JPH0854231A - Distance measurement signal processor - Google Patents

Abstract

PURPOSE:To prevent the inversion phenomenon of distance measurement data value without sacrifice of the original linearity thereof. CONSTITUTION:Two output currents I1, I2 from a PSC (position detection element) 1 are converted through current/voltage conversion circuits 4, 5 into voltages V1, V2 and a reference current Ir generated from a reference current source 8 is converted through a reference voltage circuit 9 into a reference voltage Vr. A voltage conversion circuit 10 compares both voltages V2 and Vr and an output switching circuit 11 outputs the voltage V2 or Vr selectively depending on the comparison results V3. In other words, the output voltage V4 is equal to V2 when V2<Vr and equal to Vr when V2>=Vr. An operating circuit 6 executes an operation for producing a ratio I1/(I1+I2) when V2<Vr and obtaining an output including the ratio I1/(I1+I2) when V2>=Vr.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active distance measuring device used in compact cameras, video cameras and the like, and further uses a position detecting element (PSD) as a light receiving element and outputs the same. The present invention relates to a ranging signal processing device for processing a signal.

[0002]

2. Description of the Related Art FIG. 12 is a block diagram showing a configuration of a conventional distance measurement signal processing device. In the figure, reference numeral 1 is
Both ends of the output are position detecting elements, respectively connected to the first stationary light removing circuit 2 and the second stationary light removing circuit 3. The position detecting element 1 will be referred to as PSD1 hereinafter.
The outputs of the first stationary light removal circuit 2 and the second stationary light removal circuit 3 are connected to the first current-voltage conversion circuit 4 and the second current-voltage conversion circuit 5, respectively. The outputs of the current-voltage conversion circuit 4 and the second current-voltage conversion circuit 5 are both connected to the input of the arithmetic circuit 6. Further, the output of the arithmetic circuit 6 is connected to the arithmetic result output terminal 7.

Next, the operation of the apparatus shown in FIG. 12 will be described. In order to perform distance measurement (measurement of a distance to a subject), first, an infrared light projecting unit (not shown) emits infrared light toward a subject (not shown). The infrared light is reflected by the subject, and further received by the PSD 1 through a light receiving lens (not shown). At that time, in addition to the infrared light for distance measurement, unnecessary light such as infrared light contained in sunlight is constantly incident on the PSD 1. Therefore, the current component generated in the PSD 1 is obtained by adding the signal photocurrent generated by the infrared light for distance measurement to the steady photocurrent generated by the infrared light that is constantly incident. Has become. Therefore, it is necessary to remove only the stationary photocurrent. The first stationary light removing circuit 2 and the second stationary light removing circuit 3 are circuits for exactly removing the stationary photocurrent, and by the action of both the circuits 2 and 3, a distance measuring distance is measured. Two signal photocurrents (output currents) I ₁ and I ₂ are respectively extracted.

Here, the signal photocurrents I ₁ and I ₂ change over a range of about several tens of pA to several tens of μA, and since the dynamic range is too wide as it is, the subsequent signal processing is difficult. So, as a general method,
By using the first current-voltage conversion circuit 4 and the second current-voltage conversion circuit 5, the signal photocurrents I ₁ and I ₂ are converted into logarithmically compressed voltages V ₁ and V ₂ (output voltage), respectively.

FIG. 2 is a connection diagram showing an example of a configuration common to the first current-voltage conversion circuit 4 and the second current-voltage conversion circuit 5. In the figure, reference numeral 12 is an operational amplifier, the current input terminal 15 and the anode terminal of the logarithmic compression diode 13 are connected to the inverting input terminal of the operational amplifier, and the operational amplifier is connected to the non-inverting input terminal of the OP amplifier 12. Is connected to one of the reference voltage 14 (reference voltage value V _ref1 ), and the output of the OP amplifier 12 is connected to the voltage output terminal 16 and the cathode terminal of the logarithmic compression diode 13. The other side of the reference voltage 14 is GN
D.

When, for example, the above-mentioned signal light current I ₁ is input to the current input terminal 15, the following output voltage V ₁ is generated due to the diode characteristic of the logarithmic compression diode 13.
Is obtained from the voltage output terminal 16.

[0007]

[Equation 1]

In Expression 1, k is the Boltzmann constant, T is the absolute temperature, q is the electron charge, and Is is the reverse saturation current of the logarithmic compression diode 13.

Similarly, the signal photocurrent I ₂ is transferred to the current input terminal 15
When further input, the following output voltage V ₂ is obtained from the voltage output terminal 16.

[0010]

[Equation 2]

As described above, the output currents V ₁ and V obtained by logarithmically compressing the signal photocurrents I ₁ and I ₂ by using the first current-voltage conversion circuit 4 and the second current-voltage conversion circuit 5, respectively. You can get ₂ .

After that, as shown in FIG. 12, the arithmetic circuit 6 uses the output voltages V ₁ and V ₂ to perform an arithmetic operation for obtaining an output including the relational expression given by the equation (3).

[0013]

(Equation 3)

The above formula 3 is proportional to the reciprocal of the distance to the subject. Therefore, the distance to the subject can be known by outputting the data including the relational expression of Equation 3 (a signal giving information on the distance to the subject) from the calculation result output terminal 7 and processing the data with a microcomputer or the like. .

FIG. 13 is a characteristic diagram of the distance measurement data obtained by the conventional distance measurement signal processing device of FIG. In the figure, the horizontal axis of the graph represents the distance to the subject, and the vertical axis represents the value of the data including the number 3 output from the calculation result output terminal 7. In the example of this characteristic diagram, the value of the above data must monotonically decrease as the distance to the subject increases. That is, in the above-described relational expression (3), the ratio of the signal photocurrent I ₁ to the signal photocurrent I ₂ decreases as the distance to the subject increases.
PSD1 is arranged. However, actually, as is clear from FIG. 13, the data value is inverted at a certain distance. That is, the calculation output tends to monotonically decrease up to a certain distance, but after the certain distance, the calculation output tends to increase thereafter.
The cause of such reversal development will be described below.

As described above, the amount of attenuation of infrared light projected toward a subject increases as the distance to the subject increases. That is, the signal light currents I ₁ and I ₂ decrease as the distance to the subject increases. Specifically, the magnitudes of the signal photocurrents I ₁ and I ₂ are as described above.
It is reduced to about several tens of pA. In such a state, S
It is clear that the / N ratio is significantly reduced. For this reason,
As the distance to the subject increases, the signal photocurrent I ₂
The relationship that the ratio of the signal photocurrent I _{1 to} the ratio becomes small cannot be maintained. . In other words, when this relationship cannot be maintained, the phenomenon that the data value is inverted occurs. Then, when such a data inversion phenomenon occurs, as is apparent from FIG. 13, a problem occurs that data closer than the actual distance to the subject is output.

Therefore, in order to prevent such a problem, the distance measuring signal processing device shown in the block diagram of FIG. 14 has been conventionally used. In FIG. 14, reference numeral 1
Reference numerals 7 to 7 are exactly the same as those corresponding to the conventional distance measurement signal processing apparatus shown in FIG. The difference is that the input is to the second current-voltage conversion circuit 5,
The clamp circuit 34 whose output is connected to the arithmetic circuit 6
That is the point.

FIG. 15 is an example of a wiring diagram of the clamp circuit 34 shown in FIG. In the figure, reference numeral 36
Is a constant current source for generating a constant current I ₀ , one of which is connected to the power supply terminal 35 and the other is connected to the emitter terminal of the first PNP transistor 37 and the second PNP transistor 38.
Is connected to the emitter terminal and the clamp output terminal 41. The base terminal of the first PNP transistor 37 is connected to the clamp input terminal 40, and the collector terminal thereof is connected to GND. Furthermore, the second PN
The base terminal of the P-transistor 38 has a clamp voltage 39
Is connected to one (voltage value V _S), the collector terminal is connected to GND. Also, the clamp voltage 3
The other side of 9 is connected to GND.

The operation of the conventional distance measuring signal processing device shown in FIG. 14 is different from the operation of the conventional distance measuring signal processing device shown in FIG. 12 because of the operation of the clamp circuit 34 which is input to the arithmetic circuit 6. This is because one of the applied voltages does not exceed the preset voltage (V _S ). This point is clear from FIG. 15, and when the output voltage V ₂ of the clamp voltage value Vs or more is input to the clamp input terminal 40, the first PNP transistor 37 is turned off. Is.

If it is considered by applying the above equation 2 that the operation of the clamp circuit 34, that is, the voltage input to the arithmetic circuit 6 does not exceed the preset voltage, it is as follows. It can be easily determined that the signal photocurrent I ₂ corresponds to a state where the signal photocurrent I ₂ does not fall below a certain value. As described above, this means that even if the distance to the subject increases, and as a result, the signal photocurrent decreases and the S / N ratio decreases significantly, the signal increases as the distance to the subject increases. This means that the relationship that the ratio of the signal photocurrent I ₁ to the photocurrent I ₂ becomes small is maintained. Further, this means that if the distance to the subject becomes longer, the signal light current I ₂ does not become less than a certain value, but the signal light current I ₁ continues to decrease as it is, according to the equation 3, The result means that it becomes smaller rapidly. That is, the inversion phenomenon of the data of the calculation result does not occur.

[0021]

FIG. 16 shows a circuit diagram of FIG. 14 in which the one of the wiring diagram shown in FIG. 15 is used as a clamp circuit.
FIG. 11 is a characteristic diagram of the conventional distance measurement signal processing device. FIG.
As is clear from FIG. 6, the conventional distance measurement signal processing device of FIG. 14 has one major problem. That is, the ideal clamped distance measuring characteristic is such that the reverse linear development is suppressed without impairing the original linearity as shown by the characteristic indicated by the broken line 43 in FIG. 16, but it is actually obtained. The characteristic is a curve as shown by the solid line 42, and the linearity is deteriorated.
This is due to the operation of the clamp circuit 34 shown in FIG. Hereinafter, this operation will be briefly described.

In the circuit of FIG. 15, paying attention to the time when the clamp is applied, the first PNP transistor 3
7 and the second PNP transistor 38 operate as follows. First, the first PNP transistor 37
Both the first PNP transistor 37 and the second PNP transistor 38 are turned on from the state where only the first is turned on.
After the state of turning on, only the second PNP transistor 38 is turned on. At this time, the constant current source 3
6 repeats a state in which the current flows in only one PNP transistor and a state in which the current flows in both PNP transistors, which means that the first PNP transistor 37 and the second PNP transistor 38. It means that the voltage between the base and the emitter of both fluctuates.
That is, this corresponds to the fact that the voltage to be clamped actually fluctuates, and when applying the above equation (2), even if the signal photocurrent is constant, I ₂
It means that the size of fluctuates. Further, as described above, since the signal photocurrent is converted into the logarithmically compressed output voltage, the fluctuation of the voltage between the base and the emitter becomes a considerably large fluctuation when converted to the signal photocurrent I _2. Fluctuation amount of the PNP transistor 3 of the constant current source 36.
It is interlocked with the diversion ratio to 7, 38, and it will fluctuate up to 2 times). This is the cause of impaired linearity.

Therefore, in order to improve the drawbacks of the clamp circuit 34 shown in FIG. 15, the clamp circuit 34A shown in FIG. 17 is used instead of the clamp circuit 34.
In FIG. 17, reference numerals 35 to 41 are exactly the same as the corresponding reference numerals in FIG.

Reference numeral 19 is an operational amplifier, and its inverting input terminal has both emitters of the first PNP transistor 37 and the second PNP transistor 38, one terminal of the constant current source 36, and the clamp output terminal 4.
1 is connected to the non-inverting input terminal of the clamp voltage 39, and the output of the clamp voltage 39 is connected to the base of the second PNP transistor 38.

The above-described one shown in FIG. 17 utilizes the characteristics of the operational amplifier 44 to improve the drawbacks of the clamp circuit 34 shown in FIG. 15, but this also has a major drawback. It is a drawback regarding the response speed that is always a problem even in a circuit combining such operational amplifier and diode characteristics, for example, a full-wave rectification circuit. That is, the response speed of the clamp circuit 34A is determined only by the bandwidth of the operational amplifier 44 and the slew rate. When the response speed of the clamp circuit is slow, it means that there is a delay at the beginning and end of the clamping, which becomes a new error factor. Therefore, when the operational amplifier 44 is used, it is necessary to secure a considerable bandwidth and slew rate. However, various restrictions, such as a limitation of current consumption, are required especially when the ranging signal processing device is integrated into an IC. Therefore, in reality, it is impossible to realize an ideally clamped distance measuring characteristic.

The conventional distance measurement signal processing device which prevents the inversion phenomenon of the distance measurement data value can certainly prevent the reversal development itself. However, since the conventional technique uses the clamp circuit as described above, there is a problem that its operation also deteriorates the distance measurement characteristics of the portion where the linearity was originally secured. It was

The present invention has been made in order to solve the above-mentioned problems, and it is possible to prevent the inversion phenomenon of the distance measurement data value without impairing the original linearity of the distance measurement data value. A first object is to obtain a distance signal processing device. A second object of the present invention is to realize a ranging signal processing device signal that can flexibly cope with various changes in ranging characteristics.

[0028]

The invention according to claim 1 is
A position detection element that detects the projection light reflected by the subject,
Reference voltage generating means for generating a reference voltage corresponding to a reference current, current-voltage converting means for converting two output currents of the position detecting element into output voltages, one of the two output voltages and the reference. A voltage, and outputs one of the output voltages until one of the output voltages reaches the reference voltage, and outputs the reference voltage after the one of the output voltages, and the two output voltages. And a calculating means for performing a predetermined calculation for giving distance information to the subject based on the other of the above and the voltage output by the output switching means.

In the invention according to claim 2, the reference voltage generating means in the distance measuring signal processing device according to claim 1 changes the level of the reference voltage according to the distance measuring condition and outputs the variable reference voltage.

In the invention according to claim 3, the reference voltage generating means in the distance measuring signal processing device according to claim 2 changes the level of the reference voltage to an arbitrary value in accordance with the distance measuring condition. .

In the invention according to claim 4, the reference voltage generating means in the distance measuring signal processing device according to claim 2 corresponds to the distance measuring condition from a plurality of reference currents having different values. One of the selected reference currents is selected and the reference voltage corresponding to the selected reference current is generated.

According to a fifth aspect of the present invention, the output switching means has a voltage comparison circuit for comparing one of the two output voltages with the reference voltage, and a comparison result of the voltage comparison circuit is (the output voltage On the other hand, an output switching circuit which outputs the reference voltage only when the relation of ≧ (reference voltage) is given, and outputs one of the output voltages to the arithmetic means when the comparison result does not satisfy the relation. There is.

According to a sixth aspect of the present invention, there is provided a second position detecting element.
In a distance measurement signal processing device that performs a predetermined calculation process based on one output current to generate a distance measurement signal that gives a distance to a subject, a reference current generation unit that generates a reference current serving as a reference, and the two outputs. When one level of the current reaches the level of the reference current, the predetermined arithmetic processing is performed based on the other of the output currents and the reference current instead of the predetermined arithmetic processing based on the two output currents. Distance measuring signal generating means for generating a signal giving the distance information.

In the invention according to claim 7, the reference current generating means in the distance measuring signal processing device according to claim 6 varies the level of the reference current according to the distance measuring condition.

In the invention according to claim 8, claim 6 or 7
The distance measuring signal generating means in the distance measuring signal processing device described above, the comparing means for detecting whether or not the voltage level corresponding to the one output current is equal to or higher than the voltage level corresponding to the reference current; Output switching means for selectively outputting a voltage corresponding to the one output current and a voltage corresponding to the reference current according to the detection result of the means, a voltage output by the output switching means and the other output current And a calculation means for performing the predetermined calculation based on the voltage corresponding to

[0036]

[Action]

(Invention of Claim 1) The position detection element detects the projection light reflected by the subject, and outputs the detection results to the current-voltage conversion means as two output currents. The current-voltage converting means converts each of the two output currents into an output voltage,
One of the output voltages is output to the output switching means, and the other output voltage is output to the computing means. As a result, the dynamic range of the detection result of the position detection element is optimized.

On the other hand, the reference voltage generating means also generates a reference voltage corresponding to the reference current and outputs it to the output switching means.

The output switching means compares one output voltage with the reference voltage, and outputs one output voltage to the computing means when one output voltage has not reached the reference voltage. As a result, at this stage, the calculation means always executes a predetermined calculation based on the two output voltages.

On the other hand, the output current level decreases as the subject moves away, and as a result, the output voltage level increases. When the output switching means detects that one of the output voltages has reached the reference voltage, the output switching means always outputs the reference voltage in the distance measuring stage of the object located further than the distance of the object at that time. Therefore, the calculation means always executes a predetermined calculation based on the other output voltage and the reference voltage.

(Invention of Claim 2) When the reference voltage generating means changes the level of the reference voltage, the distance to the object when (one output voltage) = (reference voltage) is satisfied according to the variable amount. Shifts.

(Invention of Claim 3) When the reference voltage generating means arbitrarily changes the level of the reference voltage, up to the subject when (one output voltage) = (reference voltage) is satisfied according to the variable amount. The distance of shifts arbitrarily.

(Invention of Claim 4) The reference voltage generating means selects one of a plurality of reference currents suitable for the distance measuring condition and outputs a reference voltage corresponding thereto. As a result, the level of the reference voltage is changed for each selection, and accordingly, the distance to the subject when (one output voltage) = (reference voltage) is satisfied is changed.

(Invention of Claim 5) The voltage comparison circuit receives one output voltage and the reference voltage and compares the levels of both signals. In this case, when the subject is located relatively close, the voltage comparator circuit (one output voltage) <
The relationship of (reference voltage) is detected and output. On the other hand, one of the output voltages approaches the reference voltage as the subject moves away, and eventually the voltage comparison circuit outputs (one output voltage) ≧
The relationship of (reference voltage) is detected and output. The output switching circuit outputs one output voltage to the calculation means when the comparison result output from the voltage comparison circuit is (one output voltage) <(reference voltage), and the comparison result is (one output voltage) = (reference voltage). Voltage), the reference voltage is always output to the calculating means.

(Invention of Claim 6) The reference current generating means generates a reference current and outputs the current to the distance measuring signal generating means. The distance measurement signal generation means receives one of the output currents output by the position detection element and the reference current, and detects whether or not the output current has reached the value of the reference current. In this case, the farther the subject is, the lower both output currents are. Therefore, the distance measurement signal generating means, when one output current does not reach the reference current, that is, (one output current)>
In the case of (reference current), a signal that gives distance information is generated based on one output current and the other output current, but when it reaches, the reference current and the other output current are then generated. A signal that gives distance information is generated based on. That is, when the output current starts to decrease in response to the increase in the distance to the subject, the signal that gives the distance information using the reference current is always used after (one output current) = (reference current). Is generated.

(Invention of Claim 7) When the reference current generating means changes the level of the reference current, the distance to the object when (one output current) = (reference current) is satisfied according to the variable amount. Shifts.

(Invention of Claim 8) The comparing means is
When the result of (voltage corresponding to one output current) <(voltage corresponding to reference current) is detected and the detection result is output to the output switching means, the output switching means outputs (voltage corresponding to one output current). ) Is output to the calculation means, and as a result, the calculation means executes a predetermined calculation based on the voltage and the voltage corresponding to the other output current.

On the other hand, when the comparison means detects a result of (voltage corresponding to one output current) ≧ (voltage corresponding to reference current), the output switching means receives the detection result and ( The voltage corresponding to the reference current) is output. As a result, the calculation means will thereafter (voltage corresponding to the reference current).
Based on and ((voltage corresponding to the other output current)), a predetermined calculation is executed.

[0048]

【Example】

(First Embodiment) FIG. 1 is a block diagram showing a first embodiment of the distance measurement signal processing device according to the present invention. In the figure, reference numerals 1 to 7 are exactly the same as those used in the description of the conventional example shown in FIGS. Therefore, the arithmetic circuit 6 receives the two voltages V input to the circuit 6.
Based on ₁ and V ₄ , an operation (predetermined operation) for giving the current ratio I ₁ / (I ₁ + I ₄ ) is performed. Here, the current I ₄ is the voltage V ₄
Represents the current before current-voltage conversion, which corresponds to

Reference numeral 9 is a reference voltage generating circuit, the input of which is one of the reference current sources 8 (constant current sources) and the output of which is
It is connected to the input of the voltage comparison circuit 10 and the input of the output switching circuit 11. Also, the other side of the reference current source 8 is connected to the power supply terminal 12, the other input of the voltage comparison circuit 10 is the output of the second current-voltage conversion circuit 5, and its output is the control of the output switching circuit 11. Connected to the inputs respectively. Further, the other input of the output switching circuit 11 is also connected to the output of the second current-voltage conversion circuit 5, and its output is connected to the input of the arithmetic circuit 6.

In the above description of the conventional example, the specific connection diagram of the first current-voltage conversion circuit 4 and the second current-voltage conversion circuit 5 shown in FIG. 3 has been described. It is also a connection diagram of the reference voltage generation circuit 9. That is, the reference voltage generating circuit 9 includes the first and second circuits.
That is, the circuits exactly the same as the current-voltage conversion circuits 4 and 5 are used.

FIG. 3 shows the voltage comparison circuit 10 constituting FIG.
3, a reference numeral 17 in FIG. 3 is a comparator, the inverting input terminal of which is the Vr input terminal 19, the non-inverting input terminal of which is the V2 input terminal 18, and the output of which is the voltage comparison output terminal 20. , Each connected.

FIG. 4 shows the output switching circuit 1 constituting FIG.
4 is a connection diagram of FIG. 1, and in FIG. 4, reference numerals 21 and 22 are a first analog switch and a second analog switch, respectively, which are connected to their outputs and to the output switching terminal 26. Further, the inputs of the first and second analog switches 21 and 22 are connected to the V ₂ input terminal 24 and the Vr input terminal 25, respectively. The control input of the second analog switch 22 is
The output switching control terminal 27 is connected to the input of the inverter 23, and the output of the inverter 23 is connected to the control input of the first analog switch 21.

The operation of the distance measurement signal processing apparatus of FIG. 1 configured as described above is very simple and clear as compared with the operation using the conventional clamp circuit. That is, the voltage comparison circuit 10, and thus the comparator 17 of FIG. 3, compares the output voltage V ₂ obtained by current-voltage converting the signal light current I ₂ with the reference voltage Vr corresponding to the reference current Ir, When the output voltage V ₂ does not reach the reference voltage Vr (V ₂ <Vr), the output switching circuit 11 outputs the signal V ₃ for instructing the selection of the first analog switch 21 in FIG. As a result, the output switching circuit 11 outputs the output voltage V ₂ as the output signal V ₄ . On the other hand, when the output voltage V ₂ is higher than the reference voltage Vr (V ₂ ≧ Vr), the comparator 17 of FIG. 3 sets the second analog switch 22 of FIG. 4 to the output switching circuit 11. An output signal V ₃ for instructing selection is output, which means that the group of analog switches shown in FIG. 4 (first and second analog switches 2
1, 22) output the reference voltage Vr as the output signal V ₄ instead of the output voltage V ₂ . The above operation will be described in more detail as follows.

As described above, the reference voltage generating circuit 9 constituting FIG. 1 uses exactly the same circuits as the first current-voltage converting circuit 4 and the second current-voltage converting circuit 5 (see FIG. 2). Therefore, the reference voltage Vr is also given by the equation 4 similarly to the equations 1 and 2.

[0055]

[Equation 4]

Therefore, comparing one of the output voltages V ₂ with the reference voltage Vr in the comparator 17 of FIG. 3 as described above is equivalent to comparing the signal light current I ₂ with the reference current Ir. are doing. That is, since the subject is the level of the signal light current I ₂ to the extent that is distant decreasing, then the magnitude of the signal light current I ₂ is less than or equal to a reference current Ir (I ₁
≦ Ir) is detected, and in that case, an operation equivalent to inputting the reference current Ir to the arithmetic circuit 7 instead of the signal light current I ₂ is performed. Therefore, when the magnitude of the signal photocurrent I ₂ does not reach the reference current Ir (I ₂ >
In Ir), I ₄ = I _2, and therefore the arithmetic circuit 6 calculates data including the ratio given by the above-mentioned equation 3,
The calculation result is output as a signal that gives information on the distance to the subject, whereas when the magnitude of the signal photocurrent I ₂ is equal to or smaller than the reference current Ir (I ₂ ≦ Ir), I ₄ = Ir, The arithmetic operation performed by the arithmetic circuit 6 includes the ratio given by the following equation 5 instead of the equation 3.

[0057]

(Equation 5)

At this time, the value of the reference current Ir is constant, and one output current I ₁ continues to decrease as the distance to the subject increases, as in the case of the above-mentioned conventional example. The calculation result of becomes smaller rapidly. That is, the inversion phenomenon of the calculation result data does not occur at all.

FIG. 5 shows a characteristic diagram of the distance measurement signal processing apparatus in the first embodiment described above. As is clear from this characteristic diagram, the inversion reduction of the distance measurement data is prevented without impairing the characteristic of the portion where the linearity of the distance measurement data was originally secured. That is, the ideal clamp characteristic 43 in FIG. 16 is realized without using a clamp circuit. This is because the clamp circuit is not used and thus has no drawbacks. In the first embodiment, the comparator 17 (FIG. 3) having a sufficiently fast response speed and the first and second analog switches 21 and 22 are provided. (FIG. 4) is used. That is, the distance measurement signal processing apparatus according to this embodiment employs a circuit configuration that hardly affects the response speed.

(Second Embodiment) FIG. 6 is a block diagram showing the arrangement of a distance measurement signal processing apparatus according to the second embodiment of the present invention. The distance measurement signal processing device in this case corresponds to a modification of the first embodiment in FIG. That is, in this case, the arrangement of the (first stationary light removing circuit 2, the first current-voltage converting circuit 4) and the (second stationary light removing circuit 3, the second current-voltage converting circuit 5) is shown in FIG. Since the relationship is set to be completely opposite to the case of 1, the other components (1, 6
~ 12) are the same as in the case of FIG. However, in this second embodiment, the arithmetic circuit 6
Is based on the output voltage V ₂ and the voltage V ₄ on one side, I ₂ /
The calculation (predetermined calculation) including the ratio given by (I ₂ + I ₄ ) is performed, and the portion including the voltage comparison circuit 10 and the output switching circuit 11 outputs when I ₁ > Ir and V ₁ <Vr. While the voltage V ₁ is output to the arithmetic circuit 6 as the output signal V ₄ , the reference voltage Vr is output as the output signal V ₄ when I ₁ ≦ Ir, and therefore V ₁ ≧ Vr.

Therefore, the arithmetic circuit 6 has one output current I
_{When 1} does not reach the reference voltage Ir (I ₁ > Ir, V
₁ <Vr),

[0062]

(Equation 6)

Calculation for obtaining an output (a signal giving information on the distance to the object) including the relational expression given by
After one output current I ₁ reaches the reference current Ir (I ₁ ≤
Ir, V ₁ ≧ Vr) is

[0064]

(Equation 7)

A calculation is performed to obtain an output (a signal that gives information on the distance to the object) including the relational expression given by.

FIG. 7 is a characteristic diagram of the distance measurement data obtained by the distance measurement signal processing device of FIG. In this case,
The other signal light current I ₁ as the subject moves away
Since one ratio of the signal light current I ₂ of the increases for the characteristics of the distance measurement data obtained is a relationship which is reversed from that (FIG. 5) in the case of the first embodiment. That is, as shown in FIG. 7, the calculation output increases as the distance increases. Even in this case, the original directness (however, the inclination is positive)
The inversion phenomenon can be prevented without impairing the above.

As described above in the first and second embodiments, whichever of the _two output currents I ₁ and I ₂ of the PSD ₁ is used as a comparison target with the reference current Ir, the present invention can be used. The first purpose can be achieved. In addition, in both of the embodiments, a circuit which can be relatively easily configured, that is, the reference current source 8, the reference voltage generation circuit 9, the voltage comparison circuit 10 and the output switching circuit 11 is newly added to the conventional components (2 to 6). It is possible to realize the first object with a good and simple structure and while maintaining high response speed.

(Third Embodiment) FIG. 8 is a block diagram showing the arrangement of a distance measurement signal processing apparatus according to the third embodiment of the present invention. This embodiment is different from the first embodiment in FIG. 1 in that the reference current source 8 in FIG.
Is being replaced. The reference voltage changing circuit 28 is controlled by the control logic 29 and the microcomputer 30. The control logic 29 is specifically configured by a serial / parallel converter or the like. With such a configuration, the value of the reference voltage Vr can be changed according to the change of the distance measuring condition. The purpose or advantage of such a configuration will be described below.

For example, in the case of a distance measuring device for a camera,
The range-finding characteristics depend on various factors such as the optical system used in the autofocus device, the light-emitting element used in the infrared projector, the light-receiving sensor that receives the reflected light from the subject, and the arrangement of these parts. It depends on
In other words, the situation in which the inversion phenomenon of the distance measurement data occurs is not uniform and changes depending on these conditions (distance measurement conditions). Therefore, it is necessary to effectively prevent the inversion phenomenon each time those conditions change. For that purpose, it is necessary to change the value of the reference voltage Vr one by one according to those conditions. However, in general, the distance measurement signal processing circuit is I
The change is not easy because it has been converted to C. Therefore, in the present invention, some reference voltage values Vr are prepared in advance, and the reference voltage value Vr is controlled by the external control of the IC.
By making it changeable, it is possible to flexibly deal with the case where the above conditions are changed.

In FIG. 8, the reference voltage changing circuit 28 is
Reference current source 28a and switch circuit 28b connected in series
The reference current generator 28 has a configuration in which five reference current generators are connected in parallel, and the reference currents Ir generated by the reference current sources 28a are set to different values.

Assuming that the distance measuring condition is changed, the microcomputer 30 and the control logic 29 select the reference current source 28a capable of appropriately responding to the new distance measuring condition in response to the change command input. Select signal (not shown)
Is generated and the signal is output to the reference voltage changing circuit 28. As a result, only the newly selected switch 28b is turned on, and the corresponding reference current source 28a outputs a different reference current Ir to the reference voltage generating circuit 9. As a result, the reference voltage generation circuit 9 outputs the reference voltage Vr having a different voltage value corresponding to the new distance measurement condition, and the characteristic of the distance measurement data value becomes linear according to the increase or decrease of the reference voltage Vr. Shift while keeping.

Here, FIG. 9 is obtained by using the distance measuring signal processing device of FIG. 8, that is, the reference current Ir or the reference voltage V.
It is a characteristic diagram of the distance measurement data when r is variable. In the figure, the characteristic drawn by the solid line 31 is shown in FIG.
The characteristic corresponding to the characteristic (FIG. 5) obtained in the case of, and an example obtained when the reference current Ir having a larger value than the reference current Ir at that time is selected is the characteristic drawn by the broken line 32. Is. Thus, as the reference current Ir is increased, the characteristic shifts to the left in FIG. On the other hand, an example when the reference current Ir having a smaller value is selected is the characteristic drawn by the broken line 33. Therefore,
The characteristic shifts to the right in FIG. 9 as the reference current Ir is reduced.

As described above, in the third embodiment, by increasing or decreasing the reference current Ir, and hence the reference voltage Vr, among a plurality of values prepared in advance, the original directness of the distance measurement data value can be obtained. It is possible to change (shift) the distance measurement characteristics in accordance with the change of the distance measurement condition while preventing the occurrence of the reversal phenomenon without deteriorating the above.

(Fourth Embodiment) In the third embodiment of FIG. 8, one of a plurality of reference current Ir values prepared in advance is used.
By changing the control to one value, it is possible to easily deal with the case where the distance measuring condition or the distance measuring characteristic changes, but instead of this, the reference current Ir or the reference voltage V
It is also possible to change the value of r to an arbitrary value so as to have further flexibility. Among them, the former case is embodied in the fourth embodiment described here. That is, FIG. 10 is a connection diagram showing a configuration of only a main part in the fourth embodiment in which the reference current Ir can be arbitrarily changed. Therefore, other parts are the same as those in FIG.

In FIG. 10, the variable constant current source 8A and the reference voltage generating circuit 9 constitute a reference voltage generating section for generating and outputting the reference voltage Vr '. In this case, the value of the reference voltage Vr 'is changed to an arbitrary value by changing the output current Ir' of the variable constant current source 8A to an arbitrary value.
As a result, the characteristics of the distance measurement data are arbitrarily changed (shifted) while maintaining the original linearity and the occurrence of the inversion phenomenon. As a result, it becomes possible to flexibly deal with changes in various distance measurement conditions.

(Fifth Embodiment) FIG. 11 is a connection diagram of a reference voltage generating circuit 9A in the fifth embodiment. In the fifth embodiment, the reference current Ir itself does not change (constant value).
Therefore, the reference voltage Vr 'can be arbitrarily changed in the reference voltage generating circuit to achieve the second object of the present invention. Therefore, in this embodiment, the variable constant voltage source 14A is provided in the reference voltage generating circuit 9A. As a result, the output reference voltage Vr 'is also changed to an arbitrary value, and the characteristic of the distance measurement data is arbitrarily changed as in the case of the fourth embodiment.

In the first to fifth embodiments described above, the first
And the second current-voltage conversion circuits 4 and 5 and the reference voltage generation circuit 9 shown in FIG. 3 (in the fifth embodiment shown in FIG. 11), and the voltage comparison circuit 10 shown in FIG. 4 has been described as an example of the output switching circuit 11 shown in FIG. 4, but the present invention is not limited to these circuits.

[0078]

【The invention's effect】

(Invention of Claim 1) In the present invention, since the reference voltage is always one of the voltages to be used for the predetermined calculation after the comparison voltage reaches the reference voltage, the range data value is originally It is possible to prevent the inversion phenomenon of the distance measurement data value without damaging the straight line. Therefore, a device suitable for a distance measurement signal processing device such as a camera can be realized.

(Invention of Claim 2) In this invention,
Since the level of the reference voltage can be changed, it is possible to easily deal with the case where the distance measuring condition is changed. That is, it is possible to change the step of setting the reference voltage to one voltage that should be used for a predetermined calculation according to the change of the distance measurement condition, and to measure the distance measurement data value with excellent linearity without inversion phenomenon. It can be realized despite changing conditions. In this way, the generation and output of the reference voltage can be externally controlled by the parts other than the core part of the device, such as the calculation part and the output switching part, and the versatility of the distance measurement signal processing device can be improved. it can. In particular, the core of the device is
When the C-type is used, control from the outside of the IC becomes possible, and the versatility can be significantly increased.

(Invention of Claim 3) In this invention,
Since the level of the reference voltage can be changed arbitrarily, it is possible to obtain distance measurement data values with excellent linearity without any reversal phenomenon even under arbitrary distance measurement conditions, and flexibility for changes in distance measurement conditions. Can be increased. Therefore, the present invention can dramatically improve versatility as a distance measurement signal processing device.

(Invention of Claim 4) In this invention,
Since the reference voltage can be changed to one of a plurality of values easily prepared in advance, the optimum reference voltage can be generated according to the change of the distance measurement condition. Therefore, it is possible to easily cope with a change in the distance measuring condition.

(Invention of Claim 5) In this invention,
In addition to the position detecting element, the current-voltage converting means, and the calculating means which are common elements to the conventional device, a voltage comparing circuit, an output switching circuit, and a reference voltage generating means can be newly provided, so that the comparison can be made. With a relatively simple structure, it is possible to realize a distance measurement signal processing device having a distance measurement data value that is excellent in linearity and has no inversion phenomenon. Moreover, since it is not necessary to use the clamp circuit at all as in the prior art, it is possible to avoid the drawbacks that accompany it and to realize a distance measurement signal processing device having excellent response characteristics.

(Invention of Claim 6) In this invention,
After the current that is being compared reaches the reference current, a predetermined calculation is always performed based on the reference current and the other output current, so the original straight line of the distance measurement data value is not impaired. The inversion phenomenon of the distance data value can be prevented.

(Invention of Claim 7) In this invention,
Since the level of the reference current can be changed, it is possible to easily respond even if the distance measuring conditions change, and even if the distance measuring conditions change the distance measuring data values with excellent linearity without inversion phenomenon. It can be realized regardless. In this way, the generation and output of the reference voltage can be controlled externally, and the versatility of the distance measurement signal processing device can be enhanced. In particular, when the core part of the device is integrated into an IC, control from the outside of the IC becomes possible, and the distance measuring signal processing device with high versatility can be configured.

(Invention of Claim 8) In the present invention,
Since it can be realized by the calculating means, the comparing means, the output switching means and the reference current generating means, it has a relatively simple structure and has a distance measurement data value excellent in linearity without inversion phenomenon A fast ranging signal processing device can be achieved.

[Brief description of drawings]

FIG. 1 is a block diagram of a distance measurement signal processing device according to a first embodiment of the present invention.

FIG. 2 is a wiring diagram of first and second current-voltage conversion circuits or reference voltage generation circuits that constitute the distance measurement signal processing device of the present invention and the conventional distance measurement signal processing device.

FIG. 3 is a connection diagram of a voltage comparison circuit which constitutes the distance measurement signal processing device of the present invention.

FIG. 4 is a wiring diagram of an output switching circuit that constitutes the distance measurement signal processing device of the present invention.

FIG. 5 is a characteristic diagram of the distance measurement signal processing device according to the first embodiment of the present invention.

FIG. 6 is a block diagram of a distance measurement signal processing device according to a second embodiment of the present invention.

FIG. 7 is a characteristic diagram of a distance measurement signal processing device according to a second embodiment of the present invention.

FIG. 8 is a block diagram of a distance measurement signal processing device according to a third embodiment of the present invention.

FIG. 9 is a characteristic diagram of a distance measurement signal processing device according to a third embodiment of the present invention.

FIG. 10 is a connection diagram of a reference voltage generator in a distance measurement signal processing device according to a fourth embodiment of the present invention.

FIG. 11 is a wiring diagram of a reference voltage generation unit in a distance measurement signal processing device according to a fifth embodiment of the present invention.

FIG. 12 is a first block diagram of a conventional distance measurement signal processing device.

FIG. 13 is a first characteristic diagram of a conventional distance measurement signal processing device.

FIG. 14 is a second block diagram of a conventional distance measurement signal processing device.

FIG. 15 is a first connection diagram of a clamp circuit constituting a conventional distance measurement signal processing device.

FIG. 16 is a second characteristic diagram of the conventional distance measurement signal processing device.

FIG. 17 is a second connection diagram of a clamp circuit that constitutes a conventional distance measurement signal processing device.

[Explanation of symbols]

1 PSD, 4 1st current-voltage conversion circuit, 5 2nd current-voltage conversion circuit, 6 arithmetic circuit, 8 reference current source, 9
Reference voltage generating circuit, 10 voltage comparison circuit, 11 output switching circuit, 13 reference voltage changing circuit, I ₁ , I ₂ output current, V ₁ , V ₂ output voltage, Ir reference current, Vr reference voltage.

Claims (8)

[Claims] 1. A position detecting element for detecting projection light reflected by an object, a reference voltage generating means for generating a reference voltage corresponding to a reference current, and two output currents of the position detecting element, respectively. Current-voltage conversion means for converting into voltage, comparing one of the two output voltages with the reference voltage, and outputs one of the output voltages until one of the output voltages reaches the reference voltage, After the arrival, an output switching unit that outputs the reference voltage, and an operation unit that performs a predetermined operation that gives distance information to the subject based on the other of the two output voltages and the voltage output by the output switching unit. And a distance measurement signal processing device provided with. 2. The distance measurement signal processing device according to claim 1, wherein the reference voltage generation means varies and outputs the level of the reference voltage according to the distance measurement condition. 3. The distance measurement signal processing device according to claim 2, wherein the reference voltage generation means varies the level of the reference voltage to an arbitrary value in accordance with the distance measurement condition. 4. The reference voltage generating means selects one corresponding to the distance measuring condition from a plurality of reference currents having different values, and the reference voltage corresponding to the selected reference current. 3. The distance measurement signal processing device according to claim 2, wherein 5. The output switching means includes a voltage comparison circuit that compares one of the two output voltages with the reference voltage, and a comparison result of the voltage comparison circuit is (one of the output voltages).
An output switching circuit that outputs the reference voltage only when a relation of ≧ (the reference voltage) is given, and outputs one of the output voltages to the arithmetic means when the comparison result does not satisfy the relation. Item 5. The distance measurement signal processing device according to item 3 or 4. 6. A reference for generating a reference current as a reference in a distance measuring signal processing device for generating a signal for providing distance information to a subject by performing a predetermined calculation process based on two output currents of a position detection element. When the level of one of the two output currents reaches the level of the reference current, the current generating means replaces the predetermined arithmetic processing based on the two output currents with the other of the output currents and the reference current. Distance measuring signal processing means for generating the signal giving the distance information by performing the predetermined arithmetic processing based on the distance measuring signal processing device. 7. The reference current generating means varies the level of the reference current according to a distance measuring condition.
The distance measurement signal processing device according to claim 6. 8. The distance measurement signal processing device according to claim 6, wherein the distance measurement signal generation means has a voltage level corresponding to the one output current equal to or higher than a voltage level corresponding to the reference current. Comparing means for detecting whether or not, output switching means for selectively outputting a voltage corresponding to the one output current and a voltage corresponding to the reference current according to the detection result of the comparing means, A distance measuring signal processing device comprising: a calculating unit that performs the predetermined calculation based on a voltage output by the output switching unit and a voltage corresponding to the other output current.