KEYENCE Laser Sensors - Laser Distance Measurement
The beam radius W is defined as the radius at which the irradiance decreases to 1/e 2 or 0.135 of the peak on-axis (r = 0) value. This is sometimes referred to as the half-width 1/e 2 (HW1/e 2) value. As shown in Figure 1, W gradually increases as the distance from the minimum beam radius (known as the beam waist, W 0 gets larger.