Talk:Image sensor

From Wikipedia, the free encyclopedia

	Film Portal This article is within the scope of WikiProject Films. This project is a central gathering of editors working to build comprehensive and detailed articles for film topics on Wikipedia. If you would like to participate, you can edit the article attached to this page, or visit the project page, where you can join the project and/or contribute to the discussion.
Start This article has been rated as Start-Class on the quality scale. ??? This article has not yet received a rating on the priority scale.
Editing Guidelines Please remember these guidelines when editing a film article: If a non-film article already exists with the name of the film that you are trying to create an article for, disambiguate and use (film) in the title: Film Title (film) For more information see: Wikipedia:Naming conventions (films) When writing an article about a particular film, the general format should be a concise lead section, followed by a plot summary of no more than 900 words, production details, a cast list, a reception section, and references. Create an Infobox that tells all pertinent information about the film.
Additional Information: This article has been checked against the following criteria for B-Class status: Referencing and citation: not checked Coverage and accuracy: not checked Structure: not checked Grammar: not checked Supporting materials: not checked To fill out this checklist, please add the following to the template call: <!-- 1. It is suitably referenced, and all major points are appropriately cited. --> |B-Class-1=yes/no <!-- 2. It reasonably covers the topic, and does not contain major omissions or inaccuracies. --> |B-Class-2=yes/no <!-- 3. It has a defined structure, including a lead section and one or more sections of content. --> |B-Class-3=yes/no <!-- 4. It is free from major grammatical errors. --> |B-Class-4=yes/no <!-- 5. It contains appropriate supporting materials, such as an infobox, images, or diagrams. --> |B-Class-5=yes/no Related task forces (general): Filmmaking task force

[edit] CCD vs CMOS

The distinction between CCD and CMOS and the divergence of these technologies has occurred for a number of reasons. This article could be greatly enhanced if a comparison between the two are compared. Is there anyone who would like to provide a detailed comparison? PD 11:17, 7 July 2007 (UTC)

This part is confusing: "Extra circuitry next to each photo sensor converts the light energy to a voltage." A CMOS sensor requires no "extra" circuitry compared to a CCD sensor to convert light to voltage, since this is a task performed by the photodiode, which is basically common to both technologies. The extra per-pixel circuitry in CMOS sensors generally performs other tasks, such as amplification.

You're right, it's not very clear or correct. Both CMOS and CCD collect charge on the photodiode and there's an associated voltage; but in the CMOS sensors, that charge is read out as a voltage via an emitter-follower amplifier transistor, while in CCD the charge itself is shifted out. I recommend you look for a book that compares them and try to find some more accurate terminology to put instead. here is a place to start. Dicklyon 17:25, 3 September 2007 (UTC)

This is incidentally a major source of difference between CCD and CMOS sensors which isn't addressed in the article. The main disadvantage of a CMOS sensor is that they have less space reserved for the photodiodes (the fill factor), due to this extra circuitry. This is largely mitigated today by the use of microlenses, giving both CCD and CMOS sensors similar fill factors. A major advantage of CMOS is that the per-pixel circuitry also allows for per-pixel noise suppression, since the amplifiers are close to the photodiodes. This means CMOS sensors can have better performance in terms of noise, and have been replacing CCDs at both the low (cheaper fabrication) and high (better circuitry) end of digital camera lines. The article citing similar performance dates from 2001, and has been superceded by new technology. --69.227.70.158 16:28, 3 September 2007 (UTC)

It's not clear what you mean here by per-pixel noise reduction. Noise and noise reduction have actually been big problems in CMOS, solved not by the amplifier but by going to CCD-like fully-depleted pinned photodiodes, and/or CDS amplifiers in the column circuits. Dicklyon 17:25, 3 September 2007 (UTC)