Sch"after+Kirchhoff SK1024U3PD Manual de usuario descargar pdf (Pagina 3)

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11-2014 E

Controlling continuous measurement

processes using a GigE line scan camera

Buffer 1 / Processing

Buffer 2 / Acquisition

done+1 done+1

Special functions have been added to the SDK of the

SK91GigE-WIN software from Schäfter+Kirchhoff that

enable the efficient control and manipulation of

continuous measurement applications

The ability to customize the memory allocation

for the Gigabit Ethernet line scan cameras can

be used for the continuous collection of the

camera data into a User Buffer Queue. This

speeds up operations as data must not be

copied back and forth, freeing up the CPU for

other activities, such as data evaluation or for

controlling external devices. The writing of data

into the User Buffer Queue is cyclical. Up to

256 buffer suballocations can be set according

to the demands of the application. The minimum

permitted size is exactly one line scan.

The data in a previously filled buffer can be

manipulated or evaluated while the camera is

writing data into the next buffer. The user

receives an event signal and the address of the

buffer in the queue that was written to last. For

the successful continuous evaluation of camera

data in the two buffers, without loss of data, the

evaluation of the first buffer must be completed

after the illumination of n lines, at the latest.

n 2n 3n 4n

Line clock

Acquisition 1

Acquisition 2

Processing 1

Processing 2

Image Counter

done = 0

+1 +1 +1 +1

When more than two buffers are allocated and

there is a time delay caused by the manipulation

of data from one buffer then the time delay can

be recovered by the rapid utilization of the data

in the next or subsequent buffers.

Thus, there are effectively no time limits or

restrictions when performing continuous

acquisition and data manipulation tasks.

The sequential method of acquisition of large

images with a GigE line scan camera

Camera

SK4096GPD-L

DMA-Ringspeicher

Auswerten

Erfassung

DMA initialisieren

scans = n, done = 0

0 n 2n Zeile

Initialization

Continuous Grab

Processing

User Ring Buffer

lines= n, done= 0

0 n 2n lines

Management of the GigE line scan camera memory by the user

The SDK in the SK91GigE-WIN software package provides library functions that allow the user to

allocate memory areas for the image acquisition. The GigE line scan camera then writes directly

into these predefined memory areas, obviating any copying of the data from one area to another.

The writing of camera data into memory can be performed either in a cyclical manner or after all

of the buffers have been filled. This latter method is particularly useful for a sequence of images,

up to a maximum of 256 individual images.

The image sequence method allows the acquisition of extremely large images, circumventing the

internal restriction of 64 MB and 16383 lines per image. The user defines the appropriate memory

size in virtual memory for the desired size of image, which is then divided in up to 256 component

parts. A sequence series is programmed by simply pointing to this buffer and the acquisition of

the sequence images then results in the image data being collected up to the desired size.

image dimension: 4096 x 32768 Pixel

image size: 128 MByte

number of buffers: 8

buffer size : 16 MByte

Sequence acquired

Start

Image

Processing

Thresholding

Thresholding is a special capability of cameras with a Gigabit Ethernet

interface that offers an effective alternative to gray shade evalution

and enumeration, assuming there is sufficient contrast available in the

image. The development of thresholding is the successful outcome

of an initiative to perform data reduction without information loss

when monitoring changes in signal intensity. The thresholding process

generates a binary signal, with data values below the threshold yielding

0 and those above yielding 1. Only the pixel addresses of the location

and value (from high o low or low o high) of the threshold transition

are transmitted with a line-end character (Runlength Encoding).

Thresholding is particularly suitable for measuring widths or edge

positions, as the substantial complexities inherent in edge position

determination have been reduced to simply masking the required pixel

addresses.

Other thresholding features and possibilities include:

• Noise suppression filtering • Subpixel resolutions

Data format: 16-bit integer without a starting character

Bit 0...13: pixel address of the signal transition

Bit 14: 0 = transition from high o low

1 = transition from low o high

Bit 15: 1 = line end character

Software SK91GigE-WIN

Example program for continuous Thresholding

GigE SK7500GTF-XB

Window Function (ROI)

The window function defines a

freely programmable window (re-

gion of interest, ROI) on the line

sensor. Only the pixel information

within this window reaches the

FIFO and, therefore, only these

ranges are then illuminated. This

window control function reduces

the data volume and the data pro-

cessing effort for both line and

picture acquisitions.

The video data of the ROI is written

left-bounded into the image buffer

and the oscilloscope display in the

SkLineScan program adjusts the ROI to the actual pixel address of the

signal window. One restriction of the memory allocation is that the ROI

length must be divisible by 8.

buffer 0

buffer 1

buffer 2

buffer 3

buffer 4

buffer 5

buffer 6

buffer 7

Image memory 128 MByte

Control dialog for setting a region of interest

1 2 3 4 5 6 7 8 ... 23 24

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