- Jyväskylä, Western Finland, Finland
- University of Jyväskylä, Physics, Department Memberadd
- Teacher, researcher, ITC specialistedit
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We study the solar flare index (SFI) for the Solar Cycles 18 – 24. We find that SFI has deeper Gnevyshev gap (GG) in its first principal component than other atmospheric parameters. The GG is extremely clear especially in the even... more
We study the solar flare index (SFI) for the Solar Cycles 18 – 24. We find that SFI has deeper Gnevyshev gap (GG) in its first principal component than other atmospheric parameters. The GG is extremely clear especially in the even cycles.The GG of the SFI appears about a half year later as a drop in the interplanetary magnetic field near the Earth and in the geomagnetic Ap-index. The instantaneous response of the magnetic field to solar flares, however, shows about two to three days after the eruption as a high, sharp peak in the cross-correlation of the SFI and Ap-index and as a lower peak in SFI vs. IMF B cross-correlation. We confirm these rapid responses using superposed-epoch analysis.The most active flare cycles during 1944 – 2020 are Cycles 19 and 21. Cycle 18 has very strong SFI days as many as Cycle 22, but it has the least nonzero SFI days in the whole interval. Interestingly, Cycle 20 can be compared to Cycles 23 and 24 in its low flare activity, although it is located be...
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A detailed analysis has been made of 13 periods of 20 days of the AE data. The average correlation dimension is found to be 3.4, and the calculated dimension is found to depend on the magnetospheric activity such that more active periods... more
A detailed analysis has been made of 13 periods of 20 days of the AE data. The average correlation dimension is found to be 3.4, and the calculated dimension is found to depend on the magnetospheric activity such that more active periods have smaller dimensions. This apparent correlation dimension does not, however, imply that the magnetospheric system behind the AE
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We study the annual periodicity and the solar rotation periodicity of the in‐ecliptic components of the interplanetary magnetic field (IMF). It is well known that the annual periodicity undergoes a phase reversal in 11 years, reflecting... more
We study the annual periodicity and the solar rotation periodicity of the in‐ecliptic components of the interplanetary magnetic field (IMF). It is well known that the annual periodicity undergoes a phase reversal in 11 years, reflecting the 22‐year Hale cycle of the solar magnetic field. We construct a model where the annual periodicity of the IMF components is phase/frequency modulated by the Hale cycle, and show that this model can reproduce the observed properties of the annual periodicity. We find that the solar rotation periodicity depicts an analogous nodal structure and a phase reversal with a period of about 3.2 years, implying a new periodicity in the properties of the IMF. We demonstrate that, using the observed spectral width, the phase/frequency modulation model can satisfactorily explain this structure. We also note that taking into account the observed phase reversal in the solar rotation periodicity implies that the most persistent synodic solar rotation period in the in‐ecliptic IMF components is 27.6 days, i.e., somewhat longer than recently suggested.
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We study the latitudinal distribution and temporal evolution of the sunspot penumbra-umbra ratio ($q$ q ) for the even and odd Solar Cycles 12 – 24 of RGO sunspot groups, SC21 – SC24 of Debrecen sunspot groups and Kodaikanal sunspot... more
We study the latitudinal distribution and temporal evolution of the sunspot penumbra-umbra ratio ($q$ q ) for the even and odd Solar Cycles 12 – 24 of RGO sunspot groups, SC21 – SC24 of Debrecen sunspot groups and Kodaikanal sunspot dataset for SC16 – SC24. We find that RGO even (odd) Cycles have $q$ q -values 5.20 (4.75), Kodaikanal even (odd) cycles have $q$ q -values 5.27 (5.43), and Debrecen cycles have $q$ q -value 5.74 on the average.We also show that $q$ q is at its lowest around the Equator of the Sun and increases towards higher latitudes having maximum values at about 10 – 25 degrees. This is understandable because smaller sunspots and groups locate nearer to the Equator and have smaller $q$ q -values than larger sunspots and groups, which maximize at about 10 – 20 degrees at both hemispheres. The error limits are very wide, and, thus, the confidence in this result is somewhat vague.For the Debrecen dataset, we find a deep valley in the temporal $q$ q -values before the mi...
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The Data (an Origin file) used for Appendix Figure 3
We decompose the monthly cosmic-ray data, using several neutron-monitor count rates, of Cycles 19 – 24 with principal component analysis (PCA). Using different cycle limits, we show that the first and second PC of cosmic-ray (CR) data... more
We decompose the monthly cosmic-ray data, using several neutron-monitor count rates, of Cycles 19 – 24 with principal component analysis (PCA). Using different cycle limits, we show that the first and second PC of cosmic-ray (CR) data explain 77 – 79% and 13 – 15% of the total variation of the Oulu CR Cycles 20 – 24 (C20 – C24), 73 – 77% and 13 – 17% of the variation of Hermanus C20 – C24, and 74 – 78% and 17 – 21% of the Climax C19 – C22, respectively. The PC1 time series of the CR Cycles 19 – 24 has only one peak in its power spectrum at the period 10.95 years, which is the average solar-cycle period for SC19 – SC24. The PC2 time series of the same cycles has a clear peak at period 21.90 (Hale cycle) and another peak at one third of that period with no peak at the solar-cycle period. We show that the PC2 of the CR is essential in explaining the differences in the intensities of the even and odd cycles of the CR. The odd cycles have a positive phase in the first half and a negative...
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The homogeneous coronal data set (HCDS) of the green corona (Fe xiv) and the coronal index of solar activity (CI) have been used to study the time–latitudinal distribution in Solar Cycles 18 – 24 and compared with similar distribution of... more
The homogeneous coronal data set (HCDS) of the green corona (Fe xiv) and the coronal index of solar activity (CI) have been used to study the time–latitudinal distribution in Solar Cycles 18 – 24 and compared with similar distribution of sunspots, the magnetic fields, and the solar 10.7 cm radio flux. The most important results are: i) the distribution of coronal intensities related to the cycle maximum are different for individual cycles, ii) the poleward migration of the HCDS from mid-latitudes in each cycle exists, even in the extremely weak Cycle 24, and the same is valid for the equatorward migration, iii) the overall values of HCDS are slightly stronger for the northern hemisphere than for the southern one, iv) the distribution of the HDCS is in coincidence with the strongest photospheric magnetic fields ($B>$ B > 50 Gauss) and histograms of the sunspot groups, v) the Gnevyshev gap was confirmed with at least 95% confidence in the CI, however with different behavior for ...
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A novel method is presented for distinguishing postal stamp forgeries and counterfeit banknotes from genuine samples. The method is based on analyzing differences in paper fibre networks. The main tool is a curvelet-based algorithm for... more
A novel method is presented for distinguishing postal stamp forgeries and counterfeit banknotes from genuine samples. The method is based on analyzing differences in paper fibre networks. The main tool is a curvelet-based algorithm for measuring overall fibre orientation distribution and quantifying anisotropy. Using a couple of more appropriate parameters makes it possible to distinguish forgeries from genuine originals as concentrated point clouds in two- or three-dimensional parameter space.
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We study distributions of differences of unscaled Riemann zeta zeros, γ-γ^', at large. We show, that independently of the location of the zeros, i.e., even for zeros as high as 10^23, their differences have similar statistical... more
We study distributions of differences of unscaled Riemann zeta zeros, γ-γ^', at large. We show, that independently of the location of the zeros, i.e., even for zeros as high as 10^23, their differences have similar statistical properties. The distributions of differences are skewed usually towards the nearest zeta zero. We show, however, that this is not always the case, but depends upon the distance and number of nearby zeros on each side of the corresponding distribution. The skewness, however, always decreases when zeta zero is crossed from left to right, i.e., in increasing direction. Furthermore, we show that the variance of distributions has local maximum or, at least, a turning point at every zeta zero, i.e., local minimum of the second derivative of the variance. In addition, it seems that the higher the zeros the more compactly the distributions of the differences are located in the skewness-kurtosis -plane. Furthermore, we show that distributions can be fitted with Joh...
We study distributions of differences of unscaled Riemann zeta zeros, γ-γ', at large. We show, that independently of the location of the zeros, their differences have similar statistical properties. The distributions of differences... more
We study distributions of differences of unscaled Riemann zeta zeros, γ-γ', at large. We show, that independently of the location of the zeros, their differences have similar statistical properties. The distributions of differences are skewed towards the nearest zeta zero, have local maximum of variance and local minimum of kurtosis at or near each zeta zero. Furthermore, we show that distributions can be fitted with Johnson probability density function, despite the value of skewness or kurtosis of the distribution.
We study the evolution of continental, zonal and seasonal land temperature anomalies especially in the early 20th century warming (ETCW) period, using principal component analysis (PCA) and reverse arrangement trend analysis. ETCW is... more
We study the evolution of continental, zonal and seasonal land temperature anomalies especially in the early 20th century warming (ETCW) period, using principal component analysis (PCA) and reverse arrangement trend analysis. ETCW is significant in all other continents except for Oceania. Warming in South America is significant from the ETCW onwards, but significant recent warming started in North America and Europe only around 1990. The zonal and seasonal PC2s are both correlated with AMO index, but zonal PC3 is related to Southern oscillation index (SOI) and seasonal PC3 best correlated with wintertime El Nino (NINO34 DJF index). In the southern hemisphere, the recent warming starts first closest to the equator in the 1950s and latest in the southernmost zone in the late 1970s. In the two lowest northern zones (EQ-N24, N24-N44) the warming is significant since the ETCW, and increased warming starts in 1970s, but in two northernmost zones (N44-N64, N64-N90) the cooling after the ET...
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We study distributions of differences of unscaled Riemann zeta zeros, $\gamma-\gamma^{'}$, at large distances. We show, that independently of the height, a subset of finite number of successive zeros knows the locations of lower level... more
We study distributions of differences of unscaled Riemann zeta zeros, $\gamma-\gamma^{'}$, at large distances. We show, that independently of the height, a subset of finite number of successive zeros knows the locations of lower level zeros. The information contained in the subset of zeros is inversely proportional to $ln(\gamma/(2\pi))$, where $\gamma$ is the average zeta of the subset. Because the mean difference of the zeros also decreases as inversely proportional to $ln(\gamma/(2\pi))$, each equally long segment of the line $\Re(z)=1/2$ contains equal amount of information. The distributions of differences are skewed towards the nearest zeta zero, or at least, in the case of very nearby zeros, the skewness always decreases when zeta zero is crossed in increasing direction. We also show that the variance of distributions has local maximum or, at least, a turning point at every zeta zero, i.e., local minimum of the second derivative of the variance. In addition, it seems that...
Research Interests: Mathematics and Physics
We analyze the temporal distribution of sunspot groups for even and odd cycles in the range SC12-SC24. It seems that cycle 24 is a characteristic even cycle, although with low amplitude. The number of large sunspot groups for cycle 24 is... more
We analyze the temporal distribution of sunspot groups for even and odd cycles in the range SC12-SC24. It seems that cycle 24 is a characteristic even cycle, although with low amplitude. The number of large sunspot groups for cycle 24 is relatively smaller than for the average of both even and odd cycles SC12-SC23, and there is a deep decline of the large groups in the middle of the cycle. Temporal evolution of the sunspot groups of the even cycles is non-synchronous such that the northern hemisphere distribution of groups maximizes earlier that the southern hemisphere groups. This leads to a double-peak structure for the average even cycle. On the other hand, the distributions of the sunspot groups of odd cycles maximize simultaneously. We show that this double-peak structure intensifies the Gnevyshev gap (GG) for the even cycles, but is not its primary cause. On the contrary, we show that the GG exists for even and odd cycles, and separately on both hemispheres. We resample all cy...
We study distributions of differences of unscaled Riemann zeta zeros, $\gamma-\gamma'$, at large. We show, that independently of the location of the zeros, their differences have similar statistical properties. The distributions of... more
We study distributions of differences of unscaled Riemann zeta zeros, $\gamma-\gamma'$, at large. We show, that independently of the location of the zeros, their differences have similar statistical properties. The distributions of differences are skewed towards the nearest zeta zero, have local maximum of variance and local minimum of kurtosis at or near each zeta zero. Furthermore, we show that distributions can be fitted with Johnson probability density function, despite the value of skewness or kurtosis of the distribution.
We study distributions of differences of unscaled Riemann zeta zeros, $\gamma-\gamma^{'}$, at large. We show, that independently of the location of the zeros, i.e., even for zeros as high as $10^{23}$, their differences have similar... more
We study distributions of differences of unscaled Riemann zeta zeros, $\gamma-\gamma^{'}$, at large. We show, that independently of the location of the zeros, i.e., even for zeros as high as $10^{23}$, their differences have similar statistical properties. The distributions of differences are skewed usually towards the nearest zeta zero. We show, however, that this is not always the case, but depends upon the distance and number of nearby zeros on each side of the corresponding distribution. The skewness, however, always decreases when zeta zero is crossed from left to right, i.e., in increasing direction. Furthermore, we show that the variance of distributions has local maximum or, at least, a turning point at every zeta zero, i.e., local minimum of the second derivative of the variance. In addition, it seems that the higher the zeros the more compactly the distributions of the differences are located in the skewness-kurtosis -plane. Furthermore, we show that distributions can ...
We decompose the monthly aa-index of cycles 10 – 23 using principal component analysis (PCA). We show that the first component (PC1) is related to solar cycle, and accounts for 41.5 % of the variance of the data. The second component... more
We decompose the monthly aa-index of cycles 10 – 23 using principal component analysis (PCA). We show that the first component (PC1) is related to solar cycle, and accounts for 41.5 % of the variance of the data. The second component (PC2) is related to 22-year Hale cycle, and explains 23.6 % of the variance of the data. The PC1 time series of aa cycles 10 – 23 has only one peak in its power spectrum at the period 10.95 years, which is the average solar cycle period for the interval SC10 – SC23. The PC2 time series of the same cycles has a clear peak at period 21.90 (Hale cycle) and a smaller peak at 3/4 of that period. We also study the principal component of sunspot numbers (SSN) for cycles 10 – 23, and compare mutual behavior of the PC2 components of aa-index and SSN PCA analyses. We note that they are in the same phase in all other cycles than Solar Cycles 15 and 20. The aa cycle 20 also differs from other even aa cycles in its shape, especially in anomalously high peaks during ...
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ract: Using detrended fluctuation analysis (DFA) we find that the all continents are persistent in temperature. The scaling exponents of the southern hemisphere (SH) continents, i.e., South America (α=0.78) and Oceania (0.75) are somewhat... more
ract: Using detrended fluctuation analysis (DFA) we find that the all continents are persistent in temperature. The scaling exponents of the southern hemisphere (SH) continents, i.e., South America (α=0.78) and Oceania (0.75) are somewhat higher than scaling exponents of Europe (0.70), Asia (0.69) and North America (0.65), but the scaling of Africa is by far the highest (0.89). The scaling exponents of the precipitation are much smaller, i.e., between 0.54 (Europe) and 0.67 (North America). The scaling exponent of Europe is near the exponent of random Brownian noise, which is 0.5. The other continents are slightly persistent in precipitation. The slopes of the logarithmic power spectra of the continents are in line with the scaling exponents confirming the DFA analysis results. We also show that the persistence is real and not the intrinsic property of the data itself. We find that scaling exponent α, i.e., persistence of the monthly temperature increases when going from local to l...
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We show that the time series of sunspot group areas has a gap, the so-called Gnevyshev gap (GG), between ascending and descending phases of the cycle and especially so for the even-numbered cycles. For the odd cycles this gap is less... more
We show that the time series of sunspot group areas has a gap, the so-called Gnevyshev gap (GG), between ascending and descending phases of the cycle and especially so for the even-numbered cycles. For the odd cycles this gap is less obvious, and is only a small decline after the maximum of the cycle. We resample the cycles to have the same length of 3945 days (about 10.8 years), and show that the decline is between 1445 – 1567 days after the start of the cycle for the even cycles, and extending sometimes until 1725 days from the start of the cycle. For the odd cycles the gap is a little earlier, 1332 – 1445 days after the start of the cycles with no extension. We analyze geomagnetic disturbances for Solar Cycles 17 – 24 using the Dst-index, the related Dxt- and Dcx-indices, and the Ap-index. In all of these time series there is a decline at the time, or somewhat after, the GG in the solar indices, and it is at its deepest between 1567 – 1725 days for the even cycles and between 144...
Research Interests: Physics and Solar Physics
We study the latitudinal distribution and evolution of sunspot areas of Solar Cycles 12 – 23 (SC12–23) and sunspot groups of Solar Cycles 8 – 23 (SC8–23) for even and odd cycles. The Rician distribution is the best-fit function for both... more
We study the latitudinal distribution and evolution of sunspot areas of Solar Cycles 12 – 23 (SC12–23) and sunspot groups of Solar Cycles 8 – 23 (SC8–23) for even and odd cycles. The Rician distribution is the best-fit function for both even and odd sunspots group latitudinal occurrence. The mean and variance for even northern/southern butterfly wing sunspots are 14.94/14.76 and 58.62/56.08, respectively, and the mean and variance for odd northern/southern wing sunspots are 15.52/15.58 and 61.77/58.00, respectively. Sunspot groups of even cycle wings are thus at somewhat lower latitudes on average than sunspot groups of the odd cycle wings, i.e. about 0.6 degrees for northern hemisphere wings and 0.8 degrees for southern hemisphere wings.The spatial analysis of sunspot areas between SC12–23 shows that the small sunspots are at lower solar latitudes of the Sun than the large sunspots for both odd and even cycles, and also for both hemispheres.Temporal evolution of sunspot areas shows...
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Aims. We study the difference in the shape of solar cycles for even and odd cycles using the Wolf sunspot numbers and group sunspot numbers of solar cycles 1−23. We furthermore analyse the data of sunspot area sizes for even and odd... more
Aims. We study the difference in the shape of solar cycles for even and odd cycles using the Wolf sunspot numbers and group sunspot numbers of solar cycles 1−23. We furthermore analyse the data of sunspot area sizes for even and odd cycles SC12−SC23 and sunspot group data for even and odd cycles SC8−SC23 to compare the temporal evolution of even and odd cycles. Methods. We applied the principal component analysis (PCA) to sunspot cycle data and studied the first two components, which describe the average cycle shape and cycle asymmetry. We used a distribution analysis to analyse the temporal evolution of the even and odd cycles and determined the skewness and kurtosis for even and odd cycles of sunspot group data. Results. The PCA confirms the existence of the Gnevyshev gap (GG) for solar cycles at about 40% from the start of the cycle. The temporal evolution of sunspot area data for even cycles shows that the GG exists at least at the 95% confidence level for all sizes of sunspots....
Research Interests: Mathematics and Physics
Aims. We study the shape of sunspot cycles using the Wolf sunspot numbers and group sunspot numbers of solar cycles 1–23. We determine the most typical “model” cycles and the most asymmetric cycles, and test the validity of the two... more
Aims. We study the shape of sunspot cycles using the Wolf sunspot numbers and group sunspot numbers of solar cycles 1–23. We determine the most typical “model” cycles and the most asymmetric cycles, and test the validity of the two Waldmeier rules: the anti-correlation between cycle height and the length of its ascending phase (rule 1), and between cycle height and the length of the preceding cycle (rule 2). Methods. We applied the principal component analysis to sunspot cycles and studied the first two components, which describe the average cycle shape and cycle asymmetry, respectively. We also calculated their autocorrelation in order to study their recurrence properties. Results. The best model cycles for Wolf numbers are SC12, SC14, and SC16, the successive even cycles from a long period of rather low overall solar activity. We find that the model cycles in eight different analyses using both sunspot series are almost exclusively even cycles. Correspondingly, the most asymmetric...
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We study the annual periodicity and the solar rotation periodicity of the Bx component of the interplanetary magnetic field (IMF). It is known since long that the annual periodicity undergoes a phase reversal in 11 years, reflecting the... more
We study the annual periodicity and the solar rotation periodicity of the Bx component of the interplanetary magnetic field (IMF). It is known since long that the annual periodicity undergoes a phase reversal in 11 years, reflecting the 22-year Hale cycle of the solar magnetic field. We construct a simple model where the annual periodicity of the IMF components is phase/frequency modulated by the Hale cycle, and show that this model can outstandingly well reproduce the observed properties of the annual periodicity. We show that the solar rotation periodicity depicts an analogous nodal structrure and a phase reversal with a period of about 3.2 years. This implies a new periodicity in the phase properties of the interplanetary magnetic field. We demonstrate that, using the observed spectral width, the phase/frequency modulation model can satisfactorily explain this structure. We also note that taking into account the observed phase reversal in the solar rotation periodicity implies th...
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A method based on the curvelet transform is introduced to estimate the orientation distribution from two-dimensional images of small anisotropic particles. Orientation of fibers in paper is considered as a particular application of the... more
A method based on the curvelet transform is introduced to estimate the orientation distribution from two-dimensional images of small anisotropic particles. Orientation of fibers in paper is considered as a particular application of the method. Theoretical aspects of the suitability of this method are discussed and its efficiency is demonstrated with simulated and real images of fibrous systems. Comparison is made with two traditionally used methods of orientation analysis, and the new curvelet-based method is shown to perform better than these tradi-tional methods.
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Background The cardiomyocyte is a prime example of inherently complex biological system with inter- and cross-connected feedback loops in signalling, forming the basic properties of intracellular homeostasis. Functional properties of... more
Background The cardiomyocyte is a prime example of inherently complex biological system with inter- and cross-connected feedback loops in signalling, forming the basic properties of intracellular homeostasis. Functional properties of cells and tissues have been studied e.g. with powerful tools of genetic engineering, combined with extensive experimentation. While this approach provides accurate information about the physiology at the endpoint, complementary methods, such as mathematical modelling, can provide more detailed information about the processes that have lead to the endpoint phenotype. Results In order to gain novel mechanistic information of the excitation-contraction coupling in normal myocytes and to analyze sophisticated genetically engineered heart models, we have built a mathematical model of a mouse ventricular myocyte. In addition to the fundamental components of membrane excitation, calcium signalling and contraction, our integrated model includes the calcium-calmodulin-dependent enzyme cascade and the regulation it imposes on the proteins involved in excitation-contraction coupling. With the model, we investigate the effects of three genetic modifications that interfere with calcium signalling: 1) ablation of phospholamban, 2) disruption of the regulation of L-type calcium channels by calcium-calmodulin-dependent kinase II (CaMK) and 3) overexpression of CaMK. We show that the key features of the experimental phenotypes involve physiological compensatory and autoregulatory mechanisms that bring the system to a state closer to the original wild-type phenotype in all transgenic models. A drastic phenotype was found when the genetic modification disrupts the regulatory signalling system itself, i.e. the CaMK overexpression model. Conclusion The novel features of the presented cardiomyocyte model enable accurate description of excitation-contraction coupling. The model is thus an applicable tool for further studies of both normal and defective cellular physiology. We propose that integrative modelling as in the present work is a valuable complement to experiments in understanding the causality within complex biological systems such as cardiac myocytes.
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Virtual reality projection systems have been used formerly to study if mammals, including humans, are able to act in or understand virtual environments. Insects have been more difficult to study in such circumstances, one of the factors... more
Virtual reality projection systems have been used formerly to study if mammals, including humans, are able to act in or understand virtual environments. Insects have been more difficult to study in such circumstances, one of the factors being their large, almost hemispherical field of view. Designing such a projection system that is capable of fulfilling the full field of vision of an insect is a challenging task. Normally, when designing a photographic objective, one of the goals is to minimize field curvature in order to provide sharp image through the whole sensor surface. However, because the image surface in this case is a sphere, flat field is not desirable and the design task becomes an opposite of a typical camera lens. Introducing field curvature becomes mandatory. We have designed and built a system with satisfactory image quality throughout the whole spherical surface with reasonable number of lenses as an add-on for common digital projectors. The manufactured system is able to project an image to a solid angle of 11.95 steradians, and when compared to the whole sphere which is represented with a solid angle of 4π steradians, approximately 5 % of the total sphere area is not illuminated.