Also called diffraction grating. It is an optical element that disperses
(decomposes into a spectrum) light using the principle of multi-slit
diffraction. It is a flat glass or metal sheet engraved with a large number of
parallel equal width and equidistant slits (scribed lines). The number of
slits in the grating is very large, generally tens to thousands per
millimeter. The monochromatic parallel light passes through the diffraction of
each slit of the grating and the interference between the slits, forming a
pattern with very wide dark fringes and very fine bright fringes. These sharp
and bright fringes are called spectral lines. The position of the spectral
line varies with the wavelength. When the polychromatic light passes through
the grating, the spectral lines of different wavelengths appear in different
positions to form a spectrum. The light passing through the grating to form a
spectrum is a common result of single-slit diffraction and multi-slit
The position of the spectral line generated by the diffraction grating can be
expressed by the formula d·sinq=kl. In the formula, d=slit width a+slit
spacing b, which is called the grating constant; q is the diffraction angle, l
is the wavelength, k=0, ±1, ±2... are the spectral series. Using this formula,
the wavelength of light can be calculated. The fringes produced by the grating
have the characteristics of high intensity, narrow fringes, wide spacing
between each other, and excellent resolution performance. Because the use of
grating diffraction can accurately determine the wavelength. The resolving
power of the diffraction grating is R=l/Dl=kN. Among them, N is the number of
slits. The more the number of slits, the brighter and thinner the bright
fringes, and the higher the resolution of the grating. Increasing the number
of slits N to improve the resolution is an important issue in grating
The earliest grating was made in 1821 by the German scientist J. Fraunhofer,
who wound fine metal wires in close packing on two parallel thin screws.
Because it is shaped like a fence, it is named "Raster". Modern gratings are
scribed on glass or metal sheets with precision scribers. Grating is the core
component of grating spectrograph, and there are many kinds of it. According
to whether the light used is transmitted or reflected, it is divided into
transmission grating and reflection grating. Reflection gratings are widely
used; they are divided into plane gratings and concave gratings according to
their shapes. In addition, there are holographic gratings, orthogonal
gratings, phase gratings, blazing gratings, echelle gratings, etc.
Grating is a combination of digital technology and traditional printing
technology, which can show different special effects on special films. Show
the lifelike three-dimensional world on the plane, the smooth animation clips
like a movie, and the incredible changing effect. A grating is a thin sheet of
strip lenses. When we look from one side of the lens, we will see an image on
the other side of the sheet as a very thin line, and the position of this line
is determined by the viewing angle. Decide. If we print these several images
on different lines, corresponding to the width of each lens, and print them on
the back of the lenticular sheet in order and line, when we look through the
lens from different angles, we will see different images.
According to research, when our human eyes observe a three-dimensional object,
since the two eyes are horizontally separated in two different positions, the
observed image of the object is different, and there is an aberration between
them, due to this aberration The existence of the human brain, we can feel the
depth of a three-dimensional world, three-dimensional changes, this is the
so-called principle of stereo vision. According to the principle of stereo
vision, if we can let our left and right eyes see two images taken at
different positions, we should be able to feel a three-dimensional space from
these two images. From the previous analysis, we can know that different
viewing angles will be able to see different images. Because if we place the
grating perpendicular to the two eyes, the two eyes will see two different
images due to the different viewing angles of the two eyes to the grating,
resulting in a three-dimensional effect.
Usually, in order to obtain a better stereoscopic effect, it is often not only
made with two images, but composed of a series of stereoscopic images.
Sub-image, you can feel the three-dimensional effect.
UK Renishaw Grating
Place the grating between the two eyes, pay attention to keep the line angle
of the two eyes parallel to the grating, so the two eyes see the same image,
if the image is composed of a series of continuous animation, then when the
eyes move up and down or When the raster is flipped up and down, the angle of
the eyes and the raster will change, and we will also see successive images
one after the other, that is, see an animation or the effect of changing
What is a grating plate
It refers to a plastic material that has one side extruded into cylindrical
lines and the other side is a complete plane, and the distance between the
cylindrical lines is equal, which is called "grating". This grating plane can
be used for printing purposes. The output device outputs the file, and it is
pasted with the grating or directly printed on the grating plate, and the
effect as shown in the right figure can be presented, so that the animation
can directly display the changing image effect seen on the screen on the flat
Narrow angle gratings and wide angle gratings
When choosing a suitable grating plate, the angle of grating bending is very
important. Generally speaking, the most ideal grating for 3D stereo effect is
to use a narrow-angle grating plate, and its viewing angle is between 15
degrees and 44 degrees. It is the best, if you want to make the effect of
changing pictures or animation, the viewing angle of the wide-angle grating
board is about 44 degrees ~ 65 degrees is the most suitable grating board.
Types and uses of gratings commonly used in the market
Grating linear self-reset displacement transmission
Before making various grating visual effects, you must first understand the
characteristics, types, specifications, thickness, size, directionality, etc.
of the grating, so as to carefully judge how to make exquisite grating image
effects. Classification can be divided into the following categories.
Printing grating material: PET, PP, PVC, TPU, etc. PET, PP are hard plate
environmental protection materials, PVC, TPU are soft materials.
Raster line number effect: 50 LPI------------3D, Flip------------Common
60 LPI------------3D, Flip, Zoom, Twist, Animation
62 LPI------------3D, Flip, Zoom, Twist, Animation
75 LPI------------3D, Flip, Zoom, Twist, Animation------------Common materials
100 LPI------------3D,Flip------------Common materials
Principle Of Refraction
Using grating vision software to convert different patterns into grating line
numbers, and using the principle of grating refraction, different patterns are
presented at different angles. As shown in the figure on the right, gratings
of different specifications will have different refraction effects and
refraction angles. The viewing distance will also be different, so when
designing a grating effect drawing file, you must first understand the grating
before designing a design drawing that conforms to the characteristics of the
The grating effects can be divided into the following types: Stereo [3D], Two
Changes [Flip], Larger and Smaller [Zoom], Explosion [Explosion], Continuous
Action [Animation], Twist [Twist]....etc. It can be more simplified and
classified as: Stereo [3D], Flip [Flip], in which all the changing effects are
covered. These effects can be produced through many animation software,
drawing software, and web multimedia software on the market. The exploded
image file of the raster vision software can be used to synthesize the
exploded image into raster line numbers through the raster vision software,
and the plane effect can be made into a special effect of three-dimensional
[3D] and variable image [Flip].
3D Effect [Stereoscopic Image]
1. The layers must be independent and the image is complete.
2. The resolution of the image file is 300dpi.
3. The file format must be PSD file. [CMYK, RGB] can be used.
4. The background layer must bleed at least
1CM. From the grating equation d(sinα±sinβ)=mλ, it can be known that for the
same spectral series m, the relaxation light composed of different wavelengths
λ1, λ2, λ2... projected onto the grating at the same incident angle α, each
The interference maxima generated by different wavelengths are all located at
different angular positions; that is, diffracted light of different
wavelengths exits at different diffraction angles β. This means that, for a
given grating, the primary or secondary of the same order of different
wavelengths (which constitute the spectral lines of different wavelengths in
the spectrum of the same level of grating) do not overlap, but are arranged in
the order of wavelengths to form a Series of discrete spectral lines. In this
way, the composite light of various wavelengths mixed together and incident is
separated from each other after being diffracted by the grating. This is the
light-splitting principle of diffraction gratings.
Type of grating
Dot-matrix holographic stereo grating
It is a new type of stereoscopic expression (also called matrix stereoscopic
grating). Its material, viewing, and production are different from the
lenticular stereoscopic grating material and the slit stereoscopic grating
material. The produced image can be viewed from top to bottom, left and right.
The technology content is quite high. At present, the United States, Japan,
and Taiwan have this complete set of technology, which is mainly used for
anti-counterfeiting, and also applied to the display screen. In the near
future, stereoscopic TV will also enter our homes. Due to the complexity of
the dot-matrix holographic stereo grating imaging technology, the high cost of
installation and production, and the difficulty of counterfeiting, it is
difficult to be widely used in the near future. It is expected to be well
applied in the following fields:
1. Three-dimensional display of fine products and valuable cultural relics.
2. The image display of well-known large enterprises and multinational
corporations, and the display of high-end three-dimensional advertising light
3. Large-scale stereoscopic photo shooting of celebrities, film and television
stars, and bright models.
4. Anti-counterfeiting printing packaging and labels for high-end brand-name
He cylindrical grating has grooves on its surface;
1. Membrane material: There is no medium, and it must be glued to the organic
board and glass; the glass has different thicknesses, the thicker the
three-dimensional effect, the more obvious.
1) PET crystal mold material: thicker than PET film material, one side is
smooth, and the other side is smooth.
2) PET mold material: relatively poor; both sides are involved.
2. Sheet: Thicker than 2.5mm is called sheet. Less than 2.5mm is called film.
(called in the market)
3. Plate: There is a medium itself, no need to add another medium, the price
is relatively expensive, 120 yuan / square.
Slit grating: smooth surface, excellent effect with lighting. There are
Common resolution: the unit is (pixel/cm), don't make a mistake.
There are mainly two types of gratings: slit gratings and cylindrical
gratings. Slit gratings or line gratings are the earliest and more mature
gratings, and their imaging principle is the principle of pinhole imaging.
Because this kind of grating is relatively easy to make, and the technical
difficulty is not too big, so a very beautiful large-scale slit grating
three-dimensional light box advertisement appeared more than ten years ago.
Nowadays, some three-dimensional production companies are still willing to use
the slit grating three-dimensional light box to participate in the exhibition,
and the effect is good, but the slit grating three-dimensional light box has
the following defects: the light transmittance is only 20-30%, which is not
environmentally friendly, not energy-saving, and the lighting lamp consumes a
lot of energy. Large, heat is large, the outdoor brightness is not enough,
only suitable for indoor.
There are many kinds of lenticular gratings, which mainly include two
categories: plate materials and mold materials. The imaging principle is the
principle of arc lens refraction and reflection imaging. Cylindrical gratings
have great potential and can be used indoors and outdoors with or without
lights, and the market penetration rate is expanding. The lenticular film was
once popular for a while due to its price competitiveness, but due to the
gradual decline in the price of the lenticular lenticular plate, and the need
to paste the film and the technology to be improved, its competitiveness has
not been prominent.
1: The front (grating surface) of the film material has stable arc formation,
uniform arrangement, smooth magnification and observation, obvious convex
feeling when touched by hand, flat back without indentation; inferior products
can not meet the above standards, especially the back has obvious concave feel
If the indentation is entered, it is easy to cause false bonding, poor
resolution, and dizziness in the image, which is a fake and inferior product.
2: The lines of the qualified film are straight and straight, and there is no
oblique distortion. Straight line detection can be printed, or the film
grating can be lifted to face the window with the pane as a reference, and the
light transmittance can be directly checked visually.
3: After the qualified product composite board is accurately focused on the
specified thickness, the unqualified product and inferior product are
inaccurately focused. The specified 4mm and 5mm focus, but most of them can
only focus on 6mm and 8mm. The fluctuation is unstable and the range is too
large. This is a point often covered up by producers of inferior products,
which is a major misunderstanding of buyers. It can be identified by the line
spacing printed test strip provided by the seller.
Grating Spectrum Alignment
From the grating equation d(sinα±sinβ)=mλ, it can be known that when the
diffraction angle is not too large (such as in the first-order spectrum, when
it is close to the spectral normal region), the positions of the spectral
lines of different wavelengths are basically equal to their wavelength values.
Proportion. Therefore, the arrangement of each wavelength spectral line in the
grating spectrum is relatively uniform, and as the wavelength value increases
or decreases linearly, the position of the corresponding grating spectral line
(such as the distance from the grating normal) also changes linearly.
In the prism spectrum, light of different wavelengths is dispersed due to
different degrees of refraction. The refractive index change of the prism
material for different wavelengths is not linear with the wavelength. The
refractive index of the prism material changes much more in the short-wave
direction than in the long-wave region. Therefore, the arrangement of spectral
lines in the prism spectrum is not uniform. In the short-wave region, due to
the large dn/dλ, the spectral line arrangement is very sparse, while in the
long-wave region, due to the small dn/dλ, the spectral line arrangement is
very dense. Therefore, for the same wavelength difference, the distance
between the corresponding spectral lines is greater at short wavelengths than
at long wavelengths. Therefore, we say that the dispersion of prisms in the
ultraviolet region is larger than that in the visible and near-infrared
regions. Therefore, some UV-Vis spectrophotometers (especially high-end UV-Vis
spectrophotometers) use quartz prisms as pre-monochromators, which is the
The arrangement of the grating spectrum is relatively uniform, and the
distance between two spectral lines with the same wavelength difference in
different wavelength regions does not change much. The evenness of the grating
spectrum not only makes the spectrum more tidy and well-proportioned, but also
facilitates the preliminary judgment and estimation of the wavelength value of
the spectral line during qualitative analysis.
In addition, in terms of the wavelength distribution order of spectral lines,
gratings and prisms are also different; in the grating spectrum, the longer
the wavelength of light, the greater the diffraction angle value, the more the
spectral lines deviate from the grating normal. In the prism spectrum, the
longer the wavelength of light, the smaller the deflection angle, and the
closer the corresponding spectral line distribution is to the direction of the
From the grating equation d(sinα±sinβ)=mλ, it can be known that the
first-order (m=1) spectral line with wavelength λ, the second-order (m=2)
spectral line with wavelength λ/2, and the third-order spectral line with
wavelength λ/3 (m=3) spectral lines...all have the same diffraction angle.
That is, βλ, 1=βλ/2, 2=βλ/3, 3=…=βλ/m, m, which is the order overlap of the
diffraction grating spectrum. That is, the diffraction grating has spectral
lines of different orders and different wavelengths at the same position. When
performing high-resolution spectral research or spectral analysis in a
wide-band range, the order overlap of the grating spectrum is very obvious,
and strong measures must be taken to isolate or filter out the unwanted bands;
Monochromators, filters with corresponding wavelength bands, etc. Only in this
way can the interference of unnecessary order spectrum be avoided, and the
resolution of the UV-Vis spectrophotometer and the accuracy and reliability of
the analysis and test data can be ensured.
The spectrum formed by prism dispersion is just arranged into a single
spectrum in order of wavelength. The spectrum formed after dispersion by the
diffraction angle grating is the sum of all orders of spectrum including m=0,
±1, ±2, ±3.... The same grating can form a series of spectra of different
orders at different positions for the same incident composite light; there are
symmetrically distributed positive-order spectra and negative-order spectra on
both sides of m=0. Therefore, the multilevel of the grating spectrum
Subordination is principled, essential, and unavoidable. This characteristic
of the grating will cause many corresponding problems in the application of
the grating, which will directly affect the ultraviolet.
The spectral resolution and spectral detection of visible spectrophotometers
cause difficulties, which must be paid attention to by designers,
manufacturers and users of all UV-visible spectrophotometers.