QHYCCD QHY991 Class 1 SWIR Camera

QHY991 SWIR Camera: Applications from 400 nm to 1700 nm

The QHY990/991/992 cameras are scientific short-wave infrared cameras with a broad spectral response from 400 nm to 1700 nm and high sensitivity.

Applications include SWIR astronomy imaging and photometry, daytime star observation, optical communications, laser, scientific research and optical laboratory applications.

Sony IMX991 Sensor: 5.0 µm Pixels and 656 x 520 Resolution

At the heart of the QHY991 is the Sony IMX991, a monochrome InGaAs sensor with a 656 x 520 pixel array and a 4.19 mm diagonal. The sensor is Class 1 and the format 1/4 inch.

The sensor's architecture incorporates Cu-Cu (copper-to-copper) interconnect technology. It gives very low FPN noise and a low defect pixel ratio. The sensor uses an electronic global shutter, so every pixel is exposed at the same time.

Imaging Performance: 112ke- Full Well and 77% Peak QE

The camera digitizes with a 12-bit ADC (4,096 levels), with a typical full well capacity of 112,000 e-.

Quantum efficiency (QE) peaks at an impressive 77% at a wavelength of 1200 nm, and the typical read noise is 135 e-, measured after bias frame FPN calibration. The QHY991's dark current is 64.6 e-/pixel/sec at -30°C and gain 0.

TEC Cooling: A 35°C Delta for Low-Noise InGaAs Operation

InGaAs sensors typically have larger dark currents than silicon-based sensors, so powerful cooling is necessary. The QHY991 integrates a dual-stage thermoelectric cooling (TEC) system that reaches 35°C below ambient.

The camera has an anti-dew heater, and all QHY cooled cameras have built-in heating plates to prevent fogging of the chamber window. Raise TEC power gradually and lower it before switching off to avoid thermal shock.

High-Speed Data: 123 FPS via USB 3.0 with a 128MB Buffer

The QHY991 is designed for high-throughput applications, transferring data over a fast USB 3.0 interface. It can sustain a maximum frame rate of 123 FPS at full 656 x 520 resolution, in both 8-bit and 16-bit modes. With a 480-line region it reaches 132 FPS at 8-bit and 16-bit.

A 128MB DDR2 buffer holds frames before they go to the computer. The IMX991 has two exposure modes: in one, exposures shorter than the frame interval can show two background bias levels; in the other, the frame rate stops rising below 8ms exposure and the two bias levels are avoided. The mode is set through the QHYSDK.

Optical Interface: C-Mount with 17.5mm Back Focus

The QHY991 has a standard male C-mount front connection. The back focus is 17.5 mm, and 1.25 inch support is available with an adapter. QHYCCD offers SWIR lenses for the QHY990 and QHY991.

The camera body also includes an integrated holder for 25 mm filters, a very common filter type for lab applications; it supports D=25mm and D=25.4mm filters. The optical window has an AR+AR multi-layer anti-reflection coating.

Astronomy in the Short-Wave Infrared: Beyond 1000 nm

The series' applications include SWIR astronomy imaging and photometry. An Orion Nebula first light image, taken with the QHY992 and a 1200-1700 nm bandpass filter, shows details in the nebula's center that differ from visible light.

Daytime star observation is another application, and stars have been captured in the daytime with a QHY991 by Martin Miller.

QHY991 vs. QHY990 & QHY992: A Model Comparison

The QHY991 is part of a family of SWIR cameras that includes the QHY990 and QHY992. They differ mainly in resolution, pixel size and frame rate.

• QHY991 (This Model): 656 x 520 pixels of 5.0 µm, 123 FPS at full resolution, 24W at 100% TEC.
• QHY990: Provides a larger field of view with its 1296 x 1032 resolution and the same 5.0 µm pixels. It reaches 66 FPS and draws 40W at 100% TEC.
• QHY992: 2592 x 2056 pixels of 3.45 µm, 32 FPS at 16-bit, and a full well of 30ke- (LG AllPixel Mode).

Software & Drivers: The QHYCCD All-In-One Ecosystem

QHYCCD provides a comprehensive All-In-One software package to operate the QHY991. Install it before connecting the camera.

The All-In-One pack contains:

• System Driver: The fundamental driver required for the camera to communicate with the computer.
• EZCAP_QT: QHYCCD's own software for device tests, update management and basic image capture; install it even if you capture with other software.
• ASCOM Driver: For ASCOM programs; QHYCCD uses MaxIm DL as its example. N.I.N.A connects through the QHY plugin or the ASCOM driver.
• SharpCap: Included in the pack, authorized by SharpCap, in 32-bit or 64-bit.
• WDM Broadcast Driver: Provides a live signal to OBS and other live software, for uses such as a live show.

Power and Build: A 520 g Scientific Instrument

The QHY991 weighs 520 g and measuring 92.5 mm in length. The camera requires a stable 12V DC power supply (rated for 11V to 13.8V) to operate the dual-stage TEC cooler and electronics. Power consumption is 24W when the cooler is operating at 100% power.

If the input voltage is too low, the camera may stop functioning or reboot when the TEC power percent is high; the input voltage cannot be lower than 11.5V.

First Session with the QHY991: Setup and Connection

The order is as follows:

1. Install Software First: Before connecting any hardware, download and run the latest QHYCCD All-In-One installer package. This pre-installs all necessary system drivers, ASCOM drivers, and SDKs.
2. Connect 12V Power: Connect a stable 12V DC power supply to the camera's power port. The cooler and main electronics require this power source to initialize correctly.
3. Connect USB 3.0 Cable: After connecting the 12V power, connect the USB 3.0 cable from the camera to your computer. The camera will not be recognized if it is not powered before connecting to the computer.
4. Launch Software: Open your preferred imaging software, such as EZCAP_QT, SharpCap, or N.I.N.A. Select the QHY991 from the camera list to connect. For cooling, click Auto and set a target temperature. Use 64-bit software such as SharpCap x64 and N.I.N.A x64.