# Patent

## Title
Distance-measuring device of measuring distance according to variation of imaging location and calibrating method thereof

## Abstract

A distance-measuring device is utilized for measuring a measured distance between a measured object and the distance-measuring device. The distance-measuring device reduces the effect of a background light and a flicking light by removing the part corresponding to the background light and the flicking light from light-sensed signals generated by an image sensor of the distance-measuring device. In addition, the distance-measuring device calculates a calibrating parameter for calibrating an assemble-error angle of the distance-measuring device, according to an imaging location of a reflective light obtained by measuring a calibrating object with a predetermined distance. In this way, the distance-measuring device can correctly calculate out the measured distance.

## Background
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a division of U.S. application Ser. No. 12/842,045 filed on Jul. 23, 2010.


BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a distance-measuring device, and more particularly, to a distance-measuring device of measuring distance according to variation of imaging location.
2. Description of the Prior Art
In the prior art, the distance-measuring device emits a detecting light to a measured object, and receives a reflecting light generated by the measured object reflecting the detecting light. The distance-measuring device calculates the distance between the measured object and the distance-measuring device according to the variation of the imaging location of the reflecting light. However, when the distance-measuring device senses the reflecting light from the measured object, the distance-measuring device is affected by the background light and the flicker phenomenon (for instance, the flicker of the fluorescent lamp caused by the frequency of the AC power supply) at the same time. Hence, the distance-measuring device calculates an incorrect measured distance because of the above-mentioned reason. Moreover, since the locations of the components of the distance-measuring device may shift or rotate due to the assembling error during the fabrication, the accuracy of the measured distance obtained by the distance-measuring device is further deteriorated, causing a great inconvenience.
SUMMARY OF THE INVENTION
The present invention provides a distance-measuring device of measuring distance according to variation of imaging location. The distance-measuring device has a lighting component, a first lens, and an image sensor. The lighting component is utilized for emitting a detecting light to a measured object for the measured object generating a reflecting light. The first lens is utilized for focusing a background light or the reflecting light. The image sensor is utilized for sensing an energy of a light focused by the first lens so as to generate M light-sensed signals. The distance-measuring device comprises a lighting/sensing controlling circuit, and a distance-calculating circuit. The lighting/sensing controlling circuit is utilized for controlling the lighting component to emit the detecting light and controlling the image sensor to sense the energy of the light focused by the first lens at the same time during a distance-sensing phase, so that the image sensor generates M first light-sensed signals, and for controlling the lighting component not to emit the detecting light and controlling the image sensor to sense the energy of the light focused by the first lens at the same time during a noise-sensing phase, so that the image sensor generates M second light-sensed signals. M represents a positive integer. The distance-calculating circuit is utilized for determining an imaging location of the reflecting light on the image sensor according to the M first light-sensed signals and the M second light-sensed signals, and calculating a measured distance between the distance-measuring device and the measured object according to the imaging location, a focus length of the first lens, and a predetermined distance between the lighting component and the image sensor.
The present invention further provides a calibrating method. The calibrating method is utilized for calibrating a distance-measuring device of measuring distance according to variation of imaging location. A lighting component of the distance-measuring device emits a detecting light to a measured object. The measured object reflects the detecting light to an image sensor of the distance-measuring device for imaging at a first imaging location. The distance-measuring device calculates a measured distance between the measured object and the distance-measuring device according to the first imaging location, a focus length of a first lens of the distance-measuring device, and a predetermined distance between the lighting component and the image sensor. The calibrating method comprises the lighting component of the distance-measuring device emitting the detecting light to a calibrating object, and the calibrating object reflecting the detecting light to the image sensor of the distance-measuring device for imaging at a second imaging location, calculating out a calibrating parameter for calibrating an assembling-error angle according to a known distance and the second imaging location, and the distance-measuring device calculating out the calibrated measured distance according to the calibrating parameter. A distance between the distance-measuring device and the calibrating object is the known distance.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 and FIG. 2 are diagrams illustrating the structure and the operation principle of a distance-measuring device according to the present invention.
FIG. 3 is a diagram illustrating the operation principle of the distance-measuring device reducing the flicker phenomenon according to the present invention.
FIG. 4 is a diagram illustrating a calibrating method of calibrating the lighting-error angle of the detecting light emitted by the lighting-component.
FIG. 5 and FIG. 6 are diagrams illustrating a calibrating method of calibrating sensing-error angles rotated by the image sensor because of the assembling error.
FIG. 7 is a diagram illustrating the structure of an image sensor according to a first embodiment of the present invention.
FIG. 8 is a diagram illustrating the operation principle of detecting the imaging location of the reflecting light by the image sensor of FIG. 7.
FIG. 9 is a diagram illustrating the structure of an image sensor according to another embodiment of the present invention.
FIG. 10 is a diagram illustrating the operation principle of detecting the imaging location of the reflecting light by the image sensor of FIG. 9.
FIG. 11 is a diagram illustrating the structure of an image sensor according to another embodiment of the present invention.



DETAILED DESCRIPTION
The present invention provides a distance-measuring device of measuring distance according to the variation of the imaging location. The distance-measuring device of the present invention reduces the effect of the background light and the flicker phenomenon by removing the parts of background light and the flicking light from the light-sensed signals generated by the image sensor. In addition, the present invention further provides a calibrating method for calibrating the assembling error of the distance-measuring device, so as to improve the accuracy of measuring the distance.
Please refer to FIG. 1 and FIG. 2. FIG. 1 and FIG. 2 are diagrams illustrating the structure and the operation principle of a distance-measuring device 100 according to the present invention. The distance-measuring device 100 measures distance according to the variation of the imaging location. More particularly, the distance-measuring device 100 measures the measured distance DM between the measured object MO and the distance-measuring device 100. The distance-measuring device 100 comprises a lighting/sensing controlling circuit 110, a lighting component 120, an image sensor 130, a distance-calculating circuit 140, a parameter-calculating circuit 150, and a lens LEN1. The coupling relations between the components of the distance-measuring device 100 are shown in FIG. 1, and hence will not be repeated again for brevity.
The lighting/sensing controlling circuit 110 generates a lighting pulse signal SLD, a shutter pulse signal SST, a phase signal Sp, a reading signal SRE, and a known-distance signal SD. Measuring the distance by the distance-measuring device 100 can be divided into two phases: 1. distance-sensing phase; 2. noise-sensing phase. During the distance-sensing phase, the lighting/sensing controlling circuit 110 generates the lighting pulse signal SLD representing “lighting” and the shutter pulse signal SST representing “turning-on”, wherein the pulse widths of the lighting pulse signal SLD representing “lighting” and the shutter pulse signal SST representing “turning-on” are both equal to TC. Then the lighting/sensing controlling circuit 110 generates the reading signal SRE representing “reading” and the phase signal SP representing “sum”, wherein the pulse widths of the reading signal SRE representing “reading” and the phase signal SP representing “sum” are both equal to TR. During the noise-sensing phase, the lighting/sensing controlling circuit 110 generates the shutter pulse signal SST representing “turning-on” and the lighting pulse signal SLD represents “not-lighting” at the time, wherein the pulse width of the shutter pulse signal SST representing “turning-on” during the noise-sensing phase is still equal to TC. Then the lighting/sensing controlling circuit 110 generates the reading signal representing “reading” and the phase signal SP representing “noise”, wherein the pulse widths of the reading signal SRE representing “reading” and the phase signal SP representing “noise” are still both equal to TR.
The lighting component 120, according to the lighting pulse signal SLD, emits a detecting light LID to the measured object MO, so that the measured object MO generates a reflecting light LRD. More particularly, when the lighting pulse signal SLD represents “lighting”, the lighting component 120 emits the detecting light LID to the measured object MO; when the lighting pulse signal SLD represents “not-lighting”, the lighting component 120 does not emit the detecting light LID. In addition, the lighting component 120 can be a Light-Emitting Diode (LED) or a laser diode. When the lighting component 120 is an LED, the distance-measuring device 100 selectively comprises a lens LEN2 for focusing the detecting light LID emitting to the measured object MO.
The lens LEN1 focuses a background light LB or the reflecting light LRD to the image sensor 130. The image sensor 130 comprises M sensing units CS1 ̃CSM. In the present embodiment, the M sensing units CS1 ̃CSM are illustrated to be arranged side by side for example. The width of each sensing unit is equal to a pixel width WPIX. That is, the total width of the M sensing units CS1 ̃CSM arranged side by side is equal to (M×WPIX). The sensing units CS1 ̃CSM sense the energy of the light focused by the lens LEN1 according to the shutter pulse signal SST. More particularly, when the shutter pulse signal SST represents “turning-on”, the sensing units CS1 ̃CSM sense the energy of the light (for example, the background light LB or the reflecting light LRD) focused by the lens LEN1 so as to generate the light-sensed signal; when the shutter pulse signal SST represents “turning-off”, the sensing units CS1 ̃CSM do not sense the energy of the light focused by the lens LEN1. For example, when the shutter pulse signal SST represents “turning-on”, the sensing unit CS1 senses the energy of the light focused by the lens LEN1 so as to generate the light-sensed signal SLS1, the sensing unit CS2 senses the energy of the light focused by the lens LEN1 so as to generate the light-sensed signal SLS2, . . . , and the sensing unit CSM senses the energy of the light focused by the lens LEN1 so as to generate the light-sensed signal SLSM. In addition, when the reading signal SRE represents “reading”, the sensing units CS1 ̃CSM outputs the light-sensed signal SLS1 ̃SLSM, respectively.
The distance-calculating circuit 140 comprises a plurality of storing units for respectively storing the light-sensed signals SLS1 ̃SLSM outputted by the sensing units CS1 ̃CSM. The distance-calculating circuit 140 sets the attributes of the received light-sensed signals according to the phase signal SP. In the present embodiment, the distance-calculating circuit 140 is illustrated to comprise M storing units M1 ̃MM for example. When the phase signal SP represents “sum”, the storing units M1 ̃MM set the attributes of the received light-sensed signals positive. That is, the received light-sensed signals SLS1 ̃SLSM are marked as positive light-sensed signals SLS1+ ̃SLSM+ according to the phase signal SP representing “sum”. When the phase signal SP represents “noise”, the storing units M1 ̃MM set the attributes of the received light-sensed signals negative. That is, the received light-sensed signals SLS1 ̃SLSM are marked as negative light-sensed signals SLS1− ̃SLSM− according to the phase signal Sp representing “noise”. The distance-calculating circuit 140 calculates the measured distance DM according to the positive light-sensed signals SLS1+ ̃SLSM+ and the negative light-sensed signals SLS1− ̃SLSM−. The operation principle of the distance-calculating circuit 140 calculating the measured distance DM is illustrated as below.
As shown in the left part of FIG. 2, during the distance-sensing phase, the lighting/sensing controlling circuit 110 generates the lighting pulse signal SLD represents “lighting” for the lighting component 120 emitting the detecting light LID to the measured object MO, so that the measured object MO generates the reflecting light LRD. Meanwhile, the lighting/sensing controlling circuit 110 generates the shutter pulse signal SST representing “turning-on” for the sensing units CS1 ̃CSM sensing the energy of the reflecting light LRD and the background light LB, so that the sensing units CS1 ̃CSM generate the light-sensed signals SLS1 ̃SLSM respectively. Then the lighting/sensing controlling circuit 110 outputs the reading signal SRE representing “reading” for the image sensor 130 outputting the light-sensed signals SLS1 ̃SLSM to the distance-calculating circuit 140, and the lighting/sensing controlling circuit 110 generates the phase signal SP representing “sum” for indicating the distance-calculating circuit 140 that the received light-sensed signals are the light-sensed signals of the distance-sensing phase. That is, the received light-sensed signals of the distance-calculating circuit 140 at the time are the positive light-sensed signals SLS1+ ̃SLSM+. It is assumed that the reflecting light LRD is mainly focused on the sensing unit CSK during the distance-sensing phase (as shown in FIG. 2). The values of the received positive light-sensed signals SLS1+ ̃SLSM+ are shown in the right upper part of FIG. 2. The sensing unit CSK senses the background light LB and the reflecting light LRD (that is, the measured object MO images on the sensing unit CSK). Therefore, the light-sensed signal SLSK+ is equal to the sum of the energy BK, which is accumulated by the sensing unit CSK sensing the background light LB, and the energy RK, which is accumulated by the sensing unit CSK sensing the reflecting light LRD. The other sensing units only receive the background light LB. For example, the light-sensed signal SLS1+ is equal to the energy B1, which is accumulated by the sensing unit CS1 sensing the background light LB; the light-sensed signal SLS2+ is equal to the energy B2, which is accumulated by the sensing unit CS2 sensing the background light LB; . . . ; the light-sensed signal SLSM+ is equal to the energy BM, which is accumulated by the sensing unit CSM sensing the background light LB.
As shown in the left part of FIG. 2, during the noise-sensing phase, the lighting/sensing controlling circuit 110 generates the shutter pulse signal SST representing “turning-on” for the sensing units CS1 ̃CSM sensing the energy of the light focused by the lens LEN1 so as to generate the light-sensed signals SLS1 ̃SLSM. Meanwhile, the lighting/sensing controlling circuit 110 generates the lighting pulse signal SLD represents “not-lighting”. Hence, the lighting component 120 does not emit the detecting light LID to the measured object MO, so that the measured object MO does not generate the reflecting light LRD. Then the lighting/sensing controlling circuit 110 outputs the reading signal SRE representing “reading” for the image sensor 130 outputting the light-sensed signals SLS1 ̃SLSM to the distance-calculating circuit 140, and the lighting/sensing controlling circuit 110 generates the phase signal SP representing “noise” for indicating the distance-calculating circuit 140 that the received light-sensed signals are the light-sensed signals of the noise-sensing phase at the time. That is, the received light-sensed signals of the distance-calculating circuit 140 are the negative light-sensed signals SLS1− ̃SLSM−. The values of the received positive light-sensed signals SLS1− ̃SLSM− are shown in the right lower part of FIG. 2. The pulse width of shutter pulse signal SST during the distance-sensing phase is equal to the pulse width of shutter pulse signal SST during the noise-sensing phase (both are equal to TC). Therefore, the parts, which corresponds to the background light LB, of the light-sensed signals SLS1 ̃SLSM of the distance-sensing phase are equal to the parts, which corresponds to the background light LB, of the light-sensed signals SLS1 ̃SLSM of the noise-sensing phase. In other words, the parts contributed by the background light LB of the positive light-sensed signals SLS1+ ̃SLSM+ are equal to the parts contributed by the background light LB of the negative light-sensed signals SLS1− ̃SLSM− (both are equal to B1 ̃BM).
After the distance-sensing phase and the noise-sensing phase, the lighting/sensing controlling circuit 110 generates the phase signal SP representing “distance-calculating”. Meanwhile, the distance-calculating circuit 140 deducts the negative light-sensed signals SLS1− ̃SLSM− stored in the storing units from the positive light-sensed signals SLS1+ ̃SLSM+ stored in the storing units. The distance-calculating circuit 140 finds out the storing units having the maximum stored value after the deduction and accordingly determines the imaging location of the reflecting light LRD on the image sensor 130. More particularly, the values of the storing units M1 ̃MM of the distance-calculating circuit 140 are respectively equal to the values of the negative light-sensed signals SLS1− ̃SLSM− deducting from the positive light-sensed signals SLS1+ ̃SLSM+. For instance, the storing unit M1 stores the value of the negative light-sensed signal SLS1− deducting from the positive light-sensed signal SLS1+. Since the positive light-sensed signal SLS1+ and the negative light-sensed signal SLS1− are both equal to B1, the stored value of the storing unit M1 after the deduction is equal to zero. The storing unit M2 stores the value of the negative light-sensed signal SLS2− deducting from the positive light-sensed signal SLS2+. Since the positive light-sensed signal SLS2+ and the negative light-sensed signal SLS2− are both equal to B2, the stored value of the storing unit M2 after the deduction is equal to zero. Similarly, the storing unit MK stores the value of the negative light-sensed signal SLSK− deducting from the positive light-sensed signal SLSK+. Since the positive light-sensed signal SLSK+ is equal to (RK+BK) and the negative light-sensed signal SLSK− is equal to BK, the stored value of the storing unit MK after the deduction is equal to RK. The storing unit MM stores the value of the negative light-sensed signal SLSM− deducting from the positive light-sensed signal SLSM+. Since the positive light-sensed signal SLSM+ and the negative light-sensed signal SLSM− are both equal to BM, the stored value of the storing unit MM after the deduction is equal to zero. In other words, among the storing units M1 ̃MM, the stored value of the storing unit MK is equal to RK, and the stored value of the other sensing units are all equal to zero. Consequently, the distance-calculating circuit 140 determines the positive light-sensed signal stored in the storing unit MK has the energy corresponding to the reflecting light LRD. Since the storing unit MK stores the light-sensed signal generated by the sensing unit CSK, the distance-calculating circuit 140 determines the reflecting light LRD generated by the measured object MO is mainly focused on the sensing unit CSK. In this way, the distance-calculating circuit 140 calculates the imaging location DCS of the reflecting light LRD of FIG. 1 according to the sensing unit CSK and the following formula:

DCS=K×WPIX  (1);

In addition, since, in FIG. 1, the straight light LF formed between the focus point OF1 of the lens LEN1 and the sensing unit CS1 is parallel to the detecting light LID, the included angle θ1 between the detecting light LID and the reflecting light LRD is equal to the included angle θ2 between the straight line LF and the reflecting light LRD. In other words, the relation between tan θ1 and tan θ2 is represented as the following formula:

tan θ1=L/DM=tan θ2=DCS/DF  (2);

wherein L represents the predetermined distance between the lighting component 120 and the image sensor 130 (or between the detecting light LID and the reflecting light LRD); DCS represents the imaging location of the reflecting light LRD; DF represent the focus length of the lens LEN1. The measured distance DM is represented as the following formula according to the formula (2):

DM=(DF×L)/DCS  (3);

as a result, the distance-calculating circuit 140 calculates the imaging location DCS according to the formula (1), and then calculates the measured distance DM according to the predetermined distance L, the focus length DF, and the formula (3).

In conclusion, in the distance-measuring device 100, during the distance-sensing phase, the lighting/sensing controlling circuit 110 controls the lighting component 120 to emit the detecting light LID to the measured object MO. The storing units M1 ̃MM store the positive light-sensed signals SLS1+ ̃SLSM+ generated by the sensing unit CS1 ̃CSM sensing the light (for instance, the reflecting light LRD and the background light LB) focused by the lens LEN1. During the noise-sensing phase, the lighting/sensing controlling circuit 110 controls the lighting component 120 not to emit the detecting light LID to the measured object MO. The storing units M1 ̃MM store the negative light-sensed signals SLS1− ̃SLSM− generated by the sensing unit CS1 ̃CSM sensing the light (for instance, the background light LB) focused by the lens LEN1. Then the stored values of the storing units M1 ̃MM are equal to the values of the negative light-sensed signals SLS1− ̃SLSM− deducting from the positive light-sensed signals SLS1+ ̃SLSM+. Thus, the stored value of the storing unit MK, corresponding to the sensing unit CSK where the reflecting light LRD is focused, is larger than the other storing units. In this way, the distance-calculating circuit 140 determines the reflecting light LRD is focused to the sensing unit CSK, and accordingly calculates the imaging location DCS of the reflecting light LRD. Therefore, the distance-calculating circuit 140 can calculate the measured distance DM according to the imaging location DCS, the focus length DF of the lens LEN1, and the predetermined distance L.
Furthermore, in the distance-measuring device 100, the distance-sensing phase and the noise-sensing phase can repeat over and over (for example, Y times), so that the storing units M1 ̃MM store the positive light-sensed signals corresponding to the Y distance-sensing phases, and store the negative light-sensed signals corresponding to the Y noise-sensing phases. The parts of the positive light-sensed signals, which corresponds to the background light LB during each distance-sensing phase, are counteracted by the parts of the negative light-sensed signals, which corresponds to the background light LB during each noise-sensing phase. Hence, besides the value of the storing unit MK, corresponding to the sensing unit CSK where the reflecting light LRD is focused, is equal to (Y×RK), the values of the other storing units are all equal to zero. In this way, even the reflecting light LRD is so weak that the energy RK sensed by the sensing unit CSK is very small, the distance-measuring device 100 still can enlarge the difference between the value of the storing unit MK and the values of the other storing units by repeating the distance-sensing phase and the noise-sensing phase for several times (that is, Y is enlarged). In this way, in spite of the weak reflecting light LRD, the distance-calculating circuit 140 still can correctly determine the storing unit MK having the maximum value, and accordingly calculates the imaging location of the reflecting light LRD.
Please refer to FIG. 3. FIG. 3 is a diagram illustrating the operation principle of the distance-measuring device 100 reducing the flicker phenomenon. Since the power of the general indoor light sources are from the AC power supply, a part of the background light LB (which is referred as the flicking light LF hereinafter) flicks because of the frequency of the AC power supply. For example, the power of the indoor fluorescent lamp is from the AC power supply. Therefore, the light emitted by the fluorescent lamp is affected by the frequency of the AC power supply, so that the flicker phenomenon is generated. In FIG. 3, it is assumed that the cycle of the AC power supply (or the AC cycle) is TF (for example, the frequency of the AC power supply is 60 Hz, and the AC cycle is 0.0167 s). The power P of the AC power supply varies with time. Hence, the power of the flicking light LF varies as well. However, the varying cycle of the power P of the AC power supply is equal to a half of the AC cycle (that is, TF/2). For example, when the time is T, the power P of the AC power supply is equal to PT; when the time is (T+TF/2), the power P of the AC power supply is still equal to PT. Since the power of the flicking light is proportional to the power P of the AC power supply, the varying cycle of the power of the flicking light LF is equal to a half of the AC cycle (that is, TF/2) as well. In this way, in the distance-measuring device 100, the lighting/sensing controlling circuit 110 controls the time interval between the distance-sensing phases (for example, T1+ and T2+ shown in FIG. 3) and the noise-sensing phases (for example, T1− and T2− shown in FIG. 3) equal to a half of the AC cycle TF/2 for reducing the effect of the flicker phenomenon. More particularly, the lighting/sensing controlling circuit 110 controls the sensing units CS1 ̃CSM sensing the flicking light LF corresponding to the power P1 (or P2) of the AC power supply during the distance-sensing phase T1+ (or T2+), so that the parts of the positive light-sensed signals, which correspond to the flicking light LF, are equal to F11 ̃FM1 (or F12 ̃FM2). The lighting/sensing controlling circuit 110 controls the time interval between the distance-sensing phase T1+ (or T2+) and the noise-sensing phase T1− (or T2−) equal to a half of the AC cycle TF/2 (for example, 0.0083 s). As a result, the power of the flicking light LF sensed by the sensing units CS1 ̃CSM during the noise-sensing phase T1− (or T2−) is equal to the power of the flicking light LF sensed by the sensing units CS1 ̃CSM during the distance-sensing phase T1+ (or T2+). In this way, the parts, corresponding to the flicking light LF, of the negative light-sensed signals generated by the sensing units CS1 ̃CSM during the noise-sensing phase T1− (or T2−) are equal to F11 ̃FM1 (or F12 ̃FM2) as well. Consequently, the parts, corresponding to the flicking light LF, of the positive light-sensed signals of the distance-sensing phase T1+ (or T2+) are counteracted by the parts, corresponding to the flicking light LF, of the negative light-sensed of the noise-sensing phase T1− (or T2−) signals. In other words, besides the value of the storing unit MK, which corresponds to the sensing unit CSK where the reflecting light LRD is focused, is equal to RK, the values of the other storing units are all equal to zero. Hence, even the sensing units CS1 ̃CSM sense the flicking light LF, the lighting/sensing controlling circuit 110 still can reduce the effect of the flicker phenomenon by controlling the time interval between the distance-sensing phase and the noise-sensing phase equal to a half of the AC cycle (TF/2), so that the distance-calculating circuit 140 correctly determines the imaging location DCS of the reflecting light LRD and accordingly calculates the measured distance DM.
Since, when the distance-measuring device 100 is assembled during the fabrication, the locations of the components of the distance-measuring device 100 are affected by the assembling error, the distance-measuring device 100 is affected by the assembling error when the distance-measuring device 100 measures the distance. In the present invention, the parameter-calculating circuit 150 of the distance-measuring device 100 is utilized for calibrating the assembling error of the distance-measuring device 100. The operation principle of the parameter-calculating circuit 150 is illustrated as below.
The parameter-calculating circuit 150 receives the known-distance signal SD for obtaining a known distance DC1 and a known distance DC2, wherein the known distance DC1 is the distance between a calibrating object CO1 and the distance-measuring device 100, and the known distance DC2 is the distance between a calibrating object CO2 and the distance-measuring device 100. By means of the method illustrated in FIG. 2, the lighting component 120 is controlled to emit the detecting light LID to the calibrating objects CO1 and CO2, so that the parameter-calculating circuit 150 can obtain the imaging location of the reflecting light LRD according to the light-sensed signals outputted by the images sensor 130 and accordingly calibrates the assembling error of the distance-measuring device 100.
First, it is assumed that the detecting light LID emitted by the lighting component 120 rotates a lighting-error angle θLD because of the assembling error.
Please refer to FIG. 4. FIG. 4 is a diagram illustrating a calibrating method of calibrating the lighting-error angle θLD of the detecting light LID emitted by the lighting-component 120. The lighting/sensing controlling circuit 110 controls the lighting component 120 to emit the detecting light LID to the calibrating object CO1. The distance between the calibrating object CO1 and the distance-measuring device 100 is the known distance DC1. Since the detecting light LID is affected by the assembling error of the lighting component 120, the detecting light LID emits to the calibrating object CO1 with a lighting-error angle θLD, and the reflecting light LRD generated by the calibrating object CO1 reflecting the detecting light LID is focused to the sensing unit CSI. The included angle between the detecting light LID and the reflecting light LRD is θ1I. The included angle between the straight line LF and the reflecting light LRD is θ2I. As shown in FIG. 4, since the straight light LF is parallel to the surface normal of the calibrating object CO1, (θ1I−θLD) is equal to θ2I. That is, tan(θ1I−θLD) is equal to tan θ2I. Therefore, the following formulas are obtained:

DC1=1/[1/(DF×L)×DCSI+B]  (4);

B=tan θLD/L  (5);

wherein B represents the calibrating parameter for calibrating the lighting-error angle θLD; DCSI represents the imaging location of the reflecting light LRD. Thus, the parameter-calculating circuit 150 calculates the calibrating parameter B according to the formula (4). In this way, the parameter-calculating circuit 150 outputs the calibrating parameter B to the distance-calculating circuit 140 through the parameter signal SAB, so that the distance-calculating circuit 140 calibrates the formula (2) to be the following formula for calculating the calibrated measured distance DM:

DM=1/[1/(DF×L)×DCS+B]  (6);

as a result, even the detecting light LID emitted by the lighting component 120 rotates a lighting-error angle θLD because of the assembling-error, the distance-calculating circuit 140 still can correctly calculate the measured distance DM, according to the calibrating parameter B, the focus length of the lens LEN1, the predetermined distance L, and the imaging location DCS of the reflecting light LRD when the measured object MO is measured, by means of the parameter-calculating circuit 150 calculating the calibrating parameter B capable of calibrating the lighting-error angle θLD.

Please refer to FIG. 5 and FIG. 6. FIG. 5 and FIG. 6 are diagrams illustrating a calibrating method of calibrating sensing-error angles θCS1 and θCS2 rotated by the image sensor 130 because of the assembling error. FIG. 5 is a top view diagram of the distance-measuring device 100. As shown in FIG. 5, the sensing-error angle θCS1 is on the XY plane. FIG. 6 is a side view diagram of the distance-measuring device 100. In addition, the sensing-error angles θCS1 and θCS2 are both shown in FIG. 6. The lighting/sensing controlling circuit 110 controls the lighting component 120 to emit the detecting light LID to the calibrating object CO2. The distance between the calibrating object CO2 and the distance-measuring device 100 is the known distance DC2. In FIG. 5 and FIG. 6, it is assumed that the lighting component 120 is assembled correctly (that is, the lighting-error angle θLD is zero). The detecting light LID emits to the calibrating object CO2, and the reflecting light LRD generated by the calibrating object CO2 reflecting the detecting light LID is focused to the sensing unit CSJ. The included angle between the detecting light LID and the reflecting light LRD is θ1J. The included angle between the straight line LF and the reflecting light LRD is θ2J. It can be seen in FIG. 6 that DCSX is a projected distance projected by the imaging location DCSJ of the reflecting light LRD, and the relation between the imaging location DCSJ and the projected distance DCSX is represented as the following formula:

DCSX=DCSJ×cos θCS2×cos θCS1  (6).

In FIG. 5, the straight line L is parallel to the detecting light LID. Consequently, the included angle θ2J between the straight line LF and the reflecting light LRD is equal to the included angle θ1J between the detecting light LID and the reflecting light LRD. That is, tan θ1J is equal to tan θ2J. In this way, the relation between the known distance DC2 and the projected distance DCSX is represented as the following formula:

L/DC2=DCSX/DF  (7);

hence, the following formulas are obtained according to the formulas (6) and (7):

DC2=1/(A×DCSJ)  (8);

A=(cos θCS2×cos θCS1)/(DF×L)  (9);

wherein A represents the calibrating parameter for calibrating the sensing-error angles θCS2 and θCS1. Thus, the parameter-calculating circuit 150 calculates the calibrating parameter A according to the formula (8). In this way, the parameter-calculating circuit 150 outputs the calibrating parameter A to the distance-calculating circuit 140 through the parameter signal SAB, so that the distance-calculating circuit 140 calibrates the formula (2) to be the following formula for calculating the calculated measured distance DM:

DM=1/(A×DCS)  (10);

it can be seen that even the image sensor 130 rotates the sensing-error angles θCS1 and θCS2 because of the assembling error, the distance-calculating circuit 140 still can correctly calculate the measured distance DM, according to the calibrating parameter A, and the imaging location DCS of the reflecting light LRD when the measured object MO is measured, by means of the parameter-calculating circuit 150 calculating out the calibrating parameter A capable of calibrating the sensing-error angles θCS1 and θCS2.

It is assumed that the detecting light LID emitted by the lighting component 120 rotates the lighting-error angle θLD, and the image sensor 130 also rotates the sensing-error angles θCS1 and θCS2, because of the assembling error of the distance-measuring device 100. The distance-measuring device 100 can obtain the imaging location DCS1 of the reflecting light LRD corresponding to the calibrating object CO1 and the imaging location DCS2 of the reflecting light LRD corresponding to the calibrating object CO2 by the lighting component 120 emitting the detecting light LID to the calibrating objects CO1 and CO2, according to the illustration of FIG. 4, FIG. 5, and FIG. 6. The relations among the imaging locations DCS1 and DCS2, the known distance DC1 between the distance-measuring device 100 and the calibrating object CO1, the known distance DC2 between the distance-measuring device 100 and the calibrating object CO2, and the calibrating parameters A and B are represented as the following formulas:

DC1=1/[A×DCS1+B]  (11);

DC2=1/[A×DCS2+B]  (12);

the parameter-calculating circuit 150 calculates the calibrating parameter A capable of calibrating the sensing-error angles θCS1 and θCS2, and the calibrating parameter B capable of calibrating the lighting-error angles θLD, according to the formulas (11) and (12). The parameter-calculating circuit 150 outputs the calibrating parameters A and B to the distance-calculating circuit 140 through the parameter signal SAB, so that the distance-calculating circuit 140 calibrates the formula (2) to be the following formula for calculating the calculated measured distance DM:

DM=1/[A×DCS+B]  (13);

in this way, even the detecting light LID emitted by the lighting component 120 rotates the lighting-error angle θLD, and the image sensor 130 rotates the sensing-error angles θCS1 and θCS2 at the same time, the distance-calculating circuit 140 still can correctly calculate the measured distance DM by the parameter-calculating circuit 150 calculating out the calibrating parameter A, which is capable of calibrating the sensing-error angles θCS1 and θCS2, and the calibrating parameter B, which is capable of calibrating the lighting-error angle θLD.

In addition, according to the formula (13), when the distance-calculating circuit 140 calculates the measured distance DM, only the calibrating parameters A and B, and the imaging location DCS of the reflecting light LRD when the measured object MO is measured are required. The focus length DF of the lens LEN1 and predetermined distance L do not have to be known. In other words, even the focus length DF of the lens LEN1 and predetermined distance L are affected because of the assembling error during the fabrication, the distance-calculating circuit 140 still can correctly calculates the measured distance DM according to the formula (13).
Please refer to FIG. 7. FIG. 7 is a diagram illustrating the structure of an image sensor 700 according to a first embodiment of the present invention. As shown in FIG. 7, the M sensing units of the image sensor 700 are arranged in N columns and K rows. In the image sensor 700, the horizontal locations (that is, the location in the horizontal direction or in the direction of the X-axis shown in FIG. 7) of the sensing units of the same column are the same. Moreover, it is assumed that the widths of the sensing units CS11 ̃CSNK are all equal to WPIX and the horizontal location of the left side of the sensing unit CS11 is represented by zero. If the horizontal location of the sensing units of one column is represented by the center of the column, then the horizontal location of the sensing units CS11 ̃CS1K of the 1st column is represented as 1⁄2×WPIX; the horizontal location of the sensing units CS21 ̃CS2K of the 2nd column is represented as 3/2×WPIX; the horizontal location of the sensing units CSN1 ̃CSNK of the Nth column is represented as [(2×N−1)×WPIX]/2, and so on. Therefore, in the image sensor 700, the horizontal locations of the sensing units of each row can be represented as {1⁄2×WPIX, 3/2×WPIX, . . . , [(2×N−1)×WPIX]/2}, according to the above-mentioned illustration.
Please refer to FIG. 8. FIG. 8 is a diagram illustrating the operation principle of detecting the imaging location DCS of the reflecting light LRD by the image sensor 700. The circle shown in the upper part of FIG. 8 represents the imaging location DCS of the reflecting light LRD on the image sensor 700. That is, the sensing units inside the circle sense the energy of the reflecting light LRD so as to generate the light-sensed signals SLS having the larger values than the other sensing units. For obtaining the imaging location DCS of the reflecting light DCS, the light-sensed signals SLD generated by sensing units of each column are respectively summed for obtaining the accumulated light-sensed signals SALS for each column. For example, the accumulated light-sensed signal generated by summing the light-sensed signals of the sensing units CS11 ̃CS1K of the 1st column is SALS1; the accumulated light-sensed signal generated by summing the light-sensed signals of the sensing units CS21 ̃CS2K of the 2nd column is SALS2; the accumulated light-sensed signal generated by summing the light-sensed signals of the sensing units CSN1 ̃CSNK is of the Nth column SALSN, and so on. Since the sensing units sensing the reflecting light LRD generate the light-sensed signals having the larger values, the sensing units near the imaging location DCS of the reflecting light LRD (that is, inside the circle) all generate the light-sensed signals having the larger values. In other words, among the accumulated light-sensed signals SALS1 ̃SALSN, if the accumulated light-sensed signal SALSF, which corresponds to the sensing units CSF1 ̃CSFK of the Fth column, has the maximum value, it represents that the imaging location DCS of the reflecting light LRD (that is, the center of the circle) is at the Fth column. In this way, the horizontal direction of the Fth column is utilized for representing the imaging location DCS of the reflecting light LRD. For instance, as shown in FIG. 8, the accumulated light-sensed signal SALS5 corresponding to the sensing units CS51 ̃CS5K of 5th column has the maximum value. Therefore, the imaging location DCS of the reflecting light LRD (that is, the center of the circle) is determined at the 5th column. In this way, the horizontal location of the 5th column (9/2×WPIX) can represent the imaging location DCS of the reflecting light LRD.
Please refer to FIG. 9. FIG. 9 is a diagram illustrating the structure of an image sensor 900 according to another embodiment of the present invention. As shown in FIG. 9, the M sensing units of the image sensor 900 are arranged in N columns and K rows. Comparing with the image sensor 700, in the image sensor 900, the horizontal locations of each sensing unit of one row is shifted by a shifting distance DSF, which is assumed to be WPIX/2 in FIG. 9. For example, the horizontal locations of the sensing units CS11 ̃CSN1 of the 1st row can be represented as {1⁄2×WPIX, 3/2×WPIX, . . . , [(2×N+1)×WPIX]/2}; the horizontal locations of the sensing units CS12 ̃CSN2 of the 2nd row can be represented as {WPIX, 2×WPIX, . . . , [2×N×WPIX]/2}; the horizontal locations of the sensing units CS1K ̃CSNK of the Kth row can be represented as {[1⁄2+(K−1)/2]×WPIX, [3/2+(K−1)/2]×WPIX, . . . , [(2×N−1)/2+(K−1)/2]×WPIX}, and so on.
Please refer to FIG. 10. FIG. 10 is a diagram illustrating the operation principle of detecting the imaging location DCS of the reflecting light LRD by the image sensor 900. The circle shown in the upper part of FIG. 9 represents the imaging location of the reflecting light LRD on the image sensor 900. The accumulated light-sensed signals generated according to the light-sensed signals of the sensing units CS11 ̃CSNK of the image sensor 900 are SASL1 ̃SALSN. The sensing range corresponding to the accumulated light-sensed signals SALS1 is the horizontal locations 0 ̃WPIX/2. Since among the sensing units CS11 ̃CSNK, only the sensing range of the sensing unit CS11 has a part in the sensing range corresponding to the accumulated light-sensed signals SALS1, the accumulated light-sensed signal SALS1 is equal to the value of the light-sensed signal generated by the sensing unit CS11. The sensing range corresponding to the accumulated light-sensed signals SALS2 is WPIX/2 ̃WPIX. Since among the sensing units CS11 ̃CSNK, the sensing range of the sensing unit CS11 and the sensing range of the sensing unit CS21 both have a part in the sensing range corresponding to the accumulated light-sensed signals SALS2, the accumulated light-sensed signal SALS1 is obtained by summing the light-sensed signals generated by the sensing unit CS11 and CS21. The other accumulated light-sensed signals can be obtained in similar way. Among the accumulated light-sensed signals SALS1 ̃SALS2N, if the accumulated light-sensed signal SALSF has the maximum value, it represents that the imaging location of the reflecting light LRD (that is, the center of the circle) is at the sensing units CSF1 ̃CSFK of the Fth column. For instance, as shown in FIG. 10, the accumulated light-sensed signal SALS10 has the maximum value. Thus, the imaging location of the reflecting light LRD (that is, the center of the circle) is determined to be at the horizontal location of the accumulated light-sensed signal SALS10. Since the sensing range corresponding to the accumulated light-sensed signal SALS10 is 9/2×WPIX ̃5×WPIX. Consequently, the horizontal location of the accumulated light-sensed signal SALS10 is represented as 19/4×WPIX. In this way, the horizontal location 19/4×WPIX represents the imaging location DCS of the reflecting light LRD.
Comparing with the image sensor 700, the image sensor 900 has a higher resolution. For example, when the image location DCS of the reflecting light LRD is detected by the image sensor 700, if the horizontal location of the image location DCS of the reflecting light LRD (the center of the circle) is actually (17/4)×WPIX, the accumulated light-sensed signal SALS5 has the maximum value. Therefore, the image location DCS of the reflecting light LRD is represented by the horizontal location 9/2×WPIX of the 5th column. However, if the horizontal location of the image location DCS of the reflecting light LRD (the center of the circle) changes to (19/4)×WPIX, the accumulated light-sensed signal SALS5 still has the maximum value. That is, although the actual horizontal location of the imaging location DCS of the reflecting light LRD has already changed from (17/4)×WPIX to (19/4)×WPIX, the imaging location DCS of the reflecting light LRD is still represented as 9/2×WPIX (the horizontal location of the 5th column) by means of the image sensor 700. However, when the image location DCS of the reflecting light LRD is detected by the image sensor 900, if the horizontal location of the image location DCS of the reflecting light LRD (the center of the circle) is actually (17/4)×WPIX, the accumulated light-sensed signal SALS9 has the maximum value. Therefore, the image location DCS of the reflecting light LRD is represented by the horizontal location 17/4×WPIX of the 9th column. If the horizontal location of the image location DCS of the reflecting light LRD (the center of the circle) changes to (19/4)×WPIX, the accumulated light-sensed signal SALS10 has the maximum value. As a result, the image location DCS of the reflecting light LRD is represented by the horizontal location 19/4×WPIX of the 10th column. Consequently, the imaging location DCS of the reflecting light LRD are more accurately detected by the image sensor 900. In conclusion, by shifting the horizontal locations of each sensing unit of the same column, the image sensor 900 has the higher resolution than the image sensor 700.
However, in the image sensor 900, the shifting distances between the adjacent rows of the sensing units do not have to be the same. For example, the shifting distance between the 1st and the 2nd rows of the sensing units is WPIX/2; the shifting distance between the 2nd and the 3rd rows of the sensing units is WPIX/4. By such organization, the imaging location DCS of the reflecting light LRD still can be detected by the method illustrated in FIG. 10.
Please refer to FIG. 11. FIG. 11 is a diagram illustrating the structure of an image sensor 1100 according to another embodiment of the present invention. As shown in FIG. 11, the M sensing units of the image sensor 1100 are arranged in N columns and Q rows. Comparing the image sensor 1100 with the image sensor 700, it can be understood that each sensing unit in the image sensor 700 is a square. However, each sensing unit in the image sensor 1100 is a rectangle. For instance, both the width and the height of each sensing unit of image sensor 700 are equal to WPIX, but, the width of each sensing unit of image sensor 1100 is WPIX and the height of each sensing unit of image sensor 1100 is (WPIX×K/Q), wherein Q<K. That is, the long side of each sensing unit of image sensor 1100 is in the vertical direction, and the short side of each sensing unit of image sensor 1100 is in the horizontal direction (the X-axis direction). In other words, each sensing unit of image sensor 1100 has the same width as the each sensing unit of image sensor 700. Although the number Q is smaller than the number K, the total area of the sensing units of one column of the image sensor 1100 is still equal to the total area of the sensing units of one column of the image sensor 700. Similar to the image sensor 700, the image sensor 1100 also provides M light-sensed signals generated by the M sensing units to the distance-calculating circuit 140, so that the distance-calculating circuit 140 calculates the accumulated light-sensed signals SALS1 ̃SALSN. For example, the accumulated light-sensed signal generated by summing the light-sensed signals of the sensing units CS11 ̃CS1Q of the 1st column is SALS1; the accumulated light-sensed signal generated by summing the light-sensed signals of the sensing units CS21 ̃CS2Q of the 2nd column is SALS2; the accumulated light-sensed signal generated by summing the light-sensed signals of the sensing units CSN1 ̃CSNQ of the Nth column is SALSN, and so on. In this way, the distance-calculating circuit 140 obtains the imaging location DCS of the reflecting light LRD according to the accumulated light-sensed signals SALS1 ̃SALSN by the method illustrated in FIG. 8, and accordingly calculates the measured distance DM.
Comparing with the image sensor 700, it can be seen that in the image sensor 1100, the side of each sensing unit in the vertical direction is longer, so that the number of sensing units of one column is reduced (that is Q<K). Therefore, the number of the accumulating times which the distance-calculating circuit 140 generates the accumulated light-sensed signals SALS1 ̃SALSN, is reduced as well. Since the total area of the sensing units of one column of the image sensor 1100 is the same as the total area of the sensing units of one column of the image sensor 700, the received energy of the sensing units of each column sensing the light focused by the lens LEN1 remains unchanged. In other words, when the imaging location DCS of the reflecting light LRD is measured by means of the image sensor 1100, the computation of the distance-calculating circuit 140 generating the accumulated light-sensed signals SALS1 ̃SALSN is reduced, and the noise-to-signal ratios of the accumulated light-sensed signals SALS1 ̃SALSN are maintained at the same time. In addition, the short side of the sensing units of each column of the image sensor 1100 is in the horizontal direction and the width of each column sensing units is WPIX. In other words, when the imaging location DCS of the reflecting light LRD is measured, the image sensor 1100 has the same resolution as the image sensor 700. Thus, comparing with the image sensor 700, it can be seen that the image sensor 1100 reduces the computation of the distance-calculating circuit 140 generating the accumulated light-sensed signals SALS1 ̃SALSN and maintains the resolution of the imaging location DCS in the horizontal direction (that is, the direction of the short side) and the signal-to-noise ratios of the accumulated light-sensed signals as well.
In conclusion, the distance-measuring device provided by the present invention reduces the effect of the background light and the flicker phenomenon by means of removing the parts corresponding to the background light and the flicking light from the light-sensed signals generated by the image sensor. In the image sensor of the present invention, the resolution is improved by shifting the sensing units of adjacent rows. In addition, the present invention further provides a calibrating method of the distance-measuring device. The first imaging location corresponding to the first calibrating object and the second imaging location corresponding to the second calibrating object are respectively obtained by means of the lighting component emits the detecting light to the first calibrating object with the first known distance and to the second calibrating object with the second known distance. The calibrating parameters capable of calibrating the assembling error of the distance-measuring device are calculated out according to the first and the second imaging location, and the first and the second known distance. In this way, the distance-measuring device correctly calculates the measured distance by means of the calibrating parameters, providing a great convenience.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.

## Claims

1. A calibrating method for calibrating a distance-measuring device of measuring distance according to variation of imaging location, a lighting component of the distance-measuring device emitting a detecting light to a measured object, the measured object reflecting the detecting light to an image sensor of the distance-measuring device for imaging at a first imaging location, the distance-measuring device calculating a measured distance between the measured object and the distance-measuring device according to the first imaging location, a focus length of a first lens of the distance-measuring device, and a predetermined distance between the lighting component and the image sensor, the calibrating method comprising:
the lighting component of the distance-measuring device emitting the detecting light to a calibrating object, and the calibrating object reflecting the detecting light to the image sensor of the distance-measuring device for imaging at a second imaging location;
wherein a distance between the distance-measuring device and the calibrating object is a known distance;

calculating a calibrating parameter for calibrating an assembling-error angle according to the known distance and the second imaging location; and
the distance-measuring device calculating the calculated measured distance according to the calibrating parameter.

2. The calibrating method of claim 1, wherein calculating the calibrating parameter for calibrating the assembling-error angle according to the known distance, the second imaging location comprises:
calculating the calibrating parameter for calibrating a lighting-error angle rotated by the detecting light of the lighting-component of the distance-measuring device according to the known distance and the second imaging location.

3. The calibrating method of claim 2, wherein the calibrating parameter, which is utilized for calibrating the lighting-error angle rotated by the detecting light of the lighting-component of the distance-measuring device according to the known distance and the second imaging location, is calculated according to a following formula:


DC1=1/[1/(DF×L)×DCSI+B]; 

wherein DC1 represents the known distance; DCSI represents the second imaging location; B represents the calibrating parameter; DF represent the focus length of the first lens; L represent the predetermined distance between the lighting component and the image sensor.

4. The calibrating method of claim 2, wherein relation between the calibrating parameter and the lighting-error angle is represented as a following formula:


B=tan θLD/L; 

Wherein θLD represents the lighting-error angle.

5. The calibrating method of claim 3, wherein when the measured distance is calculated according to a following formula:


DM=1/[1/(DF×L)×DCS+B]

wherein DM represents the measured distance; DCS represents the first imaging location of the reflecting light when the measured object is measured.

6. The calibrating method of claim 1, wherein calculating the calibrating parameter for calibrating the assembling-error angle according to the known distance, the second imaging location comprises:
calculating the calibrating parameter for calibrating a first sensing-error angle and a second sensing-error angle of the image sensor of the distance-measuring device according to the known distance and the second imaging location.

7. The calibrating method of claim 6, wherein the calibrating parameter, which is utilized for calibrating the first sensing-error angle and the second sensing-error angle of the image sensor of the distance-measuring device according to the known distance and the second imaging location, is calculated according to a following formula:


DC2=1/(A×DCSJ);

wherein DC2 represents the known distance; DCSJ represents the second imaging location; A represents the calibrating parameter.

8. The calibrating method of claim 7, wherein relation among the calibrating parameter, the first sensing-error angle, and the second sensing-error angle is represented as a following formula:


A=(cos θCS2×cos θCS1)/(DF×L);

wherein θCS1 represents the first sensing-error angle; θCS2 represents the second sensing-error angle; DF represent the focus length of the first lens; L represent the predetermined distance between the lighting component and the image sensor.

9. The calibrating method of claim 7, wherein the measured distance is calculated according to a following formula:


DM=1/(A×DCS);

wherein DM represents the measured distance; DCS represents the first imaging location of the reflecting light when the measured object is measured.