Lighting device and lighting method having limitation of the maximum irradiance

Abstract

The invention relates to a lighting device (100) and to a method for lighting a surface (Ob) with a maximum total irradiance. At least two lighting units (1, 2, 3) of the lighting device (100) illuminate the surface (Ob) at a maximum irradiance in each case. A control device (10) actuates each lighting unit (1, 2, 3) independently of the other lighting unit and thereby changes the maximum irradiance of the lighting unit (1, 2, 3). The lighting device (100) detects a user specification (9) relating to the maximum total irradiance. In response to this, the control device (10) predicts what maximum total irradiance would be achieved if the user specification (9) were implemented. If the predicted maximum total irradiance is greater than a predetermined upper bound, the control device actuates at least one lighting unit (1, 2, 3) according to the user specification. This actuation ensures that the upper bound is met.

Description

[0001] Lighting device and lighting method with limitation of the maximum irradiance

[0002] Description

[0003] The invention relates to a lighting device and a lighting method.

[0004] Such a lighting device and method are used, for example, to illuminate an operating table. A patient is lying on this operating table, undergoing medical treatment. The lighting allows the attending physician to perform the medical treatment while clearly viewing the area of ​​the patient's body to be treated.

[0005] The lighting inevitably introduces radiant energy into the patient's body, thereby heating the patient's body. If the lighting is too strong, there is a risk of the patient's tissue drying out and / or suffering burns.

[0006] For lighting devices that can illuminate an operating table, the standard IEC 60601 -2-41 applies, currently the 3 rd ed. This standard specifies that the maximum irradiance of a lighting unit of a medical lighting device shall not exceed the current 1000 W / m A 2, in the future 700 W / m A 2. This requirement applies to any distance between the lighting device and the operating table, measured along the central axis of the lighting device, and at any time.

[0007] The invention is based on the object of providing a lighting device and a lighting method that reduce the risk of the object, for example, the patient, being endangered by the lighting with relatively high reliability. This object is achieved by a lighting device having the features of claim 1 and by a lighting method having the features of claim 1. Advantageous embodiments of the lighting device according to the invention are, where appropriate, also advantageous embodiments of the lighting method according to the invention, and vice versa.

[0008] Below we first define some terms for medical lighting units that will be used subsequently.

[0009] A lighting unit comprises at least one light source, preferably a plurality of light sources, wherein the light sources are attached to a support and are preferably configured as LEDs. In one implementation, the position and orientation of a light source relative to the position and orientation of the or any other light source of the same lighting unit is unchangeable during use. It is also possible for at least one light source, in particular an assembly comprising a plurality of light sources, to be assigned a controllable actuator, wherein the actuator can move this light source or assembly relative to the support and thus also relative to the or at least one other light source.

[0010] The or each light source emits a light beam, which is usually conical in shape. In one implementation, the apex of this cone ideally lies within the light source. It is also possible for optics to influence the shape of the light beam. A special case is a cylindrical light beam. The light beams produced by the light sources of a lighting unit usually overlap. A lighting unit has an optical center axis, which often coincides with the geometric center axis of the support.

[0011] The illuminance unit has a spectral composition of the emitted light. This spectral composition of the illuminance unit results from the spectral compositions of the light from the individual light sources and is referred to below as the "light spectrum" of the illuminance unit. A color temperature is correlated with the light spectrum. The "illuminance" (Ev) describes the luminous flux per unit area that hits a surface. The SI unit is lux = lumen / m A 2. In a plane perpendicular to the optical center axis of a lighting unit, the illuminance of the

[0012] Lighting unit typically has the maximum value at the intersection point of the central optical axis with this plane. As a rule, this maximum illuminance value varies along the central optical axis as follows: starting from the lighting unit, this maximum value increases until it reaches a maximum and then decreases again. The value at this maximum is referred to as the “maximum spatial illuminance” of the lighting unit. As a rule, the maximum spatial illuminance occurs on the central optical axis. The region where the illuminance assumes the maximum value can be on an illuminated surface or between it and the lighting unit. If the surface were transparent, at a sufficiently small distance this region could also lie behind the illuminated surface in the direction of radiation.

[0013] As a rule, the maximum illuminance in a room that a lighting unit can achieve is known due to the design of the lighting unit or due to measurements performed before its first use, in particular due to the illuminances of the light sources and the relative positioning of the generated light beams. The design of the lighting unit or measurements performed also determine how the maximum illuminance value on the optical center axis depends on the distance. This functional dependence of the illuminance on the distance may depend on other adjustable or design-related parameters of the lighting unit.

[0014] Often, a user can cause the actual maximum illuminance in the room to be lower than the maximum achievable illuminance in the room through user input or automatically through a control device. In the following, we will refer to the "maximum achievable" and the "maximum currently achieved" illuminance in the room. The maximum currently achieved illuminance is lower than or equal to the maximum achievable illuminance in the room. The maximum illuminance actually achieved on the surface generally depends on the position and orientation of the lighting unit relative to the surface, whereas the maximum achievable illuminance in the room depends neither on the position nor on the orientation.

[0015] A user can often set the maximum illuminance of a lighting unit and change it during operation. In one implementation, the user can set the maximum illuminance in the room. In another implementation, the user can set the maximum illuminance at a specified reference distance from the lighting unit. In the case of operating room lights, this reference distance is often 1 m. The maximum illuminance at the reference distance is equal to or less than the maximum achievable illuminance at the reference distance. Often, the maximum illuminance in the room of a medical lighting unit is achieved at a distance that differs by no more than 10 cm from the reference distance.

[0016] When the lighting unit illuminates the surface of an object, such as an operating table or a patient on the operating table, the illuminance varies across the illuminated surface. Ideally, the illuminance achieved by the lighting unit on the illuminated surface reaches a maximum value at one point. This maximum value is referred to as the maximum illuminance actually achieved by the lighting unit on the illuminated surface. This maximum value is equal to or less than the maximum illuminance of the lighting unit in the room. The maximum value is generally assumed to occur at the intersection point of the optical central axis of the lighting unit with the illuminated surface, even if the illuminated surface is curved, which is the case with an illuminated patient, and / or oblique to the central axis.In the following, we refer to "the distance" between a lighting unit and an illuminated surface. Unless explicitly stated otherwise, this distance refers to the distance along the optical center axis between the lighting unit and the illuminated surface, even if the smallest distance between the lighting unit and the illuminated surface occurs outside the optical center axis.

[0017] Illuminance is the most important factor that describes the brightness of an illuminated surface.

[0018] In the case of a medical lighting unit, "illuminance" often refers to the illuminance at a reference distance of, for example, 1 m between the lighting unit and the illuminated surface, with the illuminated surface perpendicular to the optical center axis of the lighting unit. The lighting unit is often designed so that, ideally, the maximum illuminance in the room occurs on the optical center axis and at the reference distance from the lighting unit. In practice, this target cannot usually be achieved exactly.

[0019] How bright a surface appears to an observer, whether it is luminous on its own or due to reflection, is measured in luminance (“luminance”) in Cd / m A2. If the surface does not glow on its own, the luminance depends on the illuminance on the surface and on the reflection / absorption behavior of the surface.

[0020] Irradiance (Ee) refers to the power per unit area of ​​light radiation incident on a surface. The SI unit is W / m A2. Irradiance is also referred to as "radiant intensity" or "radiant flux density," or more obsoletely as "radiant flux density." The irradiance of a lighting unit at a point is proportional to the illuminance at that point, with the proportionality factor depending on the light spectrum of the lighting unit. Therefore, with a constant proportionality factor, the maximum irradiance and the maximum illuminance in the room occur in the same area. Depending on the illuminance, the term "maximum irradiance" is also used to describe the illuminance produced by a lighting unit on an illuminated surface. This maximum illuminance also typically reaches its maximum value at the intersection point of the optical center axis of the lighting unit with the illuminated surface. This maximum value is also referred to as "peak irradiance."

[0021] Under the light field diameter dx is understood as the diameter of a circle around the area of ​​maximum illuminance, where this circle is defined such that an average value of the respective illuminance at different points of this circle is equal to x% of the maximum illuminance in the plane of this circle. The points are, for example, evenly distributed over the circle. The plane of this circle is perpendicular to the optical center axis of the lighting unit. Typical values ​​for x in the medical field are 10% and 50%. For surgical lights, d is usually between 13 cm and 35 cm. Because the light field diameter d x usually depends on the distance between the lighting unit and the plane of this circle, the light field diameter d x relative to a reference distance, which in medical applications is often 1 m. In many cases, a user can change the light field diameter dx is set to a desired value. Note: Because the irradiance is proportional to the illuminance, the same light field diameter d results. x , if the light field diameter d x refers to irradiance instead of illuminance.

[0022] In the medical field, it is often desired or even required by a standard, for example, the IEC 60601-2-41 standard for surgical lights, that 2*dso > dio should apply for a lighting unit. This requirement results in a boundary condition for how the light beams of the light sources of a lighting unit are positioned relative to each other.

[0023] A "light field" is the area on an object's surface illuminated by a lighting unit. Two properties of a light field are the illuminance profile and the irradiance profile. These two profiles assign an illuminance and an irradiance, respectively, to each point on the illuminated surface. These two profiles differ from each other only by a proportionality factor, which depends on the light spectrum of the lighting unit.

[0024] As a rule, if the illuminated surface is a plane, the curve on the illuminated surface where the illuminance and irradiance are x% of the maximum illuminance or irradiance, respectively, has the shape of an ellipse, in particular a circle, around the point of maximum illuminance or irradiance. In a three-dimensional representation, where the illuminated surface extends in the xy-plane and the respective illuminance or irradiance at a point (x, y) is plotted on the z-axis, the light field often has an approximate shape of a bell-shaped curve that is rotationally symmetrical to the z-axis.

[0025] The illuminance, irradiance, light field, and light field diameter of a lighting unit can, of course, vary over time, particularly due to user actions, especially when moving the lighting unit. Unless otherwise stated, the respective current value is meant.

[0026] When light hits a body, the body absorbs some of the light and reflects the rest. "Heat energy", also called thermal energy, has the unit joule. The input of heat energy into an illuminated body is the integral of the absorbed irradiance over the illuminated area and over time, namely over the time the object is illuminated. An illuminated body, for example a patient on an illuminated operating table, receives an input of heat energy from a lighting device that illuminates the operating table, optionally an input of heat energy from other energy sources, for example a heater for the operating table, a radiant heater or the ambient temperature. The body releases heat energy into the environment, particularly depending on its body temperature and the ambient temperature.After a transient phase, thermal equilibrium is established, where the input of heat energy equals the output of heat energy. The patient's body temperature often rises slightly, and this rise establishes this thermal equilibrium.

[0027] On the one hand, it is desirable to provide good illumination for the area of ​​the patient's body where medical treatment is taking place. This is achieved through high light intensity and / or illuminance. However, high illuminance also leads to a high maximum irradiance. On the other hand, to avoid endangering the patient, the maximum total irradiance should not be too high. If the maximum total irradiance on the illuminated surface of the patient is too high, burns and / or dehydration can occur.

[0028] As a rule, a medical operating light produces a maximum of 50W of heat energy. However, the term "heat energy" describes the exposure of a patient's body to lighting, averaged over space and time. Particularly in medical applications, a specific area of ​​the body is often brightly illuminated so that a doctor can safely perform a medical treatment. This can lead to high local exposure to radiation. The thermal equilibrium described above therefore occurs much later in this area than averaged over the entire body. In addition, the irradiance can change rapidly, particularly when an operating light is turned up. One consequence: In this area or in a smaller sub-area of ​​the body, significantly higher temperatures are reached than in the rest of the body.These temperature differences often cannot be effectively and quickly compensated either by processes within the patient's own body or by releasing heat into the environment. This can lead to a wound partially drying out, a localized heating of an area of ​​the body, and, in extreme cases, even minor burns. Therefore, the invention does not limit, or at least not only, the heat energy as defined in the previous paragraph.

[0029] The invention reduces the risk of patient harm due to an excessively high maximum total irradiance of the lighting device. The maximum total irradiance is a measure of the current radiant power that the lighting device exerts locally and currently on the patient's body. This distinguishes the maximum total irradiance from thermal energy, which is, in a sense, averaged across the patient's body and integrated over time.

[0030] The lighting device according to the invention comprises at least two lighting units, each lighting unit capable of illuminating the same surface. Therefore, in many cases, the illuminated surface, and thus an object on the illuminated surface, is illuminated from multiple sides, which is often not possible with a single lighting unit. This feature reduces the effect of shadowing caused by an object coming into the area between the lighting device and the illuminated surface. Such an object is, for example, a medical instrument or a body part of a treating physician.

[0031] Preferably, the respective position and orientation of each lighting unit relative to the illuminated surface can be changed independently of the respective position and orientation of the or any other lighting unit of the lighting device. One limitation: Of course, two lighting units cannot penetrate each other, and a lighting unit cannot penetrate another object.

[0032] The lighting device according to the invention thus comprises at least two lighting units. Each lighting unit emits light and generates a light field and thus an irradiance on the illuminated surface, for example, on the illuminated surface of the patient or the operating table. Of course, it is possible for at least one lighting unit to be switched off at any given time.

[0033] The light fields of the lighting units overlap additively. The "total irradiance" of the lighting device refers to the irradiance that the lighting device currently achieves on the illuminated surface through its lighting units. The total irradiance also reaches a maximum on the illuminated surface, which is referred to as the maximum total irradiance, and can vary over time. The maximum total irradiance depends on the maximum irradiances achieved by the lighting units of the lighting device on the illuminated surface, as well as generally on the positions of the light fields relative to each other on the illuminated surface and, to a lesser extent, on the light field diameter and / or the correlated color temperature.

[0034] The lighting device according to the invention further comprises a signal-processing control unit. The control unit is capable of controlling each lighting unit independently of the lighting unit or any other lighting unit of the lighting device. One goal and thus one effect of the control is to change, in particular to reduce, the maximum irradiance of the controlled lighting unit. Optionally, the control unit is capable of changing the light field diameter and / or the correlated color temperature of the lighting unit through the control.

[0035] Typically, each lighting unit comprises several individual light sources, particularly LEDs. Preferably, each lighting unit comprises at least two groups of light sources, with each light source group comprising at least one light source. Preferably, the control unit is capable of controlling each light source group independently of the or any other light source group of the lighting unit, and the maximum irradiance of this light source group is changed by the control. It is also possible for the light sources of a lighting unit to be controlled only together, meaning that all light sources of a lighting unit belong to the same light source group.

[0036] Each individual light source, and thus each light source group, generates a maximum irradiance on the surface. To change the maximum irradiance of the controlled lighting unit, the control unit causes the respective maximum irradiance of at least one light source group to be changed.

[0037] To change the maximum irradiance of a light source group, the control unit assigns a different value to a luminous intensity parameter of the light source group. In one implementation, the control unit changes the maximum irradiance that the light source group can generate in the room. In another implementation, the control unit changes the light field diameter or the light spectrum, with which a color temperature is correlated, by controlling the light source group. These implementations can be combined.

[0038] A lighting unit preferably comprises at least two different light source groups that can be controlled independently of one another. In one embodiment, the control unit causes a different value to be assigned to a luminous intensity parameter of at least one light source group, while at least one other light source group remains unchanged. In another embodiment, the values ​​of the luminous intensity parameters are changed in a similar way, for example, by the same factor or by the same absolute value.

[0039] The lighting device according to the invention is capable of detecting a user specification. This user specification relates to the maximum total irradiance of the lighting device or the maximum irradiance of at least one lighting unit. "Relate" means: the user specification causes or is at least suitable for changing the maximum total irradiance or the maximum irradiance. The user specification can, in particular, relate to the maximum irradiance to be achieved in the room, optionally the light field diameter or the correlated color temperature of the lighting device or the lighting unit. The user specification can specify a value for this parameter or also include a specification to change the current value, for example, using a slider or using a plus and minus button.

[0040] The control unit is designed to automatically respond to the detection of the user input as follows:

[0041] The control unit predicts at least approximately the maximum total irradiance the lighting device will achieve on the surface when the lighting device is operated according to the user specification. Preferably, the control unit makes the prediction under the assumption that the lighting device is modified according to the user specification and otherwise operated unchanged, in particular that the respective distance between each lighting unit and the illuminated surface remains unchanged, and that, apart from the user specification, each maximum irradiance remains unchanged. Typically, the maximum total irradiance predicted by the control unit is an estimate of the maximum irradiance on the surface that would actually result from implementing the user specification.

[0042] An upper limit is specified for the maximum total irradiance that the lighting device actually achieves or is permitted to achieve on the surface. This upper limit can be specified in particular by a user or by a higher-level control system. If the upper limit is exceeded, there is a risk that an illuminated person will be injured or otherwise harmed. In one embodiment, this upper limit is fixed and cannot be changed. In another embodiment, a maximum possible upper limit is fixed, for example due to legal requirements or due to a specification by a manufacturer or user of the lighting device. A user through a corresponding user input or also a higher-level control system can cause a lower upper limit to actually be used.The control unit detects the fixed upper limit or the upper limit specified by the user or the higher-level control.

[0043] The control unit compares the predicted maximum total irradiance with this specified upper limit. If the predicted maximum total irradiance is greater than the upper limit, the control unit controls at least one lighting unit of the lighting device. This control depends on the detected user specification. One goal of the control is preferably that the user specification is realized as desired or at least as far as possible. During the control, the control unit ensures that the following boundary condition is met: The actually achieved maximum total irradiance of the lighting device after the control is less than or equal to the specified upper limit. As a rule, the control depends on the user specification and the predicted maximum total irradiance.A special case is that the control unit leaves the lighting device unchanged because even a partial implementation of the user specification would result in the upper limit being exceeded.

[0044] The control unit therefore ideally ensures through control that the specified upper limit is not exceeded by implementing a user specification as desired by the user. "Ideally" means that the prediction is an estimate that may deviate from reality and that the control unit preferentially uses signals from sensors for the prediction, although these signals may also be incorrect. Because the upper limit is ideally adhered to, the risk of an illuminated patient being injured by excessive maximum irradiance, or of the eyes of a nearby person being overloaded, or of an object being damaged, is reduced. The invention eliminates the need for the user to ensure that the upper limit is not exceeded when entering the user specification.This applies in particular to a user setting that does not directly specify a value or an increase in the maximum total irradiance, but rather another parameter that affects the maximum total irradiance, for example the maximum irradiance of an illumination unit or a light field diameter.

[0045] It is possible for the lighting device to comprise an input unit with which the user can change the maximum total irradiance. This input unit can be designed such that the user cannot increase the maximum total irradiance beyond the upper limit. The invention can be combined with such a design. However, the invention enables the user to change further parameters of the lighting device, for example the maximum irradiance of a lighting unit or a light field diameter or a correlated color temperature. According to the invention, the control unit prevents the upper limit for the maximum total irradiance from being exceeded in this case too, without the input unit having to be designed accordingly and without the user having to ensure that the upper limit is adhered to.

[0046] In one embodiment, the control unit subsequently calculates the maximum total irradiance actually achieved by the lighting device on the surface. This embodiment is described in more detail below. According to the invention, the control unit additionally or instead predicts a maximum total irradiance that would result from the user specification if the user specification were implemented as desired. If this would result in the upper limit being exceeded, the control unit prevents the upper limit from actually being exceeded by appropriately controlling at least one lighting unit. A special case is that the control unit leaves the lighting device unchanged, i.e. does not implement the user specification, because otherwise the upper limit would be exceeded.The invention thus prevents the undesirable event of initially exceeding the upper limit, subsequently detecting this event, and subsequently reducing the maximum total irradiance again. Such an effect could, in particular, endanger a patient and / or strain or fatigue the eyes of a person in the vicinity of the illuminated surface.

[0047] The invention can be operated in combination with a configuration in which the control unit continuously determines the current, actually achieved, maximum total irradiance, for example, using a fixed sampling frequency. How quickly an exceedance of the upper limit is detected in this configuration depends on the respective sampling frequency of the control unit and that of optional sensors, as well as on the computing capacity of the control unit. Thanks to the invention, however, this continuous sampling is not necessary. Rather, the maximum total irradiance is predicted as needed, namely after a user specification has been recorded. In some cases, this feature saves computing capacity and / or computing time of the control unit.

[0048] The following configuration is possible: If the predicted maximum total irradiance is greater than the upper limit, the control unit causes a corresponding message, in particular an alarm, to be output in at least one form that can be perceived by a person. However, because according to the invention the control unit automatically controls at least one lighting unit when the upper limit is exceeded, the invention obviates the need to output such a message. This is particularly advantageous because, especially in everyday clinical practice, people are often inundated with numerous messages. The invention therefore reduces the risk that the maximum total irradiance is exceeded significantly or for a longer period of time because a user fails to perceive a corresponding message or does not react correctly to such a message.It is possible for the control unit to control at least one lighting unit and additionally cause the message to be output. According to the invention, the control unit predicts the maximum total irradiance the lighting device would achieve on the illuminated surface if the user specification were implemented as desired. According to the invention, the control unit uses the detected user specification regarding the maximum total irradiance or the maximum irradiance of at least one lighting unit. Different configurations are possible regarding which additional information the control unit uses to predict the maximum total irradiance. The invention can also be implemented without this additional information.

[0049] Preferably, the control unit determines and uses the respective maximum irradiance of each lighting unit, whereby the lighting unit actually achieves this maximum irradiance on the illuminated surface. Typically, the control unit uses an approximate value for the actual maximum irradiance.

[0050] In one implementation, a maximum irradiance achievable in the room is specified for each lighting unit. Due to its design and manufacture, the lighting unit can only achieve this maximum irradiance, whereby this maximum does not necessarily occur on the illuminated surface, but rather, for example, at a reference distance of 1 m. The maximum irradiance actually achieved by the lighting unit in the room is less than or equal to the maximum achievable irradiance in the room and depends on the control of the lighting unit. The maximum irradiance achieved on the surface, in turn, is less than or at most equal to the maximum irradiance achieved in the room.

[0051] In one embodiment, the control unit uses the maximum irradiance actually achieved in the room by a lighting unit as the maximum irradiance achieved on the surface and determines the maximum irradiance achieved in the room based on the maximum achievable irradiance and the control of the lighting unit. The maximum irradiance approximately determined in this way may be greater than the maximum irradiance actually achieved on the surface, but generally not less.

[0052] In another embodiment, it is taken into account that the maximum irradiance achieved by a lighting unit on the illuminated surface depends on the distance between the lighting unit and the surface and can therefore be lower than the maximum irradiance achieved by the lighting unit in the room. According to this other embodiment, the lighting device comprises at least one distance sensor. In one implementation, a distance sensor is connected to each lighting unit, wherein the position and orientation of the connected distance sensor relative to the lighting unit cannot be changed. The or each distance sensor measures a measure of the distance between itself and the illuminated surface. In many cases, this measured distance can be used as the distance between the lighting unit and the illuminated surface.Optionally, a lateral offset between the distance sensor and the optical center axis of the lighting unit is also used. This lateral offset is predetermined by the design and remains constant during operation. The control unit uses the maximum irradiance achieved in the room and the measured distance to determine the maximum irradiance achieved on the surface.

[0053] Different implementations of this distance sensor are possible. In one implementation, the distance sensor emits electromagnetic radiation or sound waves towards the surface. The surface reflects at least a portion of the electromagnetic radiation or sound waves, a portion of which hits the distance sensor again. The travel time of the electromagnetic radiation or sound waves is measured. The travel time is a measure of the desired distance. It is also possible to measure the attenuation, with the attenuation being a measure of the distance. In another implementation, the illumination unit is connected to a camera aimed at the surface and including an autofocus function. This autofocus function automatically focuses the camera on the illuminated surface. The distance sensor detects the distance at which the autofocus function has focused the camera.This autofocus distance is an estimate of the desired distance. This design eliminates the need for a separate distance sensor. In many cases, such a camera is already present, for example, to enable the illuminated surface to be visually displayed on a spatially distant output device.

[0054] In one implementation, the camera is positioned and configured so that at least one image from the camera shows all or at least some of the light fields generated by the lighting units on the surface. The control unit evaluates this image and determines the size of each light field in this image. Furthermore, the control unit records the light field diameter for each lighting unit. x This illumination unit has a predetermined reference distance, for example, by reading data from a data storage device. The light field diameter d xThe reference distance is a design-related parameter that can be changed by the user, but it is independent of the desired distance. The control unit compares the sizes of the light fields in the image with the light field diameters at the reference distance and derives the respective distance from the comparison result. The reference distance is, of course, predetermined for the control unit.

[0055] The image described above alone shows multiple light fields on the surface, assuming multiple lighting units are switched on. In one embodiment, the control unit automatically determines which light field originates from which lighting unit. In many cases, the camera is permanently connected to a lighting unit. The control unit records the constant position and orientation of the camera relative to the optical center axis of the lighting unit. In one embodiment, at least one lighting unit is permanently connected to a distance sensor. The measured distance between this lighting unit and the surface, the light field diameter d x of this illumination unit and the diameters of the light fields in the image enable the control unit in many cases to identify the light field that originates from the illumination unit with the distance sensor.

[0056] It is possible for the control unit to detect the set light field diameter at a reference distance from at least one lighting unit without a distance sensor and to determine, through an automatic plausibility check, which light field in the image can originate from this lighting unit and which cannot.

[0057] In a preferred embodiment, the distance sensor is capable of contactlessly scanning the illuminated surface and thereby generating a topographical 3D profile of the illuminated surface. Such a distance sensor is known as a "time-of-flight sensor" and is described, for example, in DE 10 2013 012 231 A1 and DE 10 2012 014 716 A1. The control unit uses this topographical profile to determine the maximum irradiance of the connected lighting unit, the maximum total irradiance, and / or the distance between the lighting unit and the surface.

[0058] In one embodiment, the control unit uses the topographical profile to determine the minimum distance between the topographical profile of the illuminated surface and the lighting unit. This minimum distance can be smaller than the distance along the optical center axis. The control unit uses this minimum distance as well as the maximum irradiance in the space surrounding the lighting unit to determine the maximum irradiance on the surface of the lighting unit. It is also possible for the control unit to derive and use an averaged distance from the topographical profile.

[0059] According to the embodiment just described, the control device determines the maximum irradiance achieved by a lighting unit on the surface, depending on the irradiance achieved by the lighting unit in the room and the measured distance between the lighting unit and the illuminated surface.

[0060] The control unit preferably uses a characteristic curve that specifies a factor as a function of the distance. This factor specifies the percentage of the maximum irradiance achievable in the room that the lighting unit can actually achieve at this distance. This characteristic curve is known from the design of the lighting unit or is determined empirically in advance. The characteristic curve is preferably stored in a data memory to which the control unit has at least temporary read access.

[0061] In one embodiment, the control unit predicts the maximum total irradiance as follows: as the sum of the maximum irradiances of the lighting units, whereby if the user specification refers to a lighting unit, the maximum irradiance to be achieved according to this user specification is used. The maximum irradiance results from the maximum achievable irradiance and the control of a lighting unit. Preferably, those lighting units that are switched off or defective are not taken into account in this summation. This embodiment does not require a signal from a sensor, in particular not a measured distance, but can lead to a maximum total irradiance that is too high being predicted, but not to a maximum total irradiance that is too low.

[0062] Each illumination unit creates a light field on the illuminated surface. The term "light field" has already been defined above. If the illuminated surface is perpendicular to the optical center axis of the illumination unit, an irradiance of more than x% of the maximum irradiance occurs within a circle, where x is, for example, 10%, and the center of this circle is the intersection point of the optical center axis with the surface. The diameter of this circle is the light field diameter d. x The circles of the lighting units can be arranged concentrically, in which case the maximum total irradiance is ideally equal to the sum of the maximum irradiances of the lighting units. However, if the centers of these circles do not coincide, this sum is usually greater than the maximum total irradiance.

[0063] In one embodiment, the control unit is capable of at least approximately determining how the light fields are positioned relative to one another. The lighting units generate these light fields on the illuminated surface. The control unit uses the user specification, the maximum irradiances of the lighting units, and additionally the determined positioning of the light fields relative to one another to predict the maximum total irradiance.

[0064] Various configurations are possible as to how the control unit determines how the light fields of the lighting units are positioned relative to one another. In these configurations, the control unit preferably determines in particular how far apart the two points of intersection of the two optical center axes of two lighting units are from the illuminated surface. With two lighting units, there is one such distance, with three lighting units, there are three such distances, and with four lighting units, there are already six such distances, provided that all lighting units are switched on simultaneously and are taken into account in the prediction and in the optional determination of the maximum total irradiance. A distance between two points of intersection can of course be zero.

[0065] It is possible for each lighting unit to be connected to a distance sensor and an orientation sensor. The distance sensor measures the distance between the lighting unit and the illuminated surface. The orientation sensor measures the position of the optical center axis of the lighting unit in space. The control unit uses signals from these two sensors to determine how the light fields are positioned relative to each other.

[0066] In one embodiment, the two or at least two lighting units are each connected to a distance sensor. The position and orientation of the distance sensor relative to the connected lighting unit is fixed. Each of these at least two distance sensors is capable of non-contact scanning of the illuminated surface. The distance sensors provide at least two topographical 3D profiles of the illuminated surface, in many cases from different viewing directions. The control unit compares the topographical profiles and uses the result of this comparison to determine how the light fields of the lighting units are positioned relative to each other on the surface.Preferably, the control unit additionally uses the design-related position and orientation of the distance sensor on a lighting unit relative to the optical center axis of the lighting unit to derive the position and orientation of the optical center axis relative to the topographical profile. Preferably, the control unit derives the distance between the intersection points of the optical center axes and the surface from the comparison of the two topographical profiles. In many cases, the control unit is also capable of determining the position of a third light field relative to the first two light fields, even if this third light field originates from a lighting unit that is not connected to such a distance sensor.

[0067] According to the invention, the control unit is capable of controlling each lighting unit of the lighting device independently of the or each other lighting unit. According to one implementation, the control unit is capable of controlling the lighting units as follows within a measurement period: In a first alternative, at any time within the measurement period, exactly one lighting unit is switched on, and the or each other lighting unit is switched off. In a second alternative, at any time within the measurement period, exactly one lighting unit is switched off, and the or each other lighting unit is switched on. This measurement period is used to determine how the light fields of the lighting units are positioned relative to one another. Preferably, the frequency with which the lighting units are switched on and off is such that a person does not perceive flickering, but rather a continuous illumination of the surface.According to this other embodiment, the lighting device comprises an image recording system. The image recording system comprises at least one camera. In one embodiment, a camera is arranged at each lighting unit. The image recording system is capable of generating a sequence of images of the illuminated surface. The respective light field of each lighting unit lies in the field of view of at least one camera of the image recording system. The sequence is generated as follows: For each lighting unit, the sequence comprises at least one image of the illuminated surface, wherein this image was generated while, in the first alternative, this lighting unit is switched on and in the second alternative, off. This image therefore shows only the light field of this lighting unit in the first alternative and only the respective light field of the or each other lighting unit in the second alternative.The sequence therefore contains at least as many images as the lighting device has lighting units. Each image in this sequence is provided with a timestamp (the time the image was created).

[0068] The control unit evaluates the sequence of images. Preferably, the control unit computationally overlays the images in the sequence. The control unit uses the images with their time stamps, as well as the times at which each lighting unit is switched on or off, to determine which light field on the surface originates from which lighting unit. The control unit, in turn, uses this information to determine how the light fields are positioned relative to each other.

[0069] Thanks to this design, the positioning of the light fields can be determined even if all lighting units emit light with the same light spectrum. Furthermore, while it is possible, this design eliminates the need to measure the respective position and orientation of each lighting unit in the room.

[0070] In one application, this configuration can also be used to determine the distance between a lighting unit and the illuminated surface. The size of this light field in the image and the light field diameter at the reference distance of this lighting unit provide an estimate of the distance between this lighting unit and the surface.

[0071] As already explained, the irradiance of a lighting unit is proportional to the illuminance, whereby the proportionality factor depends on the light spectrum of the lighting unit. In one embodiment, the control unit determines the respective light spectrum of each lighting unit. The light spectrum of a lighting unit depends on the design-specific light spectra of the aforementioned light source groups of this lighting unit as well as on the respective maximum irradiance of this light source group. The control unit uses the determined light spectra to predict the maximum total irradiance and, optionally, to determine the actually achieved maximum total irradiance.

[0072] The maximum irradiance of a lighting unit may also depend on the angle at which the optical center axis of the lighting unit intersects the illuminated surface. In one embodiment, the control unit determines the respective angle for each lighting unit and uses the determined angles to predict the maximum total irradiance and, optionally, to determine the actually achieved maximum total irradiance.

[0073] According to the invention, the control unit predicts the maximum total irradiance in response to the detection of a user input. If the predicted maximum total irradiance is greater than the specified upper limit, the control unit controls at least one lighting unit, thereby preventing the upper limit from being exceeded, or at least significantly exceeded.

[0074] Different designs are possible as to how the control unit ensures that the upper limit is not exceeded through control. In one design, the user specification relates to the maximum total irradiance. For example, the user specifies that the maximum total irradiance to be achieved should be increased. In response to the detection of this user specification, the control unit preferentially controls each lighting unit - optionally with the exception of those lighting units that are switched off or defective. Through control, the control unit changes the respective maximum irradiance of each lighting unit according to the user specification, in such a way that the upper limit is not exceeded. It is possible that as a result of this specification, the user specification is not realized exactly as desired, i.e. remains lower than desired by the user.This configuration is particularly advantageous when the maximum total irradiance has already reached or nearly reached the upper limit and the user specifies an increase in the maximum total irradiance. It is even possible for the lighting device to remain unchanged.

[0075] In one implementation of this configuration, the control unit causes the respective maximum irradiance of each lighting unit to be changed by the same factor. In another implementation, the control unit causes the maximum irradiance of the lighting unit that currently achieves the highest or lowest maximum irradiance of all lighting units in the lighting device to be changed.

[0076] In another embodiment, the user specification relates to a specific first lighting unit selected by the user. For example, the user wishes to have a specific area on the illuminated surface more brightly illuminated, for example because medical treatment is to be carried out on a patient in this area. The user therefore specifies that the maximum irradiance and / or the light field diameter and / or the color temperature of a first lighting unit directed at this area should be changed, in particular increased. In this other embodiment, the control unit preferably controls the first lighting unit to which the user specification relates, and thereby causes the maximum irradiance of the first lighting unit to be changed, ideally in accordance with the user specification.If the control increases the maximum irradiance of the first lighting unit according to the user specification and everything else remains unchanged, the maximum total irradiance could exceed the specified upper limit. According to the invention, in this alternative embodiment, the control unit also predicts what maximum total irradiance would be achieved by implementing this user specification, i.e., if the maximum irradiance of the first lighting unit is changed as specified by the user.

[0077] Preferably, the control unit causes the first lighting unit to be changed according to the user specification. If this change would exceed the upper limit, the control unit selects a different lighting unit, controls it, and thereby causes the maximum irradiance of this other lighting unit to be reduced. The goal of this control is for the maximum total irradiance to be at most equal to the upper limit. If the lighting device comprises at least three lighting units, it is possible for the control unit to select several other lighting units and reduce the respective maximum irradiance of these selected other lighting units.

[0078] This configuration makes it possible in many cases for a specific area on the illuminated surface to be illuminated differently, in particular more intensely, than before, as desired by the user, namely by the first lighting unit, while still not exceeding the upper limit. Preferably, the control unit selects at least one other lighting unit, with the light field of this other lighting unit and the light field of the first lighting unit overlapping only to a relatively small extent or not at all. It is also possible for the control unit to select, as the other lighting unit, the lighting unit that currently achieves the highest maximum irradiance among all other lighting units.

[0079] It is possible for at least a first lighting unit of the lighting device to be directed at a first region of the illuminated surface, in particular at a first region of a patient on an operating table. The first region is particularly sensitive to the introduction of thermal energy and includes, for example, the chest or face of the patient. At least one further lighting unit is directed at another region that is less sensitive to thermal energy. Preferably, the respective light field of the or each first lighting unit and the respective light field of the or each further lighting unit do not overlap, or at least do not overlap significantly. Frequently, the upper limit only needs to be observed for this first region.

[0080] In this application, it is important that the maximum total irradiance achieved by the first lighting units is less than or equal to the upper limit. The maximum irradiances of the second lighting units are preferably not taken into account. This configuration allows the first area to be illuminated as brightly as possible or as desired without exceeding the upper limit.

[0081] In one embodiment, the control unit therefore determines a subset of lighting units, i.e., the first lighting units of the application just mentioned. The subset of lighting units comprises at least one lighting unit of the lighting device. At least one further lighting unit of the lighting device belongs to the remaining set, i.e., does not belong to the subset of lighting units. The control unit is capable of determining the respective maximum irradiance of each lighting unit in the subset of lighting units. To predict the maximum total irradiance of the lighting device, the control unit uses the user specification, the determined maximum irradiances of the (first) lighting units in the subset of lighting units, and optionally, the information regarding how the light fields of these first lighting units are positioned relative to one another.Preferably, the control unit does not use the irradiance levels of the other lighting units.

[0082] Different implementations are possible as to how the control unit determines the lighting unit subset.

[0083] In one implementation, the lighting device detects a corresponding user preference. In one implementation, the user preference specifies the or each lighting unit of the lighting unit subset; in another implementation, the user preference specifies the or each lighting unit of the lighting device that does not belong to the lighting unit subset. In many cases, a user can reliably specify which lighting units are directed at the heat-sensitive area.

[0084] Another implementation can be combined with the configuration described above, in which the control unit determines how the light fields of the lighting units are positioned relative to one another. Based on this combination, the control unit determines overlapping light fields. The lighting units that generate these overlapping light fields belong to the lighting unit subset. Any additional lighting unit does not belong to the lighting unit subset. The light field of the or each additional lighting unit therefore does not overlap with the light fields of the lighting units in the lighting unit subset.

[0085] According to the invention, the control unit predicts a maximum total irradiance, specifically in response to the event that a user specification has been detected. This user specification relates to the maximum total irradiance or to a maximum irradiance of a lighting unit. The control unit implements this user specification such that the maximum total irradiance does not exceed the upper limit. In one embodiment, the control unit is additionally capable of subsequently determining the actually achieved maximum total irradiance and reducing it if necessary. The process by which the control unit determines the achieved maximum total irradiance is triggered by the control unit detecting an irradiance-relevant event. This irradiance-relevant event changes the maximum total irradiance or is at least capable of changing it.The event has already occurred and can only be verified retrospectively, whereas according to the invention, the user specification is first verified and then implemented as described above. Typically, the irradiance-relevant event is triggered by user intervention or action.

[0086] According to this embodiment, the control unit determines at least approximately the maximum total irradiance achieved by the lighting device on the surface after the irradiance-relevant event. If this determined maximum total irradiance is greater than the upper limit, the control unit controls at least one lighting unit. The control unit thereby causes the maximum total irradiance to be (re)reduced. This embodiment reduces the risk that the maximum total irradiance will be greater than the upper limit over a longer period of time. Nevertheless, thanks to this embodiment, it is not necessary to continuously determine the current actual maximum total irradiance at a high sampling frequency.Rather, the maximum total irradiance is determined again at least when necessary, namely when an irradiance-relevant event is detected, i.e. an indication of a possible change in the actual maximum total irradiance.

[0087] In one implementation, the control unit controls all lighting units of the lighting device and causes the respective maximum irradiance of each lighting unit to be reduced, for example, by the same percentage or by the same absolute amount. It is also possible for the control unit to only reduce the maximum irradiance of those lighting units that do not belong to the subset of lighting units described above. Various configurations are possible, depending on which irradiance-relevant event the control unit is capable of detecting.

[0088] In one embodiment, the lighting device comprises at least one distance sensor, preferably one distance sensor per lighting unit. The or each distance sensor is capable of measuring a measure of the distance between itself and the illuminated surface. The control unit detects an event that at least one measured distance has changed, in particular has been reduced, by more than a predetermined lower limit as an irradiance-relevant event. Because the maximum irradiance of a lighting unit depends on the distance between the lighting unit and the surface, a changed distance of a lighting unit can lead to a changed maximum total irradiance.

[0089] In another embodiment, the lighting device comprises at least one touch sensor, preferably one touch sensor per lighting unit. The or each touch sensor is capable of detecting the event that a user has touched the touch sensor and thus the connected lighting unit. For example, this touch sensor is mounted on a handle of the lighting unit. A user touches the lighting unit, in particular a handle of the lighting unit, typically with the aim of changing the distance between the lighting unit and the illuminated surface and / or the orientation of the lighting unit.

[0090] According to the invention, the control unit is capable of controlling each lighting unit independently of the or any other lighting unit, wherein the objective of this control is or can be to change the maximum irradiance of this lighting unit. Through the control, the control unit at least partially implements a user specification or reacts to user intervention. Furthermore, the control unit prevents, or at least subsequently ensures, that the maximum total irradiance is less than or at most equal to the specified upper limit. In one embodiment, the lighting device is designed such that the control unit strives to prevent the maximum total irradiance from exceeding the upper limit throughout the entire operation of the lighting device.

[0091] In another embodiment, the lighting device can be operated in two different modes: with the limiting mode activated and the limiting mode deactivated. When the limiting mode is activated, the control unit operates as just described, i.e., in response to a user specification, it predicts a maximum total irradiance and ensures that the actually achieved maximum total irradiance is less than or equal to the upper limit. Optionally, when the limiting mode is activated, the control unit reacts as just described to the detection of an irradiance-relevant event. When the limiting mode is deactivated, the control unit allows the maximum total irradiance to be greater than the upper limit.In one embodiment, the control unit predicts a maximum total irradiance even when the limit mode is deactivated, but does not control a lighting unit with the goal of ensuring that the upper limit is not exceeded. If the maximum total irradiance is greater than the upper limit and the limit mode is deactivated, the control unit preferably issues a corresponding message in a human-perceivable form.

[0092] The lighting device is preferably capable of detecting a user input that determines whether the lighting device should be operated with the limit mode activated or deactivated. It is possible for a user to activate the limit mode in response to the message that the upper limit has been exceeded. In response, the control unit controls at least one lighting unit with the aim of reducing its maximum irradiance.

[0093] In one application, the lighting device according to the invention is used to illuminate a medical operating table. This operating table is designed to accommodate a patient who is to be treated medically. The lighting device can be used, in particular, inside a building or a vehicle.

[0094] The invention is described below using an exemplary embodiment.

[0095] Figure 1 shows schematically in a cross-sectional view a

[0096] Lighting device with three lighting units and a camera;

[0097] Figure 2 shows an example of three light fields generated by three

[0098] lighting units of Figure 1, with two light fields overlapping;

[0099] Figure 3 shows schematically a first example of the light fields of two

[0100] Lighting units and the resulting overall light field;

[0101] Figure 4 shows schematically a second example of the light fields of two

[0102] Lighting units and the resulting overall light field;

[0103] Figure 5 shows schematically in a cross-sectional view a

[0104] Lighting device with three lighting units and two cameras illuminating an uneven surface;

[0105] Figure 6 schematically shows a lighting unit of the arrangement of

[0106] Figure 5 and the illuminated surface;

[0107] Figure 7 schematically shows three images, each of which shows a camera of the

[0108] Arrangement of Figure 6. In the exemplary embodiment, the invention is used to illuminate an object Obj in the form of an operating table. A patient (not shown) who is being medically treated lies on this operating table Obj. The lighting device 100 according to the invention illuminates that surface Ob of the operating table Obj or of the patient on the operating table Obj which faces the lighting device 100. The lighting device 100 generates a light field on the illuminated surface Ob. In the following figures, a flat surface Ob is shown for the sake of simplicity. Of course, the illuminated surface of a patient on the operating table Obj is not flat. Note: The figures are not necessarily to scale.

[0109] The lighting device 100 of the exemplary embodiment comprises three lighting units 1, 2, 3, which illuminate the operating table Obj vertically or obliquely from above and from up to three different directions. Figures 1 and 5 schematically show two different embodiments of the lighting device 100. Unless expressly stated otherwise, the following description refers to both embodiments.

[0110] The lighting units 1, 2, 3 are preferably movably attached to a ceiling and can be moved independently of one another. The respective position and orientation of each lighting unit 1, 2, 3 in the room can be changed, preferably independently of the position and orientation of the or any other lighting unit. In one embodiment, the joints of each lighting unit 1, 2, 3 are designed such that the lighting unit 1, 2, 3 does not change its position and orientation relative to the illuminated surface on its own, but only after user intervention. In another embodiment, each lighting unit 1, 2, 3 can be locked in a desired position and orientation and unlocked again.

[0111] The lighting units 1, 2, 3 each have an optical central axis. In the exemplary embodiment, the optical central axis of the lighting unit 1 is the same as the geometric central axis MA.1, and the optical central axis of the lighting unit 2 is the same as the geometric central axis MA.2. In the exemplary embodiment, the first lighting unit 1 is rotationally symmetrical to a central axis MA.1, and the second lighting unit 2 is rotationally symmetrical to a central axis MA.2. The third lighting unit 3 is only shown schematically. Of course, other configurations are also possible, in particular a different number of lighting units. The lighting units 1, 2, 3 are not necessarily rotationally symmetrical. In the orientation in which the two lighting units 1 and 2 are shown in Figure 1 and Figure 5, the two central axes MA.1 and MA.2 enclose an angle between them that is preferably between 25° and 70°.The two central axes MA.1 and MA.2 are inclined on the illuminated surface Ob and lie in the drawing planes of Figure 1 and Figure 5. In the situation shown, the central axis MA.3 of the lighting unit 3 is perpendicular to the illuminated surface Ob.

[0112] The illuminance and irradiance of a lighting unit 1, 2 are maximum along the optical center axis MA.1, MA.2. More precisely: in a plane that is perpendicular to the optical center axis MA.1, MA.2, the illuminance and irradiance assume their maximum values ​​at the intersection point of the plane with the optical center axis MA.1, MA.2. The same applies to the third lighting unit 3. The maximum illuminance and the maximum irradiance in the space of the lighting unit 1, 2, 3 also lie on the optical center axis MA.1, MA.2. The intersection points S.1 and S.2 of the two optical center axes MA.1 and MA.2 with the illuminated surface Ob are shown in Figure 1 and Figure 5.

[0113] Figure 2 schematically illustrates the three light fields Lfi, Lf2, Lfs which the lighting units 1, 2, 3 generate in a possible situation on the illuminated surface Ob. The illuminated surface Ob lies in the plane of the drawing in Figure 2, and the two central axes MA.1 and MA.2 are oblique to this plane of the drawing. The two ellipses are shown on which the illuminance and thus the irradiance is 10% of the respective maximum illuminance and thus the irradiance on the surface Ob. In the interior of these ellipses the illuminance and the irradiance are greater, outside they are less than 10% of the respective maximum. The interiors of these two ellipses are dotted differently for illustration. The central axis MA.In the situation shown, the third illumination unit 3 is perpendicular to the illuminated surface Ob, so that the area where the irradiance is 10% of the maximum irradiance is a circle. In the situation shown, this circle does not overlap with the two ellipses of the two illumination units 1 and 2. For example, the two illumination units 1 and 2 illuminate the patient's chest area, while illumination unit 3 illuminates a leg. In another possible situation not shown, two light fields overlap almost concentrically.

[0114] The orientations of the three illumination units 1, 2, 3 relative to the illuminated surface Ob result in the illuminated surface Ob, and thus a patient on the operating table Obj, being illuminated from three different directions. Therefore, the patient is generally still illuminated even if an object, for example, a doctor's body part or an object, enters the area between the illumination device 100 and the illuminated surface Ob.

[0115] The first lighting unit 1 comprises a carrier 5.1 and a plurality of individual light sources 1.1, 1.2, ... , which are fastened to the carrier 5.1 and are preferably arranged rotationally symmetrically about the central axis MA.1, see Figure 1 and Figure 5. The second lighting unit 2 comprises a carrier 5.2 and a plurality of individual light sources 2.1, 2.2, ... , which are fastened to the carrier 5.2 and are preferably arranged rotationally symmetrically about the central axis MA.2. Figure 1 and Figure 5 schematically show the light beams Lbu, Lbi.2, ... of the light sources 1.1, 1.2, ... as well as the light beams Lb2.i, Lf2.2, ... of the light sources 2.1, 2.2, ... For illustrative purposes, these light beams are dotted differently. The light sources can emit light of the same color temperature or light in at least two different color temperatures. Each light beam Lbi.i, Lbi.2, Lb2.i, Lf2.2, ... creates a single light field on the illuminated surface Ob.The individual light fields of the light sources of a lighting unit 1, 2, 3 overlap on the illuminated surface Ob, forming a respective light field Lfi, Lf2, Lfs. The individual irradiances for a point on the illuminated surface Ob are therefore added together. The lighting device 100 achieves a total light field Lf on the surface Ob. ges .

[0116] The generated total light field Lf gesis shown using two examples in Figure 3 and Figure 4. The lighting units 1 and 2 are switched on, and the lighting unit 3 is switched off. The illuminated surface Ob is perpendicular to the planes of the drawing in Figure 3 A, Figure 3 B, and the lower illustration of Figure 4 B, and the optical central axes MA.1 and MA.2 lie in these planes. Conversely, the illuminated surface lies in the plane of the drawing in Figure 4 A. Figure 3 A schematically shows the two lighting units 1 and 2, as well as the two central axes MA.1 and MA.2. In Figure 3 A and Figure 4 B, the respective irradiance Ee on the surface Ob is plotted on the y-axis. Shown is a section through the two light fields Lfi and Lf2 of the two lighting units 1 and 2, as well as a section through the total light field Lf. gesFor simplicity, the two light fields Lfi and Lf2 are shown as rotationally symmetrical to the respective central axes MA.1 and MA.2, and the influence of the inclined central axes MA.1, MA.2 is neglected. Figure 4 shows another example in which the two light fields Lfi and Lf2 overlap only slightly.

[0117] The lighting device 100 further comprises an operating unit 9, shown only schematically, and a signal-processing control unit 10, likewise shown only schematically. The operating unit 9 is capable of receiving a user input and forwarding it to the control unit 10. The control unit 10 thereby detects this user input. Preferably, a user can use the operating unit 9 to specify setting values ​​for different parameters of a lighting unit 1, 2, 3 or of the entire lighting device 100. In particular, a user can specify a desired maximum illuminance in the room for each lighting unit 1, 2, 3, for example on a continuous or graduated scale from 0 to 10, wherein the value 10 corresponds to the maximum achievable illuminance in the room. The value 5 results in the actually maximum achievable illuminance in the room being equal to half the maximum achievable illuminance.Or the user can specify that the value should be increased or decreased. A minus button and a plus button are shown as examples. Furthermore, the user can enter a default value for each lighting unit 1, 2, and 3, which specifies a desired light field diameter. x and optionally also a medium light spectrum of the lighting unit 1, 2, 3. The desired light field diameter d x refers to a reference distance of, for example, 1 m. In one embodiment, the user can also specify whether or not this lighting unit 1, 2, 3 should be included in an automatically implemented limitation of the total irradiance. Furthermore, the user can select or deselect a lighting unit 1, 2, 3 using the control unit 9, which is described further below.

[0118] The user can also set the following parameters for the lighting device 100:

[0119] - an upper limit for the maximum total irradiance achieved by the illumination device 100 on the illuminated surface Ob, and

[0120] - whether the limitation mode should be enabled or disabled.

[0121] The meanings are explained below.

[0122] The control unit 10 receives the specifications from the user and controls the light sources of the lighting unit 1, 2, 3 according to the specifications. For example, the control unit 10 sets the strength of the current flowing through a light source 1.1, 1.2, ..., 2.1, 2.2, ..., or the electrical voltage applied to the light source 1.1, 1.2, ..., 2.1, 2.2, ..., to a corresponding value. The light sources 1.1, 1.2, ..., 2.1, 2.2, ... are preferably operated in a pulsed manner, with the pulse frequency being high enough that an observer perceives constant illumination. By modulating the pulse width, the control unit 10 can also change the illuminance of a light source 1.1, 1.2, ..., 2.1, 2.2, ... In pulse width modulation, the control unit changes the relationship between the duration of a pulse in which the light source is supplied with power and the duration of a period of time between two consecutive pulses.In one embodiment, the control unit 10 is capable of changing the respective illuminance of a light source independently of the illuminances of the other light sources.

[0123] In the exemplary embodiment, the control unit 10 has read access to a computer-analyzable table in which a maximum illuminance achieved by the lighting unit 1, 2, 3 in the room is stored for several possible default values ​​that the user can specify. For example, it is stored that the default value 10 on a scale of 1 to 10 leads to a desired maximum illuminance of 160 kLux in the room, which is equal to the maximum achievable illuminance, and the default value 5 leads to half the maximum achievable illuminance, i.e. 80 kLux. This table is created and saved during a previous calibration of the lighting unit 1, 2, 3. The table is preferably valid for every similar lighting unit 1, 2, 3 and is saved in a data memory of the lighting unit 1, 2, 3.If the lighting device 100 comprises differently constructed lighting units 1, 2, 3, different tables are preferably also stored. Preferably, the table for a lighting unit 1, 2, 3 also contains the setting values ​​for the light sources of the lighting unit 1, 2, 3 that lead to the desired maximum illuminance in the room. The tables are created and stored in advance. The control unit 10 has read access to these tables.

[0124] The control unit 10 “knows” and uses for each lighting unit 1, 2, 3 the respective value for each of the following parameters, whereby this value does not depend on the position and orientation of the lighting unit 1, 2, 3 relative to the surface Ob:

[0125] - the maximum achieved illuminance and / or irradiance in the room,

[0126] - the functional dependence of the maximum illuminance and / or irradiance on the surface Whether on the distance along the optical central axis,

[0127] - optionally the light spectrum,

[0128] - the light field diameter d x at a reference distance and

[0129] - whether the lighting unit 1, 2, 3 should be included in a limitation of the total irradiance or not.

[0130] The maximum irradiance achieved in the room of the lighting unit 1 , 2 , 3 is given by Ee m ax ,i,sp, Eemax, 2, sp, Eemax,3,sp.

[0131] In one embodiment, a user enters a setting value for the maximum achieved irradiance Ee max,i ,sp, Eemax, 2, sp, Eemax,3,sp in the room of each lighting unit 1, 2, 3. The control unit 10 can control each lighting unit 1, 2, 3 according to this setting value. For example, setting value 10 results in the maximum achievable illuminance in the room, while setting value 5 results in half of this. In one embodiment, a proportionality factor between the maximum irradiance and the maximum illuminance is stored, for example, 4 W / m A 2 / kLux. The setting value 10 then leads to a maximum irradiance of 640 W / m A2. In a further development, a table is stored which provides the resulting proportionality factor between the maximum irradiance and the maximum illuminance in the room for several possible light spectra of a lighting unit 1, 2, 3. The control unit 10 derives the maximum achieved or maximum expected irradiance in the room of the lighting unit 1, 2, 3 for each lighting unit 1, 2, 3 from the respective setting value, the maximum achievable illuminance in the room and the proportionality factor. In the following, the abbreviation "maximum total irradiance" Ee m ax,ges is used for the effected or predicted maximum irradiance of the lighting device 100 on the illuminated surface Ob.

[0132] The control unit 10 automatically determines in an application which maximum total irradiance Ee max,ges the illumination device 100 achieves on the illuminated surface Ob. More precisely: It determines an estimated value Ee m ax,ges,est for the maximum irradiance Ee m ax,ges. It is possible for the control unit 10 to perform this determination with a constant sampling frequency. In a preferred implementation, the control unit 10 determines the maximum total irradiance Ee m ax,ges is repeated whenever an irradiance-relevant event has been detected. An irradiance-relevant event changes the maximum total irradiance Ee m ax,ges or is at least capable of changing them. Examples of irradiance-relevant events are:

[0133] - The distance between a lighting unit 1 , 2, 3 and the surface has been changed, in particular reduced.

[0134] - A user has touched a support of a lighting unit 1 , 2, 3: This touch is usually carried out with the aim of changing the position and / or orientation of this lighting unit 1 , 2, 3 relative to the surface.

[0135] Preferably, the lighting device 100 comprises sensors capable of detecting an irradiance-relevant event. A signal from such a sensor is transmitted to the control unit 10. In another application, the control unit 10 automatically predicts the maximum total irradiance Ee m ax,ges of the lighting device 100 is to be expected in response to a user specification - more precisely: will occur or would occur if the user specification is or would be implemented unchanged.

[0136] In order to at least approximately determine the maximum total irradiance

[0137] Ee max,ges , which the lighting device 100 actually achieves on the illuminated surface Ob, the control unit 10 in the exemplary embodiment uses the current controls of the lighting units 1, 2, 3 as well as other sensor values. In order to at least approximately predict the maximum total irradiance Ee m ax,ges the lighting device 100 would achieve if a user specification were implemented unchanged, the control unit 10 uses this user specification as well as the actual controls of the lighting units 1, 2, 3. So, for example, if the user specifies that the maximum irradiance Ee ma x,i,s P in the room of the lighting unit 1 is to be increased to the maximum value, the control unit 10 uses this maximum value for the maximum irradiance Ee for the prediction m ax,i,s P, however, the actual current light field diameter and the current correlated color temperature of the lighting unit 1 as well as the respective currently achieved maximum irradiance, maximum light field diameter and correlated color temperature of the other two lighting units 2 and 3. Note: a user setting by which the light field diameter or the correlated color temperature of a lighting unit 1, 2, 3 is to be changed can also lead to the maximum total irradiance Ee m ax,ges is increased.

[0138] In a data memory of the lighting device 100, a maximum permissible upper limit for the maximum total irradiance Ee m ax,ges. This maximum permissible upper limit is, for example, 700 W / m A 2 or 1000 W / m A2. These values ​​are derived from the above-mentioned standard for a single medical lighting unit. Note: The above-mentioned standard specifies an upper limit for a single lighting unit, but not an upper limit for a lighting device with multiple lighting units.

[0139] A user can specify a lower value for this upper bound, but not a higher value. The upper bound used, i.e., the factory-set or user-specified upper bound, is denoted by Ee m ax,req. The control unit 10 compares the determined or predicted maximum total irradiance Ee max,ges with the upper limit Eemax,re In one possible application, the lighting device 100 is always operated in a limiting mode. The control unit 10 automatically ensures that the actually achieved maximum total irradiance Eemax,ges is always less than or equal to the upper limit Ee m ax,req. If a user default would cause the upper bound Ee m ax,req would be exceeded, the control unit 10 causes the upper limit Ee m ax,req is not exceeded. This is explained below using the example that the user specification specifies the following: The maximum irradiance Ee max,i,sp in the space of lighting unit 1 should be increased, for example to the maximum value. If this user specification were implemented and all other settings of lighting units 1, 2, 3 were to remain unchanged, then in this example the upper bound Ee m ax,req may be exceeded. In one implementation, the control unit 10 increases the maximum irradiance Ee in response to this prediction max ,i,sp of the lighting unit 1 is not as strong as desired by the user, in extreme cases not at all. In another, preferred embodiment, the control unit 1 increases the maximum irradiance Ee max ,i,sp in the room of the lighting unit 1 as specified by the user, but reduces the maximum irradiance Ee ma x,2,s P , Ee ma x,3,s Panother lighting unit 2 or 3 and thereby ensures that the upper limit Eemäx.req is not exceeded.

[0140] In another possible application, this limitation mode is optionally activated or deactivated, for example by the user using the control unit 9 or automatically by the control unit 10. When the limitation mode is deactivated, the control unit 10 does not prevent the maximum total irradiance Ee ma x, g the upper bound Ee ma x,req. Preferably, the control unit 10 generates an alarm when the predicted or determined maximum total irradiance Ee ma x,ges above the upper bound Ee m ax,req. This alarm is issued in a human-perceivable form.

[0141] It has already been mentioned that a user can select at least one lighting unit 1, 2, 3 of the lighting device 100. Schematically, Figures 1 and 5 show three buttons labeled 1, 2, 3 on the operator unit 9. The control unit 10 does not take into account the or each selected lighting unit 1, 2, 3 when determining or predicting the maximum total irradiance Ee. m ax, g of the lighting device 100. Alternatively, the control unit 10 takes into account only the or each selected lighting unit 1, 2, 3.

[0142] An application is explained using the example of the case where the user has selected illumination unit 3. Illumination units 1 and 2 are directed, for example, onto the patient's chest or face, and the light fields Lfi and Lf2 overlap there. Illumination unit 3 illuminates one of the patient's legs, and the light field Lfs of illumination unit 3 does not overlap with the light fields Lfi and Lf2. In this application, the maximum irradiance that illumination units 1 and 2 together generate on the patient's chest or face should be less than or equal to the upper limit Ee. m ax,req. The illumination unit 3 does not illuminate the chest or face, but rather a less sensitive area of ​​the patient, and is not included in the limitation of the maximum total irradiance.

[0143] In the embodiments described below, all three lighting units 1, 2, 3 are included in the prediction or determination of the total irradiance, ie the user has not selected or deselected any lighting unit.

[0144] The maximum total irradiance Ee m ax,ges depends in particular on the following parameters:

[0145] - the respective maximum illuminance achieved by the lighting units 1, 2, 3 on the surface Ob, and how the light fields Lfi, Lf2, Lfs achieved by the lighting units 1, 2, 3 on the surface Ob are positioned relative to each other.

[0146] The maximum irradiance achieved on the surface Ob is given by Ee max,i, Eemax.2, Eemax.3 and is less than or equal to the maximum irradiance achieved in the room of the lighting unit 1, 2, 3. In the embodiment, the assumption is used that the maximum irradiance Ee m ax,i, Ee m ax,2, Ee m ax,3 occurs on the respective optical central axis MA.1 , MA.2, MA.3.

[0147] Figure 2, Figure 3 and Figure 4 show several examples of how the two light fields Lfi, Lf2 of the two illumination units 1, 2 are positioned relative to each other. The respective maximum irradiance Ee is shown. m ax,i and Eemax.2, the resulting total light field Lf ges and the maximum total irradiance Ee m ax,ges, i.e. the maximum irradiance of this total light field Lf ges on the illuminated surface Ob.

[0148] The control unit 10 determines an estimated value for the currently achieved or expected maximum total irradiance Ee m ax,ges. This estimate is expressed as Ee m ax,ges,est. To determine the estimated value, the control unit 10 uses the respective value of at least one, optionally each of the parameters described above, which does not depend on the positions and orientations of the lighting units 1, 2, 3 relative to the illuminated surface Ob, in particular design-related and therefore predetermined parameters as well as controls of the lighting units 1, 2, 3. The control unit 10 compares this estimated value Ee m ax,ges,est with the upper bound Ee m ax,req.

[0149] In various embodiments of the invention, the control unit 10 further determines the respective value of none, one or more of the following parameters, which depend on the current positions and orientations of the lighting units 1, 2, 3 relative to the illuminated surface Ob, and uses the or at least one, preferably each determined parameter value to determine the estimated value Ee m ax,ges,est to determine: - the respective distance between each lighting device 1 , 2, 3 and the surface Ob, measured along the respective optical center axis MA.1 , MA.2, MA.3,

[0150] - the respective distance between two intersection points of two optical central axes MA.x, MA.y (y#x) with the surface Ob,

[0151] - the respective light field diameter d x , which each lighting unit 1 , 2, 3 achieves on the illuminated surface Ob,

[0152] - another property of the respective light field Lfi, Lf2, Lfs of each lighting unit 1, 2, 3,

[0153] - whether at least two light fields on the illuminated surface overlap or not, and

[0154] - the angle between the optical center axis of the lighting unit 1, 2, 3 and the plane into which the surface Ob extends.

[0155] Below, an embodiment is described in which the control unit 10 does not determine and use a value for any of the above-mentioned parameters that depend on position and / or orientation. Instead, two simplifying assumptions are made. Due to these two simplifying assumptions, the determined estimated value Ee m ax,ges,est always greater than or equal to the actual maximum total irradiance Ee m ax,ges, but not smaller. "So you're on the safe side."

[0156] One simplification is that the respective maximum illuminance and thus irradiance in the space of each lighting unit 1, 2, 3 occurs on the illuminated surface Ob. According to the other simplification, all optical center axes MA.1, MA.2, MA.3 intersect the surface Ob at the same point. One consequence: The three generated light fields Lfi, Lf2, Lfs are positioned concentrically to each other. On a flat surface Ob, the three generated light fields Lfi, Lf2, Lfs are concentric ellipses, specifically circles.

[0157] These two simplifications avoid in particular the need to measure or otherwise determine the distances between a lighting unit 1, 2, 3 and the surface Ob and the relative positioning of the light fields Lfi, Lf2, Lfs to each other, and result in the control unit 10 estimating the value Ee m ax,ges,est is determined as the sum of the maximum irradiances in the room, i.e.

[0158] (1 ) Eemax,total,est = Eemax,1 ,sp + Eemax,2,sp + Eemax,3,sp-

[0159] The embodiments according to Figure 3 and Figure 4 are two examples of how the assumption described above can lead to the control device 10 setting too low an illuminance and thus irradiance on at least one lighting unit 1, 2, 3, i.e. the illuminance of a lighting unit 1, 2, 3 and the resulting maximum total irradiance Ee m ax,ges are smaller than the upper limit Eemax.req. It is therefore possible that the illuminance / irradiance of at least one lighting unit 1, 2, 3 is smaller than desired by the user. Several embodiments are described below that avoid the need for the simplifications just described.

[0160] In one embodiment, a user additionally specifies which lighting units 1, 2, 3 generate or potentially generate overlapping light fields. The simplification just described is preferably used for those lighting units that generate light fields that overlap according to the specification. The maximum irradiance generated by these lighting units with overlapping light fields is generated according to the simplifications just described. The maximum total irradiance Ee m ax,ges,est, this maximum irradiance in the room or the maximum irradiance of another lighting unit in the room is used, whichever is greater.

[0161] An example applies to the situation shown in Figure 2 and Figure 3. According to this example, the light fields Lfi, Lf2 of the two lighting units 1 and 2 overlap, and the light field Lfs of the lighting unit 3 does not overlap. Then, the estimated value for the maximum total irradiance Ee m ax,ges,est determined or predicted as follows: (2) Eömax.ges.est — max [E6max,1 ,sp + E6max,2,sp, E6max,3,sp]-

[0162] Even with this estimate, “you are still on the safe side.”

[0163] The embodiment described below eliminates the need for a user to specify which light fields overlap or can overlap. This preferred embodiment is described below. The assumption just described can also be used in this embodiment, for example, the maximum total irradiance Ee max,ges,est can be determined or predicted according to formula (2).

[0164] A first camera 4.1 is attached to the support 5.1, see Figures 1 and 5. The area of ​​the illuminated surface Ob that is illuminated by at least one lighting unit 1, 2 lies in the field of view Bf.1 of the first camera 4.1. In the embodiment according to Figure 5, a second camera 4.2 is additionally attached to the support 5.2. The illuminated area also lies in the field of view Bf.2 of the second camera 4.2. It is also possible for a camera to be attached to a separate support.

[0165] The first camera 4.1 and the optional second camera 4.2 each generate an image of the illuminated surface Ob. This image looks similar to that shown in Figure 2 and Figure 4.

[0166] The images from camera 4.1 or from both cameras 4.1 and 4.2 show the light fields Lfi, Lf2, and Lfs. However, an image from a camera 4.1 or 4.2 does not yet reveal which light field originates from which illumination unit.

[0167] The control unit 10 is able to determine which light field originates from which lighting unit from the images of camera 4.1 and optionally from the two cameras 4.1 and 4.2, as well as the signals from these three sensors. Preferably, the control unit 10 also uses the respective light field diameter d. x which is set on the lighting unit 1 , 2, 3

[0168] A first implementation is described below, in which the control unit 10 detects, permanently or at least at regular intervals, which light field Lfi, Lf2, Lfs originates from which lighting unit 1, 2, 3. During a measurement period in which this detection is performed, the three lighting units 1, 2, 3—more generally, those lighting units that are currently in use—are operated in a pulsed manner, as follows:

[0169] - In a first alternative of the first implementation, at any given time, only one lighting unit 1, 2, 3 is switched on, and all other lighting units are switched off. During the time period, each lighting unit 1, 2, 3 is switched on at least once, preferably several times.

[0170] - In a second alternative, at any given time, exactly one lighting unit 1, 2, 3 is switched off, and all other lighting units are switched on. During the time period, each lighting unit 1, 2, 3 is switched off at least once, preferably several times. The second implementation often results in a higher irradiance than the first implementation.

[0171] Preferably, the measurement period is so short that the respective position and orientation of each lighting unit relative to the surface does not change significantly during the measurement period. In both alternatives, the pulse frequency is preferably high enough that an observer perceives the three lighting units 1, 2, and 3 as permanently switched on and illuminated, i.e., no flickering is perceived.

[0172] The first camera 4.1 and, in one embodiment, the optional second camera 4.2 each record a sequence of images. The following boundary condition is met: At least one image of the sequence shows only the first light field Lfi , at least one image only the second light field Lf2 , and at least one image only the third light field Lfs . The control unit 10 evaluates these images, preferably superimposing the images mathematically. Through the evaluation, the control unit 10 derives at least one of the following pieces of information: - the respective light field diameter d actually achieved on the surface Ob x each lighting unit 1, 2, 3 - this can be determined from the light field diameter d x deviate from the reference distance,

[0173] - whether and if so how much the light fields Lfi, Lf2, Lfs overlap,

[0174] - the distances between the points of maximum illuminance and / or centers of the light fields Lfi, Lf2, Lfs on the surface Ob from each other,

[0175] - how the respective areas of maximum irradiance of the lighting units 1, 2, 3 on the surface Ob are positioned relative to each other.

[0176] To determine which light field Lfi, Lf2, Lfs originates from which lighting unit 1, 2, 3, the control unit 10 determines, in the first alternative, which light field is shown in an image when the lighting unit x (x=1, 2, 3) is switched on and every other lighting unit y (y#x) is switched off. Similarly, in the second alternative, the control unit 10 determines which light field is not shown. Using image processing, the control unit 10 determines which lighting units 1, 2, 3 are generating light fields that currently overlap.

[0177] In a second implementation, at least one, preferably each, lighting unit 1, 2, 3 comprises a sensor that measures the current position and orientation of the lighting unit 1, 2, 3 in space. The control unit 10 uses signals from these sensors to determine which light field originates from which lighting unit 1, 2, 3.

[0178] The two implementations can be combined. The first implementation, with both alternatives, has the advantage that no sensor is required to measure the position or orientation of a lighting unit 1, 2, 3 in the room.

[0179] In the configurations just described, the respective maximum irradiance Ee max ,i,sp, Eemax,2,sp, Eemax,3,sp of a lighting unit 1 , 2, 3 in the room as the maximum irradiance Ee max,i, Eemax,2, Eemax,3 of this illumination unit 1 , 2, 3 on the surface Ob. This design sometimes leads to a maximum total irradiance Ee m ax,ges, which is well below the upper bound Ee m ax,req. Therefore, the respective distance disti, dist2, dists between a lighting unit 1, 2, 3 and the illuminated surface Ob is preferably measured and used.

[0180] In a preferred embodiment, it is justified to assume that the maximum irradiance Ee m ax,i, Ee m ax,2, Ee max,3, which a lighting unit 1, 2, 3 achieves on the illuminated surface Ob, occurs at the respective intersection point between the optical center axis MA.1, MA.2, MA.3 of this lighting unit 1, 2, 3 and the surface Ob, regardless of the angle between this optical center axis MA.1, MA.2, MA.3 and the operating table Obj and thus the surface Ob. In the examples shown in Figure 2 to Figure 4, this is the case: The maximum irradiance Ee m ax,i, Ee m ax,2 occurs at the intersection point S.1 or S.2. This assumption is particularly justified if 2*dso > d.

[0181] Under this assumption, it is sufficient to measure the distance disti, dist2 along the optical center axis between the lighting unit 1, 2, 3 and the illuminated surface Ob. The control unit 10 has read access to a computer-analyzable table for each lighting unit 1, 2, 3. In this table, for different distances, a proportionality factor is specified between the maximum irradiance Ee m ax,i,s P , Eemax,2,sp, Eemax,3,sp in the room and the maximum irradiance Ee m ax,i, Ee m ax,2, Ee m ax,3 is stored on the surface Ob. Preferably, this proportionality factor applies to each lighting unit 1, 2, 3. It is, of course, possible that a proportionality factor is stored for each lighting unit 1, 2, 3 and for different distances.

[0182] In one embodiment, the control unit 10 determines and uses the respective distance disti, dist2, dists between a lighting unit 1, 2, 3, but uses the simplifying assumption that the light fields Lfi, Lf2, Lfs are arranged concentrically to each other. The control unit 10 determines the respective maximum irradiance on the surface Ob and derives the estimated value Ee m ax,ges,est for the maximum total irradiance Ee m ax,ges, for example, according to the following calculation rule:

[0183] (3) Eemax,total,est — Eemax,1 + E6max,2 + E6max,3-

[0184] The following calculation rule is also possible if it has been specified or determined that the light field Lfs of the lighting unit 3 does not overlap with the other two light fields Lfi, Lf2:

[0185] (4) Eemax,total,est = max [Eemax,1 + Eemax,2, Eemax.s]-

[0186] It is possible for an object to enter the area between a lighting unit 1, 2, 3 and the illuminated surface Ob, for example an instrument or a body part of a treating physician. If the optical central axis MA.1, MA.2, MA.3 then passes through this object, the control unit 10 automatically detects this event. This is because the distance measured along the central axis MA.1, MA.2, MA.3 suddenly decreases. The control unit 10 preferentially uses the value measured before this sudden reduction as the distance between the lighting unit 1, 2, 3 and the surface Ob.

[0187] Various configurations are described below to measure the distance along the optical center axis MA.1, MA.2, MA.3.

[0188] In one embodiment, at least one distance sensor is attached to at least one support 5.1, 5.2, 5.3. This distance sensor measures the distance between itself and the reflective illuminated surface Ob. The example in Figure 1 shows such a distance sensor 6.2, which is attached to the support 5.2 of the second lighting unit 2 and measures the distance dist2 between itself and the illuminated surface Ob along the central axis MA.2. Preferably, at least one distance sensor is attached to each support 5.1, 5.2, 5.3. It is possible that a lateral distance occurs between the distance sensor and the central axis MA.1, MA.2, MA.3. This distance as well as an angle between the central axis MA.1, MA.2, MA.3 and the axis in which the distance sensor measures the distance are known from the design of the lighting unit 1, 2, 3.Preferably, the control unit 10 is able to correct a measurement result of the distance sensor using the distance and the angle in order to determine the distance along the central axis.

[0189] In one implementation, the first camera 4.1 and / or the optional second camera 4.2 each have an autofocus function, so that the camera 4.1, 4.2 focuses on the illuminated surface Ob. In one implementation, the control unit 10 uses the setting of this autofocus to determine the respective distance. It is possible for the control unit 10 to receive multiple measured values ​​for the distance from multiple sensors and aggregate these measured values ​​into a single distance.

[0190] As already explained, the control unit 10 detects the respective light field diameter d x , for example dio, each lighting unit 1 , 2, 3. This light field diameter d xis related to a predetermined reference distance of, for example, 1 m. Preferably, the control unit 10 "knows" the respective image scale of the or each camera 4.1, 4.2 used. The light field diameter d xand the image scale determine how large the image of the light field Lfi, Lf2, Lfs of a lighting unit 1, 2, 3 is when the plane of the light field Lfi, Lf2, Lfs is perpendicular to the optical center axis MA.1, MA.2, MA.3 and is at a reference distance from the lighting unit 1, 2, 3. From this size and the actual size in an image from the camera 4.1, 4.2, in one embodiment the control unit 10 derives an estimated value for the distance disti, dist2 dists between the lighting unit 1, 2, 3 and the surface Ob measured along the center axis MA.1, MA.2, MA.3. It is also possible for the control unit 10 to measure how large an image of a light field is in the image of a camera 4.1, 4.2. From the size of the image and the light field diameter d xAt the reference distance, the control unit 10 derives the desired distance between the camera 4.1, 4.2 and thus the lighting unit 1, 2 on the one hand, and the light field Lfi, Lf2, Lfs and thus the illuminated surface Ob on the other hand. Optionally, the control unit 10 uses the image scale of the camera 4.1, 4.2, which is variable in one implementation of the camera 4.1, 4.2. It is possible for at least one lighting unit 1, 2, 3 to comprise its own camera and / or another distance sensor, and for at least one other lighting unit to comprise neither its own camera nor another distance sensor. In some cases, however, the respective distance can still be measured at least approximately. This implementation is described below as an example for the situation shown in Figure 1, in which only the second lighting unit 2 has a distance sensor 6.2 and therefore only the distance dist2 between the second illumination unit 2 and the illuminated surface Ob can be measured directly.

[0191] In the situation shown in Figure 1, the control unit 10 uses, in one implementation, images from the camera 4.1 with the field of view Bf.1 to determine the respective size and position of each light field Lfi, Lf2, Lfs on the illuminated surface Ob. The control unit 10 also "knows" the respective geometry and the respective light field diameter d xeach lighting unit 1, 2, 3. Furthermore, the control unit 10 “knows” the diameter of the circular area occupied by the light sources 1.1, 1.2, ..., 2.1, 2.2, ... on the carrier 5.1, 5.2, 5.3 in total, i.e. the diameter of the respective light beam generated on the carrier 5.1, 5.2, 5.3. For each lighting unit 1, 2, 3, the control unit 10 determines the respective ratio between the diameter of the light field on the lighting unit 1, 2, 3 and the diameter of the light field Lfi, Lf2, Lfs generated by the lighting unit 1, 2, 3 on the illuminated surface Ob. From these ratios and from the measured distance dist2, the control unit 10 approximately determines the other distances.

[0192] The following simplified assumption is also possible for a lighting unit 1 , 2, 3 without a distance sensor: The actual distance disti, dist2, dists between this lighting unit 1 , 2, 3 is equal to the reference distance specified above, for example 1 m.

[0193] As already explained, the control unit 10 uses the respective distance between a lighting unit 1, 2, 3 and the illuminated surface Ob to determine the respective maximum irradiance Ee m ax,i, Eemax,2, Eemax,3 of this illumination unit 1, 2, 3 on the surface Ob. This distance is measured, for example, along the central axis MA.1, MA.2, MA.3.

[0194] In one embodiment, the simplifying assumption is used that the maximum illuminance Ee m ax,i, Ee m ax,2, Ee max,3, which a lighting unit 1 , 2, 3 generates on the surface Ob, occurs at the intersection point S.1 , S.2, S.3 between the optical central axis MA.1 , MA.2, MA.3 of this lighting unit 1 , 2, 3 and the illuminated surface Ob, regardless of the angle between the central axis MA.1 , MA.2, MA.3 and the surface Ob. The following embodiment avoids the need to make this simplifying assumption and takes into account the possibility that the central axis MA.1 , MA.2, MA.3 is not perpendicular but oblique to this plane and that therefore the maximum irradiance even in the case of a bell-shaped light field Lfi, Lf2, Lfs occurs outside the intersection point of the central axis with the plane. It can be assumed that the illuminated surface Ob extends in a plane.

[0195] An embodiment was described above in which a sensor measures the current orientation of the lighting unit 1, 2, 3 in space. In one embodiment, the control unit 10 derives the angle between the central axis MA.1, MA.2, MA.3 and the surface Ob from a signal from this sensor. An alternative embodiment eliminates the need to provide such a sensor. This alternative embodiment is described below with reference to Figures 5 to 7.

[0196] In this embodiment, at least one camera 4.1 is designed as a so-called 3D camera, preferably both cameras 4.1, 4.2. The camera 4.1, 4.2 has a field of view Bf.1 or Bf.2 and supplies for each pixel not only a brightness value as a gray level or color value, but also for each pixel or at least for a sufficiently large number of pixels the distance between the pixel and the illuminated surface Ob, measured in the direction of the optical center axis MA.1, MA.2 of the camera 4.1, 4.2. In the example shown, this optical center axis coincides with the center axis MA.1, MA.2 of the lighting unit 1, 2.

[0197] As a rule, the illuminated surface Ob does not have a flat contour. Five elevations 7.1, ..., 7.5 are shown as examples in Figures 5 to 7. The camera

[0198] 4.1, 4.2 scans the illuminated surface Ob without contact and thereby obtains a topographical profile of the surface Ob in the viewing direction MA.1, MA.2. Such a camera is known as a "time-of-flight sensor." Such a method is described, for example, in DE 10 2013 012 231 A1 and DE 10 2012 014 716 A1. Other designs for a sensor that generates a topographical profile are also possible, for example a suitable laser scanner, radar scanner, or lidar scanner. It is also possible for a sensor that generates a topographical profile to be spatially separated from the camera 4.1, 4.2.

[0199] Figure 5 illustrates how the two 3D cameras 4.1 and 4.2 each generate a topographical profile of the illuminated surface Ob with these five elevations 7.1, ..., 7.5 from two different viewing directions. Figure 6 shows how the second illumination unit 2 is positioned relative to the illuminated surface Ob. Figure 7 A shows how the five elevations 7.1, ..., 7.5 are shown in a topographical profile when the optical axis of the camera is perpendicular to the illuminated surface Ob, which is not the case for the two cameras 4.1 and 4.2. Figure 7 B shows how the five elevations

[0200] 7.1, ..., 7.5 are represented in a topographical profile of the camera 4.2 on the support 3.2 of the second illumination unit 2. Figure 7C shows how the five elevations 7.1, ..., 7.5 are represented in a topographical profile of the camera 4.1. As is known, the elevation 7.1, ..., 7.5 is represented larger the closer it is to the respective camera 4.1, 4.2.

[0201] The topographical profiles from the two cameras 4.1 and 4.2 show the same illuminated surface Ob from two different viewing directions. Optionally, a topographical profile is also available from a 3D camera (not shown), whose optical axis is perpendicular to the illuminated surface Ob.

[0202] The control unit 10 "knows" the position of the 3D camera 4.1, 4.2 relative to the optical center axis MA.1, MA.2. From this information, the control unit 10 automatically derives the position of the center axis MA.1, MA.2 relative to the respective topographical profile provided by the camera 4.1, 4.2. By evaluating the topographical profile and the position of the center axis MA.1, MA.2, the control unit 10 derives the distance between the lighting unit

[0203] 1.2 and the illuminated surface Ob, measured along the central axis MA.1, MA.2. By a mathematical comparison between these topographical profiles, the control unit 10 determines the distance between the two intersection points S.1 and S.2 of the two central axes MA.1, MA.2 with the illuminated surface Ob. From this and from the respective light field diameter d xof the lighting units 1, 2 at the reference distance, the control unit 10 derives how strongly the two light fields Lfi and Lf2 overlap, see Figure 2 to Figure 4.

[0204] In one embodiment, the control unit 10 further determines the respective angle between the central axis MA.1, MA.2 and the plane in which the illuminated surface Ob extends. For example, the control unit 10 computationally performs a coordinate transformation to align two topographical profiles. These two profiles show the same surface Ob. From the comparison, for example from the coordinate transformation, the control unit 10 derives the angle between the two optical central axes MA.1, MA.2 of the lighting units 1, 2.

[0205] The or at least one topographical profile which a 3D camera 4.1 ,

[0206] 4.2 measures, changes suddenly when another object comes into the field of view Bf.1, Bf.2 of a camera 4.1, 4.2. The control unit 10 automatically detects this event. To detect this event, the control unit 10 preferably uses the current topographical profile with the topographical profile that was last measured before this event was detected. This topographical profile of the illuminated surface often does not change as long as the object is in the field of view Bf.1, Bf.2 and no other object comes into the field of view Bf.1, Bf.2. Preferably, the detection of the event that another object has come into the field of view Bf.1, Bf.2 does not trigger the step of changing a maximum irradiance.

[0207] As already explained, when operating in limiting mode, the control unit 10 automatically ensures that the determined maximum total irradiance Ee max,ges is less than or equal to the specified limit Eemax.req. As already explained, in the exemplary embodiment, the user or a higher-level control unit (not shown) specifies a preset value for each lighting unit 1, 2, 3. From this preset value, the control unit 10 derives a maximum irradiance Ee to be achieved. m ax,i,s P , Ee m ax,2,s P in the room of this lighting unit 1, 2, 3. The control unit 10 derives from the maximum irradiance Ee m ax,i,s P , Ee m ax,2,s P in the room of a lighting unit 1 , 2, 3 the maximum irradiance Ee m ax,i, Ee m ax,2 of this lighting unit 1 , 2, 3 on the surface Ob and determines which maximum total irradiance Ee m ax,ges the illumination device 100 would achieve as a result of this specification on the illuminated surface Ob.

[0208] If the calculated estimate Ee m ax,ges,est for the expected maximum irradiance Ee m ax,ges is above the specified upper limit Eemax.req, the control unit 10 automatically reduces the illuminance and thus the irradiance of at least one lighting unit 1, 2, 3, in such a way that after the reduction the specified upper limit Ee max,req is maintained. In one implementation, the control unit 10 reduces the maximum illuminances to be achieved for all lighting units 1, 2, 3 by the same factor, for example by the factor Eemax,ges,est / Eemax.req. If the illuminances resulting from the default values ​​or the illuminances resulting from the automatic reduction result in the upper limit Eemax.req being maintained, the control unit 10 controls the light sources of the lighting units 1, 2, 3 such that the controlled lighting units 1, 2, 3 achieve the desired maximum illuminances.

[0209] It is possible for a user to increase a preset value for a lighting unit x (x=1, 2, 3) while the lighting device 100 is operating. The control unit 10 automatically checks whether the increased preset value still results in a maximum total irradiance Ee max,ges which is less than or equal to the given upper bound Ee m ax,req. If the increased default value for the illumination unit x results in an estimated maximum irradiance Ee m ax,ges,est above the given limit Ee m ax,req, the control unit 10, in one embodiment, automatically reduces the illuminance of another lighting unit y (y#x). This embodiment results in the illuminance of the lighting unit x actually being increased as desired by the user, thus, for example, brightening a specific area of ​​the patient. In particular, it is possible to illuminate the patient from a different direction than before. At the same time, this embodiment results in the upper limit Ee m ax,req continues to be met.

[0210] List of reference symbols

Claims

Lighting device (100) for illuminating a surface (Ob) of an object (Obj), wherein the lighting device (100) - at least two lighting units (1, 2, 3) and - a signal-processing control device (10), wherein each illumination unit (1, 2, 3) is designed to illuminate the surface (Ob) with a respective maximum irradiance (Ee m ax.i, Eemax.2), wherein the illumination device (100) is designed to illuminate the surface (Ob) with a maximum total irradiance (Ee m ax,ges), whereby the maximum total irradiance (Ee m ax,ges) of the maximum irradiances (Ee m ax.i, Eemax.2) of the lighting units (1, 2, 3), wherein the control device (10) is designed to - to control each lighting unit (1, 2, 3) independently of the or any other lighting unit and - thereby the maximum irradiance (Ee m ax.i, Eemax.2) of this lighting unit (1, 2, 3), wherein the lighting device (100) is designed to implement a user specification concerning the maximum total irradiance (Ee max ,ges) of the lighting device (100) or the maximum irradiance (Ee max .i, Eemax.2) of a lighting unit (1, 2, 3), wherein the control device (10) is further configured to automatically - to predict at least approximately the maximum total irradiance (Ee m ax,ges) the lighting device (100) on the surface (Ob) will achieve when the lighting device (100) is operated according to the user specification, - the predicted maximum total irradiance (Ee m ax,ges) with a given upper bound (Ee max,req) for the maximum irradiance on the surface (Ob) and - when the predicted maximum total irradiance (Ee max, ges) is greater than the upper limit (Ee max, re q) 'St, to control at least one lighting unit (1, 2, 3) depending on the recorded user specification in such a way that after the control the actually achieved maximum total irradiance (Ee m ax,ges) of the illumination device (100) on the surface (Ob) is less than or equal to the upper limit (Ee max, re q) 'St. Illumination device (100) according to claim 1, characterized in that each illumination unit (1, 2, 3) of the illumination device (100) is designed to generate a respective light field (Lfi, Lf2, Lfs) on the surface (Ob), and the control device (10) is designed to - to determine for each lighting unit (1, 2, 3) of the lighting device (100) which maximum irradiance (Ee m ax.i, Eemax.2) this lighting unit (1 , 2, 3) on the surface (Ob) actually achieves, - to determine how the light fields (Lfi, Lf2, Lfs) generated by the lighting units (1, 2, 3) on the illuminated surface (Ob) are positioned relative to each other, and - the maximum total irradiance (Ee m ax,ges) of the lighting device (100) using the recorded user specification, the determined maximum irradiances (Ee ma xi, Ee max.2) and the determined positions of the generated light fields (Lfi, Lf2, Lfs). Lighting device (100) according to claim 2, characterized in that the lighting device (100) comprises an image recording system with at least one camera (4.1, 4.2) and the control unit (10) is designed to control the lighting units (1, 2, 3) in a measuring period such that at any time in the measuring period - in a first alternative, exactly one lighting unit (1, 2, 3) is switched on and the or each other lighting unit is switched off and - in a second alternative, exactly one lighting unit (1, 2, 3) is switched off and the or each other lighting unit is switched on, wherein the image recording system (4.1, 4.2) is designed to generate a sequence of images of the illuminated surface (Ob) such that the respective light field (Lfi, Lf2, Lfs) of each lighting unit (1, 2, 3) lies in the field of view (Bfi, Bf2) of at least one camera (4.1, 4.2) of the image recording system, wherein this sequence comprises at least one image of the surface (Ob) for each lighting unit (1, 2, 3), which image is generated while this lighting unit (1, 2, 3) is switched on in the first alternative and switched off in the second alternative, and wherein the control device (10) is designed to - to determine by evaluating the sequence of images which light field (Lfi, Lf2, Lfs) originates from which lighting unit (1, 2, 3), and - to determine, using this information, how the light fields (Lfi, Lf2, Lfs) are positioned relative to one another. Lighting device (100) according to one of the preceding claims, characterized in that the lighting device (100) is designed to provide, as a user specification, a user specification concerning the maximum irradiance (Ee m ax.i) of a first lighting unit (1 ) of the lighting device (100), and the control unit (10) is designed to control the first lighting unit (1 ) in such a way that, in response to the control, the first lighting unit (1 ) on the surface (Ob) has a maximum irradiance (Ee m ax.i) according to the user specification, wherein the control device (10) is further designed to - the maximum total irradiance (Ee m ax,ges) when the user specification is implemented and - when the predicted maximum total irradiance (Ee max, ges) is greater than the upper limit (Ee max, re q) 'St, to control the or at least one second lighting unit (2, 3) of the lighting device (100), which is different from the first lighting unit (1), in such a way that the or each controlled second lighting unit (2, 3) has a lower maximum irradiance (Ee m ax.2) than before the control and thus the actually achieved maximum total irradiance (Ee max ,ges) is less than or equal to the upper limit (Ee max, re q) 'St. Lighting device (100) according to one of the preceding claims, characterized in that the control unit (10) is designed to determine a lighting unit subset, wherein the lighting unit subset comprises at least one lighting unit (1, 2) of the lighting device (100) and at least one further lighting unit (3) of the lighting device (100) does not belong to the lighting unit subset, wherein the control unit (10) is further designed to - the respective maximum irradiance (Ee m ax.i, Eemax.2) of the or each lighting unit (1, 2) of the lighting unit subset and - the or each determined maximum irradiance (Ee m ax.i, Eemax.2) in predicting the maximum total irradiance (Ee max,ges) of the lighting device (100). Lighting device (100) according to claim 5, characterized in that the lighting device (100) is designed to detect a user specification, wherein the detected user specification - either the lighting unit subset or - the or each lighting unit (3) of the lighting device (100) that does not belong to the lighting unit subset is specified, and the control unit (10) is configured to determine the lighting unit subset using the detected user specification. Lighting device (100) according to claim 5 or claim 6, characterized in that each lighting unit is configured to generate a respective light field (Lfi, Lf2, Lfs) on the surface, and the control unit (10) is configured to automatically determine - how the light fields (Lfi, Lf2, Lfs) which the lighting units (1, 2, 3) achieve on the illuminated surface (Ob) are positioned relative to each other, and - to determine the lighting unit subset in such a way that the light fields of the lighting units (1, 2) of the lighting unit subset overlap, and the respective light field of the or each lighting unit (3) of the lighting device (100) not belonging to the lighting unit subset does not overlap with a light field of a lighting unit (1, 2) of the lighting unit subset. Lighting device (100) according to one of the preceding claims, characterized in that the control unit (10) is configured to detect an irradiance-changing event, wherein the irradiance-changing event causes or is at least suitable for changing the maximum total irradiance (Ee max, ges). wherein the control device (10) is further designed to - to determine, in response to the detection of the irradiance-changing event, which maximum total irradiance (Ee m ax,ges) the illumination device (100) on the surface (Ob) actually achieves, and - when the determined actually achieved total irradiance (Ee max, ges) is greater than the upper limit (Ee max, re q) 'St, to control at least one lighting unit (1, 2, 3) in such a way that after control the maximum total irradiance (Ee max, ges) the lighting device (100) on the surface (Ob) is less than or equal to the upper limit (Ee max, re q) 'St. Lighting device (100) according to claim 8, characterized in that at least one lighting unit (1, 2) is connected to a distance sensor (4.1, 4.2, 6.2) in such a way that the position and orientation of the distance sensor (4.1, 4.2, 6.2) relative to this lighting unit (1, 2) is unchangeable, wherein the distance sensor (4.1, 4.2, 6.2) is designed to measure a measure of the distance (disti, dist2) between the connected lighting unit (1, 2) and the illuminated surface (Ob) in a contactless manner, and wherein the control device (10) is designed to detect a change in the measured distance (disti, dist2) as the or an irradiance-changing event. Lighting device (100) according to claim 8 or claim 9, characterized in that a lighting unit comprises a touch sensor (8.1, 8.2) which is designed to detect a touch of the lighting unit (1, 2, 3), and the control unit (10) is designed to use a touch of the lighting unit (1, 2, 3) detected by the touch sensor (8.1, 8.2) as the irradiance-changing event or an irradiance-changing event. Lighting device (100) according to one of the preceding claims, characterized in that the lighting device (100) is designed such that a limitation mode can be activated and deactivated, wherein the control unit (10) is designed to - when the limitation mode is activated, the maximum total irradiance (Ee max,ges) of the lighting device (100) and then, if this is greater than the upper limit, to cause the control of at least one lighting unit (1, 2, 3) to be given the actually achieved maximum total irradiance (Ee m ax,ges) on the surface less than or equal to the upper bound (Ee max, re q) 'St, and - when the limit mode is deactivated, the upper limit (Ee) is exceeded m ax,req). Lighting method for illuminating a surface (Ob) of an object (Obj) using a lighting device (100) comprising at least two lighting units (1, 2, 3) for illuminating the surface (Ob), the method comprising the steps of - each lighting unit (1, 2, 3) illuminates the surface (Ob) with a maximum irradiance (Ee m ax.i, Eemax.2) illuminated, whereby the respective maximum irradiance (Eem ax.i, Eemax.2) a lighting unit (1, 2, 3) independent of the respective maximum irradiance (Ee m ax.2, Eemax.i) of the or any other lighting unit (2, 3, 1 ) is variable, - the illumination device (100) illuminates the surface (Ob) with a maximum total irradiance (Ee m ax,ges) illuminated, whereby the maximum total irradiance (Ee m ax,ges) of the maximum irradiances (Ee m ax.i, Eemax.2) of the lighting units (1, 2, 3), and - at least once a user specification concerning the maximum total irradiance (Ee m ax,ges) of the lighting device (100) or the respective maximum irradiance (Ee max .i, Eemax.2) of at least one lighting unit (1, 2, 3), wherein the detection of the user specification triggers the further automatically performed steps that - at least approximately predicting the maximum total irradiance (Ee m ax,ges) the lighting device (100) on the surface (Ob) will achieve when the lighting device (100) is operated according to the user specification, - the predicted maximum total irradiance (Ee m ax,ges) with a given upper bound (Ee m ax,req) for the maximum irradiance on the surface (Ob) and - if the predicted maximum total irradiance (Ee max, ges) is greater than the upper limit (Ee max, re q) 'St, depending on the recorded user specification, at least one lighting unit (1, 2, 3) is controlled in such a way that after the control the actually achieved maximum total irradiance (Ee max,ges) of the illumination device (100) on the surface (Ob) is less than or equal to the upper limit (Ee max, re q) 'St. Illumination method according to claim 12, characterized in that at least once as a user specification a user specification concerning the maximum irradiance (Ee m ax.i) a first illumination unit (1 ) of the illumination device (100), the step of determining the maximum total irradiance (Ee m ax,ges) involves the step of determining the maximum total irradiance (Ee m ax,ges) is predicted upon realization of the user specification, and the step of controlling at least one lighting unit (1, 2, 3) comprises the steps of - the first lighting unit (1 ) is controlled in such a way that, in response to the control, the first lighting unit (1 ) on the surface (Ob) has a maximum irradiance (Ee max.i) according to the user specification, and - when the predicted maximum total irradiance (Ee max, ges) is greater than the upper limit (Ee max, re q) 'St, the or at least one second lighting unit (2, 3) of the lighting device (100), which is different from the first lighting unit (1), is controlled in such a way that the or each controlled second illumination unit (2, 3) achieves a lower maximum irradiance on the surface (Ob) than before control and thus the actually achieved maximum total irradiance (Ee max ,ges) is less than or equal to the upper limit (Ee max, re q).

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