Imaging system with a changing device and microscope

Abstract

An imaging system (100) comprises a changing device (102) with a changing holder (108) which is designed to receive at least one optical element (106) and thereby to arrange it in an optical beam path (104) of the imaging system (100), and an access element (112) which has an open and a closed state and is designed to enable access to the optical element (106) received in the changing holder (108) in the open state. The changing device (102) further comprises a bistable element (114) which has a first stable state and a second stable state and is designed to transition from the first stable state to the second stable state when the access element (112) is opened and to remain in the second stable state when the access element (112) is closed.The imaging system (100) further comprises a control unit (120) which is designed to determine whether the bistable element (114) is in the first stable state or the second stable state, and to determine that the access element (112) has been opened and thus access to the optical element (106) accommodated in the interchangeable holder (108) has been made possible when the bistable element (114) is in the second stable state.

Description

Technical field

[0001] The invention relates to an imaging system with a changing device. The invention also relates to a microscope. Background of the invention

[0002] Many microscopes contain interchangeable optical elements, such as objectives and eyepieces, but filters or beam splitters can also be interchangeable. Calibration of the microscope is often required after changing an optical element, especially if the interchangeable optical elements are part of the microscope's optical beam path. However, calibrating a microscope can be a very time-consuming process, significantly reducing the time the microscope can be used for experiments. It is therefore desirable to avoid unnecessary calibration processes whenever possible.

[0003] Regarding the prior art, reference is made to US 11 404 243 B1, which discloses a stage for an electron microscope, to DE 10 2004 034 887 A1, which discloses a microscope with an insertable holding device for optical components, to US 7 649 686 B2, which discloses a box-type microscope, and to DE 10 2012 005 541 A1, which discloses a safety device for an elevator shaft. Summary

[0004] It is therefore an object of the invention to provide an imaging system with a changing device and a microscope which make it possible to reduce the number of calibration processes.

[0005] This object is achieved by an imaging system having the features of claim 1 and by a microscope having the features of the further independent claim. Advantageous further developments are specified in the dependent claims.

[0006] The proposed imaging system comprises a changing device. The changing device comprises a changing holder configured to receive at least one optical element and thereby arrange it in an optical beam path of the imaging system, and an access element having an open and a closed state and configured, in the open state, to enable access to the optical element received in the changing holder. The changing device further comprises a bistable element having a first stable state and a second stable state and configured to transition from the first stable state to the second stable state upon opening of the access element and to remain in the second stable state upon closing of the access element.The imaging system further comprises a control unit configured to determine whether the bistable element is in the first stable state or the second stable state, and to determine that the access element has been opened and thus access to the optical element accommodated in the interchangeable holder has been enabled when the bistable element is in the second stable state.

[0007] Using the interchangeable mount, the optical element can be positioned in the optical beam path of the imaging system. For example, a filter or filter cube can be positioned in a beam path in front of a detector of the imaging system to allow the detector to detect only a specific wavelength range.

[0008] The access element is, for example, a part of a housing of the imaging system, which comprises at least the interchangeable holder. In the closed state, the access element prevents access to the interchangeable holder and the optical element arranged therein, such that the optical element cannot be removed from the interchangeable holder, for example during operation of the imaging system. In particular, in the closed state, the access element prevents the optical element from being adjusted and thus a calibration of the imaging system becoming necessary. In the open state, however, the access element allows access to the optical element, for example in order to exchange the optical element for another one. If the access element has been opened, i.e. has been in the open state at least once, there is a possibility that the optical element has been removed, replaced, or adjusted.However, this means that if the access element was opened after the imaging system had been calibrated, recalibration may be necessary.

[0009] When the imaging system is in operation, it could be determined, for example, by reading a sensor in the area of ​​the access element when the access element is opened. However, this may not be possible when the imaging system is switched off.

[0010] The switching device of the proposed imaging system therefore includes the bistable element. When the access element is opened, the bistable element transitions from the first stable state to the second stable state and remains there. This detection of a successful opening of the access element functions when the imaging system is switched off and thus represents a power-free "state memory."

[0011] The bistable element, which is in the second stable state after opening, must then be returned to the first stable state. This can be done manually, for example, by a user.

[0012] If the access element was opened while the imaging system was switched off, the control unit can determine this based on the state of the bistable element. The exchange device can thus ensure that it is reliably determined whether the access element was opened and thus whether access to the optical element arranged in the exchange holder was possible. Since recalibration is often only necessary if there is a possibility that the optical element has been removed, replaced, or adjusted, the number of calibration processes can be reduced and the operating time of the imaging system can be increased.

[0013] In one embodiment, the control unit is designed to determine, when the imaging system is switched on, whether the bistable element is in the first stable state or the second stable state. The control unit can further be designed to determine that, when the imaging system is switched off, the access element was opened and thus access to the optical element received in the interchangeable holder was enabled. If the access element was opened when the imaging system was switched off, the bistable element was brought from the first stable state to the second stable state. If the bistable element is in the second stable state when switched on, the access element was opened when the imaging system was switched off and access to the optical element was enabled.Based on this information, the control unit can, for example, initiate a recalibration or inform the user that recalibration of the imaging system is required before, for example, starting an experiment. This ensures that the measurement results obtained in the experiment are accurate by minimizing the risk of errors that could be caused by incorrect calibration.

[0014] In a further embodiment, the changing device comprises a first sensor configured to determine whether the bistable element is in the first stable state or in the second stable state. The control unit can be configured to determine, using first sensor data provided by the first sensor, whether the bistable element is in the first stable state or in the second stable state. Thus, the control unit can reliably determine, using the first sensor, whether the access element has been opened.

[0015] In a further embodiment, the changing device comprises a second sensor which is designed to determine whether the access element is in the open state or in the closed state. The control unit can be designed to determine, using second sensor data provided by the second sensor, whether the access element is in the open state or in the closed state. The control unit can thus reliably determine, using the second sensor, whether access to the optical element is currently possible. If, for example, the user opens the access element while the imaging system is in operation, i.e. when the imaging system is switched on, the control unit can determine this using the second sensor and, for example, cause a warning to be issued.This prevents, for example, the user from accidentally adjusting the optical element located in the interchangeable holder, which would require recalibration.

[0016] The first sensor and / or the second sensor can, for example, each be one of the following sensor types: a push button, a light barrier, a Hall sensor, an inductive proximity switch and a capacitive proximity switch.

[0017] In a further embodiment, the imaging system comprises an output unit. The control unit can be configured to control the output unit to output a corresponding warning when the control unit has determined that the access element has been opened. The output unit can, for example, comprise a screen, a display, a warning lamp, or other optical output elements. However, the output unit can also comprise acoustic output elements, for example a loudspeaker or a buzzer. The control unit can use the output unit to inform the user that the access element has been opened and that access to the optical element accommodated in the interchangeable holder was thus possible. The control unit can also inform the user that recalibration is required, which can, for example, be initiated manually by the user.Furthermore, the control unit can be designed to control the output unit to output a corresponding warning when the control unit has determined that the access element is currently in the open state.

[0018] In a further embodiment, the control unit is configured to start a calibration process of the imaging system when the control unit has determined that the access element has been opened. If the access element has been opened, recalibration is required. In this embodiment, the imaging system acts proactively and starts the calibration process required for recalibration. The calibration process can be started automatically by the control unit. The control unit can also be configured to start the calibration process of the imaging system only after user confirmation. The user confirmation can, for example, be a user input into an input unit of the imaging system.This informs the user that recalibration is required, but gives the user the choice of whether to perform the calibration process now or at a later time.

[0019] In a further embodiment, the access element comprises a drawer or a pivoting drawer. The drawer or pivoting drawer can, for example, be formed as part of the housing of the imaging system and enable easy and quick access to the changing device and the optical element arranged therein.

[0020] In a further embodiment, the drawer or the swivel tray encloses the interchangeable holder. If the drawer or the swivel tray is formed, for example, as part of the housing of the imaging system, the interchangeable holder can be at least partially extended out of the housing in this embodiment to enable easy and quick access to the optical element arranged therein.

[0021] In a further embodiment, the access element comprises a flap of the housing of the imaging system. In this embodiment, the interchangeable holder is, for example, fixedly arranged within the housing. Opening the flap prevents the interchangeable holder from moving, which minimizes the risk of the optical element arranged in the interchangeable holder being displaced and requiring readjustment. The flap can also be used to close the housing, preventing stray light from entering the optical beam path in which the optical element is arranged.

[0022] In a further embodiment, the bistable element comprises a mechanical follower which is designed to be moved from a first position to a second position by mechanical contact with the access element when the access element is opened and to remain in the second position when the access element is closed, such that the first stable state corresponds to the first position of the follower and the second stable state corresponds to the second position of the follower. In such an embodiment, the access element comprises or forms a follower, such that when the access element moves, the follower of the bistable element is moved. The position of the follower can be detected, for example, by the first sensor. The follower can, for example, be linearly mounted or comprise a rotatable disk.After the control unit has determined that the follower is in the second position, the follower can be returned to the first position, for example, by motor or manually by a user. The follower is moved into the second position purely by mechanical contact with the access element. This eliminates the need to supply the bistable element with electrical energy, for example, to determine whether the access element has been opened. Unlike a button or other sensor, the bistable element can also be used, in particular, to determine whether the access element has been opened while the imaging system is switched off.

[0023] In a further embodiment, the bistable element comprises a bistable lifting magnet. The first stable state can correspond to a first position of an armature of the lifting magnet. The second stable state can correspond to a second position of the armature of the lifting magnet. In this embodiment, the armature of the lifting magnet forms the mechanical follower. The position of the armature can also be detected, for example, by the first sensor. The control unit can be configured to control the lifting magnet such that the armature is returned to the first position. The armature can also be returned to the first position using a motor or manually by a user. In this embodiment, too, it is not necessary for the imaging system to be switched on in order to be able to detect whether the access element has been opened.

[0024] In a further embodiment, the control unit is designed to control the bistable element in order to return the bistable element to the first stable state.

[0025] For example, the control unit can be configured to control the bistable element after the calibration process has been completed in order to return the bistable element to the first stable state. To return the bistable element to the first stable state, the control unit can, for example, control a motor that returns the mechanical follower of the bistable element to the first position. The control unit can also be configured to control the solenoid in such a way that the armature is returned to the first position. By automatically returning the bistable element to the first state, there is no need to manually reset the bistable element in order to detect a renewed opening of the access element. The imaging system is therefore very user-friendly.

[0026] In a further embodiment, the interchangeable holder is configured to accommodate at least one of the following optical elements: a filter, a filter cube, a fluorescence filter, a beam splitter, a lens, a lens element, and an aperture stop. The aforementioned optical elements are frequently used in various types of imaging systems. The imaging system is thus versatile.

[0027] The invention further relates to a microscope comprising the imaging system described above with the exchange device. The microscope has the same advantages as the imaging system. In particular, the microscope can be further developed with features described in this document in connection with the imaging system. Furthermore, the imaging system described above can be further developed with features described in this document in connection with the microscope. Short description of the characters

[0028] Embodiments of the invention are explained in more detail below with reference to the figures, in which: Fig. 1 an imaging system with a changing device according to an embodiment; Fig. 2a to 2d each show a schematic representation of a changing device of the imaging system according to a further embodiment; Fig. 3a to 3d each show a schematic representation of a changing device of the imaging system according to a further embodiment; Fig. 4a to 4d each show a schematic representation of a changing device of the imaging system according to a further embodiment; Fig. 5 shows a microscope according to an embodiment; and Fig. 6 shows the flowchart of an exemplary method for operating the imaging system. Detailed description

[0029] Fig. 1 shows a schematic representation of an imaging system 100 with a changing device 102 according to one embodiment. The imaging system 100 is, for example, part of a microscope, a slide scanner, a spectrometer, or another optical device and includes at least one optical beam path 104.

[0030] The imaging system 100 has a changing device 102, which is designed such that at least one replaceable optical element 106 can be introduced into the optical beam path 104. The replaceable optical element 106 can be, for example, a filter, a filter cube, a beam splitter, a lens, a lens element, an aperture stop, or a similar optical element. Fig. 1, the optical element 106 is shown purely by way of example as a lens. The changing device 102 comprises a changing holder 108 in which the optical element 106 can be arranged. Once the optical element 106 is received in the changing holder 108, the optical element 106 can be introduced into the optical beam path 104 of the imaging system 100, as shown in Fig. 1 is shown.

[0031] In the embodiment shown, the optical beam path 104 is arranged within a housing 110 of the imaging system 100. To enable access to the interchangeable holder 108 and thus to the optical element 106, the interchangeable device 102 comprises an access element. The access element has an open state in which access to the interchangeable holder 108 and the optical element 106 arranged therein is possible. When the access element is open, for example, the optical element 106 can be removed from the interchangeable holder 108 or exchanged for another optical element 106. The access element 112 also has a closed state in which access to the interchangeable holder 108 and the optical element 106 arranged therein is not possible. For example, the access element 112 can be closed to ensure safe operation of the imaging system 100.

[0032] The changing device 102 also includes a bistable element 114, which has a first stable state and a second stable state. If the bistable element 114 is in the first stable state, it can only transition to the second stable state through the application of an external force. Conversely, the bistable element 114 can only be returned to the first stable state through the application of an external force. In the changing device 102, the bistable element 114 is arranged and configured to be brought from the first stable state to the second stable state by opening the access element 112, for example, through mechanical contact with the access element 112. The bistable element 114 is further configured to remain in the second stable state when the access element 112 is closed.

[0033] The changing device 102 further comprises a first sensor 116, which is Fig. 1 is arranged on the bistable element, and a second sensor 118, which is in Fig. 1 is arranged to the left of the access element 112. The first sensor 116 is designed to determine the state of the bistable element 114, i.e. whether the bistable element 114 is in the first stable state or in the second stable state. The result of this determination can be provided by the first sensor 116, for example, in the form of first sensor data. The second sensor 118 is designed to determine the state of the access element 112, i.e. whether the access element 112 is currently open or closed. The result of this determination can be provided by the second sensor 118, for example, in the form of second sensor data.

[0034] A control unit 120 of the imaging system 100 is configured to determine whether the access element 112 has been opened and thus access to the optical element 106 arranged in the interchangeable holder 108 was possible. To this end, the control unit 120 first determines whether the bistable element 114 is in the first stable state or in the second stable state. To this end, the control unit 120 processes, for example, the first sensor data. If the control unit 120 has determined that the bistable element 114 is in the second stable state, the control unit 120 determines that the access element 112 has been opened. This determination can be made at various times during operation of the imaging system 100. In one embodiment, the control unit 120 determines the state of the bistable element 114 when the imaging system 100 is switched on.If the control unit 120 determines that the bistable element 114 is in the second stable state when switched on, the control unit 120 determines that the access element 112 was opened in the off state. This means that access to the optical element 106 was possible while the imaging system 100 was switched off.

[0035] If the control unit 120 has determined that the access element 112 has been opened, the control unit 120 can take a number of measures. Since access to the optical element 106 arranged in the interchangeable holder 108 was possible in this case, there is a possibility that the optical element 106 was adjusted or removed and thus a previously performed calibration of the imaging system 100 must be performed again. In one embodiment, the control unit 120 automatically starts the recalibration when the control unit 120 has determined that access to the optical element 106 arranged in the interchangeable holder 108 was possible. In another embodiment, the control unit 120 only starts the recalibration after confirmation by a user. After calibration has been completed, the control unit 120 can control the bistable element 114 to return the bistable element 114 to the first state.

[0036] The Fig. The embodiment of the imaging system 100 shown in Figure 1 further comprises an output unit 122, for example, a display. The output unit 122 can be controlled, for example, to output information or warnings to the user. In one embodiment, the control unit 120 is configured to control the output unit 122 to output a warning. For example, the control unit 120 can warn the user that the access element 112 has been opened in the off state or that the access element 112 is currently open. The control unit 120 can further inform the user that the bistable element 114 must be reset to the first state.

[0037] Fig. 2a to 2d each show a schematic representation of the changing device 200 of the imaging system 100 according to a further embodiment. Fig. In the embodiment shown in Figures 2a to 2d, the bistable element 202 comprises a lifting magnet 204.

[0038] The lifting magnet 204 comprises an armature 206, which is linearly mounted and surrounded by two coils 208, 210. By applying a voltage to a first coil 208, the armature 206 can be moved to a first position. If the voltage is no longer applied, the armature 206 then remains in the first position. By applying a voltage to a second coil 210, the armature 206 can be moved to a second position. If no voltage is applied to the second coil 210, the armature 206 remains in the second position. The first position of the armature 206 thus corresponds to the first stable state, and the second position of the armature 206 corresponds to the second stable state. The position of the armature 206 is detected by the first sensor 116. In Fig. In Figure 2a, the armature 206 is in the first position, meaning that the bistable element 202 is in the first state. This represents the initial position.

[0039] In the Fig. In the embodiment shown in Figures 2a to 2d, the access element 212 comprises a drawer 214, which comprises the interchangeable holder 108. The drawer 214 further comprises a driver 216, which is designed as a ramp. When the drawer 214 is opened, the driver 216 abuts the armature 206 and moves the armature 206 into the second position by mechanical contact. The armature 206 thus forms a mechanical follower. The situation when opening the drawer 214 is shown in Fig. 2b, in which a first arrow P1 indicates the direction of movement of the drawer 214 when opening. A second arrow P2 in Fig. 2b shows the direction of movement of the armature 206 when opening the drawer 214. The fact that the drawer 214 is open is registered by the second sensor 118.

[0040] The driver 216 of the drawer 214 is further configured such that the armature 206 remains in the second position when the drawer 214 is closed. The situation when closing the drawer 214 is shown in Fig. 2c, in which an arrow P3 indicates the direction of movement of the drawer 214 during closing. If the armature 206 is in the second position, it can be assumed that the drawer 214 has been opened and access to the optical element 106 arranged in the interchangeable holder 108 was possible. To return the armature 206 to the first position, the lifting magnet 204 can be controlled to supply current to the first coil 208. The return of the armature 206 is shown in Fig. 2d, in which an arrow P4 indicates the direction of movement of the armature 206 when returning to the first position.

[0041] Fig. 3a to 3d each show a schematic representation of the changing device 300 of the imaging system 100 according to a further embodiment. Fig. In the embodiment shown in Figures 3a to 3d, the bistable element 302 comprises a linearly mounted follower 304.

[0042] The linearly mounted follower 304 corresponds in its function to the armature 206 of the lifting magnet 204. In Fig. 3a, the linearly mounted follower 304 is in a first position corresponding to the first stable state of the bistable element 302. Fig. 3a thus shows the starting position. When the drawer 214 is opened, the driver 216 of the drawer 214 comes into contact with the linearly mounted follower 304 and moves it to a second position. The situation when the drawer 214 is opened is shown in Fig. 3b, in which a first arrow P5 indicates the direction of movement of the drawer 214 during opening. A second arrow P6 in Fig. Figure 3b shows the direction of movement of the linearly mounted follower 304 when opening the drawer 214. When closing the drawer 214, the linearly mounted follower 304 remains in the second position, which thus corresponds to the second stable state. The situation when closing the drawer 214 is shown in Fig. 3c, in which an arrow P7 indicates the direction of movement of the drawer 214 when closing.

[0043] The changing device 300 further comprises a linear motor 306, which is designed to return the linearly mounted follower 304 to the first position. The return of the linearly mounted follower 304 is Fig. 3d, in which an arrow P8 indicates the direction of movement of the linearly mounted follower 304 when returning to the first position.

[0044] Fig. 4a to 4d each show a schematic representation of the changing device 400 of the imaging system 100 according to a further embodiment. Fig. In the embodiment shown in Figures 4a to 4d, the access element 402 comprises a pivoting drawer 404 which comprises the interchangeable holder 108.

[0045] The bistable element 406 comprises in the Fig. 4a to 4d, a disk 408 on which two cams 410, 412 are formed. The changing device 400 further comprises a rotary motor 414, which is connected, purely by way of example, via a belt 416 to an axle 418 of the disk 408. A first cam 410 of the disk 408 is located in Fig. 4a in a first position, which corresponds to the first stable state. A driver 420 of the swivel drawer 404 strikes the first cam 410 of the disk 408 when the swivel drawer 404 is opened. The first cam 410 thus corresponds in its function to the armature 206 of the lifting magnet 204 and the linearly mounted follower 304. The force exerted by the driver 420 on the disk 408 is greater than the friction between the belt 416 and the axis 418 of the disk 408. The first cam 410 is thus rotated out of the first position. The opening of the swivel drawer 404 is in Fig. 2b, in which an arrow P9 indicates the direction of rotation of the swivel drawer 404 and the disc 408 during opening. When the swivel drawer 404 is open, the first cam 410 is in a second position. If the first cam 410 is in the second position, the disc 408 is rotated such that a second cam 412 abuts the first sensor 116. As a result, the second sensor 118 detects that the first cam 410 is in the second position. When the swivel drawer 404 is closed, the disc 408 remains in its position, i.e., the first cam 410 remains in the second position, which thus corresponds to the second stable state. The situation when closing the drawer 214 is shown in Fig. 4c, in which an arrow P10 indicates the direction of movement of the pivoting drawer 404 during closing. With the help of the rotary motor 414, the disc 408 can then be rotated back to return the first cam 410 to the first position. The reversing of the disc 408 is shown in Fig. 4d, in which an arrow P11 indicates the direction of movement of the disc 408 when turning back.

[0046] Fig. 5 shows a microscope 500 according to an embodiment. The microscope 500 includes the imaging system 100, which is shown purely schematically as a box. The optical beam path 104 is a beam path of the microscope 500.

[0047] Fig. 6 shows the flowchart of an exemplary method for operating the imaging system 100.

[0048] The method is started in step S600. In step S602, the imaging system 100 is switched on, for example, by the user. In step S604, it is determined whether the access element 112, 212, 402 was opened while the imaging system 100 was switched off. In one embodiment, the control unit 120 determines the state of the bistable element 114, 202, 302, 406 based on the first sensor data. If the bistable element 114, 202, 302, 406 is in the second state, the control unit 120 determines that the access element 112, 212, 402 was opened, and the method continues in step S606. If the bistable element 114, 202, 302, 406 is in the first state, the control unit 120 determines that the access element 112, 212, 402 has not been opened, and the method is terminated in step S612. In step S606, it is determined whether the access element 112, 212, 402 is currently open.In one embodiment, the control unit 120 determines, based on the second sensor data, whether the access element 112, 212, 402 is currently open. If the access element 112, 212, 402 is currently open, a corresponding warning can be output to the user. In one embodiment, the control unit 120 controls the output unit 122 to output the warning. The warning can also be associated with a request to the user to close the access element 112, 212, 402. The method then continues in step S608 if the access element 112, 212, 402 has been closed.

[0049] In step S608, a calibration of the imaging system 100 is performed. This ensures that the imaging system 100 is correctly adjusted, even if the optical element 106 has been moved, adjusted, or replaced since the last calibration. In one embodiment, the control unit 120 initiates a calibration process to start the calibration of the imaging system 100. In step S610, after the calibration has been completed, the bistable element 114, 202, 302, 406 is returned to the first stable state. This can be done manually by the user, who has been prompted to do so by a corresponding output. However, this can also be done automatically, for example, by the control unit 120 controlling the bistable element 114, 202, 302, 406 accordingly. The method is then terminated in step S612 when the bistable element 114, 202, 302, 406 is again in the first stable state.

[0050] The term “and / or” includes all combinations of one or more of the related listed elements and may be abbreviated as “ / ”.

[0051] Although some aspects have been described in the context of a device, it is clear that these aspects also represent a description of the corresponding method, with a block or device corresponding to a method step or a function of a method step. Similarly, aspects described in the context of a method step also represent a description of a corresponding block, element, or property of a corresponding device. List of reference symbols 100 Imaging System 102 Changing device 104 Beam path 106 Optical element 108 interchangeable holder 110 housings 112 Access element 114 Bistable element 116, 118 Sensor 120 control unit 122 Output unit 200 changing device 202 Bistable element 204 lifting magnet 206 anchors 208, 210 coil 212 Access element 214 drawer 216 drivers 300 changing device 302 Bistable element 304 followers 306 linear motor 400 changing device 402 access element 404 Swivel drawer 406 Bistable element 408 disc 410, 412 cams 414 rotary motor 416 belts 418 Axis 420 carriers P1-P11 arrow

Claims

[1] An imaging system (100) having a changing device (102, 200, 300, 400), wherein the changing device (102, 200, 300, 400) comprises an interchangeable holder (108) which is designed to receive at least one optical element (106) and thereby to arrange it in an optical beam path (104) of the imaging system (100), an access element (112, 212, 402) which has an open and a closed state and is designed to allow access to the optical element (106) accommodated in the interchangeable holder (108) in the open state, and a bistable element (114, 202, 302, 406) having a first stable state and a second stable state and configured to transition from the first stable state to the second stable state upon opening of the access element (112, 212, 402) and to remain in the second stable state upon closing of the access element (112, 212, 402); and wherein the imaging system (100) further comprises a control unit (120) configured to determine whether the bistable element (114, 202, 302, 406) is in the first stable state or the second stable state, and to determine that the access element (112, 212, 402) has been opened and thus access to the optical element (106) accommodated in the interchangeable holder (108) has been enabled when the bistable element (114, 202, 302, 406) is in the second stable state. [2] The imaging system (100) according to claim 1, wherein the control unit (120) is configured to determine, when the imaging system (100) is switched on, whether the bistable element (114, 202, 302, 406) is in the first stable state or the second stable state, and to determine that, in a switched-off state of the imaging system (100), the access element (112, 212, 402) has been opened and thus access to the optical element (106) accommodated in the interchangeable holder (108) has been made possible when the bistable element (114, 202, 302, 406) is in the second stable state. [3] The imaging system (100) according to claim 1 or 2, wherein the changing device (102, 200, 300, 400) comprises a first sensor (116) configured to determine whether the bistable element (114, 202, 302, 406) is in the first stable state or in the second stable state. [4] The imaging system (100) according to any one of the preceding claims, wherein the changing device (102, 200, 300, 400) comprises a second sensor (118) configured to determine whether the access element (112, 212, 402) is in the open state or in the closed state. [5] The imaging system (100) according to any one of the preceding claims, comprising an output unit (122), wherein the control unit (120) is configured to control the output unit (122) to output a corresponding warning when the control unit (120) has determined that the access element (112, 212, 402) has been opened. [6] The imaging system (100) according to any one of the preceding claims, wherein the control unit (120) is configured to start a calibration process of the imaging system (100) when the control unit (120) has determined that the access element (112, 212, 402) has been opened. [7] The imaging system (100) of any preceding claim, wherein the access element (212, 402) comprises a drawer (214) or a pivoting drawer (404). [8] The imaging system (100) of claim 7, wherein the drawer (214) or the pivoting drawer (404) comprises the interchangeable holder (108). [9] The imaging system (100) according to any one of the preceding claims, wherein the access element (112, 212, 402) comprises a flap of a housing (110) of the imaging system (100). [10] The imaging system (100) according to any one of the preceding claims, wherein the bistable element (202, 302, 406) comprises a mechanical follower (206, 304, 410) which is designed to be moved from a first position to a second position by mechanical contact with the access element (212, 402) upon opening of the access element (212, 402) and to remain in the second position upon closing of the access element (212, 402), such that the first stable state corresponds to the first position of the mechanical follower (206, 304, 410) and the second stable state corresponds to the second position of the mechanical follower (206, 304, 410). [11] The imaging system (100) according to any one of the preceding claims, wherein the bistable element (202) comprises a lifting magnet (204), the first stable state corresponds to a first position of an armature (206) of the lifting magnet (204), and the second stable state corresponds to a second position of the armature (206) of the lifting magnet (204). [12] The imaging system (100) according to any one of the preceding claims, wherein the control unit (120) is configured to control the bistable element (114, 202, 302, 406) to return the bistable element (114, 202, 302, 406) to the first stable state. [13] The imaging system (100) according to any one of the preceding claims, wherein the interchangeable holder (108) is configured to receive at least one of the following optical elements: a filter, a filter cube, a fluorescence filter, a beam splitter, a lens, a lens element, and an aperture stop. [14] A microscope (500) comprising the imaging system (100) according to any one of the preceding claims.

Images