There was a time when all IC’s were only TTL type. They were marked as 74LS or 74ALS. But then there came CMOS types of semiconductors. They are usually marked CDxx. And lately, there appeared combined semiconductors that are compliant with both types. They usually are marked as 74HC or 74HCT.TTL is faster than CMOS, but they sink more power. They are powered from a 5V source. To diminish the power consumption, the CMOS was developed. They can work with supplied voltages in the range of 3 to 15V. The main disadvantage is that they are static sensitive. So you always have to be grounded when working with CMOS.Now both types of semiconductors are widely used. Sometimes there is a dilemma to connect TTL to CMOS. You cannot connect TTL directly to CMOS as there are different supply voltages. So it would help if you had some compliance circuit. The simplest can be bipolar transistor cascade. Just remember that such a cascade inverts the signal, so you might need to put an inverter in front of CMOS. Another reminder – never leave TTL or CMOS free pins hanging. Jus connect them through a resistor to VCC or GND.
I found Matlab to be a convenient tool that easily traces the boundaries of objects in a picture. So I adopted it to skin lesions. This can be used to automatically detect skin irregularities and calculate lesion properties like the asymmetry of shape, or border irregularities, which can help detect melanoma. There are numerous investigations done, so I only put a few examples of how it looks. I will give you my source code so that you can try it on your own. Look at my results: 1) And it also finds the center of mass:
There are many skin image capture methodologies developed and used. Here is a short review of them: Dermatoscopic photography The deepest layer of skin can be reached – Papillary dermis Resolution – depends on the optical system View of skin – Horizontal The main disadvantage is reflections of light from skin surface – stratum cornea.
I used a simple lamp directed to the glossy table surface. One polarizer is in front of the lamp, and the other is in front of a digital camera lens. Both polarizes perpendicularly oriented to each other. How does this work? A theory about an angle on which the incident polarized electromagnetic waves turn reflects from the surface with a polarization plane turned in 90 degrees. When light going through the polarizer towards the surface, the light is polarized in one direction, and when it reflects from the surface, it is turned by 90 degrees. Another perpendicular polarizer filters those waves in front of the lens.
Let’s make a filter, which filters off the 60Hz frequency from the ECG signal. As we know, the American power supply is 60Hz. This is a common noise in biomedical signals while the industrial power supply powers them. This type of noise can be defined easily and can be filtered as parameters of noise are known.Here is one example of how to implement an FIR filter using mathematical tools, like Matlab. This can be done using a microcontroller, like ARM or even AVR, because the frequencies are up to 1 kHz.Initial conditions: f0=60Hz – power supply frequency;fs=500Hz – sampling rate;frequencies who define complex zeros: we get w0=0.754;Positions of complex zeros: Zeros and poles in z plane System Function From it we can calculate filter coefficients: And filter coefficients: b3 = 1; b2 = -2cos(w0); b1 = 1 Also we know that: And here we get filter characteristics: We have a band stop filter at 60Hz, and its jam at 60Hz is -300dB. Bellow is a filter structure: Now using this filter we can filter ECG signal: As you can see, this is a simple FIR filter. In other words, there is nothing more than an average function that doesn’t need…
To evaluate skin pigmentation in different skin layers, a special light adapter is needed to take multispectral pictures of the skin. As there are different optical properties of skin pigments, four different light sources have been chosen. blue λ= 470 nm – highly absorbed by epidermal melanin green λ= 576 nm – hemoglobin peak red λ= 660nm – epidermal-dermal boundary IR λ= 865 nm – low absorption, sensitive to scattering to measure papillary dermis thickness. There was a lighting source for the “Nikon Coolpix E3100” digital camera developed to take multispectral images of skin. Making an adapter The drawing of lighting adapter The lightning adapter isn’t tough to build. It would help if you made a circular PCB and solder LEDs with protective resistors. The PCB image:
Understanding how light interacts with skin can assist in designing physics-based dermatological image processing. The key is to understand how light interacts with skin tissue. The skin consists of different layers with different spectral properties. When the incident light is applied to the skin layer, it is absorbed, and another part is scattered. The main layers of skin are as follows: Stratum cornea practically doesn’t absorb light but diffuses it; Epidermis consists of cells producing the pigment melanin. Melanin strongly absorbs light wavelengths towards the ultraviolet part; Dermis is next to the skin layer, consisting of collagen fibers. It can be split into two sublayers: The papillary dermis and the dermis itself. The papillary dermis consists of a high density of collagen fibbers who are strong scatterers of light. The primary requirement for the model is that light has to be scattered. Stratum cornea is supposed a scattering filter. Skin can be characterized as follows:
Skin is a brilliant structure of our body. It is very elastic and pretty strong to protect internal tissue. It also acts as a thermoregulator of our entire body protecting us from overheats when we sweat and when there is cold, the blood flow is reduced to skin tissues to save heat to the body’s inner organs. Skin is pretty resistant to harmful chemicals, microorganisms, and if dry, it has high electrical receptivity. From the biochemical side, the skin can produce vitamin D when exposed to sunlight, which is essential for our bones’ growth and maintenance. The extensive network of nerves within the skin feeds information continuously to the brain concerning our surroundings. So it is full of sensors to know the external world like temperature, pressure. Don’t even let me start about skin importance in the fashion industry. About how much there is the attention paid to cosmetics, beauty shine. Skin can show you if you’re shy or cold, or afraid. As you see, your body’s top layer of skin can tell you so many things; get to know it. Skin structure diagram Mainly people used to name only two layers of skin epidermis and dermis. But in reality,…