Insight - How WebCam works

Webcam is a device used to capture images, audio and videos. Webcam are either inbuilt or can be externally attached with the laptop or the computer. The most common application of a webcam is video chat, video recording, image capturing. A webcam generally consist of a lens, an image and sound sensors, electronic circuitry to process the data and send it to PC. A variety of webcams with different features are available in the markets. Depending on the features and quality, the technologies used and the prices vary. However the basic function remains the same.

Fig. 1: Image of Laptop Webcam

The webcam attached on the laptop is shown in the image above. You can see an optical lens to capture the images/videos and a small hole to capture sound. The bottom part of the body consists of a plastic casing which provides support to the webcam and a mechanism to fix the webcam on the top of the laptop.

Neck

Fig. 2: Rotating Neck of Webcam

The neck of this webcam can rotate along the horizontal and vertical axis up to certain angles. The rotation is restricted by means of mechanical stoppages which will be shown later in the article.

Mechanical Hooks

Fig. 3: Image Indicating Hooks that Bind Together Front and Back of Webcam

The front and back face of the plastic casing are fixed to each other by means of four mechanical hooks. Two of them are visible in the image above and the other two are just opposite to them.

Bottom Assembly

Fig. 4: Inside View of Plastic Casing

The plastic casing from inside is shown in the image above.

Fig. 5: Spring-Loaded Screw Mechanism of Laptop

In order to fix the webcam on the laptop a spring loaded screw mechanism is used. The front face of the bottom part can be pulled to fix on the laptop. A spring force keep it fixed.

Neck Movement Mechanism

Fig. 6: Image Indicating Mechanics of Neck Movement of Webcam

Fig. 7: Plastic Casing with Slot for Rubber Rings

The mechanical structure of the neck of the webcam is responsible for its motion along the horizontal and vertical axis. The two rubber rings at the end of the cylindrical rod have a special shape to provide the rotational movement. The casing has a special slot for the rubber rings.

Top Half Internal Structure

Fig. 8: Electronic Circuitry at Top of Webcam

The top part of the webcam contains all the electronic circuitry required to do its job. It is guarded by a pair of plastic casing which are fixed to each other by means of mechanical hooks.

PCB-Back View

Fig. 9: PCB and Wire Connections

The PCB which contains all the electronic components embedded in it is shown in the image above.

PCB-Front View

Fig. 10: PCB Configuration

The other side of the PCB showing the major components: lens, CMOS sensor, microphone, semiconductor chips etc.

Microphone

Fig. 11: Microphone and PCB Setting

The microphone also called the sound sensor is used to capture the sound signals and convert them into electrical signals for further processing by the processor. An electret condenser microphone is used for this purpose. Refer to the working of electret condenser microphone for details.

CMOS Sensor

Fig. 12: CMOS Image Sensor of Laptop Webcam

The image/video sensor, which is the most important part of the webcam, is shown in the image above. The sensor used here is a CMOS Image sensor. The purpose of the image sensor is to convert the optical light signals into electrical signals. A CMOS sensor is made up of an array of photo detector with amplifiers, noise- correction and digitization circuit. It uses the CMOS technology for its manufacturing. The output of the CMOS sensor is digitalized signals.

Electronic Components

Fig. 13: ICs and Electronic Circuitry of PCB

The rest of the electronic components in the circuitry are shown in the image above. Two major semiconductor IC can be seen. 24C02 is a serial EEPROM memory manufactured by Atmel used to store the data. The data stored in this memory is not lost even when the power is turned off. VC0326 IC manufacture by Vimicro is a chip with many functions embedded in it. It has an 8- bit microcontroller, 10 bit imaging processor, JPEG encoder engine, inbuilt ADC, audio and video class USB support and complies with USB 2.0 protocols for transferring data to the PC. It collects the data from the image and the sound sensor, processes it and sends it to the PC using the USB.

Lens Housing

Fig. 14: Lens of Webcam and its Housing Pattern

The lens is placed in a separate plastic housing which is screwed to the front plastic casing of the webcam. The housing ensures mechanical stability and protection from external damages.

Lens

Fig. 15: Close-up View of Lens

The lens of the webcam is generally made up of plastic and has a fixed focal length. The focal length and aperture size define the quality of the lens. A lens is used to focus the image of objects on the CMOS sensor.