How Do Scanners Work

Representing one of the essential parts of any modern-day office or a personal computer periphery collection of a person working from home, so to speak, scanners are absolute must-have devices if you work with any documents daily.

Let’s say you work from home during the Covid times, and you need to send your boss your ID and some other information from your driver’s license, but he needs to have a copy of the original thing.

You can try taking a picture of it using your iPhone or a camera, but that may come out looking messy since you need to take care of the lighting and make sure you take the picture at the right angle, and so on.

In this article, we will talk about how do scanners work and how these contraptions can do the magic that they’re doing to give the perfect copies of whatever we place underneath their lids.

Here’s the deal.

How Do Scanners Work

On the other hand, if you use a scanner, all you need to worry about is aligning the document on the glass so that it’s not askew (which is fairly easy to do) and then closing the lid so that the only light this document is exposed to is the light provided by the scanner itself, so to speak.

The thing is, whatever real-life document that doesn’t exist or that cannot be easily replicated online you need to take a picture of somehow and present it as a digital file, scanners can do a good job of photographing under perfect conditions and then turning into an easy-to-open digital file.

Also, we’re going to briefly list the different kinds of scanners that exist out there.

As you will see, although scanners look like pretty simple contraptions, they do use some pretty advanced technology and have some rather interesting moving mechanisms ‘underneath the hood.’

Most Common Types of Scanners

3 types of printer

1. Handheld Scanners

As their name suggests, handheld scanners are a special breed of scanner that you can hold in your hand and use it scan the documents and other items you go over.

One of the great examples of these contraptions being used would be convenience stores and other establishments that sell stuff, so to speak.

Handheld scanners are used by cashiers to scan the barcode of the product you’re buying so that they don’t need to type the price in manually.

Typically, handheld scanners are significantly smaller than their flatbed counterparts, which means they are less expensive. On the other hand, the problem with them is that they don’t tend to be that precise when it comes to the quality of the scan.

2. Flatbed scanners

Flatbed scanners represent one of the most commonly used types of scanners out there.

This scanner is usually placed on a desk or some other flat surface; it looks flat (as its name suggests), and it comes with a lid you can open and close to protect the document from the outside light.

When it comes to the use of these scanners, they are often used in offices where there are a lot of documents that need to be scanned, as well as in schools, home offices, governmental institutions, and any place where documents need to be ‘translated’ from a real-life format into a digital format, so to speak.

3. Sheet-fed scanners

In the introduction to this article, we mentioned that some scanner models feature moving parts that are used to scan the images and photograph them along the way.

Well, this type of scanner doesn’t fall into this category.

Sheet-fed scanners operate similarly to printers. The way they work is that you set the paper you want to scan in the tray (Similar to how you place clean sheets of paper in a printer tray.), and then a small motor will roll this piece of paper and move it further so that it can be scanned.

4. Drum scanners

Representing by far the most complex and the most expensive scanners, drum scanners are typically used by newspaper agencies and other establishments that require high-quality the scanned images.

These contraptions are called ‘drum’ scanners because they use special photomultiplier tubes that sort of look like drums. Also, the document that needs to be scanned goes around this drum in a similar way it’s taken in and out of a sheet-fed scanner.

The difference, of course, is that with sheet-fed scanners, the document doesn’t go a full circle, while the accuracy requirements of a drum scanner mean that the document that’s placed inside it needs to complete a full circle, so to speak, to be scanned thoroughly.

Parts of a Flatbed Scanner

Since in this article, we’re going to focus on explaining how flatbed scanners work, we’d like to say that this type of scanner is the most commonly found in both offices and home offices, or study rooms, hence – it makes the most sense to explain to you how the technology behind these contraptions works.

So, in this section, we’re going to highlight some of the most important parts of these flatbed scanners. Since scanners consist of many smaller parts, we will not describe each of them in great detail. Instead, we will focus on the most important ones and then mention the smaller ones in a paragraph or two.

Here are the most important parts:

1. CCD array (Charged-Couple Device) –

CCD represents the most important part of a common flatbed scanner. What this array consists of is a great number of small photo-sensitive diodes called photosites.

The way these diodes work is that they are sensitive to light. (As their name suggests.)

When these diodes are exposed to light, they create a small electrical charge.

Now, the more intense the light that hits them, the bigger charge they will create.

2. Mirrors

Scanners are similar to printers in the sense that they both have a certain number of mirrors that are responsible for reflecting light within the contraption itself.

Since scanners get electrical signals produced by the photosites we mentioned above, the mirrors serve the purpose of directing the light during the scanning process so that it hits exactly the diode that it needs to, thus creating the replica of the document you’re scanning.

3. Glass plate

If you’ve ever used a flatbed scanner, you’ve certainly seen a large surface underneath the lid made out of a special sort of glass.

This glass needs to be completely see-through, and there must be no dirt or other impurities on it. If the glass isn’t clean, or it’s been damaged or cracked, the quality of the scan will suffer because the light cannot reflect well through it, thus making the scan look blurry and incomplete. 

Some of the other components of a scanners work include the lamp that provides the light (which is then manipulated by the mirrors we mentioned above), various filters used for further improving the quality of the lighting signal, so to speak, as well as other supporting parts such as the control circuits, belts, stepper motor, the power supply, as well as the lid that you open and close to place the document.

How does a scanning process work?

provides paper on the printer

While the way scanners work in terms of the technology involved may seem a tad complex, operating a scanner is one of the easiest things to do around the office, so to speak. (Or, wherever you’re using a scanner.)

To explain the process below, we’re also using the flatbed scanner example. (That said, other types of the scanner also use pretty much the same, or at least similar, technology.)

Here’s a step-by-step explanation of how to make a scanner do its magic:

1. Placing the document

… on the glass plate, we already talked about in one of the passages above.

To reiterate, the glass surface needs to be completely clean; otherwise, the quality of the scan will be compromised.

The way you place the document is you take the side of the page that you want to print and then place it face-down. (So, if you have a sheet of paper with a text you want to scan on one side, and the other side is blank when you place the document correctly, you will be able to see the blank side facing toward you.)

Once you’ve done that, you must close the lid first, and then you can start scanning.

2. The lamp illuminates the document

Every scanner needs to have some sort of light source that will illuminate the document you’re scanning so that the light-sensitive diodes can make the electrical signal to send to the computer.

Flatbed scanners also come with a special lamp used for this purpose.

Once the document is placed correctly, and the lid is closed, and you hit the Start Scan button on your computer, this lamp will start illuminating the paper, thus starting the scanning process. 

3. The scan head moves

If you’re wondering what on Earth a ‘scan head’ is, it represents a part of a printer that contains all the components necessary for proper reception of the light signal by the diodes we mentioned above.

So, a scan head contains different mirrors, lenses, and the CCD array, making the whole light-to-electricity conversion possible. Some filters serve the function of ‘straightening the signal’ once it’s created by the diodes.

What happens when you hit Scan, and the lamp starts shining its light is that the belt starts moving the scan head (that’s underneath the glass, by the way) so that it can cover the entire document.

(This is what produces that well-known scanning sound when a document is scanned. Also, if you look sideways, on some scanner models, you can see the scan head slowly moving from one side of the scanner to the other.

4. Angled mirror reflection

Since the scanner head typically doesn’t cover the entire width of the see-through glass, mirrors need to be introduced, so that the entire image can be scanned.

Usually, flatbed scanners use two mirrors for this purpose, although it’s not uncommon to see a flatbed scanner that uses three mirrors. These mirrors are curved so that the edges of the document can be reflected toward the center where the scan head passes.

5. The images are reflected onto a lens

When it comes to how scanners create color scans of whatever document you place on the glass, the deal is fairly straightforward.

The number of passes the scan head makes during the scanning process is typically two.

However, to illustrate how color scanning works, it may be easier to take a look at a three-pass scanner. This scan head passes three times back and forth to scan the entire document. With each pass, the scan head ‘concentrates’ on a particular color.

Since we know that there are three main colors computers typically use (as well as computer peripheries such as scanners and printers, for example), we can see why it takes three passes to assemble a complete colored scan of a document on the glass. (The three colors are red, green, and blue, by the way.)

Once this process is completed, the computer takes all the information the scan head gathered (with the CCD sending electrical signals of varying strength). It creates a digital rendition of the document you just scanned.

Final Verdict

All in all, whether you use them for work, or a school-related or some other personal project, having a scanner you can use whenever you want or need to can be a great way to easily ‘translate’ real-life documents into faithful digital copies that can then easily be sent and archived on your computer or a cloud.

Understanding how scanners work enables us to perform better maintenance on them and use them in optimal conditions.

We hope you found how do scanners work in this article helpful, and we wish you plenty of success with your scanning ventures.

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