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Articles 31 - 58 of 58
Full-Text Articles in Optics
Optical Patterning Of Photopolymerisable Materials, Kevin Trainer, Kevin Wearen, Dimana Nazarova, Izabela Naydenova, Vincent Toal
Optical Patterning Of Photopolymerisable Materials, Kevin Trainer, Kevin Wearen, Dimana Nazarova, Izabela Naydenova, Vincent Toal
Conference Papers
Holographic recording is an effective approach for photopolymer surface patterning. It has been previously utilised in acrylamide-based photopolymers and a spatial frequency limit of 200 l/mm has been observed. We report the successful inscription of submicrometer resolution patterns. The spatial frequency response has been extended to 1550 l/mm by introduction of thermal post recording treatment. Initial results from the optical patterning utilising a spatial light modulation (SLM) reveal that the amplitude of the photoinduced surface relief structures is larger in comparison to the amplitude obtained by holographic recording.
Ocular Microtremor Laser Speckle Metrology, Mohammed Al-Kalbani, Emilia Mihaylova, Niamh Collins, David Coakley, Gerard Boyle, Vincent Toal
Ocular Microtremor Laser Speckle Metrology, Mohammed Al-Kalbani, Emilia Mihaylova, Niamh Collins, David Coakley, Gerard Boyle, Vincent Toal
Conference Papers
Ocular Microtremor (OMT) is a continual, high frequency physiological tremor of the eye present in all subjects even when the eye is apparently at rest. OMT causes a peak to peak displacement of around 150nm-2500nm with a broadband frequency spectrum between 30Hz to 120Hz; with a peak at about 83Hz. OMT carries useful clinical information on depth of consciousness and on some neurological disorders. Nearly all quantitative clinical investigations have been based on OMT measurements using an eye contacting piezoelectric probe which has low clinical acceptability. Laser speckle metrology is a candidate for a high resolution, non-contacting, compact, portable OMT …
Out-Of-Plane Vibration Analysis With A Transmission Holographic Optical Element Based Electronic Speckle Pattern Interferometer, Viswanath Bavigadda, Vincent Toal, Raghavendra Jallapuram, Emilia Mihaylova
Out-Of-Plane Vibration Analysis With A Transmission Holographic Optical Element Based Electronic Speckle Pattern Interferometer, Viswanath Bavigadda, Vincent Toal, Raghavendra Jallapuram, Emilia Mihaylova
Conference Papers
A simple electronic speckle pattern interferometer (ESPI) using a transmission holographic optical element (THOE) is presented. The THOE is designed to create a speckled reference beam in the interferometer. It is a transmission hologram of a diffusely transmitting glass plate A specific requirement for the fabrication of the THOEs is for them to be recorded at one wavelength at which the recording material is photosensitive and reconstructed using a near infrared laser diode which can be current modulated for phase shifting purposes. A partially reflective glass plate provides illumination of the object along the normal to its surface, ensuring that …
Holographic Recording In Charged Photopolymerisable Nanocomposites, Temenujka Yovcheva, Ivanka Vlaeva, Simeon Sainov, Izabela Naydenova, Vincent Toal, Svetlana Mintova
Holographic Recording In Charged Photopolymerisable Nanocomposites, Temenujka Yovcheva, Ivanka Vlaeva, Simeon Sainov, Izabela Naydenova, Vincent Toal, Svetlana Mintova
Conference Papers
Self – processing photopolymers have a large number of different applications due to their versatile properties as holographic recording materials. A significant effort has been directed towards the development of photopolymers for holographic data storage [1, 2], holographic sensors [3], holographic optical elements [4] and display holograms [5]. The Centre for Industrial and Engineering Optics has been developing acrylamide based photopolymers for the last decade [6-8]. The main parameters requiring improvement in these types of photopolymers are their dynamic range and their mechanical stability during the holographic recording. Recently we have successfully used zeolite nanoparticles as dopants in order to …
Optical Properties Of Charged Polymer With Nano-Sized Zeolite Inclusions, Temenujka Yovcheva, Izabela Naydenova, Ivanka Vlaeva, Rosen Todorov, Vincent Toal, Simeon Sainov
Optical Properties Of Charged Polymer With Nano-Sized Zeolite Inclusions, Temenujka Yovcheva, Izabela Naydenova, Ivanka Vlaeva, Rosen Todorov, Vincent Toal, Simeon Sainov
Conference Papers
The optical characteristics of photopolymer films doped with nanoparticles are studied. The investigated systems consist of a soft polymer matrix containing porous zeolite nanoparticles with concentrations varied in the range from 0wt.% to 7wt.%. 40μm thick layers are obtained by casting the photopolymer nanocomposite solution on glass substrates. The corona charging influence on the transmission spectra and on the surface and the effective refractive index of the dry layers is investigated.
Optical Properties Of Photopolymerisable Nanocomposites Containing Zeolite Nanoparticles, Izabela Naydenova, Tzvetanka Babeva, Elsa Leite, Nitesh Pandey, Temenujka Yovcheva, Svetlana Mintova, Vincent Toal
Optical Properties Of Photopolymerisable Nanocomposites Containing Zeolite Nanoparticles, Izabela Naydenova, Tzvetanka Babeva, Elsa Leite, Nitesh Pandey, Temenujka Yovcheva, Svetlana Mintova, Vincent Toal
Conference Papers
Acrylamide-based photopolymerisable nanocomposites containing three different types of nanozeolites – Si-MFI, AlPO and BEA, were studied. The influence of the porous nanoparticles on the average refractive index, optical scattering, holographic recording properties and shrinkage were characterised.
A Single Beam Data Writing Process For Holographic Data Storage, Suzanne Martin, Denis Bade, Izabela Naydenova, Vincent Toal
A Single Beam Data Writing Process For Holographic Data Storage, Suzanne Martin, Denis Bade, Izabela Naydenova, Vincent Toal
Conference Papers
A concept is described that could allow Holographic Data Storage with angular multiplexing using, uniquely, only one data writing beam; pre-recorded ‘seed’ gratings are illuminated with one writing beam in order to produce a data grating.
Recent And Emerging Applications Of Holographic Photopolymers And Nanocomposites, Izabela Naydenova, Pavani Kotakonda, Raghavendra Jallapuram, Tsvetanka Babeva, Denis Bade, Suzanne Martin, Vincent Toal, Svetlana Mintova
Recent And Emerging Applications Of Holographic Photopolymers And Nanocomposites, Izabela Naydenova, Pavani Kotakonda, Raghavendra Jallapuram, Tsvetanka Babeva, Denis Bade, Suzanne Martin, Vincent Toal, Svetlana Mintova
Conference Papers
Sensing applications of holograms may be based on effects such as change in the spacing of the recorded fringes in a holographic diffraction grating in the presence of an analyte so that the direction of the diffracted laser light changes, or, in the case of a white light reflection grating, the wavelength of the diffracted light changes. An example is a reflection grating which swells in the presence of atmospheric moisture to indicate relative humidity by a change is the colour of the diffracted light. These devices make use of the photopolymer’s ability to absorb moisture. In a more versatile …
Hoe-Based Espi Systems, Emilia Mihaylova, Viswanath Bavigadda, Raghavendra Jallapuram, Vincent Toal
Hoe-Based Espi Systems, Emilia Mihaylova, Viswanath Bavigadda, Raghavendra Jallapuram, Vincent Toal
Conference Papers
Electronic speckle pattern interferometry (ESPI) is a full-field measurement technique, capable of displaying vibrational mode shapes. Two electronic speckle pattern interferometers using reflection holographic optical elements (RHOEs) are presented. In the first ESPI system the RHOE is designed to create the speckled reference beam. A partially reflective glass plate provides illumination of the object along the normal to its surface, ensuring that the system is sensitive only to out-of-plane displacement of the object. It is demonstrated that the HOE-based system can be used for vibration measurements. Phase shifting can be implemented for fringe analysis. In the second ESPI system a …
Whole Field Out-Of-Plane Vibration Analysis With A Hoe-Based Espi System, Emilia Mihaylova, Viswanath Bavigadda, Raghavendra Jallapuram, Vincent Toal
Whole Field Out-Of-Plane Vibration Analysis With A Hoe-Based Espi System, Emilia Mihaylova, Viswanath Bavigadda, Raghavendra Jallapuram, Vincent Toal
Conference Papers
Electronic speckle pattern interferometry (ESPI) is a full-field measurement technique, capable of displaying vibrational mode shapes. A simple optical set-up for an ESPI system using a holographic optical element (HOE) is presented. The HOE is designed to create a speckled reference beam in the interferometer. A partially reflective glass plate provides illumination of the object along the normal to its surface, ensuring that the system is sensitive only to out-of-plane displacement of the object. It is demonstrated that the HOE-based system can be used for vibration measurements. Phase shifting can be implemented for fringe analysis. A big advantage of the …
Hologram-Based Humidity Indicator For Domestic And Packaging Applications, Izabela Naydenova, Raghavendra Jallapuram, Vincent Toal, Suzanne Martin
Hologram-Based Humidity Indicator For Domestic And Packaging Applications, Izabela Naydenova, Raghavendra Jallapuram, Vincent Toal, Suzanne Martin
Conference Papers
A passive indicator for Relative Humidity based on a photopolymer recorded hologram has been developed. The indicator works on the principle that the wavelength reconstructed by a reflection hologram is dependent on the spacing between the fringe planes of the hologram. As the Relative Humidity changes, the hologram swells or shrinks and the apparent colour of the reconstructed image changes. The response time, operational range and reversibility of the indicator have been studied in a controlled humidity environment. Response times from less than a minute to tens of minutes depending on the holograms physical properties have been measured. Indicators with …
Characterization Of An Acrylaminde Based Photopolymer For Fabrication Of Liquid Crystal Devices, Pavani Kotakonda
Characterization Of An Acrylaminde Based Photopolymer For Fabrication Of Liquid Crystal Devices, Pavani Kotakonda
Conference Papers
Photopolymers are increasingly interesting as new materials for the fabrication of electro optical liquid crystal devices. Photoinduced surface relief gratings in dry, self developing acrylamide based photopolymers can be used to align liquid crystals (LCs) as an alternative to the rubbing technique. These optically recorded surface relief patterns can be used to fabricate electro-optical switchable LC Bragg gratings. An investigation of the dependence of photoinduced surface relief gratings on recording intensity and thickness of the photopolymer layer is reported. The surface relief gratings were filled with E7 LCs and a switchable LC diffraction grating was fabricated.
Replay At Optical Communications Wavelengths Of Holographic Gratings Recorded In The Visible, Vincent Toal, Maurice Whelan, Alberto Volcan, Izabela Naydenova, Suzanne Martin
Replay At Optical Communications Wavelengths Of Holographic Gratings Recorded In The Visible, Vincent Toal, Maurice Whelan, Alberto Volcan, Izabela Naydenova, Suzanne Martin
Conference Papers
In this paper we report on holographic diffraction gratings recorded at visible light wavelength, which can be probed at telecommunication wavelengths. The recording material is an easily prepared, self-processing photopolymer, all of whose components are water soluble. Transmission gratings of various types, namely unslanted, slanted, totally internally reflecting and Bragg gratings were all fabricated. Diffraction efficiencies at telecommunications wavelengths compare favourably with those obtained in visible light.
Comparison Of Three Electronic Speckle Pattern Shearing Interferometers Using Photopolymer Holographic Optical Elements., Emilia Mihaylova, Izabela Naydenova, Vincent Toal, Suzanne Martin
Comparison Of Three Electronic Speckle Pattern Shearing Interferometers Using Photopolymer Holographic Optical Elements., Emilia Mihaylova, Izabela Naydenova, Vincent Toal, Suzanne Martin
Conference Papers
Three electronic speckle pattern shearing interferometers (ESPSI) using photopolymer holographic gratings to produce the sheared image are presented. In the first ESPSI system two holographic gratings are used. The gratings are placed between the object and an imaging lens in front of the CCD camera. In the second ESPSI system one grating is used in combination with a sheet of ground glass. The sheared images on the ground glass are further imaged onto a CCD camera. In the third ESPSI system only one grating is used - it is placed in front of the object. The image and the sheared …
Characterization Of An Acrylamide Based Photopolymer For Fabrication Of Liquid Crystal Devices, Pavani Kotakonda, Izabela Naydenova, Suzanne Martin, Vincent Toal
Characterization Of An Acrylamide Based Photopolymer For Fabrication Of Liquid Crystal Devices, Pavani Kotakonda, Izabela Naydenova, Suzanne Martin, Vincent Toal
Conference Papers
Photopolymers are increasingly interesting as new materials for the fabrication of electro optical liquid crystal devices. Photoinduced surface relief gratings in dry, self developing acrylamide based photopolymers can be used to align liquid crystals (LCs) as an alternative to the rubbing technique. These optically recorded surface relief patterns can be used to fabricate electro-optical switchable LC Bragg gratings. An investigation of the dependence of photoinduced surface relief gratings on recording intensity and thickness of the photopolymer layer is reported. The surface relief gratings were filled with E7 LCs and a switchable LC diffraction grating was fabricated.
Holographic Recording In Nanoparticle-Doped Photopolymer, Izabela Naydenova, Hosam Sherif, Svetlana Mintova, Suzanne Martin, Vincent Toal
Holographic Recording In Nanoparticle-Doped Photopolymer, Izabela Naydenova, Hosam Sherif, Svetlana Mintova, Suzanne Martin, Vincent Toal
Conference Papers
A nanoparticle-doped acrylic photopolymer is characterised as a material for holographic recording. The influence of nanoparticles on the photopolymer dynamic range, dynamics of recording, temporal stability and mechanical stability in terms of shrinkage has been studied. The dynamics of recording and the temporal stability are investigated by real time monitoring of the build up of diffraction gratings of spatial frequencies of 200 to 2000 l/mm. The shrinkage has been characterised by recording slanted transmission gratings and observation of the change in the Bragg angle.
Two Way Diffusion Model For The Recording Mechanism In A Self-Developing Dry Acrylamide Photopolymer, Suzanne Martin, Izabela Naydenova, Raghavendra Jallapuram, Robert Howard, Vincent Toal
Two Way Diffusion Model For The Recording Mechanism In A Self-Developing Dry Acrylamide Photopolymer, Suzanne Martin, Izabela Naydenova, Raghavendra Jallapuram, Robert Howard, Vincent Toal
Conference Papers
In our most recent study [1] diffusion constants were measured in the simplified monoacrylamide version of a dry acrylamide based photopolymer holographic recording material developed in the Centre for Industrial and Engineering Optics. In this paper we report diffusion constants for the commonly used photopolymer formulation, which also contains the crosslinker bisacrylamide. A physical model for the recording mechanism is proposed which explains the two way diffusion observed in both systems, and is in agreement with much of the previously observed behaviour of the material, particularly in regard to dependence of diffraction efficiency growth on spatial frequency and persistence of …
Holographic Recording Of Patterns In Thin Film Acrylamide-Based Photopolymer, Izabela Naydenova, Kotakonda Pavani, Emilia Mihaylova, Katia Loudmer, Suzanne Martin, Vincent Toal
Holographic Recording Of Patterns In Thin Film Acrylamide-Based Photopolymer, Izabela Naydenova, Kotakonda Pavani, Emilia Mihaylova, Katia Loudmer, Suzanne Martin, Vincent Toal
Conference Papers
A study of the light induced surface relief modulation in thin photopolymer layers is reported. Due to the nature of the photopolymer used no additional post-processing is required after holographic recording. An investigation of the dependence of the amplitude of the photoinduced relief modulation on different parameters of recording such as spatial frequency, intensity of the beams and times of exposure has been carried out. The surface relief modulation is characterized by white light interferometry. Photopolymer layer thickness ranges from 1-5m. A model of the mechanism of surface relief formation is proposed on the basis of the measured dependencies. A …
Simple Electronic Speckle Pattern Shearing Interferometer With A Holographic Grating As A Shearing Element, Emilia Mihaylova, Izabela Naydenova, Suzanne Martin, Vincent Toal
Simple Electronic Speckle Pattern Shearing Interferometer With A Holographic Grating As A Shearing Element, Emilia Mihaylova, Izabela Naydenova, Suzanne Martin, Vincent Toal
Conference Papers
An optical set-up for electronic speckle pattern shearing interferometry (ESPSI) using a photopolymer diffractive optical element as a shearing element, is presented. A laser beam illuminates the object at an angle to the normal to the object surface. The holographic diffraction grating is placed in front of the object. The zero and the first order of diffraction form the image and the sheared image of the object. The images are imaged onto the CCD camera, whose optical axis coincides with the normal to the object surface. The field of view is limited only by the dimensions of the photopolymer plate. …
Study Of An Acrylamide-Based Photopolymer For Use As A Holographic Data Storage Medium, Hosam Sherif, Izabela Naydenova, Suzanne Martin, Colm Mcginn, G Berger, C Denz, Vincent Toal
Study Of An Acrylamide-Based Photopolymer For Use As A Holographic Data Storage Medium, Hosam Sherif, Izabela Naydenova, Suzanne Martin, Colm Mcginn, G Berger, C Denz, Vincent Toal
Conference Papers
An acrylamide-based photopolymer formulated in the Centre for Industrial and Engineering Optics has been investigated with a view to further optimisation for holographic optical storage. Series of 15 to 30 gratings were angularly multiplexed in a volume of the photopolymer layers with different thickness at a spatial frequency of 1500 lines/mm. Since the photopolymer is a saturable material, an exposure scheduling method was used to exploit the entire dynamic range of the material and allow equal strength gratings to be recorded. From this investigation the photopolymer layer’s M/# was determined with regard to the recording geometry used. The temporal stability …
Electronic Speckle Pattern Shearing Interferometry For Nondestructive Testing Of Thermal Sprayed Alloy Coatings, Yueqiang Xue, David Kennedy, Emilia Mihaylova
Electronic Speckle Pattern Shearing Interferometry For Nondestructive Testing Of Thermal Sprayed Alloy Coatings, Yueqiang Xue, David Kennedy, Emilia Mihaylova
Conference Papers
Thermal sprayed coatings have wide engineering applications. There now exists a wide range of destructive and nondestructive testing (NDT) methods for surface coating inspections. This paper describes an application of Electronic Speckle Pattern Shearing Interferometry (ESPSI) for NDT of thermal sprayed surface coatings. In contrast to other conventional methods such as eddy current, ultrasonic or X-ray, ESPSI allows fast and large survey area inspection. Experimental results of shearographic measurements are presented. Thermal sprayed coatings were tested using ESPSI. Delaminations of the coatings were detected and the fringe patterns were captured using this method. It is shown that the shearography technique …
Investigation Of Polymerization Rate In An Acrylamide-Based Photopolymer Using Raman Spectroscopy, Raghavendra Jallapuram, Izabela Naydenova, Hugh Byrne, Suzanne Martin, Robert Howard, Vincent Toal
Investigation Of Polymerization Rate In An Acrylamide-Based Photopolymer Using Raman Spectroscopy, Raghavendra Jallapuram, Izabela Naydenova, Hugh Byrne, Suzanne Martin, Robert Howard, Vincent Toal
Conference Papers
Diffusion models predict that polymerization and diffusion rates are the key factors that control the dynamics and the final properties of a holographic grating recorded in a photopolymerizable material. Diffusion rates during the initial phase of holographic recording have already been studied and reported. We now report the investigation of the polymerization rate in an acrylamide-based photopolymer using Raman spectroscopy. The polymerization rate constant was estimated by monitoring the intensity of the characteristic Raman peaks at 1284 cm-1 corresponding to the bending mode of CH vinyl bond in acrylamide and 1609 cm-1 corresponding to the carbon-carbon double bond (C=C) in …
A Compact Electronic Speckle Pattern Interferometry System Using A Photopolymer Reflection Holographic Optical Element, Guntaka Tulasi Sridhar Reddy, Raghavendra Jallapuram, Vincent Toal, Izabela Naydenova, Suzanne Martin, Svetlana Mintova
A Compact Electronic Speckle Pattern Interferometry System Using A Photopolymer Reflection Holographic Optical Element, Guntaka Tulasi Sridhar Reddy, Raghavendra Jallapuram, Vincent Toal, Izabela Naydenova, Suzanne Martin, Svetlana Mintova
Conference Papers
A simple and compact electronic speckle pattern interferometry system using a reflection holographic optical element is presented. The reflection holographic optical element is recorded on an acrylamide based photopolymer formulated and prepared at the Centre for Industrial & Engineering Optics. Light intensity of 40mW/cm2 with an exposure time of 60 seconds was used in fabricating the holographic optical element. The vibration mode patterns of a 4 cm diameter thin circular sheet of brass metal attached to a 4 cm diameter paper cone loud speaker are presented.
Application Of Photopolymer Holographic Gratings, Emilia Mihaylova, Izabela Naydenova, Hosam Sherif, Suzanne Martin, Vincent Toal
Application Of Photopolymer Holographic Gratings, Emilia Mihaylova, Izabela Naydenova, Hosam Sherif, Suzanne Martin, Vincent Toal
Conference Papers
Two optical set-ups for electronic speckle pattern shearing interferometry (ESPSI) using photopolymer diffractive optical elements are presented. Holographic gratings are recorded using an acrylamide based photopolymer material. Since the polymerisation process occurs during recording, the holograms are produced without any development or processing. In both ESPSI systems the photopolymer gratings are used to shear the image. In the first ESPSI system only one grating is used in combination with a sheet of ground glass. The distance between the grating and the ground glass can be used to control the amount of the shear. The sheared images on the ground glass …
Investigation Of The Photoinduced Surface Relief Modulation In Acrylamide-Based Photopolymer, Izabela Naydenova, Emilia Mihaylova, Suzanne Martin, Vincent Toal
Investigation Of The Photoinduced Surface Relief Modulation In Acrylamide-Based Photopolymer, Izabela Naydenova, Emilia Mihaylova, Suzanne Martin, Vincent Toal
Conference Papers
A surface relief diffraction grating is inscribed in acrylamide photopolymer by holographic recording with spatial frequency below 300 l/mm. The periodic surface modulation appears in addition to a volume phase holographic grating. Due to the nature of the presented photopolymerisable material the gratings are induced by light only and no post-processing is required. An investigation of the dependance of the amplitude of the photoinduced relief modulation on spatial frequency of recording and on sample thickness has been carried out utilising white light interferometry. A model of the mechanism of surface relief formation is proposed on the basis of the measured …
Electronic Speckle Pattern Shearing Interferometry Using Photopolymer Diffractive Optical Elements For Vibration Measurements, Emilia Mihaylova, Izabela Naydenova, Suzanne Martin, Vincent Toal
Electronic Speckle Pattern Shearing Interferometry Using Photopolymer Diffractive Optical Elements For Vibration Measurements, Emilia Mihaylova, Izabela Naydenova, Suzanne Martin, Vincent Toal
Conference Papers
Electronic speckle pattern shearing interferometry (ESPSI) is superior to Electronic speckle pattern interferometry (ESPI) when strain distribution, arising from object deformation or vibration, need to be measured. This is because shearography provides data directly related to the spatial derivatives of the displacement. Further development of ESPSI systems could be beneficial for wider application to the measurement of mechanical characteristics of vibrating objects. Two electronic speckle pattern shearing interferometers (ESPSI) suitable for vibration measurements are presented. In both ESPSI systems photopolymer holographic gratings are used to shear the images and to control the size of the shear. The holographic gratings are …
Spatial Frequency Response Of Acrylamide Based Holographic Photopolymer, Raghavendra Jallapuram, Izabela Naydenova, Vincent Toal, Suzanne Martin, Robert Howard
Spatial Frequency Response Of Acrylamide Based Holographic Photopolymer, Raghavendra Jallapuram, Izabela Naydenova, Vincent Toal, Suzanne Martin, Robert Howard
Conference Papers
It has been shown that photopolymers are useful in holographic optical elements [1] and holographic interferometry [2]. However, the list of potential applications increases greatly if reflection holography is possible. Reflection holography requires a material that has the potential to record high spatial frequencies. Here we studied the spatial frequency response of an acrylamide based dye sensitized holographic photopolymer. We have investigated the effect of molecular weight of the binder and concentration of crosslinking monomer on diffusion using real time monitoring of the holographic grating formation. The effect of uniform pre-exposure on diffusion was also investigated. We have also demonstrated …
Application Of A Photopolymer Material In Speckle Pattern Shearing Interferometry, Emilia Mihaylova, Izabela Naydenova, Suzanne Martin, Vincent Toal
Application Of A Photopolymer Material In Speckle Pattern Shearing Interferometry, Emilia Mihaylova, Izabela Naydenova, Suzanne Martin, Vincent Toal
Conference Papers
A new application of a photopolymer diffractive optical element in electronic speckle pattern shearing interferometer (ESPSI) is presented. In the first stage a holographic grating is recorded using an acrylamide based photopolymer material. Since the polymerisation process occurs during recording, the holograms are produced without any development or processing. In the second stage the holographic grating is used to produce the two sheared images in an ESPSI configuration. A ground glass screen following the grating serves the purpose of eliminating unwanted diffraction orders. The distance between the grating and the ground glass can be used to control the amount of …