User detection circuit with environmental light detector

• US 6,518,561 B1
• Filed: 11/01/2000
• Issued: 02/11/2003
• Est. Priority Date: 11/05/1999
• Status: Expired due to Fees

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Miura, Shinichiro
• Primary Examiner(s): Kim, Robert H.
• Assistant Examiner(s): Kao, Chih Cheng G
• Application Number:
  US09/704,146
• Time in Patent Office: 832 Days
• Field of Search: 250/221, 250/222.1, 250/208.2, 250/208.4, 250/214.B, 250/214.AL, 340/555, 340/556, 340/557, 345/48, 345/52, 345/102, 345/207, 713/324, 713/321
• US Class Current: 250/221
• CPC Class Codes: G06F 1/3203 Power management, i.e. event-based initiation of a power-saving mode
• CPC Class Codes: G06F 1/3231 Monitoring the presence, absence or movement of users
• CPC Class Codes: G06F 1/3265 Power saving in display device
• CPC Class Codes: G09G 2330/022 in absence of operation, e.g. no data being entered during a predetermined time
• CPC Class Codes: Y02D 10/00 Energy efficient computing, e.g. low power processors, power management or thermal management

Abstract

A user sensor allows a phototransistor to receive infrared rays that are emitted from an infrared diode in front of a display apparatus and reflected from a user, and a detection signal in response to a quantity of light is inputted to the positive input terminal of a correction circuit formed by a differential amplifier. An illumination sensor receives light in the environment of the display apparatus, and a detection voltage in response to the quantity of light is divided and inputted to the negative input terminal of the correction circuit. The quantity of infrared rays that are included in the environmental light detected by the illumination sensor is subtracted from the infrared rays that enter the user sensor, providing a correct sensor output representing a state of user detection.

Claims

1. A user detection circuit for a display apparatus that detects an absence of a user and that switches from a normal operation to a power-saving standby operation to allow the display apparatus to suspend displaying and enter a standby mode, comprising:

a user sensor for detecting the user in front of a display screen;

an illumination sensor for detecting a brightness of an environment of the display screen;

correction means for correcting a detection signal of the user sensor based on a detection signal of the illumination sensor; and

determination means for determining whether the user is present based on the signal corrected by the correction means,

wherein switching between the normal operation and the power-saving standby operation of the display apparatus is performed based on a result of a determination by the determination means, and

wherein the correction means is a subtraction means for subtracting a signal generated when a direct-current component in the detection signal of the illumination sensor is interrupted and when a direct-current component included in the detection signal of the user sensor is interrupted.

2. The user detection circuit as claimed in claim 1, further comprising switch means for driving the user sensor in an alternating manner.

3. The user detection circuit as claimed in claim 1,

wherein the user sensor is a reflection-type infrared detection sensor.

4. The user detection circuit as claimed in claim 1,

wherein the illumination sensor is used as a sensor for adjusting a brightness of the display apparatus.

5. The user detection circuit as claimed in claim 4,

wherein a detection voltage signal of the illumination sensor is integrated by an integration circuit, and a brightness of the display screen is adjusted based on a level of output voltage of the integration circuit.