Accurate Measurement of Effective Intensity of Flashlight Lamps

I. Overview of Flash Light Sources

Flash light sources include various instantaneous light sources with pulsed characteristics, such as traffic warning lights, aviation obstacle lights, aircraft anti-collision lights, navigation lights, signal lights, signal flares, etc. Flash light sources have instantaneous characteristics in the time domain, and their brief stimulation to the human eye has special visual effects. Effective intensity is an important parameter for evaluating the optical characteristics of flash light sources, so it is necessary to measure the effective intensity of these lights (including anti-collision lights and signal lights) to ensure they meet specifications.

II. Definition of Effective Intensity

Effective Intensity (cd): The effective intensity of a flash light source (including anti-collision lights and signal lights) is equivalent to the luminous intensity of a constant light source of the same color that produces the same visual range under the same observation conditions. (Definition from - "Aviation Obstacle Lights" MH/T 6012-2015). Effective intensity is an important indicator for measuring the visual perception intensity of flash light sources, which is crucial for the safety and visibility of anti-collision lights and signal lights.

III. Calculation Methods for Effective Intensity

The four commonly used methods for effective intensity calculation are Blondel-Rey-Douglas, Form Factor, Allard, and Modified Allard. These methods are widely applied in effective intensity evaluation of flash light sources, anti-collision lights, and signal lights. (Reference: MODIFIED ALLARD METHOD FOR EFFECTIVE INTENSITY OF FLASHING LIGHTS)

1. Blondel-Rey-Douglas Method:

Where:

• I(t) is the instantaneous luminous intensity of the flash light source;
• (t₂-t₁) is the flash duration
• α is the visual time constant 0.2s;
• For non-rectangular pulses, t₁ and t₂ must satisfy I_eff=I(t₁)= I(t₂).

2. Form Factor Method:

Where:

• F is the form factor;
• I_max is the maximum instantaneous effective intensity;

3. Allard Method

The Allard method is one of the important methods for calculating the effective intensity of flash light sources, widely used in effective intensity testing of anti-collision lights and signal lights.

Where:

• i(t) is the visual sensation;
• I(t): instantaneous intensity;
• α is the visual time constant 0.2s;

• Effective intensity I_eff: the maximum value of i(t).

4. Modified Allard Method:

The visual pulse response function q(t) in the Allard method is modified to consist of two exponential functions, so that the result for rectangular pulses matches the widely accepted Blondel-Rey equation. The Modified Allard method has higher accuracy in effective intensity measurement of flash light sources, anti-collision lights, and signal lights.

IV. Measurement of Flash Light Sources and Effective Intensity Tester

Due to the discontinuous light emission and randomness of flash light sources, the photometric characteristics of flash light sources (including anti-collision lights and signal lights) cannot be tested with conventional photometric instruments and require specialized effective intensity tester. YIMING Technology LUX-200F Flash Light Source Test Analysis System is a professional effective intensity tester specifically designed for photometric measurement of flash light sources, widely used for effective intensity measurement of flash light sources, anti-collision lights, and signal lights. It uses 16-bit high-speed AD to capture the light output signal of the flash light source, and then automatically analyzes it through a powerful microprocessor to obtain parameters such as flash duration, flash frequency, effective intensity, instantaneous maximum and minimum intensity, and average intensity. This effective intensity tester supports multiple effective intensity calculation methods, including the Allard method and Modified Allard method, and can accurately measure the effective intensity values of various anti-collision lights and signal lights.