Videre Design STH-DCSG/-C, STH-DCSG User Manual

STH-DCSG/-C Stereo Head

User’s Manual

April, 2005

2005 Videre Design

Table of Contents

Introduction.........................................................................................4

1.1 Characteristics ...............................................................................4

1.2 Global Shutter................................................................................5

2 Quick Start...........................................................................................6

3 Hardware Overview............................................................................8

3.1 Hardware Schematic......................................................................8

3.2 Frame Formats and Rates ..............................................................8

3.3 50 Hz Operation ............................................................................9

3.4 Multiple Devices..........................................................................10

4 Installing the 1394 Host Card and Capture Software....................11

4.1 1394 Hardware and Drivers.........................................................11

4.1.1 MS Windows Hardware Installation ...................................11

4.1.2 Linux Hardware and Driver Installation..............................11

4.2 STH-DCSG Software..................................................................11

5 IEEE 1394 Interface..........................................................................13

5.1 IEEE 1394 Cable.........................................................................13

5.2 IEEE 1394 Host Interface............................................................13

5.3 Supplying Power .........................................................................13

6 Lenses .................................................................................................15

6.1 Locking Lenses............................................................................15

6.2 C and CS-Mount Lenses..............................................................15

6.3 Changing Lenses..........................................................................15

6.4 Cleaning the Imagers...................................................................15

6.5 Imager Size..................................................................................15

6.6 F Number.....................................................................................15

6.7 Focal Length................................................................................16

6.8 Range Resolution.........................................................................16

6.9 Field of View...............................................................................16

7 User Controls.....................................................................................18

7.1 Color............................................................................................18

7.2 Gamma Correction.......................................................................18

7.3 Video Digitization Parameters....................................................19

7.4 Subsampling................................................................................ 20

7.5 Frame Rates ................................................................................ 20

7.6 Firmware Parameters..................................................................20

8 Interface Software API..................................................................... 22

9 Physical Dimensions and Mounting Diagram................................23

10 Technical Specifications ............................................................... 24

10.1 Specifications.............................................................................. 24

10.2 Imager Response - Color ............................................................ 25

10.3 Imager Response – Monochrome ............................................... 25

10.4 Filter Transmittance....................................................................26

11 Technical Support.........................................................................27

Figures and Tables

Figure 1-1 Sequence taken by the MT9V022.............................................. 5

Figure 2-1 SVS main program window....................................................... 6

Figure 3-1. Physical layout of the STH-DCSG/-C stereo head...................8

Figure 3-2 Schematic of the STH-DCSG/-C electronics............................. 9

Figure 4-1 Host PC low-level software structure......................................11

Figure 5-1 External power supply connections. ......................................14

Figure 6-1 Range resolution in mm as a function of distance...................16

Figure 7-1 Video Parameters dialog.......................................................... 18

Figure 7-2 Frame size and sampling controls............................................ 19

Figure 7-3 Firmware parameters dialog. ................................................... 21

Table 1 Frame formats and sizes for the STH-DCSG/-C............................9

Table 2 Bus bandwidth requirements at different frame rates................... 10

Table 3 Horizontal and vertical field of view for different lens focal lengths.

............................................................................................................ 17

Table 4 Subsampling modes and frame rates for the STH-DCSG............20

1 Introduction

The STH-DCSG is a compact, low-power digital stereo head with an IEEE 1394 digital interface. It consists of two 640x480 (VGA), progressive scan CMOS imagers mounted in a rigid body, and a 1394 peripheral interface module, joined in an integral unit.

The CMOS imagers have a global shutter – all pixels are exposed at exactly the same time (the “G” in DCSG). This makes the STH-DCSG suitable for environments with fast movement, such as on an outdoor vehicle.

The CMOS imagers are MT9V022 sensors from Micron Semiconductor.. They are 1/3” format, with a resolution of 640 H by 480 V pixels, and come in either monochrome (STH-DCSG) or colorized (STH-DCSG-C) versions. These imagers have excellent dynamic range, sensitivity, anti-blooming, and noise characteristics. They are fully controllable via the 1394 interface: the user can set exposure, gain, decimation, etc. They have better noise, sensitivity, and crosstalk characteristics than the previous sensors.

The STH-DCSG/-C uses standard C/CS-mount lenses for user-changeable optics. Wide-angle to telephoto options are available, depending on the application.

The variable baseline version of the STH-DCSG/-C uses the same imagers, but has a separate IEEE 1394 interface for each imager. It has similar characteristics to the STH-DCSG/-C; please see the STH-DCSG-VAR/-C manual for more information.

SRI’s Small Vision System (SVS) software has an interface to the STHDCSG/-C, and is included with each stereo head. You can simply and automatically calibrate the stereo head, perform stereo correlation, and view the results as a 3D point set. The SVS software includes software drivers for the STH-DCSG/-C for MS Windows 98SE/ME/2000/XP, and for Linux

2.4.and 2.6 kernels.

1.1 Characteristics

• Micron MT9V022 CMOS imagers

Global shutter Simultaneous exposure and readout 640x480 maximum image size 1/3” format High sensitivity, low noise Low pixel cross-talk

• Fully synchronized stereo – left and right pixels are

interleaved in the video stream

• Monochrome or Bayer Color

• High frame rates – 30 Hz for 640x480

• On-chip binning (monochrome only) and decimation –

full frame 640x480 and 320x240 modes

• Electronic zoom mode – center 320x240 subwindow

• Extensive control of video parameters

Automatic or manual control of exposure and gain Automatic control of black level Manual control of color balance

• 50 Hz mode – reduces indoor light interference in

countries with 50 Hz electrical line frequency

• Stereo calibration information can be stored on the

device, and downloaded automatically to the PC

• IEEE 1394 interface to standard PC hardware – carries

power and commands to device, data to PC

• Standard C/CS mount lenses, interchangeable –

standard focal lengths 2.8, 4.0, and 8.0 mm

• Fixed 9 cm baseline

• Anodized aluminum alloy chassis, high rigidity

1.2 Global Shutter

The STH-DCSG has a global shutter (the “G” designation in STH-DCSG). Almost all other CMOS imagers have a rolling shutter. With rolling shutter, each row of pixels is exposed just before it is read out. So each row is exposed at a different time from other rows. This leads to motion blur – a skewing of moving objects from top to bottom.

Global shutter, on the other hand, exposes every pixel at the same time. The charge on exposed pixels is then transferred to a set of storage bins, and read out to give an image. Because the pixels are exposed at the same time, there is no motion blur. With its high sensitivity, the STH-DCSG allows for very short exposure times, even under moderate lighting conditions. So it is appropriate for high-motion applications, such as outdoor robotics, motion capture, etc. Figure 1-1 shows an example of motion capture using the device. Notice the stop-action motion of the model plane.

Although there are a small number of global-shutter CMOS imagers, most of them are sequential, that is, the pixels are exposed, then read out. The pixels cannot be exposed again until readout finishes. With sequential readout, either the framerate or the maximum exposure is limited. The STH-DCSG has simultaneous exposure and readout, that is, while the pixels are being exposed, the previous image is being read out.

Figure 1-1 Sequence taken by the MT9V022. Exposure 0.7 ms, 30 Hz, 640x480 video stream. Sequence shows about every 4

frame.

2 Quick Start

The STH-DCSG/-C normally comes assembled with the lenses mounted. If you need to change the lenses, or if you are supplying your own, please see Section 6.1.

To set up and test the STH-DCSG/-C, you will need the following:

1. Pair of C-mount lenses, for 1/2” or larger imager (normally

included and mounted with the STH-DCSG/-C kit).

2. Host computer with an IEEE 1394 PCI (desktop) or PCMCIA

(laptop) card, OHCI compliant; or a built-in IEEE 1394 port.

3. IEEE 1394 6-pin to 6-pin cable.

4. Small Vision System installed on the host computer.

Install the IEEE 1394 host card, if necessary, according to the directions in Section 4.1. Install the Small Vision System software (see Section 4.2).

If the lenses are not mounted on the device, follow the directions in Section

6.1 for installing them. Plug one end of the IEEE 1394 6-pin video cable into the 1394 jack on the

back of the STH-DCSG/-C, and the other into an IEEE 1394 port on the host PC.

Note: The STH-DCSG draws power from the IEEE 1394 bus. PCI cards, or built-in ports for desktop machines, normally supply this power. For PCMCIA cards (PC Cards), and laptops with a built-in port, no power is available. In this case, external power must be supplied – see Section 5.3.

The PC operating system will normally recognize the STH-DCSG, and install the correct system drivers. Please see the Videre support web pages (www.videredesign.com/support.htm

) for specific information about installation for your OS. At this point, you should check to see that the STH-DCSG has been recognized by the system.

Start the SVS main program, smallv(.exe) or smallvcal(.exe), on the host computer. You should see a screen as in Figure 2-1. The message window should indicate that the “DCS Digital Stereo Interface” is present. If not, go back to software installation (Section 4.2), and follow the instructions for configuring the correct capture library.

Pull down the Input chooser, and select the Video option. If everything has been set up correctly, the SVS interface will recognize and configure the stereo head, and a success message will appear in the info text window. If not, the Input chooser will go back to None, and an error message will appear in the info window. Please see Section 4 for troubleshooting.

To view stereo video, press the Continuous button. Left and right images should appear in the application windows. If the message “Image timed out” appears, then there is a problem with the IEEE 1394 drivers; please see Section 4. If the images are too light or too dark, you can open the manual iris of the cameras, or change the exposure and gain settings

Figure 2-1 SVS main program window.

(Section 7.3). Images can be saved using the File menu. A more complete description of the video capture program is in Section 7.

The SVS programs are described in the SVS User’s Manual, and the SVS Calibration Addendum, documentation that comes with that software. It is helpful to review Section 7 in conjunction with the SVS documentation.

3 Hardware Overview

Figure 3-1 shows the hardware configuration of the STH-DCSG/-C. The imager module has a milled aluminum alloy frame that rigidly holds

two megapixel imagers, separated by a fixed distance of 9 cm. Lens mounts are an integral part of the frame, and standard C or CS-mount lenses are screwed into these holders. There is an IR cutoff filter, with a knee at approximately 680 nm, permanently mounted inside the lens holder. See Section 6 for appropriate lens characteristics.

The interface module is mounted on the back of the stereo head. One IEEE 1394 port is placed at the back of the module; it is inset so that the IEEE 1394 plug does not stick out from the device.

A status LED indicates video imager activity. It will turn on when the device is powered and connected to an IEEE 1394 card on the host computer. The LED will begin flashing as soon as images are being acquired by the host computer, at ½ the frame rate. Changing the video modes (frame size, decimation) will cause the frame rate to change, and this will be reflected in the LED flash rate.

There are no user-settable switches on the STH-DCSG/-C.

3.1 Hardware Schematic

Figure 3-2 shows the design of the internal hardware of the STH-DCSG/-C. In the stereo imager module, two CMOS imagers, each of size 640x480 pixels, digitize incoming light into a digital stream. The imagers operate in progressive mode only, that is, each line is output in succession from the full frame.

The maximum video rate is 12 megapixels per second from each imager. The imagers are synchronized to a common clock, so that the corresponding pixels from each imager are output at precisely the same time. Special interlace electronics convert the individual streams into a single pixelinterlaced stream at 24 MHz. The interlaced stream contains one byte from the left imager, then the corresponding byte from the right imager, then the next byte from the right imager, and so on.

The interlaced video stream is transferred to the IEEE 1394 interface module, which communicates to the host PC over an IEEE 1394 digital cable. The module also accepts commands from the host PC over the cable, and uses these commands to control imaging modes such as exposure or subwindowing.

The IEEE 1394 interface module can communicate at the maximum IEEE 1394 data rate, 400 MBps.

3.2 Frame Formats and Rates

The IEEE 1394 interface electronics on the STH-DCSG supports a maximum rate of 32 megapixels per second. At this rate, there is no need for large buffer memories to hold video data on the stereo device. The STH-DCSG/-C conforms to the IIDC version 1.30 camera specification. Frame rates and frame sizes are set by this standard. The STH-DCSG/-C implements the formats shown in Table 1.

The Digital Camera Specification was set up with monocular cameras in mind. To conform to this specification, the STH-MDS/-C uses the YUV

Figure 3-1. Physical layout of the STH-DCSG/-C stereo head.

Left C/CSmount lens

IEEE 1394

ort on bac

Right

C/CS-mount

lens

LED indicato

data type, sending the left stereo image in Y, and the right image in the UV pixels.

Each image from the stereo camera has 8-bit pixels. In the case of the color version (STH-DCSG-C), the color information is encoded as a Bayer pattern in the same 8-bit pixel image.

On the host computer, the SVS interface software takes the YUV stream and parses it into the left and right images, making them available as separate images in computer memory. It also performs color processing, for the STH-DCSG-C, converting the Bayer pattern into full-color RGB images.

The STH-DCSG also has a subwindow mode, in which only the center portion of the image is returned. See Section 7.4 for full information on the modes and resolutions for the STH-DCSG.

For the monochrome device only, smaller frame sizes are also available using on-chip binning. Binning averages neighboring pixels to produce a smaller image with improved noise characteristics.

3.3 50 Hz Operation

Indoor lighting, especially from fluorescent fixtures, can oscillate at the frequency of the electrical supply. If the image frame rate does not divide evenly into this frequency, there can be moving horizontal bands of alternating light and dark moving in the output.

For countries with 60 Hz power such as the United State, the frame rates in the third column of Table 1 are ideal. In many other countries, the

Left Imager

Right Imager

Interlace Electronics

Imager module

1394 Interface Electronics

1394 module

8-bit pixels 12 MHz per ima

Interlaced

ixels

24 MHz

1394 Digital Cable

1394 imaging commands

Digital Video Stream

1394 commands

Figure 3-2 Schematic of the STH-DCSG/-C electronics.

Format Frame

size

Frame rate, 60 Hz (default)

Frame rate, 50 Hz option

Format 0, Mode 3 YUV 16 bits Left image on Y, right image on UV

640x480 3.75, 7.5,

15, 30 Hz

3.125, 6.25,

12.5 25 Hz

Format 0, Mode 1 YUV 16 bits Left image on Y, right image on UV

320x240 7.5, 15, 30,

60 Hz

6.25, 12.5, 25, 50 Hz

Table 1 Frame formats and sizes for the STH-DCSG/-C.

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