How do digital cameras capture images using the photoelectric effect?

In summary, digital cameras work by exposing a sensor to light and measuring the amount of current that flows. This current is proportional to the intensity of light received, allowing cameras to capture images with varying levels of light.
  • #1
jabers
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So they use the photoelectric effect right? Does that mean when the camera takes a picture it allows photons of light to interact with a sensor for a certain period of time? How does that create the picture? If i understand it correctly the different photons have different frequencies and their wavelengths correspond with colors. Any more insight or corrections would be very much appreciated.
 
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  • #2
The simplest possible photo detector works thusly. You basically have a diode with reverse bias applied to it. The current can't flow, because there are no carriers (electrons or "holes") in the depletion region. (Look up diode for details.) However, if a photon strikes one of the electrons and excites it into the conduction band, you end up with a free electron and a free hole, which will immediately flow in opposite directions. If you have enough photons striking the depletion region, you'll have a current flowing. The current will depend primarily on the intensity of light, allowing you to measure it. I'm sure the rest is self-evident.

Oh, the idea here is that so long as the energy is sufficient to knock out an electron, a higher energy doesn't make much difference. The low threshold for cameras is usually in near-IR region (about 900nm), so all visible light produces roughly equal effect. To get color, there is a filter mosaic overlaid on the sensor.
 
  • #3
jabers said:
So they use the photoelectric effect right? Does that mean when the camera takes a picture it allows photons of light to interact with a sensor for a certain period of time? How does that create the picture? If i understand it correctly the different photons have different frequencies and their wavelengths correspond with colors. Any more insight or corrections would be very much appreciated.

Yes - it's 'a' photoelectric effect in which electrons are 'moved about' by photons but many digital (compact and movie) cameras expose the sensors to the incoming light continuously (they don't use a shutter as with a film camera). Each sensor delivers a signal which is proportional to the intensity of light (rather than the energy admitted in 1/125 of a second). The signal is 'read' by the camera circuitry at the time you make the exposure and over a short period (the 'exposure' time). This arrangement is simple and cheap but suffers from the fact that the sensor is exposed to light all the time and low light performance suffers. Posh cameras (SLR for example) use a shutter, as with film cameras, and the sensors only get a short burst of light energy. Along with the fact that the sensors are larger area than in compact cameras, the different system gives much better low light performance.
Here's a pretty description of digital camera workings: "[URL htm"]http://www.cambridgeincolour.com/tutorials/camera-sensors. htm[/URL]
 
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Related to How do digital cameras capture images using the photoelectric effect?

1. How does a digital camera capture an image?

A digital camera captures an image by using a sensor made up of millions of tiny photosensitive cells called pixels. When light enters the camera through the lens, it hits the pixels on the sensor, and each pixel records the amount of light it receives. This information is then converted into digital data, which creates an image.

2. What is the role of the lens in a digital camera?

The lens in a digital camera is responsible for focusing the incoming light onto the sensor. It works similarly to the lens in a traditional film camera, but it also has the additional task of directing the light towards the sensor instead of onto film.

3. What is the difference between optical and digital zoom?

Optical zoom refers to physically adjusting the camera lens to zoom in on a subject, while digital zoom involves digitally enlarging a portion of the image. Optical zoom results in higher quality images, whereas digital zoom can lead to pixelation and loss of detail.

4. How does a digital camera store images?

Digital cameras store images in the form of digital data on a memory card. This data is made up of millions of pixels, each with a specific color and brightness value. When the camera is connected to a computer, the data can be transferred and saved as image files.

5. What is the difference between a DSLR and a point-and-shoot camera?

A DSLR (Digital Single-Lens Reflex) camera allows the user to change lenses and has a larger sensor, which results in higher quality images. Point-and-shoot cameras have a fixed lens and smaller sensor, making them more compact and easier to use, but with lower image quality compared to DSLRs.

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