CN101140184B - Method and device for automatically measuring ambient brightness - Google Patents

Abstract

The invention discloses a method and a device for automatically measuring environment brightness, which is used to provide a technical scheme which is simple, has the low cost and determines the environment brightness. The method provided in the invention presets the first corresponding relations of exposure time range and environment brightness grade, and the method is that the environment brightness grade is determined according to the exposure time range to which the exposure time belongs and the corresponding relations.

Description

A kind of method of automatic measuring ambient brightness and device

Technical field

The present invention relates to the signal processing technology field, relate in particular to a kind of method and device of automatic measuring ambient brightness.

Background technology

Development along with infotech; camera is popularized in a lot of multimedia equipments; these equipment often are operated in the different environment; the monochrome information that obtains surrounding environment according to camera information is very useful sometimes; such as changing according to ambient brightness; change the display brightness of display device (for example the display terminal of notebook, desktop computer and mobile phone etc.), thereby when saving electric energy, protected people's eyesight again.In addition, some special dimension also needs ambient brightness, need measure the sudden change of ambient brightness such as some automatic door bell or warning device.

In the prior art, generally by special photometry sensor (as illuminometer etc.) measurement environment luminance brightness.The precision height that this method is measured, but need separate equipment, use inconvenient in a lot of occasions.

In the prior art, can also adopt photoresistance to measure ambient brightness, still, adopt photoresistance to measure the technical scheme of ambient brightness, owing to need to increase one or more photoresistance, thereby increased cost, also increased the complexity of device simultaneously.

Camera is popularized in a lot of Multimedia Mobile equipment, the information during according to the camera pictures taken, and the estimation ambient brightness is a good selection.In the prior art, method by camera estimation ambient brightness just according to the time shutter simply with ambient brightness rough be divided into several grades, do not consider the influence of image capture device to brightness of image, and, also too simple to the classification of ambient brightness.

Summary of the invention

The embodiment of the invention provides a kind of method and device of automatic measuring ambient brightness, in order to a kind of technical scheme that realizes definite ambient brightness that simple, required cost is low to be provided.

The method that the embodiment of the invention provides sets in advance other first corresponding relation of time shutter scope and ambient light level, and this method comprises:

According to the time shutter scope under the time shutter, and described first corresponding relation, determine the ambient brightness rank.

The device that the embodiment of the invention provides comprises:

The unit is set, is used to store time shutter scope and other first corresponding relation of ambient light level of setting in advance;

Determining unit is used for according to the time shutter scope under the time shutter, and described first corresponding relation, determines the ambient brightness rank.

The embodiment of the invention sets in advance other first corresponding relation of time shutter scope and ambient light level, according to the time shutter scope under the time shutter, and described first corresponding relation, determine the ambient brightness rank.Make that other realization of mensuration ambient light level is simpler, cost is lower.

Description of drawings

The method flow synoptic diagram that Fig. 1 provides for the embodiment of the invention;

The method flow synoptic diagram that Fig. 2 provides for the embodiment of the invention;

The apparatus structure synoptic diagram that Fig. 3 provides for the embodiment of the invention;

The first determining unit structural representation that Fig. 4 provides for the embodiment of the invention.

Embodiment

The embodiment of the invention provides a kind of method and device of automatic measuring ambient brightness, makes that the realization of determining ambient brightness is simpler, and required cost is lower.

The imaging device of mentioning in the embodiment of the invention, all support the imaging device of automatic exposure modes to comprise camera, digital camera, video camera and other.The embodiment of the invention need not to increase additional hardware just can measure ambient brightness according to the exposure parameter of imaging device.

Generally speaking, imaging device all can show the human eye acceptable image for the brightness that conforms under various environmental baseline, all can comprise an automatic exposure module.This module can be according to the difference of ambient brightness, adjusts the time shutter (ET_Step) of sensor devices, thereby all accepts the image of scope at human eye can obtaining brightness of image and contrast under the darker environmental baseline and under the brighter environmental baseline.

General automatic exposure algorithm all can set in advance the brightness range of final output image, according to the brightness of current images acquired, judges this brightness of image whether in final brightness range, if, then do not handle; If do not exist, then regulate ET_Step, when the figure kine bias of gathering is bright, just reduce ET_Step, when the figure kine bias of gathering is dark, then improve ET_Step.Like this, the mean flow rate of image can be stabilized in certain scope, but the value of time shutter is but changing, and this variation has reflected the variation of ambient brightness.Under common indoor illumination condition, time shutter and the ambient brightness relation of being inversely proportional to, promptly when environment was brighter, ET_Step was less; And when environment was dark, ET_Step was bigger.

Generally speaking, ambient brightness is when 30Lux is in the 500lLux scope, and corresponding ET_Step can be transferred to the 1st grade (corresponding time shutter scope is about 0.2 second to 0.01 second) from the 20th grade, and the two all is similar to and is inverse relation.

In actual applications, do not need the fine description of ambient brightness, but the rough rank that only needs to know ambient brightness gets final product, thereby the embodiment of the invention can be measured the rank of ambient brightness according to the scope of ET_Step.

Below in conjunction with accompanying drawing, describing the embodiment of the invention in detail is how to realize automatic measuring ambient brightness.

Referring to Fig. 1, the method that the embodiment of the invention provides comprises:

S101, set in advance time shutter scope and other corresponding relation of ambient light level.

For example, ambient brightness need be divided into the N level, and the brightness at different levels scope of corresponding ET_Step respectively are [TET₁ⁿ, TET₂ⁿ), TET wherein₁ⁿBe the minimum value of scope of the ET_Step of n level ambient brightness correspondence, TET₂ⁿBe the maximal value of scope of the ET_Step of n level ambient brightness correspondence, and satisfy${\mathrm{TET}}_2^n={\mathrm{TET}}_1^{n+1},$It is the maximal value of the scope of the minimum value of scope of the ET_Step of other ambient brightness correspondence of a certain level ET_Step that equals other ambient brightness correspondence of its upper level.

S102, search the time shutter scope under the current ET_Step.

S103, according to the time shutter scope, determine corresponding ambient brightness rank.

If current ET_Step has dropped on ambient light levels when being n in the pairing time shutter scope, determine that then current environment brightness is the n level.

For example, suppose and need be divided into 5 grades to ambient brightness, can followingly set:

The 1st grade of ambient brightness: TET₁¹Equal the time shutter of the 1st grade of ET_Step correspondence, TET₂¹Equal the time shutter of 3rd level ET_Step correspondence;

The 2nd grade of ambient brightness: TET₁²Equal the time shutter of 3rd level ET_Step correspondence, TET₂²Equal the time shutter of the 7th grade of ET_Step correspondence;

Ambient brightness 3rd level: TET₁³Equal the time shutter of the 7th grade of ET_Step correspondence, TET₂³Equal the time shutter of the 13rd grade of ET_Step correspondence;

The 4th grade of ambient brightness: TET₁⁴Equal the time shutter of the 13rd grade of ET_Step correspondence, TET₂⁴Equal the time shutter of the 19th grade of ET_Step correspondence;

The 5th grade of ambient brightness: TET₁⁵Equal the time shutter of the 19th grade of ET_Step correspondence, TET₂⁵Equal the time shutter of the 20th grade of ET_Step correspondence.

Like this, each constantly all can obtain an ambient light levels, and in application, surround lighting is in the continuous variation, and the brightness degree that above-mentioned steps obtains also can constantly change, and can't stablize.And, when changing, ambient brightness enters the automatic exposure adjustment process, before automatic exposure does not settle out, ET_Step also is in continuous variation, at this moment, the brightness of output image is not in limited range, and ET_Step can't normally reflect the variation of ambient brightness.Therefore, for fear of above-mentioned situation, before judging the ambient brightness rank, step below carrying out.

The average of ET_Step in S104, the computation of Period a period of time TWith variance δ_ET

S105, work as δ_ETLess than pre-set threshold T_{σ ET}, determine that then automatic exposure this moment is stable.Can think that also the time shutter is constant, then automatic exposure is in steady state (SS), need not to judge according to the time shutter variance.It is constant promptly to work as time shutter ET_Step, perhaps the variance δ of ET_Step in the time T_ETLess than threshold value T_{σ ET}The time, determine that automatic exposure is stable, carry out ambient brightness rank determination step then.

If

In the pairing time shutter scope, determine that then current environment brightness is the n level when having dropped on ambient light levels and being n.

Even after handling like this,, may appear at the situation of frequently beating between certain two brightness degree, in order to overcome this problem, need to adopt the embodiment of dual threshold, step below promptly carrying out if ambient brightness is in the variation.

S106, according to the time shutter scope of the ambient brightness rank correspondence of determining last time, obtain the first threshold and second threshold value of time shutter.

S107, judgement

Whether more than or equal to described first threshold, and, less than described second threshold value, if, execution in step S108 then; Otherwise, execution in step S109.

S108, determine that current ambient brightness rank is the ambient brightness rank of determining last time.

S109, basis

Affiliated time shutter scope, and described corresponding relation are determined corresponding ambient brightness rank.

Suppose that the ambient brightness rank of measuring last time is n_p, pairing time shutter scope is [TET₁ⁿ, TET₂ⁿ), if then

Drop on [TET₁ⁿ-γ₁, TET₂ⁿ+ γ₂) in the scope, think that ambient light levels still is n_pOtherwise, judge

Whether dropped in the time shutter scope of certain ambient light levels correspondence, to determine the current environment brightness degree.Wherein, γ₁, γ₂Be the preset threshold protection domain, the brightness degree that causes when being used to prevent the ambient brightness variation is beated.

Yet the ET_Step range of adjustment is limited, when ET_Step arrives the adjustable extent end points, can't continue to regulate ET_Step, makes output image brightness in target zone, and ET_Step just can't accurately reflect the variation range of ambient brightness.At this moment, generally can be then adjusting brightness of image entire gain (Global_Gain) and/or sensor devices gain (Sensor_Gain).

Referring to Fig. 2, the method that another embodiment of the present invention provides comprises:

S201, set in advance time shutter scope and other first corresponding relation of ambient light level, and the gain of brightness of image (Gain) scope and other second corresponding relation of ambient light level.

For example, the ambient brightness rank of Gain scope correspondence is the M level, and the ambient brightnesss at different levels scope of corresponding Gain respectively are [TGT₁^m, TGT₂^m).

And, Gain=Global_Gain, or Gain=Sensor_Gain, or Gain=Global_Gain*Sensor_Gain.

S202, when ET_Step exceeds time shutter of setting in advance during scope, search the gain margin under the current Gain.

S203, according to the gain margin under the Gain, and described second corresponding relation is determined the ambient brightness rank.

Introduce the device that the embodiment of the invention provides below.

Referring to Fig. 3, the device that the embodiment of the invention provides comprises: first is provided withunit 31, second is provided withunit 32, judges automaticexposure stabilization element 33, first determiningunit 34,trigger element 35 and second determiningunit 36.

First is provided withunit 31, is used to store time shutter scope and other first corresponding relation of ambient light level of setting in advance.

Second is provided withunit 32, is used to store gain margin and other second corresponding relation of ambient light level of the brightness of image that sets in advance.

Judge automaticexposure stabilization element 33, be used for the variance of time shutter in computation of Period a period of time; When described variance during, determine that automatic exposure this moment is stable, and trigger described first determiningunit 34 less than pre-set threshold.

Described first determiningunit 34, when being used to receive the triggering of described judgement automaticexposure stabilization element 33, according to the time shutter scope under the time shutter, and described first corresponding relation, determine the ambient brightness rank.

Described first determiningunit 34 can be according to the time shutter scope under the current time shutter, and described first corresponding relation, determines the ambient brightness rank; Can also be according to the time shutter scope under the average of time shutter in described a period of time, and described first corresponding relation, determine the ambient brightness rank.

In addition, for fear of the problem appearance of the frequent shake of ambient brightness, referring to Fig. 4, preferably, described first determiningunit 34 comprises:dual threshold unit 341, judgingunit 342,first module 343 andsecond unit 344.

Describeddual threshold unit 341 when being used to receive the triggering of described judgement automaticexposure stabilization element 33, according to the time shutter scope of the ambient brightness rank correspondence of determining last time, obtains the first threshold and second threshold value of time shutter.

Whether described judgingunit 342, the average that is used to judge the time shutter in described a period of time more than or equal to described first threshold, and, less than described second threshold value, if then trigger describedfirst module 343; Otherwise, trigger describedsecond unit 344.

Describedfirst module 343 is used for the triggering 342 according to described judging unit, determines that current ambient brightness rank is the ambient brightness rank of determining last time.

Describedsecond unit 344 is used for the triggering 342 according to described judging unit, according to the time shutter scope under the average of time shutter in described a period of time, and described first corresponding relation, determine corresponding ambient brightness rank.

Describedtrigger element 35 is used for exceeding the described time shutter that sets in advance during scope when the described time shutter, triggers described second determiningunit 36;

Described second determiningunit 36, when being used to receive the triggering of describedtrigger element 35, according to the gain margin under the gain of brightness of image, and described second corresponding relation, determine the ambient brightness rank.

The gain of described brightness of image is: the product of brightness of image entire gain, sensor devices gain or brightness of image entire gain and sensor devices gain.

In sum, the embodiment of the invention is for all imaging devices, need not to increase additional hardware and just can measure ambient brightness, utilize the increase cost of measurement environment brightness schemes such as photoresistance and the shortcoming of equipment complexity thereby overcome prior art according to the exposure parameter of imaging device.Further, for device, can also realize the brightness of control display device according to the ambient brightness that records with display device.

Obviously, those skilled in the art can carry out various changes and modification to the present invention and not break away from the spirit and scope of the present invention.Like this, if of the present invention these are revised and modification belongs within the scope of claim of the present invention and equivalent technologies thereof, then the present invention also is intended to comprise these changes and modification interior.

Claims (12)

1. the method for an automatic measuring ambient brightness is characterized in that, this method comprises:

The variance of time shutter in computation of Period a period of time;

When described variance during, determine that automatic exposure is stable less than pre-set threshold;

When definite automatic exposure is stablized, according to the time shutter scope that sets in advance under the time shutter, and the time shutter scope that sets in advance and other first corresponding relation of ambient light level, determine the ambient brightness rank.

2. method according to claim 1 is characterized in that, the described time shutter is the current time shutter.

3. method according to claim 1 is characterized in that, when definite automatic exposure was stablized, the described time shutter was the average of time shutter in described a period of time.

4. method according to claim 1 is characterized in that, when definite automatic exposure was stablized, described other step of definite ambient light level comprised:

According to the time shutter scope of the ambient brightness rank correspondence of determining last time, obtain the first threshold and second threshold value of time shutter;

Whether the average of judging the time shutter in described a period of time more than or equal to described first threshold, and, less than described second threshold value, if determine that then current ambient brightness rank is the ambient brightness rank of determining last time; Otherwise, according to the time shutter scope under the average of time shutter in described a period of time, and described first corresponding relation, determine corresponding ambient brightness rank.

5. method according to claim 1 is characterized in that, this method also comprises the gain margin that sets in advance brightness of image and the step of other second corresponding relation of ambient light level;

Exceed the described time shutter that sets in advance during scope when the described time shutter, according to the gain margin that sets in advance brightness of image under the gain of brightness of image, and described second corresponding relation, determine the ambient brightness rank.

6. method according to claim 5 is characterized in that, the gain of described brightness of image is:

The product of brightness of image entire gain, sensor devices gain or brightness of image entire gain and sensor devices gain.

7. the device of an automatic measuring ambient brightness is characterized in that, this device comprises:

First is provided with the unit, is used to store time shutter scope and other first corresponding relation of ambient light level of setting in advance;

Judge the automatic exposure stabilization element, be used for the variance of the time shutter in computation of Period a period of time; When described variance during less than pre-set threshold, determine that automatic exposure is stable, trigger first determining unit this moment;

First determining unit is used for according to the time shutter scope that sets in advance under the time shutter, and described first corresponding relation, determines the ambient brightness rank.

8. device according to claim 7 is characterized in that, described first determining unit, and according to the time shutter scope under the current time shutter, and described first corresponding relation, determine the ambient brightness rank.

9. device according to claim 7 is characterized in that, described first determining unit, and according to the time shutter scope under the average of time shutter in described a period of time, and described first corresponding relation, determine the ambient brightness rank.

10. device according to claim 7 is characterized in that, described first determining unit comprises: dual threshold unit, judging unit, first module and Unit second;

Described dual threshold unit is used for the time shutter scope according to definite ambient brightness rank correspondence last time, obtains the first threshold and second threshold value of time shutter;

Whether described judging unit, the average that is used to judge the time shutter in described a period of time more than or equal to described first threshold, and, less than described second threshold value, if then trigger described first module; Otherwise, trigger described Unit second;

Described first module is used for the triggering according to described judging unit, determines that current ambient brightness rank is the ambient brightness rank of determining last time;

Described Unit second is used for the triggering according to described judging unit, according to the time shutter scope under the average of time shutter in described a period of time, and described first corresponding relation, determine corresponding ambient brightness rank.

11. device according to claim 7 is characterized in that, this device also comprises: second is provided with unit, trigger element and second determining unit;

Described second is provided with the unit, is used to store gain margin and other second corresponding relation of ambient light level of the brightness of image that sets in advance;

Described trigger element is used for exceeding the described time shutter that sets in advance during scope when the described time shutter, triggers described second determining unit;

Described second determining unit, when being used to receive the triggering of described trigger element, according to the gain margin that sets in advance brightness of image under the gain of brightness of image, and described second corresponding relation, determine the ambient brightness rank.

12. device according to claim 11 is characterized in that, the gain of described brightness of image is:

The product of brightness of image entire gain, sensor devices gain or brightness of image entire gain and sensor devices gain.

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