Ordinary people can also talk and communicate with each other through the camera on the network with video and voice.In addition, people can also use it for various popularDigital video, audio and video processing, etc.
Cameras can be divided into digital cameras and analog cameras.The digital camera canVideo captureEquipment generatedAnalog video signalconvert todigital signalAnd then store it in the computer.Analog camera capturevideo signalMust go through specificVideo capture cardtakeanalog signalIt can be converted to digital mode and compressed before being used on a computer.The digital camera can directly capture the image, and thenParallel portperhapsUSBThe interface is transmitted to the computer.The cameras in the computer market are mainly digital cameras, and new digital cameras are usedData transmission interfaceUSB digital cameras are the main products in the market.In addition, there is another kind ofVideo capture cardIt is used together, but it is not the mainstream.becausepersonal computerThe overall cost of analog cameras is high and cannot meet the requirements ofBSVLCD splicing screenUSB interfacetransmission speed It is much faster than serial port and parallel port, so it is a digital camera with USB interface in the market.The analog camera can be used together with the video capture card or USB video capture card, which is convenient to connect with the computer. The typical application is general video monitoring.Clean areaCamera, embedded special camera in clean area is for clean areaClean roomImportant equipmentKey positionsReal time monitoringA dedicated camera for.The camera is flat panel, embeddedColor steel plateInstallation, zeroSanitary corner, easy to clean, easy to install, can be quickly multi-point control, compatible with mainstream video systems.
camera(webcam) generally has video camera/transmission and still image capturebasic function After the image is collected by the lens, the photo sensitive component circuit and control component in the camera process the image and convert it into digital signals that can be recognized by the computer, and thenParallel portOr the image is restored by the software after the USB connection is input to the computer.
Structural components
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We can list the main structures and components of the camera from its daily working principle.
camera lens
Lens structure, consisting of several lenses, including plastic lens or glass lens.
Two types are required inside the cameraworking voltage : 3.3V and 2.5V, the latest process chip can reach 1.8V.
Remote control
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Normal Edition
1. RemoteSurveillance cameraIt is a remote monitoring camera, main and subNormal Edition, enhanced version and outdoor version, which can rotate 320 degrees from left to right and 60 degrees from top to bottom to monitor, take pictures and record videos, and send photos and videos to the mailbox or FTP server. The camera hasMobile detectionFunction, can set sending email warning, etc.Network Man RemoteSurveillance cameraThe most fundamental difference with traditional cameras is that there is no need for wiring and large-scale hardware assistance. With only one network cable, you can be anywhere in the worldRemote monitoringGo where you want to monitor.
2. The ordinary version of the webman remote monitoring camera is a combination of traditional cameras andnetwork techniqueAs long as the new generation cameraWebman cameraPlug in the network cable (without a computer), it can send the image to the other end of the earth through the network.sureRemote control cameraRotate 320 degrees from left to right and 60 degrees from top to bottom to monitor, record the monitoring picture and send it to the mailbox or FTP server.If you install a webcam in your company or warehouse, shop or home, you can monitor remotely as long as you can access the Internet, even if you go to another place.Ordinary companies create a videoControl platformThere are tens of thousands or hundreds of thousands of cameras that can't be done, and they can only be controlled on a fixed monitoring platform (you can't control them at home or in other places). To buy a webcam, it is simple to install (just plug it into the network cable), and there is no need to do port mapping,Deployment costsLow cost, remote monitoring can be realized.
Enhanced Edition
1. The enhanced version of the webman remote monitoring camera: Compared with the ordinary version, the enhanced version of the webman remote monitoring camera has more powerful performance and can easily achieve the low quality of high-definition imagesnetwork bandwidth Transmission, the image is clearer than the ordinary camera, and new functions such as night vision, audio transmission, dynamic alarm, alarm time zone can be set, and abnormality can be realizedAutomatic recovery, automatic connection after network interruption and other new functions.
2. Outdoor version: compared with the first two versions, the outdoor version of the webman remote monitoring camera has superior performance because of its powerful outdoor video monitoring function. Unlike the enhanced version, it uses professionalCCDPhotosensitive chip(420 lines), hemisphereprotection coverWaterproof and high temperature resistant, strong light and infrared night vision suppression;It can adapt to harsh outdoor environment and supportWireless routingIt is widely used in wilderness areas, taboo areas and dangerous areas, such asConstruction site, residential villas, factories, coffers,construction siteEtc.
Resolution is used to measurebitmap A parameter of the amount of data in the image, usually expressed asdpi(dot per inch).In brief, the resolution of the camera refers to the ability of the camera to analyze images, that is, theImage sensorOfNumber of pixels。Highest resolutionIt refers to the size of the camera's ability to distinguish the highest image, that is, the highest number of pixels of the camera.The resolution of 300000 pixel CMOS is 640 × 480 (307200), and the resolution of 500000 pixel CMOS is 800 × 600 (480000). The updated camera is called720p(1280 × 720921600 (1 million) pixels),1080p(1920 × 10802073600 (2 million) pixels), and even4K(four times the area of 1080p, 8 million pixels), 8K (eight times the area of 1080p, 16 million pixels), etc.The two numbers of resolution represent the unit of points occupied by a picture in length and widthAspect ratioUsually 4:3 or 16:9.
In practical application, if the camera is used forOnline chatOr video conference, the higher the resolution, the greater the network bandwidth required.Therefore, consumers should pay attention in this regard, and should choose a product whose pixels are suitable for their own needs.
commontransport protocolThe comparison relationship with resolution is as follows:
●SXGA(1280 × 1024), also known as 1.3 million pixels
Definition: It is required that the image in the screen should also be white when white objects are illuminated under different color temperature environments.Color temperature represents spectral composition,Color of light。Low color temperature indicationlong waveThere are many light components.When the color temperature changesTricolorThe proportion of (red, green, blue) will change, and the proportion of the three primary colors needs to be adjusted to achieve color balance, which iswhite balanceThe actual adjustment.
Reflecting the colorIdentification abilityAnd the color expression ability of imagingA/D converterOfQuantization precision, refers to how many levels the signal is divided into.CommonColor digits(bit) means.The higher the color depth, the more beautiful and moving the image color will be.Cameras on the marketAll haveUp to 24 bits, some even 32 bits.
Image noise
It refers to the noise in the image.It shows that there are fixed color specks in the image.
visual angle
It is the same principle as human eye imaging. In shortImaging range。It is related to the lens used.
IEEE1394(Firewire) interface (also called elink): its transmission rate can reach 100M~400Mbit/s.
Shopping Guide
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From the perspective of camera composition, the quality of a camera mainly depends on its hardware: lensMain control chipAndPhotosensitive chip。
camera lens
camera
The "full glass" on the fifth floor is also the top camera lens.The lens is composed of lens structure, which is composed of several lenses, generally plastic lens or glass lens（glass）。Generally, the lens structures used by cameras are: 1P, 2P, 1G1P, 1G2P, 2G2P, 4G, etc.The more lenses, the higher the cost;Glass lenses are more expensive than plastic.Therefore, a high-quality camera should use a glass lens, and the imaging effect is better than a plastic lens.Most camera products in the market are forcost reductionGenerally, plastic lens or semi plastic and semi glass lens (i.e. 1P, 2P, 1G1P, 1G2P, etc.) will be used.
Photosensitive chip
(SENSOR) is composed ofDigital cameraAccording to different components.
CCD（Charge Coupled Device，Charge coupled element）, which are generally high-end technical components used in photography,applied technologyMature, good imaging effect, but relatively expensive.
CMOS (Complex Metal Oxide Semiconductor, metaloxide semiconductor Components) are used in products with lower image quality.Compared with CCD, it has low price and low power consumption.
The advantages of CMOS areIntegrationHigh power consumption (less than 1/3 of CCD) and low cost.However, the noise is large and the sensitivity is low.Earlier CMOS had higher requirements for light source. In products using CMOS as photosensitive components, automatic gain reinforcement technology for image light source was used to automatically improve brightnesswhite balancecontrol technology ，Color saturation、contrast ratio、Edge enhancementas well asgammaCorrection and other advanced image control technologies can approach the effect of CCD camera.
Under the same pixelCCDThe imaging is usually very transparent and sharp,Color restorationExposure can ensure basic accuracy.However, CMOS products tend to have general permeability, and they are sensitive to the color of real objectsRestorabilityWeak, and the exposure is not very good.
High end cameras are basically CCD sensitive components, while mainstream products are basically CCD andCMOSIn general, the effect of CCD is better. The size of CCD element is usually 1/3 inch or 1/4 inch. Under the same resolution, it is better to choose the larger element size.Users can choose according to their own preferences.
First, do not use it in a backlight environment (the same as CCD), especially do not point directly at the sun, otherwise“magnifierThe tragedy of burning ants will happen on your camera.secondlyAmbient lightDon't be too weak, or it will directly affect the imaging quality.There are two ways to overcome this difficulty, one is to strengthen the surrounding brightness, the other is to select the minimum requirementIlluminanceFor small products, some cameras can already reach 5lux.
The last thing to note is thatReasonable useDo not underestimate the zoom of the lens. With correct adjustment, the camera can also have the function of shooting chip.Among the digital cameras sold in the market, CCD and CMOS are basically equal.Subject to market conditions andmarket development The camera adoptsCCD image sensorThe main reason is the high cost of CCD image sensor.
Main control chip
The selection of DSP is determined according to the camera cost and market acceptance.DSP designProduction technologyIt has gradually maturedTechnical indicatorsThe difference is not very big, but some DSPDriverFurther improvement is needed.
pixel
(Resolution)Sensor pixels, that is, how many pixels the camera is, which is one of the important indicators to measure the camera. Some products will be marked with 300000 pixels or 350000 pixels in the packaging box.In practical applications, the higher the camera's pixel, theImage qualityThe better, but on the other hand, the higher the pixel, the better. For the same picture, the higher the pixel, the stronger its ability to parse the image, but the amount of data it records will be much largerstorage deviceTherefore, the current mainstream products should be adopted when selecting.Due to the camera priceComputer hardware, imaging effect and other factors, the cameras on the market are basically sold at the level of 300000 pixels.Also, because the CMOS imaging effect is not ideal on high pixels, CCD cameras still dominate the market of high pixel cameras.It is worth noting that some resolution marks refer to what these products can achieve with softwareinterpolationResolution, although the accuracy of the obtained image can also be improved appropriately, there is still a certain gap compared with the hardware resolution.
Capture speed
Video capture capability is realized through software, so the requirements for computers are very high, namelyCPUThe processing ability of the image capture system should be fast enough. Secondly, the capture ability is different for different image requirements.Now the camera captures the imageMaximum resolution640 × 480, no digital camera can achieve the capture effect of 30 frames/second under this resolution, so the picture will bounce.It is more realistic that the combination of hardware and software under 320 × 240 resolution may achieve the acquisition index of standard rate, so for completeVideo capture speed, is only a theoretical indicator.
5. Don't disassemble the camera and try to touch its internal parts unnecessarily, which may cause damage to the camera. Once damaged, the dealer will not give warranty.
6. When storing, the camera should be stored in a clean and dry place.Do not pull or twist the connecting cable, as similar actions may damage the camera.
Machine vision is to use machines instead of human eyes to perceive, measure and judge the external environment.adoptImaging device(i.e. image capture device, including CMOS and CCD) converts the captured target into image signal and transmits it to the dedicatedimage processing system , according to pixel distribution, brightness, color and other information, it is converted into digital signal;Image systemAll kinds of operations are carried out on these signals to extract the characteristics of the target, and then the field equipment action is controlled according to the judgment results.In some systems that require high real-time system actions, humanreaction rate And information processing capabilities can not meet the requirements, and machine vision is easy to achieveinformation integration , andcomputer control system Combined, it can improve the system'sDegree of automation。
Commissioning purpose
The purpose of camera debugging in embedded system is to make the mechanical and electrical parameters of the camera meetsystem requirements Can produce the highest qualityimage data。One involving hardware and softwareImaging systemThe quality of imaging is often affected by many factors from external interference and self limitation, which will produce noise and imagingUneven。Factors from the software level are often algorithmic problems, which can be solved throughtheoretical analysis The factors from the hardware level need to be debugged with instruments through experimentsMeasurement analysisBecause the hardware processes the bottom layer of the system, the quality of the hardware will directly affect the quality of the software, thus affecting the final imaging quality.Debugging the camera is to try to eliminate interference from the hardware level.
Debugging method
Because embedded system is a relatively broad concept, this paper uses HCS12 asMain control chipAs an example, the debugging method is introduced.
Lead out three leads of power, ground and signal from the analog camera to supply power to the camera, and then connect the videoThe signal linereceiveTV boxvideoInput interface。The VGA OUT of the TV box is connected to the CRT display, so that the CRT can display the digitized camera vision.This method is a full hardware level display, providing the same display effect as human vision. It can be used to install cameras and physicallyParameter correctionSignificant help.
1. Display characters in the systemRuntimePrompts system related operating parameters in character form.Each character occupies 8 * 6 point columns and requires 6 bytes of dataCharacter displayIt is only necessary to write the corresponding data in the programming pointing position.Because of theLCD moduleIt does not have a font library, so you need to first defineASCLCD display dot matrix data of table II characters, that is, a size of N * 6 bytes2D array。
2. After the video signal collected by the display image analog camera is digitized by MCU A/D,Information storageIn a 40 * 70 two-dimensional array, the array can be binarized and displayed in a 48 * 84 resolution LCD module, enabling developers to observe the camera machine vision in real time.
This method is a combination of hardware and softwareDisplay methodIt can track and display relevant information of the camera in real time without interrupting the system operation process.
The SCI module of MCU is used to send the picture data to the PC, and the upper computer uses MSCOMM control programming to read the communication data.After reading the data, you can use the powerful data processing ability and picture display ability of Windows programs to process the picture data, such as redrawing the picture according to the data, filtering and analyzing the array and displaying the filtering effect, and exporting the received array as a filecomputer simulationprovidedata sources 。
This method is a complete software display method, which can realize a series of processing on PC only after receiving data from MCU. It has advantages over other methods in checking the effect of graphics transformation, filtering analysis and data simulation ideas.
Comparison of advantages and disadvantages
1. CRT method.By accessing the camera video signal, CRT can display machine vision in high fidelity.However, it can only be limited to the camera parameter test and camera mechanical position adjustment, and it is powerless to deal with advanced digital signals.
2. LCD debugging method.Directly connected tosinglechipData transmission is carried out on SPI port, which can refresh display pictures in real time. This module can be directly mounted on the systemdisplay system Relevant information.However, due to the limitation of module resolution, only black and white binary values can be displayed, resulting in digital image distortion.
3. Serial port debugging method.Make full use of the powerful data processing and picture display functions of PC to realize digital pictureshigh-precisionPixel display and exportGrayscaleValue table, VC,MATLABSimulation provisionfield data。But between PC and MCUData transmission speedToo slow, lackingReal time, lacking the advantages of dynamic tracking.
Automotive Applications
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Automotive effect
a. Rear view of passenger and freight cars
Car camera
b. Passenger car interior (safety, door, luggage compartment) monitoring
c.Special vehiclesImage security record and monitoring (bank cash transport vehicles, urban management vehicles, engineering vehicles, etc.)
d. Car rear view
e. Car driving front view
f. Bus camera
On board trend
a.On board electronicsThe audio application has transited to the stage of audio and video multi-function application.Camera is an important part of vehicle video.
b. With the popularization of rear and front mounting of vehicle mounted displays, cameras have been driven to be widely used.
c. Popular in automobile familiesglobalizationThe crowding of driving and parking provides a lot of space for camera assisted reversing.
d. Automotiveuser friendly designandcustomer demand, driving the development and application of the technology and products.Some models have started to configure camera products when leaving the factory.
e. Camera technology itselfMaturityThe adaptability to the vehicle environment eliminates the technical bottleneck.
Application period
a. Front decoration: designed synchronously with the car, and some models have been launched.In a period of time, the proportion is not large.
b.4SInstallation: special camera for special vehicle, andcar sales Synchronization.It is necessary to launch different products according to the model to achieve the purpose of beautiful installation and convenient application.
c. Post market modification: generally, universal cameras are used, and the price is low.Domestic aftermarketChannel salesAnd foreign trade sales of such products and applications.
According to the hardware development of IT industry“Moore's law”It can be seen that the digital camera also follows its development law, and it is believed that it will develop rapidly in the next few years.From the perspective of market conditions, the main factors restricting the development of cameras are as follows:
1. The camera market started late and consumers' awareness and acceptance were low, soPenetration rateLower,Market capacityThe growth rate is not fast enough, and some guidance is needed to promote market consumption.
2. The actual application of the camera is not wide enough and has certain limitations. It is still sold as a consumer product, and consumers only regard it asVideo chat. Create simple personal image collection, simpleMonitoring systemAnd so on.
3. Computer hardware restrictions, such as computersDisplay card, display resolutionUSB1.1The interface speed affects the real popularity of high pixel photography.
Practical application
It is widely used in agricultural military transportation and other aspects, and its application is very important, especially in transportation and public security.
1. Traffic management: owning cameras makes traffic management more convenient and efficient.
2. Police case solving: The camera plays a very important role in the police case solving, which can be solved through the camera on the road and the community camera.
Intrusion event
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Recently, according toCCTVIt is reported that a large number of home cameras have been illegally invaded, making the previously private scenes of family life peeped and curious by strangers.The news immediately made many people feel frightened and angry.
In fact, from manufacturers, hackers to regulators, to "content" platforms andDisseminatorThe existing law has set up a strict firewall.In the process of production and sales, if the home camera is invaded due to product quality, the manufacturer and business need to bear the corresponding responsibilitylegal responsibility。According to《law for the protection of consumers'interests》Business operators shall ensure that the goods or services they provide meet the requirements for personal and property safety,rights of privacyIs an important onePersonal rights。For home cameras, the product quality is not only limited to the image clarity and service life of the entity, but also includes the security and configuration scheme of the built-in softwarerationality。[1]
