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The joints of machine tools and industrial robots have many motors for accurately controlling the operation.
To accurately detect the rotation angles of motors, optical encoders with Si photodiodes and LEDs are widely used.
Hamamatsu manufactures Si photodiodes, photo ICs, LEDs, and the like suitable for optical encoders and also provides customization.

Features of Hamamatsu photodiodes for encoders

Original semiconductor process

Based on original semiconductor process technology, Hamamatsu manufactures high-sensitivity, low-noise, highly reliable photodiodes suitable for encoder photosensors.
We also have the experience of manufacturing various industrial photodiodes.


Optimal sensitivity design for each application

From visible light to near infrared, Hamamatsu can manufacture photodiodes that are highly sensitive to the wavelength of the light source to be used.
By applying the most suitable sensitivity design to the LED used in the optical encoder, high S/N can be expected.


Various packaging technology

We supply various package products for numerous applications including automotive, industrial, and consumer uses.
We offer a variety of packaging methods such as incorporating LED and photodiode used in an optical encoder into a single package.


Package lineup

COB package


Operating temperature: -40 to +100 °C
Storage temperature: -40 to +100 °C
Packing method: 1000 pcs/reel

Chip carrier package


Operating temperature: -40 to +100 °C
Storage temperature: -40 to +100 °C
Packing method: 100 pcs/tray or 1000 pcs/reel

Example of special processing applied to Si photodiode (Customization)

Through-hole formation (MEMS processing)

A through-hole can be formed in Si photodiode chip by applying MEMS technology.
This allows a LED chip used in reflective encoders to be mounted inside a hole of Si photodiode chip.
Moreover, the thickness of the Si photodiode chip can be adjusted in order to align the height of the LED emitter mounted inside the hole to the height of the photosensitive area of the Si photodiode.

Example of Si photodiode with through-hole


Example of LED mounted in the through-hole of Si photodiode


Si photodiode with FOP

It is also possible to mount a Hamamatsu FOP (Fiber Optic Plate) on the photosensitive area of Si photodiode.
Combining the FOP with the Si photodiode allows the lens focal point to be set to a position higher than the normal photosensitive area by the thickness of the FOP.
This makes it easier to mount the encoder’s slit plate close to the photosensitive area.
In addition, the directivity of photosensitivity can be adjusted by combining FOP with a low NA.


Image of Si photodiode with FOP


Directivity of Si photodiode with FOP


Low reflectance film

Improvement in the signal to noise ratio

Low reflectance film covering metal lines on the photodiode chip prevents incident light from reflecting.
By reducing reflecting light, improvement in the signal to noise ratio
can be expected.


Reflectance of the low reflectance film (reference value)

The reflectance of near-infrared light often used in optical encoders is significantly reduced.


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