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Dash Cam

Equipment used to provide scientific basis for traffic accident handling

The function of presenting video and audio in real time provides a more scientific basis for our handling and positioning of traffic accidents, and fully guarantees our property and life safety.



1. Provide reliable evidence for the analysis and judgment of traffic accidents.

2. It is convenient for drivers and passengers to check the situation in the car.

3. Provide a basis for dealing with passenger disputes in the car, finding lost and found, anti-robbery and anti-theft issues.

4. Provide monitoring of the environment inside and outside the car to provide safety guarantee for the driving of the vehicle.


What kind of dash cam is good? The performance of the camera can be examined from the following aspects:

1. Sensor

CCD and CMOS sensors are an important part of the reversing camera, which can be divided into CCD and CMOS according to different components. CMOS is mainly used in products with lower image quality. Its advantage is that its manufacturing cost and power consumption are lower than that of CCD. The disadvantage is that CMOS cameras have higher requirements for light sources; Comes with a video capture card. There is a big gap between CCD and CMOS in terms of technology and performance. Generally speaking, CCD is better, but the price is also more expensive. It is recommended to choose a CCD camera without considering the cost.

2. Clarity

Clarity is one of the important indicators to measure the camera. Generally speaking, products with higher definition will have better image quality. Products with a resolution of 420 lines have become the mainstream products of reversing cameras, and 380 lines can also be selected if the adjustment is good. There are better chips with 480 lines, 600 lines, 700 lines, etc. But depending on the chip level of each camera, the difference in photosensitive elements, including the level of debugging technicians, the quality and effect of products with the same chip and the same level may vary. Similarly, it also depends on what kind of lens is used. A lens made of good materials will have a much better image rendering effect. On the contrary, the night vision effect of high-definition products will be somewhat reduced.

3. Night vision

The night vision effect is related to the definition of the product. The higher the definition, the night vision effect of the product will not be very good. This is because of the chip itself, but good quality products have night vision function, and will not image objects. The effect, although the color will be worse, but the clarity is not a problem. If there is infrared night vision fill light or LED white light fill light, the night vision is more clearly visible at night

4. Waterproof

The reversing camera products are basically waterproof

To sum up: when choosing a reversing camera, consider the above aspects, the most important thing is to see and compare the actual effect of the image.

5. Special car reversing camera

Many cars have already produced special-purpose reversing cameras that can be used with more than 500 models. When choosing, you must first choose the reversing camera dedicated to your model, if not, then choose a general-purpose reversing camera.

6. Universal camera.

General-purpose cameras include 18.5mm perforated cameras, small butterfly external cameras, license plate frame cameras, 28mm perforated cameras, bus cameras and other external cameras, etc., such as the LED night vision color external camera for the car navigator


The lens of the dash cam is the core component, and the four key parameters are as follows:

Focal length

The size of the focal length determines the size of the field of view. The value of the focal length is small, the field of view is large, and the observed range is also large, but the objects at a distance are not clearly distinguished; the value of the focal length is large, the field of view is small, and the observation range is small. As long as the focal length is selected properly, even objects that are far away can be seen clearly. Since the focal length and the field of view are in one-to-one correspondence, a certain focal length means a certain field of view, so when choosing the focal length of the lens, it should be fully considered whether the observation details are important or a large observation range is important. If you want to see details, choose a long-focus lens; if you want to see a big scene at close range, choose a wide-angle lens with a small focal length.

Aperture coefficient

That is, the luminous flux, represented by F, is measured by the ratio of the focal length f of the lens to the clear aperture D. Each lens is marked with a maximum F value, for example, 6mm/F1.4 represents a maximum aperture of 4.29 mm. The luminous flux is inversely proportional to the square of the F value, the smaller the F value, the greater the luminous flux. The standard values of the aperture index series on the lens are 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, etc. The rule is that the exposure at the previous standard value is exactly 2 of the exposure corresponding to the latter standard value. times. That is to say, the clear aperture of the lens is 1/1.4, 1/2, 1/2.8, 1/4, 1/5.6, 1/8, 1/11, 1/16, 1/22, the previous value is The root sign of the latter value is 2 times, so the smaller the aperture index is, the larger the aperture is, and the illuminance on the imaging target surface is also larger. In addition, the aperture of the lens is divided into manual (MANUAL IRIS) and automatic aperture (AUTO IRIS). Used with the camera, the manual aperture is suitable for occasions where the brightness does not change much. Its light input is adjusted through the aperture ring on the lens, and it can be adjusted at one time until it is suitable. The auto-iris lens will automatically adjust as the light changes, and is used in outdoor, entrance and other occasions where the light changes greatly and frequently.

Auto iris lens

There are two types of automatic iris lenses: one is called video (VIDEO) driven type, and the lens itself contains an amplifier circuit to convert the video amplitude signal from the camera into the control of the iris motor. The other type is called a direct current (DC) drive type, which uses a DC voltage on the camera to directly control the aperture. These lenses contain only a galvanometer aperture motor and require an amplifier circuit within the camera head. For all kinds of automatic aperture lenses, there are usually two adjustable knobs, one is ALC adjustment (light metering adjustment), there are two options for peak metering and average metering according to the target lighting conditions, and the average metering file is generally used; The other is LEVEL adjustment (sensitivity), which can make the output image brighter or darker.

Zoom lens

Zoom lenses are divided into manual (MANUAL ZOOM LENS) and electric (AUTO ZOOM LENS). Manual zoom lenses are generally used in scientific research projects and not in closed-circuit surveillance systems. When monitoring a large scene, the camera is usually used with a motorized lens and a pan/tilt. The advantage of the motorized lens is that it has a large zoom range. It can not only see a wide range of situations, but also focus on a certain detail. In addition, the gimbal can rotate up and down, left and right, and the viewing range is very large. Motorized lenses have multiple magnifications such as 6x, 10x, 15x, and 20x. If you know the reference focal length, you can determine the variable range of the focal length of the lens. For example, a 6x motorized lens with a base focal length of 8.5mm, its zoom range is continuously adjustable from 8.5 to 51mm, and its field of view is 31.3 to 5.5 degrees. The control voltage of the motorized lens is generally DC 8V~16V, and the maximum current is 30mA. Therefore, when selecting a controller, the length of the transmission cable must be fully considered. If the distance is too far, the voltage drop generated by the line will cause the lens to be uncontrollable. It is necessary to increase the input control voltage or replace the video matrix host to cooperate with the decoder control.

In addition to the above four items, of course there are other minor details, but mastering these four index coefficients can properly configure and use the lens.

Working principle

The power supply of the camera is connected to the reversing tail light. When the reverse gear is engaged, the camera is powered synchronously and enters the working state, and the collected video information is sent to the wireless receiver placed at the front of the car through the wireless transmitter. The receiver transmits the video information through the AV The IN interface is transmitted to the GPS navigator, so that when the receiver receives the signal, no matter what kind of operation interface the GPS navigator is in, it will give priority to the LCD screen for the reversing image video.

The difference between a car camera and a car monitor and a car DVD navigator when using a portable GPS navigator is that when using a car monitor, the car monitor does not need to be turned on, as long as the car monitor is in reverse gear, it will automatically display the car camera image; and the car DVD navigation is Generally, the car camera image can be displayed only when the device is turned on; when using a portable GPS navigator, the car camera image can only be displayed when the navigator is turned on

Installation requirements

Today, with the rapid development of automotive electronics and security technologies, on-board cameras have become indispensable hardware for traffic safety.

Next, let's introduce the installation skills and troubleshooting of vehicle products.

1. The working temperature of the on-board camera on the market is between 0-50 degrees. The reason is that it is inside the car, and the temperature requirements are higher than those of ordinary monitoring hosts. The main left and right of the on-board camera is to monitor the working status of the driver and flight attendant. , and sudden time monitoring, provide good evidence for traffic accidents, and play the function of the black box of the car.

2. Cameras on the market generally have two kinds of storage devices, ordinary computer hard disk and sd card. The sd card is characterized by good shock resistance, but the storage space is only about 8 hours, and the maintenance cost is high. The ordinary hard disk can support 300g , can record for one month.

3. In fact, in addition to the monitoring function, the car camera also has multimedia playback, vehicle speed, license plate number, speed overlay, driver data overlay and gps/gprs and wireless transmission functions.

4. Because of the particularity of its installation, the car camera has certain requirements when installing it. It needs to be small in size and light in installation. It cannot affect the passenger’s riding environment and needs to be conveniently fixed, which will affect the monitoring effect. It has a little shock resistance. The most important thing is to have an infrared light, which is convenient for monitoring when the light is not good. It is recommended that you use a small dome and a conch camera with a built-in infrared light.

5. Because the car camera industry has just started, customers do not have high requirements for this color at first, and the price of color is relatively expensive, but with the development of technology, color cameras will become more and more widespread.

6. The installation cost of a bus mainly includes the following pieces: host cost, camera cost, hard disk, wire, installation cost, the price of different host equipment is different, the price of different cameras is also different, and the host price itself varies in the market It is relatively large.

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E-mail: fairy@hampotech.com

Post time: Mar-14-2023