LED irradiance pattern at short distances

Moreno, Iván

doi:10.1364/ao.59.000190

Cited by 14 publications

(5 citation statements)

References 18 publications

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“…Equation (6) describes the irradiance

in W/m 2 of a square LED at a distance

in any point at xy [ 31 ]:

where

is the flux in Watts,

is the length of the LED,

is the width and

is the distance away from the LED emitting surface. Figure 5 shows the LED irradiance at the surface with a 1 mm 2 area away from the LED at different distances.…”

Section: Functional Principle and Designmentioning

confidence: 99%

Design and Modeling of Fiber-Free Optical MEMS Accelerometer Enabling 3D Measurements

2022

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Optical accelerometers are popular in some applications because of their better immunity to electromagnetic interference, and they are often more sensitive than other accelerometer types. Optical fibers were employed in most previous generations, making micro-fabrication problematic. The optical accelerometers that are suitable for mass manufacture and previously mentioned in the literature have various problems and are only sensitive in one direction (1D). This study presents a novel optical accelerometer that provides 3D measurements while maintaining simple hybrid fabrication compatible with mass production. The operating concept is based on a power change method that allows for measurements without the need for complex digital signal processing (DSP). Springs hold the proof mass between a light-emitting diode and a quadrant photo-detector, allowing the proof mass to move along three axes. Depending on the magnitude and direction of the acceleration affecting the system, the proof mass moves by a certain amount in the corresponding axis, causing some quadrants of the quadrant detector to receive more light than other quadrants. This article covers the design, implementation, mechanical simulation, and optical modeling of the accelerometer. Several designs have been presented and compared. The best simulated mechanical sensitivity reaches 3.7 μm/G, while the calculated overall sensitivity and resolution of the chosen accelerometer is up to 156 μA/G and 56.2 μG, respectively.

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“…Equation (6) describes the irradiance

in W/m 2 of a square LED at a distance

in any point at xy [ 31 ]:

where

is the flux in Watts,

is the length of the LED,

is the width and

is the distance away from the LED emitting surface. Figure 5 shows the LED irradiance at the surface with a 1 mm 2 area away from the LED at different distances.…”

Section: Functional Principle and Designmentioning

confidence: 99%

Design and Modeling of Fiber-Free Optical MEMS Accelerometer Enabling 3D Measurements

2022

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“…We assume now the light source has a Lambertian emission pattern, i.e., its radiance L t is constant across locations on the transmitter surface. In this case, the integral in ( 15) has analytical solutions which can be obtained either by direct integration or by changing the surface integral into a contour integral in an R 3 space by applying the Stokes theorem [14], [20]. Here, we present the contour's integral method as we consider the integration conditions make the procedure simpler.…”

Section: Model For a Non-tilted Light Source And A Tilted Receiver A General Expression Of Irradiance For A Planar Sourcementioning

confidence: 99%

“…It is important to mention that we can derive the solution proposed in [14] for a receiver placed at a vertical distance z = −h from the transmitter and pointing toward the ceiling with a fixed orientation n r = [0, 0, 1] R from (20).…”

Section: B Case Of a Planar Rectangular Light Sourcementioning

confidence: 99%

“…In such cases, a more suitable model is therefore required. In [14], Moreno recently proposed a model of the irradiance of extended light sources and validated its relevance by comparing it with irradiance readings of real LEDs. This model is, however, only given in the case of a receiver whose sensitive surface is parallel to the emission surface of the transmitter.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Full Field Radiant Flux Distribution of Multiple Tilted Flat Lambertian Light Sources

Valencia-Estrada

Bechadergue

García-Márquez

2020

IEEE Open J. Commun. Soc.

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The emergence of visible light communication (VLC) as a subset of optical wireless communication (OWC) in the early 2000s has turned any light-emitting diode (LED) source into a potential data transmitter. The design process for any VLC or OWC system typically involves a link budget analysis performed by studying the signal-to-noise ratio (SNR) at the receiver. Since this SNR strongly depends on the radiant flux collected by the receiver, an accurate model for this parameter is required. The point-source model has been widely used since 1979 and generally provides a good approximation of the received radiant flux. However, it might be less accurate for typical extended lighting sources like LED panels or large-area organic LEDs. In this paper, the radiant flux distribution of flat Lambertian rectangular or circular sources is derived from a vector analysis of their irradiance. It is then validated through actual measurements in the case of a circular source. The resulting extended-source models thus better capture the light beam pattern of such transmitters to enable a more accurate link budget. It provides at the same time almost identical results to the point-source model for small sources and can, therefore, be seen as a natural extension of this already widely used model.

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“…[20] While light uniformity can be improved by increasing vertical distance, the optical power density at the skin surface is significantly reduced by the long radiation distance and severe diffuse reflection. [21,22] Some researchers reported that only 10% of incident light could penetrate into a skin model when irradiated with a 630 nm light source at 2 cm distance. [23][24][25][26][27][28] In addition, excessive light exposure to compensate distance-induced optical loss can give rise to adverse effects related with thermal damages such as increased melanin production, low temperature burns, and eye damage, as displayed in Table S1B, Supporting Information.…”

Section: Introductionmentioning

confidence: 99%

Wearable Surface‐Lighting Micro‐Light‐Emitting Diode Patch for Melanogenesis Inhibition

Lee

Ahn

Lee

et al. 2022

Adv Healthcare Materials

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Wearable light‐emitting diode (LED)‐based phototherapeutic devices have recently attracted attention as skin care tools for wrinkles, acne, and hyperpigmentation. However, the therapeutic effectiveness and safety of LED stimulators are still controversial due to their inefficient light transfer, high heat generation, and non‐uniform spot irradiation. Here, a wearable surface‐lighting micro‐LED (SµLED) photostimulator is reported for skin care and cosmetic applications. The SµLEDs, consisting of a light diffusion layer (LDL), 900 thin film µLEDs, and polydimethylsiloxane (PDMS), achieve uniform surface‐lighting in 2 × 2 cm2‐sized area with 100% emission yields. The SµLEDs maximize photostimulation effectiveness on the skin surface by uniform irradiation, high flexibility, and thermal stability. The SµLED's effect on melanogenesis inhibition is evaluated via in vitro and in vivo experiments to human skin equivalents (HSEs) and mouse dorsal skin, respectively. The anti‐melanogenic effect of SµLEDs is confirmed by significantly reduced levels of melanin contents, melan‐A, tyrosinase, and microphthalmia‐associated transcription factor (MITF), compared to a conventional LED (CLED) stimulator.

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LED irradiance pattern at short distances

Cited by 14 publications

References 18 publications

Design and Modeling of Fiber-Free Optical MEMS Accelerometer Enabling 3D Measurements

Design and Modeling of Fiber-Free Optical MEMS Accelerometer Enabling 3D Measurements

Full Field Radiant Flux Distribution of Multiple Tilted Flat Lambertian Light Sources

Wearable Surface‐Lighting Micro‐Light‐Emitting Diode Patch for Melanogenesis Inhibition

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