Patent Number: 047476451
Section: description

DETAILED DESCRIPTION FIG. 1 illustrates the filter characteristics of three commercial UV filters 1, 2, 3 and the filter characteristics of three commercial IR filters 4, 5, 6. The transmissivity of the filters is indicated on the ordinate in percent of transmission of radiation, in dependence on wavelength in nm. The typical characteristics 1, 2, 3, for UV filters, show that the flanks are steep and comparatively stable in the UV range. For IR radiation, the curves 1, 2, 3 coincide and the IR radiation can pass essentially unhindered, as shown by the line 7 in FIG. 1. In contrast to the behavior of the UV filters, the IR filters, the characteristics of which are shown at curves 4, 5, 6, do not vary short-wave radiation; rather, the transmissivity of the IR filters ends in a median UV range, as shown by the circle-chain 8 in FIG. 1. Thus, the IR filters also have some UV filtering effect which, however, is not stable. The arrangement in accordance with the present invention, in its preferred form, is shown in FIG. 2. The sample S is indicated only schematically, for example a cylindrical support carrier on which paint can be applied, fabric stretched, or the like. The spacing between a central source of radiation 9 and the sample S is not to scale, and would be substantially greater than shown in FIG. 2. The sample S is merely shown for comparison purposes. The radiation source 9, centrally located in the apparatus, is, preferably, a xenon lamp. It is surrounded by outer filters and mirrors, located in a square configuration. Each side of the square surrounding assembly is subdivided into two sections. The radiation passes through the respective sides--as will appear in greater detail below, through one section having a UV filter 10 and a second section having a first mirror-filter combination 11. Each one of the first mirror-filter combinations 11 includes a UV mirror 12, having a mirror surface facing the radiation source 9. Congruent with the mirror 12, and at the outside thereof--with respect to the source 9--is a IR filter 13. Filter 13 and mirror 12 form one combination. The UV mirror 12 and the IR filter 13 can be placed adjacent to each other, that is, flat against each other or, as shown in the figure, may be spaced slightly from each other. Suitable holding means and support structures have been omitted from the drawing for clarity, and may be of any suitable construction. In accordance with a feature of the invention, a second mirror-filter combination 14 is provided, located within the outer filters 10 and mirror-filter combinations 11. The second mirror-filter combination 14 is a sandwich construction of three elements, namely an inner UV mirror 15, having a mirror surface directed towards the source 9; an outer UV mirror 16, having a mirror surface directed outwardly; and an intermediate IR filter 17, located between the UV mirrors 15,16. The UV mirrors 15,16 and the IR filter 17 are congruent, for example forming a surface-engaged sandwich. The outer UV filter 10 and the first mirror-filter combination 11 have such a length that they subdivide each side of the rectangular apparatus into two sections of equal length. The second mirror-filter combination 14 extends from the median point of any side of the apparatus, that is, from a line between the transition zone of UV filter 10 to the first mirror-filter combination into the interior space of the apparatus in such a manner that an angle of approximately 50.degree. is formed between the second mirror-filter combination sandwich 14 and the UV filter 10. The angle is shown at 18 with respect to the lower-left mirror-filter combination 14 only, for simplicity of the drawing. The angle is not critical, and has to be matched to the particular configuration of the section involved, and may vary between about 45.degree. and 80.degree., as will appear. The second mirror-filter combination 14 has such a length that the outer UV filter 10, with which it is associated, is entirely within the optical shadow of the second mirror-filter combination 14 with respect to radiation from the source 9. This means that the second mirror-filter combination 14 must extend beyond a connecting line from a corner of the UV filter 10 to a line tangential with the radiation source 9, as shown by chain-dotted line 19 in FIG. 2. OPERATION AND PATHS OF RADIATION The entire radiation emitted from the source 9 first impinges on one of the UV filters 12 or 15 of the first or second mirror-filter combination 11,14, respectively. To illustrate the radiation, three selected beams 20,21,22 are shown in the upper portion of the apparatus of FIG. 2. Beam 20 is so selected, that it first impinges on the inner UV mirror 15 of the second mirror-filter combination 14 in the lower right quadrant of the apparatus. The UV portion is reflected, while the IR portion of the emitted radiation is filtered by the IR filter 17 forming the center part of the sandwich 14. The IR portion of the radiation then is transmitted in form of the beam 20' through the UV filter 10. The UV portion of the beam 20 is reflected by the inner UV mirror 15 of the second mirror-filter combination on the UV mirror 12 of the first mirror-filter combination in the upper-right quadrant of the apparatus, and is emitted through the UV filter 10, as seen at the upper-side of FIG. 2. The UV filter 10 filters the reflected UV beam in desired manner, in accordance with the selected filter. The second mirror-filter combination, by being spaced from the right outer first mirror-filter combination 11, forms a window between the first and second mirror-filter combination. Consequently, beam 20, after dual reflection on the UV mirrors 15 and 12 can pass through the UV filter 10. The window is shown at 23 in FIG. 2. Beam 21 is reflected only once; a single reflection on the UV mirrors 15 is sufficient to pass beam 21 from the radiation source 9 to the UV filter 10, for filtering therein. The IR portion of beam 21 is filtered by the IR filter 17 in the upper-right quadrant and passes straight out through the UV filter 10 at the upper-right quadrant as beam 21". Beam 22, similarly, is separated by the first mirror-filter combination 11 into its UV and IR components, leaving through the IR filter as beam 22', whereas the UV component thereof is reflected by the mirror 12 at the upper-left quadrant, reflected again by the UV mirror 16 at the upper-left quadrant and leaving the apparatus as beam 22 through the UV filter 10 at the upper-left quadrant of the apparatus. The system can easily be changed by forming the structures not as a rigid square, but, rather, permitting the elements to change, for example to pivot along the horizontal and vertical diammetrical lines--with respect to FIG. 2--to form, selectively, an octagon or a square. The octagonal configuration is shown in broken lines, and either arrangement may be used, as desired, and, for example, the respective sections of the structure can be connected by hinge joints for selective positioning in accordance with a square or an octagon. The arrangement in accordance with FIGS. 3 to 6 are based on the same principle and, essentially, have the same elements already described, and thus will be provided with the same reference numerals incremented by a "hundred" digit corresponding to the drawing number. The sample S is not shown in the other drawings for simplicity, and can be placed as shown, for example, in FIG. 2, that is concentric to the center of the light source 9. EMBODIMENT OF FIG. 3 An equilateral triangle having three mirror-filter combinations 314 positioned in the interior thereof. The respective separation of the irradiation emitted from the light source to separate UV radiation from the IR component passing through the filters is similar to that described in connection with FIG. 2. FIG. 3 also illustrates the outer UV filter 310, and the first mirror-filter combination 311, in which the mirror element 312, and the filter element 313 are engaged against each other, that is, not spaced as shown in FIG. 2. EMBODIMENT OF FIG. 4 The general arrangement is similar to that shown in FIG. 2, except that the second mirror-filter combination 414 is divided into two portions 25,26 which, with respect to each other, are located in an essentially V-shaped arrangement, having a tip which touches the outer UV filter 10 at the apex of the V. The IR filter 27 is located between the UV mirrors at the outside of the sandwich. In the arrangement of FIG. 4, windows 23' and 23" are formed between a portion 25 of one mirror-filter combination 414 and the portion 26 of an adjacent mirror-filter combination 414, as seen at the lower-right quadrant in FIG. 4. The reflected UV radiation can thus pass through the UV filter 10, as shown by beams 421' and 421". The combination 411 formed of elements 412 and 413 corresponds to the combination of elements 311, 312, 313. EMBODIMENT OF FIG. 5 The arrangement is constructed, entirely, in cylindrical form. The UV filter 510 and the first-mirror-filter combination 511 are formed as cylinder sectors. Corresponding to FIG. 2, eight sections are provided, formed as eight sectors, which, alternatingly, are formed by a UV filter 510 and a first mirror-filter combination 511. The second mirror-filter combination forming the sandwich 14 can be identical to that shown in FIG. 2. Of course, the IR filter 513, as well as the UV mirror 512, must be curved. FIG. 6 illustrates a cylindrical arrangement which has only two sections, forming a half-cylinder 8. A semi-cylindrical--in projection a semi-circular--UV filter 610 is located at the left half of the structure, the right half of the structure being formed by the first mirror-filter combination 611 which, again, in cross-section is semi-circular. The mirror-filter combination is formed by the semi-cylindrical UV filter 612 and the semi-cylindrical IR filter 613. The second mirror-filter sandwich assembly 614 likewise is semi-circular and arranged to place the UV filter 610 entirely in the shadow from the radiation source. In this construction, it is sufficient if the second mirror-filter combination sandwich 614 has the outer UV mirrors 616 applied only along the edge portions thereof; the IR filter 17 and the inner UV mirror 615 extend in the form of a semi-circle or, rather, semi-cylindrical structure around the radiation source 9. The first mirror-filter combination, in which the inner UV mirror 12 has its reflective surface directed towards the radiation source, is congruent with the respective mirror and, preferably, formed as a single, engaged sandwich, as shown by the 311, 411 or 511, FIGS. 3,4,5, for example. UV radiation which impinges on the mirror surface of the UV mirror is reflected back into the interior of the apparatus; visible and IR radiation, however, is permitted to pass through the UV mirror, suitably filtered by the IR filter, and then leaves the apparatus to impinge on the sample S. Thus, UV radiation is separated from the IR filter and cannot cause deterioration thereof. The second mirror-filter combination has two UV mirrors with externally directed mirror surfaces, between which the IR filter is located. Again, in accordance with a preferred feature of the invention, the mirrors and the filter form one composite sandwich, although the respective elements may be spaced from each other. The UV portion of radiation is reflected away from the IR filter, so that the IR portion and visible radiation from the light source can be passed without essential attenuation, while being filtered with respect to IR radiation in accordance with the IR filter characteristics. Separating the UV portion of the radiation from the IR filter of the second mirror-filter combination 14 protects the filter 17 of the combination. Likewise, the other UV mirrors permit reflection of the UV radiation towards the interior of the system, for emission through the UV filter 10 and impingement on the sample S. If desired, the sample holder for the sample S and the radiation apparatus can be relatively movable, e.g., rotatable. The basic principle of the arrangement contemplates to separate out the UV component by a UV mirror from the composite radiation received from the radiation source 9 before the radiation impinges on any IR filter or passes through the external or outer UV filter 10. Thus, the UV portion cannot affect the IR filters and cause aging thereof and change of its filtering characteristics. The IR radiation passing through the UV mirror of the first mirror-filter combination 11 is influenced by the IR filter portion 13 thereof. This filter portion may be a KG filter. At least one window, formed between the first and second filter-mirror combination, permits emission only of UV radiation, which had been reflected by a UV mirror at least once. Separating the radiation within the arrangement into the UV component and the IR and visible light component permits filtering only after the respective spectral components have been separated. This permits independent filtering by filters having respective filter flanks or filter characteristics independently of each other. This arrangement, further, permits to obtain any desired precisely defined overall radiation curve, determined by the respective filter characteristics, and hence a precisely defined filtering curve for the overall apparatus while using commercially available filters. Aging effects are essentially avoided, and specifically aging effects of the UV-characteristics of the KG filters, that is, the IR filters, which are highly susceptible to changes in their characteristics when irradiated by UV radiation. The spectral distribution of radiation emitted by the apparatus remains constant, even after long use thereof. The apparatus, additionally, eliminates the use of IR mirrors. IR mirrors are available commercially only in limited spectral reflecting characteristics. The arrangement is highly efficient, since absorption losses are low. Depending on the irradiation cycles, the illumination apparatus is surrounded by an even number of sections, alternating a UV filter 10 and a first mirror-filter combination 11, so that samples S which are passing around the illumination device are alternately irradiated with UV radiation and, then, with visible and IR radiation, with the IR radiation being controlled in accordance with the respective IR filters being used. In accordance with a preferred feature of the invention, the second mirror-filter combination 14 is so arranged that the respective UV filter is entirely in the shadow of the second mirror-filter combination 14 with respect to radiation emitted from any point of the light source. As an alternative, the second mirror-filter combination 414 (FIG. 4) can be so arranged that it is divided into two portions 25,26 which are placed at an angle with respect to each other, having an apex 24 located in a median range of the UV filter 410. The lengths of the second mirror-filter combination 414 must have a length sufficiently great that the respective outer UV filter 410 is entirely in the shadow with respect to direct radiation from the source 9. The arrangement in accordance with FIG. 2 provides for only one window for the passage of UV radiation; in the arrangement of FIG. 4, radiation may pass through two windows as shown in FIG. 9 by beams 421',421". The specific arrangement and shape of the respective mirror-filter combination is variable. Thus, the outer UV filter 10 and the outer UV mirror-filter combination 11 may be cylindrical, see FIGS. 5,6, or may surround the radiation source in form of a square, an equilateral triangle, an octagon, or the like. Each flat side--if a polygon is used--may be formed of a plurality of first mirror-filter combinations 11, and UV-filters 10. Preferably, however, any one side of any polygon should have only one UV filter 10 and the first mirror-filter combination 11. The preferred arrangement is that of FIG. 2, in which a single second mirror-filter combination 14 is used. The angle between the outer UV filter 10 and the second mirror-filter combination, shown at angle 18, can be between 45.degree. and 80.degree., preferably between 60.degree. and 70.degree.; smaller angles can be used, however. The arrangement is geometrically particularly desirable, and UV radiation is subjected only to few reflections on the respective UV mirrors before reaching one of the UV filters 10. Consequently, reflection losses, which are unavoidable, are very low, resulting in a high-efficiency apparatus. Various changes and modifications may be made and features described in connection with any one of the embodiments may be used with any of the others, within the scope of the inventive concept.