JP2003215441A - Camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a camera capable of bringing a main subject into focus by accurately catching the main subject even in the case of photographing a subject on the background of which a light source exists. <P>SOLUTION: The camera has a range-finding means 11 detecting a subject distance based on subject light received from the subject, an auxiliary illuminating means 12 illuminating the subject in an auxiliary condition at the time of detecting the subject distance by the range-finding means, and an illuminating light emission permitting means 13 controlling the permission of the light emission of the illuminating means 12. The permitting means 13 controls to permit the light emission of the illuminating means 12 when the subject distance arithmetically calculated by the range-finding means 11 is equal to or above a specified distance, and the range-finding means 11 detects the subject distance again while the illuminating means 12 emits the light. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera such as a digital still camera, a silver-salt camera, a movie camera, a surveillance camera, etc., having a distance measuring mechanism for detecting a subject distance by receiving reflected light from the subject.

[0002]

2. Description of the Related Art Conventionally, a camera provided with an external light passive automatic focus adjustment function, which is provided with an auxiliary light source, permits the auxiliary light to be emitted in the following cases. That is, (1) when the subject brightness obtained by the photometric device, the distance measuring image pickup device, or the subject image pickup device is less than or equal to a predetermined value, that is, when the shooting range is entirely dark,
(2) When the distance measurement calculation result indicates that distance measurement is impossible, that is, when the subject brightness is low as a whole and distance measurement cannot be performed, light emission is permitted.

However, even when there is a bright light source in the background of a person even in the dark, for example, in the commemorative photo in front of a neon sign or a illuminated building at night,
People may be dark and the background may be light. Specifically, as shown in FIG. 7, the person 5 who is the main subject in the background where the tree 53 illuminated in the dark exists.
Consider the case where 2 exists.

In the case of photographing an object in which the light source such as the tree 53 exists in the background in the dark, when the light source overlaps with the range-finding sensitivity range 51 of the camera,
Since the light source 53 is sufficiently bright, it is possible to detect the distance. However, the person who is the main subject is too dark to be captured by the passive autofocus sensor. That is, as shown in FIG. 8, the luminance 52b of the tree portion is high and the luminance 52a of the person portion that is the main subject is low, and the person 52 that is the main subject is unable to measure the subject distance on the sensor. Sufficient contrast cannot be obtained.

Under such a large luminance difference condition, generally, the sensor can obtain accurate image information only in the background, and can detect only the distance of the light source in the background. Even in this case, since the brightness of the tree portion is large and distance measurement is not impossible, the auxiliary light is not emitted. Then, as a result of performing focus adjustment based on the detected subject distance of the tree 53, the resulting photograph has a background with focus.

[0006] In general, a focus detection sensor is susceptible to noise when photographing a dark portion, and therefore is often controlled to appropriately capture a bright subject, and a person is black in a night view. It often crashes. Therefore, it may not be possible to properly detect the subject distance and focus.

In recent years, it has been required to capture an accurate subject by widening the range-finding sensitivity range. However, under the above photographing conditions, conversely, a person is detected by a background neon sign or the like in the dark. There is a concern that you cannot do it.

[0008]

Therefore, the technical problem to be solved by the present invention is to accurately capture the main subject and focus on the main subject even when the subject having a light source in the background is photographed. It is to provide a camera that can be adapted to.

[0009]

In order to solve the above technical problems, the present invention provides a camera having the following structure.

The camera has a distance measuring means for detecting a subject distance based on the subject light received from the subject, an auxiliary illuminating means for illuminating the subject auxiliary when the subject distance is detected by the distance measuring means, and the auxiliary illumination. Illumination light emission permission means for controlling light emission permission of the means. The illumination light emission permission means controls to permit the auxiliary illumination means to emit light when the subject distance calculated by the distance measurement means is equal to or greater than a predetermined distance, and the distance measurement means is the auxiliary illumination means. The object distance is detected again while is emitting light.

In the above structure, the camera has a distance measuring means capable of directly or indirectly detecting the distance to the subject by receiving the reflected light from the subject. As a specific configuration of the distance measuring detection means, either one that directly detects the subject distance based on the principle of triangulation or one that detects the focus of the photographing optical system and derives the subject distance from the lens position is used. May be.

The auxiliary illumination means illuminates the subject when the subject distance is detected by the distance measuring means which has been widely used in the past. When the auxiliary lighting unit receives a certain condition, it is determined whether or not the auxiliary lighting unit receives a signal from the lighting light emission permission unit and emits light.

The condition as to whether or not the auxiliary lighting means emits light is that the subject distance calculated by the distance measuring means is equal to or greater than a predetermined distance, and other conditions may be added. Other conditions include the case where the subject brightness, which is conventionally used as a condition for light emission, is equal to or lower than a predetermined value, or the subject distance cannot be detected.

When the auxiliary lighting means emits light, the distance measuring means detects the subject distance again while the auxiliary lighting means emits light. The light emission amount of the auxiliary illumination means at this time may be appropriately adjusted according to subject brightness, previously detected subject distance, and shooting conditions such as camera settings.

When the auxiliary lighting means is controlled in this way, the distance measuring means of the camera functions as follows. That is, in a shooting condition in which there is a main subject such as a person in the background that includes a light source such as a neon sign in the dark, the subject distance is detected based on the light source because only the light source has high brightness. When the subject distance, which is the distance from the light source, is greater than or equal to a predetermined value, auxiliary light is emitted. As a result, the person as the main subject is actually closer than the light source, and thus the brightness is increased by the auxiliary light. However, since the light source is farther than the main object, the brightness does not change much. Therefore, by detecting the subject distance again while the auxiliary light is being emitted by the distance measuring means, it is possible to obtain a luminance distribution in which the main subject and the light source have high luminance. Then, it is possible to compare the high-intensity parts of both and control the photographing optical system so that the main subject is in focus.

Therefore, according to the above arrangement, even when a subject having a light source in the background is photographed, the main subject can be accurately captured and the focus can be adjusted to the main subject.

Specifically, the camera of the present invention can be configured in various modes as follows.

Preferably, the distance measuring means is based on the principle of triangulation based on the distance measuring optical system including a pair of image pickup devices and the image information obtained from each image pickup device of the distance measuring optical system. Distance measuring calculation means for calculating the subject distance based on the distance.

In the above arrangement, the distance measuring means is a so-called external light passive type which has a distance measuring optical system different from the photographing optical system of the camera and calculates the object distance based on the principle of triangulation. . That is, the subject distance is detected based on the defocus amount calculated by comparing the images of the subject obtained by each of the pair of image pickup devices.

In the distance measuring means having the above structure, a part of the image is extracted from the entire image of the object obtained by the pair of image pickup devices, and the object distance is calculated based on the shift amount until the two images are successively matched. Therefore, in general, it is difficult to detect the subject distance of the main subject, which is a portion with low contrast that is not sufficient for calculating the defocus amount. Therefore, by emitting the auxiliary light, the contrast of the main subject is increased, and the subject distance of the main subject can be measured, which is preferably used for the camera according to the present invention.

Preferably, the distance measuring means comprises a pair of image pickup devices, and a distance measuring optical system for re-imaging subject light incident through the photographing optical system, and image information obtained from the respective image pickup devices. Based on the principle of triangulation, the focus shift calculation means calculates the focus shift amount of the photographing optical system, and the focusing lens of the photographing optical system based on the focus shift amount calculated by the focus shift calculation means. An in-focus position detecting means for determining the position.

The distance-measuring means is provided with a distance-measuring optical system configured to divide the subject light from the photographing optical system of the camera into two and make them incident on a pair of image pickup devices, so-called T.
It is of the TL phase detection type. The lens position of the photographing optical system is adjusted so that the phases of the subject images from both of the image pickup devices match, and the subject distance is detected from the lens position where the photographing optical system is in focus.

In the distance measuring means having the above construction, the lens position of the photographing optical system is moved so that the phases of the luminance distributions of the images obtained by the pair of image pickup elements are matched, so that the lens position is determined based on the object with low contrast. Cannot be adjusted, and as a result, it is difficult to detect the subject distance of the subject. Therefore, by emitting the auxiliary light, the contrast of the main subject is increased, and the subject distance of the main subject can be measured, which is preferably used for the camera according to the present invention.

Preferably, the distance measuring means is a photographing optical system having an image pickup device for receiving the subject light, and a distance calculating means for detecting the subject distance based on a focusing lens position calculated from image information of the image pickup device. And.

In the above structure, the distance measuring means divides the image information from the image pickup device of the photographing optical system that receives the subject light into fine pixels and judges the difference in light amount between adjacent pixels while moving the photographing lens. It is of the TTL contrast detection type. That is, the in-focus lens position with the sharpest contrast is obtained, and the subject distance is detected from this lens position.

In the distance measuring means having the above structure, the lens position is determined by determining the sharpness of the contrast of the divided images of the subject image obtained by the image pickup device, so that the image of the main subject, which is a dark portion, is determined. It becomes difficult to detect the subject distance using. Therefore, by emitting the auxiliary light, the contrast of the main subject is increased, and the subject distance of the main subject can be measured, which is preferably used for the camera according to the present invention.

In each of the above structures, preferably, the illumination light emission permitting unit changes the predetermined distance according to the focal length of the photographing optical system.

In the above structure, by changing the focal length of the photographing optical system, the photographing angle of view changes, and proper photographing can be performed according to the distance to the subject. That is, the perspective of the subject located in the shooting range usually differs depending on the focal length. Therefore, by changing the predetermined value, which is the condition regarding the light emission of the auxiliary lighting means, the illumination light emitting means,
It is possible to control the more appropriate permission of the auxiliary light emission under actual shooting conditions.

With the above arrangement, by changing the light emission permission distance of the auxiliary lighting means by changing the magnification of the photographing optical system,
It is possible to accurately determine the background according to the photographing magnification and prevent the background from being out of focus.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a camera according to each embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the arrangement of a camera according to the first embodiment of the present invention. The camera 1a according to the present embodiment includes a photographing lens barrel 15 that constitutes a photographing optical system and a motor 16 that drives a lens of the photographing optical system.
And an image pickup means 14 such as a silver salt film or an image pickup element for forming an image of the subject light received through the taking lens barrel 15.
A distance measuring optical system 11 including a pair of image pickup devices that receive light from the subject, and a subject brightness detecting device 10 that measures the brightness of the subject in order to control the integration time in the image pickup devices of the distance measuring optical system. An auxiliary lighting device 12 that emits auxiliary light toward a subject, and a microcomputer 13 that receives and receives information from the subject brightness detection device 10 and the ranging optical system 11 to determine and control whether or not the auxiliary lighting device 12 emits light. Equipped with.

The camera 1a according to the present embodiment is equipped with an external light passive type distance measuring device, and specifically, the subject distance is measured as follows.

The subject light reflected from the subject enters the distance measuring optical system. The pair of image pickup devices of the distance measuring optical system 11 has two
A line sensor that receives three-dimensional object light, photoelectrically converts the object light at an integration time determined by the representative brightness of the object obtained by the object brightness detection device 10, and outputs it as image data to a microcomputer.

The microcomputer receiving the image data from each image sensor divides the image data finely, and compares the divided part of the image data of one image sensor with the divided part of the image data of the other image sensor sequentially. Then, the shift amount when the two match best is calculated. Since this shift amount is the shift of the subject viewed from each image sensor, the subject distance can be calculated based on the principle of triangulation.

With the camera having the above-mentioned structure, the distance to the subject can be measured only in the portion where the contrast of the subject is sufficient. On the other hand, in the portion where the contrast is low, it is difficult to judge the coincidence of both images. It has the property of being difficult to measure.

FIG. 2 is a block diagram showing the arrangement of a camera according to the second embodiment of the present invention. The camera 1b according to the present embodiment includes a photographing lens barrel 15 that constitutes a photographing optical system and a motor 16 that drives a lens of the photographing optical system.
An image pickup means 14 such as a silver salt film or an image pickup element for forming an image of the subject light received through the taking lens barrel 15.
Distance-measuring optical system 11 including a pair of image pickup devices that divide the subject light received through the taking lens barrel 15 into two and receive the split light.
In order to control the integration time in the image sensor of the distance measuring optical system, a subject brightness detecting device 10 that measures the brightness of the subject, an auxiliary lighting device 12 that emits auxiliary light toward the subject, and a subject brightness detection. Device 10 and ranging optical system 11
And a microcomputer 13 for receiving information from the auxiliary lighting device 12 and determining and controlling whether or not the auxiliary lighting device 12 emits light. A part of the light from the photographic optical system is normally configured to enter the side of the distance measuring optical system 11 by the sub-mirror 17b through the semi-transmissive portion of the quick return mirror 17a. As shown, the subject light reaches the image pickup means 14.

The camera 1b according to this embodiment has a TTL
The focus detection device of the phase detection type is provided, and the subject distance is measured as follows.

The subject light reflected from the subject passes through the photographing optical system 15, is reflected by the quick return mirror 17, and enters the distance measuring optical system 11. In the distance measuring optical system 11, the emitted light is divided into two with an incident light axis interposed therebetween, and the incident light is incident on each of the pair of image pickup elements and photoelectrically converted. Distance measuring optical system 11
The image sensor is a line sensor that receives two-dimensional subject light, and the integration time is determined by the representative luminance of the subject obtained by the subject luminance detection device 10. The image data obtained by the image sensor is output to the microcomputer 13.

The microcomputer 13 drives the motor 16 while comparing the image data from the respective image pickup devices, and drives the lens of the photographing optical system as shown by an arrow 40. When the lens is in the in-focus position, the subject light beams match at the same point, but in the out-of-focus position, the order of the subject light beams is changed and a shift occurs. In this way, when the lens positions are determined such that the subject light is the same at the same point, the subject distance is calculated based on that position.

In the camera having the above-described structure, it is determined whether or not the two images match each other based on the brightness distributions of the object images obtained by the respective image pickup devices. Can be measured. On the other hand, in a portion where the contrast is low, it is difficult to determine the coincidence between the two images, and thus it is difficult to measure the subject distance.

FIG. 3 is a block diagram showing the structure of a camera according to the third embodiment of the present invention. The camera 1c according to the present embodiment includes a photographing lens barrel 15 that constitutes a photographing optical system and a motor 16 that drives a lens of the photographing optical system.
An image pickup device 14a for forming an image of subject light received through the taking lens barrel 15, and a subject brightness detection device 10 for measuring the brightness of the subject in order to control integration time in the image pickup device of the distance measurement optical system. An auxiliary lighting device 12 that emits auxiliary light toward a subject, and a subject brightness detection device 10
And the auxiliary lighting device 1 by receiving information from the image pickup device 14a.
And a microcomputer 13 for determining and controlling whether or not to emit light.

The camera 1c according to this embodiment has a TTL
A focus detection device of contrast detection type is provided, and the subject distance is measured as follows.

The subject light reflected from the subject enters the image pickup device 14a through the photographing optical system 15. Image sensor 14
The integration time of a is determined by the representative brightness of the subject obtained by the subject brightness detection device 10, and outputs image data to the microcomputer 13. The microcomputer 13 divides the image data into fine pixels. When the lens is at the in-focus position, the subject image is the sharpest and has the highest contrast. Therefore, the microcomputer 13 drives the motor 16 to move the lens position of the photographing optical system 15 as indicated by an arrow 42. However, the light amount difference between adjacent pixels is compared to determine the focus lens position. When the lens position is determined in this way, the subject distance is calculated based on the position.

In the camera having the above structure, the focusing lens position is determined with reference to the sharpness of the image by comparing the contrasts of the subject images obtained by the image pickup device 14a. Only the lens position can be determined and the distance to the subject can be measured. On the other hand, in a portion where the contrast is low, it is difficult to determine the coincidence between the two images, and thus it is difficult to measure the subject distance.

Using the cameras of the first to third embodiments,
A light source 53 such as a tree in the dark as shown in FIG.
Consider a case in which a subject having a background having a main subject and a main subject 52 is photographed. The camera 1a obtains a brightness distribution as shown in FIG. 8 when the subject light is incident on the distance measuring optical system. That is, when the subject is photographed, distance measurement is performed based on the luminance distribution in the distance measurement sensitivity range 51 based on the high luminance tree portion 52b, and the low luminance main subject 52a portion is measured. Is not the target part of.

5 and 6 show the flow of processing relating to the distance measurement calculation processing of the camera according to this embodiment. Figure 1 is the first
6 is a process in the camera 1a according to the embodiment.
Is a process in the second and third cameras 1b and 1c. The difference between FIG. 5 and FIG. 6 is that the distance calculation processing is different depending on the structure of the distance measuring device of the camera according to each of the above-described embodiments, and the processing of other parts is different. It is almost the same.

First, FIG. 5 will be described. The camera is
Under the control of the microcomputer, the subject distance and the subject brightness are measured by the above-described operation (# 11). The subject distance is determined based on the high-luminance portion of the subject overlapping the distance measurement sensitivity range 51. Next, the microcomputer 13 determines whether or not a distance measurement value relating to the subject distance has been obtained (# 12).

When the distance measurement value is obtained, the microcomputer 13
Determines the illumination permission distance D1 based on the focal length of the photographing optical system 15 (# 13). The illumination permission distance may be determined by a data table or the like determined according to the focal length of the photographing optical system 15, or may be calculated by calculation using the focal length as a variable.

Next, the microcomputer 13 compares the illumination permission distance determined in step 13 with the subject distance measured in step 11 (# 14). Then, when the subject distance is larger than the illumination permission distance D1, it is determined whether or not the subject brightness measured in step 11 is less than or equal to a predetermined value (# 15).

When the subject brightness is below a predetermined level, the microcomputer causes the auxiliary lighting device 12 to emit light. Then, the distance of the subject illuminated by the auxiliary light from the distance measuring optical system 11 is measured again (# 16).

As a result of distance measurement while emitting auxiliary light, the object has low brightness and insufficient contrast, and has a brightness that allows distance measurement. That is, since the main subject is located at a short distance from the camera, the brightness of the main subject is improved more than that of the background when illuminated by the auxiliary light source. as a result,
As shown in FIG. 4, the luminance distribution obtained by the distance measuring optical system shows the person 52a as the main subject and the tree 5 as the background light source.
Both 2b and 2b have high brightness. In such a case, the distance measuring device can detect the precise focus position by comparing the distance between the person and the Christmas tree, and it is possible to take a photograph in which the person is in focus.

In step 14, if the subject distance is greater than or equal to the predetermined distance D1, or in step 15,
When the subject brightness is equal to or higher than the predetermined value, it is determined that the proper subject distance is measured for the main subject, and the emission of the subject light is not permitted.

On the other hand, in step 12, if the distance cannot be measured, such as when the contrast of the entire subject is low, the microcomputer permits the emission of the auxiliary light and detects the subject distance again.

Next, FIG. 6 will be described. Under the control of the microcomputer, the camera detects the position of the focusing lens and measures the subject brightness by the above-described operation (# 21). Next, the microcomputer 13 determines whether or not the focusing lens position has been obtained (# 22).

When the focus lens position is obtained, the microcomputer 13 determines the illumination permission distance D1 based on the focal length of the photographing optical system 15 and calculates the subject distance from the focus lens position (# 23). ).

Next, the microcomputer 13 compares the illumination permission distance D1 determined in step 23 with the calculated subject distance (# 24). Then, when the subject distance is larger than the illumination permission distance D1, it is determined whether or not the subject brightness measured in step 21 is less than or equal to a predetermined value (# 25).

When the subject brightness is below a predetermined level, the microcomputer causes the auxiliary lighting device 12 to emit light. Then, the focusing lens position of the subject illuminated by the auxiliary light from the distance measuring optical system 11 is detected, and the subject distance is measured again (# 2).
6).

In step 15, if the subject distance is greater than or equal to the predetermined distance D1, or in step 16,
When the subject brightness is equal to or higher than a predetermined value, it is determined that the focusing lens position is obtained for the main subject, and the emission of the subject light is not permitted.

On the other hand, in step 22, when the focusing lens position cannot be obtained, for example, when the contrast of the entire subject is low, the microcomputer emits auxiliary light to detect the focusing lens position, and then the subject is detected again. Calculate the distance.

As a result of distance measurement while emitting the auxiliary light, the object has low brightness and insufficient contrast, and the brightness is such that the focusing distance can be detected. That is, in the luminance distribution obtained by the distance measuring optical system, as shown in FIG. 4, the person 52a as the main subject and the tree 52b as the light source of the background have high luminance, and the focus is based on the person as the main subject. The lens position can be determined.

As described above, according to the camera of the present embodiment, when the subject distance is longer than the predetermined illumination permission distance, the auxiliary light is emitted to measure the subject distance again, so that the light source is dark. Even when shooting a subject where a main subject such as a person is present in the background having a background, it is possible to detect the person and shoot a photograph in which the person is in focus without focusing on the light source. .

Further, by using the light emission permission only when the subject brightness is less than a predetermined value, the auxiliary illumination device is not allowed to emit light during landscape photography during the day, and the usability of the camera is not impaired.

The present invention is not limited to the above embodiment, but can be implemented in various other modes.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a camera according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a camera according to a second embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a camera according to a third embodiment of the present invention.

FIG. 4 is a diagram showing a luminance distribution of a subject when auxiliary light is emitted.

FIG. 5 shows a flow of processing relating to distance measurement calculation processing of the camera of the first embodiment.

FIG. 6 shows a processing flow relating to distance measurement calculation processing of the cameras according to the second and third embodiments.

FIG. 7 is a diagram showing a specific example of a subject having a light source in the background.

8 is a diagram showing a luminance distribution of the subject of FIG. 7 when no auxiliary light is emitted.

[Explanation of symbols]

1a, 1b, 1c cameras 10 Subject brightness detection device 11 Distance optical system 12 Auxiliary lighting device 13 Microcomputer 14 Imaging means 14a image sensor 15 Shooting optical system 16 motor 17 Quick Return Mirror 50 subjects 51 Range-finding sensitivity range 52 Main subject 53 background light source

Continued front page    F-term (reference) 2H011 AA01 BA05 BA33 BB01 BB04                       BB05 CA01 DA01 DA08                 2H051 AA01 BA02 BA20 BB07 BB10                       CB20 CB22 CE24 DA07 DA19                       DB01 DB10 EB13 EB19

Claims (5)

[Claims] 1. A distance measuring means for detecting a subject distance based on subject light received from a subject, an auxiliary illuminating means for illuminating the subject auxiliary when the subject distance is detected by the distance measuring means, and the auxiliary illuminating means. And an illumination light emission permission means for controlling light emission permission of the illumination light emission permission means, wherein the illumination light emission permission means causes the auxiliary illumination means to emit light when the subject distance calculated by the distance measuring means is equal to or more than a predetermined distance. The camera is controlled so as to permit, and the distance measuring unit detects the subject distance again while the auxiliary lighting unit emits light. 2. The distance measuring means is based on a principle of triangulation based on a distance measuring optical system including a pair of image pickup elements, and image information obtained from each image pickup element of the distance measuring optical system. 2. The camera according to claim 1, further comprising a distance measuring calculation unit that calculates a subject distance. 3. The distance measuring means comprises a pair of image pickup devices, and a distance measuring optical system for re-imaging subject light incident through a photographing optical system, and image information obtained from the respective image pickup devices. Based on the principle of triangulation, the focus shift calculation means calculates the focus shift amount of the photographing optical system, and the focus lens position of the photographing optical system based on the focus shift amount calculated by the focus shift calculation means. The camera according to claim 1, further comprising: a focus position detection unit that determines whether or not 4. The distance measuring means includes a photographing optical system having an image sensor for receiving a subject light, and a distance calculating means for detecting a subject distance based on a focusing lens position calculated from image information of the image sensor. The camera according to claim 1, further comprising: 5. The camera according to claim 1, wherein the illumination light emission permission unit changes the predetermined distance according to a focal length of a photographing optical system.