What are the detection devices for NOTCH FILTER?

NOTCH FILTER (Notch Filter) Testing Equipment (Technical Description)

The core function of UltraOpto NOTCH FILTER (Notch Filter) is to precisely block specific wavelengths of light and efficiently transmit the rest of the spectrum. The test results of its performance parameters directly determine whether the product meets the application requirements of optical systems. For the core indicators of notch filters, such as center wavelength accuracy, cut-off depth, transmittance, and transition band width, professional testing equipment must be used for comprehensive testing. The following is a description of the standardized testing equipment and corresponding test items.

I. Core Optical Performance Testing Equipment

1.Spectrophotometer

Core test indicators: Center wavelength, peak cut-off depth, passband transmittance, transition band width

This is the most basic and core testing equipment for notch filters, including ultraviolet-visible spectrophotometers (suitable for 200-800nm), visible-near-infrared spectrophotometers (suitable for 380-2500nm), and Fourier Transform Infrared Spectrophotometers (FTIR) (suitable for 2.5-25μm mid-infrared).

Testing principle: By shining monochromatic light of continuous wavelengths on the filter and collecting the transmitted light intensity signal, a transmittance-wavelength curve is drawn to precisely locate the center blocking wavelength of the notch filter (deviation ≤ ±1nm), the transmittance in the passband region (general standard ≥ 85%, high-end models ≥ 90%), the peak cut-off depth (general standard OD ≥ 4, high-end custom OD ≥ 6), and the transition band width (the narrower it is, the stronger the wavelength selectivity).

UltraOpto testing standard: Use a double-beam spectrophotometer to eliminate the interference of light source fluctuations, with a test repeatability error ≤ ±0.5%.

2. Ellipsometer

Core test indicators: Film thickness, refractive index, film uniformity

The optical performance of notch filters depends on the precise design and deposition of multi-layer dielectric films. Ellipsometers can non-destructively test the key parameters of the film.

Testing principle: By using the change in the polarization state of the reflected light after the polarized light is incident on the filter surface, combined with a mathematical model to infer the film thickness, refractive index, and uniformity, ensuring that the film thickness deviation ≤ ±0.3nm, to avoid the drift of the notch wavelength and the failure to meet the cut-off depth due to film parameter errors.

Applicable scenarios: Online monitoring during the coating process and verification of the film parameters of finished products.

3. Laser Wavelength Meter

Core test indicators: Center wavelength accuracy of narrowband notch filters

For narrowband notch filters dedicated to laser systems (such as 1064nm, 532nm laser blocking filters), a laser wavelength meter is required for high-precision verification.

Testing principle: Using a standard laser source as the incident light, by comparing the wavelength signals of the incident light and the transmitted light, the center blocking wavelength of the notch filter is precisely calibrated, with a measurement accuracy of ±0.001nm, meeting the strict requirements of high-end scenarios such as laser spectral analysis and lidar.

II. Geometric Precision and Physical Performance Testing Equipment

1. ser Interferometer

Core test indicators: Surface shape accuracy, parallelism

The surface shape accuracy and parallelism of the filter directly affect the direction of light propagation, avoiding light deflection or scattering.

Testing principle: Using the Twyman-Green interferometric optical path, the surface shape error of the filter is analyzed through the morphology of the interference fringes. For general mass production models, the surface shape accuracy needs to reach λ/[email protected], and for high-end custom models, it can reach λ/[email protected]; 1. The parallelism deviation is controlled within ≤0.1 arcmin to ensure no angular offset when the light is incident perpendicularly.

2. High-precision thickness gauges and dimensional measurement instruments

Core inspection indicators: thickness tolerance, dimensional tolerance

Inspection principle: Contact thickness gauges (accuracy ±0.001mm) or non-contact laser thickness gauges are used to measure the uniformity of the filter thickness; the shape dimensions of circular, square, and irregular filters are inspected through a two-dimensional image measurement instrument to ensure dimensional tolerance ≤±0.1mm, meeting the installation requirements of optical systems.

3. Film adhesion tester

Core inspection indicators: film adhesion and abrasion resistance

Inspection principle: According to ISO 15184 standard, the adhesion strength between the film and the substrate is evaluated through tape peeling tests and abrasion tests. After the abrasion test, the change in the passband transmittance of the filter should be ≤1%, with no film peeling or lifting, ensuring the reliability of the product for long-term use.

III. Environmental reliability testing equipment

1. High and low temperature and humidity test chamber

Core inspection indicators: high and low temperature adaptability, humidity tolerance

Inspection principle: Simulating extreme usage environments (temperature range -40°C to 85°C, humidity 85% RH), the filter is placed in the test chamber for a 500-hour cycle test. After the test, the optical performance changes are inspected, with the requirement that the central wavelength drift ≤±1nm and the cut-off depth attenuation ≤0.2OD, meeting the application requirements in complex environments such as outdoor security and industrial inspection.

2. Laser damage threshold tester (LIDT Tester)

Core inspection indicators: laser damage resistance

For notch filters used in laser systems, their laser damage threshold needs to be tested.

Inspection principle: By adjusting the power density of pulsed or continuous lasers and irradiating the filter surface, the critical power density at which the film layer is damaged is recorded. UltraOpto's mass production models have a laser damage threshold ≥100mJ/cm²@1064nm (10ns pulse), ensuring stable operation in high-power laser environments.

IV. Advantages of UltraOpto's inspection process

UltraOpto has established a dual quality control system of "process inspection + 100% final inspection": before coating, the substrate is screened for all parameters; during the coating process, the film parameters are monitored in real-time with an ellipsometer; in the final stage, 100% inspection is conducted using spectrophotometers, laser interferometers, and other equipment to ensure that the performance parameters of each notch filter meet the design standards, providing highly reliable optical components for scientific research, laser systems, and spectral analysis fields.