Developed for new automotive applications

An IRED is a light-emitting device whose peak wavelength exceeds 780 nm. IR communication systems such as household electric appliances, remote controls, etc., are already in use in a wide range of applications. Among these IREDs, demand for high-output IREDs has recently increased. They are aimed at nighttime security lighting systems such as security cameras, light sources of TOF (Time Of Flight) type distance image sensors, etc. More recently, IREDs are expected to be applied to driver monitoring systems (DMS) that detect the driver's conditions (such as dozing), sensors for automatic driving systems, etc. Stanley Electric developed high-efficiency high-power IREDs aimed at existing applications as well as more advanced applications (Fig. 1). There are two types of devices emitting at 855 nm and 945 nm, with narrow directivity ― 60 degrees type (M□N1105MS) － and wide directivity － 120 degrees type (M□N1106MS). "Demands for the security field will increase towards the Tokyo Olympic Games in 2020. In addition to automotive systems such as DMS, new applications such as disaster prevention cameras that protect civic life from abnormal weather, and light sources for biometric authentication systems are expected to be in high demand" (Mr. Seitaro Kondo, Stanley Electric, Optoelectronic Device Division, Sales Department III).

Fig.1: High-efficiency high-power IREDs

(Left) Narrow directivity type 「M□N1105MS」 (Right) Wide directivity type「M□N1106MS」

Increased freedom in equipment design

A major feature of Stanley Electric's newly released high-efficiency high-power IREDs is that both 855 nm and 945 nm devices achieve more than 610 mW/W (radiant flux / input power), and it is the highest luminous efficiency in the IR field. Therefore, high output can be obtained with the same current as the conventional one. "We have newly developed an LED with low forward voltage (Vf) and capable of high power output" (Mr. Kondo). In the market, to increase light output there are many devices whose forward voltage value is equivalent as two LED dies. However, such a device is disadvantageous to suppressing power consumption. Therefore, in Stanley Electric's high-efficiency high-power IREDs, the forward voltage value is equivalent to one LED die and die materials and structure are optimized multilaterally, aiming for high efficiency. Furthermore, using the optical design know-how and packaging technology cultivated with automotive LEDs, Stanley Electric also optimized the optical lenses mounted on the LEDs' top surface, thereby maximizing the efficiency of light emitted from the die.

High-efficiency high-power IREDs with such features bring many advantages to equipment designers. "For example, we can dramatically reduce the number of IREDs built into security cameras. In concrete terms, the same brightness as the light source made up of 36 conventional through-hole IREDs can be obtained with just one LED. The same power consumption can be achieved with 3 LEDs, and it can illuminate brightly and widely" (Mr. Kondo) (Fig. 2). In other words, by adopting a high-efficiency high-power IR LED, not only is it possible to reduce the cost by decreasing the number of parts, but also to reduce the size of the entire unit by making the light source smaller.

Another advantage not to be overlooked is that high-efficiency high-power IREDs can suppress generation of heat during lighting, by increasing efficiency (Fig. 3). In addition to contributing to reducing substrate temperature, simplification of the heat dissipation mechanism results in cost reduction and high packaging density. The newly released high efficiency high-power IRED is a newly designed compact package (3.8 mm long × 3.8 mm wide × 2.1 to 2.8 mm high), using ceramic with high heat dissipation properties and Cu (copper), adopted to further improve heat dissipation. "It is advantageous in securing reliability of the final unit, since the limitations due to heat will be low and the design degree of freedom will increase" (Mr. Kondo).

Fig. 2: Contributing to equipment downsizing

(Left) Example of security camera employing conventional through-hole IREDs (36 pcs)
(Right) Example of security camera employing high-efficiency high-power IREDs (3 pcs)

Fig. 3: Reduced heat compared to conventional products

Development of IRED floodlights

Stanley Electric provides electronic devices such as LEDs, as well as applied products such as various modules and equipment using electronic devices. The company is also developing equipment mounting high-efficiency high-power IREDs. At "CEATEC JAPAN 2017", Stanley Electric showcased a sample exhibit of IRED floodlight for long distance security cameras, equipped with high-efficiency high-power IREDs (Fig. 4). It deploys IREDs and optical lenses mounted on a small casing with an external size of 55 mm × 55 mm × 60 mm. The optical lens design has been optimized, making full use of advanced simulation technology. The directional half-angle of 3 degrees and the light distribution angle are throttled down a lot, so that IR light reaches far (Fig. 5). Using this floodlight, it is possible to capture an object 100 meters ahead.

Stanley Electric, which has commercialized IREDs featuring characteristics that make it distinctive from competitors, will create a new market for IREDs, making full use of LED dies and optical designs that have been proven to a great extent in automotive applications.

Fig. 4: Emitter with high-efficiency high-power IREDs

Fig. 5: Optical design simulation