| 摘要 |
PURPOSE:To effectively condense sunlight on a heat collecting part and to improve the function of the titled device in a short focal distance by constituting the device in order that a 1st refraction planes of a Fresnel lens which satisfies a prescribed initial conditional formula are continuously linked. CONSTITUTION:A light beam 1 and a light beam 2 respectively having + or -thetam angle from a direction perpendicular to a fine prism P on a position XY are respectively made incident on a point B and the point A on an X axis and an incident light beam is certainly male incident between A and B if a prism inclination angle pi and the angle lambda of a 2nd refraction plane P2 are obtained. When it is supposed that the distance between the central point C1 of the Fresnel lens and the X axis is a focal distance F, a calculating formula is obtained as initial conditions X0 and Y0. The device is designed in order that a 1st refraction plane P1 is continuously linked on this condition and if it is used by combining with a vacuum-tube type heat collecting unit, the sunlight can be effectively condensed on the heat collecting part without following up it if the sun is in an allowable incident angle and it blocking loss is improved in a short focal distance so as to improve the function.
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