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Experimental demonstration of a flexible DOE loop with wideband speckle suppression for laser pico-projectors

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Abstract

The compact and straightforward construction of a pico-projector using an original method for speckle suppression via a simple 1D diffractive optical element (DOE) structure on a loop of flexible film with tracked motion is demonstrated. The 1D-DOE structure is based on binary pseudorandom sequences. The method requires very little energy and space and can decrease speckle noise to levels below the detection sensitivity of the human eye. Large speckle suppression coefficients and low speckle contrasts are obtained for blue, green, and red lasers. Speckle suppression efficiency will be further significantly improved by optimization of the DOE structure and film material.

© 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

1. Introduction

For developing truly portable IT portals, large portable displays are needed. The best solution is a pico-projector because it does not require a large screen. The pico-projector is also the best solution for portable personal movie cinemas [1–3]. For reducing speckles and generating high-quality pictures from a small portable projector, a full-picture 2D pico-projector [3] is the best option, as the long exposure time for each pixel means that it has the greatest potential for realizing significant speckle reduction. The key requirements for the design of a pico-projector are small device size, high energy efficiency, and high picture quality.

Lasers are one of the most efficient light sources for producing high-quality beams with definite polarization [4]. Their use in projectors allows the building of small, energy-efficient devices, and laser projectors can project high-quality pictures [5]. However, images created by a laser beam are strongly modulated by speckle noise [6], which is the main hindrance to obtaining high-quality images via a laser pico-projector. Speckle noise may be quantified as speckle contrast, C, which is defined as

C=σ/Im,
where σ and Im are respectively the standard deviation and mean intensity in the image plane. The speckle suppression efficiency may be quantified using the speckle suppression coefficient k as

k=C0/C,

where C0 and C are respectively the speckle contrast before and after the application of a method for speckle suppression. Speckle suppression mechanisms are based on decreasing time, polarization, or spatial coherence of the illumination beam [6]. Methods for speckle suppression have been studied extensively [7–17]; the most promising method is based on a moving diffuser or a moving diffractive optical element (DOE) [8,12–14] placed inside an optical system [7]. The use of a moving diffuser or DOE inside an optical system in a plane conjugated to the screen is the simplest procedure for decreasing the spatial coherence of the laser beam [7], and it does not place any requirements on the properties of the laser. In the case of using the entire area of the modulator for a single color at each point in time, combining the images in the eye via a time sequence to produce a color picture, all the light of the beam is used to create each image; therefore, this approach exhibits the highest energy efficiency. Human eyes have a time resolution of approximately 0.04 s; therefore, at least 25 pictures should be created for each color (red, green, and blue) within 1 s to produce a high-quality movie without any side effects. The decorrelation length Δ of the DOE cannot be less than the optical resolution of the objective lens at the DOE plane, i.e., Δ > λ/NAin, where λ is the wavelength and NAin is the input numerical aperture of the objective lens. Taking a red laser as an example with NAin = 0.5, we obtain Δ > 1.3 μm. The speckle contrast below 0.04 is practically unnoticeable to the human eye [18]. The speckle contrast on screen can be evaluated as C = 1/sqrt(2M), where M is the number of uncorrelated speckle patterns during eye integration time [11]. It is not difficult to see that for full speckle suppression, at least 400 uncorrelated speckle fields are required to obtain speckle noise that is below the sensitivity limits of the human eye. Accordingly, a DOE shift S = 400 × 1.3 μm = 0.52 mm with a DOE speed of V ≈40 mm/s is required to obtain images that are pleasing to the eye. Most of the methods proposed for a moving DOE for speckle suppression [8] utilize vibration of the DOE. However, it is apparent from the DOE speed and amplitude estimated above that the amplitude and frequency of DOE vibrations required are too great to be realized in a pico-projector. A rotating spiral DOE has also been proposed for speckle suppression [9], which, however, is not appropriate for pico-projectors due to the large size of its rotated DOE (since only a small part of the DOE is illuminated by a laser beam). Therefore, the methods reported in the literature to date [7–17] are not suitable for adoption alongside pico-projector technology, either because of the required large device size or because of their high-energy-consumption DOE movements. Moreover, most of these methods cannot suppress laser speckles across the entire visible wavelength range.

In the present study, we propose a novel element called a flexible DOE loop with tracked motion, which is good from the perspectives of device size, DOE speed, and energy consumption. The flexible DOE loop is fabricated on a transparent film and rolled up in a loop. It is composed of several different 1D-DOE parts that are based on binary pseudorandom sequences [10,11] and have the same DOE structure except for the inclination angle with respect to the long side of the film. The flexible DOE loop with tracked motion constructs a dynamic 2D-DOE structure in real time by overlapping of a double-sided moving 1D DOE, and its energy and volume requirements are very small. We have theoretically and experimentally confirmed that the wavelength range for speckle suppression with a double-sided 1D DOE is wider than the visible range of our previous work [11,12]. The proposed mechanism of speckle suppression and the developed novel element provide the possibility to obtain very compact, highly energy efficient, speckle-free laser pico-projectors.

2. Proposed speckle suppression mechanism

An example of such a DOE loop is shown in Fig. 1, which consists of n DOE parts with inclination angles close to 45°, where n is the number of different 1D-DOE parts on the flexible DOE loop having different inclination angles. The DOE loop used in our experiments has three DOE parts, that is, n = 3. The 1D-DOE structure has N (pseudorandom binary code length) elementary cells of width T and with a period T0 = NT (see Fig. 1). The structure height h, which should provide a half-wavelength shift of the wave front, determines the wavelength band with good speckle suppression efficiency. The strip is rolled up in a loop and opposite sides of the DOE are glued together so that the DOE strip is transformed into a loop. In addition, a dynamic 2D-DOE structure is achieved due to the overlapping of different 1D-DOE structures via the tracked motion of the DOE loop.

 figure: Fig. 1

Fig. 1 (a) DOE structure on thin film, (b) DOE structure profile, and (c) scheme of DOE movement.

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The optical system of a pico-projector based on the developed DOE loop is proposed and shown in Fig. 2. Light from three lasers is collimated separately and combined into one beam by a dichroic beam combiner. Next, the laser beam is homogenized at the surface of the DOE loop with expansion of its diameter. Since the DOE loop is situated close to the last lens of the beam homogenizer, the optical scheme is robust against interference fringes. The DOE loop passes over two rotating spindles, one of which is connected to an electric motor. The inactive spindle is not fixed and can be moved along a slit; it is connected to a spring that pulls the flexible DOE loop. The DOE structure is on the outer surface of the DOE loop. The laser beam exiting the DOE loop passes through an optical modulator and illuminates the objective lens. The objective lens then projects the obtained image onto the screen. The distance between the two DOE parts on DOE loop results in a defocusing of the DOE on the screen. It was shown previously [19] that this defocusing over a wide range has no effect on speckle suppression efficiency. However, to avoid too much defocusing, this distance should be significantly smaller than the focal length of the objective lens of the projector.

 figure: Fig. 2

Fig. 2 Optical scheme of the laser pico-projector with the DOE loop.

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The overlap between the 1D-DOE structures on the front and back of the DOE loop creates a composite 2D-DOE structure. Figure 3 shows the scheme of the DOE movement and beam scanning as well as the composite 2D-DOE structure arising from the rotation of the loop. In Fig. 3(a), one red dash-dot line (parallel to the x axis) shows the direction of the DOE structure shift and another red dash-dot line shows the direction of composite 2D-DOE movement due to the relative shifts between the two 1D-DOE parts. Because the inclination angles are different between the two overlapping 1D-DOE structures, a shift along the y axis for the composite 2D DOE can be subtly achieved. Hence, the simple tracked motion of the DOE loop due to rotation of the spindles is similar to composite 2D-DOE movement with an inclination angle close to 45°, which was previously demonstrated to provide optimal speckle suppression efficiency [14]. The number of DOE structure parts n should be greater than two, to obtain overlap between two 1D-DOE structures with different inclination angles. Two lines defining the angle θ in Fig. 3(b) denote the shifts for the cases of DOE structures without and with a difference in inclination angles, respectively. The optimal angle θ for the 2D scanning of all elements of the composite 2D-DOE structure can be expressed as  sinθ2T022NT0=1/2N. The difference in inclination angles between two adjacent DOE parts is close to Δφ = θ / (n–1) for optimal speckle suppression, where DOE speed is determined by the smallest difference between the DOE inclination angles, i.e., Δφ. For the values of N = 31 and n = 3 used in our experiments, we obtain an optimal difference of inclination angles of Δφ = 0.46°. However, to decrease the required DOE speed, in our experiments we used a DOE loop with a slightly larger difference in inclination angle of Δφ = 0.6°.

 figure: Fig. 3

Fig. 3 (a) Scheme showing the movement of the front and back parts of the DOE structure (thin solid and dashed lines show the 1D-DOE structure on the front and back of the DOE loop, respectively) and (b) scheme of the composite 2D-DOE structure movement due to the relative shifts of the two-part 1D DOE for the case of DOE code length N = 4 (small squares denote the smallest elements of the DOE structure and large squares denote the period of the composite 2D DOE structure).

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Since lasers have definite polarization and the entire surface of the modulator is used by the laser beam, the highest possible energy efficiency for the 2D laser projector is accordingly obtained. From Fig. 2 is clear that speckle suppression devices can be placed very close to the optical modulator and therefore speckle suppression does not need additional space other than that required for the engine to rotate the DOE loop. Furthermore, because rotation of a flexible DOE loop consumes very small amounts of energy even during fast rotation, the engine size and energy consumption can also be very small. Hence, in principle, we obtained the most compact and energy-efficient laser projector.

A code length of N = 15 is sufficient to suppress the speckle to a level below the sensitivity of the human eye [12]. To achieve the most compact pico-projector, the smallest DOE element T should be as small as possible to enable the use of a small optical modulator and an objective lens with a short focal length. For estimating the minimal pico-projector size, the smallest element size T = 1.0 μm is assumed. Since at least one DOE period is needed for a single pixel for efficient speckle suppression, a pixel size of at least 15 μm should be used in the optical modulator for the proposed method of speckle suppression. Typical resolution of the optical modulator for pico-projectors is 1280 × 800 pixels; therefore, the size of the optical modulator should be at least 19.20 mm × 12.0 mm. The size of other optical components in the optical system of the pico-projector can also be estimated accordingly; hence, it is estimated that the size of the pico-projector can be a few tens of cubic centimeters, with the lenses having focal lengths of several centimeters. Since we assumed that all light falling on the optical modulator is utilized for the creation of the image, the optical scheme should have an optical efficiency close to the maximum possible for 2D projectors.

3. Experimental setup for measuring speckle suppression efficiency

For experimental verification of the novel method of speckle suppression as developed in this study, a DOE loop with a strip size of 7.5 mm × 75 mm with three diffraction structure parts was designed and fabricated; all three structures are the same except for their inclination angles (44.4°, 45°, and 45.6°). The scheme of the DOE structure is shown in Fig. 1. The DOE structures were produced based on binary pseudorandom M-sequences of length N = 31 with period T0 = 124 μm and elementary cell size T = 4 μm for experimental verification of our method.

Hot-embossing technology was used to manufacture the DOE. A photoresist layer with appropriate thickness was deposited on a silica substrate. First, the original DOE photoresist structure was formed in silica by photolithography. Next, a Ni stamper was manufactured by electroforming for the hot embossing. Initially, we planned to use a polyester (PET) film because of its mechanical, thermal, and optical properties. The calculated height of the DOE structure formed on the PET film was h = 360 nm, which in principle yields homogeneous speckle suppression over the entire visible range [11]. Unfortunately, our equipment was not capable of producing the DOE structure on the PET film since it would have required heating to a higher temperature. Hence, instead, we used a polyvinyl chloride (PVС) film to produce a flexible transparent DOE via hot embossing. However, as the refractive indexes of the PET and PVC films are rather different (1.65 and 1.52, respectively), the obtained DOE structure has a non-optimal height for the red laser.

Red (λ = 640 nm), green (λ = 520 nm), and blue (λ = 450 nm) lasers were used in the experiments for laser speckle suppression. An objective lens with a diameter D = 50.8 mm and a focal length of 175 mm was used in the experiments. The distances from the objective lens to screen and from the screen to the camera were 1650 mm and 1120 mm, respectively. The camera objective lens has a focal length of 25 mm, and the photodiode has a transverse size of 5.8 μm. The diameter of the input diaphragm of the camera was 1 mm. The integration time of the camera photodiode array was 0.235 s. The diameter of the spindles used to rotate the DOE loop was 4.5 mm.

In our experiments, we used the proposed system (see Fig. 2) to measure the speckle suppression effect separately for the blue, red, and green lasers. The speckle suppression efficiency was measured for two different DOE linear speeds—V1 = 8.2 cm/s and V2 = 11.6 cm/s—for all three lasers; the DOE shifts were 1.9 cm and 2.7 cm during the integration time of the photodiode (speckle averaging time). This is more than sufficient since the shift S = 2sqrt(2)NT0 = 1.076 cm is needed for achieving optimal speckle suppression for Δφ = θ / 2. The use of the DOE structure with T = 1 μm based on a code length of N = 15 requires that the DOE shift speed be one-sixteenth of V1 (a speed of approximately 5.8 mm/s) for achieving optimal speckle suppression. However, in a small laser projector, the speed of the DOE shift should be approximately the same as in our experiment since the intensity integration time of the human eye is approximately 0.04 s. In addition, lasers with different colors are used with different time intervals and therefore the intensity integration time is approximately 0.0113 s. Table 1 lists the obtained experimental speckle contrast and speckle suppression efficiency results.

Tables Icon

Table 1. Speckle-suppression efficiency (in %) for blue, green, and red lasers at two different DOE speeds.

Figure 4 shows the intensity distribution of the laser images on the screen before and after speckle suppression for the blue, green, and red lasers. Large speckle suppression coefficients of 14.7, 10, and 6.8 and small speckle contrasts of 2.5%, 3.9%, and 9% are obtained for blue, green, and red lasers, respectively. The smaller speckle suppression obtained for the red laser is due to the aforementioned non-optimal height of the DOE structure; this can be easily corrected by increasing the height of the DOE structure. It should be noted that we obtained practically the same speckle contrast and speckle suppression efficiency for two DOE speeds, in accordance with theoretical results [13], because both the speeds are greater than the minimal DOE speed required for achieving optimal speckle suppression.

 figure: Fig. 4

Fig. 4 Intensity distributions (top) and cross-sections of intensity distribution (bottom) before (left) and after (right) speckle suppression for (a) blue, (b) green, and (c) red laser beams.

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It should be noted that despite the strong speckle suppression, it is approximately two-fold less than that predicted theoretically. This method has a larger dispersion compared to that of similar speckle suppression mechanisms with different methods of DOE movement. There are four factors that could be responsible for the discrepancy between the theoretical and experimental results: DOE structure quality, inaccurate DOE shift, unwanted vibrations of DOE, non-constant angle between front and back DOE parts. Figure 5 shows the dependence of the speckle suppression coefficient for the blue laser on the shift length of the DOE during the intensity integration time obtained from experimental data and evaluated by theory. It is clear that for small shifts, we achieved good agreement between the theoretical and experimental results (the experimental data have a normal deviation of 0.5 for k). However, for greater shifts, the discrepancy between the theoretical and experimental results increases. An additional experiment that we carried out indicated that this discrepancy does not depend on the DOE speed, but it depends on the quality of the DOE sample and the shift length of the DOE during the intensity integration time. We assumed that the main cause of the discrepancy between the theoretical and the experimental data was the quality of the DOE structure. This assumption was supported by the presence of laser spot distortion on the screen in some locations. However, additional experiments should be carried out to definitely establish the origin of this discrepancy. To improve the experiment, we need to alter our DOE production technology to enable a change in the material of the DOE loop because PVC is too soft to be stable over extended periods of time.

 figure: Fig. 5

Fig. 5 Dependence of the speckle suppression coefficient k on the DOE shift (in units of length of the diagonal of the smallest element of the DOE) during time integration of the camera; the solid line represents experimental data and the dashed line represents the theoretical results.

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4. Conclusions

Our experimental results validated the effectiveness of a proposed method for speckle reduction based on a flexible DOE loop with a 1D-DOE structure consisting of pseudorandom binary sequences. The DOE loop has three different parts with slightly different inclination angles. The experimental results verified a strong speckle suppression using this approach. The simple tracked motion of the DOE loop results in a fast DOE shift and does not consume much energy. The proposed speckle suppression device is compact and efficient and is therefore extremely appropriate for portable image projectors as well as professional high-power laser projectors. The DOE on flexible film can be easily and inexpensively produced via hot embossing. Speckle contrasts below the detection sensitivity of the human eye were obtained for the blue and green lasers. The theoretical prediction and experimental results with different methods of DOE movement predict that the improvement in the DOE quality, DOE structure optimization, and improvement in accuracy of the DOE movement should facilitate significantly improved efficiency in speckle suppression (approximately two-fold) and decrease the speckle contrast below 4% for the red laser as well as the green and blue lasers.

Funding

Special Funding from “the Belt and Road” International Cooperation of Zhejiang Province (2015C04005); National Natural Science Foundation of China (NSFC) (61571399).

References

1. M. Freeman, M. Champion, and S. Madhavan, “Scanned laser pico-projectors: seeing the big picture (with a Small Device),” Opt. Photonics News 20(5), 28–34 (2009). [CrossRef]  

2. J. I. Trisnadi, C. B. Carlisle, and V. Monteverde, “Overview and applications of grating light valve TM based optical write engines for high-speed digital imaging,” Proc. SPIE 5348, 52–64 (2004). [CrossRef]  

3. R. Ryf, G. Chen, N. Basavanhally, M. Dinu, A. Duque, Y. L. Low, J. M. Wiesenfeld, Y. Shapiro, and R. Giles, “The Alcatel-Lucent microprojector: what every cell phone needs,” Bell Labs Tech. J. 14(3), 99–112 (2009). [CrossRef]  

4. B. Ismay, Semiconductor Laser Diode Technology and Applications (InTech, 1999), p. 376.

5. K. V. Chellappan, E. Erden, and H. Urey, “Laser-based displays: a review,” Appl. Opt. 49(25), F79–F98 (2010). [CrossRef]   [PubMed]  

6. J. W. Goodman, Speckle Phenomena in Optics (Roberts & Company, 2006).

7. L. Wang, T. Tschudi, T. Halldórsson, and P. R. Pétursson, “Speckle reduction in laser projection systems by diffractive optical elements,” Appl. Opt. 37(10), 1770–1775 (1998). [CrossRef]   [PubMed]  

8. S. Kubota and J. W. Goodman, “Very efficient speckle contrast reduction realized by moving diffuser device,” Appl. Opt. 49(23), 4385–4391 (2010). [CrossRef]   [PubMed]  

9. A. Lapchuk, G. A. Pashkevich, O. V. Prygun, V. Yurlov, Y. Borodin, A. Kryuchyn, A. A. Korchovyi, and S. Shylo, “Experiment evaluation of speckle suppression efficiency of 2D quasi-spiral M-sequence-based diffractive optical element,” Appl. Opt. 54(28), E47–E54 (2015). [CrossRef]   [PubMed]  

10. A. Lapchuk, A. Kryuchyn, V. Petrov, and V. Klymenko, “Optimal speckle suppression in laser projectors using a single two-dimensional Barker code diffractive optical element,” J. Opt. Soc. Am. A 30(2), 227–232 (2013). [CrossRef]   [PubMed]  

11. A. Lapchuk, O. Prygun, M. Fu, Z. Le, Q. Xiong, and A. Kryuchyn, “Dispersion of speckle suppression efficiency for binary DOE structures: spectral domain and coherent matrix approaches,” Opt. Express 25(13), 14575–14597 (2017). [CrossRef]   [PubMed]  

12. A. Lapchuk, G. Pashkevich, O. Prygun, I. Kosyak, M. Fu, Z. Le, and A. Kryuchyn, “Very efficient speckle suppression in the entire visible range by one two-sided diffractive optical element,” Appl. Opt. 56(5), 1481–1488 (2017). [CrossRef]  

13. A. Lapchuk, V. Yurlov, A. Kryuchyn, G. A. Pashkevich, V. Klymenko, and O. Bogdan, “Impact of speed, direction, and accuracy of diffractive optical element shift on efficiency of speckle suppression,” Appl. Opt. 54(13), 4070–4076 (2015). [CrossRef]  

14. J.-W. Pan and C.-H. Shih, “Speckle reduction and maintaining contrast in a LASER pico-projector using a vibrating symmetric diffuser,” Opt. Express 22(6), 6464–6477 (2014). [CrossRef]   [PubMed]  

15. T.-K.-T. Tran, X. Chen, Ø. Svensen, and M. N. Akram, “Speckle reduction in laser projection using a dynamic deformable mirror,” Opt. Express 22(9), 11152–11166 (2014). [CrossRef]   [PubMed]  

16. J. G. Manni and J. W. Goodman, “Versatile method for achieving 1% speckle contrast in large-venue laser projection displays using a stationary multimode optical fiber,” Opt. Express 20(10), 11288–11315 (2012). [CrossRef]   [PubMed]  

17. M. N. Akram, V. Kartashov, and Z. Tong, “Speckle reduction in line-scan laser projectors using binary phase codes,” Opt. Lett. 35(3), 444–446 (2010). [CrossRef]   [PubMed]  

18. Z. Cui, A. Wang, Z. Wang, S. Wang, C. Gu, H. Ming, and C. Xu, “Speckle suppression by controlling the coherence in laser Based projection systems,” J. Disp. Technol. 11(4), 330–335 (2015). [CrossRef]  

19. A. Lapchuk, V. Yurlov, G. A. Pashkevich, A. Prygun, A. A. Kryuchyn, and S. Shylo, “Impact of aberrations on speckle suppression efficiency on moving a DOE inside the optical system,” Displays 43, 1–8 (2016). [CrossRef]  

References

  • View by:

  1. M. Freeman, M. Champion, and S. Madhavan, “Scanned laser pico-projectors: seeing the big picture (with a Small Device),” Opt. Photonics News 20(5), 28–34 (2009).
    [Crossref]
  2. J. I. Trisnadi, C. B. Carlisle, and V. Monteverde, “Overview and applications of grating light valve TM based optical write engines for high-speed digital imaging,” Proc. SPIE 5348, 52–64 (2004).
    [Crossref]
  3. R. Ryf, G. Chen, N. Basavanhally, M. Dinu, A. Duque, Y. L. Low, J. M. Wiesenfeld, Y. Shapiro, and R. Giles, “The Alcatel-Lucent microprojector: what every cell phone needs,” Bell Labs Tech. J. 14(3), 99–112 (2009).
    [Crossref]
  4. B. Ismay, Semiconductor Laser Diode Technology and Applications (InTech, 1999), p. 376.
  5. K. V. Chellappan, E. Erden, and H. Urey, “Laser-based displays: a review,” Appl. Opt. 49(25), F79–F98 (2010).
    [Crossref] [PubMed]
  6. J. W. Goodman, Speckle Phenomena in Optics (Roberts & Company, 2006).
  7. L. Wang, T. Tschudi, T. Halldórsson, and P. R. Pétursson, “Speckle reduction in laser projection systems by diffractive optical elements,” Appl. Opt. 37(10), 1770–1775 (1998).
    [Crossref] [PubMed]
  8. S. Kubota and J. W. Goodman, “Very efficient speckle contrast reduction realized by moving diffuser device,” Appl. Opt. 49(23), 4385–4391 (2010).
    [Crossref] [PubMed]
  9. A. Lapchuk, G. A. Pashkevich, O. V. Prygun, V. Yurlov, Y. Borodin, A. Kryuchyn, A. A. Korchovyi, and S. Shylo, “Experiment evaluation of speckle suppression efficiency of 2D quasi-spiral M-sequence-based diffractive optical element,” Appl. Opt. 54(28), E47–E54 (2015).
    [Crossref] [PubMed]
  10. A. Lapchuk, A. Kryuchyn, V. Petrov, and V. Klymenko, “Optimal speckle suppression in laser projectors using a single two-dimensional Barker code diffractive optical element,” J. Opt. Soc. Am. A 30(2), 227–232 (2013).
    [Crossref] [PubMed]
  11. A. Lapchuk, O. Prygun, M. Fu, Z. Le, Q. Xiong, and A. Kryuchyn, “Dispersion of speckle suppression efficiency for binary DOE structures: spectral domain and coherent matrix approaches,” Opt. Express 25(13), 14575–14597 (2017).
    [Crossref] [PubMed]
  12. A. Lapchuk, G. Pashkevich, O. Prygun, I. Kosyak, M. Fu, Z. Le, and A. Kryuchyn, “Very efficient speckle suppression in the entire visible range by one two-sided diffractive optical element,” Appl. Opt. 56(5), 1481–1488 (2017).
    [Crossref]
  13. A. Lapchuk, V. Yurlov, A. Kryuchyn, G. A. Pashkevich, V. Klymenko, and O. Bogdan, “Impact of speed, direction, and accuracy of diffractive optical element shift on efficiency of speckle suppression,” Appl. Opt. 54(13), 4070–4076 (2015).
    [Crossref]
  14. J.-W. Pan and C.-H. Shih, “Speckle reduction and maintaining contrast in a LASER pico-projector using a vibrating symmetric diffuser,” Opt. Express 22(6), 6464–6477 (2014).
    [Crossref] [PubMed]
  15. T.-K.-T. Tran, X. Chen, Ø. Svensen, and M. N. Akram, “Speckle reduction in laser projection using a dynamic deformable mirror,” Opt. Express 22(9), 11152–11166 (2014).
    [Crossref] [PubMed]
  16. J. G. Manni and J. W. Goodman, “Versatile method for achieving 1% speckle contrast in large-venue laser projection displays using a stationary multimode optical fiber,” Opt. Express 20(10), 11288–11315 (2012).
    [Crossref] [PubMed]
  17. M. N. Akram, V. Kartashov, and Z. Tong, “Speckle reduction in line-scan laser projectors using binary phase codes,” Opt. Lett. 35(3), 444–446 (2010).
    [Crossref] [PubMed]
  18. Z. Cui, A. Wang, Z. Wang, S. Wang, C. Gu, H. Ming, and C. Xu, “Speckle suppression by controlling the coherence in laser Based projection systems,” J. Disp. Technol. 11(4), 330–335 (2015).
    [Crossref]
  19. A. Lapchuk, V. Yurlov, G. A. Pashkevich, A. Prygun, A. A. Kryuchyn, and S. Shylo, “Impact of aberrations on speckle suppression efficiency on moving a DOE inside the optical system,” Displays 43, 1–8 (2016).
    [Crossref]

2017 (2)

2016 (1)

A. Lapchuk, V. Yurlov, G. A. Pashkevich, A. Prygun, A. A. Kryuchyn, and S. Shylo, “Impact of aberrations on speckle suppression efficiency on moving a DOE inside the optical system,” Displays 43, 1–8 (2016).
[Crossref]

2015 (3)

2014 (2)

2013 (1)

2012 (1)

2010 (3)

2009 (2)

M. Freeman, M. Champion, and S. Madhavan, “Scanned laser pico-projectors: seeing the big picture (with a Small Device),” Opt. Photonics News 20(5), 28–34 (2009).
[Crossref]

R. Ryf, G. Chen, N. Basavanhally, M. Dinu, A. Duque, Y. L. Low, J. M. Wiesenfeld, Y. Shapiro, and R. Giles, “The Alcatel-Lucent microprojector: what every cell phone needs,” Bell Labs Tech. J. 14(3), 99–112 (2009).
[Crossref]

2004 (1)

J. I. Trisnadi, C. B. Carlisle, and V. Monteverde, “Overview and applications of grating light valve TM based optical write engines for high-speed digital imaging,” Proc. SPIE 5348, 52–64 (2004).
[Crossref]

1998 (1)

Akram, M. N.

Basavanhally, N.

R. Ryf, G. Chen, N. Basavanhally, M. Dinu, A. Duque, Y. L. Low, J. M. Wiesenfeld, Y. Shapiro, and R. Giles, “The Alcatel-Lucent microprojector: what every cell phone needs,” Bell Labs Tech. J. 14(3), 99–112 (2009).
[Crossref]

Bogdan, O.

Borodin, Y.

Carlisle, C. B.

J. I. Trisnadi, C. B. Carlisle, and V. Monteverde, “Overview and applications of grating light valve TM based optical write engines for high-speed digital imaging,” Proc. SPIE 5348, 52–64 (2004).
[Crossref]

Champion, M.

M. Freeman, M. Champion, and S. Madhavan, “Scanned laser pico-projectors: seeing the big picture (with a Small Device),” Opt. Photonics News 20(5), 28–34 (2009).
[Crossref]

Chellappan, K. V.

Chen, G.

R. Ryf, G. Chen, N. Basavanhally, M. Dinu, A. Duque, Y. L. Low, J. M. Wiesenfeld, Y. Shapiro, and R. Giles, “The Alcatel-Lucent microprojector: what every cell phone needs,” Bell Labs Tech. J. 14(3), 99–112 (2009).
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Chen, X.

Cui, Z.

Z. Cui, A. Wang, Z. Wang, S. Wang, C. Gu, H. Ming, and C. Xu, “Speckle suppression by controlling the coherence in laser Based projection systems,” J. Disp. Technol. 11(4), 330–335 (2015).
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Dinu, M.

R. Ryf, G. Chen, N. Basavanhally, M. Dinu, A. Duque, Y. L. Low, J. M. Wiesenfeld, Y. Shapiro, and R. Giles, “The Alcatel-Lucent microprojector: what every cell phone needs,” Bell Labs Tech. J. 14(3), 99–112 (2009).
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Duque, A.

R. Ryf, G. Chen, N. Basavanhally, M. Dinu, A. Duque, Y. L. Low, J. M. Wiesenfeld, Y. Shapiro, and R. Giles, “The Alcatel-Lucent microprojector: what every cell phone needs,” Bell Labs Tech. J. 14(3), 99–112 (2009).
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Erden, E.

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M. Freeman, M. Champion, and S. Madhavan, “Scanned laser pico-projectors: seeing the big picture (with a Small Device),” Opt. Photonics News 20(5), 28–34 (2009).
[Crossref]

Fu, M.

Giles, R.

R. Ryf, G. Chen, N. Basavanhally, M. Dinu, A. Duque, Y. L. Low, J. M. Wiesenfeld, Y. Shapiro, and R. Giles, “The Alcatel-Lucent microprojector: what every cell phone needs,” Bell Labs Tech. J. 14(3), 99–112 (2009).
[Crossref]

Goodman, J. W.

Gu, C.

Z. Cui, A. Wang, Z. Wang, S. Wang, C. Gu, H. Ming, and C. Xu, “Speckle suppression by controlling the coherence in laser Based projection systems,” J. Disp. Technol. 11(4), 330–335 (2015).
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Halldórsson, T.

Kartashov, V.

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A. Lapchuk, V. Yurlov, G. A. Pashkevich, A. Prygun, A. A. Kryuchyn, and S. Shylo, “Impact of aberrations on speckle suppression efficiency on moving a DOE inside the optical system,” Displays 43, 1–8 (2016).
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Kubota, S.

Lapchuk, A.

A. Lapchuk, O. Prygun, M. Fu, Z. Le, Q. Xiong, and A. Kryuchyn, “Dispersion of speckle suppression efficiency for binary DOE structures: spectral domain and coherent matrix approaches,” Opt. Express 25(13), 14575–14597 (2017).
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A. Lapchuk, V. Yurlov, G. A. Pashkevich, A. Prygun, A. A. Kryuchyn, and S. Shylo, “Impact of aberrations on speckle suppression efficiency on moving a DOE inside the optical system,” Displays 43, 1–8 (2016).
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A. Lapchuk, V. Yurlov, A. Kryuchyn, G. A. Pashkevich, V. Klymenko, and O. Bogdan, “Impact of speed, direction, and accuracy of diffractive optical element shift on efficiency of speckle suppression,” Appl. Opt. 54(13), 4070–4076 (2015).
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A. Lapchuk, G. A. Pashkevich, O. V. Prygun, V. Yurlov, Y. Borodin, A. Kryuchyn, A. A. Korchovyi, and S. Shylo, “Experiment evaluation of speckle suppression efficiency of 2D quasi-spiral M-sequence-based diffractive optical element,” Appl. Opt. 54(28), E47–E54 (2015).
[Crossref] [PubMed]

A. Lapchuk, A. Kryuchyn, V. Petrov, and V. Klymenko, “Optimal speckle suppression in laser projectors using a single two-dimensional Barker code diffractive optical element,” J. Opt. Soc. Am. A 30(2), 227–232 (2013).
[Crossref] [PubMed]

Le, Z.

Low, Y. L.

R. Ryf, G. Chen, N. Basavanhally, M. Dinu, A. Duque, Y. L. Low, J. M. Wiesenfeld, Y. Shapiro, and R. Giles, “The Alcatel-Lucent microprojector: what every cell phone needs,” Bell Labs Tech. J. 14(3), 99–112 (2009).
[Crossref]

Madhavan, S.

M. Freeman, M. Champion, and S. Madhavan, “Scanned laser pico-projectors: seeing the big picture (with a Small Device),” Opt. Photonics News 20(5), 28–34 (2009).
[Crossref]

Manni, J. G.

Ming, H.

Z. Cui, A. Wang, Z. Wang, S. Wang, C. Gu, H. Ming, and C. Xu, “Speckle suppression by controlling the coherence in laser Based projection systems,” J. Disp. Technol. 11(4), 330–335 (2015).
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Monteverde, V.

J. I. Trisnadi, C. B. Carlisle, and V. Monteverde, “Overview and applications of grating light valve TM based optical write engines for high-speed digital imaging,” Proc. SPIE 5348, 52–64 (2004).
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Pan, J.-W.

Pashkevich, G.

Pashkevich, G. A.

Petrov, V.

Pétursson, P. R.

Prygun, A.

A. Lapchuk, V. Yurlov, G. A. Pashkevich, A. Prygun, A. A. Kryuchyn, and S. Shylo, “Impact of aberrations on speckle suppression efficiency on moving a DOE inside the optical system,” Displays 43, 1–8 (2016).
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Prygun, O. V.

Ryf, R.

R. Ryf, G. Chen, N. Basavanhally, M. Dinu, A. Duque, Y. L. Low, J. M. Wiesenfeld, Y. Shapiro, and R. Giles, “The Alcatel-Lucent microprojector: what every cell phone needs,” Bell Labs Tech. J. 14(3), 99–112 (2009).
[Crossref]

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R. Ryf, G. Chen, N. Basavanhally, M. Dinu, A. Duque, Y. L. Low, J. M. Wiesenfeld, Y. Shapiro, and R. Giles, “The Alcatel-Lucent microprojector: what every cell phone needs,” Bell Labs Tech. J. 14(3), 99–112 (2009).
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Shylo, S.

A. Lapchuk, V. Yurlov, G. A. Pashkevich, A. Prygun, A. A. Kryuchyn, and S. Shylo, “Impact of aberrations on speckle suppression efficiency on moving a DOE inside the optical system,” Displays 43, 1–8 (2016).
[Crossref]

A. Lapchuk, G. A. Pashkevich, O. V. Prygun, V. Yurlov, Y. Borodin, A. Kryuchyn, A. A. Korchovyi, and S. Shylo, “Experiment evaluation of speckle suppression efficiency of 2D quasi-spiral M-sequence-based diffractive optical element,” Appl. Opt. 54(28), E47–E54 (2015).
[Crossref] [PubMed]

Svensen, Ø.

Tong, Z.

Tran, T.-K.-T.

Trisnadi, J. I.

J. I. Trisnadi, C. B. Carlisle, and V. Monteverde, “Overview and applications of grating light valve TM based optical write engines for high-speed digital imaging,” Proc. SPIE 5348, 52–64 (2004).
[Crossref]

Tschudi, T.

Urey, H.

Wang, A.

Z. Cui, A. Wang, Z. Wang, S. Wang, C. Gu, H. Ming, and C. Xu, “Speckle suppression by controlling the coherence in laser Based projection systems,” J. Disp. Technol. 11(4), 330–335 (2015).
[Crossref]

Wang, L.

Wang, S.

Z. Cui, A. Wang, Z. Wang, S. Wang, C. Gu, H. Ming, and C. Xu, “Speckle suppression by controlling the coherence in laser Based projection systems,” J. Disp. Technol. 11(4), 330–335 (2015).
[Crossref]

Wang, Z.

Z. Cui, A. Wang, Z. Wang, S. Wang, C. Gu, H. Ming, and C. Xu, “Speckle suppression by controlling the coherence in laser Based projection systems,” J. Disp. Technol. 11(4), 330–335 (2015).
[Crossref]

Wiesenfeld, J. M.

R. Ryf, G. Chen, N. Basavanhally, M. Dinu, A. Duque, Y. L. Low, J. M. Wiesenfeld, Y. Shapiro, and R. Giles, “The Alcatel-Lucent microprojector: what every cell phone needs,” Bell Labs Tech. J. 14(3), 99–112 (2009).
[Crossref]

Xiong, Q.

Xu, C.

Z. Cui, A. Wang, Z. Wang, S. Wang, C. Gu, H. Ming, and C. Xu, “Speckle suppression by controlling the coherence in laser Based projection systems,” J. Disp. Technol. 11(4), 330–335 (2015).
[Crossref]

Yurlov, V.

Appl. Opt. (6)

Bell Labs Tech. J. (1)

R. Ryf, G. Chen, N. Basavanhally, M. Dinu, A. Duque, Y. L. Low, J. M. Wiesenfeld, Y. Shapiro, and R. Giles, “The Alcatel-Lucent microprojector: what every cell phone needs,” Bell Labs Tech. J. 14(3), 99–112 (2009).
[Crossref]

Displays (1)

A. Lapchuk, V. Yurlov, G. A. Pashkevich, A. Prygun, A. A. Kryuchyn, and S. Shylo, “Impact of aberrations on speckle suppression efficiency on moving a DOE inside the optical system,” Displays 43, 1–8 (2016).
[Crossref]

J. Disp. Technol. (1)

Z. Cui, A. Wang, Z. Wang, S. Wang, C. Gu, H. Ming, and C. Xu, “Speckle suppression by controlling the coherence in laser Based projection systems,” J. Disp. Technol. 11(4), 330–335 (2015).
[Crossref]

J. Opt. Soc. Am. A (1)

Opt. Express (4)

Opt. Lett. (1)

Opt. Photonics News (1)

M. Freeman, M. Champion, and S. Madhavan, “Scanned laser pico-projectors: seeing the big picture (with a Small Device),” Opt. Photonics News 20(5), 28–34 (2009).
[Crossref]

Proc. SPIE (1)

J. I. Trisnadi, C. B. Carlisle, and V. Monteverde, “Overview and applications of grating light valve TM based optical write engines for high-speed digital imaging,” Proc. SPIE 5348, 52–64 (2004).
[Crossref]

Other (2)

B. Ismay, Semiconductor Laser Diode Technology and Applications (InTech, 1999), p. 376.

J. W. Goodman, Speckle Phenomena in Optics (Roberts & Company, 2006).

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Figures (5)

Fig. 1
Fig. 1 (a) DOE structure on thin film, (b) DOE structure profile, and (c) scheme of DOE movement.
Fig. 2
Fig. 2 Optical scheme of the laser pico-projector with the DOE loop.
Fig. 3
Fig. 3 (a) Scheme showing the movement of the front and back parts of the DOE structure (thin solid and dashed lines show the 1D-DOE structure on the front and back of the DOE loop, respectively) and (b) scheme of the composite 2D-DOE structure movement due to the relative shifts of the two-part 1D DOE for the case of DOE code length N = 4 (small squares denote the smallest elements of the DOE structure and large squares denote the period of the composite 2D DOE structure).
Fig. 4
Fig. 4 Intensity distributions (top) and cross-sections of intensity distribution (bottom) before (left) and after (right) speckle suppression for (a) blue, (b) green, and (c) red laser beams.
Fig. 5
Fig. 5 Dependence of the speckle suppression coefficient k on the DOE shift (in units of length of the diagonal of the smallest element of the DOE) during time integration of the camera; the solid line represents experimental data and the dashed line represents the theoretical results.

Tables (1)

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Table 1 Speckle-suppression efficiency (in %) for blue, green, and red lasers at two different DOE speeds.

Equations (2)

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C=σ/ I m ,
k= C 0 /C,

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