Photoelectric sensor, range image producing apparatus and method for producing range data

Abstract

A method for producing a range data includes: irradiating a pulse light toward an object during a first time period; receiving a reflected pulse light during the first time period and a second time period; calculating a ratio between a first or second received light amount and a total received light amount, wherein the first received light amount is a light amount received during the first time period, wherein the second received light amount is a light amount received during the second time period, and wherein the total received light amount is a sum of the first and second received light amounts; and producing the range data based on the ratio.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings:

FIG. 1 is a block diagram showing a range image producing apparatus;

FIG. 2 is a block diagram showing an imaging unit in the apparatus;

FIG. 3 is a circuit diagram showing a unit sensor in the apparatus;

FIG. 4 is a flow chart showing a measurement process;

FIG. 5 is a flow chart showing a range image producing process;

FIG. 6 is a timing chart showing operation of a control signal processing unit;

FIGS. 7A and 7B are graphs explaining error caused by waveform distortion of a pulse light;

FIG. 8 is a schematic view explaining an operation of the range image producing apparatus for a monitoring camera;

FIG. 9 is a schematic view explaining an operation of the range image producing apparatus for an in-vehicle camera;

FIG. 10 is a circuit diagram showing another unit sensor; and

FIG. 11 is a timing chart showing an operation of a range image producing apparatus according to a prior art.

Claims

1. A method for producing a range data comprising: irradiating a pulse light toward an object during a first time period, which is a time for the pulse light to travel back and forth to a predetermined maximum measurement distance;receiving a reflected pulse light reflected by the object during the first time period and a second time period, wherein the second time period starts at an end of the first time period, and wherein the second time period is equal to or longer than the first time period;calculating a ratio between a first received light amount and a total received light amount or a ratio between a second received light amount and the total received light amount, wherein the first received light amount is a light amount of the reflected pulse light received during the first time period, wherein the second received light amount is a light amount of the reflected pulse light received during the second time period, and wherein the total received light amount is a sum of the first received light amount and the second received light amount; andproducing the range data based on the ratio between the first received light amount and the total received light amount or the ratio between the second received light amount and the total received light amount, wherein the range data represents a distance to the object.

2. A range image producing apparatus comprising: a light emitting element for irradiating a pulse light toward a predetermined measurement range;an imaging device including a plurality of unit sensors, which are arranged in a two-dimensional plane, wherein each unit sensor includes a charge storage type photo electric conversion element for receiving a reflected pulse light reflected by an object and for converting the reflected pulse light to an electric charge, a first storage element for accumulating an output of the photo electric conversion element as a first pixel data and a second storage element for accumulating the output of the photo electric conversion element as a second pixel data;a controller, wherein the controller initializes the first and second storage elements to be a predetermined initial voltage, respectively, wherein the controller controls the light emitting element in such a manner that the light emitting element irradiates the pulse light during a first time period, which is a time for the pulse light to travel back and forth to a predetermined maximum measurement distance, wherein the controller controls the first storage element in such a manner that the first storage element accumulates the output of the photo electric conversion element during the first time period, and wherein the controller controls the second storage element in such a manner that the second storage element accumulates the output of the photo electric conversion element during a second time period, which starts at an end of the first time period and is equal to or longer than the first time period; anda range data producing element for producing a range data, which represents a distance between the object and the apparatus, wherein the range data is produced based on a ratio between the first pixel data and a total pixel data or a ratio between the second pixel data and the total pixel data, wherein the total pixel data is a sum of the first pixel data and the second pixel data, whereinthe range data producing element produces a range image having a pixel data of the range data.

3. The apparatus according to claim 2, wherein the range data producing element produces the range image in such a manner that the range image is obtained by multiplying the ratio between the first pixel data and the total pixel data or the ratio between the second pixel data and the total pixel data by the maximum measurement distance.

4. The apparatus according to claim 2, wherein the range data producing element compensates the first pixel data, the second pixel data, the ratio between the first pixel data and the total pixel data, the ratio between the second pixel data and the total pixel data, or the range data,compensation of the range data producing element is performed in such a manner that an error of waveform distortion of the pulse light is compensated based on waveform information of the pulse light,the waveform distortion is occurred at a rising edge or at a decaying edge of the pulse light, andthe waveform information is obtained in such a manner that the pulse light is preliminarily measured by the photo electric conversion element.

5. The apparatus according to claim 2, wherein the controller controls the first storage element in such a manner that the first storage element accumulates the output of the photo electric conversion element during a first compensation time period, the output having a polarity opposite to that during the first time period so that the first storage element accumulates a background output corresponding to a background light,the controller controls the second storage element in such a manner that the second storage element accumulates the output of the photo electric conversion element during a second compensation time period, the output having a polarity opposite to that during the second time period so that the second storage element accumulates the background output,the first compensation time period has time amount equal to that of the first time period, and the first compensation time period is disposed outside of the first and second time periods, andthe second compensation time period has time amount equal to that of the second time period, and the second compensation time period is disposed outside of the first and second time periods.

6. The apparatus according to claim 2, wherein the first time period of one of the unit sensors is different from that of another one of the unit sensors, andthe second time period of one of the unit sensors is different from that of another one of the unit sensors.

7. The apparatus according to claim 2, wherein the imaging device further includes a plurality of sensor groups, each of which includes predetermined unit sensors,the first time period of each unit sensor in one of sensor groups is different from that in another one of sensor groups, andthe second time period of each unit sensor in the one of sensor groups is different from that in the another one of sensor groups.

8. A photoelectric sensor comprising: a plurality of unit sensors, which are arranged in a two-dimensional plane, whereineach unit sensor includes: a charge storage type photo electric conversion element for receiving a light and for converting the light to an electric charge;a first storage element for accumulating an output of the photo electric conversion element;a second storage element for accumulating the output of the photo electric conversion element;a current path for flowing the output of the photo electric conversion element;a connector for connecting the current path and the first or second storage element; anda charging/discharging switch for switching a flowing direction of a current in the current path to the photo electric conversion element.

9. The sensor according to claim 8, wherein the photo electric conversion element is a photo diode having a PIN construction.