DE2335842C3 - Device for comparing the spectral remission or transmission of a test object and a standard - Google Patents

Description

The invention relates to a device for comparing the spectral remission or transmission a test item and a standard, in particular for checking the authenticity of banknotes and others Stamps, with a polychromatic light source, with a first, from the light source to a certain point of the test object and a second, from the light source to a corresponding one Place of the standard leading light guide, with a third and a fourth light guide for receiving of the light remitted or transmitted by the illuminated point of the test object or the standard, with a device for alternately applying the light to the first and second light guides Light source or to alternately block the third and fourth light guide, with one of the third and fourth light guide acted upon optical arrangement for the separation of a certain number narrower spectral ranges from the spectrum of the reflected or transmitted light, and with a Measuring and evaluation device for photoelectric detection and comparison of the test item and standard intensities reflected or transmitted in the respective narrow spectral ranges.

As is well known, the human eye is unable to determine from which spectral colors a Color stimulus is composed. It is therefore possible that colors with different spectral compositions produce exactly the same color sensation. The reproduction of a specific color is relatively easy as long as an identical physical impression is required. Much harder is to reproduce a color with exactly the same spectral distribution. When comparing remission two colored areas or when comparing the transmission of a test object and a standard, z. B. in the authentication of banknotes provides

-ne complete spectral analysis a very, oniit em _represent

⁹ ^ c t already known an apparatus (US-PS 00 78SI which automatically a spectral analysis • "document makes and a Ja.Nein-decision ■ * ^'i8S m ρ Here, the same applies Sieiie the decision ^^ original with a first light Ii lit narrow spectral range at the same time convenient mil k _i light sensor that from the test

leucntet, m

ling and α ^ ver _beidcn measured values _measured with each other en ^un _{hließend W} j _rc j, the same measurement with matched, ai - _n ^ _{and a} light source in _driuen ^Hl -. ^Cl wn narrow spectral repeated. ^two lt is judged to be real if at all

In the spectral range at the same time with _two light sensors that are

withstands bungle rivers and whose working _{speed is high}

This object is achieved according to the invention in that the optical arrangement for separating 5 of the narrow spectral ranges contains a mixing and distribution head designed as an integrating sphere and acted upon by the third and fourth light guides, as well as a filter device which is one of the _two light sensors that counts from the test The original reflected light corresponding to the spectral range to be separated has a sufficient number of _{transmission ranges} , the two measured values of which mutate with one another, each with a further light guide with the

Mixing and distributing head is connected, and that the measuring and evaluating device is one of the number

^Hl - ^Cl repeated in narrow spectral ranges. aussonderten the spectral regions corresponding to ^two N ^e l.Mment is judged as genuine, if i has all ₅ number of light sensors, from each of which ^the VernTeichsmessungen the difference between a determined after each pass band of the F.lteremnch- ^ ^Tel m Prüflina test measured value and the i

η inal determined Standardmeßwert a does not exceed before ^the bright value. ^{| e} | s is also a colorimeter for measuring the color * o. uoftpp of an object and for comparison own "" uncfc reference object

^{known with} nLnes named type (DT-OS ff. «9? at d? m the ^{remitted from the subject to be examined 21} d 'or from the reference object

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one behind jee
treatment is arranged.

Developments of the invention are the subject

of the subclaims.

Description of the drawing

The following is an embodiment of the invention explained in more detail on the basis of the only drawing figure. Here is from the Beisp.cl of the application of the inventive concept in a banknote validator

Ä i ^^ XÄll!

Ä i ^^ XÄ (DT ₇ AS 1131570), which shows the color point of a sample and a standard on a Braunr.chen tube. Here photocells are arranged inside a UIbrichtkugel alternately over the sample and practice

zugswe.se emc ^ "'br.cjtkg 1 _inrichlu g.

13 to} ^C _ps ^C1 "7 _v J ^ _v ^ au a graduated filter. This ^ b ^ νorz ^^ eca ^ ^^ ^

LiUs ₁ ir ^ ^ie " ^c ^ [^ _{d of these} opposite-

Finally, a Kolor.meter is known (DT-OS I rul lin _e a "graduated filter can selbstver-21 Ol 818), in which a scanning head scans the emer of ^ ate ^ -Jn Represents eme _Einze lfiltern beProbe rem.ttierte light. This will be found over 55 _{years of age} . a fiber optic to a single Liditde ek to ^ stand k m_ _Vcrtii , _head J ₂ leads another leads. Single front of the entrances Lichtfuhrungtn \ jm N Isui _Re f _e rence light sensor 14 before correction filters are arranged. , The pass band are selected in total gene, such that the overall Mn a rotatable "L ü t eittr JJ J« _{14 may cin F} = _Luer 15 is ring may ^elcren a particular group of Lichtfuhrun- c ej ^{'1 <} 60 ordr ^ se η, de ^ corresponding _area, wished Empfindlichkeitsverte, ungskurve gbt _c ^z ™ ^ S, _{it is} to a maximum value ₉

the optical adjustment and

iparaiors ίο vcn. ^ .. "· ..., a control input of a vorut " ^ r "" is. The

The maximum value memory 17 is connected to the second input of the comparators 18 via an integrator 20. A pulse generator 21 is connected to one counting input of each of the up / down counters 19. Each up-down counter 19 is assigned a logic circuit 22 which is connected to a common Decision logic 23 are connected.

A control circuit 24, shown only schematically in the drawing, controls the program sequence the device; it switches the light source I, controls the diaphragm 2, causes it at the appropriate time the deletion of the maximum value memories 16, 17 and the resetting of the up / down counters 19 and controls their counting direction.

The device described works as follows: At the beginning of the program sequence, the diaphragm 2 is in such a position that the light source 1 throws polychromatic light onto the test object 5 via the light guide 3. Part of the light remitted by the test object is detected by the light guide 10, divided into the η light guides 13 in the mixing and distribution head 12 and thrown from these via the filter device 8 onto the η light sensors 9. Each of the light sensors 9 is hit by only a narrow spectral range of the light remitted by the test object. The maximum value U ₁ to U _n of the electrical signals generated by the light sensors 9 is stored in the maximum value memory 16.

The reference light sensor 14 detects the entire spectrum analyzed by the light sensors 9 and generates a reference measured value which corresponds to the basic brightness of the test object 5. The maximum value U _{r of} this reference measured value is stored in the maximum value memory 17 and integrated by the integrator 20. A signal U arises at the output of the integrator, according to the relationship U, - = U _r · t / τ, where / means the time and τ the time constant of the integrator.

Simultaneously with the start of integration of the integrator 20, the forward-down counters 19 are enabled and the pulses emitted by the pulse generator 21 are paid into the counters 19. The comparators 18 compare the signal U ₁ with the measured values U ₁ to U _n . When the signal U ₁ reaches the value U 1, the comparator 18 of the corresponding measuring channel responds and the up / down counter 19 assigned to it is stopped. The following then applies:

Ur

where /, means the period of time during which the pulses were counted into the up / down counter under consideration. Similar relationships apply to the other measuring channels. Thus, pulses are added to each of the pulse counters 19 during a time that is directly proportional to the associated measured value and inversely proportional to the reference measured value. If the pulse frequency of the pulse generator 21 is constant, the quotient of the measured values U ₁ to U _n and the feedback value U i is formed.

The maximum value memories 16, 17 are now deleted, and the aperture 2 is set in such a way that it is subsequently The standard is illuminated via the light guide 4. The MeRvoriiani previously described:

is carried out in the same way on Standard 6, but with the difference that now the counting direction the up-down counter 19 is reversed, d. i.e., the pulses from the pulse generator 20 are counted out of the counters 19. It is easy to see that at the end of the measurement all Counter 19 are back to zero when the test specimen S exactly matches the standard 6 in all color nuances is equivalent to. Counter with positive or negative

ίο The meter reading indicates a deviation in the remission of the relevant spectral range. _{The relationship N, = (r, -Z 1} *) / # applies to the count / V _{1 of} the counter 19 of the previously considered first measuring channel, where fg is the pulse frequency of the pulse generator 21 and T ₁ * is the duration during which the pulses from the considered forward Down counters have been counted out. The logic circuits 22 determine whether the counter country of the forward / backward counter 19 is within predetermined limits or not. The decision logic 23 finally emits a "good" signal if z. B. at least (/ 1 - 2) of all meter readings are within these limits.

_a . advantages

The device described is relatively simple and does not require any time-consuming adjustment hardly susceptible to interference and nevertheless allows a very precise comparison of the spectral remission a test item and a standard. Transmission measurements can of course also be carried out will; for this it is only necessary to place the light guides 10, 11 on the one opposite the light source 1 Side of the test object 5 and the standard 6 to be arranged.

The stability of the light source 1 and the light sensors 9 and 14 is subject to only minor requirements. The sensitivity of the light sensor only has to remain constant during the two successive measurements. If, as described, the quotient of the measured values U ₁ to U _n and the reference _{measured value U 7} . is formed, it is not even necessary for the intensity of the light emitted by the light source 1 to be the same in the two measurements if only the relative spectral energy distribution is maintained. This advantage is essential if a flash lamp is used as the light source, the flash intensity of which is known to be difficult to keep constant.

By forming the quotient from the measured values and the reference measured value, it is also achieved that a neutral, d. H. Soiling was constant over the entire analyzed length range of the test item does not affect the measurement result.

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variants

Instead of a single light source 1 and a diaphragm 2, two separate ones can of course be used Light sources are used. The diaphragm 2 can have the same effect in place in front of the test object and the standard can only be arranged after these.

The light guide 13 ', the filter 15, the Rcferenzlichtfiihlcr 14 and the maximum value memory 17 can

There is no need for fi.5 if the input of the integrator is connected to one of the maximum value memories 16. In this case one of the measured values U ₁ l'i '{'; iK reference value is used. The Vonviirtv-Riick-

The upward counter of the channel concerned must then be set to zero after each completed comparison measurement stand; If this is not the case, a malfunction of the arrangement is indicated.

In the explanation of the mode of operation of the illustrated embodiment, it was assumed that that the pulse frequency of the pulse generator 21 is constant. The up-down counters 19 register here the measured values are linear. But since the error limit specified by the logic circuits 22 is constant, larger relative deviations are permitted for small measured values than for

large readings. To avoid this, the pulse generator 21 can be controlled such that the pulse frequency decreases continuously or in steps during pulse counting. This can be achieved. that the same relative deviation is permitted for small measured values despite a constant error limit becomes as with large measured values.

The logic circuits 22 can also be designed so that each count with several ίο different error limits are compared. This means that there can be extreme deviations from the decision-making logic 23 are rated accordingly strongly.

1 sheet of drawings

Claims (8)

Patent claims: 1. Device for comparing the spectral remission or transmission of a test object and of a standard, in particular for checking the authenticity of banknotes and other stamps, with a polychromatic light source, with a first, from the light source to a specific one Place the test item and a second, from the light source to a corresponding one Place the standard leading light guide, with a third and a fourth light guide to Recording of the or remitted from the illuminated point of the test item or the standard transmitted light, with a device for alternately acting on the first and second light guide with the light of the light source or to alternately block the third and fourth light guide, with an optical arrangement acted upon by the third and fourth light guide to remove a certain number of narrow spectral ranges from the spectrum of the remitted or transmitted light, and with a measuring and evaluation device for photoelectric Acquisition and comparison of the remitted or transmitted from the test item and standard in the respective narrow spectral ranges Intensities, characterized in that the optical arrangement for the separation of the narrow spectral ranges one designed as an integrating sphere and the third (10) and fourth (11) light guides acted upon by the mixing and distribution head (12) and a filter device (8) contains the number corresponding to the number of spectral ranges to be eliminated of transmission areas, each with a further light guide (13) with the mixing and distribution head (12) is connected, and that the measuring and evaluation device a number of light sensors (9) corresponding to the number of spectral ranges that have been separated out has, one of which is arranged behind each passage area of the filter device (8) is. 2. Apparatus according to claim 1, characterized in that the filter device (8) is a Graduated filter is. 3. Device according to claims 1 or 2, characterized in that the measuring and evaluation device has a reference light sensor (14) which is connected to the mixing and distribution head (12) via an additional light guide (13 '), and that the measuring and evaluation device is set up to form the quotients from the measured values (U ₁ to U _n ) determined by the light sensors (9) and the reference measured value (t / _r ) determined by the reference light sensor (14). 4. Apparatus according to claim 3, characterized in that each light sensor (9) and the reference light sensor (14) is followed by a maximum value memory (16; 17) for storing the measured values (U ₁ to U _n ) or the reference measured value (U _r ) . 5. The device according to claim 4, characterized in that each of the light sensors (9) is associated with an up-down counter (19) which is controlled by a control circuit (24) such that it is generated by a pulse generator (21) pulses during a counts the stored measured value (U ₁ to U _n ) proportional and the reference measured value (U _r ) inversely proportional time when determining a test measured value in one counting direction and when determining a standard measured value in the other counting direction. 6. Apparatus according to claim 5, characterized in that each maximum value memory (16) is connected to a first input of a comparator (18), the output of which is connected to a control input of the associated up-down counter (19), and that the second The inputs of the comparators (18) are coupled to an integrator (20), the input of which is supplied with the reference measurement signal (U _r ). 7. Apparatus according to claim 5, characterized in that the pulse frequency of the pulse generator (21) is variable over time. 8. Apparatus according to claim 5, characterized in that each up-down counter (19) a logic circuit (22) is assigned which the count of the up-down counter (19) compares several different error limits.