Antenna Shaping for Capacitive Human Body Sensor Sensitivity
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Solution Overview
Problem
Capacitive human body sensors in image forming apparatuses face challenges in reducing sensitivity differences between corner and non-corner portions of the antenna, leading to false detection when a person stands near the device, which increases power consumption and costs when multiple detection circuits are used.
Innovation Solution
The antenna is shaped to reduce sensitivity differences by being wired in a curve without forming corners in the corner portion, being thinner in the corner portion than in other areas, or wired without meandering in the corner portion and meandering in other areas, thereby equalizing the area of the antenna included in the flat areas corresponding to the human hand or finger performing the return operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the antenna is wired along the periphery of the detection target area, then the detection coverage is improved, but the sensitivity difference between corner and non-corner portions increases causing false detection
Solution Approach 1:
The antenna is designed with different line widths at different locations: the antenna line has a first width at corner portions and a second width at non-corner portions. This local variation in antenna geometry compensates for the inherent sensitivity differences at corner versus non-corner areas, achieving uniform detection sensitivity across the entire detection target area while maintaining comprehensive coverage.
2Measurement precision
If multiple detection circuits are used to reduce false detection, then the detection accuracy is improved, but the device complexity and power consumption increase
Solution Approach 1:
Instead of adding multiple detection circuits, the invention changes the geometric parameters of the single antenna structure by varying the antenna line width at different locations. This parameter modification allows the single detection circuit to achieve uniform sensitivity across the detection area, eliminating the need for multiple circuits while maintaining high detection accuracy.
3Measurement precision
If the antenna line width is increased at corner portions to compensate for sensitivity, then the detection sensitivity at corners is improved, but the overall power consumption increases
Solution Approach 1:
The antenna line width is locally adjusted only where needed: wider at corner portions to compensate for reduced sensitivity, and narrower at non-corner portions to minimize power consumption. This localized geometric modification optimizes detection performance at critical areas without unnecessarily increasing power consumption across the entire antenna structure.
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 approach reduces false detection of user return operations, enhances sensitivity uniformity, and maintains low power consumption by minimizing the difference in sensitivity between corner and non-corner portions of the antenna, thus effectively transitioning the device from a power saving mode to a normal mode.
Implementation Method 1
The capacitive human body sensor detects the proximity of a human hand or the like by using a change in storage capacity of electrical energy called capacitance. The capacitance is always generated between two conductors arranged in space.
Implementation Method 2
When a finger or hand of a human body being a conductor approaches the antenna 103 as illustrated in FIG. 12, a few picofarads of stray capacitance (parasitic capacitance=capacitor) is generated between the finger or hand and the antenna 103.
Data Source
AI summary
An image forming apparatus includes a capacitive human body sensor that detects an operation to return to a normal mode from a power saving mode consuming less power than the normal mode, wherein an antenna of the human body sensor is wired along a periphery of a predetermined detection target area which can receive the operation to return from a user, and a difference in sensitivity between a corner portion and a part other than the corner portion of the antenna is reduced by shaping the antenna at least to be wired in a curve without forming a corner in the corner portion, to be thinner in the corner portion than in the part other than the corner portion, or to be wired without meandering in the corner portion and wired while meandering in the part other than the corner portion.