JP2006105604A - Range finder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a range finder capable of measuring accurately a distance up to a subject. <P>SOLUTION: An infrared ray is emitted from an IRED 4 to the subject, and an AF signal is generated with integration by an integration circuit 15, based on reflected light. An AF signal by nonprojection of light is also generated based on light from the subject, without emitting the infrared ray from the IRED 4 to the subject. A CPU 1 subtracts the AF signal by the nonprojection of light from the AF signal to generate the AF signal after corrected. The distance up to the subject is calculated in the CPU 1, based on the generated AF signal. When the AF signal is a prescribed threshold value or less, the subject is photographed by an infinite mode, assuming that the subject exists in a long distance. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a distance measuring device that measures a distance to a subject.

  Conventionally, as described in Japanese Patent Application Laid-Open No. 60-189720 (Patent Document 1), a distance measuring device that irradiates light on a subject and calculates a distance based on reflected light from the subject is known. ing. The distance measuring device described in Patent Document 1 can determine that the subject is at an infinite position when the reflected light from the subject is below a predetermined determination level.

Here, in the distance measuring device described in Patent Document 1, external light other than the reflected light from the subject is taken in as reflected light, and the distance is calculated. The reflected light from the subject becomes weaker as the distance from the subject becomes longer. When the subject is more than a certain distance, the external light is larger than the reflected light from the subject, and is greatly affected by the external light when distance measurement is performed. Therefore, in this case, an accurate distance cannot be calculated. Therefore, as described in Japanese Patent Laid-Open No. 10-274524 (Patent Document 2), when outside light other than the reflected light from the subject is captured at a predetermined value or more, the AF signal and the distance using the clamping means are used. Is known to be calculated. That is, in Patent Document 2, when the far side signal is equal to or greater than a predetermined value using the clamping means (that is, when the subject is at or above the distance indicated by the predetermined value), it is predetermined instead of the far side signal. Output the numerical value. Then, it is described that the AF signal and the distance are calculated based on the output numerical value.
JP-A-60-189720 JP-A-10-274524

  Normally, when the subject is at a predetermined distance or more, focusing control is performed assuming that the subject is at an infinite position. That is, a certain threshold value is determined in advance, and when the AF signal is equal to or less than the predetermined threshold value, the focus control is performed assuming that the subject is at an infinite position.

  However, the technique described in Patent Document 2 includes outside light other than reflected light from the subject. Therefore, since it is necessary to consider the error (steady light error) due to the external light, the above threshold value must be set to a large value. Note that Patent Document 2 describes a circuit that removes stationary light that removes external light. However, even if this is taken into consideration, the influence of noise increases at a long distance, and the above-described threshold needs to be set large. There is. If the threshold value is set to a large value, the distance that can be measured is shortened, and appropriate photographing according to the distance to the subject cannot be performed.

  Therefore, an object of the present invention is to provide a distance measuring device that can accurately measure the distance to a subject far away.

  In order to solve the above-described problem, the distance measuring device of the present invention receives a light projecting unit that irradiates a subject with light, and external light including reflected light of the light irradiated by the light projecting unit, Light receiving means for outputting a light receiving signal corresponding to the distance to the subject, and a reference AF signal generated based on the light receiving signal output by the light receiving means by irradiating the subject with light by the light projecting means And a non-light-projecting AF generated in a non-light-projecting state based on a light-receiving signal output from the light-receiving means without irradiating the subject with light by the light-projecting means. A non-projecting distance measuring means for acquiring a signal, and a final AF signal obtained by subtracting the non-projected AF signal acquired by the non-projected distance measuring means from the reference AF signal acquired by the projected distance measuring means. A computing means for obtaining the computing means; And a, a distance calculation means for calculating a distance to the subject based on the obtained final AF signal by.

  According to the present invention, based on the final AF signal obtained by subtracting the non-projection AF signal acquired by the non-projection distance measurement unit from the reference AF signal acquired by the projection distance measurement unit by the calculation unit and subtracting it. The distance can be calculated. Since the acquired final AF signal is obtained by removing external light noise, an accurate distance can be calculated.

  Further, when the acquired final AF signal indicates a predetermined threshold value or less, since the subject is far away, shooting in the infinity mode is required. In this case, since the information conventionally includes external light noise, it is necessary to set the threshold value higher by the amount of external light noise. However, in the present invention, since it is possible to make a determination based on the final AF signal from which external light noise has been removed in advance, the threshold for the infinity mode can be set low, and accurate ranging can be performed over a long distance. It can be carried out.

  Further, the distance measuring device of the present invention includes distance determination means for determining whether the distance to the subject is within a predetermined distance based on the reference AF signal acquired by the light projection distance measuring means. The distance calculation means, when the determination means determines that the distance to the subject is within a predetermined distance, without operating the non-projection distance measurement means, the calculation means It is also preferable to calculate the distance to the subject based on the reference AF signal acquired by the light projection distance measuring means without calculating the distance to the subject based on the final AF signal acquired by the above.

  According to the present invention, when it can be determined that the subject is within a predetermined distance based on the reference AF signal, the reference AF signal is acquired without acquiring the non-projection AF signal by the non-projection distance measuring means. The distance from the subject to the subject is calculated. Thereby, ranging time can be shortened. In other words, when there is a subject within a predetermined distance, the influence of external light noise is small, so it is not necessary to acquire the non-projection AF signal over time and remove the influence of external light noise. An accurate distance can be calculated only with the AF signal, and the distance measurement time can be shortened.

  Further, the distance measuring device of the present invention further includes a photometric means for measuring the external light luminance, and a luminance determining means for determining whether the luminance measured by the photometric means is equal to or lower than a predetermined luminance. And the distance calculating means does not operate the non-light-projecting distance measuring means when the brightness determining means determines that the brightness is equal to or lower than a predetermined brightness, and adds the final AF signal acquired by the calculating means to the final AF signal. It is also preferable to calculate the distance to the subject based on the reference AF signal acquired by the light projection distance measuring means without calculating the distance to the subject based on the reference AF signal.

  According to the present invention, when the subject has a predetermined luminance or less, the distance to the subject is calculated using only the reference AF signal without acquiring the non-projection AF signal by the non-projection distance measuring means. is there. Thereby, ranging time can be shortened. That is, when the subject has a predetermined luminance or less, the influence of external light noise is small, so it is not necessary to acquire the non-projection AF signal over time and remove the influence of external light noise. An accurate distance can be calculated using only the reference AF signal, and the distance measurement time can be shortened.

  In the distance measuring device of the present invention, the light projection distance measuring unit obtains N pieces of numerical information indicating the amount of reflected light from the subject by irradiating the subject with light N times. The reference AF signal is calculated by accumulatively storing the numerical information indicating the N light amounts, and the non-projection distance measuring means acquires M (M <N) numerical information indicating the light amount of the subject. It is also preferable to cumulatively accumulate the acquired information indicating the M light amounts to calculate a non-projection AF signal, and multiply the accumulated numerical information by a predetermined coefficient.

  According to the present invention, when the non-projection AF signal is acquired by the non-projection distance measuring means, the acquisition time (that is, the distance measurement time) for acquiring the non-projection AF signal is reduced by reducing the number of distance measurement. ) Can be shortened.

  In the distance measuring device of the present invention, the light projecting distance measuring unit further irradiates the subject with light at a predetermined time X at least once, so that the amount of reflected light from the subject is increased. Is obtained for a time determined by the predetermined time X to obtain the reference AF signal, and the non-projection distance measuring means further obtains numerical information indicating the amount of light of the subject for a predetermined time Y per time. It is also possible to acquire the non-light-projecting AF signal by acquiring the time determined by (Y> X) and multiplying signal information obtained by accumulating information indicating the acquired light quantity by a predetermined coefficient. preferable.

  According to the present invention, when a non-projection AF signal is acquired by the non-projection distance measuring means, the integration time per time is lengthened, and the number of acquisitions of numerical information indicating the light quantity is reduced, thereby reducing the non-projection. The acquisition time (that is, distance measurement time) for acquiring the optical AF signal can be shortened.

  The present invention can realize a distance measuring device that can accurately measure the distance to a far object.

  The present invention can be readily understood by considering the following detailed description with reference to the accompanying drawings shown for the embodiments. Subsequently, embodiments of the present invention will be described with reference to the accompanying drawings. Where possible, the same parts are denoted by the same reference numerals, and redundant description is omitted.

  First, the camera 9 provided with the distance measuring device according to the present embodiment will be described.

  FIG. 1 is a perspective view showing an appearance of the front side of a camera 9 provided with a distance measuring device according to the present embodiment.

  As shown in FIG. 1, the camera 9 is a lens shutter camera loaded with a 135 film format cartridge. The camera 9 is provided with a release button 9a at its upper end. At the center of the front surface of the camera 9, a lens barrel 9b incorporating the taking lens 8 is attached. As the lens barrel 9b, for example, a photographic lens barrel that can perform an autofocus operation including a single focus lens having a focal length of 24 mm and an open aperture F2.0 and a shutter is used. A finder 9c, a strobe light emitting unit 9d, an AF light projection window 4a, and an AF light receiving window 5a are provided on the top of the camera 9. An IRED (infrared light emitting diode) 4 and a PSD (position detecting element) 5 are arranged so that light can be emitted and received through the AF light projection window 4a and the AF light receiving window 5a. The IRED 4 and PSD 5 are based on the principle of triangulation, for example. A distance measuring unit that measures the distance to the subject is configured.

  The camera 9 is provided with a photometry unit 9e. The photometry unit 9e functions as photometry means for measuring the external light luminance within the photographing field. As this photometric unit 9e, for example, a center-weighted average photometric sensor provided with one SPD device (incorporating an infrared cut filter on the optical path) is used. This SPD device is approximately oriented on the optical axis of the taking lens optical system.

  A shutter 9 f is incorporated on the optical axis of the photographing lens 8 inside the camera 9. The shutter 9f is configured to include a diaphragm spring sector that gives a necessary exposure amount to the film. As the shutter 9f, for example, a two-blade lens shutter having an F value of F2.0 at the time of opening and a control range Ev 2 to 16 [EV] is used.

  Next, a distance measuring device provided in the camera 9 will be described. FIG. 2 is a block diagram of the distance measuring apparatus. As shown in FIG. 1, the distance measuring apparatus according to the present embodiment is provided with a CPU 1. The CPU 1 controls the entire camera including the distance measuring device, and controls the entire camera including the distance measuring device based on the program stored in the ROM in the CPU 1 and the parameters stored in the EEPROM 2. Do.

  An IRED 4 is provided in the distance measuring device. The IRED 4 functions as a light projecting unit that projects a light projecting beam onto the subject by light emission. The IRED 4 is connected to the CPU 1 via the driver 3 and controlled to emit light. The distance measuring device is provided with PSD5. The PSD 5 functions as a light receiving means for receiving each reflected beam of the projected beam projected from the IRED 4 to the subject. Further, the distance measuring device is provided with an autofocus IC (hereinafter referred to as “AFIC”) 10 for processing the output signal of the PSD 5. The operation of the AFIC 10 is controlled by the CPU 1, and an AF signal (integrated signal) output from the AFIC 10 is input to the CPU 1.

When a projection beam that is infrared light is emitted from the IRED 4, the projection beam is projected onto the subject via the AF projection window 4a disposed in front of the IRED 4. A part of the projected beam is reflected and received at any position on the light receiving surface of the PSD 5 via the AF light receiving window 5 a disposed on the front surface of the PSD 5. This light receiving position is in accordance with the distance to the subject. The PSD 5 outputs _two signals I ₁ and I ₂ corresponding to the light receiving position.

The signal I ₁ is a near side signal that becomes larger as the distance is shorter if the amount of received light is constant, and the signal I ₂ is a far side signal that becomes larger as the distance is longer if the amount of received light is constant. is there. The sum of the signals I ₁ and I ₂ represent the amount of reflected light PSD5 has received. The near-side signal I ₁ is input to the PSDN terminal of the AFIC ₁₀ and the far-side signal I ₂ is input to the PSDF terminal of the AFIC 10. However, in actuality, a signal in which the stationary light component I ₀ is added to each of the near-side signal I ₁ and the far-side signal I ₂ due to external conditions is input to the AFIC 10.

The AFIC 10 is an integrated circuit (IC) and includes a first signal processing circuit 11, a second signal processing circuit 12, a clamp circuit 13, an arithmetic circuit 14, and an integration circuit 15. The first signal processing circuit 11 receives the signal I ₁ + I ₀ output from the PSD ₅ , removes the stationary light component I ₀ included in the signal, and outputs the near-side signal I 1. The second signal processing circuit 12 receives the signal I ₂ + I ₀ output from the PSD ₅ , removes the stationary light component I ₀ included in the signal, and outputs the far-side signal I ₂ .

The clamp circuit 13 receives the far side signal I ₂ output from the second signal processing circuit 12, compares the far side signal I ₂ with a preset clamp signal I _C, and the far side signal I ₂ is clamped. it outputs the far-side signal I ₂ when it is a signal I _C or higher, and outputs the clamp signal I _C when the far-side signal I ₂ is smaller than the clamp signal I _C. Hereinafter, the output signal output from the clamp circuit 13 is represented by I _{2 C.}

Further, the clamp circuit 13 has a function of detecting whether the output signal I _2C is a far-side signal I ₂ as or clamp signal I _C. Details of the clamp circuit 13 will be described later.

Arithmetic circuit 14, the near-side signal I ₁ output from the first signal processing circuit 11, receives the output signal I _2C outputted from the clamping circuit 13, the output ratio _{(I 1 / (I 1 +} I 2C )) And outputs an output ratio signal representing the result. The output ratio (I ₁ / (I ₁ + I _2C )) represents the light receiving position on the light receiving surface of the PSD 5, that is, the distance to the subject.

  The integrating circuit 15 receives the output ratio signal and integrates the output ratio with the integrating capacitor 6 connected to the CINT terminal of the AFIC 10 many times, thereby improving the S / N ratio. At this time, the integration of the output ratio to the integration capacitor 6 may be performed when the integration capacitor 6 is charged with a constant voltage in advance and gradually discharged according to the output ratio signal, or the integration capacitor 6 in a discharged state may be integrated. The charging may be performed gradually according to the output ratio signal.

  The integrated output ratio is output from the SOUT terminal of the AFIC 10 as an AF signal (integrated signal). Here, the AF signal to be output is converted to outside light without being projected by AFDATA, which is a reference AF signal that is projected by the IRED 4 and is generated based on the outside light including the reflected light from the subject. AFOFFDATA, which is a non-projection AF signal generated based on this. Therefore, the integrating circuit 15 functions as a part of the light projection distance measuring means that generates and acquires the reference AF signal, and as a part of the non-light projection distance measurement means that generates and acquires the non-light projection AF signal. To do.

  The CPU 1 receives the reference AF signal and the non-projection AF signal output from the AFIC 10 and calculates (AFDATA−AFOFFDATA) to calculate the AF signal that is the final AF signal. In the case of a predetermined condition described later, AFDATA is calculated as the final AF signal. The calculated final AF signal is converted into a distance signal based on a predetermined calculation, and the distance signal is sent to the lens driving circuit 7. The lens driving circuit 7 causes the photographing lens 8 to perform a focusing operation based on the distance signal. The processing until the CPU 1 calculates the final AF signal and the conversion operation from the AF signal to the distance signal will be described later.

  Therefore, the CPU 1 functions as a calculation unit that calculates and acquires an AF signal, and as a distance calculation unit that calculates a distance from the AF signal and AFDATA. Further, the CPU 1 functions as a distance determination unit that determines that the distance to the subject is within a predetermined range based on AFDATA. Further, the CPU 1 functions as a luminance determination unit that determines that the luminance is equal to or lower than a predetermined luminance based on the external light luminance acquired by the photometric unit 9e that functions as a photometric unit. Further, since the CPU 1 inputs the AF signal obtained by light projection from the AFIC 10 and the AF signal obtained by non-light projection, it functions as a light projection distance measuring means and a non-light projection distance measuring means.

FIG. 3 shows a specific configuration diagram of the first signal processing circuit 11 and the integration circuit 15 of the AFIC 10. Note that the second signal processing circuit 12 also has a circuit configuration similar to that of the first signal processing circuit 11.
As shown in FIG. 3, the first signal processing circuit 11 receives the near-side signal I ₁ including the stationary light component I ₀ output from the PSD 5, removes the stationary light component I ₀ , and closes the near-side signal I _{0. 1} is output. The current (I ₁ + I ₀ ) output from the short distance side terminal of the PSD 5 is input to the negative input terminal of the operational amplifier 20 of the first signal processing circuit 11 through the PSDN terminal of the AFIC 10. The output terminal of the operational amplifier 20 is connected to the base terminal of the transistor 21, and the collector terminal of the transistor 21 is connected to the base terminal of the transistor 22. The collector terminal of the transistor 22 is connected to the negative input terminal of the operational amplifier 23, and the collector terminal is connected to the cathode terminal of the compression diode 24. Further, the cathode terminal of the compression diode 25 is connected to the + input terminal of the operational amplifier 23, and the first reference power supply 26 is connected to the anode terminals of the compression diodes 24 and 25.

  Further, a stationary light removal capacitor 27 is externally attached to the CHF terminal of the AFIC 10. The stationary light removal capacitor 27 is connected to the base terminal of the stationary light removal transistor 28 in the first signal processing circuit 11. The stationary light removal capacitor 27 and the operational amplifier 23 are connected via a switch 29, and on / off of the switch 29 is controlled by the CPU 1. The collector terminal of the stationary light removing transistor 28 is connected to the negative input terminal of the operational amplifier 20, and the emitter terminal of the transistor 28 is connected to the resistor 30 whose other end is grounded.

  On the other hand, in FIG. 3, the integration circuit 15 includes an integration capacitor 6 externally attached to the CINT terminal of the AFIC 10. The integrating capacitor 6 is connected to the output terminal of the arithmetic circuit 14 via the switch 60, connected to the constant current source 63 via the switch 62, and grounded via the switch 64. These switches 60, 62 and 64 are controlled by a control signal from the CPU 1.

FIG. 4 shows a specific configuration diagram of the clamp circuit 13 of the AFIC 10. As shown in FIG. 4, the clamp circuit 13 is provided with a comparator 37 that determines the level of the far side signal I ₂ . The + input terminal of the comparator 37 is connected to the collector terminal of the transistor 22 of the second signal processing circuit 12 and is connected to the input terminal of the arithmetic circuit 14 via the switch 38. On the other hand, the − input terminal of the comparator 37 is connected to the collector terminal of the transistor 51 and the cathode terminal of the compression diode 52 as well as the transistor 22 and the compression diode 24 connected to the + input terminal. To the input terminal of the arithmetic circuit 14.

  A clamp current source 41 is connected to the base terminal of the transistor 51. A constant current source 42a and a switch 43a are connected in series to the clamp current source 41, a constant current source 42b and a switch 43b are connected in series, a constant current source 42c and a switch 43c are connected in series, and a constant current source 42d and a switch 43d. Are connected in series, and the other ends of the switches 43 a to 43 d are connected to the base terminal of the transistor 51.

  For example, the constant current source 42a outputs a constant current value of 0.125 nA, the constant current source 42b outputs a constant current value of 0.25 nA, the constant current source 42c outputs a constant current value of 0.5 nA, and the constant current source 42d that outputs a constant current value of 1.0 nA is used.

  The switches 43a to 43d are opened and closed under the control of signals Q1 to Q4 output from the clamp level switching circuit 16. The clamp current source 41 inputs a clamp current, which is a sum of currents from the constant current sources corresponding to the closed switches, to the base terminal of the transistor 51. This clamp current becomes the base current of the transistor 51, and a collector potential corresponding to the magnitude is input to the − input terminal of the comparator 37. The clamp current is appropriately set when the distance measuring device is manufactured.

  Further, the output terminal of the comparator 37 is connected to the switch 39, and the output signal of the comparator 37 is inputted. Further, the output terminal of the comparator 37 is connected to the switch 38 via the inverter 40, and the output signal of the comparator 37 is inverted and inputted. Accordingly, the switches 38 and 39 are in a relationship that when one of them is turned on, the other is turned off by the output signal of the comparator 37.

The output signal of the comparator 37 is output from the AFIC 10 through the CMOUT terminal and input to the CPU 1. The output signal of the comparator 37 becomes a high potential signal when the far-side signal I ₂ inputted to the + input terminal is larger than the clamp signal I _C inputted to the − input terminal, and conversely inputted to the + input terminal. When the far side signal I ₂ is smaller than the clamp signal I _C input to the − input terminal, the signal becomes a low potential signal.

Therefore, the comparator 37 functions as an output signal detection unit that detects whether the output signal I _2C output from the clamp circuit 13 is the far side signal I ₂ or the clamp signal I _C.

  Next, the relationship between the external light noise and the AF signal in the distance measuring apparatus configured as described above will be described. FIG. 5 is an explanatory diagram showing the relationship between the external light luminance (external light noise) and the AF signal. In FIG. 5, the vertical axis represents the AF signal, and the horizontal axis represents the luminance value of the external light luminance. As shown in FIG. 5, the numerical value of the AF signal increases as the brightness indicated by the external light luminance increases (the luminance value increases). From this, it can be seen that the external light noise other than the reflected light from the subject greatly affects the AF signal.

  Next, the amount of increase in noise will be described. FIG. 6 is an explanatory diagram showing an increase in noise in an AF signal obtained by non-projection. Here, the non-projection distance measurement means that distance measurement is performed without performing light projection by the IRED 4. The distance measurement by light projection refers to distance measurement by projecting light onto a subject with the IRED 4.

  As shown in FIG. 6, the bold curve indicates AFOFFDATA. AFOFFDATA indicates the characteristics of the AF signal at each luminance when the distance is measured by non-light projection. A dotted horizontal line indicates TYPDATA. TYPDATA is a theoretical AF signal (AF signal obtained in a dark state) when there is no external light noise. Specifically, TYPDATA = a reference value that can be obtained by calculating AFOFFDATA + α (error) during adjustment. Then, an increase amount of the AF signal in the non-projection distance measurement can be obtained by an arithmetic expression (AFOFFDATA-TYPDATA) (non-projection AF signal). Here, α is an error, and is an adjustment value for giving a margin to TYPDATA.

The increase amount of the AF signal in the non-projection distance measurement is an AF signal that can be obtained by the external light luminance. AFDATA is an AF signal (reference AF signal) obtained by projecting the subject with the IRED 4. Therefore,
AF signal = AFDATA− (AFOFFDAT−TYPDATA) (1)
Thus, an AF signal (final AF signal) from which external light noise due to external light luminance is removed can be calculated. If a distance signal is calculated based on the AF signal calculated here, a more accurate distance can be calculated.

  In a normal camera, when calculating the distance signal from the AF signal, if the value of the AF signal is smaller than a predetermined threshold, it is determined that the subject is longer than the distance at which proper focus control can be performed, and the subject is Focus control is performed assuming that the camera is at an infinite position. If it is equal to or greater than the threshold value, the AF signal is converted into a distance signal, and the lens is driven according to the distance signal to perform focus control.

  Here, an outline when converting the AF signal into the distance signal will be described. FIG. 7 is an explanatory diagram of conversion from an AF signal to a distance signal. In the graph shown in FIG. 7, the horizontal axis is the reciprocal (1 / L) of the distance L to the subject, the left vertical axis is the AF signal, and the right vertical axis is the distance signal. This graph also shows the relationship between the distance L and the AF signal and the relationship between the distance L and the distance signal. In particular, the AF signal for the distance L2 is y2, the distance signal is x2, and the AF signal for the distance L3 is y3, the distance signal is x3, the AF signal for the distance L4 is y4, the distance signal is x4, the AF signal for the distance L5 is y5, and the distance signal is x5 (however, L2> L3> L4> L5 ing). When the AF signal is determined in this way, the distance and the distance signal are uniquely determined.

  Here, in the range of distance L ≦ L4 and the range of distance L> L4, the AF signal has a substantially linear relationship with the reciprocal (1 / L) of the distance L, and the distance signal in the entire range of the distance L. Is substantially linear with respect to the reciprocal of the distance L (1 / L). Therefore, in the range of distance L ≦ L4 and the range of distance L> L4, the relationship between the AF signal and the distance signal is also substantially linear.

The signal characteristics of the AF signal change in the range of distance L ≦ L4 and the range of distance L> L4. The far side signal I ₂ is mainly output as the output signal of the clamp circuit 13 in the range of distance L ≦ L4. On the other hand, the clamp signal I _C is mainly output as the output signal of the clamp circuit 13 in the range of distance L> L4.

  As described above, the distance signal is calculated from the AF signal obtained based on the AF signal obtained by the distance measurement by the IRED 4 and the AF signal obtained by the non-projection, and the focus control is performed based on the calculated distance signal. Can do. Below, the detailed specific example is demonstrated.

  First, the operation of the distance measuring apparatus according to the present embodiment will be described. FIG. 8 is a flowchart showing the operation of the distance measuring apparatus according to the present embodiment. This flowchart is operated by the CPU 1.

First, distance measurement using the IRED 4 is performed (S101). Specifically, infrared light is emitted toward the subject by the IRED 4, and reflected light from the subject is received by the PSD 5. Then, a signal including stationary light is output from the PSD 5 based on the reflected light. The first signal has received the signal processing circuit 11 and the second signal processing circuit 12 outputs the respective near-side signal I ₁ and the far-side signal I ₂ by removing the ambient light. Then, by integrating the output ratio of the near side signal I ₁ and the far side signal I ₂ , AFDATA (reference AF signal) is calculated, and a distance signal is calculated.

Next, distance measurement by non-light projection is performed (S102). Specifically, the external light is received by the PSD 5 without the infrared light being projected by the IRED 4. Then, a signal including stationary light is output from the PSD 5 based on the reflected light. The first signal processing circuit 11 and the second signal processing circuit 12 that have received this signal remove the stationary light and output a near-side signal I ₁ and a far-side signal I ₂ , respectively. Then, by integrating the output ratio of the near-side signal _{I 1} and the far-side signal _{I 2,} AFOFFDATA is calculated.

  Then, it is determined whether or not AFDATA obtained in S101 is a predetermined value or less (S103). If it is determined that AFDATA is equal to or less than a predetermined value, that is, if it is determined that the distance to the subject is equal to or greater than a predetermined distance, an arithmetic expression (AFOFFDATA-TYPDATA) (non-projection AF signal) is calculated. Is done. Then, an AF signal (final AF signal) is calculated by the above equation (1) (S105).

When it is determined that AFDATA is greater than a predetermined value, that is, when it is determined that the distance to the subject is smaller than a predetermined distance,
AF signal = AFDATA (2)
Thus, an AF signal is calculated (S104).

  It is determined whether or not the calculated AF signal is larger than a threshold value indicating whether or not the subject is at an infinite position (S106). Here, when it is determined that the AF signal is larger than the threshold value, a distance signal is calculated based on the AF signal (S106). Then, the lens is driven based on the distance signal, focusing control is performed (S107), and photographing processing is performed by opening and closing the shutter (S108).

  If it is determined in S106 that the AF signal is equal to or smaller than the threshold value, it is determined that the subject is at the infinity position (S109), and focusing control corresponding to the infinity position is performed (S110). Then, photographing based on the focusing control in S108 or S110 is performed (S111).

  In this way, when calculating the AF signal, if the distance to the subject is longer than a predetermined distance, an AF signal (final AF signal combination) from which noise due to external light luminance has been removed is calculated, and this AF signal is calculated. Since the distance is calculated based on the above, an accurate distance can be calculated. Since the AF signal has a small value from which noise is removed, the threshold value can be determined for the AF signal having the small value, and the threshold value can be set to a small value. When the distance to the subject is equal to or less than a predetermined distance, AFDATA is used as an AF signal, the distance is calculated based on the AF signal, and focusing control according to the distance can be performed.

  Next, the operation of the first modification of the distance measuring device will be described. The configuration is the same as the configuration of the present embodiment described above. FIG. 9 is a flowchart showing the operation of the distance measuring apparatus according to the first modification. This flowchart is operated by the CPU 1.

First, distance measurement by IRED 4 is performed (S201). Specifically, infrared light is emitted toward the subject by the IRED 4, and reflected light from the subject is received by the PSD 5. Then, a signal including stationary light is output from the PSD 5 based on the reflected light. The first signal processing circuit 11 and the second signal processing circuit 12 that have received this signal remove the stationary light and output a near-side signal I ₁ and a far-side signal I ₂ , respectively. Then, by integrating the output ratio of the near side signal I ₁ and the far side signal I ₂ , AFDATA (reference AF signal) is calculated, and a distance signal is calculated. Then, it is determined whether AFDATA obtained in S101 is equal to or less than a predetermined value (S202).

Here, if it is determined that AFDATA is equal to or less than a predetermined value, that is, if it is determined that the distance to the subject is equal to or greater than a predetermined distance, distance measurement by non-light projection is performed (S203). Specifically, the external light is received by the PSD 5 without the infrared light being projected by the IRED 4. Then, a signal including stationary light is output from the PSD 5 based on the reflected light. The first signal processing circuit 11 and the second signal processing circuit 12 that have received this signal remove the stationary light and output a near-side signal I ₁ and a far-side signal I ₂ , respectively. Then, by integrating the output ratio of the near-side signal _{I 1} and the far-side signal _{I 2,} AFOFFDATA is calculated. Based on the calculated AFOFFDATA, an arithmetic expression (AFOFFDATA−TYPDATA) (non-projection AF signal) is calculated. Thereafter, an AF signal (final AF signal) is calculated by the above equation (1) (S204).

  If it is determined that AFDATA is greater than a predetermined value, that is, if it is determined that the distance to the subject is smaller than a predetermined distance, an AF signal is calculated by the above equation (2). (S205).

  It is determined whether or not the calculated AF signal is larger than a threshold value indicating whether or not the subject is at an infinite position (S206). Here, if it is determined that the AF signal is greater than the threshold value, a distance signal is calculated based on the AF signal (S206). Then, the lens is driven based on the distance signal, focusing control is performed (S207), and photographing processing is performed by opening and closing the shutter (S208).

  If it is determined in S206 that the AF signal is equal to or smaller than the threshold value, it is determined that the subject is at the infinity position (S209), and focusing control corresponding to the infinity position is performed (S210). Then, photographing based on the focusing control in S208 or S210 is performed (S211).

  Thus, in accordance with AFDATA, it is determined whether or not to perform distance measurement by non-light projection, and when AFADATA that does not require distance measurement by non-light projection is obtained, distance measurement by non-light projection is obtained. Therefore, efficient processing can be realized without performing useless processing.

  Furthermore, the operation of the distance measuring apparatus according to the second modification will be described. The configuration is the same as the configuration of the present embodiment described above. FIG. 10 is a flowchart showing the operation of the distance measuring apparatus according to the second modification. This flowchart is operated by the CPU 1.

First, distance measurement by IRED 4 is performed (S301). Specifically, infrared light is emitted toward the subject by the IRED 4, and reflected light from the subject is received by the PSD 5. Then, a signal including stationary light is output from the PSD 5 based on the reflected light. The first signal processing circuit 11 and the second signal processing circuit 12 that have received this signal remove the stationary light and output a near-side signal I ₁ and a far-side signal I ₂ , respectively. Then, by integrating the output ratio of the near side signal I ₁ and the far side signal I ₂ , AFDATA (reference AF signal) is calculated, and a distance signal is calculated.

Next, photometry is performed by the photometry unit, and a luminance value that is external light luminance is acquired (S302). Here, when the acquired luminance value is larger than the predetermined luminance, distance measurement by non-light projection is performed (S304). Specifically, external light is received by the PSD 5 without performing infrared light projection by the IRED 4. Then, a signal including stationary light is output from the PSD 5 based on the reflected light. The first signal processing circuit 11 and the second signal processing circuit 12 that have received this signal remove the stationary light and output a near-side signal I ₁ and a far-side signal I ₂ , respectively. Then, by integrating the output ratio of the near-side signal _{I 1} and the far-side signal _{I 2,} AFOFFDATA is calculated. Based on the calculated AFOFFDATA, an arithmetic expression (AFOFFDATA−TYPDATA) (non-projection AF signal) is calculated. Then, an AF signal (final AF signal) is calculated using the above equation (1) (S305).

  When it is determined that the luminance value acquired in S303 is equal to or less than the predetermined value, an AF signal is calculated by the above equation (2) (S306).

  Next, it is determined whether or not the calculated AF signal is larger than a threshold value indicating whether or not the subject is at an infinite position (S307). Here, if it is determined that the AF signal is greater than the threshold value, a distance signal is calculated based on the AF signal (S308). Then, the lens is driven based on the distance signal, focusing control is performed (S309), and photographing processing is performed by opening and closing the shutter (S312).

  If it is determined in S106 that the AF signal is equal to or smaller than the threshold value, it is determined that the subject is at the infinity position (S310), and focusing control corresponding to the infinity position is performed (S311). Then, photographing based on the focusing control in S309 or S311 is performed (S312).

  In this way, it is determined whether or not to perform distance measurement by non-light projection based on the result of light measurement by the light metering unit. Efficient processing can be realized without performing it.

  Next, detailed processing when performing distance measurement by non-light projection in the above-described embodiment (including the first modification and the second modification) will be described. The distance measurement by non-light projection does not require high accuracy compared with the distance measurement by IRED4. Therefore, it is conceivable to multiply the numerical value obtained by non-projection distance measurement by a predetermined coefficient, with the number of distance measurements by non-projection distance measurement being smaller than the number of distance measurements using IRED4. FIG. 11 is a timing chart showing the number of times of distance measurement and the integration time in distance measurement using the IRED 4. FIG. 12 is a timing chart showing the number of times of distance measurement and integration time in non-projection distance measurement.

  As shown in FIG. 11, in the distance measurement using a normal IRED 4, the integration time is set to 26 μsec. In this integration time, 120 distance measurements are performed at intervals of 352 μsec. On the other hand, the distance measurement by non-projection shown in FIG. 12 takes twice as much time as the normal distance measurement with an integration time of 52 μsec. Conversely, the number of distance measurements is 30, which is reduced to a quarter. The total integration time in normal distance measurement is 26 μsec × 120 times = 3120 μsec, and the total registration time in distance measurement by non-light projection is 52 μsec × 30 times = 1560 μsec. Since the total integration time in the distance measurement by non-light projection is half of the integration time using the IRED 4, the total integration time by the non-light projection distance measurement is multiplied by 2 to obtain the total integration time. Make time the same. In the distance measurement using the IRED4 and the distance measurement by the non-light projection, the weights are made the same by making the total integration time the same, and obtained by the distance measurement using the IRED4 and the distance measurement by the non-light projection respectively. AF signals can be compared with each other.

  In this way, in the distance measurement by non-light projection, the integration time is doubled and the coefficient 2 is multiplied by the integration time, thereby reducing the number of distance measurement by a quarter and reducing the number of distance measurement. It is possible to use the same weighting for the distance measurement using the light projection and the distance measurement using the IRED 4, and to shorten the distance measurement time for the non-light projection.

  Based on the same idea, by making the integration time the same and multiplying the multiplication coefficient by a times (for example, 4 times), the number of distance measurements can be reduced to 1 / a (for example, 1/4). The distance time can be shortened. Also, by simply multiplying the integration time by b times (for example, 4 times) without multiplying by a coefficient, the number of distance measurements can be reduced to 1 / b (for example, 1/4), and the distance measurement time is shortened. be able to.

  The function and effect of the distance measuring device described above will be described. According to this distance measuring apparatus, (AFOFFDATA-TYPEDATA) (non-projection AF) acquired without performing projection with IRED4 from AFDATA (reference AF signal) acquired by projecting onto a subject with IRED4. The distance can be calculated based on the AF signal (final AF signal) obtained by subtracting the signal. The acquired AF signal is obtained by removing external light noise and is close to the design value, so that an accurate distance can be calculated.

  Further, when the acquired AF signal indicates a predetermined threshold value or less, since the subject is far away, photographing in the infinity mode is required. In this case, since the information conventionally includes external light noise, it is necessary to set the threshold value higher by the amount of external light noise. However, in the present invention, since the ambient light noise can be determined based on the AF signal from which the external light noise has been removed in advance, the threshold for the infinity mode can be set low, and the accurate distance can be set over a long distance. Can do.

  Here, a comparative example of the AF signal corrected by the distance measuring apparatus according to the present embodiment, the AF signal acquired without being corrected, and the design value of the AF signal will be described. FIG. 13 is an explanatory diagram showing the relationship between the AF signal and the distance. In FIG. 13, the dotted line is a characteristic indicated by the design value of the AF signal (without external light noise), the thin solid line is the characteristic of the AF signal at high luminance (with external light noise), and the thick solid line is the characteristic at high luminance. The characteristic of the corrected AF signal (with external light noise) is shown. The vertical axis in FIG. 13 is the AF signal, and the horizontal axis is the reciprocal of the distance to the subject.

  The characteristic indicated by the design value of the AF signal indicated by the dotted line indicates that the reflected light from the subject becomes weak when the subject is farther than a predetermined distance, so that the AF signal is lowered according to the reflected light. The thin solid line shows the characteristic of the AF signal (with external light noise) at the time of high luminance until the middle, but the characteristic similar to the design value is obtained, but when the control by the clamping means is performed, the characteristic is gentler than the design value ( It is low with a high slope. The characteristic indicated by this inclination is an AF signal including external light noise, and thus has a value higher than the design value.

  The thick solid line shows the characteristic of the AF signal (with external light noise) that has been corrected at the time of high luminance, such that an AF signal that becomes lower according to the distance is output when the clamp means is controlled. It has become. Since the characteristic is based on the AF signal excluding the external light luminance, it can be seen that the characteristic is closer to the design value than the characteristic indicated by the thin line.

  Therefore, the distance measuring apparatus according to the present embodiment reduces external light noise by subtracting (AFOFFDATA-TYPDATA) obtained by distance measurement by non-light projection without using IRED4 from AFDTA obtained by distance measurement using IRED4. Can be obtained, and an AF signal close to the design value can be obtained. Therefore, the distance can be measured based on this AF signal. In addition, the threshold for determining whether or not the subject is at an infinite position can be made appropriate, and can be made smaller. That is, it is possible to determine the distance to the subject that needs the focus control corresponding to the infinity position with an appropriate threshold without taking the outside light noise into consideration and making the threshold large.

  Next, a description will be given while comparing the relationship between the distance signal calculated based on the AF signal and the distance corrected and not corrected. FIG. 14 is an explanatory diagram showing the relationship between the distance signal and the distance when the external light noise is low (low luminance). As shown in FIG. 14, the vertical axis represents the distance signal converted from the AF signal, and the horizontal axis represents the reciprocal of the distance. The dotted line indicates the characteristics of the distance signal design value (no external light noise) (partially overlaps the thick solid line), and the thin solid line indicates the characteristics of the uncorrected distance signal when the external light noise is low (one The thick solid line shows the characteristics of the distance signal with correction when the external light noise is small. The characteristic of the distance signal indicated by a thin solid line is that which has decreased to the lowest level at a predetermined distance (a point of about 1 / L = 0.00010 on the graph). Further, the characteristic of the distance signal indicated by a thick solid line is the lowest level by a threshold value for determining that the subject is at an infinite position at a predetermined distance (on the graph and at a point of 1 / L = 0.00005). It has been lowered to. In other words, the distance signal indicated by a thick solid line, that is, the characteristic of the distance signal when correction is performed, has a characteristic that approximates the design value, and it is possible to accurately measure the distance even for a subject at a farther distance. I understand that I can do it.

  As a description similar to FIG. 14, the relationship between the distance signal and the distance when there is a lot of external light noise (high brightness) will be described. FIG. 15 is an explanatory diagram showing the relationship between the distance signal and the distance when there is a lot of external light noise. As shown in FIG. 15, the vertical axis represents the distance signal converted from the AF signal, and the horizontal axis represents the reciprocal of the distance. The dotted line shows the characteristics of the distance signal design value (no external light noise), the thin solid line shows the characteristics of the distance signal without correction when there is a lot of external light noise, and the thick solid line shows the correction when there is a lot of external light noise The characteristics of the distance signal are shown. The characteristic of the distance signal indicated by a thin solid line shows a characteristic having a slope at a position slightly higher than the design value due to the influence of external light noise (partly overlapping the thick solid line). Then, at a predetermined distance (approximately 1 / L = 0.00004 on the graph), the threshold is lowered to the lowest position by a threshold value for determining that the subject is at the infinity position. In addition, the characteristic of the distance signal indicated by a thick solid line forms a slope that approaches the design value at a predetermined distance (on the graph and at a point of 1 / L = 0.00010), and remains at the lowest position in the distance signal. It has changed. In other words, the distance signal indicated by a thick solid line, that is, the characteristic of the distance signal when correction is performed has a characteristic approximate to the design value, so that the distance can be accurately measured even for a subject at a far distance. It shows what you can do.

  From the above, since the AF signal calculated by subtracting (AFOFFDATA-TYPDATA) from AFDATA can obtain characteristics close to the design value, the distance to the subject can be accurately calculated.

It is a perspective view which shows the external appearance of the front side of the camera 9 provided with the distance measuring device which concerns on this embodiment. It is a block block diagram of a distance measuring device. 3 is a specific configuration diagram of a first signal processing circuit 11 and an integration circuit 15 of the AFIC 10. FIG. 3 is a specific configuration diagram of a clamp circuit 13 of the AFIC 10. FIG. It is explanatory drawing which shows the relationship between external light brightness | luminance (external light noise) and AF signal. It is explanatory drawing which shows the increase amount of external light noise. It is explanatory drawing of conversion from AF signal to a distance signal. It is a flowchart which shows operation | movement of the distance measuring device by this embodiment. It is a flowchart which shows operation | movement of the ranging device by a 1st modification. It is a flowchart which shows operation | movement of the ranging apparatus by a 2nd modification. It is a timing chart which shows the frequency | count of ranging and integration time when performing ranging using IRED4. It is a timing chart at the time of extending the number of times of distance measurement and integration time in non-projection distance measurement. It is explanatory drawing which shows the relationship between AF signal and distance. It is explanatory drawing which shows the relationship between the distance signal when external light is low-intensity, and distance. It is explanatory drawing which shows the relationship between the distance signal when external light is high-intensity, and distance.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... CPU, 2 ... EEPROM, 3 ... Driver, 4 ... IRED, 5 ... PSD, 6 ... Integral capacitor, 7 ... Lens drive circuit, 8 ... Photographing Lens, 9 ... Camera, 9a ... Release button, 9b ... Lens barrel, 9c ... Viewfinder, 9d ... Strobe light emitting part, 9e ... Photometric part, 9f ... Shutter, 11 ... Signal processing circuit, 12 ... Signal processing circuit, 13 ... Clamp circuit, 14 ... Arithmetic circuit, 15 ... Integration circuit, 16 ... Clamp level switching circuit, 20 ... Operational amplifier 21 ... transistor, 22 ... transistor, 23 ... op amp, 24 ... compression diode, 25 ... compression diode, 26 ... reference power supply, 27 ... stationary light removal capacitor, 28 ... Transis 28 ... Steady light removing transistor, 29 ... Switch, 30 ... Resistance, 37 ... Comparator, 38 ... Switch, 39 ... Switch, 40 ... Inverter, 41 ... Clamp current source, 42a ... constant current source, 42b ... constant current source, 42c ... constant current source, 42d ... constant current source, 43a ... switch, 43b ... switch, 43c ... Switch, 43d ... Switch, 51 ... Transistor, 52 ... Compression diode, 60 ... Switch, 62 ... Switch, 63 ... Constant current source.

Claims (5)

A light projecting means for irradiating the subject with light;
A light receiving means for receiving external light including reflected light of the light emitted by the light projecting means, and outputting a light reception signal corresponding to the distance to the subject;
Projection distance measuring means for acquiring a reference AF signal generated based on a light reception signal output by the light reception means by irradiating light to a subject by the light projection means;
Non-light-projecting distance measuring means for obtaining a non-light-projecting AF signal generated in a non-light-projecting state based on a light-receiving signal output from the light-receiving means without irradiating the subject with light by the light-projecting means When,
Arithmetic means for obtaining a final AF signal by subtracting the non-projection AF signal obtained by the non-projection distance measurement means from the reference AF signal obtained by the projection distance measurement means;
Distance calculating means for calculating the distance to the subject based on the final AF signal acquired by the calculating means;
Ranging device comprising. Distance determining means for determining whether the distance to the subject is within a predetermined distance based on the reference AF signal acquired by the light projection distance measuring means,
The distance calculation means, when the determination means determines that the distance to the subject is within a predetermined distance, without operating the non-light-projecting distance measurement means, the final obtained by the calculation means The distance to the subject is calculated based on the reference AF signal acquired by the light projection distance measuring means without calculating the distance to the subject based on the AF signal. Ranging device. A photometric means for measuring ambient light brightness;
Brightness determination means for determining whether or not the brightness measured by the photometry means is equal to or less than a predetermined brightness,
The distance calculating means does not operate the non-light-projecting distance measuring means when the brightness determining means determines that the brightness is equal to or lower than the predetermined brightness, and based on the final AF signal acquired by the calculating means. 3. The distance measurement according to claim 1, wherein the distance to the subject is calculated based on a reference AF signal acquired by the light projection distance measuring means without calculating the distance to the subject. Distance device. The light projection distance measuring means obtains N pieces of numerical information indicating the amount of reflected light from the subject by irradiating the subject with light N times at predetermined intervals, and the obtained N amounts of light are obtained. The reference AF signal is acquired by accumulatively storing the numerical information indicating, and the non-light-projecting distance measuring unit acquires and acquires M (M <N) numerical information indicating the amount of light of the subject at predetermined intervals. Multiplying signal information obtained by accumulating information indicating M light amounts by a predetermined coefficient to obtain a non-projection AF signal;
The distance measuring device according to any one of claims 1 to 3, wherein: The light projection distance measuring means further irradiates the subject with light at least once for a predetermined time X, thereby providing numerical information indicating the amount of reflected light from the subject at the predetermined time X. Obtaining the reference AF signal by obtaining a predetermined time;
The non-light-projecting distance measuring means further acquires numerical information indicating the light amount of the subject for a predetermined time Y (Y> X) per time, and accumulates information indicating the acquired light amount. Multiplying signal information by a predetermined coefficient to obtain the non-projection AF signal;
The distance measuring device according to claim 4.

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