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encoder

Encoder

In the joints of machine tools and industrial robots, numerous motors are used to accurately control their operations. To accurately detect the rotation angle of those motors, optical rotary encoders are widely used. Hamamatsu manufacturers Si photodiodes, photo ICs, LEDs, and so on that are suitable for such encoders and also provides customization of these devices.

Rotary encoders can be classified into two types: magnetic/electric induction type and optical type. The optical type detects rotation angles by detecting the on/off signals of light. This is achieved by placing a code wheel with fine pitch slits between a light emitter (e.g., LED) and photosensor (e.g., photodiode) and blocking and transmitting light.
High accuracy detection requires several features. For the photosensor Si diode, which makes up the encoder, photo detecting chip arrangement that supports complicated slip patterns and high-speed response are required. For the light emitting LED, uniform irradiation is required. Hamamatsu provides light emitters and photo sensors for both transmissive and reflective encoders.

optical encoders

Features of Hamamatsu photodiodes for encoders

Hamamatsu unique semiconductor process


Using on Hamamatsu unique semiconductor process technology, Hamamatsu manufacturers high-sensitivity, low-noise, highly reliable photodiodes that are suitable for photosensors for encoders. Further, Hamamatsu has a proven track record of manufacturing numerous industrial photodiodes.

 

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Optimum sensitive design for various applications


Hamamatsu can manufacture photodiodes with high sensitivity for the wavelength of the light source to be used, from visible light to infrared light.
A higher S/N can be expected by optimizing the sensitivity for the LED used in the optical encoder.

 

 

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Extensive mounting technology


Hamamatsu supplies various package products for many applications including automotive, industrial, and consumer.
Hamamatsu can suggest a wide variety of mounting solutions such as the combined mounting of the LED (used in the optical encoder) and photodiode and the miniaturization of photodiode packages.

 

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Package lineup

COB package

COB package

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

Chip carrier package

Chip carrier package

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



Example of special processing applied to Si photodiodes (customization)

Through-hole formation (MEMS processing)

Through-holes can be formed on Si photodiode chips by applying MEMS technology. This allows a current confinement type LED used in reflective encoders and the like to be mounted inside a hole of a Si photodiode chip. Further, the thickness of Si photodiode chip can be adjusted to align the height of the LED emitter to that of the photosensitive area of the Si photodiode.

Through-hole example

Through-hole example

Example in which an LED is mounted inside a through-hole of a Si photodiode

Example in which an LED is mounted inside a through-hole of a Si photodiode

It is possible to mount a Hamamatsu fiber optic plate (FOP) to the photosensitive area of a Si photodiode. Combining an FOP and Si photodiode allows the lens to focus at a position that is higher by the amount of the FOP thickness than the normal photosensitive surface. This makes it easier to mount a slip plate or other components closer to the photosensitive surface. Moreover, the photosensitivity directivity can be adjusted by using an FOP with a low NA.

Patent: JP 6383460 B

 

FOP example

FOP example

FOP directivity

FOP directivity

Example of a Si photodiode with an FOP

Example of a Si photodiode with an FOP




Low-reflectance light-shielding film

Reflectance vs. wavelength (reference value)

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

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Example of a Si photodiode with a light-shielding film

 

Example of a Si photodiode with a light-shielding film

Customization

Hamamatsu offers customization of photo ICs according to the specifications of the encoder the customer will structure. Below are examples of Hamamatsu’s initiatives and customizations of photo ICs for reflective encoders.
 

 ・ Monolithic structure of photodiode and peripheral circuit ⇒ Helps reduce the number of parts and mounting space on the customer side
 ・ Multifunctionalization using I2C ⇒ Enables multifunctionalization such as electron volume
 ・ Built-in LED and LED driver ⇒ Enables light receiving and emitting photo ICs with LEDs placed in the center of the chip
 ・ Compensation for variations in reference values (current, voltage) by trimming


Example 1: Example photo IC in which the photodiode and LED are integrated (monolithic structure)

This is an example of Hamamatsu converting to photo IC a photodiode and peripheral circuit discretely configured by a customer.

Example photo IC in which the photodiode and LED are integrated

Example photo IC in which the photodiode and LED are integrated

Example 2: Example of instrumentation amplifier (1/f noise, thermal noise considered)

We realized noise reduction with a circuit structure that considers 1/f noise and thermal noise.

Example of instrumentation amplifier

Features of Hamamatsu LEDs for encoders

Hamamatsu unique semiconductor process

Hamamatsu unique semiconductor process Using on Hamamatsu unique semiconductor process technology, Hamamatsu manufacturers output, highly reliable LED that are suitable for light emitters for encoders.
 
 

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Extensive product lineup

Hamamatsu produces and provides various types of LEDs for a wide variety of applications including automotive, industrial, and consumer. For optical encoders, Hamamatsu provides collimated LEDs that can irradiate low-focus/dispersion, uniform collimated light suitable for constructing high accuracy encoders.

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Improvement of liability by refining the crystal structure: Current confinement type LEDs (Point source LEDs)

Example of a current confinement type LED chip design (unit: μm)

Example of a current confinement type LED chip design

Example of a current confinement type LED

Example of a current confinement type LED



Package lineup

High reliability, high collimation CAN package

High reliability, high collimation CAN package

Operating temperature: -30 to +105 ℃
Storage temperature: -40 to +105 ℃
Packing method: 100 pcs/bag

   
Compact, narrow directivity COB package

Compact, narrow directivity COB package

Operating temperature: -30 to +85 ℃
Storage temperature: -40 to +100 ℃
Packing method: 2000 pcs/reel

   


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