Features and Advantages of VCSEL in Infrared Flood Illumination and Sensing Applications versus Infrared LED

The VCSEL (Vertical-Cavity Surface-Emitting Laser) is a type of semiconductor laser diode that emits a laser beam perpendicular to the top surface, contrary to conventional edge-emitting semiconductor lasers (also in-plane lasers) which emit from surfaces formed by cleaving the chip from a wafer

Infrared lights were originally used for various low-light (night) applications, such as camera assistant exposure light and 2D/3D sensing. However, as applications have evolved, so has the demand for light sources. By combining high-efficiency VCSEL emitters and diffusion materials, VCSELs can achieve a beam angle (irradiation angle) similar to that of LEDs while providing high-precision sensing over a broader range. Additionally, the integration of emitters and diffusion materials into a compact package enables smaller and thinner application products. Therefore, VCSELs have demonstrated characteristics and advantages over LEDs in flood illumination and sensing applications, enhancing the accuracy and performance of applications including machine vision, spatial recognition, and ranging systems.

1. Uniformity: Great Illuminance Uniformity

   VCSELs emit laser light vertically from the mounting surface. With minimal light leakage in the horizontal direction, the light distribution can be controlled to match the camera's viewing angle, such as creating a rectangular illuminated image.

   

2. Wavelength Shifting: Much less Wavelength Shifting per Temperature Chang

   The wavelength shift of VCSELs is less than 1/4 that of LEDs (0.3 nm/℃), at just 0.072 nm/℃, enabling high-precision sensing that is less affected by temperature changes. Compared with LEDs, VCSELs have a narrower spectral width, and due to the smaller wavelength shift with temperature, there is less light loss through the filter. This allows for wider beam angles. In infrared camera applications, band-pass filters (infrared cut-off glass) are typically mounted on the sensor as a countermeasure against interference caused by sunlight during sensing. As a result, light from the VCSEL reaches the sensor more efficiently and eliminates the reddish appearance that can occur with LEDs.

   

   Test Data:

   

3. Filter Transmission Rate: Higher Optical Utilization by Concentrated Spectrum Width

   The elements built into the VCSEL feature a narrow-band emission wavelength, achieving a 4nm emission wavelength bandwidth. This characteristic can enhance the recognition performance on the light-receiving side.

   Comparing the effective power after adding infrared cut filter, transmission rate：VCSEL 84.88%，IRLED 61.5%

4. Diffuser FOV Efficiency (FWHM): Illumination efficiency is greater than 50% of the effective light utilization rate is excellent

   Test Data: Comparison of Corner Poavg:

   

5. Response Time When Pulse Mode: High Speed Pulse Mode

   The response time of VCSELs during emission is 2 ns (Tr/Tf), which is over 7.5 times faster than LEDs (15 ns, Tr/Tf). This rapid response time enables shorter pulse intervals, making VCSELs ideal as a light source for TOF (Time of Flight) cameras that require high-resolution and high-speed sensing.
   ．High resolution and distance resolution.
   ．Clearly capture detailed feature points.
   ．Low latency detection.

   

6. Dimension: Smaller Package Size to Achieve the Same Performance

   

7. iReach VCSEL vs. LED: VCSEL Package, P94B12016, is a superior IR Illumination solution for laptops

   
   

   iReach Corporation (www.ireachcorp.com) provides the industry's best miniaturized, cost-effective 940nm infrared illumination VCSEL solution: