Lighting device and lighting method with limit of maximum irradiance

Abstract

The invention relates to an illumination device (100) and a method for illuminating a surface (Ob) with a maximum total irradiance. At least two lighting units (1, 2, 3) of the lighting device (100) each illuminate a surface (Ob) with a maximum irradiance. The control device (10) actuates each lighting unit (1, 2, 3) independently of the other lighting units and thereby changes the maximum irradiance of the lighting unit (1, 2, 3). The lighting device (100) detects a user preset (9) relating to a maximum total irradiance. In response thereto, the control device (10) predicts which maximum total irradiance will be caused by the implementation of the user specification (9). If the predicted maximum total irradiance is greater than a preset upper limit, the control device actuates the at least one lighting unit (1, 2, 3) according to a user preset. The upper limit is followed by manipulation.

Description

Technical Field

[0001] The invention relates to a lighting device and a lighting method. Background Art

[0002] Such lighting devices and such lighting methods are used, for example, to illuminate an operating table on which a patient to be treated medically lies. The lighting enables the treating physician to carry out the medical treatment and in doing so to have a good view of the area of ​​the patient's body to be treated.

[0003] The radiation energy is inevitably delivered to the patient's body by the illumination, and the patient's body is thus heated up. In the case of too strong illumination, there is a risk of the patient's tissue dehydration and / or the patient suffering from burns.

[0004] Standard IEC60601-2-41 (currently the 3rd edition) applies to lighting equipment that can illuminate operating tables. The standard stipulates that the maximum irradiance of the lighting unit of medical lighting equipment cannot be greater than 1000W / m 2 , 700W / m in the future 2 This requirement applies to every distance between the lighting device and the operating table, measured along the central axis of the lighting device and at every point in time. Summary of the invention

[0005] The object of the present invention is to provide a lighting device and a lighting method which reduce the risk of endangering an object, for example a patient, by lighting with a relatively high degree of reliability.

[0006] This object is achieved by a lighting device having the features of claim 1 and a lighting method having the features of claim 2. Wherever appropriate, advantageous configurations of the lighting device according to the invention are also advantageous configurations of the lighting method according to the invention, and vice versa.

[0007] Some terms used subsequently with respect to medical lighting units are first defined below.

[0008] The lighting unit comprises at least one light source, preferably a plurality of light sources, wherein the light sources are fastened to a carrier and are preferably designed as LEDs. In one embodiment, the position and orientation of the light source relative to the position and orientation of the light source or each other light source of the same lighting unit is invariable during use. It is also possible to assign a controllable actuator to at least one light source, in particular to an assembly with a plurality of light sources, wherein the actuator can move the light source or the assembly relative to the carrier and therefore also relative to the light source or at least one other light source.

[0009] The or each light source emits a light beam, respectively, which light beam generally has the shape of a cone. In one implementation, the tip of the cone is ideally located in the light source. It is also possible that the optical device influences the shape of the light beam. A special case is a cylindrical light beam. The light beams generated by the light sources of the lighting unit generally overlap. The lighting unit has an optical center axis, which often coincides with the geometric center axis of the carrier.

[0010] The lighting unit has a spectral composition of the emitted light. This spectral composition of the lighting unit results from the spectral composition of the light of the individual light sources and is referred to below as the "spectrum" of the lighting unit. The color temperature is related to the spectrum.

[0011] "Illuminance" (Ev) describes the luminous flux per unit area incident on a surface. The SI unit is Lux = Lumen / m 2 . On a plane perpendicular to the optical center axis of the lighting unit, the illuminance of the lighting unit typically takes a maximum value in the intersection of the optical center axis and the plane. Usually, this maximum illuminance value varies along the optical center axis, that is, it varies as follows: starting from the lighting unit, this maximum value increases until the maximum value reaches a maximum value and then decreases again. The value at this maximum value is called the "maximum illuminance in space" of the lighting unit. Usually, the maximum illuminance in space is incident on the optical center axis. The area where the illuminance takes the maximum value may be located on the illuminated surface, or between the illuminated surface and the lighting unit. If the surface will be transparent, then at a sufficiently small distance, this area will also be located behind the illuminated surface in the radiation direction.

[0012] Typically, the maximum illuminance in a space that can be achieved by the lighting unit is known from the construction of the lighting unit or from measurements that have been performed before first use, in particular from the illuminance of the light source and the positioning of the generated light beam relative to one another. By the construction of the lighting unit or from the measurements performed, it is also known how the maximum value of the illuminance on the optical center axis depends on the distance. This functional dependence of the illuminance on the distance can depend on other adjustable or construction-induced parameters of the lighting unit.

[0013] Typically, a user can cause, either through user input or automatically through manipulation of a control device, that the actual maximum illuminance in a space is less than the maximum achievable illuminance in the space. The following discusses the "maximum achievable" and "maximum currently achieved" illuminance in a space. The maximum currently achieved illuminance is less than or equal to the maximum achievable illuminance in the space. The maximum illuminance actually achieved on a surface typically depends on the position and orientation of the lighting unit relative to the surface, whereas the maximum achievable illuminance in the space depends neither on the position nor on the orientation.

[0014] The user can often set and change the maximum light intensity of the lighting unit on the fly. In one implementation, the user can set the maximum light intensity in the space. In another implementation, the user can set the maximum light intensity in a preset reference distance from the lighting unit. In the case of surgical lights, this reference distance is often 1 m. The maximum light intensity in the reference distance is equal to or less than the maximum achievable light intensity in the reference distance. Typically, the maximum light intensity in the space of a medical lighting unit is achieved at a distance that differs from the reference distance by at most 10 cm.

[0015] When the lighting unit illuminates the surface of an object, such as an operating table or a patient on the operating table, the illuminance on the illuminated surface changes. Ideally, the illuminance achieved by the lighting unit on the illuminated surface takes a maximum value in 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 space. Generally, it is assumed that the maximum value occurs in the intersection of the optical center axis of the lighting unit and the illuminated surface, i.e. even if the illuminated surface is curved, which is the case when the patient is illuminated, and / or inclined to the center axis.

[0016] When referring to the "distance" between the lighting unit and the illuminated surface below, if not explicitly stated otherwise, this distance refers to the distance between the lighting unit and the illuminated surface along the optical center axis, even if the smallest spacing 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 medical lighting units, the term "illuminance" usually refers to the illuminance at a reference distance of, for example, 1 m between the lighting unit and the illuminated surface, wherein the illuminated surface is perpendicular to the optical center axis of the lighting unit. The lighting device is thus usually constructed so that ideally the maximum illuminance in space occurs on the optical center axis and at the reference distance from the lighting unit. In practice, this goal is usually not achieved exactly.

[0019] How bright a surface appears to an observer, either by itself and / or due to reflections, can be measured in Cd / m 2 The luminous density ("luminance") is described in units of . If the surface itself does not emit light, the luminous density depends on the light intensity on the surface and 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 2Irradiance is also called "radiant intensity" or "radiant flux density", and was formerly known as "radiant current 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 spectrum of the lighting unit. When the proportionality factor remains constant, the maximum irradiance and the maximum illuminance in space therefore occur in the same area.

[0021] Corresponding to the illuminance, we also talk about the "maximum irradiance" generated by the lighting device on the illuminated surface. This maximum irradiance also typically reaches its maximum value in the intersection of the optical center axis of the lighting unit and the illuminated surface. The maximum value is also called the "peak irradiance".

[0022] Light field diameter d x is understood to be the diameter of a circle around the area of ​​maximum illuminance, wherein the circle is defined such that the average value of the respective illuminances in the various points of the circle is equal to x% of the maximum illuminance in the plane of the circle. For example, the points are evenly distributed over the circle. The plane of the circle is perpendicular to the optical center axis of the lighting unit. Typical values ​​of x in the medical field are 10% and 50%. In the case of surgical lamps, d 10 Usually between 13cm and 35cm. x Usually depends on the distance between the lighting unit and the plane of the circle, so the light field diameter d x Related to the reference distance, which is typically 1 m in the case of medical applications. In many cases, the user can cause the light field diameter d to be x Note: Since irradiance is proportional to light intensity, if the light field diameter d x is related to irradiance rather than illumination, the same light field diameter d is obtained x .

[0023] In the medical field, it is often desired or even required by guidelines, such as the IEC 60601-2-41 guideline for surgical lights: 2*d 50 >d 10 This requirement results in boundary conditions for how the light beams of the light sources of the lighting unit are positioned relative to one another.

[0024] A "light field" is understood to be an area on the surface of an object which is illuminated by a lighting unit. Two characteristics of a light field are the illuminance distribution map and the irradiance distribution map. The two distribution maps assign the illuminance or irradiance, respectively, to each point on the illuminated surface. The two distribution maps differ from each other only by a scaling factor which depends on the spectrum of the lighting unit.

[0025] Typically, when the illuminated surface is planar, that curve on the illuminated surface where the illuminance and irradiance is x% of the maximum illuminance or irradiance has an elliptical, in particular circular, shape around the point with the maximum illuminance or irradiance. In a three-dimensional representation, where the illuminated surface extends in the xy plane and the corresponding illuminance or irradiance at the point (x, y) is plotted on the z axis, the light field typically approximates the shape of a bell curve that is rotationally symmetric about the z axis.

[0026] The illumination, irradiance, light field and light field diameter of the lighting unit may of course vary over time, in particular due to actions of the user, in particular when the user moves the lighting unit. If not otherwise noted, the respective current values ​​are referred to.

[0027] If light hits the body, the body absorbs part of the light and reflects the rest. "Heat energy" (also called thermal energy) has the unit joule. The heat energy input into the illuminated body is the integral of the absorbed irradiance over the illuminated area and over time, i.e., the time the object is illuminated. The illuminated body, for example a patient on an illuminated operating table, obtains heat energy input through the lighting device that illuminates the operating table, and optionally obtains heat energy input through other energy sources, such as a heating device for the operating table, a heat radiator, and the ambient temperature. The body emits heat energy to the environment, in particular depending on its body temperature and the ambient temperature. After the start-up phase, thermal equilibrium occurs, in which the heat energy input is equal to the heat energy emitted. The patient's body temperature usually rises slightly, and thermal equilibrium is established by this increase.

[0028] On the one hand, it is desirable to illuminate the area of ​​the patient's body in which the medical treatment takes place well. This is achieved by high light intensity and / or illumination. However, a high illumination also leads to a high maximum irradiance. Therefore, on the other hand, the maximum total irradiance should not become too large in order not to endanger the patient. If the maximum total irradiance on the illuminated surface of the patient is too high, burns and / or dehydration may occur.

[0029] Generally speaking, medical operating lights cause up to 50W of thermal energy input. However, the term "thermal energy" describes the load that is averaged in space and time on the patient's body due to illumination. However, especially in medical applications, areas of the body are often strongly illuminated so that doctors can safely perform medical treatment. This may lead to high local loads on the body due to the supply of radiant power. Therefore, the above-mentioned thermal balance appears later in this area than the thermal balance averaged over the entire body. In addition, especially when the operating light is turned on, the irradiance may change rapidly. The consequence is: in this area or in a smaller part of the body, a much higher temperature than in the rest of the body is reached. These temperature differences cannot usually be effectively and quickly balanced by the circulation itself in the patient's body or by emitting heat to the environment. This may cause the wound part to be dehydrated, the area of ​​the body to be locally heated, and in extreme cases, even slight burns may occur. Therefore, according to the present invention, there is no restriction or at least not only restriction on the thermal energy defined in the previous section.

[0030] The invention reduces the risk of harming a patient due to an excessively high maximum total irradiance of a lighting device. The maximum total irradiance is a measure of the current radiant power of the lighting device applied locally and locally to the patient's body. This distinguishes the maximum total irradiance from the thermal energy that is averaged in a certain way over the patient's body and integrated over time.

[0031] The lighting device according to the invention comprises at least two lighting units, each of which is capable of illuminating the same surface. Thus, in many cases, the illuminated surface and thus the objects on the illuminated surface are illuminated from multiple sides, which is often not possible with a single lighting unit. This feature reduces the effect of shading caused by the object when it comes into the area between the lighting device and the illuminated surface. Such objects are, for example, medical instruments or body parts of a treating physician.

[0032] Preferably, the respective position and orientation of each lighting unit relative to the illuminated surface can be varied, i.e. independently of the respective position and orientation of the or each other lighting unit of the lighting device. Restrictions are, of course, that two lighting units cannot penetrate each other, and one lighting unit cannot penetrate other objects.

[0033] Therefore, the lighting device according to the invention comprises at least two lighting units. Each lighting unit emits light and generates a light field and thus generates irradiance on an illuminated surface, for example on an illuminated surface of a patient or an operating table. Of course, it is possible to switch off at least one lighting unit at a certain point in time.

[0034] The light fields of the lighting units are additively superimposed. The “total irradiance” of a lighting device is understood to be the irradiance which the lighting device currently achieves on the illuminated surface via its lighting units in total. The total irradiance also assumes a maximum value on the illuminated surface, which is denoted by the maximum total irradiance and can vary over time. The maximum total irradiance depends on the maximum irradiance achieved by the lighting units of the lighting device on the illuminated surface and generally on the positions of the light fields relative to one another on the illuminated surface and to a lesser extent on the light field diameter and / or the correlated color temperature.

[0035] The lighting device according to the invention further comprises a signal processing control device (control unit). The control device is able to control each lighting unit, that is to say independently of the or each other lighting unit of the lighting device. The purpose and thus the effect during the control is to change, in particular to reduce, the maximum irradiance of the controlled lighting unit. Optionally, the control device can change the light field diameter and / or the correlated color temperature of the lighting unit by the control.

[0036] Typically, each lighting unit comprises a plurality of individual light sources, in particular LEDs. Preferably, each lighting unit comprises at least two groups of light sources, wherein each light source group comprises at least one light source. Preferably, the control device is able to control each light source group independently of the or each other light source group of the lighting unit and to change the maximum irradiance of the light source group by the control. It is also possible that the light sources of the lighting unit can only be controlled together, i.e. all light sources of the lighting unit belong to the same light source group.

[0037] Each individual light source and each light source group respectively generates a maximum irradiance on the surface. In order to change the maximum irradiance of the controlled lighting unit, the control device causes the respective maximum irradiance of at least one light source group to be changed.

[0038] In order to change the maximum irradiance of the light source group, the control device causes: different values ​​are assigned to the light intensity parameters of the light source group. In one implementation, the control device causes: the maximum irradiance that the light source group can generate in the space is changed by manipulation. In another implementation, the control device causes: the light field diameter or its spectrum is changed by manipulating the light source group, and the color temperature is related to the light field diameter or the color temperature. These implementations can be combined with each other.

[0039] Preferably, the lighting unit comprises at least two different light source groups, which can be controlled independently of one another. In one embodiment, the control device causes: a different value is assigned to the light intensity parameter of at least one light source group, while at least one other light source group remains unchanged. In another embodiment, the value of the light intensity parameter is changed similarly, for example by the same factor or the same absolute value.

[0040] The lighting device according to the invention is capable of detecting a user preset. The user preset relates to the maximum total irradiance of the lighting device or to the maximum irradiance of at least one lighting unit. "Relates" means that the user preset causes or is at least suitable for changing the maximum total irradiance or the maximum irradiance. The user preset can in particular relate to the irradiance to be achieved in the space at a maximum, optionally to the light field diameter or the correlated color temperature of the lighting device or the lighting unit. The user preset can be a preset value of the parameter or can include a preset for changing a current value, for example by means of a slide regulator or by means of plus and minus keys.

[0041] The control device is designed to automatically react to user-preset detections as follows:

[0042] The control device predicts at least approximately which maximum total irradiance the lighting device will achieve on the surface when the lighting device is operated according to the user preset. Preferably, the control device makes the prediction under the assumption that the lighting device is operated in a variable manner according to the user preset and is otherwise unchanged, in particular the respective distance between each lighting unit and the illuminated surface and each maximum irradiance remains unchanged except for the user preset. In general, the maximum total irradiance predicted by the control device is an estimate of the maximum irradiance on the surface that will actually result from the implementation of the user preset.

[0043] An upper limit is preset for the maximum total irradiance that can actually or possibly be achieved by the lighting device on a surface. The upper limit can be preset in particular by a user or by a superior control device. When the upper limit is exceeded, there is a risk that the illuminated person will be injured or harmed in other ways. In one design, the upper limit is fixedly preset and cannot be changed. In another design, the maximum possible upper limit is fixedly preset, for example due to legal presets or due to regulations of the manufacturer or user of the lighting device. The user can cause a lower upper limit to be actually used by a corresponding user input or a superior control device. The control device detects a fixed upper limit or an upper limit preset by a user or a superior control device.

[0044] The control device compares the predicted maximum total irradiance with the preset upper limit. If the predicted maximum total irradiance is greater than the upper limit, the control device controls at least one lighting unit of the lighting device. The control depends on the detected user preset. The goal of the control is preferably to realize the user preset as desired or at least as much as possible. During the control, the control device causes the following boundary condition to be observed: the actually achieved maximum total irradiance of the lighting device actually achieved after the control is less than or equal to the preset upper limit. Usually, the control depends on the user preset and the predicted maximum total irradiance. A special case is that the control device leaves the lighting device unchanged, because even only partial implementation of the user preset will result in: the upper limit will be exceeded.

[0045] Therefore, the control device ideally causes the preset upper limit to not be exceeded by the control in the following way, that is, the user presetting is realized as the user wishes. "Ideally" means that the prediction is an estimate that may deviate from reality, and the control device preferably uses the signal of the sensor for the prediction, wherein the signal may also be erroneous. Since the upper limit is ideally adhered to, the risk of the illuminated patient being injured due to an excessive maximum irradiance or overloading the eyes of nearby persons or damaging the object is reduced.

[0046] The present invention eliminates the need for the user to have to take care not to exceed the upper limit during the user presetting. This applies in particular to user presettings that do not directly preset a value or increase in the maximum total irradiance, but rather a value or increase in another parameter that influences the maximum total irradiance, such as the maximum irradiance of the lighting unit or the light field diameter.

[0047] It is possible that the lighting device comprises an input unit with which the user can change the maximum total irradiance. The input unit can be designed so that the user cannot increase the maximum total irradiance beyond an upper limit. The present invention can be combined with such a design. However, the present invention enables the user to change other parameters of the lighting device, such as the maximum irradiance or the light field diameter or the correlated color temperature of the lighting unit. According to the present invention, the control device also prevents in this case the upper limit of the maximum total irradiance from being exceeded, without the need for a corresponding design of the input unit and indeed without the need for the user to pay attention to observing the upper limit.

[0048] In one embodiment, the control device then calculates the maximum total irradiance that the lighting devices actually achieve on the surface in total. This embodiment will be described in more detail further below. According to the invention, the control device additionally or alternatively predicts a maximum total irradiance, which would result from the user preset if the user preset would be implemented as desired. If an upper limit would be exceeded as a result, the control device prevents the upper limit from being actually exceeded by correspondingly controlling at least one lighting unit. A special case is that the control device leaves the lighting device unchanged and therefore does not implement the user preset, because otherwise the upper limit would be exceeded. The invention thus prevents the undesirable event that the upper limit is first exceeded, then the event is determined and then the maximum total irradiance is reduced again. Such an effect could in particular endanger the patient and / or strain or fatigue the eyes of persons in the environment of the illuminated surface.

[0049] The invention can be operated in combination with a design in which the control device continuously determines the maximum total irradiance currently actually achieved, for example with a fixed sampling frequency. In the case of this design, how quickly the exceeding of the upper limit is detected depends on the control device and the corresponding sampling frequency of the optional sensor and also on the computing power of the control device. However, due to the invention, such continuous sampling is not required. On the contrary, the maximum total irradiance is predicted when necessary, that is, after detecting the user preset. In some cases, this feature saves computing power and / or computing time of the control device.

[0050] The following design is possible: if the predicted maximum total irradiance is greater than the upper limit, the control device causes: a corresponding message, in particular an alarm, is output in at least one form perceptible by humans. However, since according to the present invention, the control device automatically controls at least one lighting unit when the upper limit is exceeded, the present invention eliminates the need to output such a message. This is particularly advantageous because many messages often accumulate in clinical daily life. Therefore, the present invention reduces the risk that the maximum total irradiance is significantly exceeded or exceeded for a long time because the user does not perceive the corresponding message or does not react correctly to such a message. It is possible that the control device controls at least one lighting unit and additionally causes the output of a message.

[0051] According to the invention, the control device predicts which maximum total irradiance the lighting device will achieve on the illuminated surface if the user preset will be achieved as expected. According to the invention, the control device uses the detected user preset for the maximum total irradiance or the maximum irradiance of at least one lighting unit. Different designs are possible, which other information the control device uses to predict the maximum total irradiance. The invention can be implemented even without this other information.

[0052] Preferably, the control device determines and uses a respective maximum irradiance for each lighting unit, wherein the lighting unit actually achieves this maximum irradiance on the illuminated surface. Typically, the control device uses an approximation of the actual maximum irradiance.

[0053] In one implementation, the maximum achievable illuminance in the space is preset for each lighting unit. Due to its construction and manufacture, the lighting unit can achieve at most this irradiance, wherein this maximum value does not necessarily occur on the illuminated surface, but for example at a reference distance of 1 m. The maximum irradiance actually achieved by the lighting device in the space is less than or equal to the maximum achievable irradiance in the space and depends on the control of the lighting device. The maximum irradiance achieved on the surface is less than or at most equal to the maximum irradiance achieved in the space.

[0054] In one design solution, the control device uses the maximum irradiance actually achieved in the space of the lighting unit as the maximum irradiance achieved on the surface, and determines the maximum irradiance achieved in the space based on the maximum irradiance that can be achieved and the control of the lighting unit. The maximum irradiance approximately determined in this way may be more significantly greater than the maximum irradiance actually achieved on the surface, but is generally not less than the maximum irradiance actually achieved on the surface.

[0055] In another design solution, it is considered that the maximum irradiance achieved by the lighting unit on the illuminated surface depends on the distance between the lighting unit and the surface, and can therefore be less than the maximum irradiance achieved by the lighting unit in space. According to this other design solution, the lighting device includes 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 is additionally used between the distance sensor and the optical center axis of the lighting unit, wherein the lateral offset is preset by the construction and remains unchanged during operation. The control device uses the maximum irradiance achieved in space and the measured distance to determine the maximum irradiance achieved on the surface.

[0056] Different implementations of the distance sensor are possible. In one implementation, the distance sensor emits electromagnetic radiation or sound waves to a surface, the surface reflects at least a portion of the electromagnetic radiation or sound waves, a portion of which strikes the distance sensor again, and the run time of the electromagnetic radiation or sound waves is measured. The run time is a measure of the distance sought. It is also possible to measure attenuation, which is a measure of the spacing.

[0057] In another embodiment, the lighting unit is connected to a camera, which is directed at the surface and comprises an autofocus function. The autofocus function automatically focuses the camera on the illuminated surface. The distance sensor detects at which distance the autofocus function focuses the camera. The autofocus distance is an estimate of the distance sought. This design concept eliminates the need for a separate distance sensor. In many cases, such cameras already exist, for example to enable a visual representation of the illuminated surface on a spatially distant output unit.

[0058] In one implementation, the camera is positioned and designed such that at least one image of the camera shows all or at least some of the light fields generated by the lighting units on the surface. The control device evaluates the image and determines how large each light field in the image is. Furthermore, the control device detects for each lighting unit: which light field diameter d does the lighting unit have at a preset reference distance? x , for example by read access to the data memory. The light field diameter d at the reference distance x is a parameter determined by the configuration that can be changed by the user, but which does not depend on the distance being sought. The control device compares the size of the light field in the image with the diameter of the light field in the reference distance and derives the corresponding distance based on the result of the comparison. The reference distance is of course preset by the control device.

[0059] The image described above only shows a plurality of light fields on the surface, provided that a plurality of lighting units are switched on. In one embodiment, the control device automatically determines which light field originates from which lighting unit. In many cases, the camera is fixedly connected to the lighting unit. The control device detects 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 fixedly connected to a distance sensor. The measured distance between the lighting unit and the surface, the diameter dx of the light field of the lighting unit and the diameter of the light field in the image enable the control device to recognize in many cases the light field originating from the lighting unit with the distance sensor.

[0060] It is possible for the control device to detect a set light field diameter at a reference distance from at least one lighting unit without a distance sensor and to determine by an automatic plausibility check which light fields in the image may originate from the lighting unit and which light fields may not originate from the lighting unit.

[0061] In a preferred embodiment, the distance sensor can contactlessly scan the illuminated surface and thereby generate a 3D topographic profile of the illuminated surface. Such distance sensors are known under the name "Time-of-Flight Sensor" and are described, for example, in DE 10 2013 012 231 A1 and DE 10 2012 014 716 A1. The control device uses this topographic 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.

[0062] In one design solution, the control device uses the terrain profile to determine the minimum distance between the terrain profile of the illuminated surface and the lighting unit. The minimum distance can be less than the distance along the optical center axis. The control device uses the minimum distance and the maximum irradiance in the space of the lighting unit to determine the maximum irradiance on the surface of the lighting unit. It is also possible that the control device derives an average distance from the terrain profile and uses the average distance.

[0063] According to the design scheme just described, the control device determines the maximum irradiance achieved by the lighting unit on the surface according to the following, namely

[0064] - the irradiance achieved by the lighting unit in the space, and

[0065] - The measured distance between the lighting unit and the illuminated surface.

[0066] Preferably, the control device uses a characteristic curve which specifies a factor as a function of the distance, wherein the factor specifies which percentage of the maximum achievable irradiance in the room the lighting unit can actually achieve at this distance. The characteristic curve is known by 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 device has at least temporary read access.

[0067] In one embodiment, the control device predicts the maximum total irradiance as the sum of the maximum irradiances of the lighting units, wherein if the user specification relates to one lighting unit, the maximum irradiance to be achieved according to the user specification is used. The maximum irradiance results from the maximum achievable irradiance and the actuation of the lighting device. Preferably, switched-off or defective lighting units are not taken into account in this summation. This embodiment does not require the signals of the sensors, in particular the measured distances, but can lead to a prediction of a maximum total irradiance that is too large, but not too small.

[0068] Each lighting unit generates a light field on the illuminated surface. The term "light field" has been further defined above. If the illuminated surface is perpendicular to the optical center axis of the lighting unit, an irradiance exceeding x% of the maximum irradiance occurs inside a circle, where x is, for example, 10%, and where the center of the circle is the intersection of the optical center axis with the surface. The diameter of this circle is the light field diameter d x The circle of lighting units can be arranged concentrically, and the maximum total irradiance is then ideally equal to the sum of the maximum irradiances of the lighting units. If the centers of the circles are not coincident, however, this sum is usually greater than the maximum total irradiance.

[0069] In one embodiment, the control device can determine at least approximately how the light fields are positioned relative to each other. The lighting unit generates these light fields on the illuminated surface. The control device uses the user presetting, the maximum irradiance of the lighting unit and additionally the determined positioning of the light fields relative to each other to predict the maximum total irradiance.

[0070] Various designs are possible for how the control device determines how the light fields of the lighting units are positioned relative to one another. In the case of these designs, the control device preferably determines, in particular, how far apart the two optical center axes of the two lighting units are from one another with the two intersection points of the illuminated surface. In the case of two lighting units, there is one such distance, in the case of three lighting units, there are three such distances, and in the case of 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, optionally, in the determination of the maximum total irradiance. The distance between the two intersection points can of course be equal to zero.

[0071] It is possible that each lighting unit is connected to a distance sensor and an orientation sensor, respectively. The distance sensor measures a measure of the distance between the lighting device and the illuminated surface. The orientation sensor measures how the optical center axis of the lighting device is positioned in space. The control device uses the signals of these two sensors to determine how the light fields are positioned relative to each other.

[0072] In one embodiment, 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 immutable. Each of the at least two distance sensors is capable of contactlessly scanning the illuminated surface. The distance sensor provides at least two topographic 3D profiles of the illuminated surface, i.e. in many cases from different viewing directions. The control device compares the topographic profiles with one another and uses the result of this comparison to determine how the light fields of the lighting units are positioned relative to one another on the surface. Preferably, the control device additionally uses the position and orientation of the distance sensor at the lighting unit relative to the optical center axis of the lighting unit, which is determined by the construction, to derive the position and orientation of the optical center axis relative to the topographic profile. Preferably, the control device derives from the comparison of the two topographic profiles how far the intersection points of the optical center axis with the surface are respectively from one another. In many cases, the control device is able to determine the position of the third light field relative to the first two light fields even if the third light field originates from a lighting unit that is not connected to such a distance sensor.

[0073] According to the invention, the control device is capable of operating each lighting unit of the lighting device independently of the or each other lighting unit. According to one implementation, the control device is capable of operating the lighting units during the measuring period as follows: In a first alternative, at each point in time during the measuring period, exactly one lighting unit is switched on and the or each other lighting unit is switched off. In a second alternative, at each point in time during the measuring period, exactly one lighting unit is switched off and the or each other lighting unit is switched on. The measuring period is used to determine how the light fields of the lighting units are positioned relative to each other. Preferably, the lighting units are switched on and off so frequently that one does not perceive flickering but rather a continuous illumination of the surface.

[0074] According to this other implementation, the lighting device comprises an image recording system. The image recording system comprises at least one camera. In one implementation, 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 corresponding light field of each lighting unit is located 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 the image has been generated during the period when the lighting unit was switched on in the first alternative and switched off in the second alternative. Therefore, the image only shows the light field of the lighting unit in the first alternative, and only shows the corresponding light field of the or each other lighting unit in the second alternative. Therefore, the sequence comprises at least as many images as the lighting device comprises lighting units. Each image of the sequence is provided with a timestamp (the point in time when the image was generated).

[0075] The control device evaluates the sequence of images. Preferably, the control device computationally superimposes the images of the sequence. The control device uses the images with time stamps and the points in time at which the lighting units were respectively switched on or off to determine which light field on the surface originates from which lighting unit. The control device in turn uses this information to determine how the light fields are positioned relative to each other.

[0076] Due to this design solution, the positioning of the light field can be determined even if all lighting units emit light with the same spectrum. Furthermore, although possible, due to this design solution, it is not necessary to measure the respective position and orientation of each lighting unit in the space.

[0077] In one application, the design can additionally be used to determine the distance between the lighting unit and the illuminated surface. The size of the light field in the image and the diameter of the light field in the reference distance of the lighting unit provide an estimate of the distance between the lighting unit and the surface.

[0078] As already stated, the irradiance of a lighting unit is proportional to the illuminance, wherein the proportionality factor depends on the spectrum of the lighting unit. In one design, the control device determines the corresponding spectrum for each lighting unit. The spectrum of a lighting unit depends on the spectrum determined by the configuration of the above-mentioned light source group of the lighting unit and the corresponding maximum irradiance of the light source group. The control device uses the determined spectrum to predict the maximum total irradiance and optionally determines the maximum total irradiance actually achieved.

[0079] The maximum irradiance of the lighting unit can additionally depend on the angle at which the optical center axis of the lighting unit intersects the illuminated surface. In one design, the control device determines the corresponding angle for each lighting unit and uses the determined angle to predict the maximum total irradiance and optionally determines the maximum total irradiance actually achieved.

[0080] According to the invention, the control device predicts the maximum total irradiance, i.e. predicts it in response to the detection of a user input. If the predicted maximum total irradiance is greater than a preset upper limit, the control device controls at least one lighting unit and thereby prevents the upper limit from being exceeded, at least significantly.

[0081] Different designs are possible for how the control device causes the upper limit not to be exceeded.

[0082] In one design solution, the user preset relates to the maximum total irradiance. For example, the user presets that the maximum total irradiance to be achieved should be increased. In response to the detection of this user preset, the control device preferably controls each lighting unit - optionally, except for switched-off or defective lighting units. By controlling, the control device changes the corresponding maximum irradiance of each lighting unit according to the user preset, i.e., so that an upper limit is not exceeded. It is possible that due to this preset the user preset is not implemented exactly as desired, i.e., remains less than the user desired. This design solution is particularly advantageous when the maximum total irradiance has reached or almost reached the upper limit, and the user preset increases the maximum total irradiance. It is even possible that the lighting device remains unchanged.

[0083] In one implementation of the design solution, the control device causes the corresponding maximum irradiance of each lighting unit to be changed by the same factor through manipulation. In another implementation, the control device causes the maximum irradiance of the lighting unit that currently achieves the maximum or minimum maximum irradiance among all lighting units of the lighting device to be changed.

[0084] In another embodiment, the user preset relates to a specific first lighting unit selected by the user. For example, the user wants to be able to illuminate a specific area on the illuminated surface more intensely, for example because a patient should be treated medically in this area. Therefore, the user presets that the maximum irradiance and / or the light field diameter and / or the color temperature of the first lighting unit directed to this area should be changed, in particular increased.

[0085] Preferably, in the case of this further design, the control device manipulates the first lighting unit to which the user preset relates, and thereby causes: the maximum irradiance of the first lighting unit to be changed, ideally according to the user preset. If the maximum irradiance of the first lighting unit is increased according to the user preset by manipulation, while all other things remain unchanged, the maximum total irradiance may therefore exceed the preset upper limit. According to the present invention, in the case of this further design, the control device also predicts: which maximum total irradiance will be achieved from the realization of the user preset, that is, if the maximum irradiance of the first lighting unit is changed as the user preset.

[0086] Preferably, the control device causes the first lighting unit to be changed according to a user preset. If the upper limit would be exceeded due to this change, the control device selects another lighting unit, controls it, and thereby causes the maximum irradiance of the other lighting unit to be reduced. The goal during this control is that the maximum total irradiance is at most equal to the upper limit. If the lighting device includes at least three lighting units, it is possible that the control device selects a plurality of other lighting units and reduces the respective maximum irradiances of these selected other lighting units.

[0087] This design solution can be achieved in many cases: as desired by the user, a specific area on the illuminated surface is illuminated differently than before, in particular more intensely than before, that is, by the first lighting unit, and nevertheless the upper limit is not exceeded. Preferably, the control device selects at least one other lighting unit, wherein the light field of the other lighting unit does not overlap or only overlaps relatively little with the light field of the first lighting unit. It is also possible that the control device selects the lighting unit that currently achieves the highest maximum irradiance among all other lighting units as the other lighting unit.

[0088] It is possible that at least a first lighting unit of the lighting device is directed at a first area of ​​the illuminated surface, in particular at a first area of ​​a patient on an operating table. The first area is particularly sensitive to the input of thermal energy and is, for example, the chest or face of the patient. At least one other lighting unit is directed at another area that is less sensitive to thermal energy. Preferably, the corresponding light field of the or each first lighting unit does not overlap or at least does not significantly overlap with the corresponding light field of the or each other lighting unit. Usually, the upper limit only needs to be observed for the first area.

[0089] In the case of this application, it is important that the maximum total irradiance achieved by the first lighting unit in total is less than or equal to the upper limit. The maximum irradiance of the second lighting unit is preferably not taken into account. This design enables the first area to be illuminated as brightly as possible or as desired without exceeding the upper limit.

[0090] In one design, the control device thus determines a subset of lighting units, namely the first lighting unit of the application just mentioned. The lighting unit subset includes at least one lighting unit of the lighting device. At least one other lighting unit of the lighting device belongs to the remaining set and therefore does not belong to the subset of lighting units. The control device is able to determine the respective maximum irradiance of each lighting unit of the subset of lighting units. In order to predict the maximum total irradiance of the lighting device, the control device uses user presets, the determined maximum irradiances of the (first) lighting units of the subset of lighting units and optionally information about how the light fields of these first lighting units are positioned relative to each other. Preferably, the control device does not use the irradiances of the remaining lighting units.

[0091] Different implementations of how the control device determines the subset of lighting units are possible.

[0092] In one implementation, the lighting device detects a corresponding user preset. In one implementation, the user preset specifies the or each lighting unit of the subset of lighting units, and in another implementation, specifies the or each lighting unit of the lighting device that does not belong to the subset of lighting units. In many cases, the user can reliably preset which lighting units are aimed at the heat-sensitive area.

[0093] Another implementation can be combined with the design described further above, in which the control device determines how the light fields of the lighting units are positioned relative to each other. According to this combination, the control device determines overlapping light fields. The lighting units that produce these overlapping light fields belong to a subset of lighting units. Each other lighting unit does not belong to the subset of lighting units. The light field of the or each other lighting unit therefore does not overlap with the light fields of the lighting units of the subset of lighting units.

[0094] According to the invention, the control device predicts the maximum total irradiance, i.e., predicts in response to having detected an event preset by the user. The user preset relates to the maximum total irradiance or the maximum irradiance of the lighting unit. The control device implements the user preset so that the maximum total irradiance does not exceed an upper limit. In one design, the control device is additionally capable of subsequently determining the maximum total irradiance actually achieved and reducing the maximum total irradiance if necessary. The process by which the control device determines the maximum total irradiance achieved is triggered in that the control device detects an irradiance-related event. The irradiance-related event changes the maximum total irradiance, or is at least suitable for changing the maximum total irradiance. The event has already occurred and can only be verified afterwards, whereas according to the invention, the user preset is first verified and then implemented as described above. Typically, irradiance-related events are caused by user intervention or user action.

[0095] According to this design, the control device determines at least approximately the maximum total irradiance achieved by the lighting device on the surface after an illuminance-related event. If the determined maximum total irradiance is greater than an upper limit, the control device controls at least one lighting unit. As a result, the control device causes the maximum total irradiance to be (again) reduced. This design reduces the risk that the maximum total irradiance is greater than the upper limit for a longer period of time. Nevertheless, due to this design, it is not necessary to continuously determine the current actual maximum total irradiance with a high sampling frequency. More precisely, the maximum total irradiance is re-determined at least when necessary, i.e. when an irradiance-related event, i.e., a sign that the actual maximum total irradiance may change, is detected.

[0096] In one implementation, the control device controls all lighting units of the lighting device and causes: the corresponding maximum irradiance of each lighting unit is reduced, for example, by the same percentage or the same absolute value. It is also possible that the control device only reduces the maximum irradiance of those lighting units that do not belong to the above-mentioned subset of lighting units.

[0097] Various designs of which irradiance-related events the control device is able to detect are possible.

[0098] In one embodiment, the lighting device comprises at least one distance sensor, preferably one distance sensor for each lighting unit. The or each distance sensor can measure a measure of the distance between itself and the illuminated surface. As an irradiance-related event, the control device detects the following event: at least one measured distance has changed, in particular decreased, by more than a preset lower limit. Since the maximum irradiance of a lighting unit depends on the distance between the lighting unit and the surface, a changed distance of the lighting unit can result in a changed maximum total irradiance.

[0099] In another embodiment, the lighting device comprises at least one touch sensor, preferably one touch sensor for each lighting unit. The or each touch sensor is capable of detecting the following event: a user touches the touch sensor and thereby touches the connected lighting unit. For example, the touch sensor is mounted at the handle of the lighting device. The user touches the lighting unit, in particular the handle of the lighting unit, usually with the purpose of changing the distance between the lighting unit and the illuminated surface and / or the orientation of the lighting unit.

[0100] According to the invention, the control device is capable of controlling each lighting unit independently of the or each other lighting unit, wherein the purpose of such control is or can be to change the maximum irradiance of the lighting unit. By controlling, the control device at least partially implements the user preset or reacts to the user intervention. In addition, the control device prevents or at least causes afterwards that the maximum total irradiance is less than or at most equal to a preset upper limit. In one design, the lighting device is designed so that the control device strives not to make the maximum total irradiance greater than the upper limit during the entire operation of the lighting device.

[0101] In another design solution, the lighting device can be operated in two different modes, namely in an activated limiting mode and in a deactivated limiting mode. In the activated limiting mode, the control device operates as just described, i.e. the maximum total irradiance is predicted in response to a user preset, and the maximum total irradiance actually achieved is therefore less than or equal to an upper limit. Optionally, in the activated limiting mode, the control device reacts to the detection of irradiance-related events as just described. In the deactivated limiting mode, the control device is able to achieve a maximum total irradiance greater than an upper limit. In one design solution, the control device predicts the maximum total irradiance even in the deactivated limiting mode, but does not operate the lighting unit with the purpose of not exceeding the upper limit. If the maximum total irradiance is greater than the upper limit and the limiting mode is deactivated, the control device preferably outputs a corresponding message in a form perceptible by humans.

[0102] The lighting device is preferably capable of detecting a user input which specifies whether the lighting device should be operated with the restricted mode activated or deactivated. It is possible that the user activates the restricted mode in response to a message that the upper limit is exceeded. In response to this, the control device controls at least one lighting unit with the purpose of reducing its maximum irradiance.

[0103] In one application, the lighting device according to the invention is used to illuminate a medical operating table. The operating table is designed so that a patient to be treated medically lies on the operating table. The lighting device can be used in particular in the interior of a building or a vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0104] The present invention is described below based on embodiments. In this case,

[0105] Figure 1 A lighting device with three lighting units and a camera is shown schematically in cross section;

[0106] Figure 2 Shown by Figure 1 An example of three light fields implemented by three lighting units, where two light fields overlap;

[0107] Fig. 3 schematically shows a first example of the light fields of two lighting units and the resulting total light field;

[0108] Fig. 4 schematically shows a second example of the light fields of two lighting units and the resulting total light field;

[0109] Figure 5 A lighting device having three lighting units and two cameras is schematically shown in cross section, which lighting device illuminates an uneven surface;

[0110] Figure 6 Schematically shows Figure 5 The lighting unit and the illuminated surface of the device;

[0111] FIG7 schematically shows three images, Figure 6 The cameras of the devices respectively generate the images. DETAILED DESCRIPTION

[0112] In this embodiment, the invention is used to illuminate an object Obj in the form of an operating table. A patient, not shown, who is being treated medically, lies on the operating table Obj. The lighting device 100 according to the invention illuminates the operating table Obj or that surface Ob 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 in simplified form. Of course, the illuminated surface of the patient on the operating table Obj is not flat. Note: The figures are not necessarily drawn to scale.

[0113] The lighting device 100 of the present embodiment includes three lighting units 1 , 2 , and 3 , which illuminate the operating table Obj vertically or obliquely from above and from up to three different directions. Figure 1 and Figure 5 Schematically shown are two different embodiments of the lighting device 100. Unless explicitly mentioned otherwise, the following description relates to both embodiments.

[0114] Preferably, the lighting units 1, 2, 3 are movably fastened to the ceiling and can be moved independently of one another. The respective position and orientation of each lighting unit 1, 2, 3 in space can be changed, i.e. preferably independently of the position and orientation of the other lighting units or each other lighting unit. In one design, the hinge of each lighting unit 1, 2, 3 is designed so that the lighting unit 1, 2, 3 does not change its position and orientation relative to the illuminated surface Ob by itself, but only after user intervention. In another design, each lighting unit 1, 2, 3 can be locked and unlocked again in a desired position and orientation.

[0115] The lighting units 1, 2, 3 each have an optical center axis. In this embodiment, the optical center axis of the lighting unit 1 is identical to the geometric center axis MA.1, and the optical center axis of the lighting unit 2 is identical to the geometric center axis MA.2. In this embodiment, the first lighting unit 1 is rotationally symmetric about the center axis MA.1, and the second lighting unit 2 is rotationally symmetric about the center axis MA.2. The third lighting unit 3 is only shown schematically. Of course, other designs are also possible, in particular a different number of lighting units. The lighting units 1, 2, 3 do not necessarily have to be rotationally symmetric. In Figure 1 and Figure 5 In the orientation of the two lighting units 1 and 2 shown in FIG, the two central axes MA.1 and MA.2 enclose an angle between them which is preferably between 25° and 70°. The two central axes MA.1 and MA.2 are inclined to the illuminated surface Ob and are located Figure 1 and Figure 5 In the illustrated situation, the central axis MA.3 of the lighting unit 3 is perpendicular to the illuminated surface Ob.

[0116] Along the optical center axes MA.1, MA.2, the illuminance and irradiance of the lighting units 1, 2 are maximum. More precisely: in a plane perpendicular to the optical center axes MA.1, MA.2, the illuminance and irradiance take their maximum values ​​at the intersection of this plane with the optical center axes MA.1, MA.2. The corresponding content applies to the third lighting unit 3. The maximum illuminance and maximum irradiance in the space of the lighting units 1, 2, 3 are also located on the optical center axes MA.1, MA.2. Figure 1 and Figure 5 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 drawn.

[0117] Figure 2 The three light fields Lf1, Lf2, Lf3 generated by the lighting units 1, 2, 3 on the illuminated surface Ob in a possible situation are schematically illustrated. The illuminated surface Ob is located at Figure 2, and the two center axes MA.1 and MA.2 are inclined to this plane. Two ellipses are shown, on which the illuminance and thus the irradiance are 10% of the corresponding maximum illuminance and thus the irradiance on the surface Ob. In the interior of these ellipses, the illuminance and the irradiance are greater, in the exterior they are less than 10% of the corresponding maximum values. For illustration purposes, the interiors of the two ellipses are dotted in different ways. In the case shown, the center axis MA.3 of the third lighting unit 3 is perpendicular to the illuminated surface Ob, so that the area in which the irradiance is 10% of the maximum irradiance is a circle. In the case shown, this circle does not overlap with the two ellipses of the two lighting units 1 and 2. For example, the two lighting units 1 and 2 illuminate the chest area of ​​the patient, and the lighting unit 3 illuminates the legs. In another possible case, not shown, the two light fields overlap almost concentrically.

[0118] The orientation of the three lighting units 1, 2, 3 relative to the illuminated surface Ob causes the illuminated surface Ob and thus the patient on the operating table Obj to be illuminated from three different directions. Therefore, even if an object, such as a body part of a doctor or an object, enters the area between the lighting device 100 and the illuminated surface Ob, the patient is usually still illuminated.

[0119] 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 around a 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 around a central axis MA.2. Figure 1 and Figure 5 Schematically showing the light beams Lb of the light sources 1.1, 1.2, ... 1.1 , Lb 1.2 , ... and the light beams Lb of the light sources 2.1, 2.2, ... 2.1 , Lf 2.2 , ... For illustration purposes, these light beams are dotted in different ways. A light source can radiate light of the same color temperature or of at least two different color temperatures.

[0120] Each beam Lb 1.1 , Lb 1.2 , ..., Lb 2.1 , Lf 2.2 , ... generate a single light field on the illuminated surface Ob. The light fields of the light sources of the illumination units 1, 2, 3 are superimposed on the illuminated surface Ob to form light fields Lf1, Lf2, Lf3, respectively. Therefore, the irradiances of the points on the illuminated surface Ob are added together. The illumination device 100 realizes a total light field Lf on the surface Ob.ges .

[0121] The total light field Lf generated is shown in FIG. 3 and FIG. 4 according to two examples. ges . Lighting units 1 and 2 are turned on, and lighting unit 3 is turned off. The illuminated surface Ob is perpendicular to Figure 3A , Figure 3B and Figure 4B The drawing planes illustrated below are , and the optical center axes MA.1 and MA.2 lie in these drawing planes. Conversely, the illuminated surface is located Figure 4A In the drawing plane. Figure 3A Schematically, two lighting units 1 and 2 and two central axes MA.1 and MA.2 are shown. Figure 3A and Figure 4B The corresponding irradiance Ee on the surface Ob is plotted on the y-axis. The cross-sections of the two light fields Lf1 and Lf2 through the two lighting units 1 and 2 and the total light field Lf ges 4 shows another example, in which the two light fields Lf1 and Lf2 overlap only a small amount.

[0122] The lighting device 100 further comprises an operating unit 9, which is only schematically shown, and a signal processing control device (control unit) 10, which is also only schematically shown. The operating unit 9 can receive user inputs and forward them to the control device 10. The control device 10 thus detects the user inputs. Preferably, the user can preset set values ​​for different parameters of the lighting units 1, 2, 3 or the entire lighting device 100 by means of the control device 9.

[0123] In particular, the user can preset for each lighting unit 1, 2, 3 a desired maximum illuminance in the room, for example on a continuous scale or a graduated scale from 0 to 10, where the value 10 corresponds to the maximum achievable illuminance in the room. The value 5 results in the actual maximum illuminance achieved in the room being equal to half the maximum achievable illuminance. Alternatively, the user presets that the value should be increased or decreased. A minus key and a plus key are shown by way of example. Furthermore, the user can enter a preset for each lighting unit 1, 2, 3, which specifies the desired light field diameter d x , and optionally also specifying the average spectrum of the lighting units 1, 2, 3. The desired light field diameter d x This refers to a reference distance of, for example, 1 m. In one embodiment, the user can also preset whether this lighting unit 1, 2, 3 should be included in the automatically implemented limitation of the total irradiance. In addition, the user can select or choose the lighting unit 1, 2, 3 by means of the control device 9, which is described further below.

[0124] The user can also specify the following parameters for the lighting device 100:

[0125] - an upper limit on the maximum total irradiance achieved by the lighting device 100 on the illuminated surface Ob, and

[0126] - Whether restricted mode should be activated or deactivated.

[0127] The meaning is further explained below.

[0128] The control device 10 receives a user's preset and controls the light sources of the lighting units 1, 2, 3 according to the preset. For example, the control device 10 sets the intensity of the current flowing through the light sources 1.1, 1.2, ..., 2.1, 2.2, ... or the voltage applied to the light sources 1.1, 1.2, ..., 2.1, 2.2, ... to a corresponding value. Preferably, the light sources 1.1, 1.2, ..., 2.1, 2.2, ... are operated in a pulsed manner, wherein the pulse frequency is so high that the observer perceives a constant illumination. The control device 10 can also change the illuminance of the light sources 1.1, 1.2, ..., 2.1, 2.2, ... by modulating the pulse width of the control device. In pulse width modulation, the control device changes the ratio between the duration of the pulse in which the light source is supplied with current and the duration of the time interval between two consecutive pulses. In a design solution, the control device 10 can change the corresponding illuminance of the light source independently of the illuminance of other light sources.

[0129] In this embodiment, the control device 10 reads access to a computer-evaluable table in which the maximum achievable illuminance of the lighting units 1, 2, 3 in the space resulting from the preset is stored for a plurality of possible preset values ​​that can be preset by the user. For example, storing a preset value 10 on a scale of 1 to 10 results in a desired maximum illuminance of 160 kLux in the space, which is equal to the maximum achievable illuminance, while a preset value 5 results in half of the maximum achievable illuminance, i.e. 80 kLux. This table is created and stored during a previous calibration of the lighting units 1, 2, 3. This table is preferably valid for each similar lighting unit 1, 2, 3 and is stored in the data memory of the lighting units 1, 2, 3. If the lighting device 100 comprises lighting units 1, 2, 3 of different configurations, then preferably different tables are also stored. Preferably, in the table, for the lighting units 1, 2, 3, it is also stored which setting values ​​for the light sources of the lighting units 1, 2, 3 result in the desired maximum illuminance in the space. These tables are created and stored in advance. The control device 10 reads access to these tables.

[0130] The control device 10 “knows” and uses a respective value for each of the parameters mentioned below for each lighting unit 1 , 2 , 3 , wherein the value does not depend on the position and orientation of the lighting unit 1 , 2 , 3 relative to the surface Ob:

[0131] - the maximum achievable illuminance and / or irradiance in the space,

[0132] - the functional dependence of the maximum illumination and / or irradiance on the surface Ob as a function of the distance along the optical center axis,

[0133] - optionally spectrally,

[0134] - Light field diameter d at reference distance x ,and

[0135] - Whether lighting units 1, 2, 3 should be included in the limitation of total irradiance.

[0136] The maximum achievable irradiance in the space of lighting units 1, 2, and 3 is denoted by Ee max，1，sp ,Ee max，2，sp ,Ee max，3，sp express.

[0137] In one design solution, the user presets the maximum achievable irradiance Ee in the space of each lighting unit 1, 2, 3 respectively. max，1，sp ,Ee max，2，sp ,Ee max，3，sp The control device 10 can operate each lighting unit 1, 2, 3 according to the set value. For example, a set value of 10 leads to the maximum achievable illuminance in the space, and a set value of 5 leads to half. In one design, a proportionality factor between the maximum irradiance and the maximum illuminance is stored, for example 4 W / m 2 / kLux. For example, a setting of 10 results in 640W / m 2 In a further development, a table is stored which provides respectively obtained proportional factors between the maximum irradiance and the maximum illuminance in the space for a plurality of possible spectra of the lighting units 1, 2, 3. For each lighting unit 1, 2, 3, the control device 10 derives the maximum achievable or maximum expected irradiance in the space of the lighting unit 1, 2, 3 from the corresponding set value, the maximum achievable illuminance in the space and the proportional factor.

[0138] In the following, the maximum irradiance caused or predicted by the lighting device 100 on the illuminated surface Ob is abbreviated to the term “maximum total irradiance” Ee max，ges .

[0139] In application, the control device 10 automatically determines: which maximum total irradiance Ee the lighting device 100 achieves on the illuminated surface Obmax，ges More precisely: the control device determines the maximum irradiance Ee max，ges The estimated value of Ee max，ges，est Possibly, the control device 10 performs this determination at a constant sampling frequency. In a preferred implementation, the control device 10 re-determines the maximum total irradiance Ee whenever an irradiance-related event has been detected. max，ges . Irradiance related events change the maximum total irradiance Ee max，ges Or at least suitable for changing the maximum total irradiance. Examples of irradiance related events are:

[0140] - The distance between the lighting units 1, 2, 3 and the surface has been changed, in particular reduced.

[0141] - The user touches the carrier of the lighting unit 1 , 2, 3: such touching is usually performed with the purpose of changing the position and / or orientation of the lighting unit 1 , 2, 3 relative to the surface.

[0142] Preferably, the lighting device 100 comprises a sensor capable of detecting irradiance-related events. The signal of such a sensor is transmitted to the control device 10. In another application, the control device 10 automatically predicts: in response to a user preset, which maximum total irradiance Ee of the lighting device 100 can be expected max，ges - More precisely: if the user presupposition is or will be realized in an unchanged way, it will or will appear.

[0143] In order to at least approximately determine the maximum total irradiance Ee currently actually achieved by the lighting device 100 on the illuminated surface Ob max，ges In this embodiment, the control device 10 uses the current actuation of the lighting units 1, 2, 3 and other sensor values. In order to at least approximately predict which maximum total irradiance Ee the lighting device 100 would achieve if the user presetting were to be implemented in an unchanged manner max，ges , the control device 10 uses this user preset, and otherwise uses the actual control of the lighting units 1, 2, 3. Therefore, if, for example, the user presets: the maximum irradiance Ee in the space of the lighting unit 1 should be max，1，sp Increases to the maximum value, the control device 10 uses the maximum irradiance Ee max，1，sp The maximum value of is used for prediction, while the actual current light field diameter and the current correlated color temperature of lighting unit 1 are used, while the corresponding currently achieved maximum irradiance, maximum light field diameter and correlated color temperature of the other two lighting units 2 and 3 are used. Note: User presets by which the light field diameters or correlated color temperatures of lighting units 1, 2, 3 should be changed can also lead to a maximum total irradiance Ee max，ges is enlarged.

[0144] Maximum total irradiance Eemax，ges The maximum permissible upper limit is stored in the data memory of the lighting device 100. The maximum permissible upper limit is, for example, 700 W / m 2 or 1000W / m 2 These values ​​are derived from the above standards for single medical lighting units. Note: The above standards specify upper limits for single lighting units, but not for lighting fixtures with multiple lighting units.

[0145] The user can preset a lower value for this upper limit, but not a higher value. The upper limit used, i.e. the upper limit preset from the factory or by the user, is denoted by Ee max，req The control device 10 determines or predicts the maximum total irradiance Ee max，ges With upper limit Ee max，req Make a comparison.

[0146] In one possible application, the lighting device 100 is always operated in the limiting mode. The control device 10 automatically ensures that the maximum total irradiance Ee actually achieved is max，ges Always less than or equal to the upper limit Ee max，req If the user presets, it will result in: the upper limit Ee will be exceeded max，req , the control device 10 causes: despite the user's preset, the upper limit Ee max，req This is explained below by taking the following as an example, that is, the user presets the following content: the maximum irradiance Ee in the space of the lighting unit 1 max，1，sp If this user preset were to be implemented and all other settings of the lighting units 1, 2, 3 would remain unchanged, the upper limit Ee would be exceeded in this example. max，req In one implementation, in response to the prediction, the control device 10 does not increase the maximum irradiance Ee of the lighting unit 1 as strongly as the user desires. max，1，sp In another preferred implementation, although the control device 1 increases the maximum irradiance Ee in the space of the lighting unit 1 as specified by the user preset max，1，sp , but reduce the maximum irradiance Ee of the other lighting unit 2 or 3 max，2，sp ,Ee max，3，sp , and thereby ensure that the upper limit Ee is not exceeded max，req .

[0147] In another possible application, the limiting mode can be activated or deactivated optionally, for example by a user via the operating unit 9 or automatically by the control device 10. When the limiting mode is deactivated, the control device 10 does not prevent the maximum total irradiance Ee max，ges Exceeding the upper limit Ee max，reqPreferably, when the predicted or determined maximum total irradiance Ee max，ges At the upper limit Ee max，req When the above, the control device 10 generates an alarm. This alarm is output in a form that can be perceived by humans.

[0148] It has been mentioned that the user can select at least one lighting unit 1, 2, 3 of the lighting device 100. Figure 1 and Figure 5 Schematically shown in FIG. 1 are three keys with labels 1, 2, and 3 on the operating unit 9. The control device 10 determines or predicts the maximum total irradiance Ee of the lighting device 100. max，ges The selected lighting unit 1, 2, 3 or each selected lighting unit 1, 2, 3 is not taken into account. Alternatively, the control device 10 only takes into account the selected lighting unit 1, 2, 3 or each selected lighting unit 1, 2, 3.

[0149] The application is explained exemplarily for the case where the user selects lighting unit 3. For example, lighting units 1 and 2 are directed at the patient's chest or face, and light fields Lf1 and Lf2 are superimposed there. Lighting unit 3 illuminates the patient's legs, and light field Lf3 of lighting unit 3 does not overlap with light fields Lf1 and Lf2. In the case of this application, the maximum irradiance generated by lighting units 1 and 2 together on the patient's chest or face should be less than or equal to the upper limit Ee max，req Lighting unit 3 does not illuminate the chest or face, but rather illuminates less sensitive areas of the patient and is not included in the constraints of the maximum total irradiance.

[0150] In the case of the design described below, all three lighting units 1 , 2 , 3 are included in the prediction or determination of the total irradiance, ie no lighting unit is selected or chosen by the user.

[0151] Maximum total irradiance Ee max，ges In particular it depends on the following parameters:

[0152] - the respective maximum illuminance achieved by the lighting units 1, 2, 3 on the surface Ob, and

[0153] - How the light fields Lf1 , Lf2, Lf3 realized by the lighting units 1 , 2, 3 on the surface Ob are positioned relative to each other.

[0154] The maximum irradiance achieved on the surface Ob is denoted by Ee max，1 ,Ee max，2 ,Ee max，3 It represents and is less than or equal to the maximum irradiance achieved in the space of lighting units 1, 2, 3. In this embodiment, the following assumptions are used: the maximum irradiance Ee max，1 ,Ee max，2 ,Eemax，3 Appear on the corresponding optical center axes MA.1, MA.2, MA.3.

[0155] Figure 2 3 and 4 show several examples of how the two light fields Lf1, Lf2 of the two lighting units 1, 2 are positioned relative to each other. The corresponding maximum irradiance Ee max，1 andEe max，2 , the total light field Lf ges and the maximum total irradiance Ee max，ges , that is, the total light field Lf ges The maximum irradiance on the illuminated surface Ob.

[0156] The control device 10 determines the maximum total irradiance Ee currently achieved or to be expected max，ges The estimated value is Ee max，ges，est To determine the estimated value, the control device 10 uses at least one, optionally each, of the above-mentioned parameters that are independent of the position and orientation of the lighting units 1, 2, 3 relative to the illuminated surface Ob, in particular parameters that are determined by the construction of the lighting units 1, 2, 3 and are therefore preset, and corresponding values ​​of the controls. The control device 10 converts the estimated value Ee max，ges，est With upper limit Ee max，rea Make a comparison.

[0157] In various embodiments of the invention, the control device 10 furthermore determines any one of the following parameters, determines corresponding values ​​of one or more of the following parameters, which depend on the current position and orientation 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 in order to determine the estimated value Ee max，ges，est :

[0158] - the respective distance between each lighting device 1, 2, 3 and the surface Ob, measured along the respective optical centre axis MA.1, MA.2, MA.3,

[0159] - the corresponding distances between the two intersection points of the two optical center axes MA.x, MA.y (y#x) with the surface Ob,

[0160] - The corresponding light field diameter d achieved by each lighting unit 1, 2, 3 on the illuminated surface Ob x ,

[0161] - other characteristics of the respective light field Lf1, Lf2, Lf3 of each lighting unit 1, 2, 3,

[0162] - whether at least two light fields overlap on the illuminated surface, and

[0163] - The angle between the optical centre axis of the lighting unit 1, 2, 3 and the plane into which the surface Ob extends.

[0164] First, a design is described below in which the control device 10 does not determine and use values ​​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 estimated value Ee determined is max，ges，est Always greater than or equal to the actual maximum total irradiance Ee max，ges , not less than. “The person is thus on the safe side.”

[0165] One simplification is that the respective maximum illumination and thus irradiance in space of each lighting unit 1, 2, 3 occurs on the illuminated surface Ob. According to another simplification, all optical center axes MA.1, MA.2, MA.3 intersect the surface Ob at the same point. Result: The three generated light fields Lf1, Lf2, Lf3 are positioned concentrically with each other. On a flat surface Ob, the three generated light fields Lf1 、 Lf2 and Lf3 are concentric ellipses, especially circles.

[0166] These two simplifications in particular dispense with the need to measure or otherwise determine the distances between the lighting units 1, 2, 3 and the surface Ob and the relative positioning of the light fields Lf1, Lf2, Lf3 to one another and result in the control device 10 providing the estimated value Ee max，ges，est Determined as the sum of the maximum irradiance in space, that is,

[0167] (1) Ee max，ges，est =Ee max，1，sp +Ee max，2，sp +Ee max，3，sp .

[0168] The design schemes according to FIGS. 3 and 4 are for the following two examples. The above assumptions may lead to the control device 10 setting too low an illumination and thus an irradiance at at least one lighting unit 1, 2, 3, i.e., the illumination of the lighting units 1, 2, 3 and the resulting maximum total irradiance Ee max，ges Less than the upper limit Ee max，req It is therefore possible that the illumination / irradiance of at least one lighting unit 1, 2, 3 is less than desired by the user. A number of design solutions are described below, in which the necessity of making the simplifications just described is avoided.

[0169] In one embodiment, the user additionally predefines which lighting units 1, 2, 3 generate or may generate overlapping light fields. The simplification just described is preferably used for those lighting units that generate overlapping light fields according to the predefinement. The maximum irradiance generated by these lighting units with overlapping light fields is generated according to the simplification just described. As the maximum total irradiance Eemax，ges，est This maximum irradiance in the space or the maximum irradiance of another lighting unit in the space is used, depending on which value is greater.

[0170] An example applies to Figure 2 and the situation shown in FIG3 . According to this example, the light fields Lf1 , Lf2 of the two lighting units 1 and 2 overlap, while the light field Lf3 of lighting unit 3 does not overlap. Then, the estimated value Ee of the maximum total irradiance is determined or predicted as follows max，ges，est :

[0171] (2) Ee max，ges，est =max[Ee max，1，sp +Ee max，2，sp , Ee max，3，sp ].

[0172] With that estimate, “people are still on the safe side.”

[0173] The design scheme described below eliminates the need for the user to preset which light fields overlap or can overlap. The preferred design scheme is described below. In the case of the following design scheme, the assumption just described can also be used, that is, for example, the maximum total irradiance Ee is determined or predicted according to formula (2): max，ges，est .

[0174] The first camera 4.1 is fastened to the carrier 5.1, see Figure 1 and Figure 5 That area of ​​the illuminated surface Ob which is illuminated by at least one illumination unit 1, 2 is located within the field of view Bf.1 of the first camera 4.1. Figure 5 In the case of a design of , the second camera 4.2 is additionally fastened to the carrier 5.2. The illuminated area is additionally located within the field of view Bf.2 of the second camera 4.2. It is also possible to fasten the camera to a separate carrier.

[0175] The first camera 4.1 and the optional second camera 4.2 each generate an image of the illuminated surface Ob. For example, the image looks similar to Figure 2 Similar to that shown in Figure 4.

[0176] The images of one camera 4.1 or of both cameras 4.1 and 4.2 show the light fields Lf1, Lf2, Lf3. However, it is not yet known from the images of the cameras 4.1, 4.2 which light field originates from which lighting unit.

[0177] Control device 10 can determine from the images of camera 4.1 and optionally both cameras 4.1 and 4.2 and the signals of the three sensors which light field originates from which lighting unit. Control device 10 preferably also uses the respective light field diameter dx set at lighting units 1, 2, 3.

[0178] The following describes a first implementation: how the control device 10 permanently or at least regularly detects which light field Lf1, Lf2, Lf3 originates from which lighting unit 1, 2, 3. During the measurement period during which this detection is performed, the three lighting units 1, 2, 3 (more generally: those lighting units currently in use) are operated in a pulsed manner, i.e. as follows:

[0179] In a first alternative to the first implementation, only exactly one lighting unit 1, 2, 3 is switched on at any given point in time, and all other lighting units are switched off. During the time interval, each lighting unit 1, 2, 3 is switched on at least once, preferably multiple times, as the only one.

[0180] In the second alternative, at any given point in time, exactly one lighting unit 1, 2, 3 is switched off, while all other lighting units are switched on. During this time interval, each lighting unit 1, 2, 3 is switched off at least once, preferably multiple times, as the only one. In many cases, the second implementation results in a higher illumination than the first implementation.

[0181] Preferably, the measuring period is so short that the respective position and orientation of each lighting unit relative to the surface is not significantly changed during the measuring period. In both alternatives, the pulse frequency is preferably so high that an observer perceives the three lighting units 1, 2, 3 as permanently switched on and emitting light, i.e. no flicker is perceived.

[0182] The first camera 4.1 and the second camera 4.2, which is optional in one embodiment, each record a sequence of images. In this case, the following boundary conditions are observed: at least one image of the sequence shows only the first light field Lf1, at least one image shows only the second light field Lf2, and at least one image shows only the third light field Lf3. The control device 10 evaluates these images, wherein the control device 10 preferably places the images one above the other in terms of calculation. The control device 10 derives at least one of the following information from the evaluation:

[0183] - The corresponding light field diameter d of each lighting unit 1, 2, 3 actually realized on the surface Ob x The diameter of the light field may be different from the diameter of the light field at the reference distance d x different,

[0184] - whether the light fields Lf1, Lf2, Lf3 overlap, and if so, how strongly,

[0185] - the distance of the point of maximum irradiance on the surface Ob and / or the center of the light field Lf1, Lf2, Lf3,

[0186] - How the areas of maximum irradiance of the lighting units 1 , 2 , 3 are positioned relative to one another on the surface Ob.

[0187] In order to determine which light field Lf1, Lf2, Lf3 originates from which lighting unit 1, 2, 3, the control device 10 determines in the case of the first alternative which light field is displayed in the image when the lighting unit x (x=1, 2, 3) is switched on and each other lighting unit y (y#x) is switched off. Correspondingly, in the case of the second alternative, the control device 10 determines which light field is not displayed. By means of image processing, the control device 10 determines which lighting units 1, 2, 3 produce the currently overlapping light fields.

[0188] In a second implementation, at least one, preferably each lighting unit 1, 2, 3 comprises a sensor, which measures the current position and orientation of the lighting unit 1, 2, 3 in space. The control device 10 uses the signals of these sensors to determine which light field originates from which lighting unit 1, 2, 3.

[0189] Both implementations can be combined with each other.The first implementation with two alternatives has the advantage that no sensors are needed which measure the position or orientation of the lighting units 1 , 2 , 3 in the space.

[0190] In the case of the design just described, the corresponding maximum irradiance Ee of the lighting units 1, 2, 3 in the space max，1，sp ,Ee max，2，sp ,Ee max，3，sp is used as the maximum irradiance Ee of the lighting units 1, 2, 3 on the surface Ob max，1 ,Ee max，2 ,Ee max，3 This design sometimes leads to a clear upper limit Ee max，req The maximum total irradiance Ee below max，ges Therefore, the respective distances dist1, dist2, dist3 between the lighting units 1, 2, 3 and the illuminated surface Ob are preferably measured and used.

[0191] In a preferred design, the following assumption is justified: the maximum irradiance Ee achieved by the lighting units 1, 2, 3 on the illuminated surface Ob is max，1 ,Ee max，2 ,Ee max，3 It occurs at the corresponding intersection point between the optical center axes MA.1, MA.2, MA.3 of the lighting units 1, 2, 3 and the surface Ob, that is, it is independent of the angle between the optical center axes MA.1, MA.2, MA.3 and the operating table Obj and thus the surface Ob. Figure 2 In the example shown in FIG4 , the situation is as follows: the maximum irradiance Eemax，1 ,Ee max，2 Appears in the intersection S.1 or S.2. If 2*d 50 >d 10 applicable, then the assumption is particularly correct.

[0192] Under this assumption, it is sufficient to measure the distances dist1, dist2 along the optical center axis between the lighting units 1, 2, 3 and the illuminated surface Ob. The control device 10 reads a computer-evaluable table for each lighting unit 1, 2, 3. In this table, the maximum irradiance Ee in the space is stored for different distances. max，1，sp ,Ee max，2，sp ,Ee max，3，sp and the maximum irradiance Ee on the surface Ob max，1 ,Ee max，2 ,Ee max，3 Preferably, the proportional factor is applicable to each lighting unit 1, 2, 3. Of course, it is possible to store the proportional factor separately for each lighting unit 1, 2, 3 and for different distances.

[0193] In one design solution, the control device 10 determines and uses the respective distances dist1, dist2, dist3 between the lighting units 1, 2, 3, but uses the simplified assumption that the light fields Lf1, Lf2, Lf3 are arranged concentrically with each other. The control device 10 determines the respective maximum irradiance on the surface Ob and derives the maximum total irradiance Ee, for example, according to the following calculation rule max，ges The estimated value of Ee max，ges，est :

[0194] (3) Ee max，ges，est =Ee max，1 +Ee max，2 +Ee max，3 .

[0195] If it has been preset or determined that the light field Lf3 of the lighting unit 3 does not overlap with the other two light fields Lf1, Lf2, the following calculation rule is also possible:

[0196] (4) Ee max，ges，est =max[Ee max，1 +Ee max，2 , Ee max，3 ].

[0197] It is possible that an object arrives in the area between the 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 center axis MA.1, MA.2, MA.3 then extends through the object, the control device 10 automatically detects this event. This is because the distance measured along the center axis MA.1, MA.2, MA.3 suddenly decreases. The control device 10 preferably uses the value that has been measured before this sudden decrease as the distance between the lighting unit 1, 2, 3 and the surface Ob.

[0198] Various designs for measuring distances along the optical center axes MA.1, MA.2, MA.3 are described below.

[0199] In one design solution, at least one distance sensor is fastened to at least one carrier 5.1, 5.2, 5.3 respectively. The distance sensor measures the distance between itself and the illuminated reflective surface Ob. Figure 1 In the example of , such a distance sensor 6.2 is shown, which is fastened to the carrier 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 fastened to each carrier 5.1, 5.2, 5.3, respectively. It is possible that a lateral distance occurs between the distance sensor and the central axis MA.1, MA.2, MA.3. This distance and the 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 construction of the lighting units 1, 2, 3. Preferably, the control device 10 is capable of correcting the measurement result of the distance sensor by means of the distance and the angle in order to determine the distance along the central axis.

[0200] In one implementation, the first camera 4.1 and / or the optional second camera 4.2 each have an autofocus function, so that the cameras 4.1, 4.2 are clearly set according to the illuminated surface Ob. In one implementation, the control device 10 uses the setting of the autofocus to determine the corresponding distance. It is possible that the control device 10 receives a plurality of measurement values ​​about the distance from a plurality of sensors respectively and aggregates these measurement values ​​into a distance.

[0201] As already stated, the control device 10 detects the respective light field diameter d of each lighting unit 1 , 2 , 3 x , for example 10 The diameter of the light field is d x is related to a preset reference distance of, for example, 1 m. Preferably, the control device 10 “knows” the respective imaging scale of the camera 4.1, 4.2 used or of each camera used. The light field diameter d xThe imaging scale specifies how large the image of the light field Lf1, Lf2, Lf3 of the lighting units 1, 2, 3 is if the plane of the light field Lf1, Lf2, Lf3 is perpendicular to the optical center axis MA.1, MA.2, MA.3 and is at a reference distance from the lighting units 1, 2, 3. In one embodiment, the control device 10 derives an estimated value of the distance dist1, dist2, dist3 between the lighting units 1, 2, 3 and the surface Ob measured along the center axis MA.1, MA.2, MA.3 from this size and the actual size in the image of the cameras 4.1, 4.2. It is also possible that the control device 10 measures how large the image of the light field is in the images of the cameras 4.1, 4.2. The control device 10 derives an estimated value of the distance dist1, dist2, dist3 between the lighting units 1, 2, 3 and the surface Ob from this size and the actual size in the image of the cameras 4.1, 4.2. x The sought distance between the cameras 4.1, 4.2 and thus the lighting units 1, 2 on the one hand and the light fields Lf1, Lf2, Lf3 and thus the illuminated surface Ob on the other hand is derived from the control device 10. Optionally, the control device 10 uses the imaging scale of the cameras 4.1, 4.2, which can be changed in an implementation of the cameras 4.1, 4.2.

[0202] It is possible that at least one lighting unit 1, 2, 3 comprises its own camera and / or another own distance sensor, and at least one other lighting unit comprises neither its own camera nor another own distance sensor. However, in certain cases, the corresponding distances can nevertheless be measured at least approximately. Figure 1 These implementations are described by the situation shown in , in which only the second lighting unit 2 has a distance sensor 6 . 2 and therefore only the distance dist2 between the second lighting unit 2 and the illuminated surface Ob can be measured directly.

[0203] exist Figure 1 In the situation shown in , in one implementation, the control device 10 uses the image of the camera 4.1 with the field of view Bf.1 to determine the respective size and position of each light field Lf1, Lf2, Lf3 on the illuminated surface Ob. The control device 10 also "knows" the respective geometry of each lighting unit 1, 2, 3 and the respective light field diameter d x. In addition, the control device 10 "knows" which diameter the circular area that the light sources 1.1, 1.2, ..., 2.1, 2.2, ... occupy in total on the carriers 5.1, 5.2, 5.3 has, i.e. which diameter the light beams generated respectively have at the carriers 5.1, 5.2, 5.3. The control device 10 determines for each lighting unit 1, 2, 3 the respective ratios between the diameter of the light field at the lighting unit 1, 2, 3 and the diameter of the light field Lf1, Lf2, Lf3 generated by the lighting unit 1, 2, 3 on the illuminated surface Ob. The control device 10 determines approximately the remaining distances from these ratios and from the measured distance dist2.

[0204] For lighting units 1 , 2 , 3 without distance sensors, the following simplified assumption is also possible: the actual distances dist1 , dist2 , dist3 between the lighting units 1 , 2 , 3 are equal to the reference distance explained above, for example 1 m.

[0205] As already stated, the control device 10 uses the respective distances between the lighting units 1, 2, 3 and the illuminated surface Ob to determine the respective maximum irradiance Ee of the lighting units 1, 2, 3 on the surface Ob max，1 ,Ee max，2 ,Ee max，3 For example, the distance is measured along the central axes MA.1, MA.2, MA.3.

[0206] In one design solution, a simplified assumption is used: the maximum irradiance Ee generated by the lighting units 1, 2, 3 on the surface Ob is max，1 ,Ee max，2 ,Ee max，3 The maximum irradiance occurs at the intersection S.1, S.2, S.3 of the optical center axis MA.1, MA.2, MA.3 of the lighting unit 1, 2, 3 and the illuminated surface Ob, i.e., it is independent of the angle between the center axis MA.1, MA.2, MA.3 and the surface Ob. The following design avoids the need to assume this simplified assumption and takes into account the possibility that the center axis MA.1, MA.2, MA.3 is not perpendicular to the plane, but inclined to the plane, and therefore even in the case of a bell-shaped light field Lf1, Lf2, Lf3, the maximum irradiance occurs outside the intersection of the center axis with the plane. It can be assumed that the illuminated surface Ob extends in a plane.

[0207] Furthermore, a design has been described above in which a sensor measures the current orientation of the lighting units 1, 2, 3 in the room. In one design, the control device 10 derives the angle between the central axis MA.1, MA.2, MA.3 and the surface Ob from the signal of the sensor. An alternative design eliminates the need for such a sensor. Figure 5This alternative design is described with reference to FIG. 7 .

[0208] In this embodiment, at least one camera 4.1, preferably both cameras 4.1, 4.2 are designed as so-called 3D cameras. The cameras 4.1, 4.2 have a field of view Bf.1 or Bf.2 and provide not only a brightness value as a grayscale or color value for each image point, but also, for each image point or at least for a sufficiently large number of image points, a distance between the image point 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.

[0209] Generally speaking, the illuminated surface Ob does not have a flat profile. Figure 5 Five elevations 7.1, ..., 7.5 are shown in FIG. 7 . The cameras 4.1, 4.2 scan the illuminated surface Ob in a contactless manner and thereby obtain a topographic profile of the surface Ob in the viewing directions MA.1, MA.2. Such cameras are known under the name "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 of the sensor generating the topographic profile are also possible, for example a suitable laser scanner, radar scanner or lidar scanner. It is also possible that the sensor generating the topographic profile is spatially separated from the cameras 4.1, 4.2.

[0210] Figure 5 The diagram illustrates how the two 3D cameras 4.1 and 4.2 generate a topographic profile of the illuminated surface Ob with these five elevations 7.1, . . . , 7.5, respectively, from two different viewing directions. Figure 6 It is shown how the second lighting unit 2 is positioned relative to the illuminated surface Ob. Fig. 7A It is shown that when the optical axis of the camera is perpendicular to the illuminated surface Ob, five elevations 7.1, ..., 7.5 are shown in the topographic profile, which is not the case for the two cameras 4.1 and 4.2. Figure 7B It is shown how five elevations 7 . 1 , . . . , 7 . 5 are represented in the topographic profile of the camera 4 . 2 on the carrier 3 . 2 of the second lighting unit 2 . Figure 7C It is shown how five elevations 7.1, ..., 7.5 are represented in the terrain profile of the camera 4.1. As is known, the closer an elevation 7.1, ..., 7.5 is to the respective camera 4.1, 4.2, the greater the elevation is represented.

[0211] The relief profiles of the two cameras 4.1 and 4.2 show the same illuminated surface Ob from two different viewing directions. Optionally, there is additionally a relief profile of a 3D camera (not shown) whose optical axis is perpendicular to the illuminated surface Ob.

[0212] The control device 10 "knows" the position of the 3D cameras 4.1, 4.2 relative to the optical center axes MA.1, MA.2. From this description, the control device 10 automatically derives the position of the center axes MA.1, MA.2 relative to the corresponding terrain profiles already provided by the cameras 4.1, 4.2. By evaluating the terrain profiles and the positions of the center axes MA.1, MA.2, the control device 10 derives the distances between the lighting units 1, 2 and the illuminated surface Ob measured along the center axes MA.1, MA.2. By computationally comparing these terrain profiles, the control device 10 determines the distance between the two intersection points S.1 and S.2 of the two center axes MA.1, MA.2 with the illuminated surface Ob. From this and from the corresponding light field diameters d of the lighting units 1, 2 at the reference distance. x , the control device 10 derives how strongly the two light fields Lf1 and Lf2 overlap, see Figure 2 To Figure 4.

[0213] In one embodiment, the control device 10 further determines the respective angles between the center axes MA.1, MA.2 and the plane in which the illuminated surface Ob extends. For example, the control device 10 performs a computational coordinate transformation to make the two topographic profiles coincide with one another. The two profiles show the same surface Ob. From the comparison, for example from the coordinate transformation, the control device 10 derives the angle between the two optical center axes MA.1, MA.2 of the lighting units 1, 2.

[0214] When another object enters the field of view Bf.1, Bf.2 of the cameras 4.1, 4.2, the or at least one terrain profile measured by the 3D cameras 4.1, 4.2 changes suddenly. The control device 10 detects this event automatically. To detect this event, the control device 10 preferably uses the current terrain profile and the terrain profile last measured before the event was detected. As long as the object is in the field of view Bf.1, Bf.2 and no other objects enter the field of view Bf.1, Bf.2, this terrain profile of the illuminated surface changes frequently. Preferably, the event of detecting another object entering the field of view Bf.1, Bf.2 does not trigger the step of changing the maximum irradiance.

[0215] As already stated, when operating in limiting mode, the control device 10 automatically ensures that the maximum total irradiance Ee is determined max，ges Less than or equal to the preset limit Ee max，reqAs already stated, in this embodiment, the user or a superior control device (not shown) presets a preset value for each lighting unit 1, 2, 3. From the preset value, the control device 10 derives the maximum irradiance Ee to be achieved in the space of the lighting unit 1, 2, 3. max，1，sp ,Ee max，2，sp The control device 10 controls the maximum irradiance Ee in the space from the lighting units 1, 2, 3 max，1，sp ,Ee max，2，sp The maximum irradiance Ee of the lighting units 1, 2, and 3 on the surface Ob is derived from max，1 ,Ee max，2 , and determines which maximum total irradiance Ee the lighting device 100 will achieve on the illuminated surface Ob due to the preset max，ges .

[0216] If the expected maximum irradiance Ee max，ges The estimated value Ee determined max，ges，est At the preset upper limit Ee max，req If the above, the control device 10 automatically reduces the illumination of at least one lighting unit 1, 2, 3, and thereby reduces the irradiance, that is, after the reduction, the preset upper limit Ee is complied with. max，req In one implementation, the control device 10 reduces the maximum illuminance to be achieved by all lighting units 1, 2, 3 to the same factor, for example, to Ee max，ges，est / Ee max，req If the illuminance obtained by the preset value or the illuminance obtained by automatic reduction leads to the upper limit Ee max，req If the desired maximum illuminance is achieved, the control device 10 controls the light sources of the lighting units 1 , 2 , 3 so that the controlled lighting units 1 , 2 , 3 reach the desired maximum illuminance.

[0217] It is possible that the user increases the preset value for lighting unit x (x=1, 2, 3) during operation of the lighting device 100. The control device 10 automatically checks whether the increased preset value still results in a value less than or equal to the preset upper limit Ee max，req The maximum total irradiance Ee max，ges If the preset value for the increase of the lighting unit x results in the preset limit Ee max，req The estimated maximum irradiance Ee above max，ges，est , the control device 10 automatically reduces the illumination of another lighting unit y (y#x) in a design solution. This design solution results in that the illumination of lighting unit x can actually be increased as desired by the user, and thus, for example, a specific area of ​​the patient can be illuminated more strongly. In particular, it is possible to illuminate the patient from a different direction than before. At the same time, this design solution results in an upper limit Ee max，reqContinue to be followed.

[0218] Reference numerals list

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[0221]

Claims

1. A lighting device (100) for illuminating a surface (Ob) of an object (Obj), The lighting device (100) comprises - at least two lighting units (1, 2, 3) and - a signal processing control device (10), Each lighting unit (1, 2, 3) is designed to provide a maximum irradiance (Ee max.1 ,Ee max.2 ) lighting surface (Ob), The lighting device (100) is designed to provide a maximum total irradiance (Ee max,ges ) lighting surface (Ob), The maximum total irradiance (Ee max,ges ) depends on the maximum irradiance (Ee) of the lighting units (1, 2, 3) max.1 ,Ee max.2 ), The control device (10) is designed as - each lighting unit (1, 2, 3) is controlled independently of that lighting unit or each other lighting unit, and - thereby changing the maximum irradiance (Ee) of the lighting unit (1, 2, 3) max.1 ,Ee max.2 ), The lighting device (100) is designed to detect the maximum total irradiance (Ee max,ges ) or the maximum irradiance (Ee max.1 ,Ee max.2 ) related user presets, The control device (10) is further designed to automatically respond to a user-preset detection - predicting at least approximately which maximum total irradiance (Ee) the lighting device (100) achieves on the surface (Ob) when the lighting device (100) is operated according to a user preset max,ges ), -The predicted maximum total irradiance (Ee max,ges ) and the preset upper limit (Ee) of the maximum irradiance on the surface (Ob) max,req ) for comparison, and -When the predicted maximum total irradiance (Ee max,ges ) is greater than the upper limit (Ee max,req )hour, At least one lighting unit (1, 2, 3) is controlled according to the detected user preset, so that after the control, the maximum total irradiance (Ee) actually achieved by the lighting device (100) on the surface (Ob) is max,ges ) is less than or equal to the upper limit (Ee max,req ).

2. The lighting device (100) according to claim 1, characterized in that Each lighting unit (1, 2, 3) of the lighting device (100) is designed to generate a light field (Lf1, Lf2, Lf3) on the surface (Ob), respectively, and The control device (10) is designed to - for each lighting unit (1, 2, 3) of the lighting device (100), respectively, determining which maximum irradiance (Ee) the lighting unit (1, 2, 3) actually achieves on the surface (Ob) max.1 ,Ee max.2 ), - determining how the light fields (Lf1, Lf2, Lf3) generated by the lighting units (1, 2, 3) on the illuminated surface (Ob) are positioned relative to each other, and - Using the detected user preset, the determined maximum irradiance achieved (Ee max.1 ,Ee max.2 ) and the generated light field (Lf1, Lf2, Lf3) under the determined positioning of the lighting device (100) max,ges ).

3. The lighting device (100) according to claim 2, characterized in that: The lighting device (100) comprises an image recording system having at least one camera (4.1, 4.2) and The control device (10) is designed to control the lighting units (1, 2, 3) during the measurement period so that At each time point in the measurement 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 (Lf1, Lf2, Lf3) of each illumination unit (1, 2, 3) is located in the field of view (Bf1, Bf2) of respectively at least one camera (4.1, 4.2) of the image recording system, wherein for each lighting unit (1, 2, 3), the sequence comprises in each case at least one image of the surface (Ob), which image was generated while the lighting unit (1, 2, 3) was switched on in the case of the first alternative and was switched off in the case of the second alternative, and The control device (10) is designed as - determining which light field (Lf1, Lf2, Lf3) originates from which lighting unit (1, 2, 3) by evaluating the image sequence, and - Using this information it is determined how the light fields (Lf1 , Lf2, Lf3) are positioned relative to each other.

4. The lighting device (100) according to any one of the preceding claims, characterized in that The lighting device (100) is designed to detect a maximum irradiance (Ee) of a first lighting unit (1) of the lighting device (100). max.1 ) as a user preset, and The control device (10) is designed to control the first lighting unit (1) so that the first lighting unit (1) achieves a maximum irradiance (Ee) on the surface (Ob) according to a user preset in response to the control. max.1 ), The control device (10) is further designed as - Predict the maximum total irradiance (Ee) when achieving the user preset max,ges ),as well as -When the predicted maximum total irradiance (Ee max,ges ) is greater than the upper limit (Ee max,req )hour, A second lighting unit (2, 3) or at least one second lighting unit (2, 3) of a lighting device (100) different from the first lighting unit (1) is controlled so that The or each actuated second lighting unit (2, 3) achieves a lower maximum irradiance (Ee) on the surface (Ob) than before the actuation. max.2 ),and The maximum total irradiance (Ee max,ges ) is less than or equal to the upper limit (Ee max,req ).

5. The lighting device (100) according to any one of the preceding claims, characterized in that The control device (10) is designed to determine a subset of lighting units, The lighting unit subset includes at least one lighting unit (1, 2) of the lighting device (100), and at least one other lighting unit (3) of the lighting device (100) does not belong to the lighting unit subset, The control device (10) is further designed as - determining the respective maximum irradiance (Ee) of the or each lighting unit (1, 2) of the subset of lighting units max.1 ,Ee max.2 ),as well as - In predicting the maximum total irradiance (Ee) of the lighting device (100) max,ges ) when using the or each determined maximum irradiance (Ee max.1 ,Ee max.2 ).

6. The lighting device (100) according to claim 5, characterized in that The lighting device (100) is designed to detect user presets, The detected user preset specifies - a subset of lighting units, or - the or each lighting unit (3) of the lighting device (100) which does not belong to the subset of lighting units, and The control device (10) is designed to determine the subset of lighting units using the detected user presets.

7. The lighting device (100) according to claim 5 or claim 6, characterized in that: Each lighting unit is designed to generate a light field (Lf1, Lf2, Lf3) on the surface, respectively, and The control device (10) is designed to automatically determine - how the light fields (Lf1, Lf2, Lf3) realized by the lighting units (1, 2, 3) on the illuminated surface (Ob) are positioned relative to each other, and - Determine a subset of lighting units such 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 the light fields of the lighting units (1, 2) of the lighting unit subset.

8. The lighting device (100) according to any one of the preceding claims, characterized in that The control device (10) is designed to detect irradiance change events, The irradiance change event causes or at least applies to a change in the maximum total irradiance (Ee max，ges ), The control device (10) is further designed as - determining, in response to the detection of an irradiance change event, which maximum total irradiance (Ee) is actually achieved by the lighting device (100) on the surface (Ob) max，ges ),as well as - If the actual achieved total irradiance (Ee max，ges ) is greater than the upper limit (Ee max，req ),but At least one lighting unit (1, 2, 3) is controlled so that after the control, the maximum total irradiance (Ee) of the lighting device (100) on the surface (Ob) is max，ges ) is less than or equal to the upper limit (Ee max，req ).

9. The 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) such that the position and orientation of the distance sensor (4.1, 4.2, 6.2) relative to the lighting unit (1, 2) is immutable, wherein the distance sensor (4.1, 4.2, 6.2) is designed to measure the distance (dist1, dist2) between the connected lighting unit (1, 2) and the illuminated surface (Ob) in a contactless manner, and The control device (10) is designed to detect a change in the measured distance (dist1, dist2) as the irradiance change event or irradiance change event.

10. The lighting device (100) according to claim 8 or claim 9, characterized in that: The lighting unit comprises a touch sensor (8.1, 8.2) designed to detect a touch of the lighting unit (1, 2, 3), and The control device (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 change event or irradiance change event.

11. The lighting device (100) according to any one of the preceding claims, characterized in that The lighting device (100) is designed to be able to activate and deactivate the restricted mode, The control device (10) is designed as - predicting the maximum total irradiance (Ee) of the lighting device (100) when the limiting mode is activated max,ges )as well as If the maximum total irradiance is greater than the upper limit, the maximum total irradiance (Ee) actually achieved on the surface when the at least one lighting unit (1, 2, 3) is actuated is caused. max,ges ) is less than or equal to the upper limit (Ee max,req ),and - Enables the upper limit (Ee) to be exceeded when the limit mode is deactivated max,req ).

12. A 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), wherein the method comprises the following steps - Each lighting unit (1, 2, 3) is respectively provided with a maximum irradiance (Ee max.1 ,Ee max.2 ) lighting surface (Ob), The corresponding maximum irradiance (Ee) of the lighting units (1, 2, 3) max.1 ,Ee max.2 ) can be compared with the corresponding maximum irradiance (Ee) of the or each other lighting unit (2, 3, 1) max.2 ,Ee max.1 ) is changed irrelevantly, - The lighting device (100) is provided with a maximum total irradiance (Ee max,ges ) lighting surface (Ob), The maximum total irradiance (Ee max,ges ) depends on the maximum irradiance (Ee) of the lighting units (1, 2, 3) max.1 ,Ee max.2 ),and - at least one detection of the maximum total irradiance (Ee) of the lighting device (100) max,ges ) or the corresponding maximum irradiance (Ee) of at least one lighting unit (1, 2, 3) max.1 ,Ee max.2 ) related user presets, Among them, user-preset detection triggers other automatically executed steps: - predicting at least approximately which maximum total irradiance (Ee) the lighting device (100) achieves on the surface (Ob) when the lighting device (100) is operated according to a user preset max,ges ), -The predicted maximum total irradiance (Ee max,ges ) and the preset upper limit (Ee) of the maximum irradiance on the surface (Ob) max,req ) for comparison, and -When the predicted maximum total irradiance (Ee max,ges ) is greater than the upper limit (Ee max,req )hour, At least one lighting unit (1, 2, 3) is controlled according to the detected user preset, so that after the control, the maximum total irradiance (Ee) actually achieved by the lighting device (100) on the surface (Ob) is max,ges ) is less than or equal to the upper limit (Ee max,req ).

13. The lighting method according to claim 12, characterized in that At least once as a user preset detection and the maximum irradiance (Ee) of the first lighting unit (1) of the lighting device (100) max.1 ) related user presets, Predicted maximum total irradiance (Ee max,ges ) step includes predicting the maximum total irradiance (Ee) when achieving the user's preset max,ges ), and The step of operating at least one lighting unit (1, 2, 3) comprises the following steps: The first lighting unit (1) is controlled so that the first lighting unit (1) achieves a maximum irradiance (Ee) on the surface (Ob) according to a user preset in response to the control. max.1 ), -When the predicted maximum total irradiance (Ee max,ges ) is greater than the upper limit (Ee max,req )hour, The or at least one second lighting unit (2, 3) of the lighting device (10o) different from the first lighting unit (1) is controlled so that The or each actuated second lighting unit (2, 3) achieves a lower maximum irradiance on the surface (Ob) than before the actuation, and The maximum total irradiance (Ee max,ges ) is less than or equal to the upper limit (Ee max,req ).

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