Therefore, we did not apply this technique either.
#Zemax download volume dectortor skin
Representing all the individual blood vessels in the skin would require the addition of several hundreds of objects with the complex spatial arrangement, and would reduce the generality of the model, thus this type of modelling is not widespread in the literature. Therefore, if more accurate data are available for your specific applications, then do not hesitate to customize the model accordingly! Thus, different parameters might be required for specific subject groups. Although the model parameters were based on published data, it is important to note that the optical parameters of the human skin may vary significantly across the population. This solution ensured that the layers were located closely one after the other without any gap between them.Īs this case study relies solely on data published in the literature, we did not carry out any new measurements throughout the research process. The subsequent layers were placed by using the previous layer as Reference Object and applying Pickup solve on the Z Position value from the Z Length column of the previous layer. The thickness values of the layers were based on literature data, and the cross-sectional size was determined in such a way that there is no light leakage at the sides. Finally, similarly to most of the published skin models, we represented the subcutaneous fat with one single layer too.Īll the above-mentioned layers are modelled as Rectangular Volumes in OpticStudio.
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On the other hand, as there is no blood content in the epidermis - to keep the model simple - we decided to use only one thick epidermis layer, which accounts for all the stratum corneum, stratum granulosum, stratum spinosum, and stratum basale. Therefore, we separately modelled the sub-layers of the dermis with different blood content values, namely the papillary dermis, subpapillary dermis, upper blood net dermis, reticular dermis, and deep blood net dermis. As the primary goal for this use case was to simulate a PPG-based heart rate sensor, where the key point is to measure the changes caused by the pulsation of the blood, we focused on accurately modelling the layers where this pulsation can be observed. To simulate light transport in tissue media, we implemented a layered skin model, which accounts for the epidermis, the dermis, and the subcutaneous fat.
#Zemax download volume dectortor how to
This feature is available in the Premium edition of OpticStudio, and the process is discussed in detail in the knowledgebase article How to generate a ray set from an RSMX Source Model. The model of this LED can be directly downloaded from the Radiant Source Models library, and a Source File can be created by generating rays from the Radiant Source Model file. As a result, we chose the modelling wavelength of 575 nm, and we used a QSMF-C160 LED (Avago Technologies) as the source. Thus, we intended to apply a wavelength at which the optical parameters of both the skin and the blood are widely available in the literature, and which is also close to the most frequently used wavelengths in commercial devices. Our goal was to develop a realistic skin model based on data published in the relevant literature. In this example, we present a reflection PPG device. On the other hand, infrared and near-infrared wavelengths are better suited for measurements of deep-tissue blood flow and can be used in transmission mode as well. As the penetration depth of the light depends on its wavelength, green and yellow LEDs are most suitable to take measurements in the superficial blood flow and are typically used in reflection mode. PPG sensors can be used either in reflection or in transmission mode. In this blog, we will explore how to implement a human skin tissue model in OpticStudio and how to simulate the measured signal of a PPG device over time using a ZOS-API application. Therefore, the pulsation of blood causes a variation of the opposite phase in the signal of the detector. Light is more strongly absorbed and scattered by blood than by the surrounding tissue.
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They provide a simple optical technique to detect blood volume changes in tissues.
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PPG devices consist of infrared or visible range light-emitting diodes (LEDs) and photodetectors. This blog post demonstrates how to model the human skin in OpticStudio for physiological measurements and illustrates a time-dependent simulation of PPG-based heart rate sensors using ZOS-API. One of its most widespread applications is the wearable heart rate sensor included in commercially available smartwatches and sports bracelets, that provides comfortable and continuous pulse monitoring during everyday tasks. Photoplethysmography (PPG) is a low-cost, non-invasive optical technology that takes physiological measurements on the surface of the skin.