1 the advantages and disadvantages of plastic lenses products of high output, low price, and can realize lightweight product demand, but in the past accuracy is not high, unable to replace the traditional metal or glass and so on.
But in recent years due to the development of plastic materials and injection molding technology of diligence, have greatly changed the market.
In the field of optical components, plastic lenses already entered the era of high precision, from early disposable camera lenses, now need high precision head lens, plastic lenses give full play to the characteristic of plastic products, also transcends the bottleneck of plastic products.
Today, in the vigorous development of photovoltaic industry, this article will bring you into the plastic lens injection molding technology, understand the development process and related technology lenses.
Plastic products production speed is fast, suitable for large and automation of production, so easy to lower the price; plastic so good impact resistance; because plastic proportion is low, so the relative weight is lighter, can make the whole system to reduce weight; and the finished shape high degrees of freedom, system mechanism components and optical components can be consolidated into, reduce the number of parts, and simplify the system assembly; use of the advantages of this program, we can design special architecture of optical components.
Has advantages is not perfect, the disadvantage of plastic are: temperature characteristic is poor, and glass, plastic easily influenced by environment affect the optical properties.
Because once the heat temperature is low, thermal expansion coefficient is big, will affect the optical properties of optical components.
Precision is relatively low glass: plastic because of the material properties, so the inhomogeneity is higher, easy to produce contraction deformation, accuracy is not easy to control.
Scratch resistance is poor: plastic mechanical strength is low, material hardness is not hard as glass, therefore scraping resistance is poor.
Compared with optical glass, the less material types: due to the development of optical glass for a long time, so the plastic lenses and, by contrast, the types of material is less, and the refractive index is low, at about 1.
5 to 1.
Between June, in a narrow distribution.
Have double refraction phenomenon: which reduces the optical performance.
Must have certain production to meet economic benefits: plastic injection molding mold price is very expensive, a mold open, may need hundreds of thousands or millions of fees, so if you don't have reached a certain production scale, it is not in conformity with the economic benefits.
Size restrictions: plastic lenses in more than 30 100 mm on injection molding precision is not enough, will have the problem on the forming, also can say that the greater the size, the more accuracy is difficult to control.
2 the application of plastic lenses plastic lenses can be used in camera, digital camera with the viewing window, lens, lens;
The projector, rear projection TV with the camera lens;
The best example is used in the CD/DVD head pickup lens, grating lens, DOE, annual production of over hundreds of millions of stars;
And LCD panel on the back plate, also can see that the application of plastic lenses of light guide plate;
Among various kinds of optical system, optical components for micro-structure on plastic lenses, diffraction, refraction, spectral or polarization phenomenon, so it is suitable for application in Frenel lens, F -
Generally, plastic lenses are well suited for use in consumer photoelectric products, because this kind of product need to reduce the cost, accuracy and professional instruments for comparison is lower, while the output is large and request product lightweight, fits the characteristics of plastic lenses.
Chapter 2:2 - all kinds of plastic lenses injection forming technology
One of the basic concept of optical design lens injection molding technology includes optical design, mold, forming technology and measurement technology.
Now we are to talk about the basic concept of these technologies.
First of all, we come to optical design.
On the optical design, often need to consider two factors: the selection of materials and shape of the design.
Understand the main points of the optical design and injection molding, the relationship between the in discussions with optical designers have a concept, can also be for a designer were to design a lens and evaluate the feasibility and difficulty of judgment.
At the time of choosing optical plastic, is must pay attention to several optical properties, for example: loss of transmission spectrum and reflection, absorption and penetration rate, generally between 88 ~ 92%, and the refractive index, index of refraction stability, refers to the stability after injection molding, dispersion and birefringence characteristics.
Physical properties of the optical plastic in the optical design also need to be taken into account, such as plastic materials, forming shrinkage water imbibition, glass transition point temperature and heat deformation temperature, liquidity, specific gravity, strength, resistance to scratch, high temperature resistant, chemical, electrical resistance, impact resistance, etc.
In terms of shape design, optical design personnel should be considered to design the shape of plastic optical and resin properties, that is, different plastic materials have different characteristics, the optical design staff will use this feature to design easy to forming the shape of the keep thickness ratio and shape change, in a certain extent.
We take the CD and DVD head objective for example.
From this form, we can see something about the design of the optical system.
NA value, the greater the focus on behalf of the objective Angle, the greater the usually is associated with a smaller curvature radius, thickness more than, mould kernel processing and forming difficulty is higher.
Thickness ratio is an important indicator of measuring lens forming difficulty, when the thickness ratio is larger, forming the uneven contraction, the more difficult it is to shape the high-precision lenses.
The effective diameter refers to the optical path through the lens of real aperture size.
Lenses when forming, due to differences in thickness and temperature, on the edge of the central and shrinkage will be inconsistent, when the greater the effective diameter ratio, on behalf of the smaller in the invalid region around.
Minimum curvature radius and considered at the same time, the effective diameter usually determines the maximum surface slope, the surface slope, the greater the processing range and the measurement error will lead to greater, or may even produce cutter interference outside the measurement range of issues, this is a big problem for high precision of the lens.
Wave difference is the specification of the objective, can effectively quantify the optical properties of the lens, the lens tiny defect, can be received by wave differential expressed; therefore, the wave difference is smaller, on behalf of the objective lens of admissible error is smaller.
These error contains two curved surface shape error, error of tilt and decenter comprehensive performance.
This table for the optical lens injection molding precision comparison table, the radius of curvature changes as example, the lower order of lenses, the allowed error value of plus or minus 3 -
5%, but the precision of the lens, the required value is zero over one thousand.
That is, the more precise level of the lens, the allowed error value is small.
In general, the traditional injection molding technology of the precision of shape control can not meet the requirements of precision optical lenses, especially in recent years, plastic lenses after application gets bigger, the lens optical system need high accuracy, thickness than the big, more increase the difficulty of forming technology.
Precision forming of plastic lenses, no matter in the mold design, mould kernel processing, the forming condition and the lens measurement requires a high level of technology and equipment.