Harder Digital Gen3 2600 FOM

Harder Digital HD-1520U-AUG-EGC-BW Gen III Image Intensifier Tube – FOM 2600

The Harder Digital HD-1520U-AUG-EGC-BW is a high-performance Generation III 18mm image intensifier tube built around a GaAs photocathode and microchannel wafer architecture. This specification features a minimum FOM of 2600, 72 lp/mm centre resolution and a minimum signal-to-noise ratio of 34 for demanding night vision applications.

The tube uses a P45 black-and-white phosphor screen to produce a monochrome night vision image and incorporates AUTOGATED operation together with external gain control through a third contact. Its fiber optic inverter output and ANVIS-type inverting image intensifier architecture make it suitable for compatible night vision systems designed around this interface.

With a maximum mass of only 78g, a useful photocathode diameter of 17.5mm and operation across a specified temperature range of -55°C to +55°C, the HD-1520U combines high optical performance with environmental durability.

Key Features

• Generation III 18mm image intensifier assembly
• Minimum FOM: 2600
• Minimum centre resolution: 72 lp/mm
• Minimum signal-to-noise ratio: 34
• GaAs photocathode
• P45 black-and-white phosphor screen
• AUTOGATED operation
• External gain control via 3rd contact
• Fiber optic inverter output window
• AVG glass input window
• Minimum photocathode sensitivity: 2200 µA/lm
• Luminous gain: 50,000–80,000 fl/fc
• Minimum peripheral resolution: 57 lp/mm
• Minimum highlight resolution: 45 lp/mm at 20 fc
• Useful photocathode diameter: 17.5mm
• Maximum mass: 78g
• Specified operating temperature: -55°C to +55°C
• Specified MTBF: minimum 10,000 hours

Generation III GaAs Image Intensifier

The HD-1520U-AUG-EGC-BW is specified by Harder Digital as a Generation III, 18mm microchannel wafer, ANVIS-type inverting image intensifier assembly. Its input stage uses an AVG glass window and a GaAs photocathode, while the output uses a fiber optic inverter.

The supplied performance specification defines a minimum photocathode sensitivity of 2200 µA/lm at 2856 K, alongside minimum radiant sensitivity values of 210 mA/W at 830nm and 90 mA/W at 880nm.

FOM 2600 Performance

This HD-1520U specification establishes a minimum Figure of Merit (FOM) of 2600. FOM is derived from the relationship between image intensifier resolution and signal-to-noise performance and is commonly used as a reference point when comparing image intensifier tube specifications.

Harder Digital specifies a minimum signal-to-noise ratio of 34 at 108 µlux together with a minimum limiting resolution of 72 lp/mm at the centre. Minimum peripheral limiting resolution is 57 lp/mm.

P45 Black & White Phosphor

The tube incorporates a P45 phosphor screen, producing the black-and-white scenery image specified by Harder Digital. This configuration is commonly described as white phosphor in night vision applications.

Maximum output brightness at 1 and 20 foot-candles is specified between 3.0 and 4.5 foot-lamberts, while output brightness uniformity across a 17.0mm diameter is specified from 2:1 to a maximum of 3:1.

Autogating & External Gain Control

The HD-1520U-AUG-EGC-BW features AUTOGATED operation and external gain control through a third contact. This provides the electrical architecture required for compatible night vision systems supporting external manual gain control.

The electrical specification lists a continuous input supply voltage from 2V to 3.7V, with a maximum input current of 35mA at ambient temperature and 50mA across the specified operational temperature range.

Optical Performance

Optical Specification	Performance
Photocathode Sensitivity @ 2856 K	2200 µA/lm minimum
Radiant Sensitivity @ 830nm	210 mA/W minimum
Radiant Sensitivity @ 880nm	90 mA/W minimum
Signal-to-Noise Ratio @ 108 µlux	34 minimum
Luminous Gain @ 2 × 10⁻⁶ fc	50,000–80,000 fl/fc
FOM	2600 minimum
Limiting Resolution – Centre	72 lp/mm minimum
Limiting Resolution – Peripheral	57 lp/mm minimum
Highlight Resolution @ 20 fc	45 lp/mm minimum
Useful Photocathode Diameter	17.5mm
HALO	1.0mm maximum
Image Alignment	0.3mm maximum

Modulation Transfer Function

The supplied Harder Digital specification defines the following minimum MTF (Modulation Transfer Function) performance:

Spatial Frequency	Minimum MTF
2.5 lp/mm	92%
7.5 lp/mm	80%
15 lp/mm	61%
25 lp/mm	38%

Tube Spot Specification

Harder Digital specifies allowable opaque spots according to their diameter and position across three defined image zones. Bright spots are not allowed under the supplied performance specification.

Opaque Spot Diameter	Zone 1 Ø 5.6mm	Zone 2 Ø 5.6–14.7mm	Zone 3 Ø 14.7–18.0mm
228–300 µm	0	0	0
152–228 µm	0	1	1
76–152 µm	1	2	2
Bright Spots	Not Allowed

Electrical Characteristics

Specification	Performance
Continuous Input Supply Voltage	2–3.7V
Input Current – Ambient	35mA maximum
Input Current – Operational Temperature Range	50mA maximum
Reverse Polarity – No Damage	60 seconds minimum
BSP	60 seconds minimum

Environmental Characteristics

Specification	Performance
Operating Temperature	-55°C to +55°C
Storage Temperature – 4 Hours	-57°C to +71°C
Storage Temperature – Long Term	-35°C to +55°C
Shock	75g
Vibration	2.5g
Mean Time Between Failure	10,000 hours minimum
Force on Bearing Surface	200N maximum

Technical Specifications

Specification	Details
Manufacturer	Harder Digital
Model	HD-1520U-AUG-EGC-BW
Generation	Generation III
Format	18mm Microchannel Wafer, ANVIS Type, Inverting
Input Window	AVG Glass
Photocathode	GaAs
Output Window	Fiber Optic Inverter
Screen Phosphor	P45 – Black & White
Image Inversion	Yes
Gating	AUTOGATED
External Gain Control	3rd Contact
Mass	78g Maximum

Why Choose the Harder Digital HD-1520U Gen III?

The Harder Digital HD-1520U-AUG-EGC-BW combines a minimum FOM of 2600 with 72 lp/mm centre resolution, SNR 34, a high-sensitivity GaAs photocathode and P45 black-and-white output. AUTOGATED operation, external gain control and an 18mm ANVIS-type architecture make this specification a high-performance image intensifier option for compatible night vision systems requiring demanding optical and environmental performance.