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• Radiation Tolerance

Frequently Asked Questions

1 What makes a camera radiation tolerant?

2  Why can't I use a solid state CCD camera in radiation environments?

3 How much light does a camera need?

4 Why can't I see details in dark places when very bright objects are in view?

5 You offer LED and tungsten halogen lamps. Which is best?

6 How do I know which lens to choose?

7 What is the shortest distance from the camera that I can focus on?

8 What is the longest cable length I can use with your cameras?

9 Is there any way of extending the cable length?

10 What is multiplexed control?

11 What is the advantage of multiplexed control?

12 Do Raditec cameras have macro mode?

13 Is a radiation tolerant camera the only way of looking into a radiation area?

14 What source do you use to prove your cameras are radiation tolerant?

1  What makes a camera radiation tolerant?
The image sensor in the camera is a thermionic tube made entirely of glass and metal. The electronic circuits which control the tube and process the signal are designed using specially selected components and techniques which allow them to tolerate the effects of radiation. The materials used in the construction of the camera are also chosen for their tolerance to radiation. We know the components and materials are radiation tolerant because we have tested them in our own gamma radiation cell. We also draw on our many years experience in radiation effects work to design cameras and systems.

2 Why can't I use a solid state CCD camera in radiation environments?
If the radiation dose rate or integrated dose is low then you can. However radiation will create noise on the picture, visible as a white "snow" effect. It will also steadily destroy the CCD camera and cause it to fail much more quickly than in its normal environment. In high levels of radiation the noise will be so prominent that the camera will be unusable and it may be destroyed in minutes. Radiation tolerant cameras use different technology and will not only give good pictures in much higher levels of radiation but will also last very much longer than solid state cameras.

 

3  How much light does a camera need?
A radiation tolerant camera needs 150 lux at the camera on the scene being viewed. Pictures can be obtained with light levels down to 30 lux but the quality of the picture will deteriorate. For tasks such as detailed inspection higher light levels improve the usability of the image. Typical light levels: Well lit office 600 lux, Sunshine outdoors UK 1500 to 2000 lux, Dark corridor 20 lux. Note that the lux measurement refers to the light going towards the camera, not that falling on the scene.

 

4  Why can't I see details in dark places when very bright objects are in view?
There is too much contrast in the scene. Very bright illumination, especially on metal or other reflective materials results in bright spots which are beyond the camera range. To obtain good pictures arrange the lighting to be indirect, reflected from the wall or ceiling or use diffusers over the lamp.

 

5  You offer LED and tungsten halogen lamps. Which is best?
LED lamps are low powered and efficient. Their color coincides with the cameras' peak sensitivity. They are useful up to a few meters, for example for close inspection work. Tungsten halogen lamps give much more light and are useful over greater viewing distances, up to 15 or 20 meters, but they use more power and get hot.

 

6  How do I know which lens to choose?
Look at the scene. Measure the width of the scene you wish to see and its distance from the camera. Then using simple trigonometry calculate the angle of view. This is the viewing angle in the lens data sheet. If you need further information or an answer to a specific question please send us your enquiry using the contact us form.

 

7  What is the shortest distance from the camera that I can focus on?
Raditec surveillance cameras like the CR2225 are normally set so that they focus between 0.5m and infinity though the closest focus distance varies between lens type. Our inspection cameras, for example the CR2224, are normally set so that they give good focus down to 50mm or less from the camera. We can usually provide an optical system which will meet customers needs. If you have a specific requirement please send us your details using the contact us form.

 

8  What is the longest cable length I can use with your cameras?
We normally recommend 150m maximum length, although we know of customers who have used our cameras with much longer cables. The problems associated with using longer cables are loss of resolution in the picture i.e. small detail becomes blurred-out and some loss of control functions can be experienced if multiplexed control is used (see below). These effects are due to attenuation of high frequencies in the cable.

 

9  Is there any way of extending the cable length?
Yes. We can provide line drivers to overcome the cable problems using copper or fibre-optic cables.

 

10 What is multiplexed control?
This is a method of sending control signals to cameras and accessories such as pan and tilt units, lights etc using the video cable to carry the information. It is commonly used in the security surveillance industry. Raditec has a version which is radiation tolerant at the camera end.

 

11 What is the advantage of multiplexed control?
The number of cores in the camera cable is reduced. As radiation tolerant cables tend to be rather stiff, a reduction in cable size is a great advantage during installation and maintenance.

 

12 Do Raditec cameras have macro mode?
Our cameras are equipped with internal movement mechanisms allowing very close focusing and some magnification. If you let us know what you want to see using the contact us form we can usually provide a suitable lens.

 

13 Is a radiation tolerant camera the only way of looking into a radiation area?
No. Raditec also manufacture periscopes which are placed into the radiation area for example by passing through the shield wall. These are designed for specific applications and can incorporate special optical systems for inspection work. Infa-red cameras can also be used with special deployment mechanisms.

 

14 What source do you use to prove your cameras are radiation tolerant?
We test and prove our cameras and the equipment that goes into them using a Cobalt 60 1MeV gamma source in our own irradiation facility.