Television cameras

Claim 2

A television camera comprising a pick-up element (1), an iris (2), a variable gain amplifier (4) for a picked-up signal, and first and second comparators (7, 8) to compare the video level of the picked-up signal to be supplied to a pick-up signal system following said variable gain amplifier (4) with first and second reference levels and respectively supply first and second compared output signals therefrom to said iris (2) and said variable gain amplifier (4) for controlling them thereby to form a first and second automatic control loops (12, 13), characterised in that when the amount of light incident on said pick-up element (1) is above a predetermined value, only said first automatic control loop (12) is actuated and when the amount of light incident on said pick-up element (1) is below said predetermined value, only said second automatic control loop (13) is actuated.

Claim 3

A television camera according to claim 1 wherein said first automatic control loop (12) comprises a level detector (11) coupled to the output of said variable gain amplifier (4), a first comparator (7) receiving inputs from said level detector (11) and a first variable reference voltage signal source (9) and supplying an output signal to control said iris (2), and said second automatic control loop (13) comprises said level detector (11), a second comparator (8) receiving inputs from said level detector (11) and a second variable reference voltage signal source (10) and supplying an output signal, and a selecting circuit (14) receiving said output signal from said second comparator (8) and a signal from a switching circuit (17) which can supply either of two reference voltage signals, said selecting circuit supplying an output signal to control the gain of said variable gain amplifier (4).

Claim 4

A television camera according to claim 2 wherein said selecting circuit (14) comprises two transistors (Q 1 Q 2 ) with their collector-emitter paths connected in parallel to a common emitter resistor (R), said output signal from said second comparator (8) being supplied to the base of one of said transistors ( Q l ) and said signal from said switching circuit (17) being supplied to the base of the other of said transistors (Q 2 ), said output signal from said selecting circuit (14) being derived from the emitters of said transistors ( Qi, Q 2 ).

Claim 5

A television camera according to claim 3 wherein said iris (2) has an automatic mode and a manual mode, and said signal from said switching circuit (17) is derived from a third variable reference voltage source (15) in one said mode and is earth potential in the other said mode.

Claim 6

A television camera comprising a pick-up element (1), an iris (2), a variable gain amplifier (4) for a picked-up signal, and first and second comparators (7, 8) to compare a video level of the picked-up signal to be supplied to a pick-up signal system following said variable gain amplifier (4) with first and second reference levels and respectively supply first and second compared output signals therefrom to said iris (2) and to said variable gain amplifier (4) for controlling them, characterised by a selecting circuit (14) for comparing a level of said second compared output signal with a third reference level and for selecting the signal of either level to be supplied to said variable gain amplifier (4), thereby forming first and second automatic control loops (12, 13) operative such that when the amount of light incident on said pick-up element (1) is above a predetermined value, said first automatic control loop (12) is actuated to control said iris (2) and when the amount of light incident on said pick-up element 1 is below said predetermined value, said second automatic control loop (13) .is actuated to control said variable gain amplifier (4).

Claim 7

A television camera comprising a pick-up element (1), an iris (2), a variable gain amplifier (4) for a picked-up signal, and first and second comparators (7, 8) to compare a video level of the picked-up signal to be supplied to a pick-up signal system following said variable gain amplifier (4) with first and second reference levels and respectively supply first and second compared output signals therefrom to said iris (2) and to said variable gain amplifier (4) for controlling them, characterised by a selecting circuit (14) for comparing a level of said second compared output signal with a third reference level and for selecting the signal of either level to be supplied to said variable gain amplifier (4), thereby forming first and second automatic control loops (12, 13) operative such that when the amount of light incident on said pick-up element (1) is above a predetermined value, said first automatic control loop (12) is actuated to control said iris (2) and when the amount of light incident on said pick-up element 1 is below said predetermined value, said second automatic control loop (13) .is actuated to control said variable gain amplifier (4).

Claim 8

A television camera comprising a pick-up element (1), an iris (2), a variable gain amplifier (4) for a picked-up signal, and first and second comparators (7, 8) to compare a video level of the picked-up signal with first and second reference levels and respectively supply first and second compared output signals therefrom to said iris (2) and said variable gain amplifier (4) for controlling them, characterised by a selecting means (14) for comparing the level of said second compared output signal with a third reference level and for selecting one or the other to be supplied to said variable gain amplifier (4), and a controlling means (17) for ON/OFF controlling said selecting means (14) thereby to form said first and second automatic control loops (12, 13), whereby when the light incident on said pick-up element (1) is above a predetermined value said first automatic control loop (12) is actuated, and when the light incident on said pick-up element (1) is below said predetermined value said second automatic control loop (13) is actuated.

Claim 9

A television camera comprising a pick-up element (1), an iris (2), a variable gain amplifier (4) for a picked-up signal, and first and second comparators (7, 8) to compare a video level of the picked-up signal with first and second reference levels and respectively supply first and second compared output signals therefrom to said iris (2) and said variable gain amplifier (4) for controlling them, characterised by a selecting means (14) for comparing the level of said second compared output signal with a third reference level and for selecting one or the other to be supplied to said variable gain amplifier (4), and a controlling means (17) for ON/OFF controlling said selecting means (14) thereby to form said first and second automatic control loops (12, 13), whereby when the light incident on said pick-up element (1) is above a predetermined value said first automatic control loop (12) is actuated, and when the light incident on said pick-up element (1) is below said predetermined value said second automatic control loop (13) is actuated.