light sensors integrated with the light blocking shutters 318a, 318b, 318c, 318d detect the respective light intensities and output detection signals to the microcontroller <NUM> which processes the received detection signals.

As explained above, the light sources 102a, 102b, 102c, and 102d can be used simultaneously in order to create a resulting light beam including all wavelengths provided by the light sources. Alternatively, it is also possible to use only one or some of the light sources 102a, 102b, 102c, and 102d at a time.

<FIG> is a plan view showing a structural implementation of the light source module <NUM> shown in <FIG>. In particular, <FIG> serves to illustrate a positional relationship of the light sources 102a, 102b, 102c, 102d, the beam combining device <NUM>, and the light blocking shutter <NUM> with the integrated light sensor <NUM> within the light source module <NUM>. It goes without saying that the configuration shown in <FIG> is to be understood as an illustrative example only. Various other structural implementations are conceivable.

The light source module <NUM> comprises a module casing <NUM> which houses the aforementioned module components. As can be seen in <FIG>, the deflection mirror 326a and the dichroic beam splitters 326b, 326c, 326d of the beam combining device <NUM> are arranged to be directly opposite the associated light source 102a, 102b, 102c, and 102d, respectively. Each of these components 326a, 326b, 326c, 326d of the beam combining device <NUM> is arranged at angle to the optical axis O such that the illumination light reflected by the respective component propagates along the optical axis O defining the illumination path <NUM>. <FIG> also shows that the light sensor <NUM> formed on the light blocking shutter <NUM> is preferably positioned on the optical axis O when the light blocking shutter <NUM> is its operating state, which means that it is inserted into the illumination light path <NUM>. In that state, the light blocking shutter <NUM> covers an output lens <NUM> which is optically coupled to an optical fiber <NUM> so that the illumination light is prohibited from reaching the output lens <NUM>. If the light blocking shutter <NUM> is retracted from the illumination light path <NUM>, the illumination light reaches the output lens <NUM> and is transmitted through the optical fiber <NUM> towards the sample.

<FIG> are different views of the light blocking shutter <NUM> according to an embodiment. The light blocking shutter <NUM> may be formed by a plate-shaped component, in particular a circuit board <NUM>, as already mentioned above.

As shown in the perspective view of <FIG>, the light sensor <NUM> is mounted on a front surface <NUM> of the light blocking shutter <NUM>, the front surface <NUM> facing the light source unit <NUM>. On an opposite rear surface <NUM>, the motor <NUM> is coupled to the light blocking shutter <NUM> as shown in <FIG>. Being formed as circuit board, the light blocking shutter <NUM> may include a plurality of electronic components <NUM> such ICs as shown in <FIG>. The motor <NUM> may be configured to pivot the light blocking shutter <NUM> into and out of the illumination light path via a rotatable shaft <NUM> which coupled to a mounting portion <NUM> arranged on the rear surface <NUM> of the light blocking shutter <NUM> as shown in <FIG>.

<FIG> is a flow diagram showing a method for detecting the intensity of the illumination light <NUM> according to an embodiment. With reference to <FIG>, it is assumed that the intensity of the illumination light <NUM> is measured by a single light blocking shutter such as the shutter <NUM> shown in <FIG>. However, the method can also be applied for measuring the intensities of multiple illumination components emitted by multiple light sources. In this case, a configuration with multiple light blocking shutters may be used as indicated in <FIG> by the shutters 318a, 318b, 318c, 318d.

Hereinafter, it is assumed that the light source unit <NUM> is turned off at the beginning of the method shown in <FIG>. Thus, in S1, the controller <NUM> causes the motor <NUM> to move the light blocking light shutter <NUM> with the integrated light sensor <NUM> turned off from a retracted position into the illumination light path <NUM>.

Subsequently, in step S2, the controller <NUM> turns the light source unit <NUM> on to emit the illumination light <NUM> along the illumination light path <NUM> with the light sensor <NUM> formed on the light blocking light shutter <NUM> being arranged therein to receive the emitted illumination light <NUM>.

In step S3, the controller <NUM> causes the light source unit <NUM> to emit the illumination light <NUM> with a desired intensity which may be specified by the user, for example by a corresponding input on the PC <NUM>.

In step S4, the controller <NUM> causes the light sensor <NUM> integrated with the light blocking shutter <NUM> to measure the intensity of the illumination light incident on the light receiving surface of the light sensor <NUM>.

In step S5, the controller <NUM> turns the light source unit <NUM> off. Finally, in step S6, the controller <NUM> causes the motor <NUM> to retract the light blocking light shutter <NUM> from the illumination light path <NUM>.

The method described above can be used advantageously to protect the sample <NUM> from excessive light exposure which is important, for example, in experiments involving biological samples that are known to be light sensitive. In particular, it is possible to control the light source unit <NUM> during the experiment depending on the intensity measured by the light sensor <NUM>.

Furthermore, the light intensity measurement integrated into the light blocking shutter <NUM> can be used for predictive maintenance. For example, in step S3 of the method shown in <FIG>, the light source unit <NUM> can be controlled to emit the illumination light <NUM> with maximum intensity. The intensity of the illumination light <NUM> detected by the light sensor <NUM> in step S4 may then be compared to a pre-stored nominal intensity which has been determined at the beginning of the lifetime of the light source unit <NUM>. In this manner, predictive maintenance information about the light source unit <NUM>, in particular information about aging phenomena, can be obtained. It is to be noted that a comparison of the light intensity detected by the light sensor <NUM> to a pre-stored nominal intensity is not limited to a single pair of intensity values. Rather, multiple comparative measurements may be performed as indicated by the dashed loop between steps S3 and S4 in <FIG>, for example in the context of predictive maintenance, but also in the context of calibration, as explained hereinafter.

A calibration of the light source unit <NUM> may be implemented based on a series of light intensity measurements established by repeatedly executing steps S3 and S4 in <FIG>. For example, it is assumed that one of the LEDs 102a, 102b, 102c, 102d is to be calibrated using its associated light blocking shutter 318a, 318b, 318c, 318d with the integrated light sensor.

As an example, assume a production series including products such as the LEDs mentioned above to be calibrated in the manufacturing stage. Furthermore, assume that a maximum permissible intensity of the emitted illumination light is specified for this LED type. The entire operating range of the LED type is assumed to be <NUM>% to <NUM>%, wherein the value <NUM>% is normalized to the maximum permissible light intensity. Then, a transfer of the value of <NUM>% to the entire production series can be achieved if all LEDs of the production series are calibrated such that all LEDs obtain at least one identical reference point.

For such a calibration, an external reference sensor device <NUM> may be used during production as indicated in <FIG> by dashed lines. The external reference sensor device <NUM> is configured to measure the intensity of the light emitted by the LED with absolute accuracy. For example, the external reference sensor device <NUM> may be coupled to an output of the LED-shutter module <NUM> including the LED(s) to be calibrated in order to measure the illumination light intensity emitted by the LED(s) with absolute accuracy.

Firstly, the light blocking shutter including the light sensor is retracted from the illumination light path <NUM>. Subsequently, an electrical LED power energizing the LED to emit the illumination light is adjusted, and the corresponding intensity of the illumination light emitted by the LED is measured by means of the external reference sensor device <NUM>. This adjustment process is carried out until the external reference sensor device <NUM> measures the maximum permissible light intensity which corresponds to a first LED power. After that, the light blocking shutter including the light sensor is moved into the illumination light path <NUM>, and the intensity of the illumination light emitted from the LED is measured by the light sensor. The measured light intensity is stored. As a result, a first pair of measured values is obtained, this first pair consisting of the first LED power mentioned above and the light intensity measured by the light sensor integrated with the light blocking shutter at <NUM>%. A further light intensity measurement by means of the external reference sensor device <NUM> is not necessary for calibrating the specific light source module <NUM>.

Subsequently, a measurement series is performed iteratively, in which the illumination light intensity is set in a desired granularity and the resulting LED power is stored. Accordingly, the measurement series sets the adjusted values of the LED power in relation to the measured values of the illumination light intensity. This results in a characteristic allowing the adjustable LED power to be exactly assigned to the desired light intensity, which is particularly advantageous in a range of lower light intensities where the characteristic curve is not linear. This calibration process is performed for each light source module of the production series to create a calibration characteristic that is specific for this light source module. The calibration characteristic is stored in the respective light source module and can later be used when operating the light source module. As a result, all modules of production series are calibrated.

Such a calibration process results in a light source module which is capable of emitting illumination with reproducible light intensities. Accordingly, the user is enabled to repeat an experiment reliably at any time. Furthermore, reproducibility is not only given for a specific light source module but to the whole production series. Thus, the user can perform the same experiment with the same light intensity at different locations. This is an important aspect in the field of research, as reproducibility in microscopic imaging depends on many factors.

Claim 1:
A light source module (<NUM>) for a microscope (<NUM>), comprising:
a light source unit (<NUM>) configured to emit illumination light (<NUM>) along an illumination light path (<NUM>),
at least one light blocking shutter (<NUM>) configured to be moved into and out of the illumination light path (<NUM>), and
at least one light sensor (<NUM>) configured to detect an intensity of the illumination light (<NUM>) propagating along the illumination light path (<NUM>),
wherein the at least one light sensor (<NUM>) is integrated with the at least one light blocking shutter (<NUM>) to be moved therewith into and out of the illumination light path (<NUM>).