LIGHT AND METHOD FOR OPERATING A LIGHT

Description

[0001] The invention relates to a lamp, in particular for testing workpiece surfaces, which has at least one control element and at least two light sources that emit electromagnetic radiation of different wavelength ranges, wherein for at least one of the light sources an intensity with which the light source emits is automatically adjustable, wherein a speed at which the intensity is changed is between 5 lux / s and 500 lux / s.

[0002] The invention further relates to a method for operating a lamp, in particular for testing workpiece surfaces, optionally using a fluorescent marking agent.

[0003] From US patent 2014 / 0111981 A1, a luminaire with three LED groups emitting light of different colors is known. The light intensity of each LED group can be controlled via one of three color switches, whereby the operation of the three color switches can be switched from a self-resetting to a latching function by means of a latching mechanism.

[0004] US Patent 2014 / 0225 514 A1 describes a solid-state light emission device comprising multiple LED components that can be controlled independently. This device is designed to produce a spectral output with varying ratios of scotopic and photopic light. The device can be controlled to allow transitions between different operating modes of the multiple LED components.

[0005] German patent DE 10 2006 004 995 A1 describes a light for dental or surgical use, comprising a light mixer with multiple LEDs or a multi-LED system and a downstream optic. To set a desired color, the intensity of the LEDs can be controlled individually or in groups using a regulator.

[0006] German patent DE 103 26 369 A1 describes a transilluminator for the quantitative or semi-quantitative evaluation of material samples. The transilluminator features manual controls that allow adjustment of the intensity of different light sources emitting different wavelengths.

[0007] Luminaires of the type mentioned above, which have white light and ultraviolet LEDs emitting both white light and ultraviolet radiation, are known from DE 10 2004 043 295 B4, EP 1 623 213 B1 and US 8,616,722 B2. They are used for visual inspection of workpiece surfaces, in particular for the detection of contaminants, for penetrant testing and for fluorescent magnetic particle testing.

[0008] US patent 2005 / 0083687 A1 describes a test lamp comprising LED groups that emit ultraviolet radiation and radiation at a visible wavelength suitable for visualizing fluorescent materials. Each LED group is assigned a push button for adjusting the radiation intensity.

[0009] In visual inspection, particularly when examining workpiece surfaces using the fluorescent penetrant method, defects on workpiece surfaces are made visible by excitation with ultraviolet radiation using a fluorescent agent. The inspection is usually carried out in the dark, at an ambient light level of less than 20 lux, because humans have higher contrast sensitivity in visual perception during meoptic (twilight vision) and scotopic (night vision), and a high contrast between the surface being examined and the excited fluorescence allows for better inspection.The problem is that when performing the inspection procedures using the known lamps, switching between white light illumination, used to inspect and assess defects found on the workpiece under ultraviolet radiation, and ultraviolet illumination results in a relatively large change in brightness to which the eyes must adjust. Since the inspection often involves frequent changes in lighting, the eyes are subjected to considerable strain.

[0010] The invention is based on the objective of creating a lamp of the type mentioned above, with which the inspection of workpiece surfaces can be carried out more effectively.

[0011] A luminaire solving this problem, as defined in claim 1, is characterized in that it is configured to simultaneously increase or decrease the intensity with which the other light source emits the radiation intensity of the first light source. a) to keep constant, wherein the luminaire has at least two control elements and one of the control elements is configured to automatically increase the radiant intensity of the other light source triggered by actuation of the first control element and to decrease it by further actuation, and the luminaire is configured such that the intensity with which one light source emits is increased with the speed during actuation of the second control element and decreased when the second control element is released, or b) to automatically decrease or increase in the opposite direction, wherein the luminaire is configured such that the intensity with which one light source emits is increased with the speed during actuation of the control element and decreased with the speed when the control element is released.

[0012] The invention makes it possible to coordinate the intensities at which the respective light sources emit light when switching from one light source to another or when moving one light source to another, in such a way that abrupt changes in intensity are avoided. Advantageously, with such coordination, the eyes can adapt better to the change in intensity, thereby achieving improved visual perception.

[0013] Sudden, potentially strong changes in intensity, such as those that occur with known lamps, especially when switching the white light on and off, particularly in low ambient light, and which are very unpleasant and tiring for the eyes and can even damage them, can be avoided.

[0014] Such changes in intensity allow, on the one hand, one light source to be added to another, and on the other hand, from one light source to another, and thus from one wavelength range of illumination to another.

[0015] It is advantageous for the intensity of at least one light source to be adjustable separately from the other light source.

[0016] In one embodiment of the invention, one of the light sources is provided for emitting visible light, preferably white light, and another of the light sources is provided for emitting ultraviolet radiation, infrared radiation and / or blue-violet light. Preferably, the radiation emitted by the light source for visible light comprises a wavelength range between 380 and 780 nm, that of the light source for ultraviolet radiation a wavelength range between 200 and 400 nm, that of the light source for infrared radiation a wavelength range between 780 nm and 50 µm, and that of the light source for blue-violet light a wavelength range between 380 and 490 nm.

[0017] In visual inspection, as explained above, ultraviolet radiation is used to detect defects or the like on the surface of a workpiece with a fluorescent agent, and under white light, possibly with simultaneous irradiation with ultraviolet radiation, the workpiece is aligned and / or defects or the like found under the ultraviolet radiation are inspected, analyzed, interpreted and / or assessed.

[0018] Advantageously, the intensity with which the respective light source emits radiation is controllable and / or adjustable over the entire power range of the light source between a minimum intensity, at which the light source preferably emits no radiation, and a maximum intensity, which is preferably adjustable and may be changed within certain limits.

[0019] It is advantageous to be able to adjust the intensity of individual or all of the light sources separately.

[0020] In a further embodiment of the invention, the lamp is arranged such that the speed at which the intensity is changed depends on the intensity with which the light source emits light.

[0021] In a particularly preferred embodiment of the invention, the luminaire is provided such that the rate of change of the intensity with which the respective light source emits is lower in intensity ranges where relatively low intensity is emitted than in intensity ranges where comparatively high intensity is emitted.

[0022] While it would be conceivable to change the rate of intensity change linearly as a function of time or proportionally to the intensity, it is preferably changed as an exponential function of the intensity.

[0023] The different rates of intensity change are used to adapt the intensity change in different brightness ranges to the eye's adaptability. This takes into account that the eye has different sensitivities to intensity changes in different intensity ranges, reacting more sensitively to changes in intensity in the dark than in bright light. Sensitivity is not linear to intensity, but is described by the Weber-Fechner law or the Stevens power function, both of which show that the eye's sensitivity is proportional to the logarithm of the radiation intensity.Accordingly, in areas of lower radiation intensity, the intensity can only be changed at relatively slow speeds without causing relatively great eye irritation, while in areas of higher radiation intensity, the intensity can be changed more quickly without being unpleasant.

[0024] In one embodiment of the invention, the light is configured to adjust the intensity at such a speed that the human eye can adapt to the change in intensity during the adjustment without or with only minimal impairment of visual perception, particularly visual acuity. This is preferably achieved in such a way that a defect detected under one type of illumination remains visible when switching the light from one light source to another. The difficulties often encountered with conventional lights, namely the ability to detect a defect found under UV illumination when illuminated with white light, are thus eliminated. Visual inspection can therefore be carried out more quickly and accurately than with known lights.

[0025] In a further embodiment of the invention, the lamp is configured to adjust the intensity in such a way that the change in intensity is perceived by the human eye as smooth, in particular without sudden changes in intensity. With such a change, the intensity change is not perceived as unpleasant and is gentle on the eyes.

[0026] Advantageously, the intensity is adjustable between 0% and 100% of a specified maximum intensity, preferably 20 to 2000 lux, such that the human eye can adapt to changes in intensity during the adjustment without impairing vision and / or that the change in intensity is perceived as smooth by the human eye. While it would be conceivable to provide such adjustability only in segments for specific intensity ranges, it is preferably provided across the entire intensity range to enable comfortable work with the light.

[0027] The maximum intensity is advantageously adjustable, preferably separately for each of the lights, so that the light can be adapted to individual needs.

[0028] According to the invention, the average rate of change in the intensity of the white light is between 5 lux / s and 500 lux / s.

[0029] The following durations are recommended for creating the intensity of the white light: Increase in intensity from 0 to 20 lux / Decrease in intensity from 20 to 0 lux: Duration > 1 - 1.5 seconds; Increase in intensity from 0 to 50 lux / Decrease in intensity from 50 to 0 lux: Duration > 1.5 - 2.5 seconds; Increase in intensity from 0 to 100 lux / Decrease in intensity from 100 to 0 lux: Duration > 2 - 3 seconds; Increase in intensity from 0 to > 100 lux / Decrease in intensity from > 100 lux to 0 lux: Duration > 2.5 seconds

[0030] Within the aforementioned speed ranges, the light can be used at sufficiently high speeds; however, excessive eye fatigue is avoided, vision is not impaired when the intensity changes, and the intensity changes are perceived as smooth.

[0031] To make the adaptation of the eye to white light as comfortable as possible when adjusting the white light source from a switched-off state in which the light source does not emit light, the luminaire is expediently designed so that the white light source can be adjusted to intensities that are < 1%, preferably < 0.5%, particularly preferably < 0.1% of a maximum intensity provided for the white light.

[0032] In a particularly preferred embodiment of the invention, the light source for white light can be adjusted from the switched-off state in steps that are < 1 lux, preferably < 0.5 lux.

[0033] The light can be set up in such a way that, of the two latter setting options, i.e., the percentage dependence on the maximum intensity and the steps in 1 or 0.5 lux, it selects the one that der Smaller steps can be taken.

[0034] Preferably, the light is designed in such a way that the speed or speeds of the intensity change, preferably within certain limits, can be changed in order to be individually adjusted.

[0035] Advantageously, at least one of the light sources is formed by a discharge lamp and / or by at least one light-emitting semiconductor diode (LED), wherein the light source(s) is preferably provided with a filter for adjusting the respective wavelength range.

[0036] Advantageously, the luminaire has a control and / or regulation unit for adjusting the intensity. The control and / or regulation unit preferably includes at least one constant current controller that operates on the basis of electrical and electronic switching and control circuits. This allows the luminaires, especially the LEDs, to be operated particularly efficiently because the constant current controller measures the operating current of the respective light source, especially the LED or the LED circuit, and keeps it constant within narrow limits. Advantageously, the constant current controller can generate the constant current from an alternating and / or direct current voltage.

[0037] The intensity of the LED is preferably changed using pulse-width modulation. The luminaire preferably incorporates a pulse-width modulation control for this purpose.

[0038] Furthermore, the control and / or regulating device may include a control mechanism that can reduce or switch off the power of the luminaire or individual parts of the luminaire depending on the temperature, in order to protect the luminaire, in particular the light source and / or the control and / or regulating unit, from overheating. For cooling, the luminaire could additionally or alternatively be equipped with a fan, which is preferably controllable and / or regulating by means of the control and / or regulating device.

[0039] The light is expediently designed such that the intensity of the white light emitting light source is increased while the control element is activated and decreased when the control element is released.

[0040] Alternatively, it could be provided that the intensity of the white light source is automatically increased to the intended maximum intensity when the control element is activated, and that after reaching the maximum intensity, the intensity is automatically reduced again or by reactivating the control element, preferably to a predetermined minimum value at which preferably no radiation is emitted.

[0041] Advantageously, the lamp is configured to indicate the operating status of at least one of the light sources. The operating status preferably includes the intensity with which the light source emits radiation and / or the duration during which the light source emits radiation, preferably at a predetermined intensity. Indicating the duration is particularly useful for ensuring that, during the aforementioned inspection of the workpiece surfaces, predetermined time periods are observed to allow the eye to adapt to specific intensities.

[0042] Alternatively or additionally, the luminaire can indicate whether the respective light source is emitting radiation or not, i.e., in particular whether it is switched on or off, and for how long it has been in the respective operating state. Advantageously, it can also indicate whether sufficient time has elapsed after reaching the respective operating state for the eyes to adapt to the respective intensity. Preferably, the luminaire includes the standard values ​​for eye adaptation times for the respective operating states.

[0043] In one embodiment of the invention, the lamp according to the invention is used as follows. First, preferably in darkness or very low ambient light, the UV-emitting lamp is switched on. The intensity of the emitted radiation is then preferably increased to a predetermined target intensity at one of the rates of intensity change described above. However, it can also be set abruptly to the target intensity, since sudden changes in illumination resulting from the UV radiation are less unpleasant for the eye. A workpiece surface can then be examined under UV radiation. To inspect the workpiece surface under visible light as well, the lamp provided for the emission of white light is switched on and the intensity is increased to a predetermined target intensity, preferably at one of the rates described above.Optionally, the UV lamp can be switched off when a certain intensity of the white light lamp is reached or during an increase in intensity, or the intensity can be reduced, preferably at one of the rates described above. Advantageously, for further examination under UV radiation, the UV lamp is then switched on again and the intensity of the UV lamp's radiation is increased, preferably at one of the rates described above. Subsequently or simultaneously, the intensity of the white light lamp is increased again, preferably as described above, to a predetermined target intensity at which the workpiece surface is to be inspected with visible light.

[0044] It is understood that the light fixture is designed to automatically perform the above-described changes in the intensity of the respective light sources, possibly in response to a command entered via a control element.

[0045] In one embodiment of the invention, the luminaire has a monitoring device designed to detect an operational fault, in particular a defect in one of the light sources or other components of the luminaire, and preferably designed to shut down the luminaire when an operational fault is detected. The monitoring device may also be designed to display the operational fault.

[0046] In a further embodiment of the invention, the lamp comprises an adjustment device designed to regulate the intensity of the radiation emitted by the respective light source as a function of the device's temperature. Advantageously, this compensates for a reduction in intensity that occurs with increasing temperature.

[0047] Advantageously, the size of the area that can be illuminated by the light is adjustable. Preferably, a first setting is provided in which a relatively small area can be illuminated and which serves for focused viewing, and a further setting with which a larger area can be illuminated.

[0048] The luminaire expediently comprises at least one housing, preferably designed to accommodate the light source, at least one control element, at least one optical system, preferably comprising at least one lens, and / or at least one coolant, preferably a fan, a heat exchanger and / or a cooling plate.

[0049] In one embodiment of the invention, the lamp can be used in mobile and / or stationary applications. It can be a handheld and / or floor lamp, or a lamp that can be permanently installed, for example, on a bracket or a wall.

[0050] While in a particularly preferred embodiment of the invention a device for operating the lamp is integrated into the housing, it would also be conceivable to provide it outside the housing, wherein the lamp preferably comprises at least one housing for the light sources, at least one control cabinet or switch housing, and / or at least one operating element. Advantageously, the operating device has at least one control element that can be operated by hand or foot, by means of which the intensity of at least one of the light sources can be changed.

[0051] The control element, which is preferably formed by a push button or a rotary control, is expediently used to switch the respective light sources on or off or to control and / or regulate the intensities with which the respective light sources emit light.

[0052] The light can be powered by at least one external or integrated DC and / or AC power source.

[0053] The term "luminaire" should also include a lighting system.

[0054] The invention is explained in more detail below with reference to an exemplary embodiment and the accompanying drawings relating to that embodiment. The drawings show: Fig. 1 shows a side section of a lamp according to the invention, Fig. 2 shows a front view of the lamp according to the invention. Fig. 1 , Fig. 3 a rear view of the lamp according to Fig. 1 , and Figs. 4 to 6 are diagrams explaining the invention.

[0055] One in the Figuren 1 bis 3 The illustrated luminaire 1 according to the invention comprises eight UV LEDs 2, which are provided for the emission of UV radiation (wavelength range 200–400 nm), and eight white light LEDs 3, which are provided for the emission of white light (wavelength range 380–780 nm). Optical components 4, 5 are arranged in front of the LEDs 2, 3 to influence the respective beam paths emanating from the LEDs. A front lens 7 is arranged behind the optical components 4, 5 in the direction of radiation. This lens is connected to a housing 9 of the luminaire 1 via fastening means 10 and is provided with filters 8 for each of the UV LEDs 2.

[0056] The LEDs 2 and 3 are soldered onto a carrier board 6, which is mounted on a heat sink 11. The heat sink 11 is connected via standoffs 12 to a circuit board 13, which carries several electronic components. A display LED 14 is also mounted on the circuit board 13. As explained in more detail below, this LED is intended to indicate the operating status of the luminaire 1. A light guide 15 is arranged between the rear side of the housing 9 and the display LED 14, through which light from the display LED 14 can be directed to the rear side.

[0057] The electronic components form a control and / or regulation device 26, which is designed to control and / or regulate the intensities with which the LEDs 2,3 emit light.

[0058] The electronic components also form a monitoring device 27, which is designed to detect faults during the operation of the luminaires 1. The monitoring device 27 is configured to shut down the luminaire 1 upon detecting an operational fault, for example, if one of the LEDs 2 or 3 fails. Furthermore, it can be designed to characterize the operational fault, for example, by displaying a code via the indicator LED or another indicator device.

[0059] Furthermore, an adjustment device 28 is formed on the circuit board 13 by the electronic components, which is intended to regulate the power with which the LEDs 2,3 emit light depending on the temperature of the lamp 1, in order to compensate for changes in current that occur when the lamp 1 heats up, in order to regulate the respective intensities to the intended values.

[0060] A fan 16 is provided for cooling the lamp, by means of which air can be blown onto the circuit board 13 and the heat sink 11. The housing 9 is provided on its rear with a ventilation grille 17, which is designed to hold a filter and through which air is drawn in by the fan 16.

[0061] The light fixture 1 also has a handle 18, at the lower end of which a cable 20 is routed via a strain relief 19, through which the light fixture 1 can be supplied with energy and, if necessary, controlled.

[0062] How especially Fig. 3 As can be seen, the luminaire 1 is equipped on its back with pushbuttons 21, 22, 23, 24 and a rotary control 25, which are intended for controlling intensities with which the LEDs 2, 3 light up and which interact with the control and / or regulating device 26.

[0063] The control and regulating device 26 is designed to change the intensities with which the UV LEDs 2 and the white light LEDs 3 emit light separately from each other by means of pulse width modulation.

[0064] The control and regulating device 26 changes the intensities at such a speed that the human eye can adapt to the changing intensity without or with only minimal impairment of visual perception, in particular visual acuity, so that a detected defect can be monitored during the change in intensity. Furthermore, the intensities are changed in such a way that the human eye perceives the change in intensity smoothly, i.e., without sudden jumps in intensity.To facilitate a transition from UV to white light illumination with minimal eye strain and to ensure the fastest possible changeover, the control unit 26 is programmed to adjust the intensity relatively slowly at low intensities and more rapidly at higher intensities, corresponding to the adaptability of the human eye. The rate at which the intensity changes can be proportional or exponential to the intensity, or linear with time.

[0065] By pressing buttons 21, 22, 23, 24, the control and regulating device 26 is caused to change the intensities of the UV LEDs and the white light LEDs 3 as shown below. Figuren 4 bis 6 explained, the diagrams show the time course of the intensities of the UV LEDs 2 (Y-axis I UV plotted on the left) and the white light LEDs 3 (Y-axis IW plotted on the right). Example 1 (see Fig. 4):

[0066] At time t 1, the button 21 is pressed, thereby switching on the UV-LED 2, which then shines with a target intensity I MAX, under which a workpiece can be examined.

[0067] At time t2, pressing one of the buttons 22 switches the light from UV LED 2 to white LED 3. This means the intensity of the white LED 3 is increased to a target intensity IMAX, as explained above, while simultaneously reducing the intensity of the UV LED 2 until it is no longer emitting light. At time t3, the target intensity IMAX of the white LED 3 is reached, and the intensity of the UV LED is reduced to zero. The workpiece can now be inspected under white light.

[0068] If a further examination is to be carried out under UV illumination, the button 22 is released again and the light is switched to illumination by the UV LED 2 (time points t 4 and t 5). By pressing the button 22 again, the light can be switched back to white light (time points t 6 and t 7).

[0069] When the light is switched back to UV light, button 22 is released again (time points t 8 and t 9 ).

[0070] To switch off the UV LED 2, the button 21 is pressed again.

[0071] It goes without saying that the UV LED 2 and white light LED 3 can be switched back and forth as often as desired for examining the workpiece.

[0072] It can be provided that a crossover to radiation using only white light is carried out only as long as one of the buttons 22 is pressed and, conversely, when one of the buttons 22 is released, the intensity of the white light LED 3 is reduced again and that of the UV LED is increased to the target intensity.

[0073] Advantageously, a specific area on the workpiece, such as a defect, viewed under ultraviolet or white light, can remain in view even during crossfading. In both directions of transition, i.e., from white light to ultraviolet radiation and vice versa, the respective intensity changes are perceived as a film. Because the intensity changes occur at speeds that allow the eyes to adapt, visual perception, especially visual acuity, is not affected or only minimally impaired.

[0074] As in Fig. 4a As shown, the intensities of UV LED 2 and white light LED 3 can be adjusted so that the intensities change more quickly at higher intensities than at lower intensities. As explained above, this allows the human eye to adapt better to the changing intensities.

[0075] However, it would also be conceivable to adjust the intensities, as in Fig. 4b shown to change linearly depending on time.

[0076] It goes without saying that the different intensity levels could also be combined. For example, the intensity of the white light LED 3 could be changed depending on the intensity level, while the intensity of the UV LED 2 could be changed proportionally to time. Example 2 (Figure 5)

[0077] At time t1, pressing button 21 switches on the UV LED 2 and sets its intensity to the target intensity I MAX. Pressing one of the buttons 23 (at time t2) activates the white light LED 3 in addition to the UV LED 2. The intensity of the white light LED is gradually increased to a target value I MAX, as described above, until it reaches this value at time t3, at which point the intensity of the UV LED 2 remains constant. Similarly, the intensity of the white light LED 3 increases or remains constant at I MAX only as long as button 23 is held down. Releasing button 23 (at time t4) reduces the intensity of the white light LED 3 until it is no longer illuminated at time t5.If necessary, the white light LED 3 can then be switched back on with the UV LED 2 (time points t 6 to t 8 and t 10). Once the examination of the workpiece is complete, the UV LED is switched off by pressing button 21 (time points t 9 and t 11).

[0078] As shown above, based on the Fig. 5 As explained, the white light LED 3 can also be changed at different speeds in this example, depending on the respective intensity ( Fig. 5a ) or the intensity is carried out in a linear dependence on time ( Fig. 5b ). Example 3 (Figure 6)

[0079] How Fig. 6 As shown, the UV LED could also be switched off after switching on the white light LED 3 (time points t 4 and t 5) and switched back on with the white light if necessary (time points t 6 and t 7) to view the workpiece under UV radiation, the intensity of the white light LEDs 3 is then reduced again (time points t 8 and t 9).

[0080] Furthermore, Fig. 6 It can be seen that even when the UV-LED 2 is switched on, the intensity can be gradually increased to the target value I MAX, e.g. with one of the speeds described above.

[0081] The push button 24 is designed to maintain the respective intensities of the UV LED 2 and the white light LED 3, i.e., to prevent a change in the illumination state achieved with the luminaire 1. For example, by pressing the push button 24, the luminaire 1 can be set to remain in the state at time t 3 after Fig. 4 a or in the state after time t 3 after Fig. 5acan be held without having to press and hold button 22 or button 23.

[0082] The rotary control 25 is intended to change the target intensity with which the white light LED 3 emits within certain predetermined limits and to adjust it for use with the light 1.

Claims

1. Luminaire, in particular for testing workpiece surfaces, which comprises at least one operating element (21, 22, 23, 24) and at least two illuminants (2, 3) which emit electromagnetic radiation in different wavelength ranges, wherein an intensity with which the illuminant (2, 3) radiates is automatically adjustable for at least one of the illuminants (2, 3), wherein a speed at which the intensity is changed is between 5 lux / s and 500 lux / s, wherein the luminaire (1) is configured, at the same time as the increase or reduction of the radiation intensity of said one illuminant (2, 3), a) to keep constant the intensity with which the other illuminant (2, 3) radiates, wherein the luminaire (1) comprises at least two operating elements (21, 23) and one of the operating elements (21) is configured automatically to increase the radiation intensity of the other illuminant (2, 3) up to a maximum intensity provided, in a manner triggered by actuation of said one operating element (21), and to reduce it by renewed actuation, and the luminaire (1) is configured in such a way that the intensity with which said one illuminant (2, 3) radiates is increased at the speed during an actuation of the other operating element (23) and is reduced at the speed upon release of the other operating element (23), or b) to automatically oppositely reduce or increase the intensity with which the other illuminant (2, 3) radiates, wherein the luminaire (1) is configured in such a way that the intensity with which said one illuminant (2, 3) radiates is increased at the speed during an actuation of the operating element (22) and is reduced at the speed upon release of the operating element (22).

2. Luminaire according to Claim 1, characterized in that the luminaire (1) is configured in such a way that a speed at which the intensity is adjusted is dependent on the intensity with which the respective illuminant (2, 3) radiates, wherein preferably at comparatively low intensity the speed is lower than at comparatively high intensity.

3. Luminaire according to Claim 1 or 2, characterized in that the luminaire (1) is configured for adjusting the intensity at a speed such that the human eye can adapt to a change in the intensity during the adjustment without impairment of visual perception.

4. Luminaire according to any of Claims 1 to 3, characterized in that the luminaire (1) is configured for adjusting the intensity in such a way that the change in the intensity is perceived by the human eye as uniform, in particular without intensity jumps.

5. Luminaire according to any of Claims 1 to 4, characterized in that one of the illuminants (2) is provided for emitting visible light, preferably white light, and another of the illuminants (3) is provided for emitting ultraviolet radiation, infrared radiation and / or blue-violet light.

6. Luminaire according to any of Claims 1 to 5, characterized by a control and / or regulation device (26) for adjusting the intensities.

7. Luminaire according to any of Claims 1 to 6, characterized in that the luminaire (1) is configured for indicating an operating state of at least one of the illuminants (2, 3).

8. Luminaire according to any of Claims 1 to 7, characterized in that the operating state comprises the intensity with which the illuminant (2, 3) emits the radiation, and / or an emission duration, preferably an emission duration at a predetermined intensity.

9. Luminaire according to any of Claims 1 to 8, characterized by at least one operating device, preferably a hand- and / or foot-operated switch and / or regulator (21, 22, 23, 24, 25), for changing the intensity.

10. Luminaire according to any of Claims 1 to 9, characterized by a monitoring device that is configured for identifying an operational fault, in particular a defect of one of the illuminants (2, 3) or of other components of the luminaire (1), and preferably for indicating the operational fault and / or is provided for deactivating the luminaire (1) upon finding an operational fault.

11. Method for operating a luminaire (1), in particular for testing workpiece surfaces, in particular using a fluorescent marking medium, said luminaire comprising at least two illuminants (2, 3) which emit electromagnetic radiation in different wavelength ranges, wherein an intensity with which the illuminant (2, 3) radiates is adjusted for at least one of the illuminants (2, 3) by means of an operating element (21, 22, 23, 24), wherein the speed at which the intensity is changed is between 5 lux / s and 500 lux / s, wherein, at the same time as the increase or reduction of the radiation intensity of said one illuminant, the intensity with which the other illuminant (2, 3) radiates a) is kept constant, wherein the luminaire (1) comprises at least two operating elements (21, 23) and the radiation intensity of the other illuminant (2, 3) is automatically increased up to a maximum intensity provided, in a manner triggered by actuation of said one operating element (21), and is reduced by renewed actuation, and the intensity of said one illuminant (2, 3) is increased at the speed during an actuation of the other operating element (23) and is reduced at the speed upon release of the other operating element (23), or b) is automatically oppositely reduced or increased, wherein the intensity of said one illuminant (2, 3) is increased at the speed during an actuation of the operating element (22) and is reduced at the speed upon release of the operating element (22).

12. Method according to Claim 11, characterized in that the intensity is adjusted at a speed such that the human eye can adapt to a change in the intensity during the adjustment without impairment of vision.

13. Method according to Claim 11 or 12, characterized in that the luminaire (1) comprises an operating element (21, 22, 23, 24), and in that the intensity with which one of the illuminants (2, 3) radiates, preferably the illuminant (2, 3) that emits white light, is increased or reduced by the actuation of the operating element (21, 22, 23, 24) and the intensity with which the other illuminant (2, 3) radiates is at the same time kept constant or reduced or increased oppositely to the respectively first illuminant (2, 3).