Optical reduction of luminance to chrominance crosstalk in color television cameras

Claim 2

In a color television camera utilizing a spatial colorencoding filter in the optical path of a camera pickup tube to separate the light from a scene to be televised into its constituent colors, apparatus for reducing the luminance-tochrominance signal crosstalk, comprising: a single astigmatic filter having alternate and parallel strips of different transmissivity for filtering light passing therethrough disposed in said optical path of said pickup tube between said scene to be televised and said color encoding filter whereby; and the spacing between said alternate and parallel strips determines the spatial frequency response of the light from said scene impinging upon said color filter, said spacing being selected such that the highest frequency luminance signal components obtained from said pickup tube are below the lowest carrier frequency of the color signal components.

Claim 3

Apparatus according to claim 1 wherein said astigmatic filter is a grating having its alternate strips of lesser transmissivity of greater width than its alternate strips of grEater transmissivity, said grating being disposed at the exit pupil of the objective lens of said camera.

Claim 4

Apparatus according to claim 2 wherein the width of said strips of greater transmissivity is such that the spatial cutoff frequency of the light passing through said grating is around the carrier frequency of the lowest color component signal derived from saId color-encoding filter.

Claim 5

Apparatus according to claim 3 wherein said grating is further disposed such that said parallel and alternate strips are perpendicular to the direction of the scanning lines at the target of said pickup tube, whereby the luminance signals of a frequency higher than said lowest color component carrier frequency in the direction of said scanning lines are reduced.

Claim 6

In a color television camera including a color-encoding filter in the optical path of said camera for separating light from a scene to be televised into color component signals at different carrier frequencies at the photosensitve element of an image pickup tube of said camera, apparatus for reducing the luminance-to-chrominance signal crosstalk comprising a single astigmatic filter disposed in said optical path ahead of said color-encoding filter for determining the spatial frequency response of the light reaching said color-encoding filter such that said spatial frequency response is in a direction of the scanning lines of said pickup tube and is selected such that the highest frequency luminance signal components obtained from said pickup tube are below the lowest frequency color carrier frequency.

Claim 7

In a color television camera including a color-encoding filter in the optical path of said camera for separating light from a scene to be televised into color component signals at different carrier frequencies at the photosensitve element of an image pickup tube of said camera, apparatus for reducing the luminance-to-chrominance signal crosstalk comprising a single astigmatic filter disposed in said optical path ahead of said color-encoding filter for determining the spatial frequency response of the light reaching said color-encoding filter such that said spatial frequency response is in a direction of the scanning lines of said pickup tube and is selected such that the highest frequency luminance signal components obtained from said pickup tube are below the lowest frequency color carrier frequency.

Claim 8

Apparatus according to claim 5 wherein said astigmatic filter includes alternate and parallel strips of different transmissivity.

Claim 9

Apparatus according to claim 6 wherein said strips are of unequal width.

Claim 10

Apparatus according to claim 7 wherein said alternate strips of lesser transmissivity are of greater width than said strips of greater transmissivity.

Claim 11

Apparatus according to claim 7 wherein said astigmatic filter is disposed at the exit pupil of the camera lens.

Claim 12

Apparatus according to claim 6 wherein said parallel strips are disposed perpendicular to the direction of the scanning lines of said pickup tube.

Claim 13

Apparatus according to claim 10 wherein said astigmatic filter means comprises a grating having alternate and parallel strips of different transmissivity.

Claim 14

Apparatus according to claim 11 wherein said astigmatic filter means is further disposed at the exit pupil of said camera lens.

Claim 15

Apparatus according to claim 12 wherein said alternate strips of lesser transmissivity are of greater width than said alternate strips of greater transmissivity.

Claim 16

Apparatus according to claim 14 wherein said astigmatic filter means is further disposed such that said strips are perpendicular to the scanning lines of said pickup tube whereby said spatial frequency spectrum response in a direction of said scanning lines is determined by said astigmatic filter means.

Claim 17

In a color television camera including a lens, a spatial color-encoding filter for dividing light from an object into color component signals at different carrier frequencies; an image pickup tube; said lens, color encoding filter and pickup tube being disposed in the optical path of said camera in the order named, apparatus for reducing the luminance-to-chrominance signal crosstalk comprising: a single astigmatic filter having alternate and parallel strips of different transmissivity disposed in said optical path for producing a spatial frequency response of an image in the plane of said color-encoding filter such that said spatial frequency response is minimum at that portion of the spatial frequency spectrum including the color component carrier frequencies spectrum including the color component carrier frequencies of said color-encoding filter and is maximum for the luminance signal components.

Claim 18

In a color television camera including a lens, a spatial color-encoding filter for dividing light from an object into color component signals at different carrier frequencies; an image pickup tube; said lens, color encoding filter and pickup tube being disposed in the optical path of said camera in the order named, apparatus for reducing the luminance-to-chrominance signal crosstalk comprising: a single astigmatic filter having alternate and parallel strips of different transmissivity disposed in said optical path for producing a spatial frequency response of an image in the plane of said color-encoding filter such that said spatial frequency response is minimum at that portion of the spatial frequency spectrum including the color component carrier frequencies spectrum including the color component carrier frequencies of said color-encoding filter and is maximum for the luminance signal components.

Claim 19

Apparatus according to claim 14 wherein said strips are of unequal width.