BE1019980A3 - EVALUATION OF COLORED GLAZING. - Google Patents

Abstract

The invention relates to a method for evaluating the incidence of colored glazing on objects observed in transmission through these glazings and comprising the formation of a base of transmission spectra of colored glasses, the formation of the image under digitized form, its transformation by the application of the spectrum in transmission of the glass and its display on the screen.

Description

The invention relates to the evaluation of the incidence of colored glazing on the objects observed in transmission through these glazings. In particular the invention relates to glazing of the "automotive" domain. In the description which follows it is this mode of application which is systematically referred to, but the invention is equally useful for other types of applications for which the presence of a glazing introduces a particular coloration in transmission . This is particularly the case in building applications whether external glazing, partitions or any item of furniture.

The evaluation in question relates to the impact on the perception of the color of objects through these glazings, and thus the change in perceived color in transmission.

The choice of glass compositions to achieve a satisfactory coloring to a customer is a complex operation. The most frequently the question is solved by Γ use and presentation of pre-existing sample sets. The image in transmission is appreciated directly by the observation of this image through the sample.

The diversification of the requests requires an ever increasing number of samples, which makes this method of proceeding inconvenient and this especially as the composition of the glass is added at least the influence of the thickness of that -this. From the limited samples presented to him, the client can not immediately visualize the desired effect.

The glassmakers are able to make practically all the shades that meet the customer's wishes. The difficulty is to materialize these wishes in a technical language that can translate these wishes objectively. The invention aims on the one hand to allow the choice of glazing by the user and on the other hand materialize this choice by parameters exploitable by the glass manufacturer.

In addition, manufacturers' requests for glazing concern multiple questions. The qualities sought are simultaneously mechanical, energetic but also aesthetic. The question posed arises from this last category. The colored "filter" that constitutes the glazing must not modify the objects and people in a way that gives them an unpleasant appearance. People in the vehicle should not present to outside observers an unflattering complexion. It is also true in general of the elements of the cabin, trim, dashboard ...

The inventors have therefore sought a means for viewing the transmission image corresponding to a given colored glazing, and this regardless of the glazing and regardless of the basic image that is chosen.

The inventors propose to achieve this result by using the method forming the subject of claim 1.

In principle, the invention provides a means of visualizing the appearance of images through the filter constituting the chosen colored glazing, without having a corresponding material sample. The benefit of this operation is all the more sensitive as it can be repeated as often as desired without leading to long delays or excessive handling. The result of this selection is instantly available.

For the implementation of the invention it is first necessary to build a database comprising at least the spectral characteristics in transmission of multiple glasses previously made, regardless of the origin of these glasses. The more the base is extended the higher the probability of finding the satisfactory glass. For the treatment the basis of the spectra is digitized.

The transmission spectra are introduced simultaneously with the thicknesses of the corresponding glasses. The data are first those obtained experimentally.

In order not to unnecessarily load the base in question with elements that would make it too bulky and therefore unmanageable, it is preferable to limit the ranges of thicknesses to those normally used in the envisaged applications. It is necessary to take into consideration not only the glazings consisting of a single sheet of glass, but also the sheets used in the composition of the laminated sets and the sets themselves.

"Automotive" glazings usually have thicknesses for monolithic sheets that do not exceed 5mm and the current trend is to reduce the thickness for lighter vehicles. The monolithic sheets, for reasons of mechanical strength, have a thickness which is not usually less than 2 mm. For laminated glazing, the constituent sheets may be substantially less thick. For the thinnest they can be of the order of 1mm. Note that in laminates comprising sheets as thin, the second sheet is usually thicker to confer sufficient strength to the set.

Outside the automotive field, the thicknesses are much more variable, especially when the qualities of resistance are not very drastically restricted by the concern for lightening. Glazing in the building sector can go to thicknesses of several centimeters. Sheets of 6, 8, 10, 12, 14, 16 and even 18mm thickness are conventional in some applications. Sheets of this type are also associated in thick laminates in certain applications such as glass slabs or burglar or armor-resistant glazing. In any case, the process according to the invention is not limited to certain ranges of thicknesses. The constitution of the database will simply be adapted to take into account these particular applications.

The base of the transmission spectral data may advantageously contain data relating to various combinations, for example two sheets of different thicknesses, but also sheets whose composition, and consequently the color, is also different.

The spectral data of the laminated glazings are introduced into the base. These data also include the characteristics of the interlayer sheets that join the glass sheets. These interlayer sheets are most often colorless and do not substantially alter the spectra of the glass sheets they assemble. But they can also be colored and in this case must also be taken into account in determining the appearance conferred by the glazing.

The glass sheets involved in the constitution of automotive windows or the like are also often coated with thin layers that are likely to influence more or less the color in transmission. Layers of this type are in particular applied layers for conferring or modifying optical or energetic properties. These include the introduction of filtering effects of infrared or ultraviolet rays, but the incidence of which also exceeds the ranges of wavelength of the visible. Layers are also arranged for their selective absorption, or their reflection.

In any case, when layers are applied which introduce a change in the light transmission, it is useful to proceed to the introduction in the base of the specific characteristics of these layers, in the same way as for the interleaves. , or of course the glass sheets themselves.

The number of combinations of different factors influencing the color in transmission can quickly exceed the processing power of computing tools of reasonable capacity for the applications considered. In order not to multiply the experimental data, either of thickness for each glass, or of a combination of different glasses, it is possible, from a small number of data, to proceed very satisfactorily by computer processing to the development of the spectral data. lacking in the base from the "elemental" spectral properties of the glasses concerned. The tool makes it possible to reconstruct these properties and avoids unnecessarily loading the base.

The screen representation of the transmission effect of the glazing necessarily involves the spectra of the RGB components of the screen. For each component, the latter offers a range of given intensities, for example traditionally from 0 to 255.

An image in the digitized system is defined pixel by pixel. Each pixel corresponds to a combination of the specific intensities of each of these three spectra. This combination gives a spectrum of the pixel of the image. The method according to the invention subjects each pixel spectrum of the image to the transformation corresponding to the application of the filter, in other words to the transmission spectrum of the glazing considered. This results for each pixel a transmitted spectrum.

For the display on the screen of the image modified by the presence of the glazing, the transmission spectra of each of the pixels are again decomposed according to the three spectra of the basic colors.

Since the transformation operation is applied to each pixel of the image, the power of the computer tool used controls the number of pixels that can be processed in an acceptable time. But in principle at least, the definition of the processed image is not limited.

The quality and fidelity of the on-screen presentation of the image and its perception through the glazing requires as it is known to use devices properly "calibrated".

Calibration passes in particular by the choice of the reference. This reference is usually a function of the applications considered. For "automotive" glazings, the reference advantageously chosen is that of the 6500K white point (illuminant D65). In addition, the gamma setting of the screen is preferably equal to 1 so that the brightness of the screen develops linearly over all the shades reproduced (for example from 0 to 255).

The conditions listed being satisfied, the image of the object in transmission through an initially chosen glazing is faithfully rendered. It is possible simultaneously on the screen to bring out the effect of the glazing juxtaposing for example by half, the initial image and the one seen through the glazing.

The result can be immediately modified for example according to various thicknesses of glass.

The operation can also be repeated quickly for new choices that are possibly oriented by the display of glasses whose spectra are closest to that initially chosen, or according to a given evolution for example less red, more than green...

The database established for transmission spectra of glasses may contain other elements useful for users. Among the most usual, it is useful for example to know the opto-energetic characteristics, including energy transmission TE, UV transmission, reflection characteristics: intensity, color ... All these data can be displayed simultaneously or independently of the image in transmission.

The invention is described in detail hereinafter with reference to the diagrams illustrating pictorially the processing performed according to the invention in which: FIG. 1 schematizes the preparation of the database relating to the glass sheet; Figures 2a and 2b illustrate the mode of processing an image by the method according to the invention.

The preparation of the database is performed from parameters of glasses V previously made. The minimum data recorded for each glass is constituted by the transmission spectrum for a given thickness. The transmission spectrum is that corresponding to a chosen incident light I, such as that of the illuminant D65, ordinarily used to qualify the optical and energetic properties of glazing in the automotive field.

The spectrum SpV is that determined experimentally for each glass and for a given glass thickness. It represents in normal incident light to the glass sheet, the percentage of light intensity transmitted as a function of the wavelength λ. In order to determine the effect of the presence of the glazing on the appearance of the objects located behind this glazing, the spectrum may be limited to the wavelengths of the visible, ie the range between 380 and 780 nm.

To add to the information relating to the use of these glasses it is also possible to introduce the transmission characteristics out of the visible field, either in the infrared range, in particular for the thermal comfort aspects, or in the ultra-violet ones which are considered especially for their aging effect of certain materials.

The spectral data SpV are necessarily associated with the thickness of the sheet. If necessary, for the same glass, spectra are recorded for different thicknesses.

If possible, it is preferable to establish the base for a uniform thickness for all glasses, in order to facilitate the treatment. Nevertheless it is also possible to generate the spectra in question from those of different thicknesses. The choice to standardize as much as possible the thickness of the glasses entering the base is to reduce as much as possible the subsequent treatments for carrying out the process.

As schematized further in FIG. 1 by the icon of the computer Ç, the spectral data in transmission, and possibly those relating to other characteristics of the glasses, are introduced into a digitized base for subsequent processing.

Apart from the glasses, the base may also contain information concerning the interlayer sheets to be able to establish the incidence of the presence of laminated glazing comprising these spacers, at least the most usual. Among these include poly-vinyl butyral (PVB) sheets. But it can also traditionally be ethylene vinyl acetate (EVA), polyvinyl chloride (PVC) or polyurethane (PU).

The incidence of these intercalated sheets on the transmission spectrum is ordinarily limited for the visible range, when it is colorless interlayer. This incidence usually results in a very slight absorption over the entire visible spectrum, and therefore does not significantly change the appearance of the colors in transmission.

There are also colored dividers whose role is essentially to modify the spectrum in transmission. It is therefore necessary to have corresponding transmission spectra in the base.

It should also be noted that these dividers, even colorless, can have a much greater impact in areas out of the visible. This is particularly the case of PVB which absorbs strongly in the ultraviolet field. The corresponding characteristics are therefore advantageously introduced into the base, if these elements are useful outside the main purpose pursued by the invention.

As for glasses, the thickness of the spacers is also introduced with the spectral data in transmission. However, these data are more restricted in that the thicknesses actually used are very standardized and in very small numbers. For automotive laminated glazing in which a PVB interlayer is used, it is always 0.38 or 0.76mm thick.

FIGS. 2a and 2b schematize the processing steps leading to the representation of the image on the screen as it appears in transmission through a glazing V.

To visualize the influence of the presence of the glazing on a given object, the image of the object is first seized alone, in other words without the presence of the glazing in question.

The representation on the screen passes through the characteristics of the apparatus which for each pixel of the screen combines the basic colorimetric components RGB, to each of which correspond a spectrum, and a range of intensities for each of these spectra. This range is for example from 0 to 255.

The image of a pixel is thus constituted by the spectrum SpPi resulting from the combination of the three basic spectra SpRi, SpGi, SpBi.

The treatment according to the invention applies the transmission spectrum of the SpV glass to the SpPi spectrum of each pixel. This application consists of transmission intensity weighting for all wavelengths. The result of this treatment is a new spectrum SpPt.

The influence of the glass sheet on the transmission is not determined by the number of pixels processed. For a good rendering of the image it is nevertheless preferable to have a sufficiently high definition, in other words a relatively large number of pixels per unit of image area. The data processing time is directly related to the volume processed. It is therefore not desirable for the definition to exceed certain thresholds that would not add to the desired assessment.

Figure 2b illustrates (without the corresponding colors) and on a part of the initial image (on the right), the influence of the presence of the glazing (on the left).

To satisfactorily visualize the initial image as the image in transmission it is necessary to use screens capable of reproducing the colors without practically deformation. For this purpose the screens are necessarily calibrated as indicated above.

Insofar as the effect of the glazing does not meet the expectation of the observer, the latter can look in the base for a glass which is distinguished from the first by a variation that can be chosen. For example, by reinforcing a blue or green shade. The basis on the introduction by the user of the desired modification determines the characteristics of the closest appropriate glass. The operation is then repeated and a new image is produced.

To illustrate the processing mode we consider an initial image pixel having intensities for RGB components respectively for example R = 25 (over the range of 0 to 255) G = 30 (over the range of 0 to 255) B = 100 (on the range of 0 to 255)

The spectrum of the pixel of the image SpPi, is therefore that which combines the basic spectra SpR, SpG, SpB, weighted coefficients, or figuratively

SpPi = 25 / 255xSpR + 30 / 255xSpG + 100 / 255xSpB This SpPi image spectrum is transformed by the filter constituted by the glass, as a function of the transmission rates for each wavelength of the spectrum. This results in a spectrum in transmission noted SpPt for each pixel of the initial image.

For example, the transmission spectrum is broken down into the three RGB components, with coefficients after transmission which could be for example:

Rt = 15/255 Gt = 20/255 Bt = 47/255

These values are given arbitrarily for the sole purpose of materializing the type of treatment used.

The values thus determined are those which are reproduced on the screen.

Claims (8)

1. A method for evaluating the incidence of colored glazing on objects observed in transmission through these glazings comprising: - the preliminary constitution of a SpV transmission spectral base of a previously produced set of glasses and for given thicknesses; the base is constituted in digitized form for screen reproduction, each pixel of the screen restoring the luminous intensity by the combination of the three elementary components R, G, B, whose respective spectrum are SpR, SpG, SpB; the digital formation of an image, each pixel of the initial image being determined for the intensity of each of its components Ri, Gi, Bi to which correspond the spectra SpRi, SpGi, SpBi; the constitution of a specific spectrum SpPi of each pixel resulting from the association of the spectra SpRi, SpGi, SpBi; the application of the transmission spectrum of the SpV glass to the spectrum of each pixel of the SpPi image, giving a new SpPt transmission spectrum for each pixel; the decomposition of the SpPt transmission spectrum into three, in the form of a linear combination of the spectra SpR, SpG, SpB whose coefficients constitute the new components Rt, Gt, Bt; - display of the image on calibrated screen. 2. Method according to the preceding claim wherein the base of transmission spectra is established for automobile application glasses whose thickness is between 1.1 and 4.85 mm. 3. The method of claim 1 wherein the base of transmission spectra is established for building application glasses for glass sheets whose thicknesses are 6, 8, 10, 12, 14, 16 or 18mm. 4. Method according to one of the preceding claims wherein the evaluation is conducted for a glazing comprising a plurality of glass sheets and neutral or colored interlayer sheets, the SpV transmission spectrum of the glass being the resultant of the set of respective spectra. of each of the constituent elements of the glazing. 5. Method according to one of the preceding claims wherein the base of the transmission spectra also comprises spectral data relating to thin layers applied to the glass sheets of the glazing. 6. Method according to one of the preceding claims wherein the display screen is calibrated for a white point at 6500 ° K. 7. The method of claim 6 wherein the gamma of the screen is close to 1. 8. Application of the method according to one of claims 1, 2, 4 to 7, for windows "automobile", the image reproduced being that of the interior of the vehicle.