JP2586932B2 - Distance measurement processor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a distance measurement arithmetic processing device,
In order to measure a distance to a subject based on the principle of triangulation, when light is incident on a light receiving surface formed of a resistive layer formed between electrodes having a predetermined interval, a first light corresponding to the incident position of the light is received. And the second signal is output by receiving light reflected by the subject and projected from light projecting means including a light emitting element and a light projecting lens by a light receiving element output from the electrode. The present invention relates to a distance measurement processing device that performs calculation processing on first and second signals.

[Conventional technology]

Conventionally, various techniques have been proposed for a distance measuring technique for measuring a distance to a subject. Among them, based on the principle of triangulation, light (pulse light) from a light projecting unit is projected on the subject, and Receiving the reflected light at the light receiving element,
The so-called active triangulation method is widely known. As a typical conventional example of the active type described above,
Japanese Patent Application Laid-Open No. 54-121164 discloses a "photometric circuit of a distance measuring device" (hereinafter referred to as a "first conventional example"). There is an "automatic distance measuring device for a camera" described in JP-A-87543 (hereinafter referred to as "second conventional example"). In particular, in the second conventional example, a PSD (Positio) which is a semiconductor optical position detecting element is used as a light receiving element.
n Sensitive Device).

[Problems to be solved by the invention]

In the first conventional example, a plurality of light receiving elements are arranged corresponding to an image forming position of reflected light generated according to a distance of a distance measuring object due to a difference in parallax from light projecting means.
In addition to the problem that continuous distance cannot be detected and the resolution is low, there is a problem that a series of processing circuits are required by the same number as the number of light receiving elements, and the configuration becomes very complicated.

In order to solve these problems, the second conventional example uses the above-mentioned PSD which is a semiconductor element. And PSD
Is configured as follows. That is, as shown in FIG. 8, for example, the light-receiving side is formed of a semiconductor having a three-layer structure of a resistance layer 70 made of a P-type semiconductor, a high-resistance base layer 71 made of silicon, and a layer 72 made of an n-type semiconductor. The P-type resistance layer 70 is provided with electrodes 73 and 74 on both sides thereof, and the layer 72 is provided with a common electrode 75.

 The operation of the PSD thus configured is as follows.

The distance between the electrodes 73 and 74 is L, the resistance of the layer 70 between them is Rs, and the incident position of the incident light (spot light) 76 and the electrode
Suppose the general case where the distance to 73 is X and the resistance of layer 70 between them is Rx. The charge generated at the light incident position of the layer 70 flows through the resistive layer 70 as a photocurrent proportional to the incident energy of light. This current is
The current is output to the electrodes 73 and 74 in such a manner that the current is shunted to the electrodes 73 and 74 in inverse proportion to the resistances of the electrodes 73 and 74.

Here, the photocurrent generated by the incident light 76 is ΔI0,
Assuming that the currents output from the electrodes 73 and 74 are ΔI1 and ΔI2, respectively, the following relationship is established.

ΔI0 = ΔI1 + ΔI2 (1) ΔI1 = ΔI0 × (Rs−Rx) / Rs (2) ΔI2 = ΔI0 × Rx / Rs (3) Since the resistance layer 70 is uniform, its length and resistance are proportional. Taking this into account, equations (1) and (2) can be expressed as follows.

ΔI1 = ΔI0 × (L−X) / L (4) ΔI2 = ΔI0 × X / L (5) As can be seen from the equations (4) and (5), the currents ΔI1 and ΔI2 are the light amounts of the incident light 76. Will be proportional to
Therefore, when these current ratios y are obtained, y = ΔI2 / ΔI1 = X / (L−X) (6), and the PSD length L is independent of the light quantity of the incident light 76, that is, the photocurrent ΔI0. Incident position X (corresponding to subject distance,
It will be understood that it is determined only by the details described later). In other words, the current ratio y is used to remove the dependence on the light amount. However, from equation (6), the incident light 76 is PSD
, When X = L / 2, y =
1 and y ≒ 1 when there is no incident light 76 at all. That is, there is a problem that it is impossible to distinguish between ΔI0 = 0 and X = L / 2. Therefore, conventionally, this problem has been eliminated by configuring a light receiving optical system as shown in FIG.

That is, FIG. 9 shows the arrangement of the light receiving lens 77 and the PSD 78. As is clear from this figure, the light receiving lens
The optical axis O of 77 is arranged so as to coincide with the center line C of the PSD 78. In this case, one electrode 74 is arranged farthest from the light beam of the light emitting optical axis (not shown) of the light emitting element with respect to the center line C, and the other electrode 73 is arranged so as to be closest to the light emitting optical axis. It has become. With such an arrangement, the reflected light from the subject within the range that can be measured is always incident on one half (the right half in the figure) of the PSD 78, and the reflected light 80 from the position ∞ is located on the optical axis O. That is, the incident positions of the reflected lights 79 to 81 are always between the center line C and the electrode 74. Considering the reflected light 80 at infinity, the incident position is at the position of the center line C and does not enter the left half of the figure.

In other words, by configuring the light receiving optical system in this manner, the object distance is uniquely determined to be at the ∞ position when the current ratio y = 1 regardless of whether or not the reflected light 80 from the ∞ position is incident. There is no problem at all.

In other words, the problem was solved by actively using only half of the PSD78.

However, using only half of the PSD78 in this way is not only economically disadvantageous, but also
And the unused light-receiving surface (left half in the figure) that does not contribute to the operation, the noise generated in this part is added, and the S / N ratio between the disturbance light and the incident light 79 to 81 is increased.
A new problem of degrading the ratio has arisen.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to reduce the element length of a light receiving element determined by the distance between electrodes while maintaining a conventional characteristic with a simple configuration, thereby reducing cost. , Space saving and improvement of S / N ratio.
An object of the present invention is to provide a distance measurement arithmetic processing device capable of extending a distance measurement range while having a shorter element length than a conventional device.

[Means for solving the problem]

According to the present invention, in order to achieve the above-described object, in order to measure a distance to a subject based on the principle of triangulation, light is applied to a light receiving surface including a resistive layer formed between electrodes having a predetermined interval. When the light enters, first and second signals corresponding to the incident position of the light are respectively projected by light receiving elements output from the electrodes from light projecting means including a light emitting element and a light projecting lens and reflected by the object. In the distance measurement processing device for calculating the first and second signals output by receiving the reflected light, the ratio signal is calculated by calculating the ratio between the first signal and the second signal. Output ratio calculating means, and the magnitude of the ratio is substantially the same in the specific light receiving state where the incident position is a specific position on the light receiving surface and in the non-light receiving state where the reflected light is hardly incident. Have the property of being equal A first comparing means for receiving the ratio signal, comparing the magnitude of the ratio with a predetermined range of magnitude, and outputting an indefinite signal when the magnitude is within the range; A second unit for receiving at least one of the first and second signals, comparing the magnitude of the signal with a predetermined reference value, and outputting a finite signal when the signal exceeds the reference value; The comparison means, when receiving the indefinite signal, when receiving the finite signal, performs a finite determination that the subject is at a finite distance, and when not receiving the finite signal, The infinite determination corresponding to the non-light receiving state is performed, and when the indefinite signal is not received, a state determination unit that performs the finite determination regardless of the presence or absence of the finite signal, and the state determination unit performs the finite determination. When I went A signal selecting means for outputting subject distance data calculated based on the ratio signal of the output ratio calculating means and outputting predetermined infinite distance data when the infinity determination is made. It is.

[Action]

The first comparing means of the ranging arithmetic processing device configured as described above receives the ratio signal obtained based on the output of the light receiving element, and determines the magnitude of the ratio to a predetermined magnitude. The second comparing means receives one of the signals from the light receiving elements and outputs an indefinite signal when the signal is within the range as compared with the range. And outputs a finite signal when the value exceeds the reference value.

Then, the state determination means performs the finite determination when receiving the indefinite signal, receives the finite signal, performs the infinite determination when not receiving the finite signal, but performs the infinite determination when not receiving the indefinite signal. Performs a finite decision irrespective of the presence or absence of a finite signal.

Finally, the signal selection means outputs the subject distance data as measured when the state determination means makes the finite determination, but instead of outputting the subject distance data when making the infinite determination, To output predetermined infinity distance data.

As a result, there is a problem when the entire surface of the light receiving element is used as a light receiving surface. The case where reflected light is not incident at all and the case where reflected light is incident on a specific position (usually the center position) are distinguished. The problem of being unable to do so can be reliably solved.

Therefore, in order to secure the same distance measurement range as in the past, the length of the light receiving portion of the light receiving element can be made shorter than in the conventional case. In the case where the / N ratio is realized, but the size is not shortened, the resolution is improved and the distance measurement range is expanded.

〔Example〕

Hereinafter, an embodiment of the present invention will be specifically described with reference to the accompanying drawings.

FIG. 1 is a circuit diagram showing an entire configuration of a distance measurement processing device according to the present invention.

In FIG. 1, reference numeral 1 denotes an input terminal for receiving a light current Iil as a first signal from the PSD, 2 denotes a steady extraction transistor whose collector is connected to the input terminal 1 and whose emitter is grounded. A memory capacitor having one end grounded and the other end connected to the base of the transistor 2;
Is a sampling amplifier having a non-inverting terminal connected to the input terminal 1, receiving the correction voltage V1 at the inverting input terminal, and outputting the sampling voltage Ve1, 5 receiving the sampling voltage Ve1 at the source, and a switching signal (S1) at the gate. A field-effect transistor for a switch (hereinafter referred to as "FET") having a drain connected to the base of the transistor 2, an input transistor 6 having a base connected to the input terminal 1 and an emitter grounded, Reference numeral 7 denotes a first transistor for a current mirror whose emitter is connected to the power supply Vcc and whose base and collector are connected to the collector of the transistor 6, and reference numeral 8 denotes a transistor whose emitter is connected to the power supply Vcc and whose base is the transistor 7.
A current mirror second transistor connected to the base of the transistor 8, a logarithmic conversion diode 9 having an anode grounded and a cathode connected to the collector of the transistor 8, and 10 having a collector of the transistor 8 connected to a non-inverting input terminal. A current / voltage conversion amplifier that is connected and has an inverted input terminal connected to the output terminal and outputs a position voltage (Vo1) from the output terminal. The first input circuit 11 is configured as described above.

Reference numeral 12 denotes a second input circuit, which is configured substantially the same as the first input circuit, so that only the correspondence will be described. 13 is the second
An input terminal for receiving a photocurrent Ii2 as a signal, a transistor 14 for steady light extraction, a memory capacitor 15, a sampling amplifier 16 for receiving the correction voltage V2 and outputting a voltage Ve2, and 17 for the sampling voltage Ve2 And switch signal (S
2) FET for switch to receive, 18 for input transistor, 19 and 20 for first and second transistors for current mirror, 21 for logarithmic conversion diode, 22 for outputting position voltage (Vo2) This is an amplifier for current / voltage conversion.

Numeral 23 denotes a differential as output ratio calculating means for receiving the position voltages (Vo1) and (Vo2) and equivalently outputting a specific voltage (Vr) as a ratio signal corresponding to the ratio between the light currents Ii1 and Ii2. The arithmetic circuit 24 is a sample-and-hold circuit which receives the specific voltage (Vr) and temporarily stores it.

Portions denoted by reference numerals 25 to 29 are main parts of the present invention. Among them, 25 receives the hold signal (Vs) from the sample and hold circuit 24 and a determination signal (DS) described later, and Signal selection circuit to select, 26 is signal selection circuit 25
An output terminal for receiving the distance measurement signal (Vo3) from the controller and outputting the same to the next stage (not shown). The output terminal 27 receives the specific voltage (Vr) and compares it with a predetermined voltage range V3 to V4. , A window comparator as first comparing means for outputting an H-level undefined signal (W), and 28 is a position voltage (Vo2)
In response to this, it is compared with a predetermined reference value, a reference value voltage V5, and outputs an H-level infinite signal (Cn) when the voltage falls below the reference voltage V5 and an L-level finite signal (Ci) when the voltage exceeds the reference voltage V5. A comparator 29 serving as second comparing means receives the indefinite signal (W) and the finite signal (Cn) or the infinite signal (Ci) and outputs a logical product of them as a determination signal (DS). An AND gate as a means.

FIG. 2 is a schematic diagram showing an active distance measuring optical system based on the principle of triangulation. In FIG. 2, reference numeral 30 denotes a light projecting optical axis, 31 denotes a reference position, and 32 denotes a reference position 31 on the light projecting optical axis 30.
A light-emitting diode 33 is disposed behind the light-projection lens 32 on the light-projection optical axis 30 and emits infrared light as a light-emitting element (hereinafter abbreviated as “LED”). Do)
Thus, the LED 33 and the light projecting lens 32 constitute light projecting means. 34 is a light beam projected along the light projection optical axis 30, 35 is a subject located at a subject distance D on the light projection optical axis 30, and 36 is the light beam 34 reflected by the subject 35 The reflected light, 37 is a light receiving optical axis separated from the light projecting optical axis 30 by the base line length S, 38 is a light receiving lens having a focal length f arranged at the reference position 31 on the light receiving optical axis 37, and 39 is a light receiving lens. Light receiving axis 37
Reflected light from infinity (∞) toward the light receiving lens 38 going upward, 40 is a PSD as a light receiving element constructed similarly to the PSD shown in FIG. The light receiving optical axis 37 is provided so as to be substantially orthogonal.

FIG. 3 is an enlarged view showing the PSD and its periphery in detail, and the same parts as those in FIG. 2 are denoted by the same reference numerals.

In FIG. 3, reference numeral 41 denotes a light receiving surface formed of a resistive layer, and reference numerals 42 and 43 are provided at both ends of the light receiving surface.
The electrode L that outputs a current corresponding to the element length corresponds to the distance between the electrodes 42 and 43. 36 is the above, but the reflected light is incident on the position separated by X from the light receiving optical axis 37, and 44 is L
This is the reflected light from the closest position that enters the position separated by a distance.

4 to 7 are waveform diagrams showing the operation. FIG. 4 is an operation waveform of the window comparator 27, FIG. 5 is an operation waveform of the comparator 28, and FIGS. 4 shows operation waveforms.

In the graph of FIG. 4, the vertical axis represents the specific voltage Vr, the horizontal axis represents the incident position X, and the magnitude relationship of the voltages is V3 ≦ Vc ≦ V4.
When 0 <V3, 45 is a characteristic curve.

In FIG. 5, the vertical axis indicates the position voltage Vo in the graph.
2. The horizontal axis is the incident position X, and 46 is a characteristic curve.

Here, prior to describing the operation of the present embodiment, the principle of distance measurement will be described. From the distance measuring optical system shown in FIG.

X / S = f / D (7) By substituting equation (7) into equation (6) and rearranging, D = [(1−y) / y] · (S · f / L) (8) The subject distance D is obtained from the current ratio y.

Next, the operation will be described. However, the first and second input circuits
Since the operations 11 and 12 are the same, the first input circuit 11 will be described as a representative. Now, the FET 5 is turned on, and the LED 33 is turned off. The photocurrents from the electrodes 42 and 43 due to natural light (stationary light) are denoted by I1 and I2, respectively. Therefore, in this state, the photocurrent Ii1 input to the input terminal 1 is Ii1 = I1 (Ii2 = I1
2).

The photocurrent Ii1 = I1 becomes a sampling voltage Ve1 via the amplifier 4, flows into the memory capacitor 3 via the FET 5, and is stored as the base-emitter voltage Vbe of the transistor 2.

Next, the FET 5 is turned off, and the LED 33 is caused to emit pulse light. The light beam 34 is reflected by the subject 35 to become reflected light 36, and is incident on the light receiving surface 41 of the PSD 40 at the incident position X through the light receiving lens 38. Assuming that the photocurrent generated at this time is ΔI1, Ii1 = I1 + ΔI1 (9) However, the base potential of the transistor 2 is held by the memory capacitor 3 in a state before the FET 5 is turned off. Only the photocurrent I1 of natural light flows, so the photocurrent ΔI1 due to the reflected light 36 flows into the base of the transistor 6. Thus, the photocurrent ΔI1 is extracted from the photocurrent Ii1.

The current amplified by the transistor 6 by a predetermined amount flows into the diode 9 via the transistors 7 and 8 of the current mirror circuit, and is converted into a voltage and logarithmically compressed. The amplifier 10 outputs this voltage as a position voltage (Vo1). Then, since logarithmic compression (conversion) is performed, the position voltages (Vo1) and (Vo2) are expressed as Vo1 = KＫlnΔI1 (10) Vo2 = K ・ lnΔI2 (11) The arithmetic circuit 23 calculates the two position voltages (Vo
1) and (Vo2), calculate the difference, and output the specific voltage (Vr).

Vr = Vo2−Vo1 = K · ln (ΔI2 / ΔI1) (12) ∴Vr = K · ln (y) That is, the specific voltage (Vr) corresponding to the current ratio y is obtained. Then, the sample and hold circuit 24 temporarily stores the specific voltage (Vr).

By the way, as described in the section of the prior art, from the equation (6), in this embodiment, the PSD 40 becomes y = 1 at X = L / 2 as the specific position, and the reflected light 36 and 39,44 It has the characteristic that y ≒ 1 even when there is no light, and it corresponds to the specific light receiving state and the non-light receiving state, respectively.

If the specific voltage (Vr) corresponding to y = 1 and y ≒ 1 is Vc, as shown in FIG. 4, V4 and V3 fall within a voltage range including the variation in yV1 around Vc. Set. Therefore, when the specific voltage Vr is within this voltage range V3 to V4, in other words, the range P1 where the characteristic curve 45 given by the equation (12) or (13) intersects the straight line of Vr = V3, Vr = V4 ~ P
In 2, the indefinite signal (W) of the window comparator 27 is H
Invert to level. That is, when the indefinite signal (W) is at the H level, it indicates that it is not possible to distinguish between the specific light receiving state and the non-light receiving state.

Further, the reference voltage V5 of the comparator 28 is set to a value corresponding to the amount of the photocurrent ΔI0 (excluding ΔI0 = 0) which can be regarded as a position at almost infinity. That is, as can be seen from equation (5), the photocurrent ΔI2 corresponding to the position voltage (Vo2)
Depends on the magnitude of the above ΔI0, and by making this amount correspond to that, when reflected light is incident on any position of X = 0 to L, as shown in FIG. The characteristic curve 46 given by the equation and the equation (11) must be equal to the reference voltage.
In this case, the comparator 28 outputs an L level finite signal (Cn). However, when almost no reflected light is incident, the reference voltage V5 is exceeded and an H level infinite signal (Ci) is output. Is output. Therefore, in other words, when an L-level finite signal (Cn) is output, it indicates that reflected light is incident on any of X = 0 to L of the PSD 40. As can be seen from equation (5), when the incident light 39 from the 入射 position is incident, ΔI2 ≒ 0,
Such a state is limited only when X ≒ 0, that is, X =
It is clearly different from L / 2, and in fact, the reachable distance of the projection beam 34 by the LED 33 is about 10 m.
The reflected light 39 from the position does not return (does not enter the PSD 40). Therefore, if it is limited to the reflected light 39 from the 、 position,
Regardless of whether or not this is incident on the PSD 40, the above-mentioned ΔI2 ≒ 0 holds, and when no reflected light is incident, the position voltage (Vo2) is necessarily smaller (lower) than the reference voltage V5.

Now, it is assumed that the reflected light 36 is in a specific light receiving state in which it is incident on the position of X = L / 2. Since the specific voltage (Vr) at this time is Vc, the indefinite signal (W) goes to the H level as shown in FIG. On the other hand, as shown in FIG. 5, in the specific light receiving state, since there is always incident light, the position voltage Vo2 is
5, the comparator 28 outputs an L-level finite signal (Cn). Therefore, as shown in FIG.
The AND gate 29 that receives the indefinite signal (W) at the level and the finite signal (Cn) at the L level performs a finite determination and outputs a corresponding determination signal (DS) at the L level. The signal selection circuit 25 that has received the L-level determination signal (DS)
The specific voltage (Vr) is received as a hold signal (Vs), and this is output as it is as a distance measurement signal (Vo3) as object distance data.

Next, it is assumed that the PSD 40 is in the non-light receiving state. Also in this case, since y ≒ 1, the specific voltage (Vr) becomes Vc, and the indefinite signal (W) is inverted to the H level. However, since no reflected light is incident, the finite signal (Cn) becomes L as shown in FIG.
Since the level remains unchanged and the infinite signal (Ci) is at the H level, the AND gate 29 makes an infinite decision, and as a result, the decision signal (DS) goes to the H level. The signal selection circuit 25 receiving the H-level determination signal (DS) outputs the hold signal (Vs)
Ranging signal (Vo3) for predetermined infinite distance data without capturing
Output as

 Now, other states will be briefly described.

As shown in FIG. 6, at positions P0 and P4 where the indefinite signal (W) is at the L level, as can be seen from FIG. 4, the specific voltage (Vr)
Corresponds to the incident position X, so that the hold signal (Vs) may be output as it is as the distance measurement signal (Vo3) regardless of the level of the finite signal (Cn).

As described above, according to the present embodiment, the specific light receiving state (specifically, the state where the reflected spot light is imaged at the center of the PSD)
Even if the PSD 40 having a characteristic indistinguishable from the non-light receiving state is used, when both the indefinite signal (W) and the infinite signal (Ci) of the H level are input to the AND gate 29, the infinity determination is made, and When an indeterminate signal (W) at a level and a finite signal (Cn) at an L level are input, a finite determination is performed. When an undefined signal (W) at an L level is input, a finite signal (W) and an infinite signal ( Regardless of the presence or absence of Ci), the light receiving surface 41 of the PSD 40 is configured such that the light receiving surface 41 of the PSD 40 changes from X = 0 to X = L
It can be used in the whole area up to the present, and if the element length L is the same as the conventional one, the range of measurement is approximately doubled. There is.

Further, in addition to the reduction of disturbance light due to the shortening of the element length L, the entire area is used and there is no portion that does not contribute to the measurement as in the related art, so that there is an advantage that the S / N ratio is improved.

The shortening has the advantage that the cost can be reduced because the material can be saved correspondingly.

In addition, window comparator 27, comparator 28,
There is an advantage that it can be realized only by adding a simple circuit including the AND gate 29 and the signal selection circuit 25.

It should be noted that the present invention is not limited to the above-described embodiment,
Various modifications can be made without departing from the scope of the invention.

For example, although the comparator 28 uses the position voltage (Vo2) as the information source for the determination, the comparator 28 may use the position voltage (Vo1).

The AND gate 29 may be a NAND gate, and is not limited to positive logic, but may be negative logic if the logic of the indefinite signal (W), the infinite signal (Ci), and the finite signal (Cn) is adapted in advance.

〔The invention's effect〕

As described in detail above, according to the present invention, even when a light receiving element having a characteristic that cannot be distinguished between a specific light receiving state and a non-light receiving state is used, an indefinite signal, an infinite signal, and a finite signal are used to combine the light receiving element. The specific light receiving state and the non-light receiving state can be electrically determined, and when the non-light receiving state is determined, predetermined infinite distance data is obtained instead of the measured subject distance data. While maintaining the conventional characteristics with a simple configuration, it is possible to shorten the element length of the light receiving element, reduce cost, save space, and increase the S / N ratio, and even if the element length is shorter than before, distance measurement is possible. It is possible to provide a distance measurement processing device capable of realizing a range expansion.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing the overall configuration of a distance measurement processor according to the present invention. FIG. 2 is a schematic diagram showing an active distance measuring optical system used together with the embodiment shown in FIG. FIG. 4 is an enlarged view showing the light receiving element and the PSD in FIG. 2 in detail, and FIGS. 4 to 7 are waveform diagrams showing operation waveforms of respective parts in FIG. 1, among which FIG. FIG. 5 shows the operation waveform of the window comparator, and FIG.
FIGS. 7 and 8 show the operation waveforms of the AND gate, respectively. FIGS. 8 and 9 both show a conventional example, of which FIG. 8 schematically shows the structure of the PSD. FIG. 9 is a sectional view schematically showing a conventional distance measuring optical system using the PSD of FIG. 11 ... first input circuit, 12 ... second input circuit, 23 ...
Differential operation circuit, 24 ... Sample hold circuit, 25 ... Signal selection circuit, 27 ... Window comparator, 28 ... Comparator, 29 ... And gate, 36,39,44 ... Reflected light, 37 ... Received light Optical axis, 38: Light receiving lens, 40: PSD, 4
1 ... Light receiving surface, (Vr) ... Specific voltage, (W) ... Indefinite signal, (Cn) ... Limited signal, (Ci) ... Infinite signal, V5 ...
Reference voltage, (DS) ... Judgment signal, S ... Base line length, f ...
Focal length, L: Element length, X: Incident position.

Claims (1)

(57) [Claims] An incident position of light when the light is incident on a light receiving surface formed of a resistive layer formed between electrodes having a predetermined interval in order to measure a distance to a subject based on the principle of triangulation. The first and second signals corresponding to are output by the light receiving elements output from the electrodes, respectively, by receiving light reflected by the object reflected from the light projected from light projecting means including a light emitting element and a light projecting lens. An output ratio calculating means for calculating a ratio between the first signal and the second signal and outputting a ratio signal; The light receiving portion having a characteristic that the magnitude of the ratio is substantially equal in a specific light receiving state in which the incident position is a specific position on the light receiving surface and in a non-light receiving state in which the reflected light is hardly incident. Element and the above ratio A first comparing means for receiving the signal, comparing the magnitude of the ratio with a predetermined range of magnitude, and outputting an indefinite signal when the magnitude is within the range; Second comparing means for receiving at least one of the signals, comparing the magnitude of the signal with a predetermined reference value, and outputting a finite signal when the signal exceeds the reference value; When receiving the finite signal, a finite decision is made that means the subject is at a finite distance, and when not receiving the finite signal, an infinite decision corresponding to the non-light receiving state is made. On the other hand, when the indeterminate signal has not been received, the state determining means for performing the finite determination regardless of the presence or absence of the finite signal, and when the state determining means has performed the finite determination, the output ratio calculation Of means Outputs subject distance data calculated based on the signal, when performing the infinite determination, distance measurement calculation processing apparatus characterized by comprising a signal selecting means for outputting a predetermined infinite distance data.