CCD: How It Works & Intuitive Explanation

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In summary: My best guess is that they're too large. CCD pixels are only about six to a dozen microns or so in size, way too small for multiplier tubes. The pixels have to be that small to pick up...
  • #1
Clever Penguin
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I have read the textbook but it does not explain it in a very intuitive manner. This is the explanation (the bolded bits are the unintuitive bits):

Rectangular electrodes and an insulating layer are thin enough to allow light photons to pass through and liberate an individual electron in the light sensitive material underneath.

When collecting charge, the central electrode in each pixel is held at +10 V and the two outer electrodes at +2 V, which ensures that the liberated electrons accumulate under the central electrode.

After the pixels have collected charge for a certain time, the charge of each pixel is shifted towards the output electrode via the adjacent pixels. This is achieved by altering the voltage level of each electrode in a sequence of three step cycles.
 
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  • #2
Clever Penguin said:
After the pixels have collected charge for a certain time, the charge of each pixel is shifted towards the output electrode via the adjacent pixels. This is achieved by altering the voltage level of each electrode in a sequence of three step cycles.

Does this video help?

 
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  • #3
Andy Resnick said:
Does this video help?



Not really since youtube is blocked :sorry:
 
  • #6
Clever Penguin said:
I don't get it after the electrons are liberated and are 'captured' by the potential wells.

Are you referring to when the charge in each pixel is transferred to the next pixel over?
 
  • #7
Drakkith said:
Are you referring to when the charge in each pixel is transferred to the next pixel over?

Yes :smile:
 
  • #8
Clever Penguin said:
Not really since youtube is blocked :sorry:

why is it blocked ? I can view that video with no probs
 
  • #9
Clever Penguin said:
Yes :smile:

Alright, well, I'm not quite sure what to tell you. Let's start with the basic process of a voltage being applied to move the electrons from one pixel to another. Do you understand what that means?
 
  • #10
davenn said:
why is it blocked ? I can view that video with no probs
Me too
 
  • #11
davenn said:
why is it blocked ?
There are many possibilities:
  • The OP is 17, with a device presumably supplied by his parents. His parents applied parental controls on the device to blacklist youtube.
  • The OP uses his device at home, where his parents have blacklisted youtube at the router or modem level.
  • The OP uses his device at school, which has blacklisted youtube at the internet provider level.
One final possibility (easily discountable in this case) is that the OP lives in a country that has blacklisted youtube at the gateway level.
 
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  • #12
Drakkith said:
Alright, well, I'm not quite sure what to tell you. Let's start with the basic process of a voltage being applied to move the electrons from one pixel to another. Do you understand what that means?

I get that bit, yes. But I don't get why.

D H said:
There are many possibilities:

  • The OP uses his device at school, which has blacklisted youtube at the internet provider level.

Correct :smile:
 
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  • #13
Clever Penguin said:
I get that bit, yes. But I don't get why.

Electrons are charged particles. When you apply a voltage you exert a force on them that causes them to move. By applying this voltage in the right way, we can move the electrons from one pixel to another pixel to another until they wind up at the final pixel, which finally moves them into a charge amplifier to be "read out" by the electronics.
 
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  • #14
Drakkith said:
Electrons are charged particles. When you apply a voltage you exert a force on them that causes them to move. By applying this voltage in the right way, we can move the electrons from one pixel to another pixel to another until they wind up at the final pixel, which finally moves them into a charge amplifier to be "read out" by the electronics.

OK :smile:
 
  • #15
Drakkith said:
Electrons are charged particles. When you apply a voltage you exert a force on them that causes them to move. By applying this voltage in the right way, we can move the electrons from one pixel to another pixel to another until they wind up at the final pixel, which finally moves them into a charge amplifier to be "read out" by the electronics.

Why don't they just put some multiplier tubes underneath the pixels, connected to a computer, which can then produce an image on the screen since they know which pixel each tube corresponds to? Why do they have to shift it to the next pixel?
 
  • #16
Clever Penguin said:
Why don't they just put some multiplier tubes underneath the pixels, connected to a computer, which can then produce an image on the screen since they know which pixel each tube corresponds to? Why do they have to shift it to the next pixel?

My best guess is that they're too large. CCD pixels are only about six to a dozen microns or so in size, way too small for multiplier tubes. The pixels have to be that small to pick up the detail from the image formed by the optical system. Also, photomultiplier tubes are entirely different beasts from CCD's. They use a whole other method for picking up the light, so you would never have a photomultiplier hooked up to a CCD. Put simply, CCD's and photomultipliers perform the same function (detecting light and converting it to a digital signal) using different methods, and each has their strengths and weaknesses.
 
  • #17
Drakkith said:
My best guess is that they're too large. CCD pixels are only about six to a dozen microns or so in size, way too small for multiplier tubes. The pixels have to be that small to pick up the detail from the image formed by the optical system. Also, photomultiplier tubes are entirely different beasts from CCD's. They use a whole other method for picking up the light, so you would never have a photomultiplier hooked up to a CCD. Put simply, CCD's and photomultipliers perform the same function (detecting light and converting it to a digital signal) using different methods, and each has their strengths and weaknesses.

Thanks. That makes more sense. :smile:
 

1. What is CCD and how does it work?

CCD stands for Charge-Coupled Device and it is a type of sensor commonly used in digital cameras and image scanners. It works by converting light into electrical signals that can be processed and turned into digital images.

2. What are the main components of a CCD?

A CCD is composed of millions of light-sensitive cells (known as pixels) arranged in a grid. Each pixel contains a photosensitive material that converts light into an electrical charge. These charges are then transferred to a storage area called the output node, where they are read and converted into a digital signal.

3. How does a CCD capture color images?

A CCD can only capture grayscale images, so in order to produce a color image, it uses a color filter array (CFA) on top of the pixels. This array is made up of red, green, and blue filters that allow only certain wavelengths of light to reach each pixel. When the image is processed, the data from each pixel is combined to create a full color image.

4. What is the difference between CCD and CMOS sensors?

Both CCD and CMOS sensors are used in digital cameras, but they work in slightly different ways. CCD sensors use a complex manufacturing process and typically offer better image quality and lower noise levels. CMOS sensors, on the other hand, are simpler and less expensive to produce, but they may have lower image quality and higher noise levels.

5. Can CCD sensors be used for video recording?

Yes, CCD sensors can be used for video recording. However, they are not as commonly used as CMOS sensors in video cameras due to their slower readout speeds. This means that CMOS sensors are better suited for capturing fast-moving objects, making them ideal for video recording.

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