Calibrating method for calibrating measured distance of a measured object measured by a distance-measuring device according to ambient temperature and related device

• US 8,718,962 B2
• Filed: 03/11/2011
• Issued: 05/06/2014
• Est. Priority Date: 06/15/2010
• Status: Active Grant

• Current Assignee: PixArt Imaging Incorporated
• Original Assignee: PixArt Imaging Incorporated
• Inventors: Hsu, En-Feng, Liao, Chi-Chieh, Kao, Ming-Tsan
• Primary Examiner(s): Breene, John
• Assistant Examiner(s): Zhang, Ruihua
• Application Number:
  US13/045,529
• Publication Number:
  US 20110307206A1
• Time in Patent Office: 1,152 Days
• Field of Search: 702/97
• US Class Current: 702/97
• CPC Class Codes: G01C 25/00 Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass testing, calibrating or compensating compasses G01C17/38
• CPC Class Codes: G01C 3/10 using a parallactic triangle with variable angles and a base of fixed length in the observation station, e.g. in the instrument
• CPC Class Codes: G01S 17/48 Active triangulation systems, i.e. using the transmission and reflection of electromagnetic waves other than radio waves
• CPC Class Codes: G01S 3/784 using a mosaic of detectors
• CPC Class Codes: G01S 7/497 Means for monitoring or calibrating

Abstract

A calibrating method of calibrating a measured distance of a measured object measured by a distance-measuring device according to an ambient temperature includes providing a temperature sensor for measuring the ambient temperature of the distance-measuring device, calculating a calibrated imaging location of the measured object according to the ambient temperature and an imaging location of the measured object, and calibrating the measured distance according to the calibrated imaging location. In this way, when the distance-measuring device measures the measured object, the error due to the variation of the ambient temperature is avoided according to the calibrating method.

Claims

1. A distance-measuring device, comprising:

a lighting component, emitting a detecting light to a measured object to generate a reflective light;

a first lens, disposed in a transmission path of the reflective light;

an image sensor, the reflective light being focused by the first lens onto the image sensor for the measured object to form an image at a first imaging location,

a distance-calculating circuit calculating a measured distance between the distance-measuring device and the measured object according to the first imaging location, a focal length of the first lens, and a first predetermined distance between the lighting component and the image sensor;

a temperature sensor for measuring the ambient temperature of the distance-measuring device;

a temperature compensation calculating circuit for calculating a first calibrated imaging location according to the ambient temperature and the first imaging location, and providing the first calibrated imaging location to the distance-calculating circuit for calibrating the measured distance; and

a parameter-calculating circuit utilized for providing a first calibrating parameter and a second calibrating parameter to the distance-measuring circuit;

the first calibrating parameter is utilized for calibrating a first sensing-error angle and a second sensing-error angle of the image sensor;

the second calibrating parameter is utilized for calibrating a lighting-error angle rotated by the detecting light emitted by the lighting component;

wherein the distance-calculating circuit calculates the calibrated measured distance according to the following formula;

D_M=1/[A×

D<sub>CS—

CAB</sub>+B];

wherein D_M represents the calibrated measured distance;

A and B respectively represent the first calibrating parameter and the second calibrating parameter; and

D<sub>CS—

CAB</sub> represents the first calibrated imaging location;

wherein a relationship among the first calibrating parameter, the first sensing-error angle, and the second sensing-error angle is represented by the following formula;

A=(cos θ

_CS2×

cos θ

_CS1)/(D_F×

L);

wherein θ

_CS1 represents the first sensing-error angle θ

_CS2 represents the second sensing-error angle; and

L represents the first predetermined distance between the lighting component and the image sensor;

wherein a relationship between the second calibrating parameter and the lighting-error angle is represented by the following formula;

B=tan θ

_LD/L;

wherein θ

_LD represents the lighting-error angle.

2. The distance-measuring device of claim 1, wherein the temperature sensor measures a temperature of the first lens to obtain the ambient temperature when the distance-measuring device measures the measured distance.

3. The distance-measuring device of claim 1, wherein the temperature sensor measures a temperature of the image sensor to obtain the ambient temperature when the distance-measuring device measures the measured distance.

4. The distance-measuring device of claim 3, wherein the temperature sensor and the image sensor are integrated into a chip.

5. The distance-measuring device of claim 3, further comprising:

a temperature-sensing controlling circuit for controlling the temperature sensor to measure an operating temperature variation of the image sensor, and controlling the temperature sensor to measure a chip operation temperature of the image sensor when the distance-measuring device measures the measured distance, the temperature-sensing controlling circuit calculating the ambient temperature according to the chip operation temperature and the operating temperature variation.

6. The distance-measuring device of claim 5, wherein the temperature-sensing controlling circuit controls the temperature sensor to measure a temperature of the image sensor when the image sensor enters an operating mode, for obtaining a start-up temperature;

a delay period after the image sensor enters the operating mode, the temperature-sensing controlling circuit controls the temperature sensor to measure the temperature of the image sensor for obtaining a steady temperature; and

the temperature-sensing controlling circuit calculates the operating temperature variation according to the steady temperature and the start-up temperature.

7. The distance-measuring device of claim 6, wherein a delay period after the image sensor receives power to enter the operating mode, the temperature-sensing controlling circuit controls the temperature sensor to measure the temperature of the image sensor for obtaining the steady temperature;

and a delay period after the image sensor enters the operating mode from a power-saving mode, the temperature-sensing controlling circuit controls the temperature sensor to measure the temperature of the image sensor for obtaining the steady temperature.

8. The distance-measuring device of claim 1, wherein in a calibrating phase, the distance-measuring device measures a calibrating object with a second predetermined distance respectively at a first predetermined ambient temperature and a second predetermined ambient temperature, for obtaining a second imaging location and a third imaging location;

and the temperature compensation calculating circuit calculates a calibrating slope and a standard temperature according to the first predetermined ambient temperature, the second predetermined ambient temperature, the second imaging location, the third imaging location, and the second predetermined distance.

9. The distance-measuring device of claim 8, wherein the temperature compensation calculating circuit calculates a standard imaging location formed by the calibrating object when the distance-measuring device measures the calibrating object with the second predetermined distance at the standard temperature, according to the second predetermined distance.

10. The distance-measuring device of claim 8, wherein the temperature compensation calculating circuit calculates the calibrating slope and the standard temperature according to the following equations:

D_CS2−

D<sub>CS—

STD</sub>=SL_CAB×

(TEMP_PRE1−

TEMP_STD); and

D_CS3−

D<sub>CS—

STD</sub>=SL_CAB×

(TEMP_PRE2−

TEMP_STD);

wherein D_CS2, D_CS3, and D<sub>CS—

STD</sub> respectively represent the second imaging location, the third imaging location, the standard imaging location;

SL_CAB represents the calibrating slope; and

TEMP_PRE1, TEMP_PRE2, and TEMP_STD respectively represent the first predetermined ambient temperature, the second predetermined temperature, and the standard temperature.

11. The distance-measuring device of claim 10, wherein when the distance-measuring device measures the measured distance between the measured object and the distance-measuring device, the temperature compensation calculating circuit calculates a location compensation according to the calibrating slope, the standard temperature, and the ambient temperature;

and the temperature compensation calculating circuit calculates the first calibrated imaging location according to the first imaging location and the location compensation.

12. The distance-measuring device of claim 11, wherein the temperature compensation calculating circuit calculates the location compensation according to the following formula:

DC_DELTA=SL_CAB×

(TEMP_AMB−

TEMP_STD);

wherein DC_DELTA represents the location compensation, and TEMP_AMB represents the ambient temperature.

13. The distance-measuring device of claim 12, wherein the temperature compensation calculating circuit adds the first imaging location and the location compensation together to obtain the first calibrated imaging location.