7.5 acA-750 Acquisition Control Differences
7.5.2 Field Output Modes
On acA750 cameras, four "field output modes" are available: field 0, field 1, concatenated new fields, and deinterlaced new fields.
Field 0 Output Mode: Each time the camera receives a frame trigger signal, it acquires, reads out, and transmits a frame using the field 0 scheme described in Section 7.5.1 on page 103. Because pairs of rows are combined, the transmitted image is commonly referred to as "half height", i.e., the number of vertical pixels in the transmitted image will be one half of the number of physical pixels in the sensor.
In Field 0 output mode, the pixel data from field 0 is considered to be a frame. Each time the camera receives a frame trigger signal, it will acquire field 0 and will transmit the field 0 pixel data as a frame.
Field 1 Output Mode: Each time the camera receives a frame trigger signal, it acquires, reads out, and transmits a frame using the field 1 scheme described in Section 7.5.1 on page 103. Because pairs of rows are combined, the transmitted image is commonly referred to as "half height", i.e., the number of vertical pixels in the transmitted image will be one half of the number of physical pixels in the sensor.
In Field 1 output mode, the pixel data from field 1 is considered to be a frame. Each time the camera receives a frame trigger signal, it will acquire field 1 and will transmit the field 1 pixel data as a frame.
Frame Row 0 + Row 1 Row 2 + Row 3 Row 4 + Row 5 Row 6 + Row 7 Row 8 + Row 9
...
Fig. 52: Field 0 Output Mode
Frame Row 1 + Row 2 Row 3 + Row 4 Row 5 + Row 6 Row 7 + Row 8 Row 9 + Row 10
...
Image Acquisition Control AW00089316000
Concatenated New Fields Output Mode: Each time the camera receives a frame trigger signal it acquires two fields, combines them into a single frame, and transmits the frame.
After receiving a frame trigger signal, the camera first acquires and reads out an image using the field 0 scheme and it places this image into the camera’s memory. The camera then automatically acquires and reads out a second image using the field 1 scheme. The data from the two acquired images is concatenated as shown in Figure 54, and the concatenated image data is transmitted as a single frame.
In concatenated new fields output mode, the concatenated pixel data from field 0 plus field 1 is considered to be a frame. It is not necessary to issue a separate frame trigger signal to acquire each field. When a frame trigger signal is issued to the camera, it will first acquire field 0 and will then automatically acquire field 1 without the need for a second frame trigger signal. When acquiring each field, the camera will use the full exposure time indicated by the camera’s exposure time parameter setting.
If a camera is operating in concatenated new fields output mode and is set, for example, for 30 frames per second, it will acquire 60 fields per second. Since two fields are combined to produce one frame, the camera will end up transmitting 30 frames per second. When set for a 30 frames per second rate, the camera will begin acquiring field 0 each time it receives a frame trigger signal and will automatically begin acquiring field one 1/60th of a second later.
The main advantages of using the concatenated new fields output mode are that it provides pixel data for a "full height" image and that it provides much more image information about a given scene. The disadvantages of using the concatenated new fields output mode is that the image data must be deinterlaced in order to use it effectively and that, if the object being imaged is moving, there can be significant temporal distortion in the transmitted frame.
Frame Field 0 Pixel Data Field 1 Pixel Data Row 0 + Row 1 Row 2 + Row 3 Row 4 + Row 5 Row 6 + Row 7 Row 8 + Row 9
...
Row 1 + Row 2 Row 3 + Row 4 Row 5 + Row 6 Row 7 + Row 8 Row 9 + Row 10...
acquires two fields, combines them into a single frame, and transmits the frame.
After receiving a frame trigger signal, the camera first acquires and reads out an image using the field 0 scheme and it places this image into the camera’s memory. The camera then acquires and reads out a second image using the field 1 scheme. The data from the two acquired images is deinterlaced as shown in Figure 55, and the deinterlaced image data is transmitted as a single frame.
In deinterlaced new fields output mode, the deinterlaced pixel data from field 0 plus field 1 is considered to be a frame. It is not necessary to issue a separate frame trigger signal to acquire each field. When a frame trigger signal is issued to the camera, it will first acquire field 0 and will then automatically acquire field 1 without the need for a second frame trigger signal. When acquiring each field, the camera will use the full exposure time indicated by the camera’s exposure time parameter setting.
If a camera is operating in deinterlaced new fields output mode and is set, for example, for 30 frames per second, it will acquire 60 fields per second. Since two fields are combined to produce one frame, the camera will end up transmitting 30 frames per second. When set for a 30 frames per second rate, the camera will begin acquiring field 0 each time it receives a frame trigger signal and will automatically begin acquiring field one 1/60th of a second later.
The main advantages of using the deinterlaced new fields output mode are that it provides pixel data for a "full height" image and that it provides much more image information about a given scene. The disadvantage of using the deinterlaced new fields output mode is that, if the object being imaged is moving, there can be significant temporal distortion in the transmitted frame.
Frame Field 0 Pixel Data Field 1 Pixel Data Row 0 + Row 1 Row 1 + Row 2 Row 2 + Row 3 Row 3 + Row 4 Row 4 + Row 5
...
Row 6 + Row 7 Row 7 + Row 8 Row 8 + Row 9 Row 9 + Row 10 Row 5 + Row 6...
Image Acquisition Control AW00089316000