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GB2126828A - Camera tube aperture compensation - Google Patents

Camera tube aperture compensation Download PDF

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Publication number
GB2126828A
GB2126828A GB08225708A GB8225708A GB2126828A GB 2126828 A GB2126828 A GB 2126828A GB 08225708 A GB08225708 A GB 08225708A GB 8225708 A GB8225708 A GB 8225708A GB 2126828 A GB2126828 A GB 2126828A
Authority
GB
United Kingdom
Prior art keywords
colour
correction signal
camera
tubes
tube
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB08225708A
Other versions
GB2126828B (en
Inventor
Philip Rangecroft Groves
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Link Electronics Ltd
Original Assignee
Link Electronics Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Link Electronics Ltd filed Critical Link Electronics Ltd
Priority to GB08225708A priority Critical patent/GB2126828B/en
Publication of GB2126828A publication Critical patent/GB2126828A/en
Application granted granted Critical
Publication of GB2126828B publication Critical patent/GB2126828B/en
Expired legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/14—Picture signal circuitry for video frequency region
    • H04N5/20—Circuitry for controlling amplitude response
    • H04N5/205—Circuitry for controlling amplitude response for correcting amplitude versus frequency characteristic
    • H04N5/208—Circuitry for controlling amplitude response for correcting amplitude versus frequency characteristic for compensating for attenuation of high frequency components, e.g. crispening, aperture distortion correction
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N9/00—Details of colour television systems
    • H04N9/64—Circuits for processing colour signals
    • H04N9/646—Circuits for processing colour signals for image enhancement, e.g. vertical detail restoration, cross-colour elimination, contour correction, chrominance trapping filters

Landscapes

  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Color Television Image Signal Generators (AREA)

Abstract

This invention provides apparatus comprising means for deriving a correction signal from the combined outputs of the colour tubes of a colour camera and control means for applying the correction signal to each of the colour tubes so as to compensate for reduction in depth of modulation of the colour tube images and the reduction of spatial frequencies caused by aperture effects of the scanning beams. The provision of a correction signal derived from the combined outputs of the colour tubes of the colour camera tubes avoids the presentation of soft pictures from scenes having a low green content. Edge errors are avoided in the final image by providing accurate registration of the camera tubes.

Description

SPECIFICATION Camera tube aperture compensation The present invention relates to a method and apparatus for camera aperture compensation.
In a television camera the depth of modulation present in the image is rapidly reduced for larger aperture settings. At large aperture settings it is therefore necessary to boost the detail available in the image and in particular it is preferable that the depth of modulation should be constant over the whole of the pass band. A very significant problem is the reduction of spatial frequencies caused by aperture effects of the scanning beam.
Conventionally, in a colour television camera a correction signal is determined from the output of the greem camera tube. The correction signal is phase corrected and is added to the output from each of the three colour camera tubes. This conventional method of compensation is relatively successful because the average television scene includes a high green content.
However, for certain types of scene, especially prevalent in entertainment type programmes, the green content of the scene is low. This reduces the effectiveness of the correction signal and results in a soft picture.
The present invention seeks to mitigate the above described disadvantages.
According to a first aspect of the present invention there is provided apparatus for camera aperture compensation comprising means for combining the outputs of the colour tubes, means for deriving a correction signal from the combined outputs of the colour tubes, and control means for applying the correction signal to the output of each colour tube so as to compensate the colour tube images.
According to a second aspect of the present invention there is provided a method of camera aperture compensation comprising combining the outputs of the colour tube deriving correction signal, from the combined outputs and applying the correction signal to the output of each of the three colour tubes.
An embodiment of the present invention will now be described by way of example only.
In order to compensate for the reduction in depth of modulation of a colour television camera and for reduction in spatial frequencies due to aperture effects of the scanning beam, it is known to derive a correction signal from the green colour camera tube. A single phase corrected correction signal is then added to the output from all three colour tubes.
In contrast, the present invention combines the output of the colour tube and derives therefrom a correction signal for each of the colour tubes. This method can lead to edge information from the three colour camera tubes being present in the final image which would be manifest as edge errors. However, it is possible to obtain registration between the images of the colour camera tubes to an accuracy of 0.05% in which case edge errors do not appear in the final image.
The correction signal is derived from the combined colour signals in the same manner as the correction signal is conventionally derived from the green colour camera tube.
Claims
1. Apparatus for camera aperture compensation comprising means for combining the outputs of the colour tubes, means for deriving correction signal from the combined outputs of the colour tubes, and control means for applying the correction signal to the output of each colour tube so as to compensate for reduction in depth of modulation for the images of the respective colour tubes.
2. A method of camera aperture compensation comprising combining the outputs of the colour tubes deriving for the combined outputs a correction signal, and applying the correction signal to the output of each of the three colour tubes.
3. Apparatus for camera aperture compensation substantially as hereinbefore described.
4. A method of camera aperture compensation substantially as hereinbefore described.
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Camera tube aperture compensation The present invention relates to a method and apparatus for camera aperture compensation. In a television camera the depth of modulation present in the image is rapidly reduced for larger aperture settings. At large aperture settings it is therefore necessary to boost the detail available in the image and in particular it is preferable that the depth of modulation should be constant over the whole of the pass band. A very significant problem is the reduction of spatial frequencies caused by aperture effects of the scanning beam. Conventionally, in a colour television camera a correction signal is determined from the output of the greem camera tube. The correction signal is phase corrected and is added to the output from each of the three colour camera tubes. This conventional method of compensation is relatively successful because the average television scene includes a high green content. However, for certain types of scene, especially prevalent in entertainment type programmes, the green content of the scene is low. This reduces the effectiveness of the correction signal and results in a soft picture. The present invention seeks to mitigate the above described disadvantages. According to a first aspect of the present invention there is provided apparatus for camera aperture compensation comprising means for combining the outputs of the colour tubes, means for deriving a correction signal from the combined outputs of the colour tubes, and control means for applying the correction signal to the output of each colour tube so as to compensate the colour tube images. According to a second aspect of the present invention there is provided a method of camera aperture compensation comprising combining the outputs of the colour tube deriving correction signal, from the combined outputs and applying the correction signal to the output of each of the three colour tubes. An embodiment of the present invention will now be described by way of example only. In order to compensate for the reduction in depth of modulation of a colour television camera and for reduction in spatial frequencies due to aperture effects of the scanning beam, it is known to derive a correction signal from the green colour camera tube. A single phase corrected correction signal is then added to the output from all three colour tubes. In contrast, the present invention combines the output of the colour tube and derives therefrom a correction signal for each of the colour tubes. This method can lead to edge information from the three colour camera tubes being present in the final image which would be manifest as edge errors. However, it is possible to obtain registration between the images of the colour camera tubes to an accuracy of 0.05% in which case edge errors do not appear in the final image. The correction signal is derived from the combined colour signals in the same manner as the correction signal is conventionally derived from the green colour camera tube. Claims
1. Apparatus for camera aperture compensation comprising means for combining the outputs of the colour tubes, means for deriving correction signal from the combined outputs of the colour tubes, and control means for applying the correction signal to the output of each colour tube so as to compensate for reduction in depth of modulation for the images of the respective colour tubes.
2. A method of camera aperture compensation comprising combining the outputs of the colour tubes deriving for the combined outputs a correction signal, and applying the correction signal to the output of each of the three colour tubes.
3. Apparatus for camera aperture compensation substantially as hereinbefore described.
4. A method of camera aperture compensation substantially as hereinbefore described.
GB08225708A 1982-09-09 1982-09-09 Camera tube aperture compensation Expired GB2126828B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB08225708A GB2126828B (en) 1982-09-09 1982-09-09 Camera tube aperture compensation

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB08225708A GB2126828B (en) 1982-09-09 1982-09-09 Camera tube aperture compensation

Publications (2)

Publication Number Publication Date
GB2126828A true GB2126828A (en) 1984-03-28
GB2126828B GB2126828B (en) 1987-01-14

Family

ID=10532797

Family Applications (1)

Application Number Title Priority Date Filing Date
GB08225708A Expired GB2126828B (en) 1982-09-09 1982-09-09 Camera tube aperture compensation

Country Status (1)

Country Link
GB (1) GB2126828B (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2583244A1 (en) * 1985-06-05 1986-12-12 Thomson Video Equip DEVICE FOR CORRECTING CONTOURS IN AN IMAGE AND USE OF SUCH A DEVICE IN A COLOR TELEVISION CAMERA

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1291967A (en) * 1970-04-16 1972-10-04 Fernseh Gmbh Television camera systems
GB1387302A (en) * 1971-02-19 1975-03-12 Rca Corp Contrast compression circuits
GB1417181A (en) * 1972-01-14 1975-12-10 Emi Ltd Colour television cameras

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1291967A (en) * 1970-04-16 1972-10-04 Fernseh Gmbh Television camera systems
GB1387302A (en) * 1971-02-19 1975-03-12 Rca Corp Contrast compression circuits
GB1417181A (en) * 1972-01-14 1975-12-10 Emi Ltd Colour television cameras

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2583244A1 (en) * 1985-06-05 1986-12-12 Thomson Video Equip DEVICE FOR CORRECTING CONTOURS IN AN IMAGE AND USE OF SUCH A DEVICE IN A COLOR TELEVISION CAMERA
EP0206881A1 (en) * 1985-06-05 1986-12-30 Thomson Video Equipement Contours correction circuit in an image and use of such a circuit in a colour television camera
US4748500A (en) * 1985-06-05 1988-05-31 Thomson Video Equipment Device for correcting contours in an image and use of such a device in a color television camera

Also Published As

Publication number Publication date
GB2126828B (en) 1987-01-14

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Legal Events

Date Code Title Description
746 Register noted 'licences of right' (sect. 46/1977)
PCNP Patent ceased through non-payment of renewal fee