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This paper examines the feasibility of producing multiplexed Bragg gratings for use as diffractive optical elements (DOEs) by coherent optical replication of a surface-relief phase grating into thick-film photosensitive materials. The use of such DOEs in light guide plates (LGPs) for optical imaging systems ensures energy-efficient light input into and output from LGPs and allows one to minimise their weight and size. We present simulation results for the interference structure fabrication process and recording of a series of multiplexed diffraction gratings in photosensitive materials.

Optical sensors of linear displacements with diffraction gratings serving as the measurement scales are investigated. A method of stabilization of the phase difference of quadrature measurement signals, consisting in the use of an analyzing scale with a special structure, is proposed. A design of an optical encoder based on the method is proposed. Mathematical simulation of the phase shift of the measurement signals as a function of the parameters of the diffraction grating is performed, and the results of the simulation are presented. The RCWA method is used to simulate the passage of radiation through the optical system. The optimal parameters of the structure of the analyzing scale are calculated. Experimental investigations of a mock-up of the encoder are performed and results of measurements of the phase difference of the measurement signals are presented.

Phase shifts of light in orders of diffraction grating for the interference linear displacement sensor are considered. Using the phase diffraction grating with given geometric parameters of the surface relief allows one to stabilize phase relations in optical signals and in resulting signals outputted from the displacement sensor. Based on the mathematical simulation data, technically feasible parameters of the grating relief are proposed for creating the required phase shifts between diffracted beams leading to quadrature modulation. It helps reaching the required measurement accuracy with nanometric resolution.

Diffraction waveguides are widely used in augmented reality devices as information display systems for the introduction of data into the human visual field in order to supplement information about the world around us. This paper formulates the principles of radiation conversion in diffraction waveguides made of photo-thermo-refractive glass on the basis of multiplexed volume holographic gratings, and the advantages and disadvantages of high spectral-angular selectivity are analyzed. In the optical scheme, each of the superimposed volume holographic gratings in the diffraction waveguide forms a corresponding part of the composite angular field of view of the augmented reality device. A proposed mathematical model based on angular multiplexing made it possible to synthesize the diffraction optical element for a new type of diffraction waveguide made from photo-thermo-refractive glass and to create a prototype with an angular resolution of at least 3.0 ± 0.5′, with a brightness change in the image of less than 20% and with a composite angular field of view of 32°.

This paper describes the experiment on multiplexing recording using a phase mask to create augmented reality waveguides. The study is distinguished by the application of photo-thermo-refractive glass as both holographic and substrate materials. The presented approach allows us to obtain the diffraction efficiency above 15% in each of the multiplexed gratings for sevenfold recording. The images output with the manufactured planar waveguide prototype are presented.

Multiplexed volume holographic gratings are used as spectral and angular optical couplers for augmented reality displays and high-power laser applications. Paper presents modeling approach and recording experiments to create couplers in photo-thermo-refractive glass.

An augmented reality display based on a planar waveguide made in photo-thermo-refractive glass had been demonstrated. The monolithic integration of multiplexed volume Bragg gratings with the waveguide platform provided in/out-coupling and image transmission from a portable projector. Design and calculation of the grating configuration was performed. The optical replication method was simulated and implemented for manufacturing the multiplexed coupling elements. Resulted field of view was limited by the projection system of the prototype, however can be expanded beyond 50o.

In interference linear optical displacement sensors, precise position information is provided by the pair of quadrature sine and cosine signals while measuring scales moves along each other. One of these scales is a transmission diffraction grating that combines beam splitter function with phase retardation element. Precalculated parameters of that gratings based not only on diffraction efficiency analysis but phase relations in orders as well, helps to stabilize quadrature signals in the displacement sensor. This paper set the optimization condition in terms of phase shifts of light in diffraction orders influencing phase imbalance. To simulate the conversions of optical radiation by diffraction gratings, a rigorous coupled waves analysis was used. The phase imbalance of the obtained quadrature signals is estimated depending on the uncertainties of influencing parameters.

This presentation is devoted to methods of multiplex volume Bragg diffraction gratings production. One of last developed and most promising volume photosensitive material of a such gratings is a photo-thermo-refractive glass. Low photosensitivity and high cost of suitable lasers for this material is a huge disadvantage. This makes traditional interference method of Brag gratins production difficult to implement. Thus a new method or a new vision of previous methods of a Bragg grating production required. A scheme of optical replication of easy-to-earn relief-phase grating into volume medium is considered. A mathematical modelling of interference field forming in volume medium during this process and attained diffraction efficiency of Bragg grating is performed. Experimental research at pulsed and CW lasers setups were carried out and achieved samples of multiplex Bragg grating described. A method of vibration-independent and low-sensitivity-material-suitable optical replication for production of multiplex volume Bragg gratings is described.

In interferential linear displacement sensors, accurate information about the position of the reading head is calculated out of a pair of quadrature (sine and cosine) signals. In double grating interference schemes, diffraction gratings combine the function of beam splitters and phase retardation devices. Specifically, the reference diffraction grating is located in the reading head and regulates the phase shifts in diffraction orders. Measurement diffraction grating moves along with the object and provides correspondence to the displacement coordinate. To stabilize the phase imbalance in the output quadrature signals of the sensor, we propose to calculate and optimize the parameters of these gratings, based not only on the energetic analysis, but along with phase relationships in diffraction orders. The optimization method is based on rigorous coupled-wave analysis simulation of the phase shifts of light in diffraction orders in the optical system. The phase properties of the reference diffraction grating in the interferential sensor are studied. It is confirmed that the possibility of quadrature modulation depends on parameters of static reference scale. The implemented optimization criteria are formulated in accordance with the signal generation process in the optical branch. Phase imbalance and amplification coefficients are derived from Heydemann elliptic correction and expressed through the diffraction efficiencies and phase retardations of the reference scale. The phase imbalance of the obtained quadrature signals is estimated in ellipticity correction terms depending on the uncertainties of influencing parameters.

The paper considers optical linear encoder based on diffraction gratings. A method of quadrature signals phase shift stabilization based on the application of head grating with specific structure is proposed. The optical scheme of position encoder based on measuring head grating with specific structure is developed and described in this paper. Mathematical modeling of quadrature signals phase shift depending on grating parameters is carried out. Based on the simulation, we propose optimal parameters of head grating structure. Design process and results for head gratings are presented in the paper.

Linear displacement encoders are necessary in field of machine tools, metrology and electronic industry. Those devices provide nanometric resolution when constructed according to the interferometric scheme. Mathematical modeling of signal transfer process into its optical system to analyze an interference field is described. Signal intensity depending on a small displacement of moving grating phase shift correlations is considered. A sample model of the linear optical encoder is developed based on the optical scheme under research.

The paper describes a stable method for multiplexed recording of the Bragg diffraction gratings for waveguides using a phase mask. Diffraction waveguides in this experiment were made of photo-thermo-refractive glass. Two types of the phase mask are considered: surface and volume. Their comparison is based on diffraction characteristics of manufactured single and multiplexed Bragg gratings. The experimental results showed the advantage of surface phase mask application. To confirm the efficiency of the proposed method, diffraction waveguides was successfully fabricated and integrated in see-through near-eye display.

That paper focuses on indirect measurements of the diffraction gratings by analyzing their scattered distribution. The method is based on pre-calculated numerical dependencies of the energy characteristics. The comparison of measured diffraction efficiency values with numerical simulations provide the inverse measurements of the profile height. Presented research belongs to the field of scatterometry of high-resolution diffraction optical elements. The concept is tested with polymeric sinusoidal relief. Considered phase diffraction gratings have interest in field of linear displacement encoders.

The work is devoted to the calculation of the optimal parameters of diffraction gratings for input and output of radiation from the holographic lightguides for augmented reality glasses. Two main stages can be distinguished, namely: the calculation of the grating’s period in each of the optical lightguides to obtain a multicolor image in a large field of view, and the calculation of the height of the relief profile (to maximize the diffraction efficiency).

Optical position encoders working according to the interference method consists of a measurement scale and a measuring head moving along each other. The scale has a reflection diffraction grating on its surface and the measuring head has a transmission diffraction grating with same period inside. Laser light passing and diffracting through these two gratings creates an interference signal on an optical detector. Decoding of the interference signal phase allows to determinate current position. Known optical position encoders use complex optical schemes and some phase optical elements to form several quadrature signals with different phase for higher encoder accuracy. Previously we researched such kind of schemes [1, 2]. In this paper we propose to use a common optical scheme without phase elements but with a complex structured measuring head grating for this purpose to simplify an optical scheme and alignment requirements. The optical scheme of position encoder based on measuring head grating with specific structure is research and described in this paper.

That paper focuses on diffraction gratings consisting some period failures provided by the errors of the electronbeam lithography method. Samples of lithographic phase gratings were tentatively analyzed to describe that technological errors. A small linear modulation of the period or a joint of a frame edges can cause not only diffraction efficiency losses but also functional breakdown. A simulation of the diffraction of a monochromatic wave at the described diffraction phase structures is carried out. Described diffraction gratings have interest in field of linear displacement encoders.

Optical position encoders working according to the interference method consists of a measurement scale and a measuring head moving along each other. The scale has a reflection diffraction grating on its surface and the measuring head has a transmission diffraction grating with same period inside. Laser light passing and diffracting through these two gratings creates an interference signal on an optical detector. Decoding of the interference signal phase allows to determinate current position. Known optical position encoders use complex optical schemes and some phase optical elements to form several quadrature signals with different phase for higher encoder accuracy. Previously we researched such kind of schemes [1, 2]. In this paper we propose to use a common optical scheme without phase elements but with a complex structured measuring head grating for this purpose to simplify an optical scheme and alignment requirements. The optical scheme of position encoder based on measuring head grating with specific structure is research and described in this paper.

The article describes a new optical scheme of noncontact sensor for measuring linear displacement - linear encoder. This sensor is an optical device in which the measurement of displacement is performed by analyzing the optical signal, which pass through two diffraction gratings, one of which is moved relative to the other. The optical signal is obtained by the diffraction of light in these diffraction gratings and subsequent interference of diffracted beams. Often this type of sensors are multi-channel devices with symmetrically positioned of detectors. This scheme is proposed to use a multisection phase mask that allows to make a small-sized sensor. Sections of this multi-section phase mask are the optical windows and they made the final interference signals to be shifted relative to each other in phase. The number of sections in the multi-section phase mask can be varied. Estimated sufficient number of sections is four or more.

Optical position encoder consists of movable coding grating and fixed analyzing grating. Light passing and diffracting through these two gratings creates interference signal on optical detector. Decoding of interference signal phase allows to determinate current position. Known optical position encoders use several accurate adjusted optical channels and detectors to gather several signals with different phase for higher encoder accuracy. We propose to use one optical channel with several-section analyzing diffraction grating for this purpose to simplify optical scheme and adjusting requirements. Optical scheme of position encoder based on four-section analyzing diffraction grating is developed and described in this paper.

The optical scheme of holographic printer for obtaining of holographic stereograms with an increasing field of view is proposed. Conventional holographic printers allow obtaining holographic stereograms with the field of view up to 90°. Proposed scheme allows increasing field of view up to 120°. The optical scheme is based on a diffuser and a diffraction optical element, the high-aperture diffractive lens. The experience of using the composite holographic lens and the amplitude diffractive lens based on a binary Fresnel zone plate as a high-aperture diffractive lens is described. Samples of high-aperture diffractive lens with f-number f/0.3 are obtained and investigated. Samples of holographic stereograms are obtained using samples of high-aperture diffractive lens.

The fundamental methods for analyzing the parameters of diffraction gratings (DGs) are presented. The features of the application of DGs as measurement scales in a linear-displacement sensor system are analyzed. A method and quality criteria for monitoring the parameters of real samples of measurement scales are proposed. These criteria generalize all diffraction efficiencies that affect the formation of quadrature signals in the system of an interferometric linear-displacement sensor.

An optical position encoder uses two difraction gratings in a measurement scale and measuring head for generating cosine measurment signals. This report is about special subperiod structuring of thees gratings for generating of two signals with quadrature phase shift for better the resolution of an optical position encoder.