Patent GB-1068348-A (GB)
Title: An electronic computer
IPC: G06G7/75
Filed: 1963-10-18
Abstract: 1068348 Electric selective signalling; electric analogue calculating CIBA Ltd 18 Oct 1963 [19 Oct 1962 26 Sept 1963] 41313/63 Headings G4D D6Y D6C2 and D7X An electronic computer computes the integral of XZ/Y by providing pulses at a rate proportional to Z, each pulse (a) closing a switch to gate clockpulses to a counter and (b) starting an integrator fed with Y, the integrator output being compared with X and the comparator opening the switch. A constant multiplicative factor may be inserted in the integrand denominator by pre-selecting the integrator time-constant. The invention relates to the evaluation of integrals of expressions of the type:- needed for the determining of dyeing recipes by colorimetric measuring of the sample to be copied, F(X) being the modified Kubelka-Munk function, viz: where R(#) is the measured reflectance curve of the sample and r the residual reflectance of the sample when dyed completely black. The integration is performed by adding together digitally time intervals representing the values of F(X) for particular wavelengths # selected in accordance with E A (#)x(#). In Fig. 1, six integrals like the above (see Specification) are evaluated simultaneously, some circuit components being provided six times in parallel, as indicated by "(a-f)" in Fig. 1, for this purpose. A spectrophotometer 1 provides the curve R(X) of the sample to be copied as a varying voltage Ruo (where uo is a constant voltage) at the inputs 3, 5 of two analogue circuit branches I, II. The input to branch I is inverted at 9, and then added to a voltage uo at 11, the result being amplified by an amplifier 13 (gain A) and squared at 15, the result u o .(1-R)<SP>2</SP>.A<SP>2</SP> being fed to comparators 33(a-f). The input to branch II has a voltage -u 0 r supplied by parameter switch 23 added to it at 21, the result being amplified (gain B) at 19 and then fed to integrators 17(a-f) to be integrated. The integrator time constants are all fixed at :- by parameter switch 23. The integrator outputs are supplied to the comparators 33(a-f). Pulse transmitters 7(a-f) controlled by the spectrophotometer 1 zeroize the integrators 17(a-f) and open pulse gates 39(a-f) as each wavelength A selected for the integration comes up. The comparators 33(a-f) close the respective pulse gates 39(a-f) when their two inputs are equal. When gates 39(a-f) are open, clockpulses from a generator 43 pass via pulse dividers 47(a-f) into counters 45(a-f) possessing luminous digit display. The (adjustable) amplifier gains A, B are chosen so that the maximum inputs (along the whole R curve) to the squarer 15 and integrators 17(a-f) are both u 0 , to optimize performance. The integrals can each be obtained in a form multiplied by a factor representing pigment concentration in the measured sample by connecting amplifiers 49(a-f) between the integrators 17(a-f) and the comparators 33(a-f). The values of the integrals for the undyed substrate of the sample can be subtracted from the calculated integrals by the use of coincidence stages 51(a-f) which zeroize the counters 45(a-f) when the latter first reach the numbers stored in the respective coincidence stages 51(a-f). The standard colour co-ordinates of colour shades may be calculated with the system shown by operating the changeover switches 53, 55, 57, 59(a-f) to their other positions, thus shorting branch I, connecting voltage u 0  to the integrator inputs. setting the integrator time constant at To and disconnecting coincidence-stages 51(a-f). A simple non-linear circuit for performing all the functions of branch (I) is shown in Fig. 3a (not shown).