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Device controlling

Device calibration

The capture device must be calibrated once before its first use, when the system is fully installed. The calibration is a long process (30-60 sec.) that calculates the parameters of the device and stores them in a calibration file on the local file system. For successful calibration the calibration image must be put on the document window of the device with the squared side facing down.

Some types of devices can hold a factory default calibration file. Reading the file from the device may take a long time, which consequently slows down the system startup. To save time the file is automatically copied to the local file system at the first attempt of using the device.

The new image correction and calibration technology became much more difficult, so devices using this technology can only be calibrated with factory calibration software and images, but not with the standard calibration function.

The calibration file

The calibration state of the device can be tested with the IsCalibrated function. New calibration process can be started with the Calibrate function, and the resulted calibration file can be placed in one of the following three different directories where our system searches for the newest version of this file:

The exact path and filename of the used calibration file can be read from the calib_file property. The calibration file contains information about the device only and may be freely copied from a computer to another.

Between captures

Between two capturing processes the light and camera control modules are in a so called freerun mode. In this mode the system can run a set of the following tasks that the user can enable through the freerun_mode property:

The usable modes are defined in the PR_FREERUNMODE enumeration. Depending on the type of the device some tasks cannot be combined.

UV warming

The warming up and cooling down times of the UV tubes are approximately 25 seconds. Though acceptable images can be obtained in less warming time, the best image quality is achieved when the UV tubes are warmed up completely. The needed warming quality can be controlled by the uvwarm_quality property in range of 0 to 1000. If the quality is set to 1000 and the tubes are cool, it takes 25 seconds to capture an UV image.

If the UV tube warming task is set in the freerun mode and the uvwarm_quality property is set too, the system waits for the UV tube to warm up before the first capture and the warmed state of the UV tube is continuously preserved between successive captures.

Preview

The lighting conditions of the preview image can be set by the preview_light property. Possible values are defined in the PR_LIGHT enumeration.

To capture a real-time preview image, the user can either call the CapturePreview function or handle the preview related events (see Event handling). To view the captured image, the image display function is to be called with PR_IT_PREVIEW image type. The preview light control works only if freerun mode is set properly.

Document Detection Modes

There are different document detection modes for different devices, that can be set through the testdoc_mode property. The document detection uses both software and hardware elements. The hardware element checks the presence of the document, and the software element detects the motion.

The available document detection modes are defined in the PR_TESTDOCMODE enumeration:

Detection of Dark documents

Some types of devices can detect dark documents such as the back side of blue or green passports. To enable this functionality the ctrl/detdark property has to be set to 1.

Controlling the device

Different types of devices use different illumination sets. The available lights can be queried using the LightList function. The devices can have status leds and buttons which are fully controllable by the user through the SetStatusLed, TestButton and GetButtonEvent functions, except the power led available on some devices. The devices can report their power state (see Event handling) or it can be queried using the TestPowerState or TestPowerLevel functions.

Storing user defined data in the device

There is the possibility of storing user data in the internal memory of the device. The size of the enabled free space can vary between different types of devices. It can be used for example to store user defined serial number, legacy information or other general information restricted to the device.

User data space access is on block level, using device dependent fixed-size blocks. One can use the GetUDInfo function to get general information about the user data space - the size of one block and the number of available blocks. The first block index and the number of blocks to use must be defined at each user data read or write.

Note:
As the number of writes of an EEPROM chip is limited, please use this feature carefully.


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