Balluff - BVS CA-MLC / BVS CA-IGC / mvBlueFOX Technical Documentation
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The CCD sensor is a highly programmable imaging module which will, for example, enable the following type of applications
Industrial applications:
Scientific applications:
The process of getting an image from the CCD sensor can be separated into three different phases.
When coming out of reset or ready with the last readout the CCD controller is waiting for a Trigger signal.
The following trigger modes are available:
Mode | Description |
Continuous | Free running, no external trigger signal needed. |
OnDemand | Image acquisition triggered by command (software trigger). |
OnLowLevel | As long as trigger signal is Low camera acquires images with own timing. |
OnHighLevel | As long as trigger signal is High camera acquires images with own timing. |
OnFallingEdge | Each falling edge of trigger signal acquires one image. |
OnRisingEdge | Each rising edge of trigger signal acquires one image. |
OnHighExpose | Each rising edge of trigger signal acquires one image, exposure time corresponds to pulse width. |
TriggerSource Impact Acquire | TriggerSource GenICam(BCX) |
GP-IN0 | Line4 |
GP-IN1 | Line5 |
After an active trigger, the exposure phase starts with a maximum jitter of ttrig. If flash illumination is enabled in software the flash output will be activated exactly while the sensor chip is integrating light. Exposure time is adjustable by software in increments of treadline.
When exposure is finished, the image is transferred to hidden storage cells on the CCD. Image data is then shifted out line-by-line and transferred to memory. Shifting out non active lines takes tvshift, while shifting out active lines will consume treadline. The number of active pixels per line will not have any impact on readout speed.
Name | Description | Pixel clock | |
20 MHz | 40 MHz | ||
ttrig | Time from trigger (internal or external) to exposure start | 10.2us | 5.1us |
ttrans | Image transfer time (move image to readout cells in CCD) | 96us | 48us |
treadline | time needed to readout a line | 96us | 48us |
tvshift | time needed to shift unused lines away | 10.2us | 5.1us |
twait | minimal time to next trigger | 316us | 158us |
texposure | Exposure time | 1us..10s | 1us..10s |
treadout | Image readout time (move image from readout cells to memory | treadout = (ActiveLines * treadline) + (1248 - ActiveLines) * tvshift + treadline |
To calculate the maximum frames per second (FPSmax) you will need following formula (Expose mode: No overlap):
FPS_max = 1 -------------------------------------------------- t_trig + t_readout + t_exposure + t_trans + t_wait
(Expose mode: Overlapped):
t_trig + t_readout + t_trans + t_wait < t_exposure: FPS_max = 1 --------------- t_exposure t_trig + t_readout + t_trans + t_wait > t_exposure: FPS_max = 1 ------------------------------------- t_trig + t_readout + t_trans + t_wait
Now, when we insert the values using exposure time of, for example, 8000 us, 1200 lines and 40MHz pixel clock (Expose mode: No overlap):
FPS_max = 1 --------------------------------------------------------------------------------------- 5.1 us + ((1200 * 48 us) + ((1248 - 1200) * 5.1 us) + 48 us) + 8000 us + 48 us + 158 us = 0.000015127700483632586 1 / us = 15.1
Reprogramming the CCD Controller will happen when the following changes occur
Reprogram time consists of two phases
So for example when reprogramming the capture window you will need (average values)
tregprog = change_window + init_ccd
tregprog = 5ms + 4.5ms
tregprog = 9.5ms
Device Structure
These zone definitions apply to both the color and gray scale version of the sensor.
The CCD signal is processed with an analog front-end and digitized by an 12 bit analog-to-digital converter (ADC). The analog front-end contains a programmable gain amplifier which is variable from 0db (gain=0) to 30dB (gain=255).
The 8 most significant bits of the ADC are captured to the frame buffer. This will give the following transfer function (based on the 8 bit digital code): Digital_code [lsb] = ccd_signal[V] * 256[lsb/V] * exp(gain[bB]/20) lsb : least significant bit (smallest digital code change)