Determining the degree of hair stretch using a NIR sensor

Description

[0001] The invention relates to an arrangement for determining a degree of elongation of hair, a method for determining the degree of elongation of hair, and a computer program product which is designed to carry out the steps of such a method when executed on a corresponding arrangement.

[0002] When treating hair with cosmetic products, the effect of the product, e.g. the intensity of a color, can depend heavily on damage to the hair.

[0003] Hair can be damaged by natural or artificial processes. Both external and internal damage to the hair can be relevant to the effectiveness of a product. In general, hair can be damaged due to chemical or physical processes or due to mechanical influences.

[0004] Natural processes can, for example, involve a combined (e.g., simultaneous) exposure of the hair to UV light and oxygen (O 2 ). Artificially induced processes can include, for example, the application of hair dyes (also known as coloring), bleaching, and / or perming.

[0005] In addition to desired cosmetic effects, such as lightening the hair, severe damage to the hair can also occur, for example when using oxidizing agents.

[0006] The resulting type of damage is called oxidative damage and is caused by the use of colorants, bleaching, perming, and environmental influences (UV + O2). This damage is caused by the oxidation of the amino acids cystine and cysteine, which are very common in hair, to cysteic acid.

[0007] Cystine can form intermolecular disulfide bridges (also called SS bridges) in hair, so cystine is extremely important for the mechanical stability of hair.

[0008] The oxidation of these bridges to cysteic acid can destroy the mechanical stability of the hair and, with repeated applications, even lead to complete hair breakage. However, macroscopically perceptible, tactile, properties of the hair, such as surface roughness, can also be negatively affected. Even at an early stage of damage, the results of cosmetic treatments, especially damaging procedures, can be significantly altered compared to the results of undamaged hair.

[0009] In addition to this oxidative damage, reductive damage to hair is also possible. This occurs with cosmetic procedures that use reducing agents. These include, for example, permanent waves or straighteners, which contain reducing agents such as thioglycolic acid or sulfite. These ingredients serve to open the disulfide bonds of cysteine, thereby transforming the hair. The following sulfur species are formed: RSH (thiols), RS-SO 3 -, (colored salts, after sulfite treatment), RSS-CH2COO -< (disulfides with thiglycolate units, after thioglycolate treatment).

[0010] Furthermore, as a mostly mechanical damage, the degree of stretching of hair is a relevant parameter, especially in the case of irreversible overstretching (i.e. an overstretching which exceeds 10% of the unstretched length, measured for example at a relative humidity of a hair sample of 45%), in order to be able to estimate the effect of care and / or treatment products on the hair in advance or even to select them appropriately.

[0011] In academic and industrial settings, a researcher or developer may have access to a variety of physical, chemical-analytical, and / or biophysical methods to determine the degree of internal and external damage to hair. Traditionally, chromatographic techniques are used, such as high-performance liquid chromatography (HPLC) following a complex acid hydrolytic digestion of the hair sample. Such methods are generally very complex in terms of equipment and are often unusable for end users or consumers due to a lack of access.

[0012] Damaging cosmetic treatments, such as hair coloring, heat treatments, perms, or oxidative procedures such as bleaching, among many others, are typically performed in private settings or as part of commercial services for end users. Although performing a further damaging procedure on previously damaged hair can lead to catastrophic results, including complete hair breakage, there has previously been no simple way to determine the degree of hair stretch in this context.

[0013] Furthermore, there are many different hair treatment products on the market that claim to improve various hair properties or parameters, such as shine. However, in many cases, the user of such products is unaware of the damage caused to their hair. This can lead to the user reaching for products that are less suitable for their specific needs and being dissatisfied with their effectiveness after use.

[0014] Document DE102016212202 A1 describes a method for determining the degree of hair damage by analyzing near-infrared spectra. Document EP1629775 A1 describes a method for determining hair damage using multivariate component analysis of a near-infrared absorption spectrum of hair.

[0015] Therefore, determining the degree of stretching of the hair can be of great importance.

[0016] In addition, it can be advantageous to offer a product tailored to individual needs.

[0017] It can be considered an object of the present invention to simplify the determination of a degree of elongation of hair, in particular with regard to the expenditure on equipment and time.

[0018] This object is achieved by the features of the independent claims. Further developments of the invention emerge from the dependent claims and the following description.

[0019] The invention is based, among other things, on the following findings: It was recognized that the overstretching of hair (the degree of stretching) is a relevant cosmetic parameter and that this degree of stretching can be determined with very little effort using near-infrared sensors. This enables a non-mechanical and contactless determination of the degree of stretching of hair. In particular, the degree of stretching can be determined in a near-infrared wavelength range (generally in the wavelength range from 780 to 3000 nm), which enables the use of a near-infrared sensor with minimal equipment complexity.

[0020] Human hair essentially consists of the dominant elements of cuticle cells and cortex cells. In addition to amorphous components, complex fibrillar structures can be found in the cortex cells, which give the hair its mechanical stability. The basic building blocks of this complex fiber hierarchy are so-called α-helices as secondary structures. Besides α-helices, so-called β-fold structures are the most common form of secondary structure. In terms of the length per amino acid unit, α-helices are significantly more compact than β-fold structures. The length of α-helices is approximately 0.15 nm per amino acid, whereas in the pleated sheet structure, 0.35 nm per amino acid is available, which corresponds to a factor of well over 2. When hair is mechanically stretched, a conversion of α-helices into β-pleated sheet structures can be observed.This represents a transformation process of existing structural elements and changes the structure of hair, which can be detected in an absorption spectrum of a hair sample in the infrared range.

[0021] According to one aspect, an arrangement for determining the degree of elongation of hair is specified with the features of independent claim 1. The arrangement comprises a detection unit for detecting hair characteristics and an evaluation unit for evaluating the detected hair characteristics and for determining the degree of elongation of hair based on the detected hair characteristics. The detection unit contains a near-infrared sensor (NIRS) and is designed to irradiate a hair sample with electromagnetic waves in the infrared range and to detect an absorption level of the hair sample in a wavelength range from 800 to 2500 nm. The detection unit is further designed to generate an absorption spectrum of the hair sample in the wavelength range from 800 to 2500 nm and to provide it to the evaluation unit.The evaluation unit is designed to compare the absorption spectrum with a calibration model and to determine a degree of elongation of the hair sample based on the absorption spectrum and the calibration model.

[0022] It has been recognized that the absorption spectrum changes depending on the structure of hair, and that the absorption spectrum in a wavelength range from 800 to 2500 nm (including these limits) is particularly important for determining the degree of stretching or mechanical overstretching of hair. The vibration frequency and thus also the absorption spectrum of overstretched hair changes due to its structure. Overstretching transforms α-helices into β-sheet structures, which changes the absorption spectrum.

[0023] Furthermore, it was discovered that using a near-infrared sensor in the wavelength range from 800 nm to 2500 nm, an absorption spectrum of a hair sample can be recorded and / or generated, and that the absorption spectrum in this wavelength range provides information about the degree of elongation of hair. In particular, the degree of elongation of hair can be determined in a wavelength range below 3000 nm. This allows the use of near-infrared sensors with relatively low equipment complexity. There is no need to resort to much more complex sensors for the mid- or far-infrared range.

[0024] Near infrared (NIR), as used in this specification, refers to electromagnetic waves with a wavelength between 780 nm and 3000 nm (inclusive). As described elsewhere in this document, specific smaller wavelength ranges are selected from this wavelength range to create an absorption spectrum of a hair sample and to use this spectrum to infer the internal structure of the hair sample.

[0025] In the wavelength range between 800 and 2500 nm, harmonics of the α-helices and β-sheet structures can be detected, which are an indicator of the degree of elongation of hair. In particular, the wavelength range between 2000 and 2500 nm, and more particularly between 2000 and 2350 nm, can be used to determine the absorption spectrum and to determine the degree of elongation. The wavelength range under consideration can be referred to as the relevant wavelength range.

[0026] Harmonics of the α-helices can occur in particular at at least one of the wavelengths from a first group of 2012 nm, 2056 nm, 2168 nm, 2183 nm, 2206 nm, 2293 nm, 2345 nm. Harmonics of the β-sheet structures can occur in particular at at least one of the wavelengths from a second group of 2055 nm, 2166 nm, 2208 nm, 2297 nm, 2343 nm. The respective absorbance of the hair sample at at least one wavelength from each of the two above groups can indicate the proportion of α-helices and β-sheet structures in the hair sample.

[0027] Of course, the entire absorption spectrum across more than one wavelength from each of the two above groups can also be used to determine the degree of stretching. The range of the absorption spectrum used corresponds to the relevant wavelength range mentioned above.

[0028] In a calibration model, the absorption spectra of hair samples in the relevant wavelength range can be stored with different degrees of stretching. Each hair sample and each absorption spectrum is assigned a degree of stretching, and the degree of stretching of the absorption spectrum from the calibration model that is qualitatively and / or quantitatively most similar to the absorption spectrum of the hair sample under investigation is assigned to the hair sample under investigation.

[0029] In particular, the recorded absorption spectrum of the hair sample in the relevant wavelength range is compared with the relevant wavelength range of the absorption spectra of the calibration model.

[0030] The elongation can be expressed as the ratio of the length of a stretched hair to an unstretched hair.

[0031] Elongation is a dimensionless value. If hair is only stretched within the completely reversible range (typically up to 3% to 5% of the original length, i.e. unstretched length), it always returns to its original length after stretching. Only if the hair is stretched beyond the reversible range (from approximately 10% to 15% elongation the partially irreversible conversion of α-helices into β-sheet structures begins, from approximately 25% elongation the hair begins to break) will it no longer fully return to its unstretched length because this involves an irreversible conversion of α-helices into β-sheet structures. Different degrees of stretching can be expressed as degrees of stretching. The scale from unstretched to breaking of a hair can be divided into two or more degrees of stretching.

[0032] The following strain levels can be used, for example: unstretched, slightly stretched, severely stretched, and repeatedly severely stretched. Other chemical, physical, or biophysical methods can be used to determine strain levels in the calibration model.

[0033] The evaluation unit may be a processor or a computer that implements and executes signal processing algorithms to determine the absorption spectrum of the hair sample based on the signals detected by the NIR sensor.

[0034] A hair sample may be a single hair, but preferably contains a plurality of individual hairs to increase the intensity of the light emitted by the hair sample as the inverse of the light absorbed by the hair sample (or the amount of emitted light relative to the light emitted) compared to a single hair. For example, hair can be examined non-destructively by directing the detection unit toward a person's scalp hair. In other words, the hair can be examined without having to cut it.

[0035] The absorption spectrum can be determined from the light emitted by the hair sample. In this context, a light spectrum is defined as the absorption of light over a specific wavelength. The spectrum can be a continuous value indicating the absorption of light in a wavelength range, from a lower value to an upper value. This continuous value describes the degree of absorption of light over a specific wavelength and has a characteristic curve for the structure of the individual hairs in the hair sample.

[0036] The near-infrared sensor enables the use of near-infrared spectroscopy methods. These methods allow for direct, non-destructive testing of hair structure without complex sample preparation and without altering or destroying the hair structure during analysis.

[0037] This can enable faster results. Furthermore, it may be possible to subject the hair to further treatments after the measurement, allowing multiple applications or tests to be performed on a single hair sample (e.g., a strand of hair).

[0038] In addition, it may be possible to carry out measurements relatively easily at different hair positions (e.g. hair close to the scalp and hair far from the scalp), for example directly on the head, without having to take the hair sample.

[0039] Near-infrared spectroscopy can be used, for example, when sample preparation is difficult or impossible and a large number of samples must be analyzed in a short time, e.g. in pharmaceutical production for batch release or for measurements on skin or other biological objects.

[0040] Near-infrared spectroscopy is based on the measurement of spectral absorption through vibrational excitations of chemical bonds or structures in the hair sample. Depending on the type of bond or structure, absorption can occur at different wavelengths. Typically, absorption follows the Beer-Lambert law and is thus proportional to the concentration of a component responsible for the absorption. Overlapping absorptions are additive, allowing quantification based on the absorption spectra.

[0041] However, these absorptions may be overtones (e.g., in the NIR range) or combination vibrations. This can make it difficult to assign individual absorption wavelengths.

[0042] For this reason, chemometric methods can be used to evaluate the spectra and, in particular, for quantitative evaluation in order to use the calibration model as a starting point for assigning a damage category.

[0043] NIR spectroscopy can also be suitable for measuring hair because the near-infrared radiation not only analyzes the surface of the hair, but because of the small absorption cross sections for the near-infrared radiation (e.g. compared to light in the visible wavelength range), the hair can be at least partially penetrated and the internal structure of hair is also taken into account, which can be particularly relevant for determining the degree of elongation.

[0044] The spectra can be evaluated using a computational model, which can be developed during a calibration and validation phase using a sufficiently large set of reference spectra. This may require that reference values ​​for the parameters to be calibrated are available for all spectra.

[0045] The computational model can be an artificial system that, for example, learns from the calibration hair samples and can generalize them after the learning phase has ended. This means that the examples are not simply learned by heart, but patterns and regularities in the learning data are recognized. Different approaches can be pursued for this. For example, supervised learning, semi-supervised learning, unsupervised learning, reinforcement learning and / or active learning can be used, particularly in conjunction with so-called deep learning methods. Supervised learning can, for example, be carried out using an artificial neural network (e.g. a recurrent neural network) or a support vector machine. Unsupervised learning can also be carried out, for example, using an artificial neural network (e.g. an autoencoder), decision trees or by applying ensemble methods (e.g. so-calleddecision tree ensembles).

[0046] Spectra can generally be measured in either transmission or reflection. Reflection captures the electromagnetic waves reflected by a sample, while transmission captures the electromagnetic waves passing through / transmitting the sample. For the purposes of this description, the reflected or passing through / transmitting electromagnetic waves are referred to as emitted electromagnetic waves or emitted light.

[0047] The absorption spectrum is generated by comparing or subtracting the electromagnetic waves detected by the detection unit (corresponding to the light emitted by the hair sample) with the initially emitted electromagnetic waves. The intensity versus wavelength represents the spectrum. The difference in intensity versus wavelength between the emitted NIR light and the detected NIR light represents the absorption spectrum.

[0048] According to one embodiment, the evaluation unit is designed to compare a profile of the absorption spectrum of the hair sample with a plurality of absorption spectra from the calibration model.

[0049] The calibration model can be stored locally in the evaluation unit. Alternatively, the evaluation unit can access an external data storage unit and retrieve the calibration model data for temporary use. This allows the calibration model to be stored centrally and modified as needed. This ensures that the (decentralized) evaluation unit always has a current data set of the calibration model at its disposal.

[0050] According to a further embodiment, the detection unit is designed to detect or obtain a moisture level of the hair sample and to provide the moisture level to the evaluation unit, and the evaluation unit is designed to take the moisture level of the hair sample into account when comparing the generated absorption spectrum with the calibration model.

[0051] The moisture content of the hair sample can, for example, be entered by a user or recorded by a sensor. This sensor can be part of the recording unit.

[0052] It has been found that stretched or overstretched hair changes its moisture content, or water content. This also changes the hair's absorption spectrum. If the hair is exposed to an external source of moisture, such as high humidity or rain, this can influence the absorption spectrum in the specified wavelength range and also the assigned degree of stretch. To eliminate the influence of moisture on the measurement result, the moisture content of the hair sample is taken into account.

[0053] To indicate the moisture level, simply specifying the air humidity may be sufficient. Humidity can be expressed, for example, as relative humidity, which is expressed as a percentage by weight and indicates the weight ratio of the current water vapor content to the maximum possible water vapor content in the air at the current temperature. The moisture level can also be expressed as the weight percentage of water relative to the total weight of the wet hair sample (weight of the hair + weight of the water). In simplified terms, the moisture level can then be expressed as one of several levels: slightly damp, damp, wet, very wet.

[0054] According to a further embodiment, the evaluation unit is designed to assign a damage category to the hair sample based on the comparison of the generated absorption spectrum with the calibration model.

[0055] The known and available absorption spectra of hair samples can be part of the calibration model. For example, the calibration model can be created based on a plurality of calibration hair samples, with a calibration spectrum being acquired for each individual calibration hair sample (as described above for generating the spectrum of the hair sample under investigation). The calibration hair sample is then analyzed for damage using other independent analytical methods, and the resulting damage is assigned to the calibration hair sample.

[0056] By comparing the spectra of the calibration hair samples with the spectrum of the hair sample under investigation, the degree of elongation of the latter can be determined. The shape of the spectrum and / or its intensity can be taken into account during this comparison. Taking the shape into account can lead to a successful comparison even if the hair structure of the hair sample under investigation and the calibration hair samples do not match.

[0057] The calibration model can be stored in a local memory of the device or in an external data storage unit. The acquisition unit records at least a portion of a spectrum of NIR light that has interacted with the hair sample and compares this spectrum with a plurality of calibration hair samples. For this comparison, a processor of the evaluation unit is used, for example, and at least a portion of the spectrum of the hair sample under investigation is compared with the spectroscopic calibration model to determine the degree of elongation of the hair.

[0058] According to a further embodiment, the near-infrared sensor is a spectrometer, wherein the spectrometer is designed to create a signal pattern based on the detected light, which is characteristic of the detected hair features (can also be generally referred to as hair properties).

[0059] This means that it is not necessary to determine absolute values ​​for hair characteristics or properties. Rather, it may be sufficient to use the signal patterns obtained from the spectrometer to determine a product recommendation and / or application instruction for the treatment and / or care of the hair. The signal pattern can be part of each calibration sample of the calibration model. Independently of this, it can be determined which products and / or application instructions are appropriate for hair samples with a certain signal pattern. The corresponding signal pattern can then be assigned to the products and / or application instructions determined in this way to express that these products and / or application instructions are suitable for hair with this signal pattern and to achieve a certain effect.This means that finding a suitable product recommendation is simplified because only the signal patterns determined from the hair sample examined need to be compared with signal patterns associated with the products and / or application and treatment instructions.

[0060] According to a further embodiment, the arrangement further comprises a housing and an energy storage device, wherein the evaluation unit is accommodated in the housing and the detection unit is coupled to the housing, and wherein the energy storage device is arranged in the housing in order to supply the evaluation unit with energy and in order to enable at least temporarily autonomous operation of the evaluation unit without connection to an external energy source.

[0061] This means that the evaluation unit can be operated autonomously and without external power supply as intended. The energy storage device is preferably a rechargeable energy storage device. In one embodiment, the user interface is also arranged in the housing and can be powered by the energy source to also operate autonomously. In another embodiment, the energy storage device can also power the detection unit.

[0062] The housing and the evaluation unit can be part of a user's personal device. The personal device can be a portable computer in the form of a smartphone, a tablet, or another computer (these units can generally be referred to as a computing unit or portable computing unit). The detection unit can be connected to or integrated into the computing unit and used as described herein to determine the degree of elongation of hair. In a computer program product (e.g., software or application for the personal / portable device), the detected characteristics of the hair are then displayed in the form of values, arbitrary units, or output acoustically.From the parameters, (a) product recommendations for individually suitable treatment products and individual treatment tips can then be derived and / or (b) the treatment success of a cosmetic treatment that aims to positively influence the measured parameters can be determined and / or displayed.

[0063] The detection unit can have an interface (also: data transmission connection) via which a connection to the computing unit is established. The computing unit can have a first interface and a second interface. The first interface can be designed as a counterpart to the interface of the detection unit, i.e. to connect the detection unit to the computing unit. The second interface can be designed to connect the computing unit to a data network. These connections are designed to transmit information in at least one direction, preferably in both directions. The connection between the detection unit and the computing unit on the one hand, and the connection between the computing unit and an access point of the data network can be wired or wireless. Wired connections can, for example, use optical or electrical signals to transmit information.Wireless connections typically use electromagnetic waves for signal transmission, e.g. radio signals or optical signals.

[0064] Protocols that operate according to the principles of mesh networks can be used to connect the acquisition unit to the processing unit. For example, the Thread protocol, which is based on IPv6, can be used for data transmission and for connecting the acquisition unit to the processing unit. The Thread protocol is used in particular to connect automated or semi-automated devices to each other, in this case, for example, the acquisition unit to the processing unit.

[0065] In one example, the detection unit can be structurally plugged onto the computing unit, or conversely, the computing unit can be plugged onto the detection unit. This means that the detection unit is mechanically attached to the computing unit or a housing of the computing unit. For example, this can be achieved through tool-free assembly via a reversible connection. In the plugged-in position, the detection unit can be held relative to the computing unit with a detachable force-locking or form-locking connection. The interfaces between the detection unit and the computing unit can be arranged such that, in the plugged-in position, an electrical connection between the detection unit and the computing unit is automatically established or created.

[0066] The computing unit can execute an application (or a program, hereinafter also referred to as a computer program product) that receives or requests data from the acquisition unit. The received or requested data is used in the application to determine one or more output values. The data is processed and / or evaluated by the application according to the approaches described herein.

[0067] Processors (and one or more memory modules) of the computing unit can be used to execute the application. However, the computing unit can also be configured to outsource computational steps for executing the application. For example, the application can transfer the data received or queried by the acquisition unit to an external computing unit. Before the data is transferred to the external computing unit, it can be preprocessed.

[0068] The external processing unit can be located at a distance from the acquisition unit and the portable processing unit. The portable processing unit can be connected to the external processing unit via the data network, i.e. have a communication link. The external processing unit can be a single computer or processor or a network of computers or processors. In a computer or processor network, the computing load can be distributed among the individual components of the network in various ways. In addition to computing power, this computer network can also provide storage capacity for users and hold data released or marked by users. This can reduce the storage space required in the portable processing unit. It is also easier for the user to replace a portable processing unit because little or no data is stored locally.The computer network can be designed as a group of meshed networked servers.

[0069] According to a further embodiment, the evaluation unit is designed to compare the characteristics of treatment agents for treating hair with the detected hair characteristics and to determine an effect of the treatment agents on the hair taking into account the detected hair characteristics.

[0070] This means that the treatment agents are selected and determined based on the determined hair properties or hair characteristics. These treatment agents can, for example, be displayed on the user interface or output in another way.

[0071] According to a further embodiment, the evaluation unit is designed to transmit the detected hair characteristics to a data storage unit and to request information on the treatment of the hair according to the detected hair characteristics from the data storage unit.

[0072] These instructions may be general advice (without reference to a specific treatment) regarding hair treatment, but they may also be advice related to a specific treatment. The instructions may also include explanations of which behaviors affect which hair properties and how.

[0073] The data storage unit can contain information from studies as well as information from literature sources and / or scientific publications. The evaluation unit can be designed to display, output, or at least alert a user to an extract of this information depending on the recorded hair properties.

[0074] According to a further embodiment, the arrangement further comprises a user interface and the evaluation unit is designed to instruct the user interface to output the received instructions for treating the hair.

[0075] The user interface can, for example, be a display of the portable computing unit, in particular a so-called touchscreen, which enables content to be displayed visually and user input to be received via touch.

[0076] According to a further embodiment, the evaluation unit is designed to query information from a user and to additionally take this information into account when querying the data storage unit in order to obtain from the data storage unit features of treatment agents for treating hair according to the information queried by the user.

[0077] The requested information can be collected using a predefined questionnaire, in which the user assigns more or less weight to a statement, or selects one from several possible answers. The predefined questionnaire can specifically address the user's lifestyle and unusual stressors, for example, eating habits, duration and quality of sleep, amount of alcohol consumed, type of beverage, use of stimulants (e.g., nicotine, alcohol), professional activities, and leisure activities (spent a lot of time outdoors in all weather conditions, spending time in the mountains, visiting a solarium). The user's age, gender, and ethnicity can also be queried, and these can be used to query the treatment data store. The requested information can also relate to a desired or desired hair property.

[0078] According to a further embodiment, the evaluation unit has a local memory which is designed to store the data retrieved from the data storage unit, preferably to store it persistently.

[0079] This means that the evaluation unit can at least temporarily perform its functions without being dependent on a permanent connection to the data storage unit or the data network. The retrieved data is stored in the local memory. The data is stored in the local memory in such a way that it is retained even if the evaluation unit is switched off or deactivated (persistent storage). It is possible for the evaluation unit to only retrieve data from the data storage unit that matches a current image or current properties of the hair. In one embodiment, data that matches slightly changed properties of the hair based on the current state can also be retrieved and stored locally. It is therefore not necessary to retrieve all data from the data storage unit and store it in the local memory.Rather, the data or information that matches the recorded condition of the hair can be transferred from the data storage unit to the local storage.

[0080] According to a further embodiment, the evaluation unit is designed to store the detected hair features in the local memory, provided with a time stamp relating to the detection of the hair features.

[0081] This makes it possible to observe and analyze changes in the hair over time. These changes can also be used to provide suitable non-therapeutic treatments and / or treatment recommendations. Furthermore, this embodiment allows a user to observe the changes in order to determine whether self-set goals have been achieved or are approaching.

[0082] According to a further embodiment, the evaluation unit is designed to store the detected hair features in the local memory over a longer period of time, comprising at least two processes of detecting the hair features, and to optionally retrieve a development of the hair features over a predeterminable period of time from the local memory and to instruct the output unit to display or output this development.

[0083] According to a further embodiment, the evaluation unit is designed to transmit the detected hair features to the data storage unit.

[0084] The captured and transmitted hair characteristics can be assigned to a user ID or code in the data storage unit, allowing a user to view their data from various devices. This approach also has the advantage that a user's data is backed up or stored in a central location in the event of loss or damage to the personal evaluation unit.

[0085] Furthermore, this embodiment makes it possible to record a user's hair characteristics over a longer period of time and to observe their changes and, if necessary, to link them to recommendations for non-therapeutic treatment agents and / or treatment instructions.

[0086] According to a further embodiment, the arrangement is designed to output instructions for operating the detection unit visually on the output unit and / or acoustically via a loudspeaker. This can be particularly helpful when a user's hair is being comprehensively detected for the first time in order to obtain an overview of the hair's condition.

[0087] According to a further embodiment, the output unit is designed to output information about a treatment agent, e.g. a product name, information regarding ingredients and / or composition of a treatment agent and / or application instructions for the non-therapeutic treatment of the hair.

[0088] This allows the user to form their own opinion about a treatment in its entirety. Furthermore, the user can be given instructions for use related to a treatment or independent of it. These instructions can refer to desired and / or undesired behavior.

[0089] According to a further embodiment, the user interface is designed to receive an input from a user after outputting features of a treatment agent and, based on this input, to initiate an action relating to the displayed or output treatment agent.

[0090] The action can, for example, involve offering the user a treatment product for purchase and allowing the user to initiate the purchase by entering information. In addition to the purchase of treatment products, the user can also be offered further information on the purchase. This further information can relate to more detailed treatment and application instructions. For example, the program receives the request that the user wishes to purchase the treatment product, saves the request, and / or forwards the request to a commercial company that sells the treatment products. The computer program prompts the user to enter their personal data (address, bank information, shipping preferences, etc.) via the input unit.

[0091] Alternatively, the user can be informed where he or she can purchase the dispensed treatment product on site, for example in a drugstore, hair salon, pharmacy, etc. in his or her vicinity.

[0092] More and more customers want a product tailored to their individual needs. Accordingly, a customized treatment product can be recommended to the user and an ordering process initiated, for example, by accessing the website of a manufacturer of customized hair treatment products.

[0093] This can be a treatment product manufactured specifically for a specific user or a so-called "mass customized" product. With a "mass customized" product, individualization can be achieved by varying a few, but from the customer's perspective, crucial, features. These "mass customized" products are preferably based on the concept of modularization, meaning the product can be individually assembled from various modules / building blocks.

[0094] There are often numerous dependencies between the many different features / ingredients of a product, which can be expressed as "requirements" or "prohibitions." To obtain a clear product definition, it can be advantageous to use a product configurator during the ordering process. This configurator assists the user in selecting the features / ingredients and indicates the permitted / prohibited feature combinations, whereby the latter cannot then be selected.

[0095] For hair treatment products, the relevant product characteristics include, in particular, the chemical ingredients of the products, their physical properties, and the packaging type. A product configurator can, for example, help avoid the selection of chemically and / or physically incompatible ingredients or the selection of ingredients unsuitable for the determined degree of damage / stretching, etc. Conversely, the product configurator can predetermine or suggest suitable ingredients for the determined degree of damage / stretching, etc.

[0096] It is also possible to produce an individual hair treatment product on-site, for example in a hair salon or at a point of sale of hair treatment products, such as a drugstore, using a mixing device, preferably an intelligent mixing device (smart mixer).

[0097] According to a further aspect, a method for determining a degree of elongation of hair is as specified in independent claim 11. The method comprises the following steps: irradiating a hair sample with electromagnetic waves in the infrared range; detecting the light emitted by the hair sample; detecting an absorption degree of the hair sample in a wavelength range of 800 to 2500 nm; generating an absorption spectrum of the hair sample in the wavelength range of 800 to 2500 nm; comparing the generated absorption spectrum with a calibration model, and determining the degree of elongation of hair based on the absorption spectrum and the calibration model.

[0098] This method corresponds to the function of the arrangement described above. The method steps correspond to the functions of the arrangement and will not be described again here. For details on the method steps, please refer to the above description of the arrangement and its function. The remaining functions of the arrangement can, of course, also be implemented as method steps.

[0099] When comparing the generated absorption spectrum with the calibration model, in particular a profile of the absorption spectrum of the hair sample can be compared with a plurality of absorption spectra from the calibration model.

[0100] According to one embodiment, the method comprises the step of detecting or obtaining a moisture level of the hair sample and using the moisture level of the hair sample when comparing the generated absorption spectrum with the calibration model.

[0101] According to one embodiment, the method comprises the following step: assigning a damage category to the hair sample based on the comparison of the generated absorption spectrum with the calibration model.

[0102] According to a further aspect, a method for determining a treatment agent based on the determined degree of stretching of hair is provided. The method comprises the following steps: using the determined degree of stretching of hair; selecting a treatment agent for hair based on the determined degree of stretching; and outputting information about the selected treatment agent.

[0103] The treatment agent is selected or determined based on the determined or specified degree of stretching and taking into account a desired effect, such as the desired properties of the hair after treatment. The desired effect can be an effect specified by a user or a desired condition of the hair. It can be helpful to assign one or more types of damage or degrees of stretching to each treatment agent, for which application is possible, as well as an effect that the treatment agent has for the corresponding type of damage or degree of stretching. This allows the appropriate treatment agent to be determined by simply comparing the type of damage or degree of stretching with the desired effect.

[0104] According to a further aspect there is provided a computer program product as set out in claim 15, which is adapted to carry out the method of claim 11 when executed on an arrangement of claim 1.

[0105] The computer program product enables monitoring and tracking of results by displaying (e.g., graphically) the measurement results over time. Based on the results achieved, the computer program product provides personalized treatment and product recommendations. The quality of the treatment and product recommendations can be improved by having the user answer additional questions about their hair condition, dietary habits, general health, and other behavioral traits, which the computer program product can process accordingly. This is based not only on literature data, for example, but also on the treatment success of other users of the computer program product, particularly the treatment success of other users who have at least a similar hair condition.

[0106] The data collected via the questionnaire can be used to analyze the development of the user's hair condition under the given circumstances, i.e., the data entered by the user. This development can be compared with the development of other users. From this, it can be concluded whether, during treatment with a particular product, the development of users with similar or identical questionnaire entries is similar or differs from that of users with different entries.

[0107] The data entered by the user can thus be used for a global analysis to monitor the success of a treatment and the effectiveness of a product under different conditions and, if necessary, to recommend changes to the treatment and / or product.

[0108] Embodiments of the invention are illustrated in the figures and explained in more detail below. Herein: Fig. 1 shows a schematic representation of an arrangement for determining the degree of stretching of hair according to one embodiment; Fig. 2 shows a schematic representation of a data carrier according to a further embodiment; Fig. 3 shows a schematic representation of steps of a method according to a further embodiment; Fig. 4 shows a schematic representation of a detection unit for an arrangement according to a further embodiment; Fig. 5 shows a schematic representation of an absorption spectrum indicative of the degree of stretching of hair; Fig. 6 shows a schematic representation of a stress-strain diagram of hair.

[0109] In the following detailed description, reference is made to the accompanying drawings, which form a part of this application, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. It should be understood that other embodiments may be utilized and structural, functional, or logical changes may be made without departing from the scope of the present invention. In this regard, directional terminology such as "top," "bottom," "front," "back," "forward," "rear," etc., is used with reference to the orientation of the described figure(s). Since components of embodiments may be positioned in a number of different orientations, the directional terminology is for purposes of illustration and is in no way limiting.It is understood that the features of the various exemplary embodiments described herein may be combined with one another unless specifically stated otherwise. The following detailed description is therefore not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims and equivalents thereof.

[0110] Fig. 1 shows an arrangement 100 for determining the degree of stretching of hair. The arrangement 100 has a detection unit 110, an evaluation unit 120, and a user interface 130. The detection unit 110 is designed to detect properties or characteristics of hair. For this purpose, the detection unit 110 emits infrared light in the direction of an area 12 to be examined of the analysis object 10 (for example, human hair) and detects the emitted light in order to detect an absorption level of the hair sample in a wavelength range from 800 to 2500 nm. The light emitted by the area 12 to be examined is recorded by the detection unit 110 and allows conclusions to be drawn about the degree of stretching of the hair because the structure that changes when the hair is stretched or overstretched has an individual absorption spectrum in the detected wavelength range.

[0111] The detection unit 110 comprises a suitable source of electromagnetic waves. This source is a light emitter or laser emitter and can also be referred to as a radiation source, and is arranged on or in the detection unit 110. The radiation source can be arranged on or in the detection unit 110 such that, when emitting the electromagnetic waves 112, the radiation source assumes a predetermined distance from the area 12 to be examined, particularly when the detection unit 110 is placed on the area to be examined. The distance of the radiation source from the area to be examined can be variable and can be changed using actuators or manually.

[0112] The detection unit 110 is connected to the evaluation unit 120 via a data transmission connection 114. The data transmission connection 114 can enable unidirectional or bidirectional data transmission between the detection unit 110 and the evaluation unit 120. Thus, the detection unit 110 delivers signals relating to the detected features of the hair to the evaluation unit 120, whereas the evaluation unit 120 can deliver control commands to the detection unit 110, wherein the control commands specify how the detection unit 110 operates. In the case of a unidirectional data transmission connection 114, which only enables data transmission from the detection unit 110 to the evaluation unit 120, control parameters can be specified via input elements (buttons, switches, rotary controls, etc., not shown) on the detection unit 110.The acquisition unit 110 may have display elements (not shown) that indicate the status of the acquisition unit or the set control parameters. Alternatively, the acquisition unit 110 can also transmit the set control parameters to the evaluation unit 120, where they can be optionally displayed.

[0113] The evaluation unit 120 has a processor 126 and a local memory 128. The evaluation unit 120 receives signals relating to the characteristics of the examined area 12 of the hair sample 10 and, based on these characteristics, determines a recommendation relating to a non-therapeutic treatment of the examined hair. The non-therapeutic treatment may include recommendations regarding treatment agents and / or treatment instructions or application instructions for the respective hair examined. Treatment instructions and application instructions are used synonymously in the context of this description and refer to instructions for the non-therapeutic treatment of the examined area (hair) 12 using selected treatment agents or without using treatment agents. Treatment instructions may, in particular, include the application of a treatment agent or measures to be taken or omitted by the user.For example, the treatment instructions can contain an indication of desired or undesired behavior after the application of a treatment agent. To determine a recommended non-therapeutic treatment, the recorded characteristics of the examined area 12 can be compared with the areas of application, effects, and application instructions of treatment agents and / or treatment instructions. Information about the treatment agents and / or treatment instructions can be stored in a data storage unit 140.

[0114] The data storage unit 140 can be arranged outside and spatially separated from the evaluation unit 120. The evaluation unit 120 can access the data storage unit 140 via a data network 122 and retrieve information about the treatment agents and / or treatment instructions stored there. This retrieved information is compared by the evaluation unit 120 with the recorded characteristics of the area 12 to be examined in order to determine appropriate recommendations for the non-therapeutic treatment of the hair examined. In other words, this means that the data storage unit is queried using the recorded hair characteristics (or determined hair properties). A large number of stored information can first be retrieved from the data storage unit in order to then process this information using the determined hair properties and, if applicable,Filtering treatment goals based on which treatment agents and / or treatment instructions are relevant. For this purpose, the data from the data store can be loaded into a volatile RAM. Alternatively, the determined hair properties can be used when retrieving the information from the data store to retrieve only the relevant information from the data store. For the purposes of this description, these two variants can be considered to have equivalent effects.

[0115] The data network 122 may be a public data transmission network, which has partially wired or wireless transmission sections. For example, the evaluation unit 120 may establish a wireless connection to an access point (not shown) of the data network 122 in order to establish a corresponding connection to the data storage unit 140.

[0116] The user interface 130 is connected to the evaluation unit 120 via the data transmission connection 124. The user interface 130 has an input unit 132 and an output unit 134. The input unit 132 enables a user to specify parameters for the operation and configuration of the evaluation unit 120, the acquisition unit 110, and / or the user interface 130. The input unit 132 can receive information via various interfaces: a keyboard, a mouse, a touch-sensitive display, or a microphone (so-called voice control). It is conceivable that any interface via which a human user can communicate with a computing unit and enter or transfer data can be used. The air humidity or a moisture level of the hair can be entered via the input unit.The output unit 134 can be a display or other display unit that outputs visual information to a user. The output unit 134 can also have a speaker through which acoustic information can be output. Visual information can be output on a touch-sensitive output unit, so that the output unit also allows a user to enter inputs.

[0117] The evaluation unit 120 has a processor 126 and a local memory 128. The processor 126 executes instructions to perform its intended function or functions. The hair characteristics detected by the detection unit 110 or the associated signals or values ​​can be stored in the local memory 128.

[0118] A particular aspect of this exemplary embodiment is that the detection unit 110 can be operated with an evaluation unit 120 and a user interface 130, which are implemented in a portable device of a user or consumer. This makes it particularly easy to couple a detection unit 110, which enables advanced analysis and examination options for the hair of a human user, to a portable computerized data processing device. The portable data processing device can be, for example, a smartphone or a tablet, or a home computer. The detection unit 110 can be mechanically, electrically, and signal-connected or coupled to the portable data processing device by means of a defined interface.

[0119] Fig. 2 shows a data carrier 300. A computer program product is stored on the data carrier, which is designed to be executed on a portable computing unit 120 and to instruct a processor 126 of the portable computing unit to carry out the following steps (cf. also the method steps in Fig. 3 ): Irradiating (410) a hair sample with electromagnetic waves in the infrared range; detecting (420) the light emitted by the hair sample; detecting (430) an absorption level of the hair sample in a wavelength range from 800 to 2500 nm; generating (440) an absorption spectrum of the hair sample in the wavelength range from 800 to 2500 nm; comparing (450) the generated absorption spectrum with a calibration model and determining the degree of elongation of hair based on the absorption spectrum and the calibration model.

[0120] The data carrier 300 may use magnetic, optical, or electrical storage techniques (or combinations thereof) to store the instructions of the computer program product in a machine-readable form. These instructions may be used to directly execute the instructions by the processor 126 of a portable computing unit 120 (the evaluation unit 120 from the embodiment of the Fig. 1 ) to be executed. Alternatively, the instructions can be used to load the computer program product into an internal memory of the portable computing unit 120 in order to then be executed from there. This internal memory can be, for example, the local memory 128 from the Fig. 1 act.

[0121] The data storage device 300 can be a mobile and / or portable data storage device. Alternatively, the computer program product can also be loaded via a data network by a portable computing device accessing the data storage device 300 via the data network to load the computer program product via the data network. The computer program product can be loaded onto a user's portable device via a data network and installed on the portable device for use by the user.

[0122] In addition to Fig. 2 is in Fig. 3 a method 400 is shown with the following steps (these steps correspond to the functions of the computer program product): irradiating (410) a hair sample with electromagnetic waves in the infrared range; detecting (420) the light emitted by the hair sample; detecting (430) an absorption level of the hair sample in a wavelength range from 800 to 2500 nm; generating (440) an absorption spectrum of the hair sample in the wavelength range from 800 to 2500 nm; comparing (450) the generated absorption spectrum with a calibration model and determining the degree of elongation of hair based on the absorption spectrum and the calibration model.

[0123] The computer program product includes instructions that instruct the processor 126 of the portable computing device 120 to perform these steps 410 to 450.

[0124] Of course, the method 400 or its steps 410 to 450 may be implemented in accordance with one of the embodiments of the arrangement 100, as described with reference to Fig. 1 and the remaining description. This means that the functions of the arrangement 100 or one of its components, in particular the evaluation unit 120, described herein can be implemented as a step of the method 400. The functions of the evaluation unit will not be repeated here. Rather, those skilled in the art will recognize that and how these functions are implemented as method steps.

[0125] The various method steps as well as the components of the arrangement can be implemented by one or more circuits. In one embodiment, a "circuit" is understood to be any unit that implements logic, and can be hardware, software, firmware, or a combination thereof. Thus, in one embodiment, a "circuit" can be a hard-wired logic circuit or a programmable logic circuit, such as a programmable processor, e.g., a microprocessor or an FPGA (field programmable gate array). A "circuit" can also be understood to be a processor that executes software, e.g., any type of computer program, such as a computer program in programming code for a virtual machine (delimited runtime environment, virtual machine), such as a Java computer program.In one embodiment, a "circuit" may be understood to mean any type of implementation of the functions described below.

[0126] Fig. 4 shows a schematic representation of a detection unit 110. The detection unit has a surface 111 on which a light emitter 116 and an NIR sensor 118 are shown. The NIR sensor 118 can be a spectrometer. The light emitter 116 is shown as circular, and the NIR sensor 118 is shown as square.

[0127] The surface facing the user's hair during a detection process is visible from the detection unit 110. In other words, the light emitter 116 emits the light rays from the plane of the drawing toward a viewer.

[0128] When a human user's hair is irradiated with light (e.g. laser), a portion of this light is emitted depending on the chemical composition and / or structure of the hair.

[0129] The processor 126 ( Fig. 1 ) can implement control functions and issue control commands to the light emitter 116. Thus, the processor 126 can control the light emitter to emit light of a certain intensity, wavelength, and / or spectral distribution (these may be referred to as parameters of the light).

[0130] The evaluation unit 120 with the processor 126 ( Fig. 1 ) also receives the signals from the NIR sensor 118 and can classify the hair being examined based on these signals. In other words, the signals provided by the NIR sensor 118 are characteristic of the hair being examined. These signals can also be referred to as signal patterns and can be used to determine and output a product recommendation and / or application instructions.

[0131] It is conceivable that a product and / or an application instruction is assigned a typical signal pattern, with which the product and / or the application instruction can be sensibly applied to the hair being examined in order to achieve a desired treatment result. This assigned signal pattern of the products and / or the application instructions can be compared with the actual signal pattern from the recording unit. Once the signal pattern recorded or supplied by the spectrometer matches the signal pattern assigned to the products and / or application instructions to a certain degree, the corresponding products and / or application instructions can then be output. The signals can be examined for qualitative similarity (do the shapes or curves of the signals correspond) and / or quantitative similarity (do the signals for similar input values, i.e. light, have similar output values, i.e. emitted light).

[0132] It is also conceivable that, depending on user input, a factor is determined and applied to the signal acquired by the spectrometer before this input signal is compared with the signal patterns of the products or application instructions. This has the advantage that a correction factor can be applied to the acquired signal to improve the accuracy of the product recommendations and / or application instructions for a specific user.

[0133] Fig. 5 shows an exemplary absorption diagram 500 in a wavenumber range from 1600 cm -1< to 1720 cm -1< (wavelength range between 6250 nm and 5813 nm). Fig. 5 The wavelength range shown is above the NIR (near infrared) range and is used to understand the invention. The displayed diagram shows the absorption spectrum of hair in a mid-infrared wavelength range. The wavenumber is plotted on the horizontal axis 510, and an absorption coefficient measured as the proportion of absorbed light to emitted light (normalized to 1) is plotted on the vertical axis 520. In the aforementioned wavenumber range, the absorption spectrum 530 of the β-sheet structures, the absorption spectrum 540 of the α-helices, the absorption spectrum 550 of other randomly distributed protein fragments of the hair, and the resulting total absorption 560 are shown. The total absorption 560 results from the superposition of curves 530, 540, and 550. The qualitative shape and the quantitative absorption values ​​of curve 560 are characteristic of the degree of elongation of the hair sample.

[0134] However, detecting the absorption spectrum above the NIR range (above a wavelength of 3000 nm) can be very complex in terms of equipment. The invention therefore proposes using a near-infrared sensor that detects the absorbance of a hair sample in a wavelength range between 800 nm and 2500 nm and generates the corresponding absorption spectrum. In the wavelength range between 800 nm and 2500 nm, particularly between 2000 and 2500 nm, harmonics of the α-helices and β-sheet structures can be detected.

[0135] Fig. 6 shows, by way of example and in a qualitative manner, a stress-strain diagram 600 for human hair. The horizontal axis 610 represents the strain, and the vertical axis 620 represents the tension in the hair.

[0136] In human hair, the stretching process is completely reversible up to approximately 3% to 5% elongation (depending on the individual hair). This means that after the stress is removed, the hair quickly returns to its original length before stretching. This range is marked with 630 and indicates the range of linear elastic behavior. From approximately 10% to 15% elongation, the irreversible conversion of α-helices into β-pleated sheet structures occurs. Due to the simple conversion of the secondary structures, this overstretching requires only very low forces, as can be seen from the very slight or almost non-existent slope of the curve in the 640 range. At approximately 25% elongation, the hair breaks.

[0137] However, this transformation of the hair is undesirable from a cosmetic point of view, since the hair in the transition region 640 significantly loses its mechanical stability.

[0138] Following the 640 area, there is another area, 650, which corresponds to a further increase in stretching. Here, the tension continues to increase with increasing stretching until the hair ultimately breaks.

[0139] The analysis of the ratio of α-helices to β-sheet structures is therefore, in addition to parameters such as oxidative damage, reductive damage, moisture, and surface damage, another important parameter for the holistic assessment of hair condition.

[0140] It has now been discovered that the described overstretching of hair can be easily determined using NIR sensors by comparing the absorption spectrum recorded with the NIR sensor with the absorption spectra of a calibration model, as described above. Due to its compactness and low cost, the method is also suitable for end consumers, hair salons, and drugstores ("point of sale"). LIST OF REFERENCE SYMBOLS

[0141] 10 Analysis object 12 Area to be examined 100 Arrangement for determining hair properties 110 Detection unit 111 Surface 112 Electromagnetic waves 114 Data transmission connection 116 Light emitter 118 NIR sensor 120 Evaluation unit 122 Data network 124 Data transmission connection 126 Processor 128 Local memory 130 User interface 132 Input unit 134 Output unit 140 Data storage unit 200 Housing 210 Energy storage device 300 Data carrier 400 Process 410 - 450 Process steps 500 Absorption diagram 510 Wavenumber 520 Absorption 530 β-sheet structures 540 α-helices 550 Other protein fragments 560 Total absorption 600 Stress-strain diagram 610Stretch 620Stress 630Linear-elastic behavior, reversible region 640Transformation region of α-helices into β-folded structures 650Overstretch

Claims

1. An arrangement (100) for determining a degree of elongation of hair, the arrangement comprising: a detection unit (110) for detecting hair characteristics; an evaluation unit (120) for evaluating the detected hair characteristics and for determining the degree of elongation of hair based on the detected hair characteristics; wherein the detection unit (110) contains a near-infrared sensor, NIRS; wherein the detection unit (110) is designed to irradiate a hair sample with electromagnetic waves in the infrared range and to detect an absorbance of the hair sample in a wavelength range of 800 to 2500 nm; wherein the detection unit (110) is designed to generate an absorption spectrum of the hair sample in the wavelength range of 800 to 2500 nm and to provide the absorption spectrum to the evaluation unit (120); wherein the evaluation unit (120) is designed to compare the generated absorption spectrum with a calibration model and to determine a degree of elongation of the hair sample based on the absorption spectrum and the calibration model.

2. The arrangement (100) according to claim 1, wherein the evaluation unit (120) is designed to compare a course of the absorption spectrum of the hair sample with a plurality of absorption spectra from the calibration model.

3. The arrangement (100) according to claim 1 or 2, wherein the detection unit (110) is designed to detect or obtain a moisture level of the hair sample and to provide the moisture level to the evaluation unit (120); wherein the evaluation unit (120) is designed to take into account the moisture level of the hair sample when comparing the generated absorption spectrum with the calibration model.

4. The arrangement (100) according to one of the preceding claims, wherein the evaluation unit (120) is designed to assign a damage category to the hair sample based on the comparison of the generated absorption spectrum with the calibration model.

5. The arrangement (100) according to one of the preceding claims, wherein the near-infrared sensor is a spectrometer (118), wherein the spectrometer is designed to create a signal pattern based on the detected light, which pattern is characteristic of the detected hair characteristics.

6. The arrangement (100) according to one of the preceding claims, further comprising a housing (200) and an energy store (210), wherein the evaluation unit (120) is accommodated in the housing and the detection unit (110) is coupled to the housing, and wherein the energy store is arranged in the housing (200) in order to supply the evaluation unit (120) with energy, and to allow at least temporarily autonomous operation of the evaluation unit without said unit being connected to an external energy source.

7. The arrangement (100) according to one of the preceding claims, wherein the evaluation unit (120) is designed to compare the characteristics of treatment agents for treating hair with the detected hair characteristics and to determine an effect of the treatment agents on the hair, taking into account the detected hair characteristics.

8. The arrangement (100) according to one of the preceding claims, wherein the evaluation unit (120) is designed to transmit the detected hair characteristics to a data storage unit (140) and to request information for treating the hair according to the detected hair characteristics from the data storage unit.

9. The arrangement (100) according to claim 8, further comprising a user interface (130), wherein the evaluation unit (120) is designed to instruct the user interface to output the obtained information for treating the hair.

10. The arrangement (100) according to one of claims 8 or 9, wherein the evaluation unit (120) is designed to request information from a user and to also take this information into account when requesting information from the data storage unit (140) in order to obtain, from the data storage unit (140), characteristics of treatment agents for treating hair according to the information requested from the user.

11. A method (400) for determining a degree of elongation of hair, comprising: irradiating (410) a hair sample with electromagnetic waves in the infrared range; detecting (420) the light emitted by the hair sample; detecting (430) an absorbance of the hair sample in a wavelength range of 800 to 2500 nm; generating (440) an absorption spectrum of the hair sample in the wavelength range of 800 to 2500 nm; comparing (450) the generated absorption spectrum with a calibration model and determining the degree of elongation of hair based on the absorption spectrum and the calibration model.

12. The method (400) according to claim 11, further comprising: detecting or obtaining a moisture level of the hair sample; and referring to the moisture level of the hair sample when comparing the generated absorption spectrum with the calibration model.

13. The method (400) according to one of claims 11 or 12, further comprising: assigning a damage category to the hair sample based on the comparison of the generated absorption spectrum with the calibration model.

14. A method for determining a treatment agent based on the degree of elongation of hair determined in one of claims 11 to 13, comprising the following steps: referring to the determined degree of elongation of hair; selecting a treatment agent for hair based on the determined degree of elongation and outputting information about the selected treatment agent.

15. A computer program product which is designed to carry out the method according to one of claims 11 to 14 when said method is carried out on an arrangement according to one of claims 1 to 10.