Digital controlling system to the set of high power LEDs

Abstract

In the paper is described the concept and architecture of the multi-channel control system for set of high-power LEDs. The broadband source of radiation for prototype illuminator is dedicated to the investigation of Low Level Laser Therapy procedures. The general scheme of the system, detailed schemes, control algorithm and its implementation description in FPGA structure is presented. The temperature conditions and the opportunity to work with a microcomputer are characterized. MOTIVATION TO INVESTIGATIONTo irradiation in vitro cell lines and in vivo human organs in procedures of Low Level Laser Therapy (LLLT) are used almost exclusively semiconductor radiation sources emitting in the spectral range 600-1000nm -laser diodes and LEDs [1] -and HILT systems (High Intensity Laser Therapy). HILT produces relatively high energy/power pulse with pulse duration of about 100-200 µs and wavelength 1064 nm. Individual sources are used or their matrixes. The radiation power emitted by the individual emitter is from several mW to 500 mW, whereby the total optical power of the system is usually not higher than 2 W. Constant power density of the radiation does not exceed 100 mW/cm 2 on the surface of the object. Exposure takes place in order to stimulate tissue for positive reaction and eventually induce therapeutic effect [2][3][4]. This effect is related to the absorption of low-energy (low-power) radiation that initiates the processes in the tissue at the cellular and molecular level [5-10] without damage and without significant thermal effect (increase of body temperature is less than 1 K). The narrow spectrum of radiation allows selective excitation of specific chemical tissue substances to stimulate certain chemical processes. The cellular response is dependent on the wavelength of the radiation, the surface power density and surface energy density, exposure time and agenda, as well as the tissues type and the functional state of cells [11][12][13][14][15]. These factors determine what changes are induced in irradiated tissues.In available publications in the field of LLLT many authors show positive effects of laser radiation in variety of different diseases, some investigators found no positive effects of laser stimulation or observed negative results [16]. Lack of clear guidelines on the methodology and dosing of laser treatments may be the cause of the absence of positive therapeutic effects -delivered energy dose may be too low or too high, radiation parameters of the source selected for the treatment ineffective. Investigators state that mechanisms of interaction of laser light with the tissue, which had been not fully understood yet, do not allow to consider in reliable and irrefutable manner that biostimulation is an effective therapeutic instrument [16]. However, the vast number of reports about unambiguous therapeutic effects obligates to undertake research into their explanation and settlement the selection of procedure parameters. Without scientific verification of LLLT influence on lived cell lines and clinic...

Therapeutic and diagnostic set for irradiation the cell lines in low level laser therapy

“…The use of this property and the effect of the development of semiconductor radiation sources -the emergence of high power LEDs in a wide spectral range of red and near infrared (NIR) light -enabled the development of the broadband source with a continuous spectrum [5,28,29]. The broadband source realization is based on summation of individual spectral distributions of 31 LEDs, and use the mechanism of independent regulation their currents [30]. Illuminator is characterized by spectral power density of radiation at level of 10 mW/nm in the entire aforesaid spectral range, and its low volatility, Fig.…”

“…2. Each LED has its own independently controlled analog controller/power supply [30][31][32], controlled digital signal from the FPGA, enabling a broad regulation of emission spectral characteristics of illuminator. Power supply system for each LED has been designed on the basis of DC current amplifier DD311 with 100-fold current amplification up to 1000 mA.…”

“…The emission spectrum of LED illuminator The driver and broadband illuminator system includes[30] (Fig. 3): the set of high power LEDs (LED 1 ...…”

Optoelectronic set for measuring the absorption spectrum of the thin biological media

“…Radiation sources are powered in the way that provides variable value of its optical power. The control system and broadband illuminator [32] (Fig. 1 and 2) includes: a set of high power LEDs (LED LED 1 ... n), the analog controllers module (Driver Driver 1 ... n), the digital controller FPGA, transmission protocols converter FTDI and microcomputer.…”

“…Analog drivers provide the required output power for the whole set of LEDs. Each driver module produce output current whose intensity is proportional to the optical power of individual LEDs [32,33]. It is possible to wide regulation the emission spectral characteristics of illuminator.…”