• FireWire devices allow an operating voltage from 8 to 30 VDC. The current consumption may be 1.5 A. USB devices are much less flexible. The operating voltage has to be 4.7 VDC while the max current is 0.5 A.

• FireWire devices hold their addresses after the system has been restarted while those of USB devices are reassigned. This is especially obstructive when using more than one camera.

• There are more than 50 internationally standardized protocols for FireWire devices. In the case of cameras transferring their image data without compression or an audio channel the protocol is DCAM/IIDC. USB cameras, in comparison, only come with proprietary protocols.

The cause of these differences lie in their history. USB is the successor of the RS232 interface. FireWire is a user friendly variation of busses such as SCSI, PCI, etc. When only using one camera, the differences are not usually important. But, for more demanding applications the possibilities of USB are very limited.

White Balance

Use this parameter to vary the degree of red and blue in the image to achieve a lifelike color representation. The values can be controlled manually or automatically. The automatic white balance feature offers two operation modes:

Auto: the balancing algorithms affects the video stream continuously.
One push triggers only one pass of the adaptation procedure.

Simple multimedia cameras only provide one white balance parameter. Thus, increasing the degree of red leads to a decrease of blue and vice versa. High quality cameras offer two parameters and thus allow to adjust independently the degree of red and blue:

(The End.)

Saturation

Use this parameter to adjust the color‘s saturation from monochrome to high color values:

Hue

Use this parameter to shift color values. Nevertheless, the relation between the colors remains:

(To be continued…)

Sharpness

You may use this mechanism to enhance blurred images. Overdoing its application leads, however, to distortions:

Gamma

Gamma increases or decreases the middle graylevels. In other words, you compensate the non-linear behavior of picture tubes:

(To be continued…)

Gain (Contrast)

Gain determines the amplification of the CCD’s output signal. This parameter may be adjusted manually or automatically. The amplification increases the contrast. A high gain, however, leads to noisy images:

Offset (Brightness)

The offset is added to the CCD‘s output signal. This parameter may be adjusted manually or automatically. Therefore, adding the offset increases all graylevels. Thus, the image looks brighter:

Auto Exposure und Exposure Reference

Auto Exposure determines whether the adjustment of the exposure time and the gain (see Shutter and Gain) is to be adjusted manually or automatically. You can use the parameter Exposure Reference to control the automatic operation. It compares the mean graylevel of the current image with the Exposure Reference. If these values are different, the exposure time as well as the gain are varied accordingly.

(To be continued…)

Introduction

The quality of an image is determined by many things: Illumination, lens and camera parameters. In the following text, we are going to take a look at how to set camera parameters for optimal image quality.

Shutter (Exposure Time)

The shutter determines the CCD‘s exposure time. It may be adjusted manually or automatically. The three first sample images show a key ring (the LED is initially off) with correct exposure time, one which is too short and another which is too long:

Switching on the LED, the image is overexposed in such a way that it only shows a big, white spot. The LED is correctly represented, if we decrease the exposure time. There is, however, a vertical line which disturbs the image. This is a typical CCD problem and is known as “smear”. To avoid this, we close the diaphragm and increase the exposure time:

(To be continued…)

Bremen, (July 10, 2008) - The Imaging Source - a multi-national manufacturer of industrial cameras - has just announced a new series of cost effective LED lighting modules, which seamlessly integrate with The Imaging Source USB, FireWire and GigE camera.

• Very bright LEDs
• Direct connection to the camera
• All parameters can be set via the shipped software, IC Capture and IC Imaging Control or by custom built software
• Compatible with The Imaging Source USB CCD cameras
• Compatible with The Imaging Source FireWire cameras
• Compatible with The Imaging Source GigE cameras

All cameras manufactured by The Imaging Source ship with IC Capture and IC Imaging Control. The former is an end-user application, with which it is possible to set all cameras parameters, save singular images and image sequences and display live video streams. IC Imaging Control is an SDK, which consists of a .NET component, ActiveX control and C++ class library for Windows XP and Windows Vista.

Please do not hesitate to contact us for more information.

For more details, please take a look at the products’ web site:

• FireWire and USB 2.0 Cameras

Please do not hesitate to contact us, if you would like a quotation for any of the above cameras, or indeed, would like to talk to us about any matter related to image processing or machine vision.

Typical mistakes

The bewildering variety of optical components, as well as “historical legacy issues” originating from the world of picture tubes, lead to different mistakes when selecting these components. In the following you will find the three most basic misunderstandings:

Incorrect: The lens format and the camera format have to be identical.
Correct: The lens format should preferably be larger than the CCD format since optical flaws appear at the rim of the lens.

Incorrect: If the lens format is larger than the CCD format it has to have a larger/smaller focal length.
Correct: The focal length exclusively depends on the CCD format, the working distance and the
object size.

Incorrect: Extension rings increase/decrease the depth of field.
Correct: Extension rings decrease the minimal working distance.

Fixing blurred images

There are two basic reasons for blurred images:
• The lens quality is lower than the quality of modern CCD chips. The Pentax M Series recommended in this white paper has been especially designed to work with modern CCD chips. Wide-angle lenses, however, have weaknesses due to their construction.
• The lens setup is incorrectly arranged. This usually leads to extremely blurred images. In such cases please proceed as follows:

C Mount lens / CS Mount camera:
Please check whether a 5 mm extension ring has been screwed between the camera and the lens. The Imaging Source exclusively manufactures CS mount cameras. Each of the cameras is shipped with a 5 mm extension ring.

CS Mount lens / CS Mount camera:
If you have accidentally screwed a 5 mm extension ring between the camera and the lens, you will only be able to focus on close objects.

CS Mount lens / C Mount camera:
This configuration only allows to focus on very close objects. If this is not your aim, then you have to use a CS mount camera. The Imaging Source exclusively manufactures CS mount cameras.

“Sticking” extension rings:
If you previously have used the camera or the lens with a thin extension ring, it often “sticks” to either of them. In such cases you are not able to focus to infinity for no apparent reason.

(The End.)