Color grading apparatus with temperature sensor to compensate for lamp brightness

Claim 1

IN COLOR GRADING APPARATUS THE COMBINATION OF AN ELECTRIC DISCHARGE DEVICE COMPRISING AN ELONGATED VITREOUS TUBE HAVING AN ATMOSPHERE OF RARIFIED GAS, SAID TUBE BEING OF SUBSTANTIALLY CIRCULAR SHAPE, A HOUSING, A WALL MEMBER EXTENDING ACROSS SAID HOUSING AND FORMING AN ANNULAR CAVITY FOR SAID TUBE, SAID HOUSING COMPRISING OUTER WALL STRUCTURE AND INNER WALL STRUCTURE SPACED THEREFROM, HEAT INSULATING MATERIAL POSITIONED BETWEEN SAID WALL STRUCTURES, SAID WALL MEMBER HAVING A HOLE THERETHROUGH SUBSTANTIALLY IN THE CENTRAL PART THEREOF, LIGHT FILTER MEANS POSITIONED IN ALIGNMENT WITH SAID HOLE FOR SELECTING SUBSTANTIALLY MONOCHROMATIC LINES FROM THE LIGHT PRODUCED BY SAID ELECTRIC DISCHARGE DEVICE, SAID HOUSING HAVING TOP WALL STRUCTURE DEFINING A WELL INTO WHICH THE SAMPLE TO BE COLOR GRADED IS INSERTED, THE BOTTOM OF SAID WELL BEING OPEN SO THAT LIGHT PRODUCED BY SAID ELECTRIC DISCHARGE DEVICE IMPINGES SAID SAMPLE AND IS REFLECTED FROM SAID SAMPLE INTO SAID HOLE AND FILTER MEANS, A LIGHT SENSITIVE CELL POSITIONED UNDER SAID FILTER MEANS TO RECEIVE LIGHT REFLECTED FROM SAID SAMPLE AND PASSING THROUGH SAID FILTER MEANS, AN AMPLIFIER HAVING A PLURALITY OF STAGES, SAID AMPLIFIER HAVING THE INPUT THEREOF CONNECTED TO SAID LIGHT SENSITIVE CELL, AN INDICATING DEVICE CONNECTED TO THE OUTPUT OF SAID AMPLIFIER FOR INDICATING THE MAGNITUDE OF LIGHT ENERGIZATION OF SAID CELL, AND MEANS CONNECTED TO THE CATHODE CIRCUIT OF ONE OF SAID AMPLIFIER STAGES FOR CONTROLLING THE CATHODE BIAS OF SAID STAGE INVERSELY IN ACCORDANCE WITH THE TEMPERATURE OF SAID ELECTRIC DISCHARGE DEVICE.