Modern webcams. Important webcam settings

It consists primarily of a sensor.
Very often, cheaper CMOS sensors are used instead of standard CCD matrices for video surveillance. Although they have more low sensitivity and not too good color reproduction, their use can greatly reduce the cost of the device, since these sensors are " all in one chip» with digital data output.
Next: The network camera includes microprocessor for video compression and motion detection(or just a compressor chip). The most popular is JPEG, as the simplest and cheapest; MPEG4 is also used quite often, the rarest and most expensive being MPEG2. With the expiration of the patent for arithmetic coding, WaveLet gains popularity. Finally, the network camera includes a 10/100 Mbps network controller.

The device and principle of operation of the web-camera:
The modern webcam is digital device which produces video filming, digitization, compression and transmission over computer network video images. Therefore, the webcam includes the following components:
- CCD
- lens
- optical filter
- video capture card
- block of compression (compression) of the video image
- CPU and built-in web server
- RAM
- flash memory
- network interface
- serial ports
- alarm inputs/outputs
A CCD matrix is ​​used as a photodetector in most web cameras (CCD, CCD - a device with charge bond) - a rectangular light-sensitive semiconductor plate with an aspect ratio of 3: 4, which converts the light falling on it into an electrical signal. The CCD matrix consists of a large number of photosensitive cells. In order to increase the light sensitivity of a CCD array, it is not uncommon to form a structure that creates a microlens in front of each of the cells. IN technical parameters webcams usually indicate the format of the CCD (the length of the diagonal of the matrix in inches), the number of effective pixels, the type of scanning (progressive or interlaced), and sensitivity. A typical webcam contains a lens, an optical filter, a CCD, a circuit digital processing image, an image compression scheme, and web server to connect to the network. Each network camera has its own IP address, computing functions, and firmware, allowing it to function as a web server, FTP server, FTP client, and e-mail client. Most advanced network cameras include many other attractive features such as motion detection, alarm input/output and email support.

You can also see information on the topic:

A modern webcam is a digital device that captures video, converts an analog video signal into a digital one, compresses a digital video signal, and transmits a video image over a computer network. Therefore, the webcam includes the following components:

• CCD,
• lens,
• optical filter,
• video capture card
• block of compression (compression) of the video image,
• CPU and embedded web server,
• flash Memory,
• network Interface,
• serial ports,
• alarm inputs/outputs.

As a photodetector in most webcams, CCD (CCD, CCD - charge-coupled device) - a rectangular light-sensitive semiconductor plate with an aspect ratio of 3: 4, which converts the light incident on it into an electrical signal. The CCD matrix consists of a large number of photosensitive cells. In order to increase the light sensitivity of a CCD array, it is not uncommon to form a structure that creates a microlens in front of each of the cells. The technical parameters of a webcam usually indicate the format of the CCD matrix (the diagonal length of the matrix in inches), the number of effective pixels, the type of scanning (progressive or interlaced), and sensitivity.

Lens is a lens system designed to project an image of an object of observation onto photosensitive element webcams. The lens is an integral part of the webcam, so the quality of the video image received by the webcam depends on the correct choice and installation of the lens. Quite often, a webcam is equipped with a lens. Lenses are characterized by a number of important parameters, such as focal length, relative aperture (F), depth of field, mount type (C, CS), format.

Optical infrared cut filters, which are installed in webcams, are optically accurate plane-parallel plates mounted on top of a CCD matrix. They work like optical low pass filters with a cutoff frequency of about 700 nm, near red. They cut off the infrared component of light waves, providing the webcam with the correct color reproduction. However, many black and white webcams do not have these filters installed, which is why monochrome webcams have higher sensitivity.

Video capture card webcam (digitizing unit) converts analog electrical signal, formed by a CCD matrix, into a digital format. The signal conversion process consists of three stages:

• Sampling,
• quantization,
• Coding.

Sampling- reading the amplitude of the electrical signal at regular intervals (period). This stage of signal conversion is characterized by the sampling frequency.

Quantization is the process of presenting discretization results in digital form. The change in the level of the electrical signal over the sampling period is represented as a code word of 8, 10 or 12 bits, which give respectively 256, 1024 and 4096 quantization levels. The number of quantization levels determines the accuracy of the signal representation in digital form.

Coding. In addition to the information about the change in the signal level obtained at the previous stage, during the encoding process, bits are formed that indicate the end of the clock pulse and the beginning of a new frame, as well as additional error protection bits.

Compression block The webcam compresses the digitized video signal into one of the compression formats (JPEG, MJPEG, MPEG-1/2/4, Wavelet). Compression reduces the video frame size. This is necessary for storing and transmitting video over the network.

CPU is the computing core of the webcam. It performs operations for outputting digitized and compressed video images, and is also responsible for performing the functions of the embedded web server and control program for webcams.

Interface for Ethernet used to connect the webcam to a 10/100 Mbps Ethernet network.

For network operation, the webcam may have serial port to connect a modem and work in dial-up mode in the absence of local network. You can also connect peripherals to the webcam through the serial port.

Flash memory card allows you to update webcam control programs and store custom HTML pages.

RAM serves to store temporary data that is generated during the execution of control programs and user scripts. Many Internet cameras have a so-called video buffer. This is a portion of RAM reserved for recording and temporarily storing video frames captured by the webcam.

Alarm inputs/outputs are used to connect alarm sensors to the webcam. When one of the sensors is triggered, an alarm signal is generated, as a result of which the webcam processor composes a set of frames recorded in the video buffer before, after, and at the time of the alarm. This set of frames can be sent to a given e-mail address or via FTP.

A webcam is a device that is most often bought at the same time as a computer and does not attach much importance to it. However, it is worth paying attention to the characteristics, otherwise, already at the first shooting or communication session, disappointment and irritation may appear.

Following our tips, you can learn all about the features, functions and applications of webcams. We hope that this information will help readers to make right choice when purchasing a device.

1. What is a webcam, how does it work and where is it used

Webcam is enough small device, which is a photo or video camera connected to a computer or laptop. Webcams capture an image in real time and then transmit it to the addressee using the Internet. The difference from a digital camera primarily lies in the power supply by wires and the impossibility of functioning without a computer, in any case, fully.

Webcams are used for video chats and video calls, video conferences, security purposes, for monitoring and surveillance, etc.

1. Key features of webcams

The characteristics of webcams affect both the quality of the device and its price, which can vary greatly from model to model. What are the main parameters and what should not be missed when choosing a webcam?

• Webcam matrix type. The webcam matrix can be created using one of the following technologies:

a) CCD- a technology used in digital cameras and also used for webcams. Among its advantages: high sensitivity, high duty cycle, efficiency - about 95%, lower noise level during operation. It is worth remembering that a too weak power supply is likely to fail at the time of maximum load of the system or even its individual elements. Power supply too high power can reduce the efficiency of the entire computer;

b) CMOS is a cheaper-to-manufacture technology used in most webcams. Such matrices have a low cost, shoot up to 500 frames per second, and consume quite a bit of energy during operation. Among their shortcomings, experts point out a large number of image noise, low pixel fill factor and, as a result, low sensitivity;

c) BSI CMOS- when using such a matrix, the light hitting the photodiodes is simplified. Such sensors are also called "back-illuminated sensors" - they are much more light sensitive. Due to this, the amount of noise in the image is reduced compared to conventional CMOS.

• Camera resolution- another one of the most important characteristics. The quality of the transmitted image depends on it. Note that resolution can be direct or interpolated. In software interpolation, the number of pixels in the original image is processed using mathematical methods, is multiplied by a certain number and then an already enlarged image is formed. This does not change the original resolution of the image, and the quality may deteriorate. When choosing a camera, you should pay attention to the real resolution of 1.3 megapixels - this is enough for HD quality.
• Frame frequency- a characteristic responsible for the smoothness of shooting. Acceptable is the rate of shooting from 15 frames per second - this will be enough for communication on the Web. For high-quality video broadcasts, at least 30 frames per second is required.
• Focusing webcam allows you to influence the clarity of the image. It can be either manual or automatic. Manual is carried out by rotating the wheel located at the lens. Autofocus, on the other hand, assumes that the webcam itself sets the distance to the object and calculates the focal length. IN different models autofocus speed and quality can vary significantly.
• Sensitivity- the parameter of the minimum allowable illumination at which it is possible to use the camera. However, when buying a camera with infrared illumination, this characteristic will immediately be presented at a decent level.
• Connection type. Typically, webcams are connected via USB version 1.1, 2.0, or 3.0. The latter type is faster, but only found on modern computers.

1. Additional webcam features:

• The presence of a built-in microphone. Eliminates the need to purchase another device, allows you to make video calls to large companies. Now almost all cameras are equipped with a built-in microphone.
• The ability to use the webcam as a camera. Modern models webcams allow you to use these devices as digital cameras. If you choose a camera for these purposes, pay attention to devices with a higher resolution, otherwise the quality of the photos is unlikely to suit you. Some cameras are also equipped with a photo button on the body - pressing it can activate photo mode and launch a graphics editor.
• Availability of special software. Each webcam manufacturer offers its own software for users to install or use. Apart from standard features, it can complement the work of the camera with personalized features. For example, Logitech offers a built-in graphics editor.

1. What else should you pay attention to?

When choosing and buying a webcam, pay attention to its mounting, tilt and swivel capabilities, as well as the viewing angle.

Explore the specifications, compare webcam models, take into account the tips from our review and enjoy a comfortable and enjoyable video chat.

A webcam is a device that brings people together, which allows you not to feel how far your close and dear person is.

Many now do not even imagine how they lived before without this invention, how they communicated with friends and relatives who live thousands of kilometers away. But thanks to the webcam, all boundaries were erased and now at any time of the day you can see a person and chat with him.

In addition to the fact that the webcam makes it possible to communicate with relatives who live abroad or with friends who live in other cities, it has become an integral part of the workflow in institutions and offices. The presence of a webcam at the desktop makes it possible to monitor the work of employees, hold online conferences or meetings with employees who work outside the central office.

Everyone knows how to communicate via Skype, but, unfortunately, not many users can choose a good webcam. But the quality of the image and other important points that make communication between people comfortable depend on the camera.

As such, there is no classification or types of webcams. All cameras can be conditionally divided into computer, tablet, IP-cameras, wireless and gaming. But in reality, they are distinguished by such parameters as the resolution of the matrix, the quality of the optics, the type of attachment, the method of transmitting information. According to the same parameters, the necessary webcam is selected.

It should be noted that IP cameras are mainly used to monitor an object or territory. Such cameras transmit high-quality images at any time of the day, unlike their counterparts, which do not have any criteria regarding image quality. Therefore, when choosing a webcam, you should not rely on the described characteristics. You just need to turn on the camera and see how it works. In this case, do not be afraid that the program will not work. Manufacturers create webcams that go with any application.

Main characteristics

Choosing a webcam is worth starting with studying matrix type. There are two main types of CMOS and CCD. Webcams that are designed to communicate on the Internet are equipped with a CMOS type matrix. The CCD matrix has the best quality image transmission than the first type. Therefore, it is installed in webcams that are designed for security purposes. The best thing to do when choosing a camera is to compare image quality with a CMOS and CCD sensor. Then make a purchase.

Resolutions- one more important point, which affects the image quality. The minimum webcam resolution is 0.3 megapixels, i.e. 320x240 pixels, which will be enough for videoconferencing. The maximum webcam resolution is 2592x1944 pixels. The optimal resolution for webcams is 640x480 and 1280x960 pixels, which allows you to clearly see the interlocutor, take pictures and videos. At the same time, you should not hope that the video or photo will be clear, like on a camera or camcorder. Still, the pictures are slightly blurry. A webcam is, first of all, a tool for communicating with people. Therefore, the low resolution is compensated by other good parameters.

optician a, installed on webcams affects the quality of the picture. Manufacturers are trying to install high-quality optics. It can go in both expensive and budget models. High-quality glass optics, for example, include Carl Zeiss. The type of optics is indicated in the characteristics of the device in the store or on the packaging.

Frame frequency- a parameter to which you should be careful. The frame rate ranges from 9 to 90Hz. A small frequency will transmit the image as a slideshow. A high frame rate may not be compatible with the speed of the Internet, and as a result, communication will not be possible. The best option is 40 - 70Hz. But still, you should take into account the speed of the Internet, for example, for Wi-Fi, you should choose an average frame rate.

The next parameter that affects image quality is matrix sensitivity. The quality of the image in a particular illumination depends on the level of sensitivity of the matrix. If the sensitivity of the matrix is ​​​​not high, then poor lighting will interfere with the transmission of the picture.

Communication without a microphone is difficult to imagine. Therefore, if the webcam is selected for personal computer, then its model must have a microphone. If for a laptop, netbook or tablet, then the microphone is already built into them.

Mount type. For this parameter, everything is quite simple. If you need to mount to the monitor, then select the model with the appropriate fasteners. The webcam can just stand on the table if there is a lot of space. To perform security functions, cameras are chosen that are mounted on a wall or a pole (if the surveillance is carried out on the street). Therefore, everyone chooses what is more convenient for him.

There are two ways to connect a webcam - via a USB cable or a modem. Basically, they use the first connection method, because the speed will always be high. If you use a modem, then the speed will depend directly on the provider. The third connection method is less common because it is used in expensive webcam models - wireless. It can only be used if Wi-Fi is available.

The last thing you should pay attention to when choosing a webcam, compatibility with operating system. Here it is worth saying one thing, almost all models of webcams work with an operating Windows system and not suitable for other systems.

Additional webcam features

Zoom and backlight. For a camera or camcorder, these functions would be much more important than for a webcam. They still will not improve the image quality to such a state as in the camera. At the same time, the presence of zoom and backlight indicates a good assembly of the device.

Autofocus is a good thing, especially if you plan to frequently transfer your webcam or take photos and videos. In this case, the distance to the subject will always be adjusted.

Many manufacturers add a change in shooting mode (for example, sepia, black and white photo, white balance, etc.) to the additional features of the webcam. In principle, they will be useful for filming, but not for skype communication. Although it is worth processing photos in a program specially designed for this.

Webcam manufacturers

Responding to this question the first thing that comes to mind is well-known companies that produce electronics, i.e. Samsung, LG and Philips. In addition, webcams are produced by HP, Bravis and Microsoft. Of course, there are other manufacturers less popular than those listed. The most popular are webcams from Genius, Logitech and Creative. They provide high quality of their product.

You can buy goods from these companies not only in specialized stores, but also in online stores, where quality is also guaranteed.

The pricing policy is different. It depends not only on the brand, but also on additional features. When choosing a webcam, it is worth remembering one thing - the most expensive does not mean the best. You can buy an inexpensive webcam and get a high-quality image when communicating with relatives. The cost of webcams varies from 300 to 6100 rubles.

Using the webcam is quite simple. Special programs allow you to set up Skype, and the camera will only need to be connected to it

When using the webcam, it is important not to touch the optics and to fix it securely so that it does not fall.

Thus, the best option for home use and Skype communication will be a webcam with a resolution of 640x480 pixels, a USB cable for connection, with a built-in microphone and with the function auto tuning images based on the lighting in the room.

webcams. Purpose, principle of operation and main characteristics.

discipline (specialization) "Hardware computer science»

Checked

Nikolskaya K.Yu.

student group PS-170

Badalova A.A.

Abstract protected

with an estimate

Chelyabinsk 2014

Badalova A.A. webcams. Purpose, principle of operation and main characteristics. - Chelyabinsk: SUSU, PS-170, 20 p., 4 ill., bibliogr. list - 5 name.

The purpose of the abstract is to learn about the purpose, principles of operation and the main characteristics of webcams.

The objectives of the abstract are to study the device and the principle of operation of webcams, learn how to install webcams and connect them to the network, learn about the importance of webcams in the modern world.

The main characteristics of webcams, ways to connect to the network are considered. Learn about webcam software and how to connect your webcam to a network.

1. Introduction (page 4)

2. Definition (page 5)

3. The history of the webcam (p. 6)

4. Design and operation of the webcam (p. 7-11)

5. Additional features and functions of webcams (p.12)

6. Connecting the webcam to the network (p. 13-15)

7. Ways to use webcams (p. 16-17)

8. Webcam software (p. 18)

9. Conclusion (page 19)

10. Bibliographic list (p. 20).

Introduction.

Webcams are becoming more and more part of our lives. They are used to build video systems for both territorially large and small objects. Especially they become indispensable in the control and monitoring of remote points where there is a need to use unattended equipment. When you urgently need to install "temporary" cameras, webcams are indispensable, because they do not require the installation of separate wires, and therefore installation is quick and easy.

The purpose of my work is to learn about the purpose, principles of operation and the main characteristics of webcams.

To do this, I will study the history of occurrence, the device and the main characteristics, as well as the scope of webcams, learn how to install and connect them to the network.

Webcam concept.

A digital webcam is a network device that consists of a video camera (CCD), a compression processor, and an embedded web server. As a rule, a webcam is used as a device for organizing video shooting, video conferencing or video surveillance and transmitting video images over a LAN/WAN/Internet network. Webcam operation on the network does not require special devices and a personal computer. Depending on the settings, access to the video image received by the webcam may be open to all network users or only authorized users.

The history of the webcam.

It all started in one of the computer laboratories in Cambridge back in the early 90s of the last century, when the Global Web was just beginning its victorious march across the planet. A group of scientists, 15-20 people, worked on a project in the field network technologies. Working conditions were spartan - the whole team had only one coffee maker, which could not satisfy the needs of the entire team. The main work was carried out in the laboratory, the staff lived in the same building, but in a different part of it. In order to whip up the thought process with a cup of an invigorating drink, the participants in the scientific project were forced to frequent the corridor located on the floor above, where the coffee maker was located. Often such trips failed, as some colleagues had already managed to empty the coveted container. The situation required a non-standard solution, and it was found.
One of the computers in the lab had a video surveillance device (frame grabber). A camera was connected to it, which was directed at the object of observation. The same computer played the role of a web server due to a specially written software. Those who wanted to know if there was coffee had to run client software on their computer that connected to the server. As a result, on remote computer a small window displayed a black-and-white image, updated three times a minute. A note about this interesting complex was published in Comm-Week magazine on January 27, 1992. Not much time has passed since the appearance of the first prototypes of IP cameras, but they have already turned into a fully formed, separate class of devices that make everyday life easier, more convenient and more fun.

Figure 1. Snapshot from the first webcam

The device and principle of operation of the webcam.

A modern webcam is a digital device that captures video, converts analog video to digital, compresses digital video, and transmits video over a computer network. Therefore, the webcam includes the following components:

CCD,

lens,

optical filter,

video capture card

block of compression (compression) of the video image,

CPU and embedded web server,

flash Memory,

network Interface,

serial ports,

alarm inputs/outputs.

·
As a photodetector in most webcams, CCD ( CCD, CCD - charge-coupled device) - a rectangular light-sensitive semiconductor plate with an aspect ratio of 3: 4, which converts the light incident on it into an electrical signal. The CCD matrix consists of a large number of photosensitive cells. In order to increase the light sensitivity of a CCD array, it is not uncommon to form a structure that creates a microlens in front of each of the cells. The technical parameters of a webcam usually indicate the format of the CCD matrix (the diagonal length of the matrix in inches), the number of effective pixels, the type of scanning (progressive or interlaced), and sensitivity.

· Lens - this is a lens system designed to project the image of the object of observation onto the photosensitive element of the webcam. The lens is an integral part of the webcam, so the quality of the video image received by the webcam depends on the correct choice and installation of the lens. Quite often, a webcam is equipped with a lens. Lenses are characterized by a number of important parameters, such as focal length, relative aperture (F), depth of field, mount type (C, CS), format.

· Optical infrared cut filters , which are installed in webcams, are optically accurate plane-parallel plates mounted on top of a CCD matrix. They work as optical low-pass filters with a cutoff frequency of about 700 nm, near red. They cut off the infrared component of light waves, providing the webcam with the correct color reproduction. However, many black and white webcams do not have these filters installed, which is why monochrome webcams have higher sensitivity.

· Video capture card webcam (digitization unit) converts the analog electrical signal generated by the CCD matrix into digital format. The signal conversion process consists of three stages:

Discretization, quantization, coding.

Sampling- reading the amplitude of the electrical signal at regular intervals (period). This stage of signal conversion is characterized by the sampling frequency.

Quantization is the process of presenting discretization results in digital form. The change in the level of the electrical signal over the sampling period is represented as a code word of 8, 10 or 12 bits, which give respectively 256, 1024 and 4096 quantization levels. The number of quantization levels determines the accuracy of the signal representation in digital form.

Coding. In addition to the information about the change in the signal level obtained at the previous stage, during the encoding process, bits are formed that indicate the end of the clock pulse and the beginning of a new frame, as well as additional error protection bits.

· Compression block The webcam compresses the digitized video signal into one of the compression formats (JPEG, MJPEG, MPEG-1/2/4, Wavelet). Compression reduces the video frame size. This is necessary for storing and transmitting video over the network. If the local network to which the webcam is connected has limited bandwidth, it is advisable to reduce the amount of transmitted information by lowering either the network frame rate or the frame resolution. Most of the compression formats that webcams use provide a reasonable compromise between these two ways of solving the problem of transmitting video over a network.

Compression formats known today make it possible to obtain a digitized stream with a bandwidth of 64 Kb - 2 Mb (with such a bandwidth, video data streams can work in parallel with other data streams in networks).

· CPU is the computing core of the webcam. It performs operations for the output of digitized and compressed video images, and is also responsible for performing the functions of an embedded web server and a control program for web cameras.

· Interface for Ethernet used to connect the webcam to a 10/100 Mbps Ethernet network.

· For network operation, the webcam may have serial port to connect a modem and work in dial-up mode in the absence of a local network. You can also connect peripherals to the webcam through the serial port.

· Flash memory card allows you to update webcam control programs and store custom HTML pages.

· RAM serves to store temporary data that is generated during the execution of control programs and user scripts. Many Internet cameras have a so-called video buffer. This is a portion of RAM reserved for recording and temporarily storing video frames captured by the webcam. Information in the video buffer is updated cyclically; the new frame is written instead of the oldest one. This feature is required if the webcam is performing CCTV surveillance, as it allows you to restore the pre- and post-alarm events from security sensors connected to the webcam.

· Alarm inputs/outputs are used to connect alarm sensors to the webcam. When one of the sensors is triggered, an alarm signal is generated, as a result of which the webcam processor composes a set of frames recorded in the video buffer before, after, and at the time of the alarm. This set of frames can be sent to a given e-mail address or via FTP.

Figure 2. Webcam device.

5. Additional features and functions of the webcam

· Motion Detector - this is a software module, the main task of which is to detect webcams moving in the field of view at a video surveillance object. The motion detector not only detects movement in the image field, but also determines the dimensions of the object and the speed of its movement. Depending on the tasks of video surveillance, the motion detector of the webcam is configured to detect the movement of objects with the utmost minimization of false alarms (noise filtering), and flexible alarm processing logic is set (alarm recording, integration with other security equipment).

· Audio signal transmission over the network in most cases is carried out by connecting an additional audio module to the webcam. For example, AXIS Communications for expansion functionality webcam releases a dedicated AXIS 2191 audio module that is compatible with most AXIS webcams.

· Password protection is used to restrict access to the webcam to unauthorized persons.

By default, webcam video can be viewed from any network computer, which has a standard web browser installed, such as Internet Explorer or Netscape Navigator. However, you can limit the number of people who can access the webcam by entering a user-level password. Many webcams support multi-level password protection to differentiate access and administration rights.