Method for emulating an optical emitter

Description

[0001] The invention relates to a method for emulating an optical emitter. background

[0002] In connection with security documents, such as identification documents or banknotes, provision may be made for optical security features. For example, chromophores or dyes can be integrated into the security document that emit and / or absorb light upon excitation, thereby exhibiting a characteristic optical behavior suitable for forming a security feature. In this context, for example, special pigments or phosphor preparations can be provided that exhibit a defined optical behavior upon optical irradiation or excitation in another way, for example with regard to the wavelength and / or frequency of emitted light.

[0003] The radiation emitted in response to the excitation can also assume a signal curve independent of the direct excitation, meaning that it is not necessary to assume a proportional relationship between the excitation and the radiation emitted in response. Thus, depending on the materials used, different constants for the rise (intensity) and decay of a light emission can result.

[0004] The materials used to create optical security features are subject to safety-related restrictions, particularly regarding their availability. Therefore, studies of the optical behavior of such materials can be costly, if the materials are even available for such studies.

[0005] The document DE 10 2011 053 902 A1 discloses a method for operating a light-emitting device, wherein in the method a pulsed current with a pulse frequency is generated by a driver circuit which has a clock generator providing clock signals for current pulsing, and a light-emitting device which is functionally coupled to the driver circuit and which is formed with one or more organic light-emitting diodes is subjected to the pulsed current.

[0006] Document US 2016 / 0 007 430 A1 discloses a remote-controlled Christmas lighting and sound system that provides a remote-controlled and decorated control module integrated into a holiday symbol, such as a Christmas tree, to control a Christmas lighting pattern and audio recording for a plurality of light strings and a speaker. Summary

[0007] The object of the invention is to provide a method for emulating an optical emitter, which enables characterization and investigation of optically active emitters for a wide variety of applications.

[0008] To achieve this, a method for emulating an optical emitter is provided according to independent claim 1. Embodiments are the subject of dependent subclaims.

[0009] In an example not belonging to the present invention, an apparatus for emulating an optical emitter is provided with a light-emitting device having a light-emitting element. The optical emitter, upon receiving excitation energy, emits at least one light pulse, wherein the at least one light pulse for the optical emitter is characterized, depending on the excitation energy, by at least the parameters color, rise time constant, and decay time constant. The apparatus can have an input device configured to receive an input specifying at least one pulse characteristic for a light pulse to be generated, wherein the at least one pulse characteristic corresponds to a parameter for the optical emitter from the following group: rise time constant, decay time constant, and color, or wavelength, for the light pulse, based on the predetermined substance.Furthermore, an electrical driver circuit may be provided, which is connected to the input device and the light-emitting device and configured to generate control signals in response to the at least one pulse characteristic and to output them to the light-emitting device. The light-emitting device may be configured to emit the light pulse with the at least one pulse characteristic in response to the control signals using the light-emitting element.

[0010] The exemplary device can be provided to emulate an optical emitter that, in response to receiving, in particular by absorption, an excitation energy, an electromagnetic radiation having an excitation waveform, emits radiation that can be detected and measured. The measurable and then known radiation (light pulse(s)) is determined at least by color or wavelength as well as the rise time constant and decay time constant. The excitation waveform can be, for example, a light pulse or an electric field. The electromagnetic radiation emitted in response thereto can be, for example, without limitation, fluorescent radiation.

[0011] The term "excitation waveform," as used here, refers specifically to the temporal profile of an excitation of the optical emitter with electromagnetic energy, its wavelength, and the duration of the exposure. Exposure to other forms of excitation is also considered, such as thermal, electrical, or mechanical fields or forces.

[0012] The proposed technology makes it possible to emulate the behavior of optical emitters, providing a substitute for experimental investigations and studies on materials that form optical emitters. These investigations can be carried out without actually having optical emitter material available and thus without consuming it.

[0013] It is therefore understood that the (actual) presence of the optical emitter is not required to practice the teaching. Rather, its actual presence can be replaced by knowledge of its response, in the form of electromagnetic radiation in the optical range, to the reception of excitation energy in a predetermined excitation waveform.

[0014] The electrical driver circuit generates the control signals in response to the at least one characteristic received via the input device, for example, as part of a user input. The characteristic can be received as such via the input device, for example, a numerical value with a dimension, such as a rise time constant in seconds. Alternatively, a parameter can be received via the input device, for which the associated characteristic is then determined for the parameter value using the input device and / or a data processing device connected thereto.

[0015] The input device can be formed together with the electrical control circuit and / or the light emitting device, or separately therefrom.

[0016] The light-emitting device can be configured to emit single-color light pulses. The light-emitting device can be configured, using one or more optical emitters, to generate and emit light pulses with only one wavelength or light pulses of different wavelengths according to the control signals. In this or other embodiments, the light-emitting element can be formed with a light-emitting diode, an organic light-emitting diode, a laser, and / or a discharge lamp. For example, an arrangement with multiple diodes can be provided, each configured to emit light of different colors.

[0017] The group of parameters can further comprise at least one of the following parameters: temporal spacing of light pulses in a pulse train, intensity of the light pulse, temporal pulse width, symmetrical pulse shape, and asymmetrical pulse shape. If a sequence of light pulses is provided, the light pulses can each be generated with the same parameters or with different parameters, for example with different intensities, different time constants, different temporal spacings, and / or different light colors. The pulse shape of the light pulses can correspond to a Gaussian or Lorentz curve or be approximated to one in spectral and / or temporal terms. An asymmetrical pulse shape on the time axis can mean, in particular, that the rise time constant and the decay time constant for the light pulse differ.

[0018] In various embodiments, the pulse rise time constant may indicate the time period between 10% and 90% of the amplitude of the light pulse. Similarly, the decay time constant may indicate the period for the amplitude of the light pulse to decay from 90% to 10%.

[0019] The light emitting device may be configured to emit light pulses in at least one of the following spectral ranges: about 500nm to about 700nm and about 800 to about 1100nm.

[0020] The electrical driver circuit may be configured to generate control signals such that the light pulse has a rise time constant between about 10ps and about 10ms, preferably between about 1µs and about 1000µs.

[0021] The electrical driver circuit may be configured to generate control signals such that the light pulse has a decay time constant between approximately 10ps and approximately 10ms, preferably between approximately 1µs and approximately 1000µs.

[0022] The input device can be configured to receive, in response to a user input that specifies or indicates an optical emitter, at least one characteristic from a database in which one or more associated characteristics are stored for each optical emitter. In this embodiment, it can be provided that the user input specifies a name or a parameter of the optical emitter, for which the at least one characteristic is then retrieved from the database. For this purpose, the user input can be transmitted to the database, where one or more characteristics are stored for the optical emitter identified based on the user input.The database returns the at least one characteristic value to the input device and from there to the electrical driver circuit or directly to the electrical driver circuit, whereupon the control signals can be generated which control the light emitting device in such a way that the light pulse with the at least one characteristic value is generated.

[0023] The light-emitting device can have a plurality of light-emitting elements configured to emit identical or different light pulses independently of one another. In this way, for example, the light-emitting device can be provided with a plurality of optical channels, each emitting light pulses randomly or in a coordinated manner, whether with identical or different characteristics, for example, with regard to the light color. In this way, for example, mixed light emulation can be implemented. Thus, an optical emitter can be emulated that emits light of different colors simultaneously or at different times.

[0024] It can be provided that the input device is configured to receive a usage parameter indicating a usage condition, and that the electrical driver circuit is configured to generate the control signals such that the light emitting device, in response to the control signals, emits the light pulse with at least one pulse characteristic changed according to the usage conditions by means of the light emitting element.

[0025] Based on the received information about one or more usage conditions, the at least one pulse characteristic according to which the light pulse is generated by means of the electrical driver circuit and the light-emitting device is modified such that the modified pulse characteristic leads to the generation (emulation) of a light pulse that is different from a light pulse for which the usage condition is not taken into account, i.e., an optical emitter that is unaffected by usage conditions. This makes it possible to consider various aspects of the use of the optical emitter during emulation with the aid of the device.

[0026] The conditions of use may, for example, include wear or aging of the optical emitter (emitter material). If, for example, optical emitters are used in security documents to provide security features, these optical emitters are subject to wear or aging processes over the course of the security document's use. This changes the light emission (e.g., fluorescence) that is received and evaluated when such a security feature is checked. To emulate such aging processes, information about pulse characteristics relating to an optical emitter can be provided in a database, for example, indicating different light pulses depending on the age of the emitter material. These (age-dependent) pulse characteristics can then be taken into account during emulation, for example, in response to a user input that indicates a predetermined aging.Regarding aging or wear, different pulse parameters can be stored for different service lives.

[0027] Another usage condition, for example, concerns the emulation of the behavior of the optical emitter under different environmental conditions. This includes, for example, the emission of different light pulses by the optical emitter at different temperatures. When using optical emitters in security documents, a cover surface of the area in which the emitter is located may be dirty or worn, so that the light emission received from the outside when checking a security feature is altered due to these usage conditions. The emulated light emission can also be adapted for such usage situations, for example, by storing pulse parameters for different degrees of contamination in the database.

[0028] Another category of usage conditions concerns influencing variables for the light emitted by an optical emitter on the one hand and the measurement light received during a measurement on the other, for example, when determining and evaluating an optical security feature of a security document. The actually measured light may differ from the light emitted by the optical emitter due to specific usage conditions, such as back reflections, stray light, and / or scattered light. Such usage conditions can also be taken into account during emulation, for example, by storing different pulse parameters for the optical emitter that indicate a graduated influence of back reflections, for example, by the light intensity of the light pulse gradually decreasing.

[0029] In connection with the method for emulating an optical emitter, the examples explained above in connection with the variants of the device apply accordingly. Description of implementation examples

[0030] In the following, further embodiments are explained in more detail with reference to a figure.

[0031] The single figure shows a schematic representation of a device for emulating an optical emitter with a light-emitting device 1, which in the embodiment shown has several light-emitting elements 2.1, ..., 2.4. Optical emitters are materials or elements that emit light upon receiving excitation energy, for example, by irradiating electromagnetic radiation.

[0032] The light-emitting elements 2.1, ..., 2.4 are each formed, for example, with a light-emitting diode, an organic light-emitting diode, a laser, and / or a discharge lamp, whereby a combination of different such light-emitting elements can be provided. The light-emitting device 1 is thereby configured to generate and emit single-color light of different wavelengths and / or mixed light in the form of light pulses. The emitted light can be detected or measured using an optical detection device (not shown), for example, with a spectrometer. To evaluate the detected light pulses, an analysis in the frequency domain (spectral analysis) and / or the time domain (time-resolved analysis) can be provided. Suitable analysis devices for this purpose are known in various embodiments.

[0033] To control the light-emitting device 1 to emit one or more light pulses of the same or different colors, an electrical driver circuit 3, constructed using hardware and software components, is coupled to the light-emitting device 1. Using the electrical driver circuit 3, control signals are generated that control one or more of the light-emitting elements 2.1, ..., 2.4 to emit light. The electrical driver circuit 3 is configured to generate control signals or pulses such that light pulses with defined parameters are emitted by the light-emitting device 1, wherein the parameters can be adjusted using the control signals.For example, the control signals are generated by means of the electrical driver circuit 3 such that a light pulse emitted by the light emitting device 1 has a defined rise time constant and / or a defined decay time constant, wherein the time constant can indicate the period between 10% and 90% of the pulse height or amplitude of the light pulse during rise / decay.

[0034] The hardware / software configuration of the electrical driver circuit 3 makes it possible to provide control signals for a wide variety of light pulses in order to emulate the emission behavior of different optical emitters, be it in spectral terms (color) and / or in temporal terms, for example with regard to the pulse rise, the pulse width and / or the pulse decay.

[0035] According to the figure, an input device 4 is also provided, which is connected to the electrical driver circuit 3 (and optionally to the light-emitting device 1). Inputs 5 are received via the input device 3, for example, a user input, for example via a keyboard or a touchscreen, which are used to specify at least one characteristic value for a light pulse to be generated by the light-emitting device 1, for example, a rise time constant and / or a decay time constant for the light pulse to be generated.

[0036] In this case, the recorded input can directly specify or name the at least one characteristic, for example, a time constant (for example, time in seconds). Alternatively, it can be provided that the input does not directly indicate the characteristic; for example, a name or a parameter can be entered, for which one or more characteristics for the light pulse to be generated are then retrieved from the database 6 by accessing a database 6.A collection of characteristics for different optical emitters can be provided in the database 6, so that a user enters an identifier for an optical emitter, for example via the input device 4, whereupon one or more characteristics are retrieved from the database 6 for the optical emitter identified thereby, in order to subsequently generate the control signals necessary for generating a light pulse with the characteristic(s) by means of the electrical driver circuit 3 and then transfer them from the electrical driver circuit 3 to the light emitting device 1.

[0037] Optical emitters, i.e., materials that emit electromagnetic radiation in the optical range in response to receiving excitation energy, are known as such in a wide variety of forms. Such optical emitters can emit or emit light in just one or in multiple wavelength ranges. In these cases, the optical emitter is also referred to as having different spectral emission bands. The emission band in which light is emitted in response to excitation can depend on the type of excitation energy and / or the excitation energy transfer within the emitter. For example, materials are known that emit light of different colors depending on the color of the excitation light.If, for example, excitation of the emission is intended by means of optical radiation, this must usually lie in a spectral range in which the optical emitter itself has a so-called absorption band (spectral band in which the optical emitter absorbs) in order to absorb the excitation energy.

[0038] Using the proposed technology, the emission behavior of a wide variety of optical emitters can be emulated, particularly with regard to the spectral characteristics and / or the temporal characteristics.

[0039] The features disclosed in the above description, the claims and the drawings may be important for the realization of the various embodiments both individually and in any combination, provided that they fall within the scope of the appended claims. List of reference symbols

[0040] 1Light-emitting device 2.1,..., 2.4Light-emitting elements 3Electrical driver circuit 4Input device 5Input 6Database

Claims

1. A method for emulating an optical emitter, which, in response to receiving excitation energy corresponding to an electromagnetic radiation with an excitation waveform, emits at least one measurable and therefore known light pulse, wherein - the at least one light pulse of the optical emitter, depending on the excitation energy, is characterized at least by the characteristic variables of colour, rise time constant and decay time constant, and - emulation of the optical emitter comprises the following: - providing a light emission device comprising a light-emitting element; - receiving an input by means of an input device, wherein - the input specifies at least one pulse characteristic for a light pulse to be generated, which substitutes the actual presence of the at least one measurable and therefore known light pulse from the optical emitter to be emulated and - the at least one pulse characteristic is one from the following group: rise time constant, decay time constant and colour for the light pulse that the optical emitter to be emulated emits in response to receiving electromagnetic radiation; wherein the input device, in response to a user input specifying the optical emitter, receives the at least one pulse characteristic from a database in which one or more associated pulse characteristics are respectively stored for optical emitters; - generating control signals in response to the at least one pulse characteristic by means of an electronic driver circuit that is connected to the input device and the light emission device; - transmitting the control signals to the light emission device; and - emitting the light pulse to be generated, with the at least one pulse characteristic, via the light emission device in response to the control signals with the help of the light-emitting element.

2. The method according to claim 1, characterized in that the light emission device emits monochromatic light pulses.

3. The method according to claim 1 or 2, characterized in that the group of characteristic variables further comprises the following characteristic variables for the optical emitter to be emulated: time interval between light pulses in a pulse sequence, intensity of the light pulse, temporal pulse width, symmetrical pulse shape and asymmetric pulse shape.

4. The method according to any one of the preceding claims, characterized in that the light emission device emits light pulses in at least one of the following spectral ranges: approximately 500 nm to approximately 700 nm and approximately 800 nm to approximately 1100 nm.

5. The method according to any one of the preceding claims, characterized in that the electrical driver circuit generates control signals in such a manner that the light pulse has a rise time constant between approximately 10 ps and approximately 10 ms, preferably between approximately 1 µs and approximately 1000 µs.

6. The method according to at least one of the preceding claims, characterized in that the electrical driver circuit generates control signals in such a manner that the light pulse has a decay time constant between approximately 10 ps and approximately 10 ms, preferably between approximately 1 µs and approximately 1000 µs.

7. The method according to at least one of the preceding claims, characterized in that the light emission device comprises multiple light-emitting elements, which emit identical or different light pulses independently of one another.

8. The method according to any one of the preceding claims, characterized in that - the input device receives a usage characteristic indicating a usage condition and - the electronic driver circuit generates the control signals in such a manner that the light emission device, in response to the control signals, emits the light pulse with the help of the light-emitting element with at least one pulse characteristic modified in accordance with the usage conditions.