Photocurrent Amplifier Circuit for Compact Multi-Disc Optical Pickups
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Solution Overview
Problem
Conventional photocurrent amplifier circuits are difficult to downsize due to the need for differential amplifiers for individual light receiving devices with different wavelengths, making it challenging to create a compact optical pick-up device compatible with multiple optical disc formats like CDs, DVDs, and Blu-ray Discs.
Innovation Solution
A photocurrent amplifier circuit with a differential amplifier configuration that includes parallel-connected amplifier devices, device selector switches, gain resistors, and light receiving devices, where inactivated amplifier devices are effectively open, allowing a single differential amplifier circuit to amplify photocurrents from multiple light receiving devices, reducing circuit space requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If differential amplifiers are set for individual light receiving devices with different wavelengths, then each light receiving device can be amplified independently with high accuracy, but the circuit size increases and becomes difficult to downsize
Solution Approach 1:
The patent merges multiple amplifier devices into a single differential amplifier circuit. The differential amplifier has a first input terminal connected to a first amplifier device and a second input terminal connected to a second amplifier device, allowing simultaneous amplification of multiple photocurrents in one integrated circuit structure, thereby reducing overall circuit area while maintaining amplification accuracy.
Solution Approach 2:
The differential amplifier circuit is designed to handle multiple wavelengths and light receiving devices universally. By configuring the differential amplifier with multiple input terminals and associated amplifier devices, a single circuit can process signals from different wavelengths (e.g., red and blue light receiving devices) without requiring separate dedicated amplifiers for each, achieving multi-functionality in a compact form.
2Area of stationary object
If a single differential amplifier circuit is used to amplify photocurrents from multiple light receiving devices, then circuit space is reduced and downsizing is achieved, but selective amplification control becomes more complex
Solution Approach 1:
The patent segments the control function by providing separate control inputs for each amplifier device within the differential amplifier circuit. Each amplifier device can be independently controlled to be active or inactive, allowing selective amplification of specific wavelengths or light receiving devices without requiring a completely separate circuit for each, thus managing control complexity while maintaining compact size.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enables a simple and downsized photocurrent amplifier circuit that selectively amplifies photocurrents from multiple light receiving devices, facilitating the creation of compact optical pick-up devices capable of supporting multiple disc formats with minimal internal output loss and high accuracy.
Implementation Method 1
By performing photo-electric conversion of the light reflected from the medium using light receiving devices which are set for the respective wavelengths, an electric signal is obtained
Data Source
AI summary
A photocurrent amplifier circuit is capable of selectively amplifying one or more of photocurrents which are respectively obtainable from plural receiving devices, and can be realized to have a small size. The photocurrent amplifier circuit includes: light receiving devices; amplifier devices associated with the light receiving devices; device selector switches which apply input voltages, which inactivate the amplifier devices, to the associated amplifier devices; and a differential amplifier circuit having an inverting input unit configured by the amplifier devices which are connected in parallel. The inputs of the amplifier devices and the output of the differential amplifier circuit are connected by gain resistances. The differential amplifier circuit amplifies, into voltage signals, photocurrents flowing from the light receiving devices which respectively associated with the gain resistances.