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The automatic exposure control (AEC) algorithm adjusts both the exposure time and gain
as part of its algorithm in an attempt to achieve an ‘optimal’ SNR. The AEC algorithm
favours increasing the exposure time over increasing the gain when the image needs to
be made lighter in low illumination conditions and it favours decreasing the gain over
reducing exposure time when the image needs to be made darker. The gain and exposure
settings of the AEC can be modified by use of the ‘Backlight Compensation’ setting
(described above) and the ‘

Exposure, Dynamic Framerate

’ switch (described below).

The AEC algorithm is based on sampling the average luminance in 16 rectangular
subregions within the whole imaging area (these subregions are arranged in a grid 4
regions across and 4 down).

In extremely bright conditions the AEC algorithm will enter into ‘

Light AEC

’ mode (LAEC)

which allows integration time to be less than 1 row.

In extremely dark conditions the AEC will activate '

night mode

' which allows integration

time to be larger than one frame. In night mode, the chip can integrate up to 8 frames by
slowing down the original frame rate and waiting for exposure. This is what enables the
AF51 to be used in medium low light level applications that would otherwise not be
practical for a CMOS cameras of this type.

Night mode and LAEC cannot be set via the manual exposure control (they are beyond
the limits of the ‘

Exposure Time, Absolute

’ range) but they can be entered into and fixed

as a constant setting if the AEC is de-activated when either of these modes is currently
operating. In this way they can be used as ‘one-touch’ fixed settings.

The ‘

Exposure, Dynamic Framerate

’ control is an on (1) / off (0) setting which only

makes a difference when in auto-exposure (‘Aperture priority’) mode. When on, this
enables the AEC to override the camera stream frame rate (selectable by the user – see
later in this manual for the available frame rates) so as to reduce the frame rate even
further for darker illumination scenes to allow longer exposure times. This effectively
allows you to get the maximum light sensitivity in low light conditions when using certain
camera format steams that have a faster frame rate setting. If you set this to 0 then the
AEC range will be limited by the frame rate of the current camera image format stream –
you will be able to image faster moving action but with lower light sensitivity. The effect of
this setting remains constant if you switch off the AEC mode (by setting ‘

Auto Exposure

’

to 0) while ‘

Exposure, Dynamic Framerate

’ is active. In these circumstances, changing

the setting ‘

Exposure, Dynamic Framerate

’ will have no effect until you set a value for

‘

Exposure Time, Absolute

’ or until you re-enter AEC mode by setting ‘

Auto Exposure

’ to

3.

OptArc AF51 Camera Page 29 of 99 User Guide v1.02

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Содержание AF51

Страница 1: ...ocument created 28 10 2022 Last edited 24 11 2022 Manual prepared by OptArc Designers and manufacturers of custom optical and optoelectronic systems using 3D printing rapid prototyping and based in the UK See optarc co uk for details ...

Страница 2: ...s and the eyepiece these measures will not eliminate all risk of damage and some risk will always remain that pressure from the clamp mechanism may cause wear scratches and or indentation to the outer casing of the eyepiece The user is advised to use minimum force when clamping the camera to an eyepiece and take whatever additional measures they see fit to reduce the risk of this external damage e...

Страница 3: ...have FCC RoSH and CE certification We have not made independent tests on this so have not marked the camera with those certifications The AF51 camera is supplied and sold on the understanding that this is an item of custom equipment for scientific research applications OptArc AF51 Camera Page 3 of 99 User Guide v1 02 ...

Страница 4: ...AF51 12 2 Recommended uses and limitations 15 Recommended uses of the AF51 15 Extra wide field of view afocal eyepiece projection 15 Colour imaging in bright conditions 16 Medium low light level applications 16 General and macro photo video recording 16 Limitations of the AF51 18 Highest magnification imaging 18 Short eye relief or narrow field eyepieces 19 Extreme low light level imaging 19 Why n...

Страница 5: ...bility 49 Eyepiece eye relief limits of usability 52 Adjusting on an eyepiece to get a good image 56 Preliminary steps and aims 56 Types of adjustment available 57 Centring the optical axis 57 Achieving the correct eye point level 59 6 Introduction to PARD Capture 60 Compiling the software 61 Starting the program The main window 62 Preview frame integration night vision 66 The settings window 70 C...

Страница 6: ...oise 90 Colour streak artefact in low light conditions 92 Making a master flat and master dark for astronomy 93 Unnatural edge sharpening 93 Sample images 94 8 Disposal and Recycling 95 Recycling of PLA Plastic in the UK 95 Recycling of PLA Plastic outside the UK 95 Electronics 95 Index 96 OptArc AF51 Camera Page 6 of 99 User Guide v1 02 ...

Страница 7: ...he OptArc website via this link https www optarc co uk support The CAD files for the 3D printed eyepiece clamp for this camera have been made open source so you can attempt to modify it and print your own version to fit an eyepiece that the standard clamp does not fit See the Github page here https github com TadPath PUMA For video demonstrations on how to use this camera as well as the PARD Captu...

Страница 8: ...ability for any such damage to eyepieces Dr Paul J Tadrous TadPath and OptArc cannot accept any liability for any loss or damages that may occur from the misuse or mis handling of this product or from the failure to heed and abide by the warnings and safety notices set out in this document All information in this document is believed to be accurate according to the research and understanding of th...

Страница 9: ...ng FDM Fused deposition modelling method of 3D printing FITS Flexible Image Transport System file format FOV Field Of View FPS Frames Per Second gcc GNU Compiler Collection C compiler and linker software GNU GPL GNU General Public License HD High Definition HSI Hue Saturation Intensity JPEG Joint Photographic Experts Group compression standard for digital photos LENC A pattern of variable gain acr...

Страница 10: ...ormat PUMA Portable Upgradeable Modular Affordable open source 3D printed microscope system RGB Red Green and Blue SDK Software Development Kit SNR Signal to Noise Ratio SOC System On a Chip TV TeleVision UNC UNified Coarse screw thread standard US United States of America USB Universal Serial Bus UVC USB Video Class a communications protocol standard for video devices v4l2 Video for Linux 2 progr...

Страница 11: ... otherwise acquired separately 1 AF51 camera body with two centration adjustment screws and a female tripod thread socket to accept a standard 1 4 20 UNC threaded tripod screw a tripod is not included and a Type A USB male connector on the end of an approximately 42 cm long USB cable 2 A protective lens cap shown here removed from the lens The camera will ship with this lens cap in place and the u...

Страница 12: ...oscope system figure 1 3 but it may also be used with other optical equipment that use an eyepiece such as other microscopes and telescopes It has its own integral lens with user programmable focus so may also be used for normal photography and video recordings as an industrial inspection camera for machine vision projects as a document camera a web cam etc The camera requires a separate computer ...

Страница 13: ...ises the tendency to cause vibrations on the scope and fits in with the portability ethos of the PUMA system The camera is designed with a built in lens to image via afocal eyepiece projection and the lens system is designed to give a complete circle wide field of view when used with an OptArc x10 WF high eye point eyepiece The field of view with other eyepieces will vary see chapter 5 for details...

Страница 14: ...s which are important for scientific image processing like Z stacking extended focal imaging EFI deconvolution quantitative microscopy and some forms of astrophotography Another bonus feature is that the casing is 3D printed and the design files for the eyepiece clamp system are available free of charge as open source FreeCAD files so a user with access to 3D printing either DIY printing or an onl...

Страница 15: ...for the OptArc x10 WF eyepieces and many other types but with some extra wide field eyepieces the circular field will be cropped on top and bottom These eyepieces therefore use more of the available pixels of the camera for their image of the specimen at the expense of not seeing the whole circular field of view Details of how much of the camera sensor is used by the the eyepiece field of view wit...

Страница 16: ...w light level applications The AF51 can also be used in medium low light level applications including dark field microscopy and immunofluorescence Achievable frame rates will be lower due to the need for longer exposure settings and multi frame integration on the sensor chip and averaging in software for the lowest end of the useable light level scales At the lowest light settings the monochrome s...

Страница 17: ...s use as a document camera use for machine vision applications e g industrial inspection of products for quality control facial recognition robotics use as a web camera etc whenever the wide field of view of this camera is advantageous to that task The camera can also be used for time lapse sequences e g of natural phenomena or for filming 3D printing Figure 2 2 The AF51 being used as a standard c...

Страница 18: ... becomes an issue because the object is so close to the camera body Figure 2 3 Part of a US 1 dollar bill captured with the AF51 in its macro mode Note that images shown in this manual are compressed and down sized for the PDF so do not represent the full quality of the original image taken from the camera This figure just gives an idea of the scale of the macro setting Limitations of the AF51 Hig...

Страница 19: ...ry small field of view and excessive vignetting See chapter 5 for more details and measurements for various eyepieces Extreme low light level imaging The AF51 is not recommended for extreme low light applications such as faint bioluminescence deep sky faint object astrophotography or low light level imaging of fast moving objects This is because the AF51 uses its own lens with a small aperture and...

Страница 20: ...age with multi frame averaging manual control of exposure colour balance etc and the ability to maintain a good signal even in low light levels see chapters 6 and 7 of this manual All this can be done with the AF51 and PARD Capture software If you can do all too that with your smartphone camera and have it well mounted on the microscope then I see no advantage of using the AF51 over such a device ...

Страница 21: ...columns x 1956 rows 5 132 544 total pixels with a primary colour blue green green red Bayer array arranged in line alternating fashion see figure 3 1 The array includes active pixels signals from which are read out to form the image and inactive pixels used for black level calibration Active array size 2592 x 1944 5 MP Image area 3673 6 mm x 2738 4 mm Optical projection characteristics Suitable fo...

Страница 22: ... firmware interface Programmable 16 zone size position weight control cropping windowing and panning Lens correction LENC i e a programmable fixed pattern of gain that varies across the sensor area to compensate for uneven illumination caused by the lens optics System clock control is via an on chip phase locked loop PLL that generates a default 96 MHz clock from a 6 27 MHz input clock An inside p...

Страница 23: ...ed below Lens system Effective Focal length 2 8 mm Field of view angle 76 degrees TV Distortion 1 F number 2 2 Relative illumination of sensor 70 IR Cut filter 650 nm 10 nm fixed Construction 4 element Focus Electromagnetic voice coil mechanism allows for continuous auto focus and programmable manual focus figure 3 2 Distance 3 cm to infinity The closest distances are most reliably achieved using ...

Страница 24: ...ons are only adjustable to hardware developers in the factory using specialist development interface boards Not all of those features are programmable or controllable by the end user of the camera For example the LENC gain pattern across the sensor has been programmed at the factory and cannot be altered by the end user via the the USB 2 0 interface board The features provided to the user by the U...

Страница 25: ...omatic white balance AWB on 1 or off 0 When on the current value for White Balance Temperature will be ignored and cannot be set When AWB is turned off the value currently held in the White Balance Temperature will be applied Varying that value will vary the white balance setting of the image The value for Power Line Frequency corresponds to 3 menu options Disabled 0 50 Hz 1 and 60 Hz 2 This works...

Страница 26: ...ter you can change from 0 directly to 3 The reason for this behaviour is that the off 0 setting for this control simply leaves the setting where it was last it is effectively non functional The Backlight Compensation feature affects the behaviour of the automatic exposure level when the automatic exposure control AEC is enabled automatic exposure settings are discussed below in the section on the ...

Страница 27: ...ould normally do without compensation see figure 3 5 Figure 3 5 Backlight Compensation factors of 0 1 and 2 from left to right on an unevenly lit background from a microscope using the AF51 in AEC mode i e Aperture Priority exposure mode From the above description it should be clear that changing the Backlight Compensation setting when the camera is NOT in an automatic exposure mode will have no e...

Страница 28: ...e AF51 does not have a separate gain control The exposure setting whether manual or automatic actually sets both the gain and exposure simultaneously The relative contribution of gain and exposure is calculated by means of an on chip algorithm that is designed to maximise the SNR for any given lighting condition See below for details Manual mode provides a constant fixed gain value and exposure ti...

Страница 29: ...is type Night mode and LAEC cannot be set via the manual exposure control they are beyond the limits of the Exposure Time Absolute range but they can be entered into and fixed as a constant setting if the AEC is de activated when either of these modes is currently operating In this way they can be used as one touch fixed settings The Exposure Dynamic Framerate control is an on 1 off 0 setting whic...

Страница 30: ...16 9 format image Figure 3 6 Effect of varying the Tilt Absolute control when in a wide format mode showing how this can select what part of the full sensor image to display in the wide format output Top left is an image taken with a 4 3 aspect ratio image format which captures the full sensor data Wide screen formats have to leave out some of the vertical sensor information The default Tilt Absol...

Страница 31: ...ause the AF51 zoom mechanism works by sampling from the full 640x480 VGA output of the chip even when the chosen video stream size is lower resolution than this The higher the zoom factor the closer to 1 1 sampling of the full VGA image is produced recall that zooming only works for image formats lower than full VGA However capturing such a zoomed image does not give quite as good an image quality...

Страница 32: ...s Focus Automatic Continuous should be disabled set to 0 when using the AF51 with an optical instrument coupled to an eyepiece and for proper afocal eyepiece projection coupling this fixed focus should be at infinity Focus Absolute gives you manual or programmatical control over the focus to produce a fixed focus of the lens at a position determined by the value supplied for this control The value...

Страница 33: ...able camera stream formats for the AF51 Also shown is the compatibility of each format with the digital Pan Tilt and Zoom controls of the camera These are the closest approximations to 16 9 aspect ratio that maintain modulo 16 compatibility i e each dimension pixel count is exactly divisible by 16 This is important because encoding frames into a streaming format is done by breaking the frames down...

Страница 34: ...longer frame exposure times etc 3D Printed housing The sensor chip and interface board are set in a 3D printed enclosure made with PLA filament and designed to enable adjustable mounting of the camera on a variety of eyepieces or on a standard tripod and to provide heat sink passive cooling for the sensor chip and interface board The casing is made with an Ender 3 FDM 3D printer Heat sink enclosur...

Страница 35: ...llow aluminium heat sink foil There are no user serviceable parts or adjustment controls inside this enclosure Under no circumstances should this casing be opened otherwise the spring holding the heat sink system against the back of the sensor chip will come loose and the heat sink will loose its effectiveness resulting in malfunction of the camera For this reason also avoid handling the camera ro...

Страница 36: ...allow a degree of XY shift freedom in this fit see figure 3 9 The inscribed circles printed onto the flat part of the camera heat sink enclosure serve as a guide to help you know how nominally centred is the translation adjustable mount relative to the camera heat sink enclosure Figure 3 9 The translation adjustable mount allows the user to centre the camera over any eyepiece Top panel shows the m...

Страница 37: ... on the thumbscrew nut Right Turn the tool to tighten or loosen the grip of the thumbscrew nut Take care to avoid over tightening or the tool may be damaged Eyepiece clamp The eyepiece clamp is only required when using the camera with an eyepiece you should not fit it if you are using the camera for ordinary or macro photography with its own in built lens because it will obstruct part of the perip...

Страница 38: ...een the lock nut and the base of the threaded region This adjustment cannot compensate for eyepieces with very short eye relief and such eyepieces will require a customised adapter to be designed and printed Such customisations are possible due to the 3D printed nature of the clamp but will need to be done by the user custom clamp are not supplied with the AF51 as sold by OptArc For eyepieces with...

Страница 39: ... folds are flat against the inside of the clamp giving maximum clearance Bottom Right After the connections break there will always be some residual in folding of the flexure giving narrower clearance When this clamp is brand new freshly printed the flexure folds of the inner sheath will be flush against the walls of the clamp figure 3 12 bottom left but with use these folds flex inwards and the t...

Страница 40: ...uld damage the plastic sheath like a screwdriver or other metal instrument to push these folds back because these can wear away or tear the protective parts of the thin plastic sheath that lie over the metal screws and expose the metal screws directly to your eyepiece casing at which point damage to the casing will definitely result if you continue to use the clamp If the inner sheath does get dam...

Страница 41: ... body of the eyepiece so that the top ledge of the clamp no longer rests on the eyepiece See text for details While the thumbscrews remain loose you should have some angular adjustment of the camera on the eyepiece as well as the ability to slip the clamp up or down on the eyepiece see figure 3 15 All these adjustments together with the simple XY adjustment shown in figure 3 9 allow you to get the...

Страница 42: ...tilt available will also be very restricted Now gently tighten the three thumbscrews till the eyepiece is held firmly in position but do not over tighten the thumbscrews or damage to the eyepiece casing or coatings may result A sudden jolt to the camera while it is mounted on an eyepiece may also damage the eyepiece casing or coating These risks can never be fully removed so take care to avoid suc...

Страница 43: ...Pads without some additional specialist interface electronics the availability quality and compatibility of which I have not tested Therefore I do not recommend using the AF51 with Apple iOS devices The host computer you use must be able to supply the 500 mW of USB power required to power the camera Software No separate drivers are required to use the AF51 camera because the UVC protocol built int...

Страница 44: ... GPL v 3 PARD Capture will be described in more detail in a separate chapter It is designed primarily for scientific still image capture including time lapse sequences and low light level work and real time video previewing but it is not suitable for real time video capture PARD Capture allows full control of all the AF51 features described in the previous chapter as well as providing additional f...

Страница 45: ...The project page and source code link is https sourceforge net projects guvcview Microsoft AmCap and SDK for Windows AmCap is open source software by Microsoft It is distributed under the MIT license It is only for Microsoft Windows It is legacy code that is for Windows 7 1 and Windows Vista but it can also work on Windows 10 It can control all the functions of the AF51 The Exposure Dynamic Framer...

Страница 46: ...g saving raw data in floating point formats saving the Y only data etc On Windows 10 I compiled AmCap exe like this 1 Download MS software development kit SDK for Windows 7 1 Vista from here https msdn microsoft com windowsvista bb980924 aspx The SDK contains many components and examples one of which is AmCap 2 Download Free Community Edition of MS Visual Studio from Microsoft you will need a Micr...

Страница 47: ...tion appropriate to the type of build you made debug or release e g in C Program Files Microsoft SDKs Windows v7 1 Samples multimedia directshow capture amcap x64 Debug AmCap exe or C Program Files Microsoft SDKs Windows v7 1 Samples multimedia directshow capture amcap x64 Release AmCap exe 10 Connect your AF51 camera to the computer then double click the AmCap exe file Webcamoid for macOS Android...

Страница 48: ...vely recent Check the project pages for the latest on Android compatibility The project page and source code links can be found here https webcamoid github io Apple macOS and iOS The camera should work on macOS previously called OS X or Mac OS X using the Webcamoid software described above and other software capable of running UVC video devices You should also be able to write your own custom soft...

Страница 49: ...AF51 Not all these eyepieces can be used with the standard AF51 eyepiece clamp and not all of them provide a field of view that fills the camera frame sufficiently to give a high resolution image Details will be provided in this chapter Of course I cannot test all possible eyepieces so I will list the eyepiece measurements alongside the results so the reader can use this data as a guide as to how ...

Страница 50: ...e units are mm The Zeiss will be too small to fit the standard AF51 eyepiece clamp without a special adapter not supplied The Celestron will be too large to fit See text for details The standard clamp mechanism of the AF51 was designed to work optimally for eyepieces with a maximum outer diameter of 35 mm to 36 5 mm However it will work with eyepieces that have a maximum outer diameter in the rang...

Страница 51: ...p the body of the eyepiece Some eyepieces have a significantly narrower diameter e g some vintage eyepieces from Zeiss e g 28 mm diameter for the Zeiss W Kpl x10 and Reichert e g 29 mm diameter for the BPK 10x as well as some modern cheap generic eyepieces These are too narrow to be gripped by the indentations of the inner sheath of the AF51 standard eyepiece clamp even when the 3 clamp screws are...

Страница 52: ... with the standard clamp For those eyepieces with short eye relief therefore some custom adaptor will again need to be made or acquired by the user they are not supplied with the camera To give you an idea of whether the standard clamp will work fully with a particular eyepiece I have tabulated my results with the 13 eyepieces tested Manufacturers use various methods to measure eye relief distance...

Страница 53: ...ronomical eyepieces tested in this group the Bresser 20 mm SPL and the Celestron X Cel LX 18 mm both of which are claimed by the manufacturer to have an eye relief of 16 mm My measurement of eye point gave a value of 15 mm for the Bresser and 18 mm for the Celestron This difference may be accounted for by the fact that the level of the focal plane of astronomical eyepieces are not standardised lik...

Страница 54: ...n the eyepiece Olympus SWHK 10xL 36 17 22 Yes Yes 76 75 3 87 No PUMA BH2 Locknut at 1 full thread Olympus WK 10x 20L 37 5 16 17 5 Yes Yes 44 69 2 25 Yes PUMA BH2 Locknut very close to base Olympus WHK 10x 20 L 36 20 19 Yes Yes 46 9 2 36 Yes PUMA BH2 2 threads Zeiss W Kpl 10x 28 18 5 21 No Yes 37 75 1 9 Yes PUMA Zeiss 2 threads with thin eyepiece adaptor Reichert BPK x10 29 19 18 5 No Yes 38 1 91 Y...

Страница 55: ...e field eyepieces tested this is not the case because the width of the eyepiece field is wider than the width of the camera field of view All the eyepieces were tested on a PUMA microscope with some also tested on other microscopes a Zeiss Standard an Olympus BH2 BHS and a Leica DMLS Field of view measurements were about the same regardless of which microscope was used but eye point measure differ...

Страница 56: ...djusting on an eyepiece to get a good image Preliminary steps and aims The first thing to do is ensure the microscope is on and looking down the scope by eye using the eyepiece you intend to use for photography you see the whole field of view of the scope is evenly illuminated and you can see a specimen in focus Next ensure the camera is on and you can see a live image preview the MJPEG image stre...

Страница 57: ...The first thing to do is centre circular eyepiece field of view in the rectangular camera field of view This is done with adjustments 1 and 2 described above but because adjustment 1 XY shift is already set at a nominal central position you should begin by making angular adjustments till you catch the optical axis in the camera s field of view then make small corrective adjustments iterative in bo...

Страница 58: ...ry than the centre but do ensure that the brightest part of the image is well centred in the circular field of view Also ignore the position of the specimen under the microscope you are only concerned about the patterns of illuminating light in figure 5 6 I moved the specimen on the stage in between image captures so it will not look in the same position in each image but that is irrelevant as is ...

Страница 59: ...e 5 7 Figure 5 7 Adjusting the height of the camera above the eyepiece such as to provide the flattest illumination across the field a The camera is too high above the eyepiece b The camera is too close to the eyepiece c The camera is just at the optimal level Note that while you make this adjustment you may need to also adjust the axis as well as shown if figure 5 6 because while making these hei...

Страница 60: ...ditions see chapter 7 for more on that The free and open source PARD Capture software on the other hand was specifically designed for optimal image acquisition for scientific image capture including Y only images and this chapter will take you through the basics of its usage Chapter 7 will give some practical tips for optimal quality image acquisition and show example images PARD Capture uses the ...

Страница 61: ...libs devel Table 6 1 Dependencies for PARD Capture Install these using your Linux installation method before compiling the PARD Capture software Note Arch Linux installs the developer parts of a lib as standard with each lib Other types of Linux need to specifically install the dev or devel versions of the lib Once all the dependencies are installed compile the PARD Capture code itself called pard...

Страница 62: ...ll output messages will be recorded in this log file as a plain text file so you may want to give it a txt extension but that is not mandatory If the user does not have access permissions to the chosen file then a pop up error message will alert the user that logging can t be done but the program will then continue as usual The start up screen main window is shown in figure 6 1 The camera status l...

Страница 63: ...mage capture because the camera will heat up more when it is streaming images The Preview check box allows you to toggle on and off the live preview of images from the camera This will only have any effect if the camera is streaming so if you see nothing when you check this box make sure the camera is streaming and turn on streaming if it is off see preceding paragraphs The Use beeps check box ena...

Страница 64: ...ount down the duration of which is set via the settings controls discussed later So in that case activating the Save Image button will start the count down followed by the capture event When a series capture is in progress the Save Image button will change its text to a bold red Cancel Series label Clicking the button when it shows this label will terminate the series capture sequence after the cu...

Страница 65: ...ew area because this will show if the camera is streaming or not and also to look at the Turn ON OFF Streaming button because it will show Turn ON Streaming if the stream is currently off compare figures 6 1 and 6 2 The preview area is a constant size being at VGA resolution 640x480 pixels and it cannot be scaled When wide format images are being streamed they will show in this area at full width ...

Страница 66: ...is integration mode and all its features and options are available and functional even if only 1 frame is integrated i e no actual multi frame integration takes place Figure 6 2a Preview frame integration controls The Preview Integral is a number from 1 to 20 The number shown here is the number of frames that will be integrated before the final resulting compound frame is displayed A rolling integ...

Страница 67: ...ailable range for Preview Bias is from 4845 to 512 Note that preview frame integration and bias calculations are all performed in integer arrays in the program that is the int data type in the C programming language so can handle very large resulting negative and positive intensity values at least 32768 for computers with 2 byte integers but many modern computers have an int that is 4 bytes long s...

Страница 68: ...t not a preview master flat Green means that only a preview master flat is loaded but not a preview master dark Blue means that both a master dark and a master flat preview correction image are loaded A valid preview master dark must be in raw doubles format with dou extension a qih external header file and it must be of the same dimensions as the preview image currently this is VGA i e 640 pixels...

Страница 69: ...ember Eject All will not show unless a custom preview master dark or master flat is loaded Similar behaviour occurs when you click the Load P Flat button If you click the multifunction button when it displays Eject All you will get a pop up confirmation box that will give you the option to either go ahead with the ejection or cancel your request for ejection either way when you respond to that box...

Страница 70: ...ontrols are mostly in the form of a text entry box but sometimes a drop down menu or a check box instead For those cases where a file needs to be selected a button is provided that brings up a file chooser dialog box so you can select a file name In the middle column of the settings window is a list of the currently applied value for each setting On the right is a description of the setting as wel...

Страница 71: ... I have clicked in the Gamma entry box to give it current focus it is outlined in blue and the real time control slider at the top is labelled Gamma and shows the current Gamma value as well as the limits of possible gamma choices See text for further details OptArc AF51 Camera Page 71 of 99 User Guide v1 02 ...

Страница 72: ...s no option for real time control with the slider bar as there is for the Camera and User settings The Image size and FPS for full frame capture drop down list shows all the image stream sizes and maximum frame rate for each one that are available for the type of stream format that is currently selected This is important to realise because it you select to change the camera stream format then the ...

Страница 73: ...gure 6 4 Scrolling down the settings window we have the Custom controls These are the same for any camera that can be used with the PARD Capture software OptArc AF51 Camera Page 73 of 99 User Guide v1 02 ...

Страница 74: ... This will be a raw array of unsigned integers at 16 bits per pixel bpp i e unsigned shorts There will be 1 integer for every pixel so the array will be if total size height x width integers The integers will be arranged in raster fashion from top left pixel 0 to bottom right pixel height x width 1 Each 16 bit integer will contain two 8 bit values the first byte is a luminance value and the second...

Страница 75: ...ause it uses the full RGB data up until the end if you want to do dark field subtraction or flat field division corrections see below you must supply a 3 channel colour master dark image or master flat image see figure 6 5 PPM This saves a 24 bpp colour image in the PPM P5 format The saved file will have an ending of the form _rgb ppm If the camera is streaming in YUYV format a full YUYV to RGB co...

Страница 76: ... entry box The complete file name used to save an image is constructed in the form root_ ending where root is the string supplied for the File name root for saved images setting is an integer that starts with the value supplied for the File name frame number start from setting and ending is the ending described under each format of the Format to save the image files to disk as setting described ab...

Страница 77: ...s clipped into the 0 255 range for 8 bpp and 24 bpp outputs but it left in its double precision floating point form for output as raw doubles and FITS The corrections mask support see below is not used for multi frame averaging full support is used always even if a custom corrections mask has been supplied When the program interfaces with the camera stream it has to request a frame from the camera...

Страница 78: ...ll be started and the Save Image button will return to its normal appearance The JPEG save quality setting has been described above in the JPEG section of Format to save the image files to disk as The YUYV conversion gain and YUYV conversion bias settings are floating point numbers which represent the gain and bias used in converting the raw YUYV values from the camera s YUYV stream into RGB value...

Страница 79: ...es in addition to whatever save as format you selected with the drop down list described above This option will be ignored if the save as format selected from the drop down list is Raw YUYV or if it is Intensity because that will be saved as raw doubles anyway or if it is JPEG and no multi frame averaging is being done If it is JPEG and multi frame avaraging is being done then this option will be ...

Страница 80: ...l be used in the calculations and corrections Figure 6 6 shows the algorithm used to apply the optional pre processes The Scale mean of each frame to first option when selected is a pre process applied to multi frame averaging sequences It therefore has no effect if multi frame averaging is not being done If this option is selected then when a multi frame average is first started the first image f...

Страница 81: ...e must end in _Y dou or _I dou or _y dou or _i dou and have a corresponding qih external header file Such images with compatible file names for either colour or monochrome use can be generated by PARD Capture using the Save as raw doubles option or using the Intensity save as format described above The Apply flat field division option when selected divides each frame captured by a pre processed ma...

Страница 82: ... will be performed on all pixels of the frame i e a full support mask will be internally generated You chose your what custom corrections mask image to load with the Select button below this check box This brings up a file chooser dialogue box from which you can select a file File formats that are acceptable for use are those with the following extensions ppm a PPM P6 formatted image pgm a PGM P5 ...

Страница 83: ...ave as format of Intensity then you must supply an RGB format image as the master dark or master flat image even though the output will be monochrome Regardless of image save as type whether colour or monochrome only one identical mask is applied to all colour channels For this reason if a colour format mask image was chosen the data in the three colour channels is reduced to a single channel by e...

Страница 84: ... values contained in the settings file as if you had entered those valued manually yourself However the settings file load process will not apply the settings The settings will be applied when you manually click the Apply All Settings button at the top of the settings window This gives you an opportunity to inspect the loaded values and modify them if you wish When you save a settings file the fil...

Страница 85: ...files are generated automatically by PARD Capture and must be of a particular format to be readable by it but a settings file may be manually edited provided you adhere to the rules and restrictions on editing described here Failure to adhere to these rules and restrictions could make the file unreadable by the program or worse crash the program or spoil your camera For this reason it is best not ...

Страница 86: ...ngs up at the beginning of the file The file reader in the PARD Capture software does not care about that The camera firmware settings come in blocks Each block begins with idx followed by an integer and the line after that is the name of the control preceded by name If you make any edits you must ensure that idx always comes immediately before its corresponding name line Any number of blank or co...

Страница 87: ...Capture for each setting Like any comment these can be edited or removed at will without adverse effect The end of the file as far as PARD Capture is concerned is marked by the line that has the single word exit on it After this line PARD Capture stops reading the file and closes it You may therefore write whatever free text you like after the exit line in whatever format you like those lines do n...

Страница 88: ... should be prepared and applied as flat field correction to the main image frames when you capture them The PARD Capture software provides the facilities to both make a master flat field image and apply flat field correction during image capture If you are using other software to capture your images from the camera you may have to perform flat field correction using multiple software packages over...

Страница 89: ...rtefacts and random noise The raw output of each frame from the AF51 camera can distinguish 256 brightness levels per channel from 0 to 255 maximum This 8 bit depth of intensity quantisation causes chunky steps in colour or grey levels in regions where the intensity varies only slightly This is quantisation artefact the actual intensity varies smoothly in real life but can only be digitised into d...

Страница 90: ...verage Dark current signal bias and amplifier patterned noise The presence of a fixed pattern of pixel readout information in total darkness is common to CCD and CMOS cameras and seldom are pixel values ever 0 even in complete darkness For this reason for quantitative imaging it is recommended to subtract a master dark frame from all captured image frames prior to any other processing The PARD Cap...

Страница 91: ...ty channel from a YUYV to_RGB transform still using the YUYV output from the camera Top Exposure setting of 1269 Middle Exposure setting night mode maximum frame integrations Bottom Close up of the small flare seen in the middle panel Such small imperfections in the pixel read out amplifiers are not unusual and this is part of the fixed pattern dark field noise which dark field subtraction is desi...

Страница 92: ...d we can expect some light to get to those pixels and bias them sufficiently to overcome this deficiency and read out some meaningful signal However when a longer exposure time is allowed such as in the middle row pictures of figure 7 3 sufficient charge has built up in all pixels across the field even in complete darkness due to thermal dark current signal accumulation that they all read out sign...

Страница 93: ...uctory links that may be useful in this regard are as follows http spiff rit edu classes phys445 lectures darkflat darkflat html https core ac uk download pdf 37772805 pdf https www cfht hawaii edu baril Pyxis Help flatdarkfield html https www stsci edu instruments wfpc2 Wfpc2_dhb wfpc2_ch44 html http astro corlan net gcx html node7 html https github com deepskystacker DSS releases tag 4 2 2 Relea...

Страница 94: ...s which is not good for many types of image analysis Sample images All the images in this PDF document are either downsampled or compressed or both so cannot reflect the true quality of images from the camera A selection of full and uncompressed images taken with the AF51 camera is available on the PARDUS project GitHub page For example see https github com TadPath PARDUS blob main PARD_Capture Sa...

Страница 95: ... should therefore be disposed of in general household waste or sent to a specific facility that will accept it for recycling Those with the ability to do so may also grind used PLA and reform it into usable 3D printer filament Recycling of PLA Plastic outside the UK Please consult with your local authorities for recycling advice Electronics The interface board and CMOS sensor contain surface mount...

Страница 96: ...cal axis 57 children 2 chromosomes 19 CMOS sensor 21 Colour streak artefact 92 Compiling 61 Compiling AmCap 46 Compiling PARD Capture 61 contrast 27 Contrast 25 copyright 8 Customise the camera to fit your eyepiece 7 Dark current 21 Dark current signal 90 Disposal 95 document camera 17 Ender 3 34 Exposure Time Absolute 28 Exposure Aperture Priority Mode 28 Exposure Dynamic Framerate 29 Exposure Ma...

Страница 97: ...tArc 8 Pan 30 PARD Capture 44 60 Algorithm image capture and pre processes 83 Apply All Settings button 70 Apply dark field subtraction 81 Apply flat field division 81 BiaQIm header file 75 BMP 24bpp 75 camera status 62 Cancel Averaging 76 Cancel Series 78 command line 62 count down 78 Custom settings 72 Default settings 84 Delay first capture by s 78 Eject All 69 File name frame number start from...

Страница 98: ...79 Save as raw doubles 79 Save Image 64 Scale mean of each frame to first 80 Series number of images 77 settings 70 Settings 63 settings files 84 single frame picture 64 time lapse 78 Turn OFF streaming 63 Turn ON Streaming 63 Use beeps 63 Use corrections mask 82 Use crop from full sized image as preview 65 Use crop from full size image as preview 79 Y BMP 75 Y PGM 75 YUYV conversion bias 78 YUYV ...

Страница 99: ...time lapse 17 tool for tightening loosening thumbscrew nuts 37 Trade Marks 8 Tripod attachment 42 tripod screw 11 USB 2 0 microcontroller 24 USB connector 43 USB power 43 User Controls 25 User s Manual 7 UVC protocol 24 43 voice coil mechanism 23 warnings 2 web camera 17 Webcamoid 47 weight 21 Well capacity 21 White Balance 25 XY shift 36 57 Y channel 60 YUYV 33 60 Zoom 30 f End of Document OptArc...

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