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Introduction To Optical Sensors, The Difference Between Them And Fingerprint Sensors

Introduction To Optical Sensors, The Difference Between Them And Fingerprint Sensors

September 20 , 2023 0

Since fingerprints have the unique characteristic of being unchanged for life, and the fingerprints of different users are different, with the continuous development of information technology, fingerprint recognition technology has been widely used, and it is commonly used in a variety of fields, such as identity authentication.
The fingerprint recognition components in the current terminal may include: fingerprint sensor, the fingerprint sensor should try to avoid the occurrence of false contact, which means that although the object is in contact with the fingerprint sensor, the fingerprint sensor is unable to recognize the fingerprint. Typically, the higher the sensitivity of the fingerprint sensor, the higher the probability of detecting a false touch, and the lower the sensitivity of the fingerprint sensor, the lower the probability of detecting a false touch, but there is a possibility that the fingerprint may not be detected. Therefore, the terminal should complete the debugging of the sensitivity of the fingerprint sensor before leaving the factory, so that the fingerprint sensor can be recognized in every fingerprint identification and avoid false touches.
However, the sensitivity of the fingerprint sensor in the terminal after delivery is fixed, and the flexibility of the fingerprint sensor in recognizing fingerprints is relatively single.

Method, Device, And Storage Medium For Controlling A Fingerprint Sensor And Process

By using the fingerprint sensor module shown below you can make fingerprint recognition easier to implement and easier to add to your project. This means that fingerprint capture, enrollment, comparison and search are very easy to implement.

These modules come with FLASH memory for storing fingerprints and can be used with any microcontroller or system with a TTL serial interface. These modules can be added to security systems, door locks, time and attendance systems and more.

Understanding Capacitive Fingerprint Sensors

Unlike optical fingerprint sensors that create a fingerprint image, capacitive products use an array of micro-capacitor circuits to collect data. When a finger is pressed onto the collection surface, the ridges and valleys of the finger create different tiny capacitances between the epidermis and the chip. The chip measures the different electromagnetic fields in the space to get the complete fingerprint information, which is processed by the op-amps and ADCs. For example, R502/R503 can recognize both dry and wet fingerprints, while the former is lighter.
Taking R503 as an example, the sensor is embedded with fingerprint recognition algorithm and protocols, with functions of fingerprint acquisition, comparison, search and template storage, etc. R503 has an image size of 192*192, a resolution of 508 DPI, 200 fingerprints can be stored, FRR ≤ 0.01%, FAR ≤ 0.00001%, and supports Arduino, Android, Windows R503 supports Arduino, Android, Windows, Linux, etc.

R503 supports low power consumption finger detection, operating voltage 3.3V, acquisition current no more than 18mA, average standby current is only 2uA.R503 through the RS232 UART interface, the communication rate up to 57600bps, used for computer peripherals, fingerprint door locks, fingerprint padlocks, safes and so on.

Basic Classification of Optical Sensors

Optical sensors mainly include colorimetric sensors, fluorescence sensors, chemiluminescence sensors, Raman scattering sensors, surface plasmon resonance sensors and so on. Due to the convenience and low cost of colorimetric and fluorescence analysis techniques, they are now the two most commonly used types of optical sensors.

Colorimetric Sensor

The colorimetric sensing technique% is used to determine the UV-visible absorption spectrum of the sample to be tested in the range of 200-800 nm by means of a UV-visible spectrophotometer only. Changes in the UV-visible absorption spectra of the samples to be measured are measured by a UV spectrophotometer only, and qualitative and quantitative analyses of the target %are achieved based on the Lambert-Beer law%(Lambert-Beer).9 Alternatively, colorimetric analyses of the target %can also be carried out by the color change of the solution that is visible to the naked eye. Colorimetric sensors based on detecting changes in the absorption spectra of the system with the advantages of visualization only, fast analysis, low cost, real-time monitoring, and no need for complex equipment have achieved remarkable development

Fluorescence Sensor

Fluorescence is a photoluminescence cold luminescence phenomenon, usually refers to the material molecules in the absorption of short wavelengths (such as ultraviolet or X-rays) of light energy into the excited state, and immediately de-excited and emit light longer than the original wavelength. The principle of luminescence is that when the light irradiation to some atoms, the light energy to make the nucleus around some of the electrons from the original track jump to the orbit of higher energy, that is, from the base state jump to the first excited single-line state or the second excited single-line state and so on. The first excited single-wire state or the second excited single-wire state, etc. are unstable and will immediately return to the ground state. When the electrons return to the ground state from the first excited single-wire state, the energy is released in the form of light, which becomes fluorescence. Fluorescence analysis is the qualitative and quantitative analysis of a substance to be measured by determining its excitation and emission wavelengths and detecting changes in the fluorescence intensity signal. Compared with other analytical methods, the fluorescence detection technology constructed according to the characteristics of fluorescent substances and their diversity has the following significant advantages: (1) high sensitivity, compared with the colorimetric method, incandescent light sensing method is usually 2-3 orders of magnitude higher sensitivity; (2) strong selectivity, low background signal; (3) simple operation, low sample dosage, fast response speed.