We have posted “Frequently Asked Questions” and answers from our customers.

I would like to know about types of glass.

There are basically two types of glass products, plate glass and optical glass materials.

White crown glass(such as B270), D263, or Soda-lime glass are most typically used as plate glass. Silica, borosilicate glass (Tempax, Pyrex) alkali-free glass and low α ray glass are widely used for each usage. The optical glass, for optical parts production, will be selected according with the specification of the refractive index, etc. HOYA, OHARA, SCHOTT are leading manufacturers. Now crystal glass (click here for more information) is increasingly used for laser or infrared ray. Furthermore, color filters which have optical characteristics themselves are also widely used.
I would like to know about ND (neutral density) filters.

It is a filter which attenuates light of all colors of the captured image equally.

This filter is usually produced by depositing metal film such as Cr, Inconel on glass and has been used for portable camera, digital camera, or security camera. In the case of metal film, dielectric multilayer ND and kneading type ND filters are also used to prevent surface reflection. There are also plastic film types other than glass.
What kinds of deposition do you use in optics?

There are two main types.These are as follows.

  1. Metal film Al (aluminum) / Au (gold) / Ag (silver) / Cr (chromium) / Ni (nickel) / Cu (copper) / Pt (platinum) (absorbing film) AL enhanced reflection mirror (AL+SiO2) telecommunication mirror (Au)/ light exclusion (Cr+Cr2O3)/ chromium oxide
  2. Dielectric film These are as follows. AR coat/ multi coat (antireflection, non-reflective coat) (oxide film)MgF2・Al2O3・SiO2・OS-50・OH-5 (deposition material specification) (multilayer film) IR cut filter / UVIR cut / Infrared cut filter  BGR (blue, green, red) / YMC(yellow, magenta, cyan) Trimming coat (filter) BPF/ bandpass filter LPF/ long pass filter SPF/ short pass filter CM (cold mirror, total-reflection mirror)
In addition, for other than optical characteristics use, you can use water repellent coat (antifouling coat), hydrophilic film (use titanium or silica), or conductive film (ITO/ antistatic coat) for surface treatment.
I want to ask optical design, what data must I prepare?

In optical design, more than twenty specification items will be required as follows.

Usage and purpose, environmental working condition, brightness (F-number), numerical aperture (N.A.), focal length (f), size of subject image, object to image distance, object distance, working distance, back focal length, flange back, magnification, MTF angle of view, distortion tolerance, wavelength region, light source, photo detector, lens dimension (limit of the outer shape), lens configuration, lens mount shape, weight limit, size of permissible circle of confusion, coaxial gap, etc. Since these are a lot of items that require expertise, we will offer you suggestions concretely in consultation, if you tell us your vague idea like “I want to do such a thing”.
How do you select the glue when I want bond certain materials with glass?

Since there are many kinds of glues and the usage and conditions are very complicated, we perform the selection of the adhesive carefully.

We use low viscosity and high viscosity adhesives in right place by usage (temporal or filling up adhesion). We select the glue by considering the conditions such as object, usage environment, usage wavelength (light source), accuracy (parallelism), adhesion speed and bonding procedure (UV hardening, heat hardening, silicon, optical contact, air gap, air contact). For example, it is necessary to select the same refractive index and transparency for the adhesion of glass, so that we select the most suitable adhesive to meet its usage and purpose. Now we can bond different materials together such as glass with plastic.
What substances are used for deposition?

There are two main types of substances for deposition, dielectric and metal film.

Regarding to dielectric film, there are several substances such as TiO3, SiO2, Nb2O5, Ta2O5, MgF2, etc. We deposit high refractive substance and low refractive substance combining together by turns. As for metal film, there are several substances such as Au, Ni, Cr, Al2O3, Ag, Cu, Al, ZnO, Cr2O3, Pt, Inconel, etc. In addition to the substances explained above, there are ITO which is electric conductive or fluorocarbon polymers which is for surface protection of objects (water repellent coat, antifouling coat).
I want to use IR cut feature. What type do you have?

There are two types of IR cut filter for CCD, CMOS, absorbent type and reflective type.

Regarding to absorbent type, there are absorbing glass, color glass or absorbing filter etc., and these glass materials themselves cut infrared rays harmful for CCD, CMOS. They have no angular dependence. They are used with low pass filter as a couple. As for reflective type, we deposit about 40 layers on glass or film. As depositing method, there are non-shift Film formation such as digital sputter, sputtering, IAD, etc., and general EB deposition. We provide various kinds of IR cut filter for single-lens reflex camera, digital camera, cellular phone with built-in camera, on-board use, day and night type monitoring of burglar (security), scanner, etc. Recently, thin-type t0.145 glass, α ray cut glass, or films are increasingly used as IR cut materials. Moreover, through the shaping process, we cut not only rectangle and square but also round or atypical.
What kind of glass cutting do you have?

When we cut plate glass linearly, we have some methods such as dicing, scriber cutting, slice cutting, etc.

We have specific machine corresponding to multi blade in dicing or slicing. We use wire saw (cutting), to cut down a glass block. We also adopt the method using peripheral cutting edge or inner diameter blade and recently laser cutting, precision blast cutting, or water jet machining. We correspond to centering (rounding), polygonizing or atypical processing by NC centering machine using digital cam.
What is the refractive index?

It means specific proportion when traveling light changes its angle of direction at the different medium border.

We call the ratio refractive index (Nd), in which light is refracted (as 1.00 in vacuo), when it enters liquid or solid passing light through from atmosphere (vacuo). Glass materials have a variety of refractive index such as high or low refractive index. (for example, BK7 (1.5168), Synthetic silica (1.4585)). The refractive index also varies by wavelength in measurement.
What are the molding materials for plastics?

For optical products, most generally used materials are acryl (PMMA), polycarbonate (PC) (Panrite, Iupilon, Dialex), Polystyrene (PS), Zeonex (480R, 330R, 340R, E48R), Atron, Apel, Topas, Ultem, etc. We also have transparent silicone rubber and so-called smoked materials, made of plastic resin which themselves transmit infrared rays.

As for molding materials corresponding to usage, there are ABS, PET, Polystyrene PS, Polyvinyl Chloride (PVC), Polypropylene, APET, CPET, Duracon, Duranex, Liquid Crystal Polymer, PPO, Elastomer, etc.
What kind of crystalline material do you have?

Calcium fluoride (alias fluorite) is one of the frequently used crystalline materials, which has stable properties ranging from UV to IR.

Silicon (Si), germanium (Ge), zinc selenide (ZnSe) are also used for infrared window application. Alumina (alias sapphire, Al2O3) which transmits from near infrared to infrared region is also excellent in the aspect of mechanical strength, optical properties, electrical properties, and thermal conductivity. In addition to substances explained above, there are barium fluoride (BaF2), lithium niobate (LiNbO3), BBO (βBaB2O4), lithium fluoride (LiF), sodium chloride (NaCl), potassium bromide (KBr), potassium chloride (KCl), cesium iodide(CsI) corresponding to usage.
I want to create a filter that transmits a certain wavelength while rejecting other wavelengths. Please tell me about a bandpass filter (BPF).

A band pass filter (alias interference filter) is the one which transmits the specific range of wavelength selectively out of polychromatic light, while shutting out unnecessary spectrum completely by reflection and/or absorption.

A wavelength range of transmittance is defined by half-value width and we can create various kinds of filter such as broadband bandpass filter, narrowband bandpass filter, short-pass filter, long-pass filter, etc. Generally BPF tends to decline quantity of transmitted light in case of enlarging incidence angle, because of causing separation of polarization characteristic. As for our bandpass filter, there are basically two types of filters, we provide you based on usage and conditions.

  1. (1)Method to create by dielectric only The advantage of this method is to achieve high level transmittance and guarantee flexibility in design. We design and produce centre wavelength, transmission bandwidth, etc. corresponding to your request. In case of widening inhibition zone, production becomes more challenging.
  2. (2)Method to create by dielectric plus color glass This method, which improves attenuation within the inhibitions zone by absorption of color glass, enables to reduce number of layers as well as is highly cost effective. However, flexibility in design is narrow because types of glass are limited.

We use them for LD/LED sensor, noise reduction, separation and composition of optical signal, infrared sensor, near-field switch for illumination sensor, biometrics sensor, splitter for optical communication, ornament and lighting equipment, measuring equipment, inspection equipment for semiconductor and related devices, etc.