JP2888492B2 - Distance information output device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a distance information output device, and more particularly to a device for projecting pulsed light such as infrared light onto a subject and subjecting the subject to a distance based on reflected light from the subject. The present invention relates to an active distance information output device for detecting the distance information.

2. Description of the Related Art There are roughly two types of autofocus (hereinafter abbreviated as AF) devices applied to a still camera, a video camera, and the like. One is a passive method that uses the luminance distribution information of the subject, and the other has its own light emitting means,
This is a so-called active method in which the distance is measured by the reflected light of the projection signal. The active system has a high penetration rate because it has a simple configuration and is inexpensive as disclosed in, for example, JP-A-1-291111. Next, one example is
Shown in the figure.

FIG. 5 is a block diagram showing a configuration of a main part of a generally known active AF camera. The light emitted from the infrared light emitting diode IRED1 is condensed by the light projecting lens 2 and The reflected light is imaged by a light receiving lens 4 on a well-known light position detecting element (hereinafter, abbreviated as PSD) 5 composed of a semiconductor element. The PSD5 photocurrent I ₁ and I ₂ are diverted in accordance with the image forming position, the photocurrent I ₁ and I ₂ to the shunting is supplied to the AF IC 6. The AF IC 6 is connected to the IRE through the IRED driving transistor 1A.
D1 is pulsed, and the photocurrents I ₁ , I
_The distance measurement data based on ₂ is supplied to the CPU 7.

On the other hand, an exposure control (hereinafter abbreviated as EE) light receiving element 8 for converting the brightness of a subject into an electric signal controls an appropriate exposure in combination with an EE IC 9. The CPU 7 controls the sequence of the entire camera, and also performs calculations for driving the shutter opening time, the lens for focus adjustment, and the like. The output of the CPU 7 drives a motor 11 serving as a power source for performing shutter and film winding and lens feeding by a driver 10.

Here, the operation principle of the infrared projection type triangulation which measures the object distance by the PSD5 will be described with reference to FIG. When a line parallel to the line connecting the emission center of IRED1 and the principal point of the projection lens 2 is extended from the principal point of the light-receiving lens 4, the point that crosses PSD5 is determined from the end of PSD5 on the IRED side. At the point of length a. Then, assuming that the incident position of the reflected signal light is x as shown in the figure, the photocurrent outputs I ₁ and I ₂ of PSD5 are P
If the total length of SD5 is t Becomes Here, I _p0 is the total amount of reflected signal light, and varies depending on the reflectance of the subject, the amount of IRED light, the photoelectric conversion efficiency of the PSD, and the like.

Moreover, the principle of triangulation, the object distance l is, s the base line length, as shown in FIG, if the focal length of the receiver lens 4 and f _0, Is required.

Therefore, from the above equations (1), (2) and (3), the distance information of the subject is obtained by the following equation.

At this time, the term of the total amount of the reflected signal light, I _p0 , has no _relation in the calculation.

[Problems to be Solved by the Invention] However, the light projection pattern of IRED1 actually has a certain finite size as shown in FIG. 6A. that is,
Because the light emitting portion of the IRED1 is not a point source, the focal length of the projection lens 2 and f _1, when the tip diameter of IRED1 and d _c, the spot diameter indicating the size of the projection pattern at an object distance l d _s Has the relationship d _s = d _c · l / f ₁ (5). To explain this with a concrete numerical example, since d _c = 0.4 mm f ₁ = 10 mm in general, a high-speed projection spot diameter of d _s = 8 cm was projected for the subject 3 with the subject distance of 2 m. That is, the diameter of the light projection spot 1a increases as the subject distance 1 increases.

Therefore, as shown in FIG.
There is no problem when the light projection spot 1a is perfectly aligned with the subject 3, but when the light projection spot 1a does not hit the subject 3 completely and shifts (hereinafter, referred to as spot departure), an error occurs. It is often a distance measurement.

As described above, the subject distance 1 is obtained by changing the incident position x of the IRED reflected light on the PSD 5. However, if the projection spot 1a deviates from the spot, even if the subject is at the same distance, the distance information is obtained. different. Then, the fact that when the light projecting spot 1a moves on the PSD 5, thereby causing erroneous distance measurement will be described with reference to FIGS. 7A to 9B.

FIG. 7A shows respective reflected signal light spots from a subject at a short distance when the distance measuring optical system is configured as shown in FIG. 5, and FIG.
1B shows the incident position on PSD5 of FIG. Since these reflected light spot 1b has a finite size, the position of the center of gravity each x _N, with x _F. These are the sixth
As shown in Figure B, the projected light spot 1a is, in the case that hits the object 3, the photocurrent I ₁ output from both ends of the PSD, I ₂ is the center of gravity position x of the reflected light spot 1b depending on the _N or x _F, the (1) are outputted in accordance with equation (2).

Next, when the light projection spot 1a does not hit the subject 3 and a half (dotted line portion) deviates as shown in FIG.
As shown in Figure 8B, when it should properly reflected signal light spot centered on x ₀ is irradiated onto the PSD 5, the center of gravity of the reflected signal light spot by spot off is shifted towards the x _1. Therefore, (see FIG. 5) IC 6 for AF, this actually close to the center-of-gravity position x _F of the reflected signal light spot from an infinity object than the distance, i.e. resulting in ranging erroneous long distance side. Further, when the spot deviates as shown in FIG. 9A, as shown in FIG. 9B, the position of the center of gravity of the reflected signal light spot 1b is now changed to the reflected signal light spot 1b from the close-side object.
Closer to the center-of-gravity position x _N of, that is, since the shifts in x ₂ in the short distance side, AF for IC6 is resulting in ranging erroneously short distance side than the actual distance.

To solve such a problem, Japanese Patent Application Laid-Open No. 63-1310
In No. 20, using scanning means calling light amount peak detection means,
Scan the IRED light spot to the left and right across the subject,
It has been proposed to detect a state in which a projected spot is completely hit on a subject based on an output result of a light quantity peak detection circuit, and select a distance measurement result at that time as correct distance information.

However, in this proposal, there is a problem that a mechanical movable part for scanning the light projecting spot to the left and right across the subject is required, so that the configuration of the apparatus becomes complicated and reliability is poor.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a distance information output device that solves the above-mentioned problem and can prevent erroneous distance measurement even when a spot deviates in an active distance measurement method.

[Means and Actions for Solving the Problems] A distance information output device according to the present invention includes a light projecting lens that projects light to a subject, a light receiving lens that is disposed at a distance from the light projecting lens by a base line length, A first light source for projecting light to the subject corresponding to the center of the screen to project light to the subject via the light projecting lens, and reflected light of the light source from the subject via the light receiving lens And a distance information output device for outputting distance information to a subject based on the two electric signals from the light position detecting element. First distance information detecting means for detecting first distance information according to a ratio of the two electric signals of the light position detecting element;
Second distance information detecting means for detecting second distance information in accordance with a sum signal of the two electric signals of the light position detecting element; and the first and second distances when the first light source emits light. Error detecting means for comparing information and detecting whether or not there is a distance measurement error.

The distance information output device includes a first light source and a second light source provided along the base line length direction and projecting light to a subject via the light projecting lens. If a ranging error is detected, the second
And outputting distance information based on the first distance information or the second distance information at this time, wherein the second light source is disposed on the left and right of the first light source. Any one of the two light emitting elements according to the result of the determination by the error detecting means as to which side of the light projection of the first light source onto the subject is missing. And outputs distance information based on the first distance information or the second distance information at this time. If the first distance information is closer than the second distance information, the error detection means determines that the predetermined side of the light projected on the subject is missing.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a configuration block diagram of a distance information output device showing a basic concept of the present invention. In FIG. 1, unlike FIG. 5, an IR having three independently controllable light emitting chips 1R, 1C, and 1L is a feature of the present invention.
In addition to ED 1X and a ratio operation circuit 19 for performing a distance measurement operation based on the above equation (4), a sum operation circuit 20 for performing a distance operation based on the sum of the photocurrents I ₁ and I ₂ output from the PSD 5 , And the aforementioned PS
A correction data storage unit 21 is provided for correcting the variation of the total photoelectric flow I _p0 incident on D5 with each product. Except for these points, the configuration is the same as that of FIG. 5, and the same components are denoted by the same reference numerals and description thereof will be omitted.

The sum operation circuit 20 determines the subject distance by an operation different from the expression (4) based on the following principle. That is, when the projected spot of the IRED 1X is completely diffused on the subject 3, the amount of light I incident on the PSD 5
_p0 satisfies the relationship of I _p0 = (1 / K · l) ² (6) K: quantification and is a function of the subject distance l. Therefore, The distance information 1 / l can be calculated from the following equation.

Here, the constant K greatly varies due to the infrared reflectance of the subject 3, the variation of the projection power of the IRED 1X, the variation of the photoelectric conversion efficiency of the PSD 5, the variation of the arithmetic circuits 19 and 20, and the like. Therefore, the reflectivity of the subject 3 is set to 50% of the average of the reflectivities of the general subjects, and the change in K caused by the variation of the various constituent factors is corrected by the correction data stored in the correction data storage unit 21. The correction will be made in accordance with the data.

In the distance information output device according to the present invention configured as described above, if the distance measurement result obtained by the first light source IRED 1C greatly differs between the result obtained by the above expression (4) and the result obtained by the above expression (7). Is determined to be a spot departure, and an adjacent IRED at a position where the projection spot, which is the second light source, does not deviate.
By illuminating 1L or 1R and re-measuring, erroneous distance measurement due to a spot departure is prevented.

FIG. 2 shows an embodiment of the distance information output device of the present invention in which the AF IC 6 and PSD 5 are more specifically configured in accordance with the basic concept of the present invention shown in FIG. FIG. 3 is a timing chart of the operation of each unit in FIG. Here, the photocurrents I ₁ , I
_Since the circuit systems for amplifying the two signals 2 are formed in exactly the same manner, only the circuit system for _one photocurrent I1 will be described here.

When the camera is pointed at the subject, the subject is generally steadily illuminated by sunlight or artificial illumination light.Therefore, PSD5 receives not only signal light but also steady light due to those lights. and it outputs the constant photocurrent I ₀ due. In operation AF, it is necessary to take out the fixed light (see FIG. 1) IRED 1X current I ₀ is removed the signal photocurrent I _1, to discriminate only I ₂ by.

Therefore, the operation of removing the stationary photocurrent will be described first. The discrimination between the steady light current I ₀ and the signal light currents I ₁ and I ₂ is as follows.
Since the components of the stationary light current I ₀ in the state basically emitted a state where IRED does not emit light does not change, variation is carried out by determining that the signal beam currents I _1, I _2.

Before the emission of IRED 1X, the steady-state photocurrent I ₀ is sucked into the amplifier 12 (13) by low input impedance, and the transistor
It is amplified by 40 (51). This amplified current is supplied to the compression diode 4 by the current mirror circuits 41 (52) and 43 (54).
Although flow into the 6 (57), this time, the potential of the compression diode is increased by the influx of the constant photocurrent I _0, worked hold amplifier 48 (59) controls the base potential of the transistor 50 (61), ambient light it tries to eject the current I ₀ to the ground.

That is, the non-inverting input terminal of the hold amplifier 48 (59)
Compression diode 4 biased at I _DB of current source 45 (56)
6 (57), by the current source 68 to the inverting input terminal, like I _DB
Since the compression diode 69 biased by the current of the input is input through the buffers 47 (58) and 67, respectively, as long as the hold amplifier 48 (59) is functioning, the compression diode
Current due to the constant photocurrent I ₀ to 46 (57) is adapted not flow. In other words, this circuit is stable in the state where no current flows in the line X ₁ (X ₂ ) in the figure.

Next, FIG. 3 by the application of emission signal IRED that (B), the pre-amplifier 12 in a state in which the signal photocurrent I ₁ a steady photocurrent I ₀ if IRED 1X emits light (I ₂₎ is superimposed ( Entered in 13). At this time, the bias cut signal B (third signal) supplied from the timing circuit 33 in synchronization with the emission of IRED 1X
(See FIG. (C)), the hold amplifier 48 (59) is turned off, so that the steady-state photocurrent I ₀ is determined based on the potential stored in the hold capacitor 49 (60). , But only the signal light current I ₁ (I ₂ ) is
The current mirror circuit 41 (5)
2) It flows into the compression diode 46 (57) via the 43 (54). At this time, the current source 45 (56)
Similar to (59), because it is turned off by a bias cut signal B (B line in FIG. 2), the compression voltage V _A by only the signal light current I ₁ is generated in the compression diode 46. Similarly, the signal light current I ₂ flows into the compression diode 57 after the stationary light current I ₀ is removed.

These compressed voltages V _A , V _B are input via buffers 47, 58 to a ratio calculation circuit including transistors 62, 63, a current source 64, an integration capacitor 65, and a reset circuit 66. Integration signal IN supplied from timing circuit 33 in synchronization with IRED emission
T (see FIG. 3C) becomes active, and the current source 64
Is turned on, the current I flowing through the integrating capacitor 65 is
_INT is So that the integration capacitor 65 has Voltage signal is generated.

Here, n is the number of times of IRED emission, I ₀ is the current of the current source 64, τ
Is the integration time for one time, and C is the capacity of the integration capacitor 65.

The reset circuit 66 sets the potential of the integration capacitor 65 to an initial state and sets V _INT = 0 prior to the emission of IRED. Equation (9) of the V _INT is CPU7 is assumed that read by the A / D conversion, the equation (4) and (9) Holds, the first distance information 1 / lr is obtained from V _INT .

The above is the first distance information detecting means of the first embodiment.
Is a description of a ratio calculation operation for obtaining distance information lr.

Next, in the calculation of the sum of the signal light currents I ₁ and I ₂ , similarly to the ratio operation, the amplified signal light current I ₁ is integrated by the current mirror circuits 41 and 42 to integrate the sum of the light amounts. (Light quantity integration circuit). Similarly, the amplified signal light current I ₂
Is the signal light current I by the current mirror circuits 52 and 53.
₁ is added. However, a bias current constantly flows through the transistors 42 and 53 constituting the current mirror circuit in addition to I ₁ and I ₂ . It is transistors 40,41,42,4
If 3 is not biased, the response to the signal current of IRED will be poor, so in the state where the current of the lines X ₁ and X _{2 in} the figure becomes 0 by the above-described steady light removing operation, It is biased in each I _PB accordance flow I _PB. Therefore, the light quantity integration circuit removes the bias of the I _PB, and has a circuit for integrating only the photocurrent I ₁ and I _2.

In other words, the current flowing from the transistors 42 and 53 is removed before the IRED light emission, and only the current I ₁ + I _{2 obtained} by subtracting the current is integrated, thereby performing the same operation as the above-described steady light removing circuit. .

Before the IRED light emission, the integration signal INT output from the timing circuit 33 is non-active, and when the analog switches 72 and 73 are turned on and the analog switches 70 and 71 are turned off, the bias current 2I _PB
The minute is discharged to ground by the operation of the hold amplifier 76. The reason is as follows. When a current flows through the resistor 75, the voltage drop is detected by the hold amplifier 76 and the transistor 78 is controlled.

That is, when a current is to flow in the direction A in the figure, the potential of the non-inverting input terminal of the hold amplifier 76 increases, so that the transistor 78 increases the collector current to suppress the current in the direction A. Conversely, if a current is to flow in the direction b in the figure, the potential at the inverting input terminal of the hold amplifier 76 increases, so that the transistor 78 reduces the collector current and tries to suppress the current in the direction b. . In this way, even if the current flows in either direction a or b through resistor 75 due to the noise component included in the bias current 2I _PB that is the sum of both channels, this circuit removes it sensitively. can do.

Next, when IRED emits light, the integration signal INT output from the timing circuit 33 becomes active, thereby turning off the analog switches 72 and 73 and turning on the analog switches 70 and 71.
Is turned on, so that the bias current obtained by adding the two channels is discharged to the ground by the transistor 78 based on the electric charge stored in the hold capacitor 77. Then, only the current based on the signal light currents I ₁ and I ₂ is guided to the light intensity integration circuit including the integration amplifier 79 and the integration capacitor 80 along the path C, and is integrated. Therefore, assuming that the current amplification factor of the amplification transistors 40 and 51 is β, the integration amplifier 79
The output voltage V _PINT is obtained as V _PINT = nβ (I ₁ + I ₂ ) τ / C _P = nβ I _p τ / C _P (11), which is a calculation result based on the sum of the signal light amounts. Here, _CP is the capacitance of the integration capacitor 80.

The reset circuit 81 uses the reset signal R from the timing circuit 33 to generate V _PINT
Is reset to the initial state. When CPU7 performs A / D conversion,
_{Read the PINT} and obtain the distance information 1 / la according to the following equation (12).
Is required. From equations (7) and (11) The reading of the above V _PINT and V _INT is performed on the premise of A / D conversion by a generally known square integration method, as shown in FIG.
This is shown in (E). The above is the description of the sum calculation operation for obtaining the second distance information la in the second distance information detecting means of the present embodiment.

FIG. 4 is a flowchart for calculating an actual distance in a distance measuring system having the two distance measuring methods of the ratio operation and the sum operation. Here, by simplifying equation (12), However, I _p DATA is a digital value obtained by reading V _PINT into the CPU. Equation (10) also _shows that V _INT
Represents the read digital value as AD, and is simplified to the form of 1 / lr = A.AD + B (14). Here, k, A, and B are all constants.

By the way, the formula of the ratio calculation and ranging based on the emission of the second light source, IRED 1R and IRED 1L, is a constant a (fifth) indicating the position of the reflected signal light spot 1b incident on the PSD 5 in the expression (10)
Therefore, the value of the constant B must be changed in the 1 / lr operation. That is, when IRED 1L emits light, 1 / lr = A ・ AD + B _L (15), and when IRED 1R emits light, 1 / lr = A ・ AD + B _R (16).

The actual operation will be described with reference to the flowchart of FIG. 4. In step S1, the distance measuring operation already described with reference to FIG. 2 is performed. Here, IRED 1C is selected to emit light. Then, when the operation proceeds to step S2, a sum operation, that is, data obtained by integrating the light amount is read out, and in step S3, data is read out by a ratio operation. The above is as shown in (F) and (G) of the timing chart of FIG.

In step S4, the distance measurement calculation described in the above equation (13) is performed. In step S5, the distance measurement calculation described in the above equation (14) is performed.
The correction is performed by the CPU 7 while referring to the correction data from the correction data storage means 21 (see FIG. 1). As a result, second distance information la is obtained in step S4, and first distance information lr is obtained in step S5. Then, in step S6, the first distance information based on the ratio calculation is compared with the second distance information based on the sum calculation to determine the distance measurement error Δl. Then, in steps S7 and S10, the distance measurement error Δl is compared. I do.

Referring back to FIGS. 8A to 9B again, as shown in FIG. 9A, when the light projection spot comes off, since the amount of the incident signal incident on the PSD 5 is reduced due to the spot coming off,
The second distance information la obtained in step S4 outputs the far distance side, and the first distance information lr obtained in step S5 is output.
Conversely, as described above, the short-distance side is output, so that it can be determined that the reflected light spot 1b deviates to the right as shown in the figure.
Therefore, at this time, the process branches to step S8, and a slightly leftward IRED signal is projected so that the projected spot does not deviate from the subject. That is, the distance is measured by IRED 1L, the ratio calculation as shown in the equation (15) is performed in step S9, and in step S14, this is determined as the subject distance l.

Next, as shown in FIG. 8A, when the light projection spot goes off, both the ratio calculation and the sum calculation output a long distance,
It is indistinguishable from the case where a long-distance subject is actually measured. Therefore, in this case, in step S10, the process branches to step S11 to cause the IRED 1R to emit light and determine which one of them is in order to determine whether the spot is out of the spot or whether a distance is actually measured. I do.

If the projection spot is off as shown in FIG. 8A, the IRED 1R is fired to measure the right side of the projection spot, and the calculation result of step S12, that is, the second light source IRED
The first distance information l _r1 by 1R should be output as a distance that is closer than the center distance measurement result l _r obtained in step S5. Conversely, if the distance is actually measured at a long distance, l _r1 should also output the long distance. Therefore,
In step S13, the correct measurement result towards the close of lr and l _r1, through step S14, determining this as the object distance l.

In the above-described embodiment, the IRED 1X includes three chips 1L, 1C, and 1R.
However, the same concept can be used to increase the number of chips constituting the IRED 1X to provide a more effective autofocus device.

According to the above-described embodiment, it is possible to provide an easy-to-use autofocus system with a simple configuration that is less likely to cause erroneous distance measurement due to a spot deviation. By using this method, an in-focus photograph can be taken without accurately aiming at the subject, so that it is possible to design a camera that is easy to use even for beginners and has good instantaneous photography.

[Effects of the Invention] As described above, according to the present invention, at least three light emitting units are provided, the addition operation and the ratio operation are performed on the light emission in the central part, and the spot departure is determined from the difference. Since the distance is measured by emitting the IRED that does not cause a spot departure from the result, a remarkable effect that erroneous distance measurement can be prevented even when a spot deviates in the active distance measurement method is exhibited.

[Brief description of the drawings]

FIG. 1 is a block diagram of a configuration of a distance information output device showing a basic concept of the present invention, and FIG. 2 is a distance information according to the present invention which specifically configures an AF IC and a PSD in FIG. FIG. 3 is a timing chart showing the operation of each part of FIG. 2; FIG. 4 is a flowchart of the distance measuring operation in the embodiment shown in FIGS. 2 and 3; FIG. 5 is a block diagram showing a configuration of a main part of a conventional active AF camera. FIGS. 6A and 6B are diagrams showing a case where a projection spot having a finite spread in FIG. FIGS. 7A and 7B are diagrams showing an incident position on a PSD of a reflected signal light spot from a subject at a short distance or a long distance, FIGS. 8A and 8B and FIGS. Relationship between Projected Spot and Subject and Reflection when Object Does Not Hit Subject The incident position at issue light spot on the PSD diagrams showing respectively. 1C ... IRED (first light source) 1L, 1R ... IRED (second light source) 2 ... Light emitting lens 3 ... Subject 4 ... Light receiving lens 5 ... PSD (light position detecting element) 6 ... AF IC (first and second distance information detecting means) 7... CPU (error detecting means)

Claims (4)

(57) [Claims] 1. A light projecting lens for projecting light to a subject, a light receiving lens disposed at a distance from the light projecting lens by a base line length, and a light projecting lens for projecting light to the subject via the light projecting lens. A first light source for projecting light to a subject corresponding to the center portion of the screen; and a reflected light of the light source from the subject received through the light receiving lens, into two electric signals corresponding to the incident position. A light position detecting element to be converted, and a distance information output device for outputting distance information to a subject based on the two electric signals from the light position detecting element, wherein a ratio of the two electric signals of the light position detecting element First distance information detecting means for detecting first distance information according to the following, and second distance information detecting means for detecting second distance information according to a sum signal of the two electric signals of the optical position detecting element. And projection of the first light source. An error detecting means for comparing the first and second distance information during light and detecting whether or not there is a distance measurement error; and a distance information output device. 2. The distance information output device includes a first light source and a second light source provided along the base line length direction for projecting light to a subject via the light projecting lens. If the error detecting means detects a distance measurement error, the second light source is projected, and distance information is output based on the first distance information or the second distance information at this time. The distance information output device according to claim 1, wherein: 3. The second light source has at least two light projecting elements disposed on the left and right of the first light source, and the first light source projects light onto a subject by the error detecting means. In accordance with the determination result of which side is missing, one of the two light emitting elements is projected, and the distance information is determined based on the upper first distance information or the second distance information at this time. The distance information output device according to claim 2, which outputs the distance information. 4. The error detecting means determines that a predetermined side of the light projected on the subject is missing when the first distance information is closer than the second distance information. The distance information output device according to claim 1.