Most physical and chemical experiments can be described with a finite number of rules. In physiological processes, everything can be tied to the laws of nature. A good model can be a guideline for new experiments. Usually, the model and experiment have an iterative connection. To understand how to investigate any material, there is a model needed (block 1). First, we need an abstract understanding of what we are investigating (block 2). Abstracts are transformed into mathematical models (block 3). There we can use formulas and solve them using the computer. The results you get shows, what experiments have to be done, and what to expect from them. This loop system is resistive to irregularities in the mathematical model. In other words, this is the purifier of experiments and models.
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 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.
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: