CN111965805A

CN111965805A - Illumination device and illumination method for optical microscope

Info

Publication number: CN111965805A
Application number: CN202010407271.4A
Authority: CN
Inventors: 马丁·穆勒; 布莱斯·安东·莫法特
Original assignee: Carl Zeiss Microscopy GmbH
Current assignee: Carl Zeiss Microscopy GmbH
Priority date: 2019-05-20
Filing date: 2020-05-14
Publication date: 2020-11-20
Also published as: DE102019113360A1

Abstract

An illumination device for an optical microscope, comprising a light source (10), a current regulating device (20) for regulating a current (i1) flowing through the light source (10), and a measuring resistor arrangement (30), wherein a voltage drop (U1) across the measuring resistor arrangement (30) is dependent on the current (i1) flowing through the light source (10). The current regulating device (20) is configured to regulate the current (i1) flowing through the light source (10) based on a voltage drop signal (Ue) related to the voltage drop (U1) across the measuring resistor arrangement (30). The measuring amplifier circuit (50) with adjustable gain is configured to output an amplified output signal (Ua) dependent on the voltage drop (U1) as a voltage drop signal (Ue) to the current regulating device (20).

Description

Illumination device and illumination method for optical microscope

Technical Field

The invention relates to an illumination device according to the preamble of claim 1, an optical microscope according to the preamble of claim 13 and an illumination method.

Background

A common illumination device for an optical microscope includes a light source, such as one or more LEDs. The luminance of the light source is set by a current (hereinafter referred to as "flowing current of the light source").

In optical microscopy, the desired brightness level may vary over a wide range, in particular depending on the microscopy method currently used or the nature of the sample currently being examined. Thus, the current level required by the light source also varies over a large range. Furthermore, in particular for camera-based observations, it is advantageous if the luminous intensity and thus the current level can be adjusted as constantly as possible over time, so that the successively recorded camera images are comparable to one another or can be easily combined together by calculation.

The general lighting device comprises a current regulating means for regulating the current flowing through the light source. Furthermore, a measuring resistor device is used, the voltage drop across which depends on the current flowing through the light source. In particular, the current through the measuring resistance means may be equal to the flowing current or dependent on the flowing current in a known manner. The current regulating device is configured to regulate the flowing current of the light source based on a voltage drop signal related to the voltage drop over the measuring resistance arrangement.

Similarly, in a general illumination method for optical microscopes, the through-current of the light source is set by means of a current regulation device. A measuring resistance means is provided and the voltage drop across it depends on the current flowing through the light source. The current regulating device regulates the through current of the light source based on a voltage drop signal related to the voltage drop over the measuring resistor arrangement.

By means of such a closed-loop control, the current flowing through and thus the luminous intensity can be set to a value which is particularly constant over time.

However, in the case of low light emission intensity, the flowing current is so small that sufficiently good current resolution cannot be obtained. To solve this problem, patent DE 102012210905B 4 proposes the use of two current control loops. Each current control loop has a dedicated measuring resistance device, the resistance levels of which differ from each other. See R1 and R2 in fig. 2 of patent DE 102012210905B 4. One current control loop is used for operation at high luminous intensity, while the other current control loop is used in case of low luminous intensity. This has the disadvantage that for both current control loops a large number of hardware components have to be provided twice. In addition, two set point encoders must be provided, or in the case of a single set point encoder, the latter must be supplemented by a switching device in order to switch between the set points of the two current control loops. In the exemplary embodiment shown in fig. 2 by dashed lines in battle force DE 102012210905B 4, the voltage drop across the respective measuring resistor is not provided directly as a voltage drop signal at the current regulating device, but rather is amplified before being provided to the current regulating device. In this case, the necessary amplifier must also be provided twice for both control loops.

Furthermore, DE 102012207217 a1 (see fig. 2 therein) discloses a current regulation of a light source, wherein a single current control loop is used, and the switch is adjustable whether a single measuring resistor or two parallel measuring resistors are used to capture the flowing current. However, the internal resistance of the switch must also be properly considered, otherwise the result can be tampered with.

DE 102014208424 a1 discloses an illumination device for an optical microscope, in which the current of a light source to be set is set by means of a calibration table.

The object of the present invention is to provide an illumination device for an optical microscope, a corresponding optical microscope and an illumination method which make it possible to set the luminous intensity as precisely as possible over a large area.

This object is achieved by an illumination device having the features of claim 1, an optical microscope having the features of claim 12 and an illumination method having the features of claim 13.

Disclosure of Invention

Advantageous variants of the illumination device according to the invention, of the optical microscope according to the invention and of the illumination method according to the invention are the subject matter of the dependent claims and will be explained additionally in the following description.

In a lighting device of the above-mentioned type, there is a measuring amplifier circuit with adjustable gain according to the invention. The measuring amplifier circuit is configured to output an amplified output signal as a voltage drop signal to the current regulating device, the amplified output signal being dependent on the voltage drop across the measuring resistance means. Similarly, in the above-mentioned type of lighting method, an amplified output signal depending on the voltage drop is generated by means of a measuring amplifier circuit with adjustable gain, wherein different gains are set for different levels of the flowing current; thus, an amplified output signal is provided as a voltage drop signal at the current regulating device.

The voltage dropped at the measuring amplifier circuit (or the voltage associated therewith) is thus amplified and, if necessary, output to the current regulation device by way of further processing steps. Thus, it is possible to avoid the second current control loop as in patent DE 102012210905B 4, or the use of an additional measuring resistor as in patent DE 102012207217 a 1. Instead, in particular, the same measuring resistance or the same measuring resistance can always be used, irrespective of the illumination intensity of the currently provided light source. This reduces possible errors and the expenditure on the apparatus can advantageously also be low. The proper signal amplitude is achieved by a variable gain factor, so that the subsequent disturbing influence in the wire is less important. Thus, at both low and high current levels, a high resolution of the flowing current is provided which is required to be considered.

In a variant of the invention, the resistance value of the measuring resistor device is selected to be constant, independently of the current flowing through the light source. In contrast to the prior art which was first proposed, the resistance value is not modifiable or switchable here, and it is also not possible to select between different resistance values. Thus, potential errors and inaccuracies associated with switching when measuring resistance are avoided. To the extent that switches are used in the present invention, as described in more detail below, the switches should not be arranged in such a way that the light source passes a potentially small flow of current therethrough.

An electronic control means may be provided and may be configured to adapt the gain of the measurement amplifier circuit based on the set brightness/illumination intensity of the light source. The control device may be configured in such a way that it sets a higher gain at a lower brightness (i.e. at a smaller flowing current). The desired brightness is selected or set by the user or software, for example for automatic image recording. This selection may be used by the control device to set the gain as described. Alternatively, the magnitude of the amplified output signal of the measurement amplifier circuit may also be used as a measure to determine whether the current saturation gain factor should be changed.

The electronic control means may be configured to send a set value to the current regulating device that depends on the desired brightness of the light source. In particular, the current regulating device may comprise an operational amplifier, which provides the set value at a first input thereof and the voltage drop signal (i.e. the amplified output signal of the measuring amplifier circuit or a voltage dependent thereon) at a second input thereof. The output of the operational amplifier, hereinafter referred to as "control command", can now control the flow of current, for example by means of a transistor through which the flow of current is controlled by means of the control command.

Thus, the control command of the current regulating device is generated based on the set value and based on the amplified output signal of the measuring amplifier circuit. Thus, the control device may be configured to set the setting value also based on the currently set gain of the measurement amplifier circuit. In the related art, the control device sets the setting value based on the desired brightness, whereas in the presently described variation of the present invention, the control device specifies the effect of the gain change on the setting value to be set using a function or table.

In particular, the setting value may be selected not only according to the desired brightness of the light source, but also based on the gain of the measurement amplifier circuit provided for the desired brightness. For example, which gain of the measuring amplifier circuit is used for the brightness to be set can be stored in a memory. Therefore, when changing the desired luminance, the setting value is adjusted based on the gain to be set for this luminance, not based on the previously set gain, for example.

In principle, the measuring amplifier circuit may have any design, as long as this makes it possible to adjust the different gains (gain factors) in a discrete or continuous manner.

As an example, the measurement amplifier circuit may comprise at least two measurement amplifiers and be configured (in particular by a multiplexer) to selectively set which measurement amplifier or amplifiers participate in outputting the amplified output signal as a voltage drop signal to the current regulating device. In this case, the individual measurement amplifiers may have a fixed gain factor (at a given operating voltage), as a result of which the choice of the currently used measurement amplifier or amplifiers effects a change in the resulting gain factor.

Thus, the measuring amplifier or measuring amplifiers may be arranged in parallel with each other. The parallel-connected measurement amplifiers may have different gains. Alternatively, a different number of measuring amplifiers can also be connected in series on the parallel branches, so that all measuring amplifiers can also have the same gain. Now it is possible to select which of the parallel connected measuring amplifiers sends the amplified output signal to the current regulating device, for example by means of a multiplexer.

Alternatively, the measurement amplifier or amplifiers may be connected in series. For example, the multiplexer now makes it possible to select the measuring amplifier connected in series and to provide the output signal from this as a voltage drop signal at the current regulating device. Thus, each measurement amplifier in the series may be connected to a multiplexer. The switching state of the multiplexer selects how many measuring amplifiers in series are used. The advantage of the series arrangement is that only a single measuring amplifier is connected to the measuring resistor arrangement, thus causing potential disturbances in the measuring resistor arrangement, whereas in the case of the above-described parallel arrangement, a plurality of measuring amplifiers may have a disturbing influence on the measuring resistor arrangement.

In contrast, a parallel arrangement (in which one measurement amplifier is arranged in each parallel branch) has the following advantages: the output signal is generated by a single measurement amplifier (rather than by multiple measurement amplifiers as in a series circuit), which may be advantageous in view of the accuracy of the output signal.

In the case of two measuring amplifiers connected in series, the gain factor of the backward measuring amplifier can be in particular between 2 and 20. In the case of a low brightness, the cause of the high level of the measurement signal relative to the brightness is amplified. Within the above range, the measurement current can be captured with high resolution within the commonly employed luminance range. In case the gain factor is smaller than 2, it is not always possible to cover the desired brightness range, whereas a factor larger than 20 would thus result in an excessively high output signal and a setting value to be selected accordingly. Similarly, in the case of measuring amplifiers connected in parallel, the gain factor of one measuring amplifier is preferably 2 to 20 times greater than the gain factor of the other measuring amplifier.

The measurement amplifier circuit may also be formed as or include an integrated circuit configured to set a certain gain based on the drive signal. Thus, an amplifier with an integrated interface for setting the gain, such as the chip LTC6915IC of an analog device, may be used, with a digital SPI interface for setting the gain. The amplifier may be designed to provide two or more selectable discrete amplification factors.

In the case of a further variant embodiment, the measuring amplifier circuit comprises an instrumentation amplifier with an adjustable resistance for setting the gain. For example, chip LT1167IC may be used as an instrumentation amplifier, while chip AD5241IC may be used as an adjustable resistor. This allows, for example, a plurality of discrete resistance values, and thus discrete gain factors, to be set, depending on the design.

The optical microscope according to the invention comprises the described illumination device for illuminating the sample, a light detector for measuring detection light, and an objective for guiding detection light from the sample to the light detector. Depending on the configuration, the objective lens may also be used to direct the illumination light from the light source to the sample.

The meanings of various terms used in the present disclosure are explained below. "Current flow" of a light source means the current through the light source or a current proportional thereto. The present brightness of the light source depends on the flowing current and is set by the flowing current. A measuring resistance device is understood to mean a circuit which is designed to measure a current (in particular a current of the light source flowing through or depending on it). The means for measuring resistance may comprise one or more resistances, referred to herein as measuring resistances. The current flowing through it causes a voltage drop through one or more resistors, which can be further measured or used. The measuring amplifier circuit with adjustable gain is configured to allow a targeted selection of different (discretely or continuously adjustable) gain values. When the settings of the measurement amplifier circuit are changed, the resulting gain change is known in advance. The measurement amplifier circuit taps the voltage across the measurement amplifier circuit, referred to herein as the voltage drop across the measurement amplifier circuit. The measurement amplifier circuit can be configured such that it either directly taps off the voltage drop or applies a voltage dependent on the voltage drop to the measurement amplifier circuit, for example, wherein the dependent voltage is derived from the voltage drop. However, it may be preferred that the input of the measuring amplifier circuit, or the input of the operational amplifier of the measuring amplifier circuit, is directly tapped off the voltage dropped across the measuring amplifier circuit. This avoids disturbing influences prior to amplification. An operational amplifier may also be understood to mean an operational amplifier circuit that may comprise a plurality of cooperating operational amplifiers. The measurement amplifier circuit outputs a signal or voltage that depends on the voltage drop, referred to herein as an amplified output signal. The amplified output signal or a signal derived therefrom is provided to the current regulating device. This signal supplied to the current regulating device is referred to as the "voltage drop signal" and is therefore, accordingly, exactly the amplified output signal or a signal derived therefrom. A current regulating device may be understood as an electronic circuit having an input for receiving a set value and an input for receiving a voltage drop signal. The current regulating device is designed to output a signal (in the present case referred to as a control command) which depends on the set point and the voltage drop signal, in particular on the difference between them. The control command is output to an electronic component configured to vary the current in accordance with the control command. As an example, the electronic component may include or may be formed of a transistor. The electronic component may be considered to be part of the current regulating device or an additional component of the current regulating device. In particular the electronic control device which sets the gain of the measuring amplifier circuit, can in principle be an electronic circuit of any design which is used to drive the function of the measuring amplifier circuit, realized by hardware and/or software. The control device may be designed as a local unit or as a spatially distributed system.

In particular, all or several of the following components can be considered as components of the control loop, through which the current flow is set: a measuring resistor arrangement, a measuring amplifier circuit, an electronic component with means for changing the current, a light source and a control device or parts thereof.

The characteristics of the invention described by the additional features of the lighting device, when used as intended, also result in a variant of the method according to the invention. Conversely, the lighting device may also be configured to carry out the described method variants.

Drawings

Further advantages and features of the invention will be described below with reference to the accompanying schematic drawings:

fig. 1 shows a schematic view of a first exemplary embodiment of a lighting device of the present invention;

fig. 2 shows a schematic view of a second exemplary embodiment of the lighting device of the present invention;

fig. 3 shows a schematic view of a third exemplary embodiment of the lighting device of the present invention;

fig. 4 shows a schematic view of a fourth exemplary embodiment of the lighting device of the present invention; and

fig. 5 shows a schematic view of an exemplary embodiment of an optical microscope of the present invention.

In the drawings, like and functionally similar elements are generally indicated by the same reference numerals.

Detailed Description

Fig. 1 shows an exemplary embodiment of an illumination device 100 for an optical microscope. The lighting device 100 comprises a light source 10, which in the example shown has an LED D1, and may generally also comprise further or other light emitters (illuminants). The through-current i1 through the light source 10 determines its illumination intensity and is set by a switching device (in this example a transistor Q1) to which, for this purpose, a variable voltage S is applied to its gate.

In order to be able to set the current i1 as precisely as possible and constantly over time, a current regulation device 20 and a measuring resistor arrangement 30 are used. The current regulating device 20 outputs a control command S for setting a flowing current i 1; in the illustrated example, the voltage at the gate of transistor Q1 is set for this purpose. The current regulating device 20 generates a control command S which is induced to the flow current i1 by means of the measuring resistance means 30.

In the example shown, the measuring resistance device 30 comprises a measuring resistance R1 having a constant resistance value. The measuring resistor means 30 are connected to the switching device. Thus, in the example shown, the measurement resistor R1 is connected to the source terminal of the transistor Q1, while the LED D1 is connected to the drain terminal of the transistor Q1. Thus, the current flowing through or associated with current i1 flows through measurement resistor R1; this is accompanied by a voltage drop U1 across the measurement resistor R1.

The voltage drop U1 is measured and the quantity dependent thereon is supplied to the current regulating device 20 to form a control loop. The desired brightness of the light source 10 and thus the current i1 flowing therethrough may vary over a wide range depending on the measurement situation or application. In contrast to some conventional lighting devices, the same measuring resistor R1 is always used in the illustrated exemplary embodiment of the invention, regardless of the magnitude of the current flowing through the current i 1. Here, the voltage drop U1 can be accurately captured in a wide range. This can be achieved by means of the voltage drop U1 amplified by the measurement amplifier circuit 50 with a variably adjusted gain factor. The electronic control device 40 sets the gain factor of the measuring amplifier circuit 50, in particular in dependence on the magnitude of the current flowing through the current i 1. The smaller the current i1, the higher the gain factor can be selected. The measurement amplifier circuit 50 now outputs an amplified output signal Ua which depends in a monotonic manner on the voltage drop U1 and which may in particular be proportional to the voltage drop U1. The amplified output signal Ua is supplied to the current regulating device 20, and the current regulating device 20 sets the magnitude of the control command S based on the amplified output signal Ua.

As shown in fig. 1, the amplified output signal Ua may be provided directly at the input of the current regulating device 20. More generally, a voltage drop signal Ue, which depends on the voltage drop U1, is provided at the input of the current regulating device 20, wherein Ue may be equal to the amplified output signal Ua or may be derived from the amplified output signal Ua.

In the exemplary embodiment shown, the current regulating device 20 comprises an operational amplifier OP1 providing a set value U + and an amplified output signal Ua at the input of an operational amplifier OP 1. The amplitude of the control command S is therefore dependent on the difference between U + and Ua. The set value U + is determined by the control device 40 depending on the desired brightness of the light source 10.

In the example of fig. 1, the measurement amplifier circuit 50 is formed by an operational amplifier circuit OP2 with an integrated interface for setting the gain. The control device 40 provides at OP2 a drive signal Us by which the gain factor is set to one of a plurality of different possible values. The operational amplifier circuit OP2 may be formed as an Integrated Circuit (IC).

In accordance with the present invention, a number of different implementations of the measurement amplifier circuit 50 are contemplated.

Fig. 2 shows an exemplary embodiment of an illumination device 100 according to the present invention, which differs from the design of the measuring amplifier circuit 50 of the above example. Thus, in fig. 2, the measuring amplifier circuit 50 comprises two measuring amplifiers (operational amplifiers) OP3 and OP4, which are connected in parallel with one another, in each case with a voltage drop U1 applied at their input. That is, one inputs of OP3 and OP4 are connected to a point before the measurement resistance R1, respectively, and the other inputs of OP3 and OP4 are connected to a point after the measurement resistance R1, respectively. The gains of the operational amplifiers OP3 and OP4 are different. Here, OP3 and OP4 may have constant, unchanging gain factors, respectively. For example, the IC INA193 and INA197 of Texas Instruments (TI) can be used as the measurement amplifiers OP3 and OP 4. The outputs of OP3 and OP4 lead to a multiplexer MUX, for example the ADG1433 of an analog device. Other switching devices may also be used as multiplexers. The multiplexer MUX allows to select whether to transmit the signal of OP3 or the signal of OP 4. Thus, the signal from OP3 or the signal from OP4 is forwarded to the current regulating device 20 as amplified output signal Ua. The control device 40 controls the multiplexer MUX and thus sets which operational amplifier OP3 and OP4 is currently used. For example, OP3 may have a greater gain factor than OP4, and the former may be used if the desired brightness of the light source 10 is below a specified threshold. Conversely, if a brightness above this threshold is desired, OP4 is used. In a modification of the illustrated embodiment, more than two operational amplifiers connected in parallel, each having a different gain factor, may also be used.

Another exemplary embodiment of a lighting device 100 according to the present invention is shown in fig. 3. Again, this differs from the described embodiment in the design of the measurement amplifier circuit 50. In fig. 3, the measurement amplifier circuit 50 includes operational amplifiers OP5 and OP6 connected in series. In this case, U1 is applied only to the input of the operational amplifier OP 5. In contrast, the operational amplifier OP6 is not directly connected to the measuring resistance device 30. As a result, potential interference effects on the measurement resistance device 30 by the operational amplifier OP6 are substantially eliminated. The operational amplifier OP5 outputs the amplified output signal to the input of the subsequent operational amplifier OP6 and to the multiplexer MUX. The operational amplifier OP6 amplifies the signal obtained from OP5 and outputs a corresponding amplified output signal to the multiplexer MUX. The control device 40 again controls the multiplexer MUX to select whether the multiplexer MUX transmits the signal amplified only by the amplifier OP5 or the signals amplified by the OP5 and OP6 to the current regulating device 20. It is considered that the OP5 and the OP6 may have the same gain factor or may have gain factors different from each other, respectively. In a variation of the illustrated example, even more than two operational amplifiers may be connected in series, each operational amplifier may be connected to a respective input of the multiplexer MUX.

Fig. 4 shows another exemplary embodiment. It is again different from the remaining examples in the design of the measurement amplifier circuit 50. In this case, the measurement amplifier circuit 50 comprises an instrumentation amplifier OP7, at the input of which the voltage U1 drops across a measurement resistor R1. By means of the adjustable resistor R2, the gain factor of the instrumentation amplifier OP7 can be changed. The adjustable resistor R2 may be, for example, an NT potentiometer or a digital potentiometer, which is controlled by the control device 40 via the bus.

In the figure, VCC denotes the operating voltage, by which the light source 10 is provided in particular. The remaining components, in particular the measuring amplifier circuit 50 and/or the current regulating device 20, can likewise be fed by VCC or a voltage associated therewith, wherein in principle they can also be fed by a voltage independent of VCC. In adjusting the gain factor and adjusting the brightness, the operating voltages of the light source 10, the measurement amplifier circuit 50 and the current adjusting device 20 are kept constant or are not actively adjusted in any case.

In the exemplary embodiment shown, the control device 40 selects the setting U + of the current regulating device 20 and the gain factor of the measurement amplifier circuit 50. Both values affect the level of the subsequently output control command S and thus the brightness of the resulting light source 10. The control device 40 may be configured to select a certain gain factor depending on the desired brightness. The relation between the desired brightness and the gain factor to be selected may be specified and may be stored in a data memory of the control device 40. Now, the control device 40 selects the setting value U + not only on the basis of the desired brightness, but also on the basis of the gain factor belonging to this brightness. In particular, in the example of fig. 1, in order to change the brightness of the light source 10, the control device 40 may also not adapt the setting value U +, but adjust the gain factor of the measurement amplifier circuit 50.

In all exemplary embodiments, the voltage U1 across the measuring resistor R1 is first amplified before other electronic components act on the measuring resistor R1. As a result, the structure is more robust to the potentially disturbing effects of these components. For example, in fig. 2 and 3, the multiplexer MUX is not directly connected to the measurement resistor R1. In contrast to the switches used in the prior art for selecting different measuring resistors and therefore arranged directly on the measuring resistor, the multiplexer MUX has no or only a little influence on the signal on the measuring resistor to be measured. Instead, U1 is first amplified by a selectable factor, in particular for an optimal resolution of the current i1 to be measured.

In the case where the desired luminance is changed, the control device 40 changes the gain of the measurement amplifier circuit 50 to a gain value provided for the desired luminance. At the same time, the control device 40 can also adapt the set value U +. This makes it possible to set new brightness values particularly quickly and largely unchanged.

Fig. 5 schematically shows an exemplary embodiment of an optical microscope 110 of the invention, comprising an illumination device 100 according to one of the embodiments of fig. 1 to 4. The illumination device 100 emits illumination light 101, which is directed to the sample 106 by the optical element. Detection light 105 from a sample 106 is directed via an objective lens 104 and optical elements to a light detector 108, such as a camera chip. The detection light 105 may be, for example, fluorescence, wherein the detection light may also be, for example, illumination light scattered on the sample or illumination light transmitted through the sample, depending on the structure and measurement operation of the microscope. The illustrated example shows a confocal descan setup, in which the illumination light is also directed via the objective 104. The scanner 102 is used both to scan a sample 106 with illumination light 101 and to direct detection light 105 from a currently illuminated sample region. The beam splitter 107 separates the illumination beam path and the detection beam path from each other. To this end, the beam splitter 107 is transmissive to the illumination light 101 and reflective to the detection light 105, or vice versa. For example, the beam splitter 107 may transmit or reflect light in a wavelength-dependent or polarization-dependent manner. The illumination device 100 may also be used in optical microscopes of different designs, for example, which are not scanning microscopes or confocal microscopes.

List of reference identifiers

10 light source

20 current regulating device

30 resistance measuring device

40 electronic control device

50 measurement amplifier circuit

100 lighting device

101 lamp/lighting lamp

102 scanner

104 objective lens

105 detection lamp

106 samples

107 beam splitter

108 photo detector

110 optical microscope

LED of D1 light source 10

i1 light source flowing current 10

MUX multiplexer

OP1 operational amplifier of current regulating device 20

OP2 operational amplifier circuit/measurement amplifier circuit 50 integrated circuit

Measurement amplifier for OP3-OP6 measurement amplifier circuit 50

Instrumentation amplifier for OP7 measurement amplifier circuit 50

Q1 transistor of current regulating device 20 for setting the current i1 flowing

R1 measuring resistance of resistance device 30

Adjustable resistor of R2 instrumentation amplifier OP7

S is a control command for setting the current regulating device 20 through which the current i1 flows

U1 measures the voltage drop across the resistance device 30

Ua depends on the amplified output signal of the voltage drop U1,

ue voltage drop signal related to voltage drop U1

Us drive signal for integrated circuit OP2 for setting a certain gain

Set value of the U + current adjusting device 20

Operating voltage of the VCC light source 10

Claims

1. An illumination device for an optical microscope, comprising

-a light source (10),

-a current regulating device (20) for regulating the through-flowing current (i1) of the light source (10), and

-a measuring resistor arrangement (30), wherein a voltage drop (U1) across the measuring resistor arrangement (30) is dependent on a current (i1) through the light source (10),

wherein the current regulating device (20) is configured to regulate the current (i1) through the light source (10) based on a voltage drop signal (Ue) related to the voltage drop (U1) over the measuring resistor arrangement (30),

a measurement amplifier circuit (50) with an adjustable gain, wherein the measurement amplifier circuit (50) is configured to output an amplified output signal (Ua) dependent on the voltage drop (U1) as a voltage drop signal (Ue) to the current regulating device (20).

2. The illumination device of claim 1,

the resistance value of the measuring resistor arrangement (30) is selected to be constant independently of the current (i1) flowing through the light source (10).

3. The lighting device according to claim 1 or 2,

an electronic control device (40) is provided which is configured to set the gain of the measurement amplifier circuit (50) based on the selected brightness of the light source (10).

4. A lighting device as recited in any one of claims 1-3,

the electronic control device (40) is configured to select a larger gain of the measurement amplifier circuit (50) as the current (i1) through the light source (10) decreases.

5. The lighting device according to any one of claims 1 to 4,

the electronic control device (40) is configured to:

-according to a desired brightness of the light source (10), an

-a gain based on a current setting of the measurement amplifier circuit (50)

The set value (U +) of the current regulating device (20) is set.

6. A lighting device as recited in any one of claims 1-5,

the electronic control device (40) is configured to:

-according to a desired brightness of the light source (10), an

-gain based on a measurement amplifier circuit (50) provided for a desired brightness

A setpoint value (U +) is set for the current regulation device (20).

7. A lighting device as recited in any one of claims 1-6,

the measurement amplifier circuit (50) comprises at least two measurement amplifiers (OP3-OP6) and is configured to be selectively set, in particular by a Multiplexer (MUX), which measurement amplifier (OP3-OP6) is involved in amplifying the output of the output signal (Ua) for output as a voltage drop signal (Ue) to the current regulating device (20).

8. Lighting device as claimed in the preceding claim,

the measuring amplifiers (OP3, OP4) are connected in parallel with each other and have different gains,

the Multiplexer (MUX) makes selectable which of the parallel measuring amplifiers (OP3, OP4) provides the output signal (Ua) to the current regulating device (20).

9. The illumination device of claim 7,

the measuring amplifiers (OP5, OP6) are connected in series,

the Multiplexer (MUX) makes selectable which of the series-connected measurement amplifiers (OP5, OP6) supplies the output signal (Ua) to the current regulating device (20).

10. The lighting device as defined in any one of claims 1-9,

the measurement amplifier circuit (50) is formed as an integrated circuit (OP2) and is configured to set a gain in dependence on the drive signal (Us).

11. The lighting device as defined in any one of claims 1-9,

the measurement amplifier circuit (50) includes an instrumentation amplifier (OP7) having an adjustable resistance (R2) for setting the gain.

12. An optical microscope having an illumination device according to any one of the preceding claims for illuminating a sample, comprising a light detector (108) for measuring detection light (105), and an objective (104) for guiding detection light (105) from the sample to the light detector (108).

13. A method of illuminating an optical microscope, comprising:

the current (i1) flowing through the light source (10) is set by means of a current regulating device (20),

wherein a measuring resistor device (30) is provided, wherein a voltage drop (U1) across the measuring resistor device (30) is dependent on a current (i1) flowing through the light source (10), and

wherein the current regulating device (20) regulates the through-current (i1) of the light source (10) on the basis of a voltage drop signal (Ue) which is dependent on a voltage drop (U1) across the measuring resistor arrangement (30),

generating an amplified output signal (Ua) dependent on the voltage drop (U1) by means of a measuring amplifier circuit (50) with an adjustable gain, wherein different gains are set for different levels of the flowing current (i1), and

the amplified output signal (Ua) is output as a voltage drop signal (Ue) to the current regulation device (20).