JP3796324B2 - Ranging device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention obtains a distance from a light receiving sensor to an object based on a shift amount of an image forming position of the object in two images obtained by imaging one object using a pair of light receiving sensors. The present invention relates to a distance measuring apparatus.
[0002]
[Prior art]
Conventionally, a single object is imaged using a pair of line sensors such as a CCD, the amount of deviation of the image forming position of the object in the two obtained images is obtained, and the distance from the amount of deviation to the object is determined. The distance measuring device to be obtained is well known.
[0003]
FIG. 4 shows a conventional ranging process sequence in such a ranging apparatus.
[0004]
First, when a predetermined switch of the camera is operated, a distance measurement process is started in step S401, and charges remaining in the line sensor which is a light receiving sensor and its peripheral circuits are cleared in step S402.
[0005]
In step S403, a threshold value of the signal level of the image signal accumulated in the line sensor (hereinafter referred to as “comparative level (Scmp)”) is set. This is for ending the charge accumulation operation in the line sensor when the signal level of the image signal accumulated in the line sensor exceeds the comparison level Scmp.
[0006]
In step S404, the longest time (Tmax) during which the line sensor continues to accumulate the charge of the image signal is set. This is to stop the charge accumulation operation in the line sensor after the elapse of the time Tmax set in step S404 when an image signal equal to or higher than the comparison level Scmp set in step S403 cannot be obtained. .
[0007]
Charge accumulation of the image signal is started from step S405, and it is determined whether or not the signal level of the image signal S accumulated in the line sensor in step S406 exceeds the comparison level Scmp set in step S403. If the signal level of the accumulated image signal S exceeds the comparator level Scmp, the process proceeds to step S408 to end the charge accumulation operation, and if not, the process proceeds to step S407.
[0008]
In step S407, it is determined whether or not the time T elapsed since the start of the charge accumulation operation is within the time Tmax set in step S404. If the time T is within the time Tmax, the accumulation operation is continued, and the time Tmax has passed. Then, the process proceeds to step S408, and the accumulation operation is terminated.
[0009]
After completing the charge accumulation operation in step S408, in step S409, the difference (Dif (Smax, Smin)) between the maximum signal level (Smax) and the minimum signal level (Smin) of the image signal obtained from the line sensor is predetermined. Contrast determination is performed to determine whether or not the value is greater than or equal to the value. If the difference between the maximum and minimum signal levels of the image signal is not greater than or equal to a predetermined value due to this contrast determination, it is difficult to determine the amount of deviation between the two images obtained by the pair of line sensors, for example, by detecting corresponding points. Therefore, without using the image signal obtained by the charge accumulation operation, the designated distance is output as a result in step S412, and the distance measuring process is terminated.
[0010]
If it is determined in step S409 that the difference between the maximum and minimum signal levels of the image signals is greater than or equal to a predetermined value, the amount of deviation between the two image signals is obtained in step S410, and from the amount of deviation to the subject in step S411. The distance measurement process is obtained and the distance measurement process is terminated.
[0011]
[Problems to be solved by the invention]
However, since the contrast determination is always performed in the above-described conventional example, when a sufficient image signal is obtained, the distance measurement process takes extra time, which causes a release time lag.
[0012]
The present invention has been made in view of the above-described problems. At the time of distance measurement, the signal level of the image signal accumulated in the sensor within a predetermined time exceeds the preset value, so that the charge in the light receiving sensor is increased. When the accumulation operation is completed, it is determined that the signal level difference between the image signals is sufficient and the contrast is not determined. Only when the light receiving element cannot obtain an image signal having a sufficient signal level. An object of the present invention is to reduce the release time lag while maintaining the distance measurement accuracy by performing the contrast judgment for confirming the difference between the maximum signal level and the minimum signal level of the image signal.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, the distance measuring apparatus of the present invention photoelectrically converts incident light from a subject by a pair of light receiving sensors, accumulates electric charges, outputs them as image signals, and the signal level of the output image signals is A distance measuring device that terminates charge accumulation when it exceeds a predetermined value and obtains a distance to a subject based on an output image signal, based on image signals output from the pair of light receiving sensors A calculation unit that performs a calculation for determining the contrast of the image signal, and a control unit that omits the calculation by the calculation unit when the time required for charge accumulation is within a predetermined time.
[0014]
In addition, the pair of light receiving sensors according to the present invention photoelectrically converts incident light from a subject, accumulates charges, and outputs them as an image signal. When the signal level of the output image signal exceeds a predetermined value, According to the distance measuring method for ending accumulation and obtaining the distance to the subject based on the output image signal, when the time required for charge accumulation is equal to or longer than a predetermined time, the image signal is based on the output image signal. When the time required for charge accumulation is within a predetermined time, the distance to the subject is determined based on the output image signal without performing the calculation.
[0015]
Further, the calculation for judging the contrast of the image signal in the above-described configuration, a calculation for obtaining a difference between the maximum signal level and the minimum signal level of the images signals.
[0016]
According to the above configuration, when the charge accumulation operation in the light receiving sensor is terminated because the signal level of the image signal accumulated in the sensor within a predetermined time exceeds a preset value, the signal level difference of the image signal Therefore, the difference between the maximum signal level and the minimum signal level of the image signal can be determined only when the light receiving element cannot obtain an image signal having a sufficient signal level. By performing the contrast judgment for confirming, it is possible to shorten the release time lag while maintaining the distance measurement accuracy.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block diagram of a camera system using the distance measuring apparatus of the present invention.
[0018]
Reference numeral 1 denotes a microprocessor (MPU) having an A / D converter, an arithmetic circuit, and a storage device (not shown). 2 is a power switch (MAIN) for turning on / off the power of the camera, and 3 is a switch (SW1) for starting a release operation. When the switch 3 is closed, ranging, photometry, and the like are performed. Reference numeral 4 denotes a switch (SW2). When the switch 3 is closed while the switch 3 is closed, exposure or the like is performed on the film.
[0019]
Reference numeral 5 denotes a zoom switch (TELE) for switching the focal length of the camera to the telephoto side, and reference numeral 6 denotes a zoom switch (WIDE) for switching the focal length of the camera to the wide angle side. Reference numeral 7 denotes a photometric sensor (ALS) for measuring the luminance of the subject. The exposure time is obtained based on the luminance obtained by this sensor.
[0020]
A distance measuring unit 24 includes a distance measuring sensor 9 (AFS), a light emitting element 10 such as an IRED, and a distance measuring element control unit (AFC) 8 for controlling them. The light emitting element 10 is controlled in light emission time and light emission timing by the distance measuring element control unit 8. Further, although not shown in FIG. 1, the distance measuring sensor 9 is constituted by a pair of line sensors.
[0021]
A shutter control unit (SHC) 11 opens a shutter (not shown) for a predetermined time to expose a film (not shown). Reference numeral 12 denotes a feeding drive unit (FM) for winding up an exposed film (not shown) by a predetermined amount. Reference numeral 13 denotes a lens barrel drive unit (ZM) for driving a lens barrel (not shown) in order to change the focal length of the camera. Reference numeral 14 denotes a focus driving unit (LM) for controlling a focus adjusting lens (not shown) based on subject distance information obtained from the distance measuring unit 24.
[0022]
Next, the principle of distance measurement used in the camera system having the above configuration will be described with reference to FIG. FIG. 2 is a schematic diagram for explaining the principle of the distance measuring system of the present invention.
[0023]
The light emitting element 10 projects light toward the subject 15 in accordance with a control signal from the distance measurement control unit (AFC) 8 shown in FIG. The projected light is reflected by the subject 15 and is incident on a pair of light receiving sensors 9a and 9b constituted by a CCD or the like. Reference numerals 16 and 17 schematically illustrate how light incident on the light receiving sensors 9a and 9b is converted into an electrical signal by photoelectric conversion and output as an image signal.
[0024]
Since the light emitting element 10 and the light receiving sensors 9a and 9b are arranged on the same line, the incident angles of the reflected light reflected by the subject 15 and entering the light receiving sensors 9a and 9b are different from each other. For this reason, since the image forming position of the subject in the two images obtained from the light receiving sensors 9a and 9b differs depending on the subject distance, it is possible to detect the shift amount of the subject image. That is, the distance to the subject can be obtained based on the amount of deviation of the image formation position of the subject image.
[0025]
FIG. 3 is a flowchart showing the distance measuring operation of the present invention.
[0026]
First, when the predetermined switch 3 (SW1) of the camera is closed, the ranging process is started in step S301. In step S302, the charge remaining in the light receiving sensor and its peripheral circuits is cleared.
[0027]
In step S303, a comparison level Scmp, which is a threshold value of the signal level of the image signal accumulated in the line sensors 9a and 9b, is set. This is for ending the charge accumulation operation in the line sensors 9a and 9b when the signal level of the image signal received by the light receiving sensor exceeds the comparison level Scmp, and is obtained as a charge accumulation result. What is necessary is just to set arbitrarily in the range which line sensor 9a, 9b does not saturate so that the maximum signal level of an image signal may become suitable for detecting the shift | offset | difference amount of the to-be-photographed image mentioned later.
[0028]
In step S304, the longest time (Tmax) during which the line sensors 9a and 9b continue to accumulate the charge of the image signal is set. This is to stop the charge accumulation operation of the image signal after the time Tmax set in step S304 elapses when an image signal equal to or higher than the comparison level Scmp set in step S303 cannot be obtained.
[0029]
In step S305, charge accumulation of the image signal is started. In step S306, it is determined whether or not the signal level of the image signal S is equal to or higher than the comparison level Scmp set in step S303. If it is equal to or higher than the comparison level Scmp, it is determined that an image signal having a signal level sufficient to obtain a distance measurement value (image shift amount) is obtained, and the process proceeds to step S308. It is determined that an image signal is not obtained, and charge accumulation is continued.
[0030]
If it is determined in step S306 that the signal level of the image signal S is lower than the comparator level Scmp, the process proceeds to step S307, and the time T that has elapsed since the start of the charge accumulation operation in step S305 is within the time Tmax set in step S304. If it is within the time Tmax, the accumulation operation is continued and the process returns to step S306. If the elapsed time T has passed the time Tmax, the process proceeds to step S308, and the accumulation operation is terminated even if an image signal having a signal level sufficient to obtain the shift amount (distance value) of the subject image is not accumulated.
[0031]
After completing the charge accumulation of the image signal in step S308, whether the time Tend required for the charge accumulation in step S309 is equal to or longer than the time Tmax set in step S304, that is, the time Tmax elapses when the charge accumulation operation ends. It is determined whether the power storage operation is terminated or whether a sufficient charge of the image signal is accumulated. If Tend> = Tmax, that is, if time-out occurs, the process proceeds to step S310. If not, the image signal having a sufficient signal level is accumulated, and the process proceeds to step S311.
[0032]
On the other hand, the image signal obtained by stopping the charge accumulation operation after the elapse of time Tmax is a relatively dark image having a maximum signal level equal to or lower than the comparison level Scmp, and therefore, the contrast of the image, that is, the brightness in the image. The difference in height may be small. If the contrast is low, it is difficult to determine the amount of deviation (distance value) of the subject image. Therefore, in step S310, the contrast of the obtained image signal is determined, and the difference between the maximum signal level Smax and the minimum signal level Smin ( It is determined whether or not Dif (Smax, Smin)) is greater than a predetermined value. If it is determined that the signal level difference is smaller than the predetermined value, that is, the contrast is low, the process proceeds to step S313, the designated distance data is output as a distance measurement result, and the distance measurement operation is terminated. If it is determined that the signal level difference is greater than or equal to the predetermined value, that is, if it is determined that the contrast for obtaining the amount of deviation of the subject image is sufficiently high, the process proceeds to step S311.
[0033]
In step S311, the amount of deviation of the subject image signal in the two images is obtained. In step S312, the distance to the subject is obtained based on the amount of deviation, and the distance measuring operation is terminated.
[0034]
In the present invention, a pair of line sensors using a CCD is used as a light receiving element. However, a plurality of silicon photodiodes (SPDs) and skim CCDs arranged in a pair are used. Also good. Further, the configuration is not limited to the line sensor, and an area sensor arranged on the same plane can be used.
[0035]
Further, the present invention may be applied to a system constituted by a plurality of devices (for example, a host computer and a camera head) or to an apparatus (for example, a camera) composed of one device.
[0036]
Another object of the present invention is to supply a storage medium recording a program code of software for realizing the functions of the above-described embodiments to a system or apparatus, and the computer (or CPU or MPU) of the system or apparatus stores the storage medium. Needless to say, this can also be achieved by reading and executing the program code stored in the.
[0037]
In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention.
[0038]
As a storage medium for supplying the program code, for example, a floppy disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.
[0039]
Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an OS (operating system) operating on the computer based on the instruction of the program code. It goes without saying that a case where the function of the above-described embodiment is realized by performing part or all of the actual processing and the processing is included.
[0040]
Further, after the program code read from the storage medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function expansion is performed based on the instruction of the program code. It goes without saying that the CPU or the like provided in the board or the function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.
[0041]
【The invention's effect】
As described above, according to the present invention, the charge accumulation operation in the light receiving sensor is terminated when the signal level of the image signal accumulated in the sensor within a predetermined time exceeds a preset value during distance measurement. In this case, it is determined that the signal level difference between the image signals is sufficient and the contrast is not determined, and only when the light receiving element cannot obtain an image signal having a sufficient signal level, By making a contrast judgment that confirms the difference between the maximum signal level and the minimum signal level, the release time lag can be shortened while maintaining the distance measurement accuracy.
[0042]
[Brief description of the drawings]
FIG. 1 is a block diagram of a camera system using a distance measuring device of the present invention.
FIG. 2 is a schematic diagram for explaining the principle of the distance measuring system of the present invention.
FIG. 3 is a flowchart for explaining a distance measuring operation of the present invention.
FIG. 4 is a flowchart for explaining a conventional ranging operation.
[Explanation of symbols]
1 Microcomputer 2 Switch (MAIN)
3 Switch (SW1)
4 switch (SW2)
5 Zoom switch (TELE)
6 Zoom switch (WIDE)
7 Photometric sensor 8 Distance measuring element control unit 9 Light receiving element 9a Line sensor 1
9b Line sensor 2
DESCRIPTION OF SYMBOLS 10 Light emitting element 11 Shutter control part 12 Feed drive part 13 Lens barrel drive part 14 Focus drive part 15 Subject 16 Image signal (schematic diagram)
17 Image signal 2 schematic diagram)
24 Ranging unit

Claims (11)

Charge is accumulated by photoelectrically converting incident light from the subject with a pair of light receiving sensors and output as an image signal. When the signal level of the output image signal exceeds a predetermined value, accumulation of the charge is terminated. A distance measuring device for obtaining a distance to a subject based on an output image signal,
An arithmetic means for performing an operation for determining the contrast of the image signal based on the image signal output from the pair of light receiving sensors;
And a control unit that omits the calculation by the calculation unit when the time required for charge accumulation is within a predetermined time. 2. The distance measuring apparatus according to claim 1 , wherein the calculation for determining the contrast of the image signal is a calculation for obtaining a difference between a maximum signal level and a minimum signal level of the image signal. The pair of the light receiving sensor, the distance measuring apparatus according to claim 1 or 2, which is a line sensor. The distance measuring device according to claim 3 , wherein the line sensors are arranged on the same straight line. The pair of the light receiving sensor, the distance measuring apparatus according to claim 1 or 2, characterized in that an area sensor. 6. The distance measuring device according to claim 5 , wherein the area sensors are arranged on the same plane. Distance measuring apparatus according to claim 1 or 2, characterized in that said pair of light receiving sensors is constituted by CCD. Distance measuring apparatus according to claim 1 or 2, characterized in that it is constituted by the pair of the light receiving sensor silicon photodiode. Distance measuring apparatus according to claim 1 or 2, characterized in that said pair of light receiving sensors is constituted by skim CCD. Charge is accumulated by photoelectrically converting incident light from the subject with a pair of light receiving sensors and output as an image signal. When the signal level of the output image signal exceeds a predetermined value, accumulation of the charge is terminated. A distance measuring method for obtaining a distance to a subject based on an output image signal,
When the time required for charge accumulation is equal to or longer than a predetermined time, an operation for determining the contrast of the image signal based on the output image signal is performed, and when the time required for charge accumulation is within the predetermined time, ranging method characterized by determining the distance to the object based on the image signal output without pre Ki演 calculation. 11. The distance measuring method according to claim 10 , wherein the calculation for determining the contrast of the image signal is a calculation for obtaining a difference between the maximum signal level and the minimum signal level of the image signal.

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