JPS63267926A - Image pickup device - Google Patents

Abstract

PURPOSE:To execute the precise control of exposure at low cost with a simple constitution by providing a distance measuring means for measuring the distance to an object, a comparison means for comparing the distance with a previously specified distance (d) and an exposure control means for executing the control of exposure based on the compared result of the comparison means. CONSTITUTION:When it is decided that the distance D to the object (h) which is obtained by measuring by the distance measuring means (a) is shorter than the limit distance (d) specified according to the precision of measuring distance of distance measuring means (a), the control C of exposure that an iris and the speed of a shutter are changed based on the distance D to the object is executed. Meanwhile, when it is decided that the distance D to the object is longer than the limit distance (d), on the contrary, the control (f) of exposure by dimming based on the light quantity of a reflected light from the object is executed. Namely, in a short distance photographing in which the precision of measuring distance is very high, the precise control of the exposure quantity based on the measured distance to the object (h) without receiving the effect of the reflectance of the object is executed and in a long distance photographing where the error of measuring distance becomes large, the control of the exposure quantity based on the received light quantity of the reflected light from the object (h) is executed. Thus excessive overexposure can be prevented in the long distance and the precision of exposure can be raised.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an imaging device for photographing and recording a subject, and particularly to an imaging device having a distance measuring means and an illumination means.

[Conventional technology]

This type of imaging device includes one that records a subject on a photographic film and one that records a subject on a magnetic disk, optical disk, or the like using an image sensor.

In the currently used imaging devices of this type, the sensitivity of the image sensor (or photographic film) is not necessarily sufficient for shooting in dark places, so in such cases, lighting devices such as strobes and flashes are used. Therefore, photography is performed using the illumination light of this illumination device as auxiliary light.

However, the size and light intensity of the light source of the illumination device used in this case are not necessarily large enough to illuminate the subject, and the subject is often illuminated from near the imaging device as a point light source. Therefore, the amount of light attenuates in inverse proportion to the square of the distance, and under this condition it is difficult to control the amount of exposure to the image sensor to an appropriate value with high precision.

Currently, methods for controlling the amount of exposure to an image sensor (or photographic film) can be broadly classified into the following two methods.

(2) Detecting the amount of reflected light from the subject and controlling the output of the illumination means so that the detected amount of light becomes constant (hereinafter referred to as the first control method).

■Using the fact that the amount of illumination light attenuates in inverse proportion to the square of the distance to the subject, the amount of illumination light irradiated to the subject can be calculated by measuring the distance to the subject with a distance measuring device. , and control the exposure amount according to the calculation result (hereinafter,
(referred to as the second control method).

[Problem that the invention seeks to solve]

However, there are advantages and disadvantages to all of the above-mentioned methods of controlling the amount of light in conventional imaging devices.

In other words, if the subject is a person, it is sufficient that the exposure matches the face (skin); however, in the case of the first control method described in item (■) above, the proportion of the face to the entire screen is very small; Also, compared to the reflectance of the face (approximately 20 units), it is rare for objects such as the periphery of the face and the back shadow to occupy a large area of the screen, with a reflectance of more than 4 times or less than 1/4. For example, when photographing a person wearing white or black clothes, the exposure of the person's face will not be appropriate, and the reproduced image will look very strange.

However, even with the first control method described in item (2), exposure control with a sufficiently high precision is possible unless special conditions are taken when photographing a subject with uniform reflectance.

On the other hand, in the case of the second control method described in item (2), the distance measurement error to the subject directly appears as an exposure error. In terms of focusing, the longer the distance, the deeper the depth of field becomes.
Although there is no practical problem even if the distance measurement accuracy is compromised, a situation arises in which this is unacceptable from the perspective of exposure control for the above-mentioned reasons.

Conventionally, when an imaging device is provided with a distance measurement function, due to technical limitations, manufacturing costs, etc., the distance measurement accuracy has been set to an accuracy that does not pose a problem in terms of depth of field. However, this distance measurement accuracy has the disadvantage that it cannot be said to be sufficient for the accuracy required for exposure control above a certain distance of the subject, and if the distance measurement accuracy is made too high, it will become extremely However, they also had the problem of becoming expensive, complicated, and large, making them impractical.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide an imaging device that has a simple configuration, is inexpensive, and can easily perform highly accurate exposure control regardless of the subject distance.

[Means for solving the problem] In order to achieve this purpose, a distance measuring means for measuring the distance to the subject, a distance ff1ffD to the subject measured by the distance measuring means, and a distance measuring means for measuring the distance to the subject are provided. A comparison means compares a predetermined distance d predetermined based on distance measurement accuracy, and based on the comparison result of the comparison means, when D<d, exposure control is performed according to the distance to the subject, and when D≧d. Sometimes, it is characterized by comprising an exposure control means for performing exposure control by dimming according to the amount of reflected light from the subject.

Further, when the distance 11i1iD and d are D<d, the exposure control means of the present invention is based on the following formula %, where k is a proportionality constant and G is the light amount or guide number of the illumination means. Exposure control is performed by adjusting and driving an exposure adjusting means having at least one of an aperture and a shutter mechanism, and when D≦d, illumination is controlled based on the amount of reflected light from the subject detected by the measuring means. It is characterized in that exposure control is performed by adjusting the output of the means.

[Function] When the present invention determines that the distance to the subject measured by the distance measuring means is shorter than the limit distance d determined based on the distance measurement accuracy of the distance measuring means, the distance to the subject is determined based on the distance 11i1D. When the camera determines that the distance to the subject is longer than the limit distance d, it performs exposure control by adjusting the light intensity based on the amount of light reflected from the subject. As a result, in short-distance shooting, exposure control errors are minimized and high-precision image recording that is unaffected by subject reflectance can be performed, and long-distance shooting is possible! In IT photography, images can be captured and recorded with an appropriate average value of overall exposure.

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the basic configuration of an embodiment of the present invention. In this figure, a denotes distance measuring means for measuring the distance to the subject.

b is the distance l to the subject measured by distance measuring means a! ! tD
and a predetermined distance d predetermined based on the distance measurement accuracy of the distance measurement means a. C is an exposure control means, and according to the comparison result of the comparison means, D<d
When D≧d, exposure control is performed according to the distance to the subject, and when D≧d, exposure control is performed by adjusting light according to the amount of light reflected from the subject.

For example, when the distance lID and d are D<d, the exposure control means C is based on the following formula %<Dv dimming, where k is a proportionality constant and G is the light amount or guide number of the illumination means e. Exposure adjustment means f having at least one of an aperture and a shutter mechanism for controlling exposure;
This is done by adjusting and driving, and when D≦d,
Exposure control is performed by adjusting the output of the illumination means e based on the amount of reflected light from the object detected by the measurement means g.

FIG. 2 shows the overall circuit configuration of an embodiment of the present invention. In this figure, 1 is an optical system that forms a subject image, 2A is a movable member (exposure control means) such as a shutter or an aperture for controlling the exposure amount of an image sensor, which will be described later, and 2B is the member 2. This is a driver (drive circuit) that drives the 8.

3 is an image sensor using a CCO (charge-coupled device) array or the like that converts the optical image of the object formed by the optical system 1 into an electrical signal; 4 is an image sensor that reads out object image information from the image sensor 3 in the form of an electrical signal; A signal processing circuit 5 converts the video signal into a specified video signal (picture signal), and 5 is a recording unit that records the video signal obtained by the signal processing circuit 4 on a recording medium such as a semiconductor memory, a magnetic disk, or a magnetic tape. .

6 is a distance measuring device that measures the distance to the subject. As the distance measuring device 6, various methods can be used, such as an ultrasonic method, an infrared method, and a triangulation method using a CCD. 7
The data and detection information from each part of the imaging device are manually stored in the internal memory ROM, and according to the control procedure shown in Figure 4, various calculations and judgment processes are performed to control the overall performance of each part of the imaging device. This is an arithmetic control circuit that performs control.

Reference numeral 8 denotes a release button for instructing the start of photographing, and manually inputs a release signal to the arithmetic control circuit 7.

The above-mentioned components 1 to 8 surrounded by broken lines constitute the imaging device A according to the present invention. Further, if the parts indicated by the symbols 3 to 5 are replaced with photographic film, a conventional general still camera or movie camera can be obtained, and the present invention can also be applied to these imaging devices.

Further, reference numeral 10 denotes a lighting device for illuminating the subject, which is connected to the imaging device A by a control line X. The lighting device A may be one that emits light continuously over time, such as an incandescent light bulb, or one that emits light in a pulsed manner, such as a flash light emitting device called a strobe or flash. But it can also be used for video shooting.

FIG. 3 shows a detailed circuit configuration example of the illumination device IO of FIG. 2.

In FIG. 3, 101 is a light emitting unit that includes a lamp or flash discharge tube and an accompanying optical system (condensing optical system) such as a reflecting mirror and a lens.

102 is a power source that supplies light emission energy to the light emitting section 101; 103 is a power supply amount control circuit that controls the amount of power supplied from the power source 102 to the light emitting section 101.

104 is a photometering circuit that measures the amount of light directly bundled from the light emitting unit lot; 105 is a photometering circuit that measures the amount of light reflected from the subject; output terminals from the photometering circuits 104 and 105 respectively Connect to input terminals a and b. As this switch changeover circuit 106, a commercially available analog multi-breather or the like can be used. The switch switching circuit 106 conducts the input terminal A and the output terminal C when the control terminal d connected to the control line X is at a high level, and conducts the input terminal through the input terminal when the control terminal d is at a low level. Switching control is performed so that output terminal C conducts. An output terminal C of this switch changeover circuit 106 is connected to a control terminal e of the power supply amount control circuit 103.

Next, the operation of the embodiment of the present invention with the above configuration will be explained with reference to the flowchart of FIG.

When a power switch (not shown) is turned on by an operator, power is supplied to each part of the apparatus shown in FIG. Thereafter, a command signal from the arithmetic control circuit 7 causes the distance measuring device 6 to detect the distance 1 to the subject! fD is measured, and the measured value is sent to the arithmetic control circuit 7 and stored in an internal register (not shown) (step 201).

Next, the arithmetic and control unit 7 determines whether the measured distance to the subject is greater than a limit value DI set in advance based on the distance measurement accuracy of the distance measuring device 6, that is, whether the measured value of the distance to the object is greater than the limit value DI set in advance based on the distance measurement accuracy of the distance measuring device 6, that is, whether the measured value of the distance to the subject is larger than the limit value DI set in advance based on the distance measurement accuracy of the distance measuring device 6. The distance to which the amount of photographing can be controlled not by the reflected light from the subject but by the measured distance to the subject (
(limit value) Determine whether it is farther than Dl (step 2
02).

If the measured distance or the limit value distance I! If it is farther than IDl, that is, if D>Di is affirmed, the arithmetic control circuit 7 sets the control line X to a low level. When the control line X becomes low level, the switch circuit 10 of the lighting device 10
8 and terminal C are electrically connected, thereby connecting the photometry circuit 105 that measures the amount of light reflected from the subject and the power supply amount control device 103 via the switch changeover circuit 106, and the light emitting unit 101 The amount of light emitted by the light emitting unit 101 is controlled by the power supply amount control circuit 103 so that the amount (intensity) of the illumination light reflected from the subject is constant (step 2).
03). Next, the arithmetic control circuit 7 selects a predetermined aperture value and shutter speed so that the amount of exposure to the image sensor 3 is appropriate for the amount of light reflected from the subject, and performs exposure via the driver 2B. The amount control member 28 is driven and controlled (step 204). Next, the arithmetic control circuit 7 determines whether the release 8 has been operated by the operator or not (step 207). If the release 8 is not operated and the release is If so, the process returns to step 201 and repeats the operations from step 202 onwards.

If it is determined in step 207 that the release 8 has been operated, the arithmetic control circuit 7
(step 208), the signal processing circuit 4 reads the subject image information from the image sensor 3 and converts it into a prescribed video signal (step 209), and at the same time, the recording section 5 records the video signal on a recording medium. Record it (step 21O).

On the other hand, in the above step 202, if a negative determination is made that the measured distance to the subject is closer than the above limit value Dl, the arithmetic control circuit 7 sets the control line X to a high level and switches the lighting device 10. Terminal a and terminal C of circuit 106
A photometry circuit 104 and a power supply amount control circuit 103 that directly measure the light intensity of the light emitting unit 101 itself by establishing conduction between them.
The light emitting unit 10 is connected by the power supply amount control circuit 103.
The amount of power supplied to the light emitting unit 101 is controlled so that the amount of light emitted from the light emitting unit 101 (intensity) becomes a predetermined value (step 205). Further, the arithmetic control circuit 7 adjusts the illumination device l to the subject based on the distance raD to the subject for this predetermined light amount.
The amount of illumination light arriving from O and the conditions for properly exposing the image sensor 3 (generally referred to as Dv dimming conditions) are calculated using the following formula, or the calculation results are stored in advance. Determine by referencing the table.

Specifically, when the exposure time is constant, (aperture FNo.
) − The sum k is a constant of proportionality. Next, the FN of the aperture obtained under the above conditions.

(F number), the exposure control member (aperture) 28 is driven via the driver 2B (step 206).

Next, the process proceeds to the judgment process of step 207 described above, and if step 207 is an affirmative judgment, step 207 is performed in the same manner as described above.
8. Execute the process of 209.210.

In the above configuration, if the exposure amount control member list consists of an aperture and a shutter, step 204 described above is performed.
By driving the aperture in step 206 and controlling exposure by driving the shutter in step 208, both still images and moving images can have 19 shadows.

Furthermore, in a film camera in which the imaging device uses photographic film, the processes of steps 209 and 210 in FIG. 3 are of course omitted. Further, when the illumination device 1O emits light continuously, it may emit light from beginning to end, but when it emits light in a pulsed manner like a flash light emitting device, it may emit light at the timing of step 208 in FIG. 3.

FIG. 5 shows yet another embodiment of the present invention. This figure has almost the same configuration as FIG. 2, with only a few differences. The same components as in FIG. 2 are given the same reference numerals, and only the parts that are different from FIG. 2 will be described below. The functional difference is that in the first embodiment shown in Fig. 2, the focal length of the optical system is constant, whereas in this embodiment, the focal length changes like an interchangeable lens or a zoom lens. That's the point you get.

In FIG. 5, 301 is an optical system, including an interchangeable lens,
Alternatively, it may be an attached zoom lens or the like. 302
is the lens system of the optical system 301, and 303A is the lens system 3.
Focus adjustment member (including motor) that adjusts the focus of 02
, 303B is a driver that drives and controls the focus adjustment member, 304 is the focal length of the lens and the distance to the subject VS
It is a sensor such as an encoder for detecting the position of the distance ring of the lens.

Here, for the fixed focus of the interchangeable lens, the fixed focus data may be stored in advance in a ROM built into the interchangeable lens, and read out from the ROM during operation to transmit the focal length information to the arithmetic control circuit 7. . If this is not the case (zoom lens, etc.), the focal length and object distance are transmitted from the sensor 304 to the arithmetic control circuit 7.

Reference numeral 305 is a zoom operation member when the optical system 301 is a zoom lens, and it may be operated directly manually or via a control circuit. Further, the distance measuring device (sensor) 6 determines the amount of blur (degree of focus) of the subject by the optical beam sent via the beam splitter 306 placed in the middle of the optical path passing through the optical system 301 and going to the image sensor 3. Assume that the configuration is to measure . In this case, the distance measurement accuracy (focusing accuracy) of a telephoto lens will be high.

The above is the configuration of FIG. 5, and the operation of this embodiment will be described below with reference to the flowchart of FIG. 6. 6th
The figure is almost the same as FIG. 4, and only the differences will be explained.

After starting the operation, the arithmetic control circuit 7 first detects the sensor 30.
4, the focal length 11tf of the optical system 301 is manually adjusted.

Next, from the focal length f, a distance of 1 mDI (
f) is determined (step 401 in FIG. 6).

Next, the distance to the subject is measured in the same manner as in FIG. There are various distance measuring methods, but for example, as in this embodiment, the arithmetic control circuit 7 drives the focus adjustment member 303A via the driver 303B, and uses the signal from the distance measuring device 6 to minimize blur. Adjust the focus to , and then focus on sensor 3.
The distance to the subject can be measured by reading distance 11 (position of lens distance i ring) from 04 (step 4o2 in FIG. 6).

Since the following operation is exactly the same as that in FIG. 4, detailed explanation thereof will be omitted.

However, if the determination in step 207 in FIG. 6 is No, the process returns to step 401 described above, thereby making it possible to cope with changes in focal length due to zoom operation.

(Effects of the Invention) As explained above, according to the present invention, it is determined that the distance to the subject measured by the distance measuring means is shorter than the limit path 111d determined based on the distance measuring accuracy of the distance measuring means. When you do,
Exposure control is performed by changing the aperture and shutter speed based on the distance to the subject 11111D, and conversely, the distance to the subject @
When it is determined that D is farther than the limit distance d, exposure control is performed by adjusting light based on the amount of light reflected from the subject, so when taking close-up shots, the exposure control error is minimized and the subject's reflection is controlled. It is possible to perform highly accurate imaging and recording that is not affected by the exposure rate, and in long-distance photography, it is possible to achieve the effect that imaging and recording can be performed with an appropriate average value of overall exposure.

In other words, according to the present invention, in close-range II shooting where the distance measurement accuracy is sufficiently high, high-precision exposure control is performed based on the measured distance to the subject and is not affected by the subject reflectance, and the distance measurement error is large. In long-distance photography, the exposure is controlled based on the amount of reflected light received from the subject, so extreme overexposure can occur, especially when the subject is far away and there is no background. Not only can it prevent this, but it can also achieve extremely high exposure accuracy for people wearing white or black clothes, and when photographing long-distance subjects, the average value of the exposure as a whole is more important than individual faces. However, such requirements can be satisfied by controlling the exposure amount based on the amount of received reflected light.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the basic configuration of an embodiment of the present invention, Figure 2 is a block diagram showing the overall circuit configuration of an embodiment of the invention, and Figure 3 is a detailed circuit diagram of the lighting device in Figure 2. FIG. 4 is a block diagram of the embodiment of the present invention shown in FIGS. 2 and 3. FIG. 5 is a block diagram showing a circuit configuration of another embodiment of the present invention. FIG. 6 is a flowchart showing an operation example of the embodiment of FIG. DESCRIPTION OF SYMBOLS 1... Optical system, 2A... Exposure amount control member, 2B... Driver, 3... Image pick-up element, 4... Signal processing circuit, 5... Recording part, 6... Distance measurement Apparatus, 7... Arithmetic control circuit, 8... Release, lO... Lighting device, 101... Light emitting section, 102... Power supply, 103... Power supply amount control circuit, 104.105... - Photometry circuit, 106... Switch switching circuit, 301... Optical system, 303A... Focus adjustment member, 304... Sensor.

Claims (1)

[Claims] 1) a) distance measuring means for measuring the distance to a subject; b)
a comparison means for comparing the distance D to the subject measured by the distance measurement means with a predetermined distance d predetermined based on the distance measurement accuracy of the distance measurement means; c) based on the comparison result of the comparison means; , when D<d, exposure control is performed according to the distance D to the subject, and D≧
d. An imaging apparatus characterized by comprising: exposure control means for performing exposure control by dimming according to the amount of light reflected from the subject at the time of d. 2) In the apparatus according to claim 1, when the distances D and d are D<d, the exposure control means, where k is a proportionality constant and G is the amount of light of the illumination means or a guide number, performs the following: Exposure control by Dv dimming based on the formula F number = k x G/D is performed by adjusting and driving an exposure adjusting means having at least one of an aperture and a shutter mechanism, and when D≦d, the exposure is detected by the measuring means. An image pickup apparatus characterized in that exposure control is performed by adjusting the output of the illumination means based on the amount of reflected light from the subject. 3) The imaging device according to claim 1 or 2, wherein the value of the predetermined distance d is changed depending on the focal length of the lens.