How do industrial cameras solve frame loss? Let's take a look

In the industrial camera industry, the reason why the phenomenon of frame loss of industrial cameras occurs is actually the blockage of the data channel, which cannot be processed by technology, so when the new image is collected, the previous image may be forced to be discarded, or the new image is forced to be discarded.

01, lost frame performance

1. In the preview mode of industrial cameras, images cannot be transmitted at full frame speed

2. In trigger photo mode, the number of images transmitted by the camera is less than the trigger times (the trigger frequency should be less than the frame rate).

3. The number of images processed by image processing software is less than expected

02. Possible causes of frame loss

The problem of frame loss in industrial cameras is a common problem in industrial cameras, and the reason is not much related to the transmission interface of the camera, mainly related to the hardware of industrial cameras and poorly designed drivers, which has a very uncertain effect on machine vision detection.

Industrial camera frame loss 3 main reasons to explain:

1. Industrial camera hardware design

The industrial camera converts the image from an optical signal into an ordered electrical signal, in which the image sensor transmits the image to the USB chip on the camera, and the USB is transmitted to the computer side. If the computer side system is busy at a certain time, the image is not received in time, and the subsequent image is transmitted, resulting in the loss of the part of the image that is not received.

2. Industrial vision software application part

Visual software includes hardware drivers and image processing, the memory space allocated for image computing, there is no buffer mechanism, you can increase the image cache to increase the buffer time, and the design of multi-threading will also affect the processing speed.

Let the program have enough space to process, in the case of operation, the overall processing speed of the CPU is slower than the image coming in, if the cache is not enough, the efficiency of receiving is too low, and the industrial camera does not have enough cache, it will constitute the phenomenon of lost frames.

But this is a system drop, not an industrial camera drop. In this case, whether it is an industrial camera with the 1394 interface, or a USB interface, or a GigE interface, any interface industrial camera will get the same effect.

3. Hardware PC system

The PC part mainly depends on the hardware driver, the important thing is the power of the driver and how many kernel way the system has threads in the partition of the CPU time, the received power is not good, industrial cameras do not have a good buffer memory, often cause frame loss phenomenon.

Frame loss due to hardware reasons may be caused by insufficient data bandwidth, such as expansion network cards or USB3.0 cards may cause problems.

The camera network cable does not meet the transmission rate requirements;

The PCIe slot is faulty and cannot reach the standard rate. For example, a PCIe slot may be expanded from the primary PCIe slot and share the same bandwidth with the primary PCIe slot.

Or the data transmission rate of the camera's full-frame image is higher than that of a single network port /USB3.0 port.

The data transfer rate of all the channels of the NIC /USB3.0 exceeds that of the PCIe slot.

03, how to solve the frame loss problem

To solve this problem, designers need to precisely design every part of the drive and data transfer of industrial camera hardware, with three places blocking image data:

1. Part of an industrial camera

The image sensor transmits the image to the USB chip on the camera, transfers the USB to the PC, and if the PC system is busy processing the received image, and the image sensor continues to transmit new image data, the industrial camera must have an adequate memory buffer, and vice versa.

2. Visualize the software program part

The visualization software has a buffering mechanism for waiting on the computed image space in order to increase the buffering of the image to obtain buffering time, so that the operation of the program can be processed, but if the operation is stable, the overall processing speed of the CPU is faster.

In machine vision systems, the frame rate of industrial cameras is often large, and the cache of industrial cameras is also limited, mainly for the scheduling system to play a temporary busy processing auxiliary function.

The speed of machine vision software is slower than the speed of industrial camera images coming in, and a long time will lead to the saturation overflow loss of software cache, so whether it is USB interface and gige interface, there will be frame loss phenomenon, so optimizing the processing speed of machine vision software is also very important.

3. Hardware PC system

This section is biased towards PC hardware drivers and has nothing to do with visualization software programs.

The key to PC reception is the efficiency of the driver, how many threads are in CPU time in kernel mode, the reception efficiency is not high, and the industrial camera does not have enough buffer memory will cause frame loss.

Industrial cameras have very fast frame rates, and in fact, as long as there is enough capacity to adjust the "temporary" busyness of the system, industrial camera caches will not scale up as much as PC programs. USB industrial cameras will discard frames, only in one case, the machine vision software is slower than the industrial camera image, the software cache is full, can not store new images.

But this is system data, not industrial camera data. In this case, regardless of the industrial camera using the 1394 interface, USB interface or GigE interface, the industrial camera with any interface will get the same result.

Therefore, when buying an industrial camera, it is necessary to examine its parameters in detail and select the actual requirements of the project to avoid the occurrence of frame drop events.