Is natural light used to photograph animal activities at night?

There are many kinds of cameras, and the basic principle of their work is the same: converting optical image signals into electrical signals for storage or transmission. When we shoot an object, the light reflected by the object is collected by the camera lens and focused on the light receiving surface of the camera device (such as the target surface of the camera tube), and then the light is converted into electric energy by the camera device, and a "video signal" is obtained. The photoelectric signal is very weak, so it needs to be amplified by pre-amplifier circuit and then processed and adjusted by various circuits. The final standard signal can be sent to video recorders and other recording media for recording, or spread through a propagation system, or sent to a monitor for display.

infrared camera

Pinyin: Ji Xiang Infrared Society

English: infrared camera

The visible light that human eyes can see is arranged from long to short wavelength, which is red, orange, yellow, green, cyan, blue and purple in turn. The wavelength range of red light is 0.62 ~ 0.76 micron; The wavelength range of violet light is 0.38 ~ 0.46 μ m, the light with shorter wavelength than violet light is called ultraviolet light, and the light with longer wavelength than red light is called infrared light, which is invisible to naked eyes. Because digital cameras use CCD to sense all light (visible light, infrared light, ultraviolet light, etc.). ), the image taken is very different from the image produced by our naked eyes only seeing visible light. In order to solve this problem, the digital camera is equipped with an infrared filter between the lens and the CCD, whose function is to prevent infrared rays from entering the CCD, so that the CCD can only perceive visible light, and the images taken by the digital camera are consistent with those seen by our naked eyes.

Infrared night vision means that in the night vision state, the digital camera will emit infrared rays invisible to the naked eye to illuminate the subject, and turn off the infrared filter to stop the infrared rays from entering the CCD. After the infrared ray is reflected by the object, it enters the lens for imaging. At this time, what we see is an image reflected by infrared rays, not by visible light, which means that we can shoot an image that is invisible to the naked eye in a dark environment.

At present, most infrared cameras use LED infrared light emitting diode as the main material of infrared cameras. Detailed product drawings and appearance are as follows:

Principle, characteristics, selection and use of infrared camera

In the project of TV monitoring system, infrared ray was rarely used in the past, but due to the increase of crime rate in today's society, infrared ray plays a more prominent role in night monitoring, which is not only used in treasury, oil depot, armory, library, cultural relics department, prison and other important departments, but also used in general monitoring systems. Even the TV monitoring project in residential areas has applied infrared cameras. This shows that people's requirements for TV monitoring system engineering are becoming more and more standardized and higher. More and more important places need 24-hour continuous monitoring.

The method of realizing night vision can use conventional visible light illumination, but this method can not only hide, but also expose the monitoring target. At present, hidden night vision monitoring adopts infrared camera technology. Infrared camera technology is divided into passive infrared camera technology and active infrared camera technology. The principle of passive infrared camera technology is that any object will emit infrared light above absolute zero (273℃). Because the infrared light emitted by human body and heated objects is strong, and the red light emitted by other non-heated objects is weak, special infrared cameras can be used to realize night monitoring. Passive infrared camera technology is not used in night vision system because of its high equipment cost and inability to reflect the surrounding environment. Active infrared camera technology uses a special "infrared lamp" to artificially generate infrared radiation that is invisible to human eyes but can be captured by ordinary cameras to "light up" the scenery and environment, and uses ordinary low-illumination CCD black-and-white cameras, or cameras that automatically change color to black and white during the day and night or "infrared low-illumination color cameras" to feel the infrared light reflected by the surrounding environment, thus realizing night vision.

Principle and characteristics of infrared camera

Light is an electromagnetic wave with a wavelength ranging from a few nanometers (1nm= 10-9m) to 1 mm (mm). What is visible to the human eye is only a part of it, which we call visible light. The wavelength range of visible light is 380 nm to 780 nm. Visible light can be divided into red, orange, yellow, green, blue and purple light from long to short. The wavelength shorter than violet light is called ultraviolet light, and the wavelength longer than infrared light is called infrared light.

According to its infrared radiation mechanism, infrared lamps can be divided into two types: semiconductor solid-state emission (infrared emitting diode) infrared lamps and thermal radiation infrared lamps. Generally speaking, infrared lamps with infrared light-emitting diodes are mainly used in the market, and their principles and characteristics are introduced as follows: A luminous body consists of an infrared LED matrix. The infrared emitting diode is made of a material with high infrared radiation efficiency (usually gallium arsenide GaAs), and a forward bias is applied to inject current into the PN junction to excite infrared light. The central wavelength of spectral power distribution is 830 ~ 950 nm, and the half-peak bandwidth is about 40nm, which is a narrow-band distribution and can be felt by ordinary CCD black-and-white cameras. Its biggest advantage is that there is no red explosion at all (using infrared tubes with wavelength of 940 ~ 950 nm) or only weak red explosion (red explosion has visible red light), and its service life is long. The emission power of infrared light emitting diode is expressed by irradiance μW/m2. Generally speaking, its infrared radiation power is proportional to the forward working current, but when it is close to the maximum rating of the forward current, the temperature of the device rises due to the heat consumption of the current, which makes the luminous power decrease. If the current of infrared diode is too small, it will affect its radiation power, but if the working current is too large, it will affect its life and even burn out the infrared diode. In view of this situation, Foxconn's FI-930C and FI-970C fully considered this problem when designing, and adopted high-efficiency light-emitting diodes and built-in cooling system in the camera, so that the camera can work stably for 25,000 hours!

Selection and use of infrared camera

The most important problem in the selection of infrared lamp is the completeness of infrared lamp, camera, lens, protective cover and power supply. At present, most cameras and infrared projectors on the market are separated, so we must consider all the equipment in the design scheme. Do you choose a black-and-white camera with infrared light or a color-to-black camera? There are also installation methods and waterproof considerations. Generally speaking, the CCD sensor used in black-and-white cameras has a wide sensitive spectrum, including not only the visible region, but also the infrared region. CCD sensor can be imaged clearly by using auxiliary infrared lamp illumination, while the photosensitive spectrum of ordinary color camera is only in the visible light region, which is not suitable for infrared bulb illumination. Day and night cameras use two CCD switches or a CCD sensor, and infrared bulbs can also illuminate the camera by switching digital circuits, but there are shortcomings such as high black and white illumination or bad influence on color. In addition, there is an integrated infrared camera, which integrates the camera, lens, protective cover and infrared lamp. Typical products of Foxconn, such as FI-930C and FI-970C, adopt high-quality aluminum shells. Through one-step molding production process, the waterproof grade of the product reaches IP55, which can be used indoors and outdoors. Due to the integrated design, the construction debugging is naturally reduced.

With the rapid development of infrared night vision system, there will be more and more manufacturers of infrared lamps, but infrared products are not as easy as some people think, and the conditions in technology and testing equipment are also different. I hope users can make more comparisons and choose carefully.

Users should first read the instruction manual carefully when using the infrared lamp, especially the precautions to ensure the safety of personal equipment. Check whether the above support aspects meet the requirements and whether the influencing factors should be considered. If not, adjust the equipment used in time.