Using the JAI CV-M10 Camera in Asynchronous Reset Mode with the IMAQ 1409

This article explains how to use the JAI CV-M10 camera in asynchronous reset mode with National Instruments’ IMAQ 1409 device to acquire clear images of moving objects. It also includes an example program that illustrates asynchronous reset with the JAI CV-M10 camera.

Progressive Scan and Asynchronous Reset

Some industrial imaging and Web inspection applications involve acquiring images of fast-moving objects. In most cases, an external trigger produced by a photocell, proximity sensor, or a similar device starts the image acquisition.
Acquired images of moving objects are often blurred. Using triggered acquisition with a progressive scan camera is one way to produce an image that is not blurred. Progressive scan cameras, such as the JAI CV-M10, eliminate the blur that results from motion because they acquire one full frame at a time. Moving images acquired using interlaced cameras often produce a motion-induced blur because they acquire the odd and even fields separately and then interlace them. Motion-induced blur occurs when the two fields are not acquired at the same time and the object is moving between the fields.

Triggering only the acquisition device while using the camera in free-running mode creates a variable delay between the time the acquisition board receives the trigger and the time the image is acquired. The delay occurs because the board has to finish acquiring the current frame before acquiring the triggered frame. Figure 1 illustrates this variable delay.



Because the delay is variable, depending on when the trigger occurs, the object does not appear at the same location on all the triggered images. Asynchronous reset cameras offer one solution to this problem. Asynchronous reset techniques help keep the motion device (a conveyor belt, for example) moving while acquiring the images on-the-fly. These techniques offer a way to introduce a vision system in an assembly line with very little modification of the environment.

When asynchronous reset cameras receive a trigger, they reset their CCD and immediately start the acquisition of a new image, which ensures that the image is always taken at the same time after trigger assertion. In this case, the objects imaged appear at the same location in the image, which simplifies the preprocessing of the image - including locating the object under inspection and specifying the regions of inspection within the image.

Figure 2 illustrates the asynchronous reset principle.

This section explains how to set up the JAI CV-M10 to run in asynchronous reset mode.
Use figures 3, 4, 5, and 6 to locate the internal and external camera switches. See Tables 1 and 2 for a summary of the camera switch configuration.

Note: These settings are valid only for revision F of the JAI CV-M10.

The JAI CV-M10 supports two asynchronous reset modes: H reset mode and H non-reset mode. A brief description of each is listed below. This document describes how to set up the camera to operate in H non-reset mode.

• H reset mode the camera resets the internal HD signal at the falling edge of the external trigger signal and then starts the exposure. The HD signal is provided to the IMAQ 1409.
• H non-reset mode the IMAQ 1409 provides the HD signal to the camera, and the exposure starts at the next HD pulse.
  

In both modes, you can control the exposure time in one of two ways: with the 7-step fixed shutter (edge preselect mode) whose speed is set by jumpers SW1-1, SW1-2, and SW1-3 on the back of the camera; or with the trigger pulse (pulse width control mode) sent to the camera.

Setting Up the JAI CV-M10
Setting up the JAI CV-M10 to run in H non-reset mode requires that you modify some of the jumpers inside the camera. Follow the guidelines below to configure the JAI CV-M10 for H non-reset mode.

Note: If you are unsure of how to modify the jumpers inside the camera, please contact JAI technical support for more information.

Make the following modifications to the internal camera switches:

• The factory default settings on the PK8189 board are set to input the HD signal to the camera. Verify that these switches are in the following positions:
  JP1: short
  JP4: short
  JP5: open
  JP7: open

Figure 3 shows the location of these switches.

Figure 3: PK8189A Board (from JAI CV-M10 Operation Manual—Rev. F)




• Open the JP3 and JP6 switches to allow TTL input of the HD signal. Figure 3 shows the location of these switches.
  
• Modify the exposure control settings for either edge preselect mode or pulse width control mode.

• In edge preselect mode, the exposure is controlled by the 7-step fixed shutter. The switches on the back of the camera determine the shutter speed.
  
  To operate the camera in edge preselect mode, short the JP13 jumper on the PK8206(BX) or PK8190(RS) board. Leave JP12 open.

• In pulse width control mode, the low period of the trigger received by the camera controls the exposure. The advantage of this mode is that you can programmatically control the exposure time.
  
  To operate the camera in pulse width control mode, short both the JP12 and JP13 switches on the PK8206(BX) or PK8190(RS) board. (This mode is supported only by revision F of the JAI CV-M10.)

Figures 4 and 5 show the location of the JP12 and JP13 switches on the PK8190A and the PK8206A, respectively.

Make the following modifications to the external camera switches:

• Modify the SW1-1, SW1-2, and SW1-3 switches to set the shutter speed when using the camera in edge preselect mode. Refer to the Shutter Speed table in your camera manual for the shutter speed that corresponds to the different switch settings.
• Set SW1-4 to OFF to select the random trigger mode.
• Set SW1-5 to ON to set the camera to noninterlace mode (progressive scan).
• Set SW1-6, SW1-7, and SW1-8 to set up the gamma, automatic gain control (AGC), and gain, respectively.

Note: It is recommended that you turn off the AGC (SW1-7) and use the manual gain instead. To use manual gain, set SW1-1 to ON.

Figure 6 shows the locations of the external camera switches. See Tables 1 and 2 for a summary of the camera switch settings.



Summary: Camera Switch Settings

Table 1: CV-M10(BX) Settings

Switch Number	Switch Settings	Mode Settings OFF                               ON
1, 2, 3	Shutter Speed	See the Shutter Speed Table in Your Camera Manual
4	Ext. Trigger Mode	Random Trigger	Normal
5	Scanning	Interlace	Noninterlace
6	Gamma	γ = 1.0	γ = 0.45
7	AGC	AGC OFF	AGC ON
8	Gain	Fixed	Rear Volume

Table 2: CV-M10(RS) Settings

Switch Number	Switch Settings	Mode Settings OFF                               ON
1, 2, 3	Shutter Speed	See the Shutter Speed Table in Your Camera Manual
4	Ext. Trigger Mode	Random Trigger	Normal
5	Scanning	Interlace	Noninterlace
6	Gamma	γ = 1.0	γ = 0.45
7	RS-232C	Switch on Rear Panel	RS-232C
8	RS-232C	Switch on Rear Panel	RS-232C

Cabling Requirements

This section discusses cabling and power supply requirements. Figure 7 shows the cable schematics for the JAI CV-M10 and the IMAQ 1409.
Note: You can use the IMAQ-A6822 breakout box to easily prototype your cable.

Tables 3, 4, 5, 6, and 7 outline the connection requirements for IMAQ 1409 loopback connections, connection from the IMAQ 1409 to the JAI CV-M10 (12-pin Hirose connector), connection from the IMAQ 1409 to the JAI CV-M10 (6-pin Hirose connector), external BNCs, and the power supply, respectively.

The IMAQ 1409 operates in external H lock mode. This mode requires that you provide the horizontal synchronization signal to the board. Since the IMAQ 1409 is configured to generate this signal, it is necessary to loop it back on the corresponding input of the IMAQ 1409.


Table 3: IMAQ 1409 Loopback Connections

Signal	68-Pin IMAQ Connector (Male) Pin Number       Signal Name		Signal Direction	68-Pin IMAQ Connector (Male) Pin Number       Signal Name
H Sync	12	CTRL(0)	→	16	HSYNC_IN +

Table 4: Connection from the 1409 to the JAI CV-M10 (12-Pin Hirose Connector)

Signal	68-Pin IMAQ Connector (Male) Pin Number          Signal Name		Signal Direction	12-Pin Hirose Connector (JAI CV-M10) (Female) Pin Number            Signal Name
H Sync	16	CTRL(0)	→	6	Ext. HD In
	26	DGND	→	5	GND
Video	68	VIDEO(0) +	←	4	VIDEO 1 Out
	60	DGND	←	3	GND

Table 5: Connection from the 1409 to the JAI CV-M10 (6-Pin Hirose Connector)

Signal	68-Pin IMAQ Connector (Male) Pin Number          Signal Name		Signal Direction	12-Pin Hirose Connector (JAI CV-M10) (Female) Pin Number          Signal Name
V Sync	15	VSYNC_IN +	←	6	WEN Out
	2	DGND	←	3	GND
Trigger Output to Camera	5	TRIG(3)	→	5	Ext. Trigger In
	41	DGND	→	3	GND

Table 6: External BNCs

Signal	68-Pin IMAQ Connector (Male) Pin Number          Signal Name		Signal Direction	External BNCs
Trigger  Input	8	TRIG(0)	←	BNC(0) (Female)
	42	DGND	←	BNC(0) GND
Strobe  (Optional)	7	TRIG(1)	→	BNC(1) (Female)
	39	DGND	→	BNC(1) GND

Table 7: Power Supply

Signal	12-Pin Hirose Connector (Power Supply) (Male) Pin Number          Signal Name		Signal Direction	12-Pin Hirose Connector (JAI CV-M10) (Female) Pin Number          Signal Name
Power  Supply	1	GND	→	1	GND
	2	+12V	→	2	+12V

Note: To preserve the quality and signal-to-noise ratio of the analog video signal, National Instruments recommends a cable length less than 10 meters (~30 feet).

Interfacing with the IMAQ 1409

This section explains how to configure your software for asynchronous reset acquisition.
Before configuring your software, make sure to remove the W1 jumper on the 1409 device.

Configuration Files

1. Copy the JAI CV-M10 30Hz Progressive Scan Ext Lock(1409).icd file and the JAI CV-M10 25Hz Progressive Scan Ext Lock(1409).icd file into the <NI-IMAQ>\Data folder. Copy the JAI CV-M10 30Hz Progressive Scan Ext Lock(1409).txt file and the JAI CV-M10 25Hz Progressive Scan Ext Lock(1409).txt file into the <NI-IMAQ>\Camera Info folder. These files are available from the linked example at the bottom of this document.

2. Launch Measurement & Automation Explorer (MAX), and follow the steps below.

1. Expand the Devices and Interfaces branch of the tree view.
2. Expand the IMAQ PCI/PXI-1409 branch of the tree view.
3. Right-click Channel 0.
4. Select Camera>>JAI>>JAI CV-M10 30Hz Progressive Scan Ext Lock
       if you have an EIA (RS170) camera, or select Camera>>JAI>>JAI
       CV-M10 25Hz ProgressiveScan Ext Lock if you have a CCIR camera.
5. Click Save and exit Measurement & Automation Explorer.

Note: Because asynchronous reset mode requires that you provide the trigger signal and the synchronization signals to the camera (external lock mode), image acquisition within Measurement & Automation Explorer is not possible.

In order to acquire images in asynchronous reset mode, both the IMAQ 1409 and the camera must receive the trigger. The input trigger connects to the IMAQ device, which generates the trigger signal sent to the camera. If you set up the camera to work in pulse width control mode, this setup allows you to specify the length of the trigger pulse in order to set the exposure time. (In pulse width control mode, specifying the length of the trigger pulse sent to the camera sets the JAI CV-M10 exposure time.)

Because the IMAQ 1409 generates the trigger sent to the camera, you can also use the camera without providing an external trigger input to the board. Specifying the width and frequency of the pulse signal generated by the board determines the acquisition rate and exposure time (internal trigger mode).

The IMAQ device generates the horizontal (HD) synchronization signal the camera needs. The HD signal is generated on one of the control lines of the IMAQ 1409 (Control Line 0), as specified in the configuration file.

The camera outputs the VD signal (WEN), which is connected to the corresponding input of the IMAQ 1409.

When acquiring images of moving objects, decreasing the exposure time (increasing the shutter speed) ensures that the resulting images are not blurred. Decreasing the exposure time decreases the amount of light that the CCD sensor can integrate. To compensate for the short exposure time and still get a well-contrasted image, provide a more intense lighting or use a strobe light at the time of the image acquisition. The strobe light can also control the exposure time, in which case the sensor exposure time can be set to the maximum.

Because the acquisition device is capable of outputting a signal that corresponds to the start of a frame (TRIG 1), it can be useful to illuminate the object by firing a strobe light when the frame is acquired.

Computing Exposure Time

This section explains how to compute the correct exposure time for your application.

To compute the exposure time needed for your application, you need to know the following parameters:

• Horizontal resolution of your camera (example: 640 pixels)
• Horizontal field of view (example: 100 mm)
• Speed of the moving object (example: 150 mm/s)
• Acceptable blur—defines the maximum blur that is acceptable in the image (example: < 1 pixel). The acceptable blur corresponds to the number of pixels that the object moves during the exposure time.
  

The shutter speed needed for the application corresponds to the time needed for the object to move the number of pixels specified by the blur. Figure 8 demonstrates how to compute exposure time.

Figure 8: Computing Exposure Time


In the example, the Exposure Time needs to be less than: 1 x 100 / (640 x 150) = 0.00104 s = 1.04 ms

Example Program

This section includes a link to a sample program that demonstrates an asynchronous reset acquisition.

This example below shows how to control the camera's shutter speed and how to perform an asynchronous reset acquisition with an IMAQ 1409 and a JAI CV-M10 camera. You can either provide an external trigger to trigger the acquisition, or the IMAQ device can generate a signal to trigger the acquisition (internal trigger). The internal trigger mode allows you to test the example without having to provide an external trigger signal to the board.

The following example (JAI CV-M10 Advanced Asynchronous Reset Example.vi) is implemented using a state machine. In the first frame, IMAQ Create allocates the memory for the images.

1. In the Start state, shown in Figure 9 below, IMAQ Init is called to initialize the board. Then, the subVI JAI CV-M10 Asynchronous Reset Manager generates all the signals. Inside this subVI, IMAQ Generate Pulse is called twice to create the shutter pulse, which control the camera's shutter and asynchronous reset, and to output a strobe signal on one of the output lines.

2. Next, IMAQ Configure List configures the buffer list, which contains one buffer. IMAQ Start starts the acquisition.

3. In the Acquire state, shown in Figure 10 below, IMAQ Copy provides a copy of the image currently being acquired. IMAQ WindDraw displays this image in an image window.



4. The Stop state, shown in Figure 11 below, calls JAI CV-M10 Asynchronous Reset Manager to stop generating the pulses. IMAQ Close.vi is called to shut down the acquisition.




To download the source code for this example, refer to Example: Using the JAI CV-M10 Camera in Asynchronous Reset Mode with the IMAQ 1409.

See Also:
Example: Using the JAI CV-M10 Camera in Asynchronous Reset Mode with the IMAQ 1409

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