How to Choose an Infrared Projector?

How to Choose an Infrared Projector? Timing for Infrared Use

Infrared (Infrared) is a type of electromagnetic wave. Whenever any object has a temperature above absolute zero (-273ºC), it will emit infrared radiation. The total wavelength of infrared is about 0.75μm (750nm) to 1,000 micrometers (μm). It is then divided into three types of wavelengths based on their energy content: near-infrared (near-IR / wavelength 0.75 to 2.5μm), mid-infrared (mid-IR / wavelength 2.5 to 25μm), and far-infrared (far-IR / wavelength between 25 and 1000μm), with its wavelength extending up to about 1,000μm, after which it falls into the microwave range.

Regardless of the classification, devices that use infrared as their working light source are now widely applied in security monitoring equipment. Near-infrared can be used in charge-coupled device (CCD) cameras and point-to-point human temperature motion detection sensors. Mid-infrared can be used in infrared gas analyzers and infrared thermal imaging devices. Far-infrared is mainly used for heating purposes, with only a small portion applied in gas analysis, and its importance is currently less widespread compared to near and mid-infrared.

The different infrared wavelengths referenced in various application technologies have theoretical limitations and cannot easily substitute for one another. Moreover, infrared is crucial not because it is invisible light, but because many natural phenomena (the movement and vibration of molecules) emit or absorb radiation energy that conveniently falls into the infrared energy range, making it possible to use infrared to detect the type, quantity, and even appearance of the substances to be analyzed.

When using infrared projectors, the following correct concepts should be considered:

• Using infrared projectors in enclosed indoor spaces is much more effective than outdoors because the walls inside reflect the infrared light source. The infrared projector acts like an invisible light bulb; when using a bulb indoors, the light can reflect off walls or other surfaces, providing better illumination for objects. However, if the bulb is moved outdoors, the lighting effect decreases significantly since most light is scattered, failing to focus on illuminating objects. Consequently, the reflected image captured by the camera will be much poorer than in indoor settings.
• When using infrared projectors outdoors, try to direct the projector downward to the ground to achieve better light source reflection effects.
• The choice of camera lens is crucial; a lens with a larger focal length (in mm) should be used. Wider angle lenses (below 4mm) have poorer infrared effects because their wide angle means less infrared light source is captured by the camera. Unless multiple infrared projectors are used to improve the light source, lenses with larger focal lengths (such as 6/8/12mm or above) are a better choice.
• The greater the distance of the infrared projector (in terms of power), the camera lens must use a larger focal length; otherwise, the reflected infrared light source will be minimal, resulting in a completely dark surveillance image, losing the intended effect of infrared night vision.
• The strength of the infrared projector depends on the intensity of its infrared lamps. When the camera supports infrared (equipped with infrared filters), full night vision can be achieved with the infrared projector, but the captured image will be in black and white. Therefore, when purchasing a camera for use with an infrared projector, ensure that the camera itself supports infrared (IR).
• Generally, infrared projection can be categorized into spotlight and floodlight types. As the names imply, these have different emission angles for infrared light, resulting in varying imaging effects. Spotlight means the infrared light targets specific objects; when viewed from the camera, only the central object is clear, while surrounding objects remain blurred due to lack of light, presenting an overall circle where only the objects within the circle are visible.
• Most infrared projectors on the market are floodlight types, which can directly illuminate an entire area. However, the size of the area is directly related to the strength of the infrared lamp; many infrared projectors and waterproof infrared cameras on the market specify their infrared projection distance, number of infrared lamps, and intensity (which may not always be indicated). Intuitively, one might think that the more infrared lamps, the stronger the projection. However, when purchasing, it is crucial to clearly understand the infrared projection distance! The number of infrared lamps does not necessarily indicate how far they project. For instance, a super-powerful infrared lamp with 25 lamps can project up to 150 to 200 meters, while a regular infrared lamp with 84 lamps can project only 30 meters. When purchasing, also consider waterproofing and size based on site conditions.
• Black objects, water, and wilted plants absorb infrared light and do not reflect it; they should be avoided. Walls, smooth surfaces, metallic materials, cotton objects, healthy plants, and human bodies are more likely to reflect infrared light.
• During installation, positioning the infrared projector to face the same object being monitored will yield night vision effects; generally, it is installed next to the monitoring camera. However, the infrared projector has a sensor among its numerous infrared lamps that can determine whether it is day or night! In other words, if the light is insufficient, the sensor determines it to be nighttime and automatically turns on the infrared lights to enhance nighttime photography. If there is sufficient daylight, it will automatically turn off the infrared projection to prevent overly bright images.
• While operating, the infrared projector emits a faint red light at night, providing a certain deterrent effect for nighttime photography. However, if used for covert recording, it is not very suitable; in this case, a low-light (LUX) camera should be used, which can clearly see in the dark with minimal light. This is a different night vision effect compared to infrared projection.