GB2123139A

GB2123139A - A device for the fast measurement of the gloss of a surface

Info

Publication number: GB2123139A
Application number: GB08310237A
Authority: GB
Inventors: Gunter Rockstroh; Klaus Schnieder; Boris Lux
Original assignee: Pentacon Dresden VEB
Current assignee: Pentacon GmbH Foto und Feinwerktechnik
Priority date: 1982-06-29
Filing date: 1983-04-15
Publication date: 1984-01-25
Also published as: GB8310237D0; DD208670A1; DE3312948A1; GB2123139B

Abstract

The distribution of light from a pulsed source 2 after it has interacted with a surace 5 being tested is transformed into a distribution of electrical signals with the aid of a line 7 of detectors and an analogue store 8. Advantageously, the detector line is so arranged that the point of intersection of the surface normal of the individual detectors is located in the sample centre. In this connection, it is favourable for the performance of the measurements that the spectral sensitivity of the individual detectors of the detector line is adapted to that of the eye or that the source 2 is a green light-emitting diode, so as to prevent any possible spectral falsification of the gloss values so determined. <IMAGE>

Description

SPECIFICATION A device for the fast measurement of the gloss of any optional surface The invention relates to a photo-electricaily working device forthe fast routine measurementofthe gloss of any surface.

Forthe gloss definition, there are known several gloss numbers, such as the mirror gloss number, the reflectance gloss number, the logarithmic gloss number, etc.

With all these gloss number definitions, and the apparatus conceptions derived therefrom, such as reflectometers, multi-angle reflectometers and twodiaphragm reflectometers, itis impossible to produce an exact correlation ofthe measured values with visual measurement rows.

The definition ofthe gloss number Gt established by Fleischer: -t Gt = I - e 10 with:t=20 d do it L(o:)max oc: evaluation angle L: luminance also forms part of the priorart.

This gloss number correlates very well with the visual gloss scale. For the practical application ofthis gloss numberGThernisnecessarythedetection ofthe luminance L. For measuring the required luminance distribution there are known goniophotometric laboratory units which entail however problems with respect to their complexity, susceptibility to trouble, considerable size and the long measurement and evaluation times. Forthe latter reason, it is impossible to control the gloss influencing production parameters in the manufacturing process according to the exact gloss number as per Fleischersincetimes in the ms range are appropriate here, causing the resolution of position of moved samples, for example of running paper webs, to be correspondingly high.

Glossmeters, with the aid of which the luminance distribution is detected continuously but only in a very small angular range, such as are described in DE OS 2905727 and DE OS 28 51 455, are only suitable for special cases of application. A multivalent use thereof for gloss measurement is not possible.

The invention aims at performing gloss measurements without the mentioned disadvantages.

It is the object of the invention to develop a trouble4reearrangementforthefast routine measurement and control ofthe gloss of any surface, more especially according to the definition of the exact gloss number as per Fleischer.

According to the invention, the problem is solved in that the luminance spectrum of a sample irradiated with light pulses is transformed into an electrical signal spectrum with the aid of a detector line.

Advantageously, the detector line is so arranged that the point of intersection ofthe surface normal of the individual detectors is located in the sample centre. In this connection, it is favourable forthe performance of the measurements that the spectral sensitivity of the individual detectors ofthe detector line has been adapted to that of the eye or that, forthe irradiation of the sample, there is used a light-emitting diode which emits a green light, so as to prevent any possible spectral falsification of the gloss values. According to another inventive conception, following the simultaneous detection of the luminance spectrum, the measured values are stored in an analogue form and are processed further serially.For controlling the gloss influencing production parameters of the sample, it is furthermore proposed according to the invention that there should be provided successively in the control loop a digital-to-analogue converter, power output stages and final control elements.

The invention will now be explained in more detail with reference to an exemplified embodiment and to the accompanying drawing.

The radiation emitted by a light-emitting diode 2, which is triggered by a pulse generator 1, passes via a collimator lens 3 as a parallel bundle 4 onto the surface ofthe sample 5. The ray components 6 reflected from the sample surface are evaluated by a high-resolution detector line 7. The detectors ofthis line are so arrangedthatthe point of intersection of the surface normal is located in the sample centre.

Due to the short response times of the photodetectors, the illumination of the sample 5 can be effected with lightflashes. As advantages there come about a short measurement time and minimal thermal stress of the samples. As a result of the simultaneous detection of the luminance spectrum, short-term fluctuations ofthe light intensity ofthe ray do not falsify the measurement resu It; the relative accuracy ofthe gloss measurement is rendered very high. The photo-detectors transform the optical signals into electrical signals which are collected in an analogue quantity store 8. The selector switch 9 allows an interrogation of the individual analogue quantities and feeds these serially to the analogue-to-digital converter 10, whose output signals are compatible with the micro-computer 11.In the micro-computer 11 itself there is effected, taking into consideration the measured value correction according to the apparatus function, the computation ofthe gloss number, the comparison with nominal values as well as the control ofthe gloss influencing production parameters via th'e digital-to-analogue converter 12, the power output stages 13 and 14 and the final control elements 15. The control of the measurement sequence and the visual display of the measurement result are effected by the control unit with the terminal 16.

The geometry of the measuring device (illuminated surface, distance detector line 7/sample 5 and detector surface) is so fixed that, in accordance with the required measurement accuracy, the necessary measuring aperture is not exceeded.

There is no departure from the scope of the invention ifthe reflected ray components 6 are focussed into the detector plane by optically active constructional elements.

The advantage ofthe invention isto be seen in the factthat in addition to the known gloss numbers it is possible to measure the exact gloss number accord ingto Fleischerquickly and routinelyforwidely varying surfaces.

Claims

1. Adeviceforthefast measurementofthe gloss of any surface, characterised in that the luminance spectrum of a sample (5) irradiated with light pulses is transformed into an electrical signal spectrum with the aid of a detector line (7).

2. A device for the fast measurement of gloss as claimed in Claim 1, characterised in that the detector line (7) is so arranged that the point of intersection of the surface normal ofthe individual detectors is located in the sample centre.

3. A device for the fast measurement of gloss as claimed in Claim 2, characterised in that the spectral sensitivity of the individual detectors ofthe detector line (7) has been adapted to that of the eye or in that there is used for the irradiation of the sample (5) a light-emitting diode (2) which emits a green light.

4. A device forthe fast measurement of gloss as claimed in Claim 3, characterised in thatfollowing the simultaneous detection ofthe luminance spectrum, the measured values are stored in an analogue form and are processed further serially.

5. Adeviceforthefastmeasurementand control of gloss as claimed in Claim 1, characterised in thatfor controlling the gloss influencing production parameters ofthe sample (5) there are provided in the control loop successively a digital-to-analogue converter (12), power output stages (13,14) and final control elements (15).

6. A device for the fast measurement ofthe gloss of any surface substantially as described herein and with reference to the accompanying drawings.