SHIL - Section Half Imaging Logger

Imaging Specialist's Responsibility

Camera and image processing calibrating is an essential procedure to take in attempting a proper tonal and color managed workflow. Calibration should only be done once an expedition, where the SHIL is set up to image both dark and light cores. However, if you run into problems, or if scientists request different processing of the section scans, you will be required to recalibrate during an expedition.

Quality monitoring of the scans should be done daily (ideally at the start and at the end of your shift), to quickly identify problems and if you need to rescan a section.

SHIL set up

Changing the scan rate

Creating 360 images

VCD configuration user guide

SHIL barcode gun rules

360 Uploader USG

Quality Monitoring

SHIL Images Review

When to rescan

Reported Issues

Understanding Line Scan Camera

A line scan camera has a single line of pixels that image across an object. To build up a two-dimensional image of the object, the camera moves perpendicular to the line of pixels down the track. Line scan cameras are better than frame cameras when the product speed is high, because you can compensate for short exposure times by using concentrated illumination and Time Delay and Integration (TDI) to increase the photons “harvested” by the camera.

Figure 1. One optical path with 3 lines x 2048 pixels.

Sensor Pixels

The camera mounted on the SHIL is a prism-based RGB color line scan camera with three separate imagers for simultaneously capturing red, green and blue light (Fig. 2). The physical spacing of the sensor lines means that each line on the sensor has a slightly different optical angle to the target. As a result, during simultaneous exposure, each line on the sensor captures a slightly different position on the target. Simply combining these captured sensor lines into an RGB representation results in non- precise color reproduction and/or blur. To remedy this, a Spatial Compensation function is used to compensate for the different line positions. A buffer holds each line image until the third line is captured and the combined RGB data can be output. Typically, this involves introducing delay factors that stagger the exposure sequence of the three lines so that they each capture the same point on the target. To “freeze” the motion of fast moving objects, high line rates are needed.

Figure 2. Principle of a 3CCD line scan camera from the Line Scan Camera Manual_SW-2001T-CL.pdf. Note that the light travels the shortest distance to the green channel.

During the camera’s exposure time, each pixel accumulates photoelectric charges proportional to the light from the object imaged onto that pixel. At the end of the exposure time the charges in an entire row of pixels are transferred into a readout register. The readout register shifts out the pixel charges and they are amplified, corrected and digitized to produce the camera output. The readout register shifting is done while the next row of pixels is being exposed. The maximum rate at which exposure and readout can occur is called the “line rate” and is specified in kilohertz (kHz).

In the SW-2001T-CL the exposure time can be set individually for all three channels (Fig. 3). The SW-2001T-CL camera outputs 3 x 2048 pixel resolution at 19,048 lines per second, while maintaining image quality at a signal-to-noise ratio of 58 dB.

Figure 3. Sensor exposure time can be set individually for all three channels in the 'JANI Camera Setup' window in IMS.