CN101216302B - Ranging device - Google Patents

Abstract

The present invention provides a high-versatility, cheap and high-precision distance measuring device. The distance measuring device comprises the following components: a light position measuring unit which outputs a pair of photocurrent signals corresponding with the incidence position when the incidence is projected to the reflected signal light and the background light of the light of the shotobject; an integrating circuit which does integration to the photocurrent signal outputted by the light position detecting unit; an arithmetic unit which calculates the ratio between the integral quantity that the integrating circuit does integration to a pair of the photocurrent signals and the integral quantity that the integrating circuit does integration to one side in the pair of photocurrent signal; and when the integration result of the summation of the pair of photocurrent signal is larger than the assigned amount the arithmetic unit calculates the ratio.

Description

Distance measuring equipment

The present patent application be based on February 16th, 2004 to State Intellectual Property Office propose, number of patent application is 200410005050.5, denomination of invention is dividing an application that the patented claim of " distance measuring equipment " is made.

Technical field

The present invention relates to distance measuring equipment, relate to the distance measuring equipment of active mode in more detail.

Background technology

The distance measuring method of common distance measuring equipment, " passive mode " and " active mode " arranged, so-called " passive mode " is meant, with the picture signal that detects object as a pair of image detection device of two eyes of people, find range based on this detected picture signal, and so-called " active mode " is meant, by light activated element receive when flashlights such as infrared ray are projected object, from the reflected signal light of object, calculate the distance of object according to the incoming position of reflected signal light intensity that receives and light.

Wherein, in the passive mode, carrying out correct range finding if object does not have contrast is the comparison difficulty.And owing to need the special-purpose semiconductor transducer of range finding, it is very high that the cost of distance measuring equipment becomes.

And the situation of active mode, even be the special-purpose common parts of non-range finding, also can component devices and passive mode compare, can carry out low cost manufacturing.So the applicant in Patent Document 1, to using the distance measuring equipment of active mode, has proposed the cheaper scheme of cost.The range-measuring circuit of Here it is in the chip of microcomputer computer etc. built-in active mode.

Patent Document 1: TOHKEMY 2000-352512 communique

But, the speed of technical progresses such as microcomputer computer, faster than the technical progress speed of analog circuit component far away, therefore, advanced the integrated of range-measuring circuit even on handling, painstakingly work hard, become the product that has fallen behind the times but the magnetic core that is used for microcomputer and RAM, ROM etc. are very fast.For this reason, if when the various functional utilizations of the microcomputer computer that proposed in the Patent Document 1 are in most products, the situation of versatility difference is just arranged.

Summary of the invention

The present invention In view of the foregoing makes just, and its purpose is to provide high-precision distance measuring equipment, with the specification of microcomputer computer is irrelevant, versatility is very strong, can constitute the very strong range-measuring circuit of detectability at an easy rate.

In order to achieve the above object, distance measuring equipment of the present invention has: the optical position detecting unit, when incident projects the reflection of light flashlight of object and bias light, export a pair of photo-signal corresponding with this incoming position; Integrating circuit is to carrying out integration from the photo-signal of above-mentioned optical position detecting unit output; Arithmetic element, calculating are carried out the integrated value of integration by above-mentioned integrating circuit to above-mentioned a pair of photo-signal sum and only the side in the above-mentioned a pair of photo-signal are carried out the ratio of the integrated value of integration by above-mentioned integrating circuit; When the integral result of above-mentioned a pair of photo-signal sum during greater than specified amount, above-mentioned arithmetic element is calculated above-mentioned ratio.

In addition, also can be, above-mentioned integrating circuit be the circuit that 3 group inte grations the time are carried out in range finding, and the integral number of times with appointment in the integration of the 1st group and the 2nd group carries out integration, in the 3rd group inte gration, carry out the integration of the integral number of times corresponding with the result of above-mentioned the 2nd group inte gration.

Moreover, also can be that above-mentioned integrating circuit carries out the circuit of 3 group inte grations when being range finding;

Also have remote judging unit, before being begun to carry out the 3rd group inte gration by above-mentioned integrating circuit, poor according to the 1st group inte gration result of above-mentioned integrating circuit and the 2nd group inte gration result judges whether above-mentioned object is present in distant location.

As mentioned above, according to the present invention, can provide a kind of high-precision distance measuring equipment, irrelevant with the specification of microcomputer, the versatility height can constitute the strong range-measuring circuit of detectability at an easy rate.

Description of drawings

Fig. 1 is the circuit composition diagram of the distance measuring equipment that relates to of the present invention the 1st embodiment.

Fig. 2 is explanation calculates the method for photocurrent according to integral voltage a sequential chart.

Fig. 3 is the circuit composition diagram of the video camera total system that relates to of the present invention the 1st embodiment.

Fig. 4 is the circuit composition diagram according to the distance measuring equipment of range of triangle mode.

Fig. 5 is the sequential chart in when range finding among the present invention the 1st embodiment.

Fig. 6 is the process flow diagram of the control sequence during range finding among expression the present invention the 1st embodiment.

Fig. 7 is the circuit composition diagram of the distance measuring equipment that relates to of the present invention the 2nd embodiment.

Fig. 8 is the circuit composition diagram of the distance measuring equipment that relates to of the present invention the 3rd embodiment.

Fig. 9 is the sequential chart in when range finding among the present invention the 4th embodiment.

Figure 10 is the process flow diagram of the control sequence during range finding among expression the present invention the 4th embodiment.

Figure 11 is the process flow diagram of obtaining order of explanation the 3rd group inte gration number of times.

Figure 12 is the process flow diagram of the control sequence during range finding among expression the present invention the 5th embodiment.

Embodiment

Below, with reference to the description of drawings embodiments of the invention.The principle of the active mode distance measuring equipment that uses among the present invention at first, is described.

In the range finding of active mode, principle according to the light quantity range finding is carried out the judgement of object distance, the principle of above-mentioned light quantity range finding is meant, light quantity from the next reflected signal light of object reflection, for reducing, for increasing from the near object of distance measuring equipment from distance measuring equipment object far away.In addition, can utilize standoff distance, and according to the principle of range of triangle, carry out far and nearly more accurately judging for throwing is subjected to, the distance between the optical lens, the light projector photosensitive elements that so-called benchmark line length disposes.In addition, in the range finding of active mode, the speed that also has other, come as the light reflection according to projection is tried to achieve the radar mode of object distance etc.Yet this radar mode circuit complexity is used on specific use, but is seldom used on portable devices such as video camera.

Fig. 4 (A) is the composition diagram of distance measuring equipment of the range of triangle principle of explanation light porjection type.During range finding, the infrared ray that infrarede emitting diode (IRED) 1 sends after light projector lens 2 optically focused, projects on the object (object) 30.Afterwards, from the reflected light of object 30,, be subjected to light by light activated element 4 by sensitive lens 3.And this light activated element 4 uses optical position detecting element (PSD), this PSD output and the light quantity of incident light and the corresponding photocurrent of incoming position of light.Also have, PSD is with respect to the configuration of datum line length direction, and its two ends have 2 output electrodes.If two electrodes of PSD are same current potentials, then export the incoming position photocurrent corresponding of sharing the same light with each distance between electrodes from each output electrode shunting.That is to say, when there is light incident in the central authorities of PSD,, therefore, export equal-sized photocurrent from each electrode of PSD with shunting in 1: 1.

Here, the light incoming position of PSD changes with the object distance L, therefore, if can detect incoming position x, just can calculate the object distance L.That is to say, as shown in the figure, the distance between light projector lens 2 and the sensitive lens 3 is made as B, the focal length of sensitive lens is made as f, when the catoptrical incoming position the optical axis of sensitive lens 3 during as initial point is made as x,, following relation is arranged for the object distance L:

X=Bf/L (formula 1)

The set value of decision when Bf is design, therefore, by detecting x, the object distance L becomes:

L=Bf/x (formula 2).

Here, the output electrode of supposing any end of PSD is present on the optical axis of sensitive lens 3.At this moment, the length between two electrodes of PSD is made as t, the photocurrent sum of exporting from two electrodes of PSD is made as iP0, then photocurrent iP1 and the iP2 from each electrode output uses (formula 3) and (formula 4) expression respectively.

IP1=iP0 (x/t) (formula 3)

IP2=iP0-iP1 (formula 4)

Here, derive by (formula 3)

X=(iP1/iP0) t (formula 5).

That is to say that x can try to achieve by detecting photocurrent iP0 and iP1.And iP0 has inversely prroportional relationship for the quadratic power of object distance L, and still, this relation is only regularly set up at the reflectivity one of and object certain from the value for the projection quantity of light-projecting component (being IRED here).

The 1st embodiment

Below, as the 1st embodiment, illustrate that circuit bank shown in Figure 3, that have the video camera total system of the range-measuring circuit 23 that is connected with CPU10 becomes example.

In the present embodiment, as shown in Figure 3, built-in adjuster 26 by impact damper 55, offers external circuit to the output of adjuster 26 in the same chip of the IC that constitutes CPU10.And the branch pressure voltage of the electric resistance array 29 relevant with the output DCOUT of DC/DC converter is input to A/D converter 37 and is located at the interior operational amplifier 54 of CPU10.

In the DC/DC converter, according to the signal of exporting from the oscillator 56 that is built in the CPU10, transistor 40 carries out conducting control, makes the electric current from battery 22 flow into telefault 3.At this moment, by the voltage that takes place in the telefault 3, electric capacity 25 is recharged.The charging voltage of electric capacity 25 at this moment is DCOUT.Then, after the dividing potential drop, this branch pressure voltage is input to A/D converter 37 to this DCOUT in electric resistance array 29.According to the detected value of this A/D converter 37, CPU10 monitors branch pressure voltage.

Yet, only often monitor result's the program of A/D converter 37 and insufficient sometimes.That is to say that must carry out under the occasion of High-speed Control, the result of reading in A/D converter 37 is free the hysteresis the needed time, just can not carry out accurate control in the long time.And as the example of this High-speed Control of needs, for example, the situation of the write time control when writing the date on film and detecting under the situation of zoom lens position must be monitored boosting of DC/DC converter etc. sometimes simultaneously.

So, in the present embodiment, with operational amplifier 54 comparer of given voltage DA1, DA2 (hereinafter to be referred as comparer 54) and using as a comparison.In the time of in DCOUT reaches specified level, the decision circuitry 50 of making this judgement is closed vibration shut-off circuit 45, the boost action of the DC/DC converter that stops to boost.And this vibration shut-off circuit 45 is not the vibration that merely stops the DC/DC converter, but the output voltage when vibration stopped to be changed to fixing L level, so that the transistor 40 when vibration is stopped still not to be in conducting state.

With reference to the sequential chart of Fig. 9, the control of the DC/DC converter in this built-up circuit is described.In this control, DCOUT is controlled in the specified level.And D/A converter 36 can switch the judgement voltage that is input to comparer 54 according to the program that is written among the not shown ROM.Thus, the judgement voltage of comparer 54 can be selected from two kinds of voltages of DA1 shown in Figure 9, DA2.

That is to say, use the voltage DA1 of high-side when boosting.On the other hand, boost when stopping and using the voltage DA2 of low level side.Decision circuitry 50 judges according to the output of comparer 54 whether DCOUT surpasses selected judgement voltage.Surpassed judgement voltage if be judged as DCOUT, then decision circuitry 50 switching controls of shut-off circuit 45 and working routine of vibrating.

Like this, after cell voltage boosted, the output of adjuster 26 was supplied with as the reference voltage of D/A converter 36, A/D converter 37 and lcd driver 21, worked by the constant pressure source of impact damper 55 as outside each circuit of CPU10 simultaneously.For example, the output of adjuster 26, as the light interrupt circuit 47 (being labeled as MTPI among the figure) that detects motor 47 rotations, show with LED38, write down various data EEPROM39 etc. power supply and work.

And the output of adjuster 26 also can be used as the power supply of stablizing AF portion 71 and uses, and the size of not shown light-projecting portion being carried out inciding when light projector is controlled the light signal of light activated element 70 detects in AF portion 71.

And in circuit shown in Figure 3, the output pulse of oscillator 56 is also as the charging pulse of flasher circuit 17 and use.A/D converter 37 is also monitored the charged state of the flasher in the flasher circuit 17.

Again, the output of D/A converter 36 also is input in the operational amplifier 59, and motor driver 46 allomeric pipes 48 are carried out constant voltage driving together.Then, motor driver 46 carries out the speed control of motor 47.And, not from adjuster 26 supply powers, but directly take out supply voltage, so that the operational amplifier 59 that this motor driver is used also can be high voltage withstanding from DCOUT.

Also have, in the circuit of Fig. 3, utilize clock circuit 60 instrumentations that the date writes usefulness to carry out timing from the pulse of oscillator 41 outputs.And, this oscillator output multiplication in multiplier (frequency multiplied clock) 35, the major clock of generation CPU10.

Moreover (RESET) circuit 57 that resets resets CPU10 when the residual quantity of battery 22 disappears, and correctly restarts CUP10 when battery refills.

Below, the distance measuring equipment of the present invention the 1st embodiment is described with reference to Fig. 1.Fig. 1 is and has used the light quantity range finding of active mode and the distance measuring equipment of range of triangle.Just,,, utilized the distance measuring equipment of range of triangle here as the distance measuring equipment of light quantity range finding.

The light quantity range finding, the change in voltage when having the range finding result to rely on power supply use battery and the shortcoming of object reflectivity.But this shortcoming can use range of triangle to overcome.This point can be clear and definite from above-mentioned (formula 2).That is to say that in range of triangle, shown in (formula 2), the object distance L is just by B, f and x decision.Therefore, just can calculate correct distance as long as can obtain correct x.But, when object is present in distant location, the incident light quantity of light activated element is reduced to some extent, therefore can not obtain correct x.In this case, use simple light quantity to find range, distance accuracy can improve.

In the present embodiment, in order suitably to switch this 2 kinds of distance measuring methods, transistor is used (below, be called switch 13 comprising this transistorized on-off circuit) as switch.Thus, the open/close state of the feedback loop by control operational amplifier 6b is controlled the photocurrent of light activated element (PSD) 4 outputs.Here, " switch element " put down in writing in the switch 13 respective rights claims, " the optical position detecting unit " put down in writing in the PSD4 respective rights claim.And, " the 2nd amplifier " put down in writing in the operational amplifier 6b respective rights claim.

That is to say that if reduce the transistorized base current of switch 13, operational amplifier 6b just is in conducting state.For this reason, the photocurrent iP from PSD4 all flows to operational amplifier 6a side.

Among Fig. 1, resistance 7 and electric capacity 5a, 5b form Hi-pass filter.This Hi-pass filter filtering only allows the composition that exchanges change pass through and arrival operational amplifier 6a side from the composition (low frequency part) that stably changes in the output photocurrent of PSD4.

That is to say, when putting switch 14 continuously and project the infrared light of pulsed on the object 30 from IRED1, only allow and pass through Hi-pass filter from composition in the reflected signal light of object 30, that be modulated into pulse type by what PSD4 was subjected to light in open/close state.Below, the photocurrent of this modulation composition is made as iP.In addition and reflected signal light incide steady-state light compositions such as the sunshine of PSD4 and artificial light together and in Hi-pass filter, filtered, flow into GND by resistance 7.Here, " the light projector unit " put down in writing in the IERD1 respective rights claim.

By the photocurrent iP of Hi-pass filter, be enlarged into current amplification degree β doubly by the amplification of transistor 8.Afterwards,, flow into integrating capacitor 12, give integrating capacitor 12 chargings through the current mirroring circuit that constitutes by resistance 11a, 11b and a pair of PNP transistor 9.Here, comprise " amplifying circuit " put down in writing in the circuit respective rights claim of Hi-pass filter, operational amplifier 6a and transistor 8.And, " the 1st amplifier " put down in writing in the operational amplifier 6a respective rights claim.

And, the charging of integrating capacitor 12, be integral action, can stop by the close current mirror circuit.The current potential that the open drain lead-out terminal 17 of conducting CPU10 (below be called INT terminal 17) reduces resistance 11b gets final product.Also have, the occasion of dividing the electric charge of savings in the electric capacity 12 when initial eliminate indigestion, open drain lead-out terminal 18 that can conducting CPU10 (below be called RST terminal 18) gets final product the two-terminal-grounding of integrating capacitor 12.Here, during the circuit respective rights that comprises integrating capacitor 12 and this integrating capacitor 12 is carried out the CPU10 of integration control requires " integrating circuit " of record.

Moreover above-mentioned switch 13 and the switch 14 that carries out the on/off operation of IRED1 also can utilize the open drain lead-out terminal 19,20 (being called CH terminal 19 and IRED terminal 20 respectively) of CPU10 to carry out ON/OFF control respectively.

Here, CPU10 uses single-chip microprocessor calculation machine etc.In recent years, the most built-in above-mentioned open drain terminals of microcomputer and mould/number (A/D) change-over circuit.These according to the program that is recorded among the ROM that is built in the CPU10, are controlled by the control part 16 of CPU10 inside.

And the input terminal of operational amplifier is the base terminal of internal transistor.That is to say, among Fig. 1, even the base stage of transistor 8 is states of photocurrent iP=0, because the base current ib of the input terminal of operational amplifier 6a, and often be in bias state.Therefore, the collector current of transistor 8 at this moment becomes β ib.In addition, when making IRED1 luminous, the base current of transistor 8 becomes ib+iP, so the collector current of transistor 8 becomes β (ib+iP).

And in the present embodiment, the input of operational amplifier 6a, 6b "+" end is fixed as given voltage Vref.Be in conducting at switch 13, be the feedback loop of operational amplifier 6b be in conducting during, the current potential of the operational amplifier side of electric capacity 5a, 5b, all the imaginary short effect because of operational amplifier becomes same potential Vref.Therefore, the photocurrent that produces at PSD4 splits into iP1 and iP2 according to the incoming position that incides the reflected signal light of PSD4, and photocurrent iP1 flows into the amplifying circuit of being made up of Hi-pass filter, operational amplifier 6a and transistor 8 afterwards.

In addition, the off switch 13 and when feedback loop of operational amplifier 6b is closed, become the equivalent circuit shown in Fig. 4 (B).At this moment, the side terminal of operational amplifier 6b is in conducting state.For this reason, the photocurrent that produces among the PSD4 is not shunted, and all flows into operational amplifier 6a side.That is to say, in this case, photocurrent flow into amplifying circuit with iP0=iP1+iP2.

Therefore, if detect photocurrent iP0 and P1 in ON/OFF, just can obtain x by above-mentioned (formula 5) by putting switch 13.And these current values iP0 and iP1 can detect by the integral voltage VINT that reads in above-mentioned integrating capacitor 12 through A/D change-over circuit 15.

That is to say,, just can make integral voltage VINT be increased to VINT1 according to size from the output photocurrent iP of PSD4 from VINT0 if the n channel transistor of each terminal of CPU10 is carried out ON/OFF control according to sequential chart shown in Figure 2.And VINT0 makes the not luminous and integral voltage of integrating capacitor 12 when carrying out integration of IRED1, and VINT1 makes the luminous and integral voltage of integrating capacitor 12 when carrying out integration of IRED1.Here, be that the ON time of CINT, INT terminal 17 is that tINT, integral number of times are P time if establish the capacity of integrating capacitor 12, then

VINT0=p β ibtINT/CINT (formula 6)

VINT1=p β (iP+ib) tINT/CINT (formula 7)

Set up.By these (formulas 6), (formula 7), can draw:

VINT1-VINT0=p β iPtINT/CINT (formula 8)

Therefore, if p, β, tINT, and CINT be changed to fixed value, just can calculate photocurrent iP by asking VINT1-VINT0.

Here, in the present embodiment, the ON/OFF of luminous having it's too late CH terminal 19 is switched to IRED1, carry out as shown in Figure 53 group inte grations of each integral action of P time as 1 cover.Afterwards, by being built in the A/D change-over circuit 15 in the CPU10, read integral voltage V0, V1, V2.Then, obtain iP0, obtain iP1 by obtaining V2-V0 again by obtaining V1-V0 from these integral voltage values.X is obtained in these substitutions (formula 5), calculate the object distance L by (formula 2).

Fig. 6 is the process flow diagram of the control sequence of expression when finding range based on above-mentioned logic.

Step S1～S13 places integration under " H " level (OFF) state at CH terminal 19.Here, at first CH terminal 19 is changed to (step S1) after " H " level, and RST terminal 18 is changed to " H " level, removes the reset mode (step S2) of RST terminal 18, beginning integration (step S3).Then, CPU10 is at the integration (step S4) through the predetermined number of times that judges whether to have carried out to become benchmark after fixed time tINT p time.If be judged as the integration of not finishing predetermined number of times p time, return step 3 and proceed integration.In addition, when being judged as the integration that has carried out predetermined number of times p time, then read the integral voltage V0 (step S5) of the integrating capacitor 12 of this moment by A/D change-over circuit 15.

Finish RST terminal 18 temporarily to be changed to " L " level, the electric charge of initialization savings on integrating capacitor 12 after the reading of integral voltage V0.Afterwards, again RST terminal 18 is turned back to " H " level (step S6).Simultaneously, make IRED1 luminous, beginning integration (step S7).And the integration here is synchronous with the fluorescent lifetime of IRED1 as shown in Figure 5.Then, through after the fixed time tINT, CPU10 has judged whether to carry out the integration (step S8) of predetermined number of times p time.If be judged as the integration of not finishing predetermined number of times p time, return step 7 and proceed integration.In addition, when being judged as the integration that has carried out predetermined number of times p time, then read the integral voltage V1 (step S9) of the integrating capacitor 12 of this moment by A/D change-over circuit 15.

Thereafter step S10～S14 places integration under " L " level (ON) state at CH terminal 19.Here, at first CH terminal 19 is changed to (step S10) after " L " level, the RST terminal temporarily is changed to " L " level, the electric charge of initialization savings on integrating capacitor 12.Afterwards, make RST terminal 18 turn back to " H " level (step S11) again.Simultaneously, make IRED1 luminous, beginning integration (step S12).And the integration here is also synchronous with the fluorescent lifetime of IRED1.Through after the fixed time tINT, CPU10 has judged whether to carry out the integration (step S13) of predetermined number of times p time.If be judged as the integration of not finishing predetermined number of times p time, return step S12, continue integration.In addition, if in the judgement of step S13, be judged as the integration that has carried out predetermined number of times p time, then read the integral voltage V2 (step S14) of the integrating capacitor 12 of this moment by A/D change-over circuit 15.

Detect after integral voltage V0, V1, the V2, utilize these values to judge the distance of object, obtain the object distance L.In the explanation of back, be made as closely L0 to the near situation of the distance of object, be made as remote L2 to the situation of the distance of object, the distance of between is made as middle distance L1.The relation that has L0＜L1＜L2 between them.

At first, calculate V1-V0, that is to say and calculate iP0.Then, judge that whether this calculated value is than designated value Δ V (specified amount of putting down in writing in claims) little (step S15).When being judged as V1-V0 littler than designated value Δ V the time, being judged as the object distance L is remote L2 (step S16), the control of process ends.In this case, just become and utilize light quantity range finding to ask the object distance.

In addition, in the judgement of step S15, when being judged as V1-V0, can utilize range of triangle to ask the object distance greater than designated value Δ V.In this case, also calculate V2-V0.Afterwards, ask the ratio of V2-V0 and V1-V0, i.e. iP1/iP0.Then, judge that this ratio is whether than the judgment value R1 little (step S17) of appointment.Ask " arithmetic element " put down in writing in the computing respective rights claim of this ratio.If the judged result among this step S17 is that iP1/iP0 is littler than judgment value R1, then be judged as middle distance L1 (step S18), the control of process ends.In addition, in the judgement of step S17, when judging ip1/ip0, be judged as closely L0 (step S19), the control of process ends greater than judgment value R1.

As mentioned above, according to present embodiment, can provide and only use influence that is built in the interior function of CPU10 and simple common components, the reflectivity that is not subject to object and cell voltage variation usually and the distance measuring equipment that utilizes the range of triangle mode.Operational amplifier commonly used, majority is that 2 are formed as 1 assembly.In addition, comprise the transistor circuit (switch 13 and switch 14) of resistance and, also proposed the structure of multiple both cheapnesss and miniaturization by 2 a plurality of transistors (transistor 9 etc.) of forming 1 group.For this reason, can make distance measuring equipment, also can save the space with low cost.

The 2nd embodiment

Below, with reference to Fig. 7 the 2nd embodiment of the present invention is described.Among the 2nd embodiment, omitted current mirroring circuit, replaced and use analog switch 12a to carry out the ON/OFF control of integration.And resistance 12b is using high impedance.This resistance 12b is that in time process makes integrating capacitor 12 discharge the resistance of shelving the usefulness that resets of electric charges.

In the circuit of this Fig. 7, make the luminous of analog switch 12a and IRED1 place conducting synchronously, thus, produce the voltage corresponding on the integrating capacitor 12 with photocurrent.Read this voltage by the not shown A/D change-over circuit that is built in the CPU10, carry out the detection of photocurrent.

And, in the present embodiment,, when the photocurrent of shunting PSD4 output, use analog switch 13a in order effectively to use by 2 analog switches of forming 1 assembly.The switch 13 that this analog switch 13a is corresponding above-mentioned, by putting analog switch 13a in opening state, the output photocurrent of PSD4 splits into iP1 and iP2.In addition, close analog switch 13a, the output photocurrent of PSD4 can not shunted, photocurrent and iP0 (=iP1+iP2) flow into amplifying circuit.

As above illustrated, in the present embodiment, do not use current mirroring circuit just can carry out the action identical with the 1st above-mentioned embodiment.

The 3rd embodiment

Below, use Fig. 8 that the 3rd embodiment of the present invention is described.The 3rd embodiment does not use operational amplifier, is only with the example of transistor (transistor 30, transistor 32) and resistance (resistance 31, resistance 33) built-up circuit.

State in the use in the example of operational amplifier, rely on the operational amplifier imaginary short effect that "+" side terminal is fixed into the given voltage Vref of benchmark, "-" side terminal of the operational amplifier 6a of input photocurrent also is fixed on the given voltage Vref.But, in the present embodiment,, mobile from the photocurrent of PSD4 for the current potential of VCC and BE.

CPU10 is by carrying out the output photocurrent that ON/OFF is controlled PSD4 to grounding switch 34.That is to say that when grounding switch 34 was not in ground state, transistor 30b and 32b ended.Thus, from the whole inflow transistor 30a of the output photocurrent side of PSD4.In addition, when grounding switch 34 was in ground state, the base potential of transistor 30a and 32b was identical, split into iP1 and iP2 from the photocurrent of PSD4.As a result, having only photocurrent iP1 to be exaggerated circuit amplifies.

As above illustrated, in the present embodiment, do not use operational amplifier, also can carry out and the above-mentioned the 1st and the 2nd identical action of embodiment.

The 4th embodiment

Below, the 4th embodiment of the present invention is described.This 4th embodiment, its compositions is the same with the 1st embodiment, but when utilizing CPU10 to find range, especially the control sequence difference of integration control.

In the above-mentioned control sequence, the 1st group to the 3rd group all is to carry out integration control with identical integral number of times P, therefore, even the occasion of the high object of reflectivity, be the big occasion of light quantity of reflected signal light, also need to set and make the undersaturated integral number of times of integral voltage.But in this case, when the reflectivity of object hanged down, integral voltage was also low.At this moment, just become with lower S/N ratio to find range, the danger of distance accuracy variation has been arranged.

So, in the present embodiment, control according to sequential chart as shown in Figure 9.Among Fig. 9, at first, carry out the integration of the 1st group and the 2nd group at the state that CH terminal 19 is changed to " H ".About the integral number of times in the 1st group and the 2nd group inte gration, consider the influence of the deviation of the deviation of light projector light quantity and magnification, be set at the integral number of times q that makes the certain undersaturated appointment of integral voltage.Afterwards, the IRED1 that carries out the 1st group IRED1 and do not have luminous integration and the 2nd group has luminous integration.Then, according to the size of the integral voltage V1 that obtains from the 2nd group inte gration, decision the 3rd group integral number of times r thereafter carries out the 3rd group inte gration.For the determining method of the 3rd group integral number of times r, describe in detail in the back.

Carry out the 3rd group integration control as described above, even the very high object of reflectivity also can not make integral voltage saturated and carry out integration, and, even if the low object of reflectivity can guarantee that also sufficient S/N ratio finds range.Figure 10 is the process flow diagram of the control sequence in when range finding in the expression present embodiment.

Among Figure 10, obtain step S40～S48 of integral voltage V0 and V1, identical with above-mentioned Fig. 6, carry out simple declaration.At first, CH terminal 19 is being changed under the state of " H ", is not making IRED1 luminous and to carry out integral number of times be q time integration, obtaining integral voltage V0.Then, make IRED1 luminous and to carry out integral number of times be q time integration, obtain integral voltage V1.

Obtain after the integral voltage V1, CH terminal 19 is switched to " L " (step S49).Then, calculate the 3rd group integral number of times r (step S50).The method of the integral number of times r that obtains the 3rd group is described with reference to Figure 11 (A) and 11 (B) here.

Figure 11 (A) is a method of obtaining the 3rd group integral number of times r by computing.That is to say that if the saturation voltage of integrating capacitor 12 is made as Vsat, integral voltage V1 then shown in Figure 9 and the degree of tilt of V2 equate that therefore, integrating capacitor 12 undersaturated integral number of times r can be tried to achieve by following formula.

R=INT (Vsatq α/V1) (formula 9)

Here, INT means parenthetic value is rounded.And α is the well-to-do rate to Vsat, uses the value less than 1.For example, integral voltage V2 is made as 80% o'clock of saturation voltage Vsat, α=0.8.After (formula 9) setting integral number of times r, skip the flow process of Figure 11 (A), carry out the later control of step S51 of Figure 10.

In addition, the judgment value VR of V1 value and appointment is compared in Figure 11 (B) expression, according to this comparative result, selects the integral number of times r1 of setting in advance and any among the r2, as the 3rd group integral number of times.Here, integral number of times r1 and r2 have the relation of r1＞r2.

That is to say, obtain after the V1, judge that whether this V1 is than fixed judgment value VR little (step S70).The judged result of this step S70 if be judged as V1 less than VR, as integral number of times r (step S71), afterwards, is skipped this flow process to the r1 that can set more integral number of times, carries out the later control of step S51 among Figure 10.In addition, if the judged result of step S70 when being judged as V1 greater than VR, is set at integral number of times r (step S72) to r2, skips this flow process, carries out the later control of step S51 among Figure 10.

Here, return the explanation of Figure 10 once more.After step S50 sets integral number of times r, RST terminal 18 temporarily is changed to " L " level, the initialization savings is at the electric charge of integrating capacitor 12.Afterwards, make RST terminal 18 turn back to " H " level (step S51) once more.Simultaneously, make IRED1 luminous, beginning integration (step S52).Through behind the fixed time tINT, CPU10 has judged whether to carry out the integration (step S53) of predetermined number of times r time.If be judged as the integration of not finishing predetermined number of times r time, return step S52 and continue integration.In addition, when being judged as the integration that has carried out predetermined number of times r, just read the integral voltage V2 (step S54) of the integrating capacitor 12 of this moment by A/D change-over circuit 15.

Obtain after integral voltage V0, V1, the V2, utilize these values to calculate the object distance L.At first, calculate V1-V0, and judge that whether this calculated value is than designated value Δ V little (step S55).If it is littler than designated value to be judged as V1-V0, judge that the object distance L is remote L2 (step S56), the control of process ends.

In addition, in the judgement of step S55,, can ask the object distance by range of triangle if when being judged as V1-V0 greater than designated value Δ V.Just, V0 and V1 are the A/D value of integral number of times when being q.So, in order to be converted into the value of integral number of times when being r, will the V0 ' of the superior r/q of value of V0 and V1 (=V0r/q) and V1 ' (=V1r/q) be used for later computing.And V2 is constant.And the appointment judgment value R1 of Fig. 6 is the value of expression ratio, does not have the influence of integral number of times.So, use the judgment value R1 identical here with the 1st embodiment.

Afterwards, calculate V2-V0 '.Then, ask the ratio of V2-V0 ' and V1 '-V0 '.Secondly, judge that whether this ratio is less than R1 (step S57).If the judged result of this step S57, the ratio that is judged as V2-V0 ' and V1 '-V0 ' are during less than R1, judgement is middle distance L1 (step S58), the control of process ends.In addition, in the judgement of step S57, if the ratio that is judged as V2-V0 ' and V1 '-V0 ' during greater than R1, judgement is L0 (step S59) closely, the control of process ends.

The 5th embodiment

Below, the control sequence in when range finding among the 5th embodiment is presented on the flow process of Figure 12.

The flow process of this Figure 12 is represented, the processing that the carrying out of the step S55 that is equivalent to Figure 10 judged at a distance, carries out immediately after reading integral voltage V1.That is to say that among Figure 12, the A/D of integral voltage V1 reads (step S88) after the end, calculates V1-V0, judges that whether this calculated value is than designated value Δ V little (step S89).The processing of this step S89, the function of " the remote judging unit " put down in writing in the respective rights claim.

When being judged as V1-V0, judge that the object distance L is remote L2 (step S56), the control of process ends than the little occasion of designated value Δ V.

In addition, if the judged result of step S89 when being judged as V1-V0 greater than designated value Δ V, switches to " L " back (step S91) to CH terminal 19, begins the 3rd group inte gration.And, the 3rd group integration control, identical with step S49～S54 and the step S57～S59 of Figure 10, so omit its explanation.

If the flow process of Figure 12 is according to the above description controlled,, transfer to step S90 from step S89 when object is present in when remote.At this moment, do not carry out the action of the step S91～S96 suitable with step S49～S54 of Figure 10, therefore, not only can shorten the range finding time, it is luminous also needn't to carry out unnecessary IRED, is beneficial to the saving energy.

And, in the flow process of Figure 12, be that the step S55 in the relevant flow process of Figure 10 is moved to before the step S49, also be suitable for this 5th embodiment among the 1st embodiment.That is to say that even the step S15 in the flow process of Fig. 6 is moved to before the step S10, also can obtain the effect of the 5th embodiment, this is self-evident.

Based on the foregoing description the present invention has been described, but the present invention is not limited to the above embodiments, wants in the point range, can carry out various distortion and application is self-evident of the present invention.

Claims (1)

1. distance measuring equipment is characterized in that having:

Optical detecting unit, when incident when projecting the reflection of light flashlight of object and bias light, export a pair of photo-signal corresponding with this incoming position;

Integral unit is to carrying out integration from the photo-signal of above-mentioned optical detecting unit output; And

Arithmetic element, calculate the integrated value of carrying out integration from a pair of photo-signal sum of above-mentioned optical detecting unit output when carrying out the light projection to above-mentioned object by above-mentioned integral unit with by above-mentioned integral unit for integrated value poor that when above-mentioned object carries out the light projection, does not carry out integration from a pair of photo-signal sum of above-mentioned optical detecting unit output;

When the difference of above-mentioned integrated value during, be judged as and carry out, and calculate the number of times of integration to above-mentioned object light projection and integration once more greater than specified amount; Above-mentioned arithmetic element has been according to having carried out the integrated value of revising with above-mentioned integral number of times of calculating, calculate by above-mentioned integral unit when carrying out the light projection to above-mentioned object from the above-mentioned a pair of photo-signal sum of above-mentioned optical detecting unit output carry out integration integrated value and by above-mentioned integral unit only when carrying out the light projection to above-mentioned object the side from the above-mentioned a pair of photo-signal of above-mentioned optical detecting unit output carry out the ratio of the integrated value of integration.

Images