“Spot Wobble” Unlines TV Picture (Jul, 1957)

This is one of those weird artifacts of imaging that is still true on computers today. Applying some sorts of a blur to an image can make it actually appear sharper.

“Spot Wobble” Unlines TV Picture

Vast improvement in TV pictures is predicted by Westinghouse if the “spot wobble” method of horizontal line scanning is introduced. TV viewers are all familiar with the black and white lines that make up the picture. A viewer too close to the receiver can see the lines (ten feet is optimum for a 24″ screen). This can be remedied by slightly wobbling the scanning spot in the picture tube so that a broader line is rendered for better quality at a closer viewing distance.

  1. Hirudinea says: February 15, 20125:37 pm

    They make the picture better by reducing precision, thats clever. Sometimes perfection isn’t the best solution.

  2. G. L. Tyrebyter says: February 16, 20121:01 am

    While this never worked for active TV since the “wobble” was perceptible in the picture as a slight vertical jitter. In the early 80′s Matrix Instruments made a video to film imager that digitally stepped a DC component in the vertical scan of a video display. This essentially filled in the scan lines on the film image. It did make the image sharper to the eye. This was not a loss in image data but actually filled in the missing image space with redundant information.

  3. Sean says: February 16, 20129:10 am

    I forget which spacecraft it was, (Maybe the Constellation before they cancelled it?), but designers realized that the vibration of the craft would make it nearly impossible for astronauts to read their screens. To correct this, they figured out the frequency of the the vibration and set the screens to flicker on and off in time with it.

  4. Christian Berger says: February 16, 20121:29 pm

    Actually it was employed in the British EMI 405 line system. If you make the spot wobble with a high frequency. It doesn’t make the image more blurry, you could do that easily by adjusting the focus on the TV-set, however it makes the spot wider while still keeping the edges sharp. In a nutshell that is primitive reconstruction filter.

    You can see it at the top of the hat. It looks “pixely”. The impulse response of the wobbled spot is nearly rectangular.

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