When two systems of contrasting stripes are superimposed, a pattern appears formed by their thickening in places where the stripes of one system fall into the spaces between the stripes of the other system. The occurrence of such patterns is called moire effect.
The simplest moiré pattern occurs when two systems of equidistant parallel stripes (lines) intersect at a slight angle. A small change in the angle of rotation of one of the systems leads to significant changes in the distance between the elements of the moire pattern.
A moire pattern is also formed when two non-intersecting systems of equidistant parallel lines are superimposed, when the step size of one of the systems is slightly different from the other. Moreover, the smaller the difference in pitch, the greater the distance between the moire fringes. This makes it possible to obtain a colossal increase (millions of times) in the difference in the width of the spaces between the lines. In other words, the moire effect makes it possible to visually detect, without the use of optical systems, minute deviations in almost identical periodic structures. Currently, the moiré method is widely used to control the accuracy of dividing devices for the manufacture of diffraction gratings.
Moiré appears in an electron micrograph of two crystals superimposed so that their atomic lattices are almost identical. Any defect that disrupts the regularity of the crystal structure is clearly visible in the moiré pattern. The magnification is such that it allows one to see displacements of atoms, the magnitude of which is less than the diameter of the atom itself.
If two lattices of equidistant parallel straight lines, slightly different in step size, are moved one relative to the other in a direction perpendicular to the lines, then the stripes of the moiré pattern will move at a speed much greater than the relative speed of movement of the lattices themselves. In this case, the direction of their movement coincides with the direction of the relative displacement of the lattice with a smaller step. Thus, a small movement of one of the gratings results in a large movement of the moiré fringes, which is easy to detect and measure.
Application example:
A method for determining deformations from a pattern of moire fringes, characterized in that, in order to increase the accuracy of measuring deformations, the ratio of the speeds of mutual movement of the deformed and reference meshes and the speed of movement of the moire fringe is determined, and the magnitude of the deformations is judged by the value of this ratio.
The described manifestation of the moire effect has long been used in all measuring instruments with nondus, such as a micrometer or caliper.
The moiré effect can be used to visualize minute changes in the refractive index of transparent media by placing them between gratings. For example, you can visually study the dynamics of the dissolution of two substances.
The same principle allows for express analysis of the quality of optical parts. The lenses are placed between the gratings; the presence of a convex lens increases the elements of the moire pattern, while a concave lens decreases them. In this case, both lenses rotate the pattern in opposite directions at an angle proportional to the focal length. In places where the structure or shape of the lenses is inhomogeneous, the pattern lines are distorted.
Another example of optical control:
An interference method for measuring the wedge shape of optical transparent plates, which consists in focusing a beam of light from a laser using a lens into the plane of a hole in the screen, behind which a controlled plate is installed, differing in that, in order to increase the accuracy and productivity of measurements, from the controlled plate with its In a fixed position, a transparent copy of the interference rings is obtained, the plate is rotated in its plane by 180, the interference pattern is superimposed on the copy, and the wedge shape of the platinum is measured using the width of the moiré fringes formed from the overlap.
A variety of moiré patterns can be created by combining lattices formed by a wide variety of lines, such as concentric circles, spiraling wavy or radially radiating lines from a point, and even families of evenly spaced dots. In this way, it is possible to simulate many complex physical phenomena, such as the interaction of electrostatic fields, wave interference, and others. Some problems of architectural acoustics are solved using similar methods.
In Japan, it has been proposed to use the moire effect to compile topographic maps of objects. The object is photographed through a grid of thin threads, casting a clear shadow on it. The shadow is deformed in accordance with the relief of the object and when it interacts with the real lattice, a moiré pattern appears, superimposed on the image of the object. In the photograph, the distance between the moire lines corresponds to the depth of the relief. This method is very effective, for example, in studying the deformation of rapidly rotating parts, in analyzing the flow of a surface layer of liquid around bodies in medical anatomical studies.
The versatility of the moire method, the ease of converting various quantities with its help, close to IFR, high resolution - all this suggests that inventors will turn to the moire effect more than once in their practice.
moire, the name of the fabric) is a pattern that appears when two periodic mesh patterns are superimposed. The phenomenon is due to the fact that the repeating elements of the two patterns follow with slightly different frequencies and either overlap each other or form gaps.The moire pattern is observed when different parts of tulle curtains are placed on top of each other.
The concept of "moiré" comes from fabric moire, in the finishing of which this phenomenon was used.
Moiré pattern occurs when digitally photographing and scanning reticles and other periodic images if their period is close to the distance between the photosensitive elements of the equipment. This fact is used in one of the mechanisms for protecting banknotes from counterfeiting: a wave-like pattern is applied to the banknotes, which, when scanned, can become covered with a very noticeable pattern that distinguishes the counterfeit from the original.
Digital image processing
The appearance of moire during scanning
In everyday life, moire often appears when scanning printed images. This occurs because the scanner re-rasterizes an image that already has the original raster in it. It can be more simply imagined this way: if you take a tracing paper with one ornament and put it on a tracing paper with the same ornament, but depicted from a different angle, then the resulting ornament will differ from both the first and the second. If you put them so that they coincide, then the first ornament will coincide with the second.
The round “rosettes” at the intersection of two rectangles result in image distortion, which is visible in the first picture.
The appearance of moire during the screening process
Moire can also occur due to incorrect setting of angles between the lines of primary colors during screening. Both are, in fact, the interference of two sets of raster lines. There are several types of moire rosettes, by the appearance of which you can often find out the cause of moire.
Scanning, in fact, is the modulation of signals in the scanner grid nodes by the brightness of the typographic raster nodes. In general form, the result is a product of two modulated sinusoids (gratings) with different periods of spatial oscillations. One harmonic may have a larger period equal to the sum of the periods of both gratings, which causes moire. The second always has a period equal to the modulus of the difference between the grating periods and disappears because it cannot be implemented at a given scanning resolution.
Paints that affect moire
When printing with any set of inks, the most intense (dark) ink, which has a value of 30 to 70% over a large area, can produce moire. That is, if in a CMYK photograph the black channel does not dominate (<10-15 %) то вероятность возникновения различимого глазом муара минимальна. Таким образом можно почти не обращать внимание на жёлтый канал CMYK фотографии. Угол поворота растра между самыми проблемными каналами должен быть как можно ближе к 45°.
When printing “solid” (that is, with a fill of >95%), the concept of “raster inclination angle” practically disappears (even if we are talking about photography).
see also
- Wave interference - a moiré pattern creates a superposition of waves of different lengths or directions.
- Vernier - the overlapping of scales with different pitches generates a moiré pattern of parallel lines ( English).
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An excerpt characterizing the Moiré pattern
“Third, I said, third,” the prince shouted briefly, pushing away the letter, and, leaning his elbows on the table, pulled up a notebook with geometry drawings.“Well, madam,” the old man began, bending close to his daughter over the notebook and placing one hand on the back of the chair on which the princess was sitting, so that the princess felt surrounded on all sides by that tobacco and senile pungent smell of her father, which she had known for so long. . - Well, madam, these triangles are similar; would you like to see, angle abc...
The princess looked fearfully at her father’s sparkling eyes close to her; red spots shimmered across her face, and it was clear that she did not understand anything and was so afraid that fear would prevent her from understanding all her father’s further interpretations, no matter how clear they were. Whether the teacher was to blame or the student was to blame, the same thing was repeated every day: the princess’s eyes grew dim, she saw nothing, heard nothing, she only felt the dry face of her stern father close to her, felt his breath and smell and only thought about how she could quickly leave the office and understand the problem in her own open space.
The old man lost his temper: he pushed the chair he was sitting on with a loud noise, made an effort to not get excited, and almost every time he got excited, cursed, and sometimes threw his notebook.
The princess made a mistake in her answer.
- Well, why not be a fool! - the prince shouted, pushing away the notebook and quickly turning away, but immediately stood up, walked around, touched the princess’s hair with his hands and sat down again.
He moved closer and continued his interpretation.
“It’s impossible, princess, it’s impossible,” he said when the princess, having taken and closed the notebook with the assigned lessons, was already preparing to leave, “mathematics is a great thing, my madam.” And I don’t want you to be like our stupid ladies. Will endure and fall in love. “He patted her cheek with his hand. - The nonsense will jump out of your head.
She wanted to go out, he stopped her with a gesture and took out a new uncut book from the high table.
- Here’s another Key of the Sacrament your Eloise sends you. Religious. And I don’t interfere with anyone’s faith... I looked through it. Take it. Well, go, go!
He patted her on the shoulder and locked the door behind her.
Princess Marya returned to her room with a sad, frightened expression that rarely left her and made her ugly, sickly face even more ugly, and sat down at her desk, lined with miniature portraits and littered with notebooks and books. The princess was as disorderly as her father was decent. She put down her geometry notebook and impatiently opened the letter. The letter was from the princess’s closest friend since childhood; this friend was the same Julie Karagina who was at the Rostovs’ name day:
Julie wrote:
"Chere et excellente amie, quelle chose terrible et effrayante que l"absence! J"ai beau me dire que la moitie de mon existence et de mon bonheur est en vous, que malgre la distance qui nous separe, nos coeurs sont unis par des liens indissolubles; le mien se revolte contre la destinee, et je ne puis, malgre les plaisirs et les distractions qui m"entourent, vaincre une certaine tristesse cachee que je ressens au fond du coeur depuis notre separation. Pourquoi ne sommes nous pas reunies, comme cet ete dans votre grand cabinet sur le canape bleu, le canape a confidences? Pourquoi ne puis je, comme il y a trois mois, puiser de nouvelles forces morales dans votre regard si doux, si calme et si penetrant, regard que j"aimais tant et que “je crois voir devant moi, quand je vous ecris.”
[Dear and priceless friend, what a terrible and terrible thing is separation! No matter how much I tell myself that half of my existence and my happiness lies in you, that, despite the distance that separates us, our hearts are united by inextricable bonds, my heart rebels against fate, and, despite the pleasures and distractions that surround me, I I cannot suppress some hidden sadness that I have been experiencing in the depths of my heart since our separation. Why aren’t we together, like last summer, in your big office, on the blue sofa, on the sofa of “confessions”? Why can’t I, like three months ago, draw new moral strength from your gaze, meek, calm and penetrating, which I loved so much and which I see before me at the moment I write to you?]
Having read up to this point, Princess Marya sighed and looked back at the dressing table, which stood to her right. The mirror reflected an ugly, weak body and a thin face. The eyes, always sad, now looked at themselves in the mirror especially hopelessly. “She flatters me,” thought the princess, turned away and continued reading. Julie, however, did not flatter her friend: indeed, the princess’s eyes, large, deep and radiant (as if rays of warm light sometimes came out of them in sheaves), were so beautiful that very often, despite the ugliness of her whole face, these eyes became more attractive than beauty. But the princess had never seen a good expression in her eyes, the expression they took on in those moments when she was not thinking about herself. Like all people, her face took on a tense, unnatural, bad expression as soon as she looked in the mirror. She continued reading: 211
You may have already seen moire in images - it's a strange wave-like pattern that doesn't appear on the subject.
This effect occurs when an image of an object with many details, such as lines, is superimposed on the pattern of pixels on the matrix.
As a result, it is most often seen in detailed, high-contrast images of patterns. It usually appears when photographing fabric, hair, or scenes that contain repeating details, such as pronounced vertical lines in architecture.
As you can see in the picture, when two patterns are superimposed on each other, moiré is formed.
What is color distortion?
This term is used to refer to those colors in a digital image that differ from the actual colors of the object. The light coming from an object is not detected by all RGB color sensors, which causes the stored colors to change. In digital images, moire and color distortion usually appear together.
In the image above, the U-shaped pattern on the slate wall is the result of moire. In addition, there are areas of red color in the image, which are the result of color distortion.
Many digital cameras use an optical low-pass filter to reduce aliasing and color distortion.
By understanding the nature of these effects and why they occur, these problems can be minimized during shooting or editing.
1. Change the shooting angle and the distance between the camera and the subject.
Since the effects of distortion are affected by the angle at which you shoot and the distance between the camera and your subject, small changes can eliminate or reduce these imperfections. Move the camera left or right, up or down, or move a little closer or further away.
2. Change the focus point.
The reasons for the occurrence of moire and color distortion are very sharp focusing and high detail of the drawings. By manually adjusting the lens and setting the focus slightly in front of or behind the focus point, you can avoid such effects.
3. Change the focal length using a different lens.
4. Decrease the lens aperture.
MTF graph with resolution values for lenses with different apertures.
The optimal resolution for each lens is achieved at a certain aperture value (in the graph this is f/8). Optimal resolution is usually achieved by setting the aperture value 2-3 stops below the maximum.
Closing the aperture too much (beyond optimal resolution) will cause diffraction. In this case, the resolution will decrease slightly, but at the same time the distortion effects will also decrease.
To check whether there are such phenomena in the picture, it is best to view the images on a computer screen at full size (100%). When pictures are reduced in size, false moire and color distortion may occur due to the pattern on the monitor tube (or panel).
These effects can appear in images from all digital cameras and scanners, but are more likely to occur in images from DSLR cameras because the lens, sensor, and software are designed to produce the sharpest, most accurate image possible.
The distortion may not be eliminated, but it can be reduced if you know under what circumstances the problem occurs and how to fix it.
The specialists of the Neman company have perfectly mastered the technology of applying polymer powder coating both to finished doors and to non-standard structures. For this you have everything you need - knowledge, experience, strength and desire. Polymer painting is a waste-free and clean technology that allows you to obtain high-quality decorative, protective and decorative coatings.
Note that the appearance is formed from polymer powders applied to the painted part of the product fabric. Next, the product is heated and held at a certain temperature for several minutes. The low polymerization temperature makes it possible to paint glass and metal using this technology. In the last decade, this technology has gained great popularity and is gradually replacing traditional methods of applying paint and varnish coatings.
One of the finishing options offered by the Neman company is Moire. What is this coating? This is an entrance door finish that offers a special powder coating structure. So, upon completion of the work there will be a special pattern on the canvas. Speaking figuratively, moire can be compared to the effect that sandpaper gives. The main advantages of this type are: practicality, aesthetics and versatility. Typically, such products are used in cases where it is necessary to obtain the maximum practicality possible. It is also effectively used to hide defects in the outer part of a metal door.
What benefits does a consumer receive when choosing moire coloring?
- High resistance to aggressive environments (alkalies, acids, organic solvents);
- Resistance to mechanical stress;
- Increased adhesion. In this case, the adhesion of paint particles to the surface being treated is 500 kg/nm;
- High anti-corrosion resistance;
- Environmental friendliness. The paint does not contain organic solvents or other types of volatile substances.
The main idea of the painting method is to spray powder paint onto a previously cleaned metal coating. You need to know that paint particles receive an electrostatic charge, which allows the particle to stick to a product that has the opposite charge. Particles that have not had time to settle are captured in the spray chamber and can be used again. After this, the product is placed in a polymerization chamber for subsequent baking of the paint at a temperature level ranging from 180 to 200 degrees Celsius. Thus, a reliable, high-quality and safe decorative and protective design for humans is created on the canvas. Metal doors painted with Moire can be used not only for installation in apartments, cottages, but also in industrial facilities.
Moiré pattern
The appearance of moire when two linear gratings are superimposed.
Moire pattern(moire, from French. moire) - a pattern that occurs when two periodic mesh patterns are superimposed. The phenomenon is due to the fact that the repeating elements of the two patterns follow with slightly different frequencies and either overlap each other or form gaps.
The moire pattern is observed when different parts of tulle curtains are placed on top of each other.
The concept of "moiré" comes from fabric moire, in the finishing of which this phenomenon was used.
Moiré pattern occurs when digitally photographing and scanning reticles and other periodic images if their period is close to the distance between the photosensitive elements of the equipment. This fact is used in one of the mechanisms for protecting banknotes from counterfeiting: a wave-like pattern is applied to the banknotes, which, when scanned, can become covered with a very noticeable pattern that distinguishes the counterfeit from the original.
Digital image processing
The appearance of moire during scanning
Most often in everyday life, moire appears when scanning printed images. This occurs because the scanner re-rasterizes an image that already has the original raster in it. It can be more simply imagined this way: if you take a tracing paper with one ornament and put it on a tracing paper with the same ornament, but depicted from a different angle, then the resulting ornament will differ from both the first and the second. If you put them so that they coincide, then the first ornament will coincide with the second.
The round “rosettes” at the intersection of two rectangles result in image distortion, which is visible in the first picture.
The appearance of moire during the screening process
"Divers". The sky is painted with uneven horizontal lines, and at low resolutions you get moiré.
Moire can also occur due to incorrect setting of angles between the lines of primary colors during screening. Both are, in fact, the interference of two sets of raster lines. There are several types of moire rosettes, by the appearance of which you can often find out the cause of moire.
Scanning, in fact, is the modulation of signals in the scanner grid nodes by the brightness of the typographic raster nodes. In general form, the result is a product of two modulated sinusoids (gratings) with different periods of spatial oscillations. One harmonic may have a larger period equal to the sum of the periods of both gratings, which causes moire. The second always has a period equal to the modulus of the difference between the grating periods and disappears because it cannot be implemented at a given scanning resolution.
Paints that affect moire
Moiré ribbon
When printing with any set of inks, the most intense (dark) ink, which has a value of 30 to 70% over a large area, can produce moire. That is, if in our CMYK photograph the black channel does not dominate (<10-15%) то вероятность возникновения различимого глазом муара минимальна. Таким образом можно почти не обращать внимание на жёлтый канал CMYK фотографии. Угол поворота растра между самыми проблемными каналами должен быть как можно ближе к 45°.
When printing “solid” (that is, with a fill of >95%), the concept of “raster inclination angle” practically disappears (even if we are talking about photography).
see also
Links
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See what “Moiré pattern” is in other dictionaries:
The appearance of moire when two linear gratings are superimposed. Moire on the ribbon of the Order of St. Andrew the First-Called. Moire pattern (moire, from the French moiré) is a pattern that occurs when two periodic mesh patterns are superimposed. The phenomenon is due to the fact that... ... Wikipedia
