MEP 2006, 7-11 November 2006, Guanajuato, Guanajuato, México.
A SEMI-SPHERICAL IRRADIANCE PROFILES METER USED AS A QUALITY CONTROL DEVICE A. Gonzalez-Roman1, M. Tecpoyotl-Torres,1 J. Escobedo-Alatorre1, S. Pal-Verma,2 M. Torres-Cisneros and J. Sánchez-Mondragón3 1
Research Centre of Engineering and Applied Sciences (CIICAp) Autonomous State University of Morelos (UAEM) 62209, Av. Universidad No 1001, Cuernavaca, Mor., Mexico, e-mail:
[email protected] 2 Centro de investigación en Energía, 62580, Temixco, Mor. 3 National Institute for Astrophysics, Optics, and Optics (INAOE) 72000, Luis Enrique Erro #1, Tonantzintla, Pue. Mexico Abstract- The design of a semi-spherical irradiance profile detector (SD) is shown. With this device, we obtain the distribution of illumination due to punctual sources in the visible range. This meter can be also used as quality control device for lamps and bulbs. We are interested in the distribution of the irradiance, instead of the total irradiance over a complete region, which is the information given by spherical meters, such as the Ulbrich spheres. The obtained discrete profiles corresponds to the irradiance, as equivalent to the voltage intensity detected in semispherical detector basic sensor. These voltage values permit us to obtain the corresponding profile to each source and give as the capability to chose the better sources for specifics tasks. Keywords: Detectors, Labview, Amplification, optical range.
INTRODUCTION The knowledge of the irradiance profiles of a point like or spherical source is one of the most practical and interesting problems in many fields that includes science and engineering. There is a close relation between the interfereometric problem in a circular pupil, functionally described by the Zernike polynomials, with that one that corresponds to a spherical problem and the spherical harmonics. In the first one, the coefficients of these polynomials have a physical meanings, expressed as Seidel´s aberrations. The spherical problem does not have a technological solution based on spherical CCDs (Coupled-Charge Devices), because there are not spherical CCDs. On the other side, the Light Emitting Diodes (LEDs) may convenientle be used as emitters or detectors with a convenient spectral wide, that allows us to determine, under a low cost way, the illumination characteristics of the sources.
DATA ANALYSIS We use a semi-sphere, Θi = 0 and Θf = π/2; where the sine and cosine are mono-valued functions of θ. This stablish a direct mapping on its projection, as it is shown in figure 1.
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Figure 1: Projection of the sphere over a circular plane.
Figure 2: Experimental data
Figure 3: Fitted data using Zernike polynomials
1-4244-0628-5/06/$20.00 ©2006 IEEE
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As can be noticed, the angle θ determines uniquely the projection on the unitary circle, the magnitudes of the coordinates x, and y; and the angle φ gives us the corresponding quadrant and given by: x = senθ cos φ and y = senθ senφ . The analysis of the corresponding data fitting has been considered [1]. We realize a projection of the semi-sphere with a uniform distributed data set in order to show the data fitting, with the diffuse lamp data (Diffuse reflector par 38. 150 PAR/FL), figure 2. The obtained results were obtained using up to fourth grade Zernike polynomials. The fitted data are shown in figure 3, over the projection.
METER DESCRIPTION The meter is conformed by the following parts: an arrangement of semi-spherical detectors, a signal conditioner circuit, and an acquisition card, for visualize the generated data using a program developed in LABVIEW. We characterize the sensitivity of the detector (LED, E5/AMB-C) from 350 up to 900 nm, using an I-V converter arrangement and a monochromator ACTON 300, and we obtain a maximal answer at 570 nm (figure 4). GND -9V
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Figure 5: Signal conditioner circuit.
Figure 6: Photograph of the semi-spherical arrange
A multiplexing stage was necessary because the number of detectors (61) is larger than the number of the analogical inputs (16) of the used acquisition card (PCI-MIO-16E-1 of National Instruments). The data collection rate was of 1.25/16 MS/s. Each of the 8 conditioner cards is formed by the amplification and the multiplexing circuits, as can be seen in figure 5. The meter was realized on a cardboard semi-sphere. A metallic hollow cubic structure was made to support and to avoid deformation of the semi-sphere. The 8 conditioner cards were placed on its base (figure 6). The data collection is realized by the acquisition data card and displayed using a program realized in LABVIEW.
IRRADIANCE BUBBLE PROFILES The polynomial description [2] is clear, from an analytical point of view, but hardly informative from a technical point of view, where the uniformity is much more infromative. Then, we have found as convenient illumination that corresponds to spots diagrams, where the spot diameter is proportional to the intensity voltage detected in each sensor. In figures 7 and 8, the data of two illumination sources for home light bulbs are shown. From these figures, the source recommended for uniform illumination is the saver energy lamp, in accordance with the proofs realized by the labs of PROFECO, Mexico, which qualified it as Very Good Source, with a high efficiency (delivered luminosity, consumed energy).
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MEP 2006, 7-11 November 2006, Guanajuato, Guanajuato, México.
SEMISPHERICAL DETECTOR USED AS A QUALITY CONTROL DEVICE We use the SD to obtain the irradiance profiles of several samples of the different source in order to determine the variation among the characteristics of the similar products in the market. The analyzed sources were: Softone yellow lamp, 60 W and Phillips home reflector, 75 W (figures 9 and 10, respectively). The reproducibility data obtained from three separate tests for each case showed that most measurements were on the average within 0.003 to 0.05%. A statistical analysis of the measured intensity data was also carried out. The data for a Softtone yellow lamp of 60 W seemed to be normally distributed and the Philips home reflector of 75 W showed a bimodal distribution. 1.5
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Figure 7: Irradiance profile of a light bulb (white light. 100W 127V). 1.5
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Figure 10: Irrandiance profiles of 3 Phillips home reflector, 75 W
CONCLUSIONS The irradiance measurement on a circular pupil finds in the Zernike polynomials not only as a suitable base, but also as an efficient and informative description. We have adequated the use of this base to the measurement of the irradiance patterns produced by the semi-spherical detector, in spite that its 3-dimentional nature is technically more complex and where does not exist other option different to the detection on a discrete set of points, that is a convenient technical description.
ACKNOWLEDGEMENT I. A. Gonzalez Román would like to express their appreciation to the support from the National Council and Technology (CONACyT) of Mexico, for his graduate scholarship.
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MEP 2006, 7-11 November 2006, Guanajuato, Guanajuato, México.
REFERENCES 1. M. Tecpoyotl-Torres, J. Escobedo-Alatorre, I. GonzálezRomán, J. Sánchez-Mondragón, E. Rivera-Partida y C. TrejoLeyva. Medidor semi-esférico de perfiles de irradiancia. XVIII Reunion Anual AMO. Guad. Jal. Octubre 2005. Óptica2005 CF-03-1 -9 2. Eider Emmir Rivera Partida. Método para caracterizar perfiles de radiación en base a polinomios ortogonales. Bachelor Thesis CIICAp-INAOE-Instituto Tecnológico de los Mochis. May 2005.
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