Zahner 12/2011 Light Spectra Display and Analysis
Light Spectra Analysis -2-1. Introduction 3 2. Light Spectra Analysis Graphic Software 4 2.1. Startup...4 2.2. Export Functions...6 2.2.1. Export ASCII List... 6 2.2.2. Export Drawing... 6 2.2.3. Hardcopy... 7 2.3. The Select Spectral Graphic Panel...7 2.3.1. Clear Program Memory... 8 2.3.2. Select Spectra from Program Memory for Display and Analysis... 8 2.3.3. 3D-Plot / Contour Plot of the Selected Spectra... 9 2.4. Graphic Type Control Elements...10 2.4.1. CIMPS-abs spectral data... 10 2.4.2. CIMPS-emit spectral data... 11 2.4.3. CIMPS-pcs Photocurrent Spectra... 12 2.4.4. The Wavelength / Wavenumber Toggle... 13 2.4.5. X/Y Autoscale / Manual Scale Function... 14 3. Cursor Analysis Functions 15 3.1. Entering the cursor mode...15 3.2. Zoom- and Analysis Functions...16 3.2.1. Mark Wavelength Sections... 16 3.2.2. Zoom Re-Zoom Operation... 16 3.2.3. Analyse Marked Wavelength Sections... 17
Light Spectra Analysis -3-1. Introduction With for instance CIMPS-abs, CIMPS-emit or CIMPS-pcs Zahner supports measurement techniques which create light wavelength dependent spectral data. Due to the differentiation between measurement tasks and analysis tasks, which is common to most Thales applications, visualization and analysis support in the measurement environment is restricted. Instead, special analysis software is provided. For wavelength dependent spectral data this is done by means of the lightspectra analysis program LA. LA supports the opening of spectra data files, management of up to 100 curves and providing of many different graphic representations of the data. Orthogonal to any other Thales application, data may be exported as ASCII data list, vector graphics (Windows EMF) and pixel graphic (bitmap, hardcopy) in WYSIWYG manner. In a crosshair sub menu data may be analyzed in order to calculate extremes, line widths and more.
Light Spectra Analysis -4-2. Light Spectra Analysis Graphic Software 2.1. Startup The software is content on the standard Thales installation. It is easily activated by using the pull down menu as shown in Fig. 1. For opening the pull down menu click onto the Z-icon in the title bar of the Thales window. Fig. 1 Start of Light Spectra Analysis using the pull down menu After initialization, the main window of LA is displayed (see Fig. 2). The user must now enter select diagram in order to open the spectral data files of interest for display and analysis operations. Fig. 2 Empty main window of Light Spectra Analysis after startup
Light Spectra Analysis -5- Use file operations and open the data files of interest by marking and confirming the load button. After closing the select diagram panel, the spectra actually loaded are displayed in the default graphic representation provided for the specific data type, if the type is common to all selected spectra. If the type is mixed (e.g. absorption spectra together with emission spectra), all data are interpreted as of dimension intensity. Data may now be printed, plotted or exported, like described in the following.
Light Spectra Analysis -6-2.2. Export Functions 2.2.1. Export ASCII List Copies the content of the measurement data of the selected light spectrum as an ASCII text into the Windows clipboard. Saves the measurement data of the selected light spectrum as an ASCII text file. Select a path and a file name in the browser window. Exported ASCII lists have the file-extension.txt! Passes the ASCII list to the Thales text editor ZEdit e.g. for editing the data. You will end up in the text editor main menu. If you already have some text in ZEdit, you may want to append the ASCII list to the existing text. Chose append list in that case. 2.2.2. Export Drawing Copies the graphics to the Windows clipboard. From there you may paste it to any Windows program which is able to paste graphics from the clipboard (Word, PowerPoint, Draw, etc.). Copies the graph to the Thales CAD software directly. If the CAD graphic board is empty the graph is positioned in the middle of the board. If there is already a graphic present, you are asked where to place the new graphics relative to the resident one. Only in that case the box shown to the left will appear. Saves the graphics to the mass storage in the EMF format. Select a path and a file name in the browser window. You may load the graphics from there to any Windows software which is able to handle EMF files. Click on the save button to save the graphics. Click on the exit button to cancel the operation.
Light Spectra Analysis -7-2.2.3. Hardcopy Clicking on the hardcopy icon creates the hardcopy version of the graph on the screen and gives you the following options: output : sends the graphics to the device selected under settings. form feed : sends a form feed to the printer settings : toggles through the following options big (landscape): sends a A4 format graphics to the printer small (portrait): sends an A5 format graphics to the printer to clipboard : sends the graphics to the Windows clipboard save as file : save the graphics to the mass storage as an BMP file cancel the operation. Select a path and a file name in the browser box and click on the save button to save the data. Click on the exit button to 2.3. The Select Spectral Graphic Panel Fig. 3 Entering the Select Spectral Graphic panel.
Light Spectra Analysis -8- Click the select diagram icon (Fig. 3, left hand side) to open the Select Spectral Graphic panel (Fig. 3, right hand side). In this submenu you can execute certain operations by means of the buttons on the left hand side. The control elements on the right hand side enable you to determine the type of graphic representation you need. The presence of these elements depends on the data type of the spectra loaded and selected. 2.3.1. Clear Program Memory Fig. 4 Deletion of the spectra present in the program memory You may initialize the data memory of the LA program, if you have too much spectra present. The operation sketched in Fig. 4 clears all spectra present in the program memory, but has no influence on the data files in the mass storage media. You have to confirm the are you sure? - Box to finalize the operation. 2.3.2. Select Spectra from Program Memory for Display and Analysis Fig. 5 Entering the select box for spectra already present in the memory. The names of all spectra which are already present in the program memory appear in the select box, if you choose the select spectra function from the panel like sketched in Fig. 5. If more than ten spectra are present, a scroll bar will appear at the right hand side of the box. By means of the confirming mouse button you may select/deselect a single spectrum. If you press the CTRL key simultaneously you may repeat the select/deselect function on several spectra. If you use the right hand mouse button together with the SHIFT key, a field of spectra may be selected / deselected, while the CTRL + A key will mark all spectra. The selecting mechanism is similar to the file select mechanism for data files in the file explorer environment. You have to confirm the select box by means of the -button to finalize the selection. If you use the close button instead, the operation is ignored.
Light Spectra Analysis -9-2.3.3. 3D-Plot / Contour Plot of the Selected Spectra 3D- or contour plots are provided in a different window, if you use the 3-D-display button. Fig. 6 Creating a 3D-Plot in a separate window. The operation is ignored, if only a single spectrum is selected. After pop up you may click on the edges of the graphic grid and pull for changing the view angle of the display. The setting of the checkbox 3-D/contour on the right hand side of the control panel decides, if the 3D graphics (Fig. 6) or the contour plot (Fig. 7) is displayed. Fig. 7: Creating a colored contour plot in s separate window.
Light Spectra Analysis -10-2.4. Graphic Type Control Elements The control elements on the right hand side of the Select Spectral Graphic Panel may be checked / toggled, provided the corresponding function is supported for the actual display type. Changes by means of mouse clicks will cause an immediate redraw and return to the Select Spectral Graphic Panel, if the mouse is moved slightly away from the changed control element. Note: If the mouse position is not changed significantly, the checking status change is not recognized immediately! 2.4.1. CIMPS-abs spectral data The presence of control elements depends on the data type of the spectra loaded and selected. The upper part of Fig. 8 shows the appearance, if all selected spectra are measured by means of CIMPS-abs. Fig. 8 Control elements present for spectra measured with CIMPS-abs (upper part) and the graphic representation accordingly (lower part). Spectra are not copied as bitmaps from the main screen, but as EMF data from the CAD screen by means of an export drawing operation. Terms and definitions for absorption spectra data are handled different in literature. The following table gives an overview upon the definitions relevant for LA. Please note, that the term Absorbance is used by Thales following the usage in astronomy. This definition is also used mainly in the European scientific community. Quantity (name used in Thales) IUPAC name Symbol / Formula Unit Incident radiant power Incident radiant power P 0 W Transmitted radiant power Transmitted radiant power P W Transmittance Transmittance P T = 1 Absorbance Absorptance α = 1 T 1 Extinction Absorbance A = 10 logt 1 For CIMPS-abs data the display in %-units and alternatively the logarithmic scaling in Y direction are available in combination with the absorbance and transmittance settings. P 0
Light Spectra Analysis -11-2.4.2. CIMPS-emit spectral data Fig. 9 left shows the control elements set, if all selected spectra are measured by means of CIMPSemit. Fig. 9 Control elements present for spectra measured with CIMPS-emit (left) and the according graphic representation (right). The spectra are not copied as bitmaps from the main screen, but as EMF data from the CAD screen by means of an export drawing operation. The lin/log radio buttons are active for emittance data, but due to numerical values possibly near zero of intensity spectral data, a logarithmic diagram is not recommended. Please note, that the same panel is displayed as default, if spectra from mixed data types are selected.
Light Spectra Analysis -12-2.4.3. CIMPS-pcs Photocurrent Spectra Fig. 10 left shows the control element set, if all selected spectra are measured by means of CIMPSpcs. Fig. 10 Control settings (left), Photocurrent- (upper) and IPCE spectra (lower) Photocurrent efficiency H IP (λ) is calculated from the photocurrent I(λ) divided by irradiance P (dimension W/m²) and illuminated area A: I ( ) ( λ) H IP λ = P A The dimensionless IPCE is defined as ratio of generated photoelectrons n e (λ) to incident photons n ph (λ): n IPCE ( λ) = n e ph ( λ) ( λ)
Light Spectra Analysis -13- The number of photoelectrons n e (λ) can be easily calculated from the photocurrent I(λ) and time t using the elementary charge q e. I ( ) ( λ) t ne λ = q The number of photons n ph (λ) is given by the irradiance P (dimension W/m²) multiplied by the illuminated area A and time t divided by the energy of a photon. The latter is determined by its wavelength λ, the speed of light c and the Planck constant h: e n ph ( λ) = P A t c h λ Using these expressions IPCE calculates to: IPCE ( λ ) = ( λ) I h c P A λ q e 2.4.4. The Wavelength / Wavenumber Toggle By means of the wavelength / wavenumber toggle you may switch the X axis from wavelength dimension to inverse wavelength dimension wavenumber [cm -1 ]. Fig. 11 Photocurrent spectrum of an OSC vs. wavelength (left) and vs. wavenumber (right)
Light Spectra Analysis -14-2.4.5. X/Y Autoscale / Manual Scale Function Clearing the checkbox for X- or Y-autoscaling will open the appropriate input box for manual settings. Fig. 12 Manual scaling in X (left) and in Y (right) direction
Light Spectra Analysis -15-3. Cursor Analysis Functions 3.1. Entering the cursor mode Touching the graphic display field with the mouse pointer and pressing the confirmation mouse button will enter the cursor mode (Fig. 13 & Fig. 14). Fig. 13 Entering the cursor mode by positioning the mouse pointer in the graphic display field and confirming with the right hand mouse button Fig. 14 Cursor mode. Moving the mouse left or right will change the wavelength of interest. The cursor will follow the amplitude course of the selected curve. If more than one curve is selected, scroll up /down will move the cursor to the Y-position of the next/previous spectrum.
Light Spectra Analysis -16-3.2. Zoom- and Analysis Functions 3.2.1. Mark Wavelength Sections Fig. 15 A wavelength section in cursor mode, marked by two cursor positions. By means of two clicks with the mouse confirm button you may mark a certain wavelength section for zoom- or analysis operation (Fig. 15). 3.2.2. Zoom Re-Zoom Operation Touching the z key while in cursor mode will expand the marked wavelength section to the full display panel. Inversely the r key causes a re-zoom operation and the marked cursor positions will be cancelled.
Light Spectra Analysis -17-3.2.3. Analyse Marked Wavelength Sections Fig. 16 Analysis of a selected spectral section of an emittance spectrum. Pressing a for analysis will open the analysis page and offer print-, graphic- or text export for the analyzed data from the selected wavelength range (Fig. 16 to Fig. 18). Fig. 17 Analysis output of an emittance spectrum as vector graphic
Light Spectra Analysis -18- Fig. 18 Analysis output of an absorbance spectrum as a bitmap