How to choose the underwater camera, lens and signal transmission method?

1. The refraction of water and the choice of the optical system

Because water refracts more than air, the viewing angle of a TV camera is a quarter narrower in water than in air. three-quarters of that in air. In order to observe the subject in a wider range, the camera of the underwater TV must choose a wide-angle lens. In addition, the lens is required to have the highest possible transmittance.

2. Sensitivity and camera selection

Due to the lack of brightness in the water, it is possible to compensate with artificial lighting. However, it is also very important to improve the camera's sensitivity, so the selection of the camera needs to be considered.

In the past, light guide tubes that were easy to adjust were generally used. But it falls short in image retention, and sensitivity. At present, CCD cameras are mostly used. Because of their advantages of small size, lightweight, low power consumption, good reliability, no burn phenomenon, anti-seismic, and wide spectral response, they are being widely used. And because of the variety, you can also choose a high-sensitivity CCD camera.

3. Consideration of video signal transmission mode

The maneuverability of underwater TV cameras is much less than that on land, so the transmission of video signals has to be considered in many ways. The transmission of image signals usually uses coaxial cables. The bandwidth of the image signals of TV cameras is usually from DC to several megahertz. When used at depths of several kilometers, the high-frequency level of the signal sent by the camera must be increased. High-frequency compensation is also adopted at the receiving end. No matter how deep the depth is, the frequency modulation method or the pulse code modulation method should be considered to prevent the signal from deteriorating during transmission.

In addition, narrow-band systems can also be considered using ultrasound to transmit images or laser transmission.