JPS606820A - Active distance detection device - Google Patents

Abstract

PURPOSE:To improve the accuracy in detection by projecting light to an object to be measured for a prescribed period, receiving the light reflected therefrom in the position corresponding to the distance up to the object, detecting the distance in accordance with the fluctuating component in the quantity of the incident light and delaying the operation for detecting the distance for a prescribed time. CONSTITUTION:The 1st output from a means 1 for generating information on distance measurement is fed by a control means 2 to a signal processing circuit 3. The output from the circuit 3 is fed by a switch means 4 controlled by the means 2 to a storage means and is held therein. The means 1 controlled by the means 2 feeds the 2nd output to the circuit 3. The output from the circuit 3 is fed to an arithmetic means 6 by the means 4 changed over by the means 2 without passing the same through a storage means 5 and at the same time the signal from the means 5 is fed by the means 2 to the means 6, by which the results of the arithmetic operation is calculated. The result of the arithmetic operation is judged by a distance judging means 7 and is fed as distance information to the succeeding stage.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a distance detecting device, particularly an active distance measuring device that projects light onto a distance measuring object for a predetermined page period and detects the distance nlL to the object based on the reflected light. Let's start with the device that controls the detection timing of the detector ft.

The light emitting element of the current 11 old Pb type distance detection device is as follows:
Generally, light-emitting elements such as infrared light-emitting diodes (hereinafter referred to as 1RBD) are used, but these light-emitting elements do not always generate a constant amount of light emitting energy from the time they start turning on until they are turned off, and they do not generate self-heating. Immediately after the light is turned on, a bright energy is generated, but as the self-heating increases, the energy decreases.

Even if a light emitting element with such unstable output characteristics is used, conventional distance detection devices, ie, a light emitting system or a light receiving system f, cannot be mechanically scanned. Detect the changing point of the photometer and calculate the distance r
(In the case of the distance detecting device i'! that detects t, no problem occurs because the change in the receiving bar 9M due to mechanical scanning is so large that the temporal fluctuation in the light emitting output of the light emitting element can be ignored. It took a long time.

On the other hand, another distance detecting device does not have a movable f(1; minute), but instead has a plurality of light receiving elements in the light receiving system.

Even in the case of a distance detection device that detects distance by detecting the closest light receiving element of the incident light, the light emitting element only generates pulsed light, and each light receiving element detects the relative value at the same time. Since it is a method that involves

However, the distance detection device does not have any moving parts and uses a method that drives a light emitting element for a predetermined period of time in order to improve the S/A ratio. More specifically, it has a fixed light emitting and light receiving system, and the distance detection device uses a method that drives a light emitting element for a predetermined period of time in order to improve the S/A ratio. A light beam is continuously projected, and the reflected light is incident on the receiving system at a position corresponding to the distance to the distance measurement object, and distance measurement is performed based on the fluctuation of the incident light that changes depending on the distance to the distance measurement object. In the case of a distance detection system that detects the distance to an object, if the light emitting output of the light emitting element fluctuates over time, the fluctuation will immediately affect the distance measurement information, causing a big problem as accurate distance If information cannot be obtained. was.

An object of the present invention is to provide a distance detecting device based on the third method, which uses a light emitting element having the characteristic 7 as described above as a light emitting element, and is capable of obtaining even a poor detection accuracy. It is.

The present invention will be explained in detail below using the drawings.

FIG. 1 is a schematic diagram for explaining the principle of a distance detection device for a camera to which the present invention is applied, and FIG. 2 is a plan view of the light receiving element shown in FIG.

In Fig. 1 and 'Pj2, 1RFD is a light projecting element that emits linear infrared light to the object ob1 through a light projecting lens L1.
．． Project onto ob2. L2ij: From the objects ob1 and ob2 to be distance measured, two light receiving elements 5Pc1. SPC! I'm turning 20! 1: It is a light-receiving lens. Light-receiving element 5POI An image formed by the reflected light from the subject on JJPC2 is continuously perpendicular to the light projection axis (hereinafter referred to as the base line length direction) depending on the distance of the subject.
Swamp and move on 11!1.

Therefore, since the structure of the light receiving elements 5pa1 and 5pc2 is in the form of a servant shape as shown in the second figure, the output of the elements changes according to the change in the distance to be measured.If the output of one of the light receiving elements increases, the output of the other light receiving element increases output decreases.

The outputs of the light receiving elements 5pa1 and 5pa2 are
, B, normalized by (A-1-B) i'', ,
Ky number, for example, A/(A+B) is indicated at the position of the object to be measured.

Note that an autofocus device is realized by controlling the amount of movement of the photographing lens using the output of the device.

FIG. 3 is a schematic diagram of an embodiment of a distance measuring device to which the present invention is applied.

In FIG. 3, 1 is, for example, the light receiving element 5PCI, SPC! shown in FIG. 2. The distance varies depending on the distance to the object to be measured. 'i'G1+1ltll distance which outputs the second distance measurement signal in a time-divisional manner]n report generation means.

2 is the distance measurement 1N report occurrence 1,111. Signal processing circuit 3, described later
, switch means 4. Dividing the storage means 5, the calculation means 6, and the distance determination means 7? In this embodiment, an electric switch is used to control f1111, but a member that is linked to the pressing operation of a button (not shown) is used to control +3:
' by switching a mechanical switch, or by changing the light receiving element F.
There is also a method H4 in which a mask is provided in lpc1e8pC2 and the mask is moved in the order of 11N1 of 2i to control the output of the ranging 1a information generating means. 6 is a front/water signal processing circuit which performs the signal section 111 such as amplification. Reference numeral 4 denotes switch means 1 for transmitting the output of the signal processing amount P83 to the storage means 5 and the λγ means 6, which will be described later, depending on the type 81 or time division mode of the information generated from the distance measurement information generation means 1.

5 storage means for storing the output of the signal processing circuit 6;
is an arithmetic means for calculating the output of the storage means 5 and the output of the signal processing circuit 3 which is directly output from the switch means 4. , 7 is the subject pressure 1! from the output of the above-mentioned Hamacho lower means B! ′!
ft as a mark (7, a distance judgment means 1'-- which outputs all control signals to a display circuit (not shown) or a hammer-shaped lens system sub-circuit (not shown).
It is y.

Next, I'li of the implementation fl constructed as above,
b) Explain 'F. By means of the auxiliary means 2, the output of the output circuit 1 of the measurement signal generating means 1 is necessarily sent to the signal processing circuit.

Control 9 is controlled by means 2 and switch hand p 74.
The output of the Niji signal processing circuit 3 is sent to the recording means and held there.Then, it is controlled by the controlling hand 2 and (liil distance 1'
The FF signal generating means 1 sends a second output to the signal processing circuit 3. ! tlJ 6m The output of the signal processing circuit 3 is sent to the means 6 by the switch means 4 without passing through the storage means 5, and at the same time, the output of the signal processing circuit 3 is sent to the means 6 by the side turning means 2. The I+¥ number is sent to the calculation means 6, and the calculation result is calculated.The calculation result is determined by the distance rlt determination means 7, and the distance ll++ is sent to the ?& stage with the information ?14.

Next, a concrete example of a distance detection device for a camera (also referred to as a distance measuring device) to which the present invention is applied will be described with reference to FIG.

In FIG. 4, 1RED is a light projecting element that projects light onto an object to be measured (not shown) through a lens (not shown) such as Ll shown in FIG.
do. 1RDR KE1RED iFor 1RED that blinks with a predetermined light threat! ; It is a PAJI・H circuit.

+1181. MS2 is an analog switch composed of MO6FJST, MSB1, MSB2 is +AOB-FF
iT MSj, a buffer amplifier that amplifies one on-off word of MS2, an amplifier (hereinafter referred to as an operational amplifier) MA is configured as shown in Figures 1 and 2 of the previous τ. An amplifier with a high and large cain beam dancer that converts the output current of the light receiving element 5PO1゜5pc2 into a tonden resistor Rs + R,
, the negative part j! borrowed from capacitor C1 i! The DC suppressor has an eye ρ by the path. %Al is an inverter that receives a signal with a DC component cut off at its non-inverting input terminal via a bypass filter formed by a capacitor C2 and a resistor R8, and inverts the output signal +'y of the signal amplifier PA, and iNT is a capacitor. Together with C5, there is a Miller integrator circuit (+- configuration, 2 operational amplifier that integrates the output of the preamplifier FA, 13PA, 5iNV
, 5DSC! Keoff 1'! ? [f (An analog switch that does not cause a voltage drop, connected to the inverting input terminal of the R11 operational amplifier iNV, and a resistor, OPl, (!l'2.O
n is a comparator, R1! l, R14, R15 comparator ap1. The resistor R13 is connected in series with each other, and one end of the resistor R13 is grounded.
One end of 5 is connected to a 1 volt power source.

A well-known circuit for generating an OSake clock signal
CIl-1: Divide the clock signal from C8C by 172Kl, and output a signal with the same frequency as the divided output whose phase is shifted by one clock width. ) Johnson counter 1. ulDId: Uses an AND gate to determine the completion of distance measurement and when a high level (hereinafter referred to as H level) power signal is output from the latch circuit JLC (described later), that is, during distance measurement operation. When a low-level signal is output from the distance measurement completion judgment and latch circuit JLO, which will be described later, that is, l1ll lil: f''
After the Jb operation is completed, the divided output from the Johnson counter JC is processed by an AND gate that prohibits sending it to the frequency dividing circuit Div, which will be described later, and Div is the frequency dividing circuit that further divides the clock signal. Send it to the binary counter BC and also send it to the binary counter BC.
2) The output number τ of each stage is sent to the interval decoder iiD for integral characteristic compression in 7. The 4-bit 211q counter, which is set up by the OC flip-flop, counts the output 1J@4 of the 1-frequency divider circuit D1v, and sends it to their timing overturning decoder TOD and distance measurement zone determination decoder ZJD, which will be described later. Provides the output of the valley flip-flop. 1-digit binary counter Be explained by Naoki Example
I will explain 4711 circuits by writing d in 16 steps and explaining the 4711 circuits. Mi: the distance measurement zone determination decoder ZJD; binary counter Be;
The distance zone in which the object to be measured is located is determined based on the distance measurement completion determination signal and the distance measurement completion signal from the latch circuit JLO, which will be described later. fl Ege Nagi If Iiii・: 111 works completed %? 1ill 4. 'If the internal range of the binary counter BC is 7" or fr, t"8" when the huge completion signal is inverted from the IT level to the low level (hereinafter referred to as L level), then the object to be measured is , 11tfi +', +4 zone, "9n is the distance zone, A" is the near tll
T p′! It outputs a signal indicating that it is in the e-zone "B", so to speak, in the close range zone. F and io are external interface circuits that display distance measurement data in response to the output signal of the distance measurement zone determination decoder ZJD.1. , fr, s,
411-Shadow lens (for still cameras, video cameras, etc.)
(not shown). TCD timing system 91'! It is a decoder for IT, binary counter 13
0 signal, various timing signals shown in TCD1 to TOD5 in FIG. , J
ll latch circuit SQL, ilD ili control circuit I
OC%r'+min switch control circuit 1sc, analog switch 5DSCVC feed, control stiffness. This is a compression No. 11 waveform shaping circuit for preventing the F'E condensed call signal chattering detected by the C8C comparator cpl. The exclusive H level signal is held, while the first L level signal output from the comparator CP1 is held during the falling process of the output of the mirror integrator.

iiD is an interval decoder for integral lp compression, and a frequency dividing circuit Di is used to compress the output of the operational amplifier iNT.
The output of v (see AND 1 in Figure 9) is decoded and a pulse as shown in 11D1 in Figure 9 is then sent to the integral switch control circuit 1sc in E to compress the integral characteristic. Analog switch for decision SPA, 5ilf
Create a control signal of f.

This is an integral switch control circuit for isc, and generates signals for controlling the opening and closing of analog switches SPA and 5iNV shown as i, l1ll, and igc2 in FIGS. 5 and 7 from the output signal of the Johnson counter JO.

iCC is the iR1 control circuit, and the 2'$A counter Be
When receiving a signal from the timing control decoder TCD that the content of is °°0'' or 1'', and when the distance measurement completion judgment and IJ-1 output signal of the latch circuit JTIC is at L level, the light emitting element 1RWD Turn it off and then when other than the above! Ho's spa Lumi control latch SCSC
The signal which is the exclusive OR of the utility signal and the output signal of the Johnson counter JO causes the light emitting element 1RgD to reach the point rQd. 5CTJld: OCl in Figure 5, +1
, SC! The SP outputs a pulse as shown by L2.
This is a latch circuit for C control, and during rising integration, the light receiving element 5
Analog switch 148 is set so that the output signal of PO1 is input to the operational amplifier (A).
1°) Control 4S2. PEG is a PUC signal generating circuit that outputs a PUO signal to clear each circuit when the power is turned on 11♀.

Next, the operation of the distance measuring device having the above configuration will be explained using FIGS. 5 to 9.

When the release button (not shown) of the camera is pressed, voltages (V4-, V-) as shown in the fourth diagram are generated from the power supply circuit PU, and the voltages are supplied to the 41st and 2I circuits.

At 11-1, the power-up clear signal PUO is generated from the PUC signal generation circuit PSG, and the Johnson counter JO
, the frequency divider circuit DiV, the binary counter Bc, and the sPC control clock cycle SCL are cleared. When this clearing operation is completed, the Johnson counter JO is activated by the oscillation circuit O.
Count clock number 18 from 8a, and count the clock number 18 from counter J
The output terminal "r05" of O generates an output signal obtained by frequency-dividing the clock signal. , low H level) is given, AND supplies the divided output from the Johnson counter JC to the frequency dividing circuit Div, and the reduced frequency dividing circuit DiV is: 1. Grass input signal (i 9 [
11) AND1 gradient 111) is further divided into A4 and supplied to the binary counter BC as a human input signal. Therefore, 8 of the counters Be gradually increases from 0'' after the power-up clear operation.The output terminal 'l'OD1 of the decoder TCD that decodes the contents of the counter BC is the TOD in FIG.
The contents of counter BC change from '0' to 1 as indicated by 1.
” is at L level, so the 1RKD control circuit iCC
Is the output r'ijA also the contents of counter BC? Holds L level between '0'' and 1'', 1RKD persistent circuit 1RDR
During this period, the light emitting element 1RED is not driven and no light is emitted. Also, the output terminal TCI of the timing control decoder TCD
When the contents of the D2 counter BC are between 0'' and 2'', the L level (see TCD2 in Figure 215) is maintained, and the output terminal 1sc! of the integral switch control circuit 1sO is held. 1.1SO2
is set to L level, so the analog switch SPA, 5i
The NV ij remains off and the integration operation of the mirror integrator is not started. On the other hand, timing control decoder TCD
Since the output i1'JTOD3 of the counter Be is at H level between 0'' and 2'' (TCD3 1 ■ θ in Fig. 5), the analog switch 5DSOl-1 remains on during this period, and the resistors R12 and R11f via comparator O
Connect the output terminal of P3 to the inverting input terminal of operational amplifier TNT, and connect it to 1NT-CF2-808(!-R12-R11-1N
A closed circuit consisting of T is formed. The closed circuit is formed -gf'
Also, for example, the potential at the output terminal of the operational amplifier iNT ■2
is Vr2+OF'2 (however, Vr2 is the potential of the inverting input terminal of the operational amplifier 0P50 forming the comparator, and O
F2 is the offset voltage of the operational amplifier CP3. Since the capacitor C6 is charged via R11, the potential 2 at the output terminal of the operational amplifier iNT gradually drops in accordance with the charging voltage, and the potential V2 at the inverting input terminal of the operational amplifier iNT decreases over a predetermined period of time.
1 and the potential V at the output end of the operational amplifier CP3 reach the same potential, the charging operation for the capacitor C3 stops.

On the other hand, when the 'α position V2 at the output end of the operational amplifier iNT is lower than the potential Vr2 + OF2, the output end of the operational amplifier CP3 becomes an L level, and the resistors R11 and R1
Since the charge stored in the capacitor C3 is discharged through the analog switch 5DSO and the analog switch 5DSO, the potential at the output end of the operational amplifier iNT increases by v2. After a predetermined period of time, the potential v1 of the inverting input terminal of the operational amplifier iNT and the potential Vl of the output terminal of the operational amplifier ap3 are similarly changed in the above case.
When they become the same potential, the capacitor C3 stops discharging Y7°C and becomes stable.

When such a stable state is reached, the potential (2) at the output terminal of the operational amplifier iNT becomes t) at the next peak.

That is, if the increase rate of operational amplifier cp3 is multiplied by α, then 17,
The king's relationship is Vl = V2 +a (V, -Vr, -0F2)
=V1 Generally, the amplification factor α of an operational amplifier (operational amplifier)
)1, the above formula becomes V2-:Vr2
+OF2, and the potential V at the output terminal of the operational amplifier iNT,
is the direction of the operational amplifier cpx (value voltage (vrt, 4-0F2
) K is approximately equal.

As a result, the terminal voltage of capacitor C3 is
The inverting input terminal potential V, ==Vr, -0F1 of T and the non-inverting input terminal voltage V, =Vr of comparator CP3.

+OF2, so the offset T of the operational amplifier iNT and the voltage converter CP3 is
F2 can be automatically compensated, and the output level of the operational amplifier iNT when there is no signal is set to be less than or equal to the reference level (in the case of the example shown in Fig. 4, the reference level is the ground level). As in the example above, if the output of the operational amplifier INT swings in only one direction (positive direction) with respect to the output level at the time of the ladder signal, which will be described later, the output level of the operational amplifier iNT when there is no signal will be grounded. If it is set below this level, the dynamic range of the output of the operational amplifier iNT will be expanded, and the El/N ratio will be improved.

Next, the contents of counter Be (M
(see BC in Figures 5, 7, and 8) becomes "2",
Output of decoder TCD ☆::ATCD1 (@5 TCD
i) is reversed from L level to H level, iRl
The output terminal of the jtl control circuit 100 repeats the I (level and L level) in response to the output signal from the output JO3 of the Johnson counter JO, so the 1RKD drive circuit 1
RDR intermittently activates the light projecting element 1RFiD, and the light projecting element i R1! ! Light is projected onto the distance measuring object through a lens such as the first lens L1 shown in FIG. Immediately after the lighting starts, the internal temperature of the light emitting element 1RED is low.
Although the energy is high, the internal temperature decreases to 1JV due to continuous lighting.
(Then, the emission energy of the light emitting element iR will gradually decrease.Then, the light emitting energy of the light emitting element iR will gradually decrease.
The internal temperature IW of iD is lower than the ambient temperature of the light emitting element.

〈When the so-called thermal equilibrium state is reached, in which the heat generated inside the light emitting element is emitted to the outside world, the light emitting element 1RED
The luminous energy of H2 reaches a stable state. After that, when the value of the counter BC changes from "2" to 63", the output terminal TOD3 of the decoder Tl (see 5M TCD3) is inverted from the I(level) to the L level, so the analog switch 5DS(! Kaisei urT-cps-5D
A circuit company consisting of SO-R12-Rll-ftNT is opened, and an integral 5h operation using a Miller product 4+ machine is started. At this point, the spa system (fly 1 use punching circuit SCL
The output terminal 5CL1 of the output terminal 5CL1 is at the L level, the output terminal 5OL2 is at the H level, and only the light receiving element FIPO1 is connected to the input terminal of the amplifier MA.

After the contents of the counter BC changed to -ge, 4,! At the output terminal of the minute switch control circuit 1so, SOj is 1s in FIG.
The output fi J of Johnson counter JO as shown in Oj
Generates a bus A・S with almost the opposite phase to the pulse from Ol, starts opening/closing the analog switch SPA, and further closes the output terminal 1s.
O2 is the output terminal of the Johnson counter JO shown at 1sa2 in FIG.

Therefore, after the content of the counter Be changes to 3" and the analog switch C for sy is opened as described above, the light from the light emitting element 1 RED reflected by the sidecar object passes through the light receiving element spa 1.
As a result, the amplifier FA generates an output as shown in the waveform FA of FIG. 6(a) according to the intensity of the incident light, and the inverter iNV generates the waveform 1 of FIG. 6(b).
When an output as shown in 1ff occurs, the analog switches SPA and 5iNV change the waveform SPA in Fig. 6(a).
, 5iNv, so that the inverting input terminal of the operational amplifier j and NT forming the Miller integrator receives a signal that always has a negative level as shown by iNT in Figure 6 (al). Therefore, the capacitor C3 continues to be electrically connected for a certain period of time T while the contents of the counter BC are between 3'' and ``6'', and its terminal is replaced by the waveform iNT shown in the figure P!
As shown, it increases according to the amount of light incident on the light receiving element SPOf. Then, when a certain period of time T has elapsed, capacitor C3
When the distance measuring object is close to g (1), the voltage is high, and when the object is far away, it is charged to a low voltage.

Thereafter, the contents of the counter BC change from 1"6" to 1"7", and the output terminal TC of the decoder TOD! When D4 changes from the H level to the L level as shown in the waveform TOD4 in FIG.
EiOL1, EfOL217) are each waveform 5 in Fig. 5.
As shown in cL1.5OL2, the analog switch MS1 is opened and the analog switch S2f is closed, and the light receiving elements 5PO1 and 5PO2 are connected in parallel to the input terminal of the amplifier MA. Due to the change in the output of the output terminal TOD4 of the decoder TcD mentioned above, the output terminal 5OL3 of the latch circuit for the FEPC control 11 also changes from the L level to the H level as shown in the waveform ROTr5 shown in FIG.
e u Johnson counter, pulse 'fiRE' with the phase of the pulse from TO's output zisJa3 shifted by 180'
Supplied to D drive 11 circuit 1RDH. Furthermore, in synchronization with the change in the output terminal TOD4 of the decoder TOD, the other output terminal TOD2 of the decoder TCD changes to the waveform T shown in FIG.
Since it changes from H level to L level like OD2, both output terminals tsci and 1sc2 of the integral switch control circuit 1800 receiving the signal from the output terminal TOD2 become L level and open the analog switches SPA and 5iNV. , interrupts the equinox operation by the mirror integrator, and generates an amplifier M due to the switching of the light receiving elements 8PO1 and 5PO2.
Erroneous distance measurements due to transient fluctuations in A are lost.

When the contents of the counter Be change from "7" to "8" and the output signal of the output terminal TC!D2 of the decoder TOD changes from the L level to the 1iH level again, the analog switch SP
A, 5iNV is the output signal from the output terminals 1sC1, 1s(2 (1sO in FIG. 5) of the integral switch control circuit 180 again.
1, 1sO2)), but as mentioned above, the Gr phase of the pulse output from 1RED control circuit P31 (!0) is the content of counter BC from ``6'' to 7''.
Note 11108 when switching to , light emitting element iR
J! When the iD lights up, the analog switch BPA opens,
Analog switch 5iN when light emitting element 1RF2D is turned off
V will be opened (see FIG. 6(b)).

Therefore, the inverting input terminal of the amplifier iNT with Miller integration 4 is applied from the time when the content of the counter BC shifts to 8'' as shown in FIG.
A positive voltage as shown by waveform iNT in b) is applied. Of course, the positive voltage f- applied to the inverting input terminal of the operational amplifier 1NT is connected to the output of the light receiving element SPCI and 5PO.
The voltage corresponds to the way 2 and 411 appear.

After the content of the counter Be shifts to 8'', the operational amplifier i
When the voltage in the positive direction described above is applied to NT one after another, the output level of the operational amplifier iNT changes to the waveform iNT shown in FIG.
It gradually decreases as shown in . Furthermore, the waveform iNT in Fig. 5
iNT −1 is iNT −1 when the object to be measured is close to
T -2 is when the distance measurement object is medium distance, 1NT-3 is when the distance measurement object is jIh distance, 1l-IT -4 is 1ill
1JIT-5 is the output of the operational amplifier iNT when the distance object is very close and has a high reflectance. The abbreviations are shown below.

Here, the operation will be described when the distance measurement r is a short distance and the output of the operational amplifier iNT exhibits an output characteristic as shown by iNT-1 (see iNTm force in FIG. 5).

The output of the operational amplifier iNT is lr of the comparator CP5,
When the value falls below +, l, the output terminal of comparator CP3 is inverted from H level to L level, and latch circuit JLO
The distance measuring light r.g. is given to. At this time, the output dance of the timing opening/opening decoder T (jD) ij T CD 5 (fE5[
Since T of statement 1 (see jD5) is at H level, launch circuit JLO outputs an L level output signal (JL in FIG. 5) in response to distance measurement completion 1 word from comparator CP3.
C1) if [D fill feeding circuit ice, integral switch control circuit 18G, comparator OP3, AND gate AND, and ranging zone determination decoder ZJD.
give to each of them. For this reason, the light emission of the light emitting element 1RicD is stopped (see jilD in Fig. 5), and both analog switches SPA and Elilf are open (h) (see Fig. 5 isG).
! 1, 1sO2), the group division tυ operation of the Miller integrator is stopped, and the operation of the comparator cp3 is also stopped. Further, the output of the AND gate AND is also inverted from the H level to the L level, thereby blocking the transmission of pulses from the counter JO to the frequency dividing circuit 1'-3DiV. Therefore, the binary counter BC holds the numerical value "A" at the time when the aforementioned distance measurement completion number 46 was output from the comparator OP3, and the distance measuring zone judgment decoder zJDK retains the numerical value "A" which is the content of the counter BC. It will be done. At this time, the distance measurement zone judgment decoder ZJD is given an L level signal from the latch circuit JLIO in response to the distance measurement completion signal from the comparator OP3 as described above. -1n judgment decoder ZJD Fi 1n da I3 from binary counter BC
Based on the distance information of the distance measuring object, the external interface circuit (in this embodiment, the necessary (+) inside the camera will be described in detail.

Integral in the rising direction (Vt min. time Ill T ) The fall of the capacitor C6 at the time 114T in FIG.
It is clear from 7) E pc is equal.

Here, C3... Capacity of capacitor C3, xzil...
・Resistance value of input resistor R11, A... Light receiving element, : 1P
Output C current value of O1, B...output current value of light receiving element BPO2, T...integration time in the above-mentioned upper η direction.

t...Mtl '$ L, integration time in the descending direction l2, α... product of the current-blade pressure conversion constant of the operational amplifier MA and the amplification factor of the operational amplifier FA, and both -r log switch SPA , is a proportional constant a determined by the switching duty ratio of 5iNV.

Equation (2) above shows that when the integration time T is constant, the distance to the lever B, that is, the distance measurement object, can be determined by measuring the integration time t (7 distances). Judgment decoder Z, TDl-j This principle is used in the 11th to calculate the distance +W#, that is, as described above (given by C kakunta Too) 7
Calculate the integral □8♀I'll t from the number rtf\"A", calculate A/A → -B from the known -W gain interval T, calculate the distance to the distance measuring object, and As mentioned above, output the high resistance 1 to the distance measuring object to the external bar 1s interface circuit.

When the object to be measured is at a medium distance, the comparator CP3 generates the above-mentioned distance measurement light r signal when the content of the counter Be is 9'', so the main distance judgment decoder ZJD detects that the object to be measured is It outputs a signal indicating that it is at a medium distance.Furthermore, when the object to be measured is at a very short distance, when the content of the comparator cP3 counter count Be is 8", the above-mentioned distance measurement\no1' completion signal is generated. Distance measurement decoder ZJD
outputs a signal indicating that the object to be measured is far away.

Next, when the distance measuring object is extremely far away, the output level of the mirror integrator has an integral characteristic of 11JT -5 (iNT in Figure 5).
Even when the contents of the counter BC shift to 07'' as shown in (i), the dark value cp2'r of the comparator cp2 (
(see waveform iNT in Figure 5), if it exceeds the timing system? When the output terminal TOD4 of the J decoder TOD is inverted from the H level to the L level, the latch circuit JLO latches the L level signal output from the comparator CP2 in synchronization with this level inversion. As a result, the output of the latch circuit JLO does not change from the level to the L level in response to the inversion of the output of the output terminal TOD4 of the decoder (as in the case where the distance measuring object is within the normal range as described above). Refer to TLOI in Figure 5 [(C), light emitting element i, RF
The light emission of the iD is stopped, the content of the counter Be is held at 7", and the content of the counter Be of the armored zone judgment decoder ZJD is "7" and the latch circuit J.
From the output signal of LO, the external interface circuit Fii outputs a signal indicating that the object to be measured is in a very single-grain ratio group.
Output to C.

Finally, an explanation will be given of the operation when the distance object is at near vision 1ζ1t and has a narrow reflectance.

In such a case, the output iit pressure Vi of the mirror integrator is shown in integral characteristic 1NT L-a in FIG.
PC! It rises rapidly after the start of integration according to the output current from 1. When the signal value of comparator CP1 exceeds 0PtT (iNT reference in Fig. 7)'f, the output of comparator OP1 (cp1 reference 1 in Fig. 8) is inverted from L level to H level, and the compressed signal waveform shaping is performed by the circuit. The output of C8C is the 8th
As shown by the waveform CSC in the figure, the signal is inverted from 1 level to L level. Therefore, the output terminals j, scj of the integral switch control circuit 1 iso.

18c2 F1. ) is the pulse from the integral interval decoder iiD (see 11D1 in FIG. 9N((,'
) Therefore, as shown in the waveform 18c1.1sC2 of FIG. 7, the output cuff 1 pressure of the operational amplifier iNT forming the mirror integrator is as shown in FIG. It rises at a gentle slope.

Then, when the content of the counter BC shifts to "7", analog switches SPA and 5iNV are opened in response to the L level signal output from the output end TCD2 of the timing 1i++ decoder TCD, and the capacitor Since the charging path of C5 is cut off, the integrating operation of the Miller integrator is stopped.

Then, when the content of the binary counter aa reaches 8", the timing '+++lI' occurs at the output terminal T of the NU decoder rOD.
OD217j Reversal from L level J to H level J again and the 5th
Waveform TC in the figure! D2Cj), integral switch control circuit is
The output terminals 1sO1 and 1S02 of o are given by j and 1-8 of the 7th M
Since pulses such as O1, i, and 8c2 are supplied to the analog switches FIPA and 5iNV, the analog switches SpA and 5tNv open and close, and the integration operation starts again. The output depends on the electric current mH, which is the sum of the output current from the photodetector 5PCI and the output current from 5PO2, and during the period T1 (see Fig.
Then, with a slope of -t<, (A+B), the seventh waveform j, NT or the waveform 61NT-4iτ of FIG. 5 gradually drops to the first waveform 4,1. The output of the integrator further decreases and the output of the comparator CP1 becomes 1゛ (1 value OP1'r (
When the waveform iNT reference in FIGS. 5 and 7 becomes less than 1Iio,
The output of the comparator CP1 is inverted from level 1 to L level J, and the output of the compressed signal waveform forming circuit 20 is inverted from level 7- to H level (waveform esc! in FIG. 8).
Output terminal i of the integral switch control circuit 1SC
The duty ratio of the output from B Cj 1 and i S Cj 2 is returned to 1. Therefore, the output of the integrator is m51:ZlnoiNT output (waveform iNT -4
Reference pi() The VC suddenly drops to 1.: as shown in the IC. And the output of the integrator, that is, the operational amplifier iN
The output voltage of T is 1. of comparator CP3. ', tJ value or less, the output of comparator CP3 is inverted to L level, and the completion of distance measurement is judged and the output of latch circuit JLO is inverted (see waveform JLC1 in Figure 5). The light emission of the optical element SO1 LRFiD is stopped, and the distance measurement noon judgment decoder ZJD receives distance ytt information according to the g ("I3") of the counter BC, that is, it indicates that the distance measurement object is at close range. The information is output to the external interface circuit EiO.

As described above, according to the present invention, high distance measurement accuracy can be obtained even if a light emitting element having the above-mentioned characteristics is used as a light projecting element.

[Brief explanation of the drawing]

Fig. 1 is a principle diagram of the distance 1''![mouth detection device 6] to which the present invention is applied, Fig. 2 is a plan view of the light receiving element shown in Fig. 1, and Fig. 3 is a schematic diagram of the distance detection device to which the present invention is applied. Figure 4 shows details of the distance detection device to which the present invention is applied +fl11
circuit diagram, ? The Pjs diagram, FIG. 6(a), R46 diagram (b), and FIGS. 7 to 9 show waveform diagrams of each part of the circuit shown in the fourth diagram. In the figure, 1RED...Light emitting element T (!D,..., Timing control decoder BC forming a delay circuit...Counter iso,..., 1 circuit SPA before integrating switch, 611NV, --7f og switch 1
, NT , , operational amplifier C3,6 capacitor

Claims (1)

[Claims] Means for projecting light onto an object to be measured for a predetermined period;
A distance detection device that detects the distance based on a light receiving means that receives reflected light from the object at a position corresponding to a distance to the object, and a variation of an incident light valve that changes depending on the distance. An active pressure portion detection device, further comprising means for delaying the distance detection operation by a predetermined time from the start of the light projection.