JPS61117407A - Automatic range measuring circuit - Google Patents

Abstract

PURPOSE:To secure automatic range measurement operation by monitoring the output level of a rectifying circuit by a monitor circuit and controlling the quantity of light emission of a light emitting element. CONSTITUTION:Infrared rays are modulated and projected on a subject and its reflected light is converted photoelectrically by a couple of infrared detection sensors Sa and Sb which are arranged nearby and movable at right angles of a subject direction. Their outputs are amplified by narrow-band amplifying circuits 1a and 1b, whose signals are rectified by rectifying circuits 3a and 3b and converted into DC voltage, so that the monitor circuit 6 monitors output levels of the rectifying circuits 3a and 3b. Then, a large/small decision circuit 5 determines the blind sector width of the monitor from the large/small relation of the differential output. Then, a controller 7 determines the moving direction of a lens from which of two output voltages of a channel A (system of sensor Sa) and a channel B (system of sensor Sb) is larger and then judges that the automatic range measuring operation is completed when the difference between those output voltages is within a certain constant channel width range (blind sector area), thereby driving the lens automatically with the output of the device 7 so that said difference is in the state all the time.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention amplifies a modulated optical signal received by a light receiving element with a frequency selective amplification circuit and electrically processes the signal to perform automatic distance measurement. This invention relates to an automatic distance measuring circuit that performs control.

(Prior Art) Many proposals have been made regarding devices that project infrared rays or the like toward an object or subject in front, receive the reflected light with a sensor, and automatically measure the distance to the subject using the principle of triangulation.

Even if such a method is adopted, the amount of reflected light from the subject decreases in inverse proportion to the square of the distance, and there are considerable differences in the shape and reflectance of the subject, so the amount of incident reflected light may be extremely low. However, later signal processing was not easy.

(Object of the Invention) An object of the present invention is to provide an automatic distance measuring circuit that can solve the problems of separating background light and reflected light and the amount of reflected light, and can perform reliable automatic distance measurement. be.

(Structure of the Invention) In order to achieve the above object, an automatic distance measuring circuit according to the present invention projects light from a light emitting element forward, receives the light with a light receiving element, and automatically calculates the distance to a subject based on the incident angle of the reflected light. In the automatic distance measurement circuit that detects the distance, the light emitting element drive circuit amplitude modulates the current flowing through the light emitting element and variably controls the supplied current, and the The first
and a second light-receiving element, first and second narrowband amplifier circuits that selectively amplify the modulation frequency components of the light incident on the first and second light-receiving elements, respectively; first and second AC amplifier circuits that further amplify the output of the second narrowband amplifier circuit; and first and second rectifier circuits that convert the outputs of the first and second AC amplifier circuits into DC voltages. a differential amplifier circuit that detects and amplifies the difference between the outputs of the first and second rectifier circuits; a monitor circuit that monitors the output level of the rectifier circuit; and a distance detection state based on the output signal of the differential amplifier circuit. a comparator for determining the amount of light emitted from the subject, which generates a control signal for controlling the amount of light emitted by the light emitting element drive circuit based on the output of the monitor circuit, and inputs the output from the comparator to the first and second light receiving elements. The light receiving element is composed of a control device that generates a drive signal to move the light receiving element so that the reflected lights of the light receiving elements are equal.

(Example) Hereinafter, the present invention will be described in more detail with reference to the drawings and the like.

FIG. 1 is a block diagram showing an embodiment of an automatic distance glt measuring circuit according to the present invention.

FIG. 2 is a schematic diagram showing the positional relationship between a subject, a sensor, and a light emitting element.

The automatic distance measuring circuit according to the present invention modulates infrared rays and projects them onto a subject Ob in front, and transmits the reflected light to a pair of sensors 3a that are arranged close to each other and are movable at right angles to the subject direction. , Sb is configured to perform photoelectric conversion.

In order to minimize the influence of external light, the signal is amplified by a frequency selective amplifier circuit, rectified and converted into a DC voltage, and the A channel (sensor Sa series) and B channel (sensor sb series) are used. ) The direction of movement of the lens is determined by the magnitude relationship between the two output voltages;
This method determines that automatic distance measurement has been completed and automatically drives the lens to maintain that state at all times.

In Fig. 1, the narrowband 4 amplifier circuits 1a and lb are the object ob.
Sensors Sa and Sb of weak modulated light that is reflected and returned by
This is a narrowband amplifier circuit that amplifies the photoelectric conversion output of

The output is greatly amplified by AC amplifier circuits 2a and 2b. The rectifier circuits 3a and 3b rectify the respective amplified outputs. The differential amplifier circuit 4 is a circuit that amplifies the difference between the two rectified outputs of the A channel and the B channel.

The magnitude determination circuit 5 determines the dead band width of the motor from the magnitude relationship of the differential output. Microprocessor 7 is a CPU that controls the automatic distance measurement sequence.

The infrared LED drive circuit 8 is a drive circuit that modulates the infrared LED and controls the magnitude of its amplification.

The motor drive circuit 9 is a circuit that drives lenses and the like using the output of the microprocessor 7.

The synchronization signal detection circuit 10 is a circuit that generates an interrupt signal to the microprocessor 7 in order to emit infrared light during the vertical retrace period.

The LED is modulated at a certain frequency and reflected by the object ob, and the reflected light enters the infrared detection sensor of the A and B channels. As mentioned above, the infrared light emitting element and the two sensors are arranged in an optical relationship based on the so-called triangulation method, as shown in Figure 2, and when the outputs of the sensors Sa and Sti are equal, the light reception The distance to the subject is detected using the angle formed between the sensor and the light emitting element.

In order to measure the distance between objects, the sensors Sa,
In addition to moving Sb, the amount of lens extension is controlled by a motor for automatic focus adjustment.

FIG. 3 is a circuit diagram showing the automatic distance measuring device having the above configuration in more detail.

The modulated infrared light reflected from the subject is selectively amplified by the A and B channel preamplifiers A1a+Alb (corresponding to the narrowband amplifier circuits 1a and lb shown in FIG. 1) shown in FIG. .

The detailed structure of this circuit is described in detail in the applicant's earlier application, Charging Current Amplifying Circuit (Japanese Patent Application No. 183205/1983). In short, this amplifier circuit is a narrowband amplifier circuit that detects only the frequency component that is the same as the modulation frequency of infrared light and blocks other noises. .

The outputs of the preamplifiers ALa and A1b are respectively amplified by AC amplifier circuits 2a and 2b so that the amplitude of the modulated voltage is about 1 to 2V.

The output voltages of the AC amplifier circuits 2a, 2b are converted into negative DC voltages (-Ea, -Eb) by rectifier circuits 3a, 3b.

The output of the differential amplifier circuit A4 is expressed as Eo = (R4/R3) (Ea-Eb).

When the distance is detected, the DC outputs of the A channel and the B channel are equal, so E becomes zero.

If Ea>Eb, EO>0. If Ea<Eb, then E.

<O, and the driving direction of the lens for focusing is determined.

Comparator A5. A forms the magnitude determination circuit shown in FIG. 1, and converts the logic state shown in Table 1 depending on the magnitude of the voltage of the differential output.

Table 1 (Relationship between logical states of differential output and comparator output) Differential output E, E, >VT VT≧E, ≧VT' V
T'>Ee input terminal L Low High
High input terminal I2 Low Low
High, that is, the differential output EO is VT≧Eo>
If the range of VT' is set to fall within the depth of field range, it can be determined that the area is in focus at Eo.

The microprocessor 7 drives the motor so that the input terminals 11 and 12 become 11=high and 2=low as shown in Table 1. Automatic distance measurement control is thereby performed.

The intensity of the modulated infrared rays incident on the photodetector depends on the reflectance and shape of the subject (flat or curved).

It changes depending on the distance to the subject.

In the case of a long distance, the reflected light becomes weaker, so if the amplification degree of the circuit is constant, the differential output is E. becomes smaller. Therefore, the current flowing through the infrared emitting LED is increased to increase the light emitting output. On the other hand, at short distances, the reflected infrared rays from the subject are relatively thick (if the amplification factor is constant, the differential output EO will be saturated).

Therefore, as a countermeasure, an automatic gain circuit system in which the amplification factor of the circuit is made variable or a system in which the output of the LED is controlled may be considered.

The latter is advantageous due to circuit simplification.

In order to realize this method, the magnitudes of the rectified output voltages -Ea and -Eb are constantly monitored so that the circuit does not become saturated.

That is, monitor amplifier circuit A7. Ae amplifies the rectified output voltage.

Now, if the upper limit of the rectified output voltage when the circuit is not saturated is -E a max + -E b tnax, then A? .

A monitor amplifier circuit A7. A8 amplification degree can be selected.

Therefore, microprocessor 7 always uses I3. , check whether the input terminal of I4 is at high level.

If the level becomes high, it emits infrared light and reduces the ED current by one step. The terminals 13+I4 read high or low again, and if both are low, the intensity of the infrared emission remains unchanged.

If it is high, the current is further decreased by l steps.

In order to prevent the differential output Eo from becoming saturated in this way, the microprocessor 7 controls I3. Monitors the I4 terminal and automatically controls it.

The light output of the LED is controlled by R10, R11* R12
By turning on and off the transistors connected to RIO and R, which are connected to the anode side of the LED,
11, Since the current flowing through the resistance of RI□ is added, L
The magnitude of the current flowing through the ED changes. The LED drive circuit 8b is turned on by the output signal from the output terminal 04 of the microprocessor 7.

Turn off. Therefore, the LED blinks at a constant frequency.

The magnitude of the current flowing through the LED is changed by setting the o, , 02, and 03 terminals low, depending on the combination of 1) np) transistors in the on state.

The vertical synchronization signal detection circuit 10 generates a negative pulse at its output at the start of the vertical retrace period of the video signal. This pulse is input to the interrupt terminal of the step. The microprocessor 7 starts blinking the LED in response to this interrupt signal.

Modulate at a fixed period, and after a fixed period, the difference output E1
Read and determine the motor rotation direction for automatic distance measurement control. Microprocessor 7 outputs 05.0
．． The sensor outputs a signal to rotate the motor to move the sensor and extend the lens.

The automatic distance measurement control procedure of the apparatus according to the present invention will be described below with reference to flowcharts.

Terms, flags, etc. used in flowcharts to be described later are defined in advance.

(2)F: Forward current IA of infrared emitting LED, [B, IC, ID: IF can be switched to 4 levels. IA>IB>IC>IDe/I, in descending order
eB: Voltage level of input of differential amplifier circuit ■S: Saturation reference voltage of input voltage Meaning of status flag 5TOP=0 Indicates a state where distance measurement is not completed.

5TOP=1 Indicates distance measurement completion state.

The old N=OIF is not the minimum current 10.

MEN = 1 1 F is the minimum current ID.

MAX = OIF F is not the maximum current I^.

Gate ^X=I IF is the maximum current IA.

Leaf = O As a result of size judgment, there is no size relationship.

■=1　As a result of the size judgment, there is a size relationship.

1., I2 IF is set to one of the current values of IA, IB, IC, and IO. ．． It is shown in 2 bits of 12.

IF=I^ (I2=1.It=1)LF=IB
(12=1.It=0)IF=IC(I2=O,
It = 1) I F = I D (12 = O, I
1=0) Control flag is 7 (MSB) 5 TOP 5 MIN 5 DF 4 MAX 3 * 2 * 0 (LSB) 11 FIG. 4 is a flowchart showing the main routine of the automatic distance measurement control procedure.

Automatic distance measurement control in this program is performed in the interrupt routine, and automatic distance measurement control is not performed in the main routine.

After powering on, the program sets interrupt addresses, initializes ports, and sets status bits.

After setting the IP, enter the main routine.

The main routine is always interruptible, so
If there is an interrupt, at that point it jumps to the interrupt routine.

The interrupt timing occurs at the beginning of the vertical retrace period, and interrupts occur regularly every 1 field, that is, every 16.6 ms.

Even if an external interrupt occurs during interrupt processing due to the length of the motor on/off time interval in the interrupt routine, the external interrupt is prohibited until the interrupt processing is completed.

Therefore, in this case, since the interrupt processing is executed at the next external interrupt, the interval of automatic distance measurement control becomes 2 fields, but the automatic distance measurement control is always executed at the start of the vertical retrace period. You can start.

There are five main roles in the interrupt routine:

■Selection of IP ■Pulse emission/data of infrared emitting LED Human power ■Reduction of r and p currents to avoid saturation of the circuit when the light reception output is excessive ■Lens drive for distance measurement ■Judgment of completion of distance measurement The above role will be explained in detail below with reference to the flowchart of the interrupt routine shown in FIG.

When control is transferred from the main program to the interrupt routine, (*l) it is first determined whether it is automatic distance measurement mode or manual mode.

In manual mode, do nothing and jump to the return command.

(*2) In the automatic distance measurement mode, it is determined whether the status bit STOP (=STOP) is 1 or O, and it is determined whether distance measurement has been completed in the previous automatic distance measurement control.

(*3) If stop=1, it is determined that distance measurement has been completed in the previous control.

In order to compare the light emission for one time, a 30 ms timer is provided after the stop-○ and reset.

(*4) If stop=0, it is assumed that the focus is not yet in focus, and the IF current value is selected. In this automatic distance measurement system, the IP values are IA, IB, and IC in ascending order.
, 10, and the IF value can be changed to four levels depending on the level of the infrared input.

To select the IF value, the IF to be applied next is determined in the previous automatic distance measurement control, and its contents are stored in the memory using 2 bits of the status memory. The tp value is determined from these 2 bits, the LED is caused to emit pulse light, and data is input at a constant timing.

(*5) Next, check whether rF=■A. I
If P=I^, jump to the size discrimination program.

(*6) If ■F≠IA, check whether the input level does not exceed the saturation level.

This is the check for input≧saturation level at *6 in the flowchart. Here, in the relational expression satisfying input≧saturation level, e^≧VS>eB.

There are three possible cases where eB≧VS>eA, eA, and eB are all ≧VS, but only the case of eA and eBkVs satisfies the relational expression of input≧saturation level. If there are 2 frames remaining, it is assumed that the input is at the saturation level, and the program jumps to a size discrimination program.

(*7) If eA, eB≧VS and IF≠ro, it is determined that the input level is excessive, and control is entered to lower the IF level.

The IP stage setting after power-on is set to IP=IB.

If rF=IB is set for LED emission now, the next time the LED emits light, the level will be lowered by IF=[
It emits light as C. Similarly, now if IP=IC,
Set the status lll1n = 1, and next time, it will emit light as an IP-ID with a lower level.

Now, if you think about when the relationship of input≧saturation level actually holds, it might be when the subject is in front of you rather than at a close position, or when the reflectance of the subject itself is quite high.

In such a case, both e A + e B input levels will exceed the saturation level, and if this continues, e/
l.

Since it is impossible to determine the magnitude relationship between eB, the IP value is lowered and the magnitude relationship between eA and eB is determined again during the next infrared emission/automatic distance measurement control.

Also, either eA or eB is VS (saturation level)
If it exceeds eA≧VS>e3. or eB≧VS
>eA, and there is clearly a size relationship, so in this case there is no need to lower the IP level.

(*8) Now, we finally enter the program to determine the size of e^ and eB, eA > eB, e^ = eB.

When it is determined that e^<eB, the corresponding motor control is performed.

As a result of size discrimination, if eA>eB, it is determined that the subject is in the infinity direction, and in this automatic distance measurement control, the sensor is set to L E D 111, and during automatic focus adjustment, the lens is moved in the infinity direction. let

(Umbrella 9) In one judgment (that is, in one interrupt routine)
The motor is turned on for 25ns and immediately checks to see if the limit switch (in this case, the infinite limit switch) is turned on.

If the switch is on, the motor will stop automatically when adjusting the focus, assuming the lens is at the infinity end.

(*10) If the limit switch is off, brake the motor for 5 ms and stop the motor. Therefore, the motor can reach 25 m with one automatic distance measurement control.
The motor is turned on for 5ms and turned off for 5ms.

After the motor is turned off, the current determination shows that there is a magnitude relationship between eA and e3, and distance measurement has not yet been completed.

The status bit DF is set to 1, and a return command returns to the main routine, whereupon automatic distance measurement control is started using the next interrupt.

(*11) If e8<e3, the motor rotates in the opposite direction, and the lens is driven in the near direction (the limit switch is checked).

(*12) To e = eB (Of course, within the allowable range e
A (including the case of object e8), then I
It is checked whether P = I. If IF=■A, distance measurement is complete. If IP≠IA, then IP≠1
Check whether 0 = 1.

DF=1 indicates that there was a magnitude relationship in the previous single motion distance measurement control.

('k13) When e^=eB and DF≠1, it happens when e^=eB happens when the power is turned on, or when the reflectance of the subject is very low and both eA and eB are almost O. This is the case when it is assumed that eA = eB at the level. In this case, in order to prevent errors in judgment, the IF
=IA, apply the maximum current to the LED during the next automatic distance measurement control, and check again whether it is determined that e^=eB.

At that time, if a new magnitude relationship appears, motor control is performed in accordance with the magnitude relationship, and the lens moves. On the other hand, if there is no relationship in size, it is assumed that the focus is in focus, and each status bit is set or centered according to each state.
Set 1F=IB and return to the main routine.

(Effects of the Invention) As explained in detail above, the automatic distance measuring circuit according to the present invention is configured to monitor the output level of the rectifying circuit with a monitor circuit and control the amount of light emitted from the light emitting element, so that the automatic distance measuring circuit always maintains a good performance. You can get a good signal.

Furthermore, since the signal processing system of the light receiving element is divided into two systems, each of which extracts only the signal light frequency component, it is possible to eliminate the influence of background light.

The following characteristics can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of an automatic distance measuring circuit according to the present invention. FIG. 2 is a schematic diagram showing the positional relationship between a subject, a sensor, and a light emitting element. FIG. 3 is a detailed circuit diagram of an embodiment circuit corresponding to the block diagram. FIG. 4 is a flowchart showing the main routine. FIG. 5 is a flowchart showing the interrupt routine. la, lb... Narrowband amplification circuit 2a, 2b... AC amplification circuit Ob... Subject Sa, Sb... Sensor (light receiving element) 3a, 3b... Rectifier circuit 4... Differential amplification circuit 5... Size determination circuit 7... Microprocessor (control device) 8... Infrared LED drive circuit 9... Motor drive circuit 10... Synchronous signal detection circuit Patent applicant Kyocera Co., Ltd. Company agent Patent attorney Hisashi Inoro Ju Procedural amendment April 5, 1985 Patent application No. 239180 2o Name of invention Zi Huang Dan Xin 1 Yodo Circuit 3, Person making the amendment Relationship with the case Patent applicant 4゜Representative person 5? ! Date of positive order Self-issued 12 bmsJ
Correct to. Contents of the correction (Japanese Patent Application No. 59-239180) (11 Specification, page 9, line 12, “The differential output Eo
'' is corrected to 'the differential output EO is VT≧EO≧VT'. (2) "From line 12 to line 13 of page 17 of the specification"
That's...a check. ” to be deleted. (3) reA, eB≧VS on page 17, line 17 of the specification
``Only when reA and eB are ≧VS'' is corrected to ``only when reA and eB are ≧VS''. (4) reA, eB≧VS on page 17, line 20 of the specification
From this, the case where IF≠ID is corrected to the case where both reA and eB are ≧VS and IF≠10. (5) In the rlF setting on page 18, line 3 of the specification, "r
Correct to [F's default setting is]. (6) “Status m1n=
1" is corrected to "Status MIN = I J." (7) "Size determination" on page 19, line 6 of the specification is corrected to "size determination." (8) r25nsJ on page 19, line 15 of the specification (9
) From page 17, line 18 to line 20 of the specification, "If the switch is on... it will stop." has been changed to "If the switch is on, during automatic focus adjustment, the lens will be at the far end." It is assumed that the camera is in focus and the motor stops." α0) "..." from line 7 to line 8 on page 20 of the specification
Show that you have not done so. ``Status bit'' is corrected to ``A status bit indicating that it has not been done.'' (11) “What is now?” on page 20, line 11 of the specification
Delete. (12) “Next IP≠” on page 20, line 19 of the specification
Check whether ID=1. ” to “Then IF =I
Check whether it is D, and if IF≠■D, move on to check DF=1. ”. (13) “At that time,” on page 21, line 11 of the specification,
"If, newly," is corrected to "then, newly."that's all

Claims (3)

[Claims] (1) In an automatic distance measurement circuit that projects light from a light emitting element forward, receives the light with a light receiving element, and automatically detects the distance to the subject based on the incident angle of the reflected light, the current flowing through the light emitting element is amplitude-modulated. a light emitting element drive circuit that variably controls the supplied current;
and a second light-receiving element, first and second narrowband amplifier circuits that selectively amplify the modulation frequency components of the light incident on the first and second light-receiving elements, respectively; first and second AC amplifier circuits that further amplify the output of the second narrowband amplifier circuit; and first and second rectifier circuits that convert the outputs of the first and second AC amplifier circuits into DC voltages. a differential amplifier circuit that detects and amplifies the difference between the outputs of the first and second rectifier circuits; a monitor circuit that monitors the output level of the rectifier circuit; and a distance detection state based on the output signal of the differential amplifier circuit. a comparator for determining the amount of light emitted from the subject, which generates a control signal for controlling the light emission amount to the light emitting element drive circuit based on the output of the monitor circuit, and inputs the output from the comparator to the first and second light receiving elements. An automatic distance measuring circuit comprising a control device that generates a drive signal for moving the light receiving element so that the reflected light of the light receiving elements becomes equal. (2) The automatic distance measuring circuit according to claim 1, wherein the control device is constituted by a CPU, and the control signal and drive signal are generated by interrupt processing. (3) The automatic distance measuring circuit according to claim 1, wherein the automatic distance measuring circuit is used in a video camera, and the light emitting element is generated during a vertical retrace period of a television signal.