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An active illumination microscope provides simultaneous acquisition of multi-contrast images such as bright-field, dark-field, and differential phase-contrast using various illumination patterns. We experimentally demonstrate the multi-contrast images of structural modifications produced in glass by a femtosecond laser. The multi-contrast images of structural modifications were obtained by changing illumination patterns with a projector for microscopic contrast enhancement. The refractive index change and scattering damage produced in BK7 glass were identified by differential phase-contrast images and dark-field images. We can enhance the direction of contrast in the imaging of modifications by changing the rectangular illumination pattern. Multi-contrast microscopy by different illumination pattern is a technique for in situ monitoring of modifications by femtosecond laser pulses in transparent materials.

For requirements of light source on tiny parts measurement system, this paper puts forward a single wavelength LED to design uniform light of multiple ring. According to detection principle of tiny parts, the design method of ring source is set up, as well as luminescence radiation calculation model of LED ring source. The calculation model of light illumination properties of LED ring array light source are set up and analyzed, light illumination calculation functions of ring source are derived; based on design characteristics of ring source, illumination model and calculation principles of uniform light source are analyzed, the derivation process is established in detail. Through calculation and experimental analysis, illumination uniformity distribution curve of LED ring array light source were given under different detecting plane and the horizontal distance of LED, and the contrast results of illumination uniformity in the x axis and y axis also were given, the results show that when the distances between detecting plane and LED plane are 80 mm and 100 mm, illumination uniformity of LED ring array light source can reach 0.96.

In traditional optical microsopy the uniformity of off-axis illumination is poor. In this paper we propose a novel LED optical system for near-field illumination in microscopy. The system includes a LED light source, an optical collimator and a freeform, micro-reflective lens array. The Monte Carlo method is used to simulate the system. The simulation results show that the illumination uniformity can be better than 85% in the observation zone. The optical system can be put at the side of the main optical axis of the microscope. The illumination uniformity is not varied when the observation distance changes so it has good stablilty.

We present an improved structured illumination configuration for structured illumination microscopy (SIM) based on spatial light modulator. Precise phase shifts and rotation of illumination fringes can be dynamically controlled using a spatial light modulator. The method is different from the conventional illumination configuration that are based on interference of ±1 diffractive order light. The experimental setup requires less optical elements making it compact, reliable, and suitable for integration. The method has been applied in the standing-wave total internal reflection fluorescent microscopy. High lateral resolution of sub-100 nm was achieved in single directional resolution enhancement experiments.

Photometric stereo estimates the surface normal given a set of images acquired under different illumination conditions. To deal with diverse factors involved in the image formation process, recent photometric stereo methods demand a large number of images as input. We propose a method that can dramatically decrease the demands on the number of images by learning the most informative ones under different illumination conditions. To this end, we use a deep learning framework to automatically learn the critical illumination conditions required at input. Furthermore, we present an occlusion layer that can synthesize cast shadows, which effectively improves the estimation accuracy. We assess our method on challenging real-world conditions, where we outperform techniques elsewhere in the literature with a significantly reduced number of light conditions.

Capturing high quality image is very important in the active automatic optical inspection system. Besides camera, image quality mainly is affected by the illumination. A design method of structure illumination, which is comprised of light emitting diodes (LEDs) arrays, is proposed in this paper. And especially, these LEDs arrays are not in the same plane. First, the single LED irradiating model is built based on analyzing its irradiance properties. Second, the case of two LEDs irradiating is set as an example to analyze superposition properties of the same color light for any specified point's light brightness based on the built single LED irradiating model, and then the irradiating model of LEDs is developed. Third, the structure illumination design method of LEDs ring arrays is illustrated based on the proposed design model of illumination uniformity. Especially, the illumination design method is decomposed into two subproblems to simplify the design process, which can reduce the design difficulty. Experimental results show that the light intensity deviation is less than 3.78% by the proposed illumination design method, which validates the effectiveness of the proposed method.

To meet the uniform dose exposure in optical lithography, it is desirable to get uniform illumination in the scanning direction on wafer for the step-and-scan lithographic system. We present a flat Gauss illumination for the step-and-scan lithographic system in this paper. Through flat Gauss illumination in scanning direction, pulse quantization effect could be reduced effectively. Correspondingly, the uniformity of the reticle and wafer is improved. Compared with the trapezoid illumination, flat Gauss illumination could keep the slit edge fixed, and pulse quantization effect will not be enhanced. Moreover flat Gauss illumination could be obtained directly without defocusing and blocking, which results in high energy efficiency and high throughput of the lithography. A design strategy for flat Gauss illumination is also proposed which offers high uniformity illumination, fixed slope and integral energy of flat Gauss illumination in different coherence factors. The strategy describes a light uniform device which contains first microlens array, second microlens array, one-dimensional Gauss diffuser and a Fourier lens. The device produces flat Gauss illumination directly at the scanning slit. The design and simulation results show that the uniformity of flat Gauss illumination in two directions satisfy the requirements of lithographic illumination system and the slope. In addition, slit edge of flat Gauss illumination does not change.

The paper considers the possibility of a flat light field creation (light raster) of a large size by laser scanning at a distance of several tens of meters with angular sizes equal to 20º×4º. It is shown that the filling of such size raster by light is possible with the use of a single laser. The uniformity of light raster illumination is achieved by choice of parameters for collimating and scanning optical systems, the speed of light spot movement on the line and frame, turnover frequency of frames, spot light overlap factor. We present findings that give the possibility to obtain relatively uniform raster illumination at laser scanning and the filling of large size raster with low power laser light from the radiation source.

In many illumination problems, the beam pattern needed and/or some geometrical constraints lead to very asymmetric design conditions. These asymmetries have been solved in the past by means of arrangements of rotationally symmetric or linear lamps aimed in different directions whose patterns overlap to provide the asymmetric prescriptions or by splitting one single lamp into several sections, each one providing a part of the pattern. The development of new design methods yielding smooth continuous free-form optical surfaces to solve these challenging design problems, combined with the proper CAD modeling tools plus the development of multiple axes diamond turn machines, give birth to a new generation of optics. These are able to offer the performance and other advanced features, such as efficiency, compactness, or aesthetical advantages, and can be manufactured at low cost by injection molding. This paper presents two examples of devices with free-form optical surfaces, a camera flash, and a car headlamp.

In recent years, high-resolution microscopy using structured illumination has been practically applied for fluorescent bio-imaging. However, there is a large amount of speckle noise in reflected- and scattered-light images, because structured illumination is typically generated by laser-beam interference. Hence, this high-resolution imaging technique cannot be effectively used in industrial applications. In this study, we attempted to generate structured illumination using two-beam interference of low-coherence light for high-resolution and low-speckle imaging. First, we constructed an optical system consisting of a Michelson interferometer configured in such a manner that it achieved zero optical path-length difference and allowed the interference fringes to be manipulated. Then, we confirmed that the generated structured illumination width corresponded to the coherence length of the light source. As a final result of the resolution improvement experiment, the narrow sample pitch of 0.4 μm was successfully resolved beyond the diffraction limit of 0.74 μm with relatively less speckle noise.

In this research, an overlapped illumination model was newly proposed for designing a freeform LED lens with a uniform illuminance distribution on its illuminating plane. Based on the proposed model and conventional illumination models, freeform lenses were designed and their performances and tolerances were compared. As a result of the tolerance analysis about thickness change in lens, position, size change, central direction change of light emission and characteristic change in LED source. This proposed model and divergent illumination model are similar to the performance about central direction change of light emission in LED source. but the uniformity illumination value in this proposed model is more remarkably value than it in divergent illumination model about characteristic change in LED source

We propose an elliptical mirror-based total-internal-reflection fluorescence (e-TIRF) microscopy with shadowless illumination and adjustable penetration depth. The elliptical mirror is used to produce a hollow-cone illumination with all azimuthal directions and a large range of incident angle, so as to attenuate the potential shadow effects when utilizing a single-direction illumination, such as asymmetries and low contrast. The experiment demonstrates that the e-TIRF method can realize shadowless imaging with symmetric intensity distribution. Meanwhile, the penetration depth of e-TIRF can be theoretically adjusted from 58 nm to 250 nm by adjusting the size of the aperture or the position of an opaque mask. This method extends the minimum penetration depth, which is useful for high axial resolution.

This study reports an application of a fiber-optic LED-based illumination system to solve an inverse problem in optical measurements of characteristics of a single-mode fiber. The illumination system has the advantages of low temporal coherence, high intensity, collimation, and thermal stability of the emission spectrum. The inverse analysis is investigated to predict the values of the diameter and refractive index of a single-mode fiber and applies to the far field scattering pattern in the vicinity of a polychromatic rainbow. As the inversion possibility depends considerably on the properties of the incident radiation, a detailed discussion is provided on both the specification of the illumination system as well as preliminary characteristics of the produced radiation. The illumination system uses a direct coupling between a thermally-stabilized LED junction and a plastic optical fiber, which transmits light to an optical collimator. A numerical study of fiber-to-LED coupling efficiency helps to understand the influence of lateral and longitudinal misalignments on the output power.

Dark field illumination in high throughput colony selection device is reported in this paper. It improves the contrast of image in the premise of uniform illumination. Three important factors including angular distribution of light radiation, number of LED circle array and distance between the target and the LED circle source were analyzed, which affect illumination uniformity of dark field illumination. The simulation result shows that the illumination uniformity is 93.16% when the angular distribution of light radiation is 75°, the number of LED circle array is 3, and the distance between the target and the LED circle source is 61mm. In addition, Experimental system was set up in order to test designed dark field illumination, which matches with the project requirement and simulated results very well.

A novel approach to incorporate surface information into the ray mapping method is proposed. This method calculates irradiance at the physical optical surface and target plane instead of the usually flat or hemispherical dummy surface, resulting in a mapping relationship which reflects the true geometry of the system. The robustness of the method is demonstrated in an extreme example (60° off axis) where the uniformity is as high as 82%.

General approaches to realize higher sensitivity in optical inspection system are using shorter wavelength including UV and higher NA for objective lens. Extreme performances of imaging and illumination systems in a situation of wellmatched to each other are inevitable for the further effort on an effective optical detection of fine defects in patterned wafer. This study focused on the dark field illumination systems satisfying hi areal uniformity and concentration efficiency for the specific conditions of non-symmetric illumination area and critical slanted angle. Three different types of anamorphic dark field illumination systems namely, Far-field Areal Illumination (FAI), Near-field Areal Illumination (NAI) and Farfield Linear Illumination (FLI), are designed and evaluated by brightness, uniformity and concentration efficiency of beam intensity.

Structured illumination microscopy (SIM) doubles the lateral resolution and produces optically-sectioned images. In SIM, the illumination system is modified in order to illuminate the sample by a structured pattern. Previously, axially-localized high-contrast sinusoidal patterns generated using a slit-prism illumination system based on a Fresnel biprism were investigated. In this contribution, we propose a Wollaston prism to replace the Fresnel biprism and produce the corresponding 3D structured illumination pattern. In this study, both optical elements are illuminated by the light emerging from an axial point source. Our results show that the benefits of using a Wollaston prism instead of a Fresnel biprism are twofold: (1) there is no envelope modulation perturbing the sinusoidal patterns and thereby reducing their visibility, and (2) the region of interference fringes is significantly larger than the one created by the Fresnel biprism.

A novel 3D patterned illumination system using an incoherent light source has potential benefits for structured illumination microscopy (SIM) such as lowered intensity requirements and tunable modulating frequency. The illumination system, based on a coherent source, a set of parallel slits and a beam-splitting Fresnel biprism, generates localized interference fringes with a continuously-tunable range of lateral and axial spatial frequency combinations that are not easily accessible using other existing methods of generating structured illumination. Here we present adaptation of this system to a wide-field fluorescence microscope that tests its suitability for SIM imaging. Numerical simulations and experimental data are used to compare theoretical and practical system properties. Results demonstrate that theoretically predicted illumination properties can be used to select system design parameters and accurately produce specific illumination properties at the microscope sample plane. As part of an imaging system, this illumination approach may improve the applicability of super-resolution SIM to a greater variety of samples.

Using freeform lenses to construct uniform illumination systems is important in light-emitting diode (LED) devices. In this paper, the energy feedback design is used for freeform lens (EFFL) constructions by solving a set of partial differential equations that describe the mapping relationships between the source and the illumination pattern. The simulation results show that the method can overcome the illumination deviation caused by the extended light source (ELS) problem. Furthermore, a uniformity of 95.6% is obtained for chip-on-board (COB) compact LED devices. As such, prototype LEDs manufactured with the proposed freeform lenses demonstrate significant improvements in luminous efficiency and emission uniformity.

This chapter explores the relationship between light, illumination and colour with respect to human response, and questions the validity of the current numerical systems of measurement. Mankind has evolved over many, many, thousands of years under daylight; that is light directly from the sun and by reflection. Daylight has a broad, relatively smooth spectral distribution embracing the full colour range of the human visual system. Electric illumination has been available for barely 100 years and has developed considerably from the humble incandescent light bulb through discharge sources and now solid state light emitting devices but its measurement systems are based on a much narrower spectral distribution, agreed internationally in 1924, the CIE Vλ distribution. Systems of colour measurement came much later, but are considered insufficiently accurately for modern light sources. Possible alternatives are considered. It also explores the human response to light and colour with respect to environment design.

It is well known for structured illumination microscopy (SIM) that the lateral resolution by a factor of two beyond the classical diffraction limit is achieved using spatially structured illumination in wide-field fluorescence microscope. In the state of art SIM systems, grating patterns are generally generated by physical gratings or by spatial light modulators such as digital micro mirrors (DMD), liquid crystal displays (LCD). In this study, using a combination of LCD and ground glasses, size controlled randomized speckle patterns are generated as an illumination source for the microscope. Proof of concept of using speckle illumination in SIM configuration is tested by imaging fixed BPAE cells. MOE (Min. of Education, S’pore) Published version

An automatic optical inspection system for detecting local defects on specular surfaces is presented. The system uses an image display to produce a sequence of structured diffuse illumination patterns and a digital camera to acquire the corresponding sequence of images. An image enhancement algorithm, which measures the local intensity variations between bright- and dark-field illumination conditions, yields a final image in which the defects are revealed with a high contrast. Subsequently, an image segmentation algorithm, which compares statistically the enhanced image of the inspected surface with the corresponding image for a defect-free template, allows separating defects from non-defects with an adjusting decision threshold. The method can be applied to shiny surfaces of any material including metal, plastic and glass. The described method was tested on the plastic surface of a car dashboard system. We were able to detect not only scratches but also dust and fingerprints. In our experiment we observed a detection contrast increase from about 40%, when using an extended light source, to more than 90% when using a structured light source. The presented method is simple, robust and can be carried out with short cycle times, making it appropriate for applications in industrial environments. (C) 2016 Elsevier Ltd. All rights reserved., This research is sponsored by the Portugal Incentive System for Research and Technological Development. Project in co-promotion no 36265/2013 (Project HMIExcel - 2013-2015)., info:eu-repo/semantics/publishedVersion

For the special use demands of ultraviolet warning cameras, the structures, distortion balances and the consistency of image plane illumination of ultra wide-angle optical systems were analyzed. An ultraviolet optical system with a large field of view of 120 and a large relative aperture of 1/2 was designed. The system is a double imaging configuration with the spectral range from 0.254 m to 0.272 m. By using inverse telephoto structure, its back working length is 7.48 mm. A quasi-telecentric optical system was selected to improve the illumination uniformity for off-axis and on-axis view fields. Then, by choosing optical materials and distributing the focal powers reasonably, the optical system was optimized. The experiments demonstrate that the system is characterized by smaller imaging distortion and uniform image plane illumination, the dispersion spot diameter is smaller than 63.5 m, and the relative distortion at 0.71 field of view, the relative illumination uniformity for off-axis and on-axis view fields are less than 20% and 10%, respectively. The structure of the whole system is compact and feasible, and is suitable for ultraviolet warning cameras.

Indirect illumination with light-emitting diodes (LEDs) and diffusers is widely applied in various fields that require uniform illumination. In this paper, a design of diffuse reflection freeform surface is proposed. Based on the Lambertian characteristic of LEDs and ideal diffuse surface, a mathematical model is developed. Nonlinear algebraic equations are established by redistributing the energy emitted from LEDs to the illuminated scene for uniform illumination. Solving these equations numerically, the outline of the diffuse surface is obtained. Finally, by using ray tracing software TracePro, the simulation result shows that the irradiance uniformity of the detection plane is above 95% with high accepted tolerance.

LED lighting has a significant edge over the traditional incandescent lighting in terms of illuminating brightness, illuminating stability and energy consumption. However, if directly being applied to lamps and other illumination devices without undergoing optical processing, LED illumination chips can hardly give full play to its performance. Therefore, it is necessary to study secondary design of high-power LED with even illumination. Proceeding from illumination principles and characteristics of LED, this paper explores design of the projector to realize even illumination of the high-power LED. It is hoped that this research can provide theoretical references for LED lighting design.

Based on the observation of the data measured, the illumination distribution of single LED is set to follow Gaussian function, and with this hypothesis, two forms of light array are analyzed on their illumination distribution. The law of Spyro is used to optimize space between LED in array. Comparison and analysis of the two kinds of array arrangement are given for getting the uniform illumination. The general design method and the calculation example of LED array to produce uniform illumination are also given in this paper. Keywords: Plane light source, Gauss function fitting, LED light source, Uniform illumination

In order to study the influence by non-uniformity of illumination on testing performance of optical measurement system, the causes of non-uniformity were analyzed. We constructed the relationship model between interval distance of LED light source and illumination. The distribution of illumination with different intervals of LED were simulated. Then relationship model between viewing-field angle at object plane of optical system and illumination was established. Influence of viewing-field angle at object plane on distribution of illumination was studied. The experimental results indicate that non-uniform light source and wide viewing-field angle are two main causes for non-uniformity in optical imaging system. Larger interval distance of LED or viewing-field angle will result in non-uniformity of illumination.

This paper studies the measurement of illumination parameters from a bright product. We are making use of diffuse reflection characteristics of the integrating sphere, which can greatly reduce the measurement error caused by the shape of the light, the divergence angle, and different location on the detector. In this way we can measure the intensity of the light source accurately, and the measurement accuracy less than 5%.

Replacing traditional light sources with light-emitting diode (LED) light modules is a global trend, especially for underwater illumination. The light intensity is dispersed evenly at all emission angles in traditional underwater light sources that use the radiative transfer model, resulting in the inclusion of scattering factors in the attenuation coefficient. The high directionality of LED light source modules causes the light intensity transfer in water to vary according to varying emission angles. This renders traditional underwater optical transfer theory irrelevant as an underwater LED light module design reference. Therefore, this study constructs an underwater LED light source transfer model using the light-field average cosine and the light transfer scattering probability method, and imports the LED luminous intensity distribution curve (LIDC) and axial luminous intensity. Experimental results showed that the illumination intensity of the underwater LED illumination module was less than 10% of the simulation. Therefore, this design method can be used to design the required illumination light modules for different underwater environments. Finally, the LED light module has been used for under water fish attractor lighting and enhanced the illumination zone efficiency (m 3 per Watt) of 81% compared to the traditional high intensity discharge (HID) underwater fish attractor lamp.

Near infrared laser illumination is in low illumination situation,using near infrared lasers as the light source for long-distance target active lighting.Because of the laser generation mechanism,the optical system tolerance,atmospheric turbulence and other factors,the laser intensity spatial distribution on the target plane is not uniform,which has great impact on image resolution and tracking accuracy.In this paper,the area surrounded by normalized PSD(power spectral density) is adopted to evaluate the near infrared laser illumination intensity uniformity.Using this method,different near infrared laser illuminator′s uniformity evaluation parameters are studied,in the same work condition.The results verify the reasonableness of the laser power spectrum as an evaluation parameter.

Specular and strong reflections are the main problems encountered during part image defect inspection of shiny or highly reflective surfaces. In this letter, we propose an improved illumination method for defect inspection. A diffuse light source is designed based on the physics analysis of light reflection. The distribution of intensity is simulated according to a known model to verify the illumination uniformity of the source. Experiments show that defect expressivity when using the proposed illumination method has a better performance. The optical model is not only suitable for the defect detection of metal balls but also for the defect detection of planes and cylinders.

An improved machine vision illumination system was proposed that used general LED light sources.General LED light source with the package type of surface mounted device,or chip on board was used in the new system.A uniform light system was used to make sure the illumination uniformity when the new system switched different light colors of general lighting LED light source.Based on the edge light principle of the non-imaging theory,a method of simultaneous multiple surfaces was used to design the universally uniform optical system.The system on the premise of maintaining the optical system being fixed can switch multiple light sources without specially designed uniform light source.It ensures the uniformity of target surface illumination and expands the illumination subsystem′s light color range.The comparison between several groups of Monte Carlo ray tracing simulation shows that the general illumination light sources meeting the requirements of sizes can be integrated into the system as long as the light source used in the new system meets the design requirements of sizes;the nonuniformity of the illuminated area will not lead to the decrease of distinguishing degree;so the proposed light source is suitable for the machine vision system that requires not too high energy efficiency and high uniformity of illuminance of the target area.

This letter shows that the human eye fundus tissue has higher reflectivity at the near-infrared (NIR) wavelength, and that some aberrations exist at the pre-optical system from cornea to vitreous. We design a NIR fundus camera with inner focusing, which can be applied to the -10 D to 10 D range of vision and has the advantage of ensuring the stability of image when is focused. Considered as Liou's eye aberration model, we correct the integrated aberration to ensure a 100 lp/mm resolution when we complete the assembly and calibration of the fundus camera. Kohler illumination is also applied to obtain uniform fundus illumination. Moreover, we put forward a novel method for stray light elimination based on polarization switch, which inhibits ghost image formation near the focal plane when the illumination beam is reflected by the eyepiece surface. The result shows that this method is effective in ensuring an illumination uniformity of 80%, with the advantage of simple structure and easy assembly.

A new laser illumination system was designed based on the analysis of regular homogenization technology. It was widely used in the field of security without sunlight and other lighting. The new laser illumination system used eccentric motor to drive a light shaping scatterer to vibrate at a frequency that faster than the electronic shutter of cameras, making multiple light superimposed in integration time to form a uniform illumination effect. The laser illumination system can eliminate interference fringes and laser speckles, and realize the purpose of homogenization illumination. Experimental results show that the new laser illumination system makes the energy efficiency reach up to 90% and the illumination uniformity reach up to 94% in the effective area. The new laser illumination system improves the uniformity of illumination and utilization rate of laser energy, thus improves the image quality of the illuminated target.

Retinal images are obtained by simultaneously illuminating and imaging the retina, which is achieved using a fundus camera. This device meets low light illumination of the fundus with high resolution and reflection free images. Although the current equipment presents a sophisticated solution, it is complex to align due to the high number of off-axis components. In this work, we substitute the complex illumination system by a ring of LEDs mounted coaxially to the imaging optical system, positioning it in the place of the holed mirror of the traditional optical design. We evaluated the impact of this substitution regarding to image quality (measured through the modulation transfer function) and illumination uniformity produced by this system on the retina. The results showed there is no change in image quality and no problem was detected concerning uniformity compared to the traditional equipment. Consequently, we avoided off-axis components, easing the alignment of the equipment without reducing both image quality and illumination uniformity.

The theory and application of RGB-LED based mixed-color illumination system for use in machine vision and optical microscopy systems are presented. For machine vision system, relationship of various color sources and output image sharpness is discussed. From the viewpoint of gray scale images, evaluation and optimization methods of optimal illumination for machine vision are concluded. The image quality under monochromatic and mixed color illumination is compared. For optical microscopy system, demand of light source is introduced and design thoughts of RGB-LED based mixed-color illumination system are concluded. The problems need to be solved in this field are pointed out.

We explain how to concentrate light simultaneously at multiple selected volumetric positions by means of a 4D illumination light field. First, to select target objects, a 4D imaging light field is captured. A light field mask is then computed automatically for this selection to avoid illumination of the remaining areas. With one-photon illumination, simultaneous generation of complex volumetric light patterns becomes possible. As a full light-field can be captured and projected simultaneously at the desired exposure and excitation times, short readout and lighting durations are supported.

The optical microscopy is one of the most powerful tool in the analysis of biological systems. The usual transmitted light microscope uses a white light lamp as source, what sometimes does not bring optimal results, making it necessary to introduce filters to change some illumination properties like the color temperature or the color itself. There is, of course, an intrinsic limitation on the use of filters that is the lack of an analogical control on the illumination properties and a practical limitation that depends on the number of available filters. To address this need, we developed an illumination system based on (Red, Green and Blue) RGB LEDs, were the microscope operator can control the intensity of each one independently and manually. This paper details the developed system and describes the methods used to compare quantitatively the images acquired while using the standard white light illumination and the images obtained with the developed system. To quantify the contrast, we calculated the relative population standard deviation for the intensities of each channel of the RGB image. This procedure allowed us to compare and understand the major advantages of the developed illumination system. All analysis methods have shown that a contrast enhancement can be obtained under the RGB LEDs light. The presented illumination allowed us to visualize the structures in different samples with a better contrast without the need of any additional optical filters.

This paper presents the performance analysis of a freeform lens that can be used as a first or secondary optic when combined with a point or an extended light source. The light source can be an LED. The purpose of the optic is to increase uniformity of illumination within the footprint. The analysis is performed on the freeform lens when combined with: (i) an isotopic or a Lambertian point light source (ii) an isotropic or a Lambertian extended light source. This paper shows that through a design based on energy mapping between a light source and a target plane it is possible to achieve uniform illumination. The ZEMAX ray tracing simulation shows that the uniformity reduces gradually when the size of the light source increases. The results indicate that a freeform lens combined with a point source can generate over 95% uniformity.

Live-cell and live-tissue imaging using fluorescence optical microscopes presents an inherent trade-off between image quality and photodamage. Spatially-controlled illumination microscopy (SCIM) aims to strike the right balance between obtaining good image quality and minimizing the risk of photodamage. In traditional imaging, illumination is performed with a spatially-uniform light dose resulting in spatially-variable detected signals. SCIM adopts an alternative imaging approach where illumination is performed with a spatially-variable light dose resulting in spatially-uniform detected signals. The actual image information of the biological specimen in SCIM is predominantly encoded in the illumination profile. SCIM uses real-time spatial control of illumination in the imaging of fluorescent biological specimens. This alternative imaging paradigm reduces the overall illumination light dose during imaging, which facilitates prolonged imaging of live biological specimens by minimizing photodamage without compromising image quality. Additionally, the dynamic range of a SCIM image is no longer limited by the dynamic range of the detector (or camera), since it employs a uniform detection strategy. The large dynamic range of SCIM is predominantly determined by the illumination profile, and is advantageous for imaging both live and fixed biological specimens. In the present review, the concept and working mechanisms of SCIM are discussed, together with its application in various types of optical microscopes.

LED-illuminated structured light sources with shortest system length are realized using arrayed microprojectors. Flux scaling requires array area enlargement only. Large depth of focus of the individual projectorlets enables projection onto strongly tilted or curved screens.