JP4307648B2 - camera - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a camera, and more particularly to a camera capable of determining a night scene and performing a shooting operation suitable for the night scene.
[0002]
[Prior art]
Conventionally, many cameras have been developed that are devised when shooting night scenes.
[0003]
For example, Japanese Patent Application Laid-Open No. Hei 7-199039 discloses a camera that allows a photographer to set a night view mode and take a picture when shooting a night view scene. This camera performs AF by projecting auxiliary light onto a subject.
[0004]
Further, in the camera described in Japanese Patent Laid-Open No. 5-249369, when the pixel data of the AF sensor is distributed in a high luminance part and a low luminance part, it is determined that the person has a bright background and the integration of the AF sensor A technique is disclosed in which AF detection is performed with emphasis on the low-luminance part by extending the time and integrating again.
[0005]
[Problems to be solved by the invention]
However, the camera described in Japanese Patent Laid-Open No. 7-199039 has a problem that it is troublesome for the photographer to set the night view mode in accordance with the photographing scene.
[0006]
Further, in the camera described in Japanese Patent Laid-Open No. 5-249369, since the luminance is detected by one line sensor, there is a problem that the detection area is narrow and a high-contrast subject is erroneously recognized. ing. Furthermore, there is a problem that it cannot be distinguished from a night view unless a bright part enters the detection area.
[0007]
The present invention has been made in view of the above problems, and an object of the present invention is to provide a camera capable of automatically discriminating a night scene and performing a photographing operation suitable for the night scene without setting by the photographer.
[0008]
[Means for Solving the Problems]
That is, the present invention provides an imaging unit, a luminance distribution detection unit that detects a luminance distribution in a photographing screen based on an output result of the imaging unit, and a region where predetermined luminance is continuous based on an output result of the luminance distribution detection unit. A luminance region discriminating unit for discriminating and a region where the predetermined luminance is continuous based on the output result of the luminance region discriminating unit Face of An arithmetic means for calculating the product and an output of the arithmetic means As a result of the determination as to whether or not the area of the region where the distribution of pixels having higher luminance than the predetermined luminance is less than or equal to the predetermined value and the luminance in the photographing screen based on the output of the luminance distribution detecting means is predetermined Based on the result of determining whether the brightness is lower than the value And a photographing mode determining means for determining the photographing mode.
[0010]
In the camera of the present invention, the luminance distribution in the photographing screen is detected by the luminance distribution detecting means based on the output result of the imaging means. Then, based on the output result of the luminance distribution detection means, an area where predetermined luminance continues is determined by the luminance area determination means. Further, based on the output result of the luminance region discriminating means, the region where the predetermined luminance is continuous Face of The product is calculated by the calculation means. Output of this calculation means As a result of the determination as to whether or not the area of the region where the distribution of pixels having higher luminance than the predetermined luminance is less than or equal to the predetermined value and the luminance in the photographing screen based on the output of the luminance distribution detecting means is predetermined Based on the result of determining whether the brightness is lower than the value The shooting mode is determined by the shooting mode determination means.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0013]
FIG. 1 is a block diagram showing the configuration of a camera according to the first embodiment of the present invention.
[0014]
In FIG. 1, a microcomputer 11 is a system controller that controls the entire camera, and includes a CPU (central processing unit) 11a, ROM 11b, RAM 11c, and an analog-digital (A / D) converter (ADC). 11d and EEPROM 11e.
[0015]
The CPU 11a performs a series of operations according to a sequence program stored in the ROM 11b. The EEPROM 11e stores correction data relating to AF, photometry / exposure calculation, and the like for each camera.
[0016]
The microcomputer 11 is connected to an AF area sensor 12 that captures a subject image formed by a distance measuring optical system and converts it into sensor data that is an electrical signal. The area sensor 12 includes a light receiving element group that is two-dimensionally arranged in the horizontal direction and the vertical direction as the imaging region 12a, and a processing circuit 12b for these light receiving element groups.
[0017]
The microcomputer 11 includes a focus lens driving unit 14 for driving the focus lens 13, a focus lens encoder 15 for generating a pulse signal corresponding to the amount of movement of the focus lens 13, and a zoom lens driving unit 16. A photometry unit 18 having a photometric light-receiving element 17, a shutter drive unit 19, a film drive unit 20, a strobe circuit unit 24 having a strobe 23, a display unit 25, a first release switch (1RSW) 26, and A second release switch (2RSW) 27 is connected.
[0018]
In the microcomputer 11, the integration operation of the AF area sensor 12 and the reading control of the sensor data are performed, and the distance measurement calculation is performed by processing the sensor data output from the area sensor 12. Based on the distance measurement calculation result, a drive signal is output from the microcomputer 11 to the focus lens drive unit 14, and the output of the focus lens encoder 15 is monitored to control the position of the focus lens 13.
[0019]
In the zoom lens driving unit 16, a zoom operation is performed under the command of the microcomputer 11.
[0020]
In the photometry unit 18, the photocurrent signal generated by the photometry light-receiving element 17 is processed to generate a photometry output. In the microcomputer 11, this photometric output is A / D converted by the A / D converter 11d to perform photometric exposure calculation.
[0021]
The shutter drive unit 19 drives a shutter (not shown) based on a command from the microcomputer 11.
[0022]
In the film driving unit 20, film driving operations such as auto-loading, one-frame winding, and rewinding are performed under the command of the microcomputer 11.
[0023]
The strobe circuit 24 has a function of causing the strobe 23 to emit light as an auxiliary light source during photographing. The microcomputer 11 performs charging and light emission control of the strobe circuit unit 24. The strobe circuit unit 24 is also operated as AF auxiliary light during the distance measuring operation.
[0024]
The display unit 25 displays information inside the camera on a display element such as an LCD, and is controlled by the microcomputer 11.
[0025]
The first release switch 26 and the second release switch 27 are switches linked to a release button (not shown). The first release switch 26 is turned on when the release button is pushed down in the first stage, and the second release switch 27 is turned on when the release button is pushed down. The microcomputer 11 controls the AF and photometry operations when the first release switch 26 is turned on and the exposure operation and film winding operation when the second release switch 27 is turned on.
[0026]
Next, the distance measuring optical system will be described.
[0027]
FIG. 2 is a diagram showing the arrangement of the optical system and the AF area sensor 12 described above.
[0028]
Here, a so-called passive method for measuring a distance based on an image signal of a subject will be described.
[0029]
In the passive method, when measuring the distance to the subject, the light receiving lenses 31a and 31b are arranged with a base line length B, and the image of the subject 30 is divided into two images to be captured in the imaging region 12a of the AF area sensor 12. Make an image.
[0030]
The relative position difference x between the two images is obtained from the focal length f of the light receiving lens and the base length B by the following formula (1) based on the principle of triangulation.
L = (B · f) / x (1)
FIG. 3 is a diagram showing the relationship between the shooting screen (wide and tele) and the ranging area.
[0031]
Since distance measurement is based on the external light passive method, there is a parallax between the imaging screen and the distance measurement area.
[0032]
As shown in FIG. 3, the areas of the standard, tele, and wide shooting screens 34, 35, and 36 are different from the detection area (ranging area) 33 of the AF area sensor 12.
[0033]
Therefore, the area used for distance measurement is limited according to the focal length information (zoom information) of the imaging optical system.
[0034]
The distance measurement area position correction data corresponding to such a change in focal length is stored in advance in the EEPROM 11e, and is expanded in the RAM 11c together with the initialization of the microcomputer 11. The correction data is referred to according to the zoom operation, and the distance measurement area used for the distance measurement operation in the imaging area of the AF area sensor 12 is determined. Then, a distance measurement calculation is performed based on the sensor data within the distance measurement area range.
[0035]
Further, the microcomputer 11 outputs a control signal to the AF area sensor 12 so that a peak monitor for integration control corresponding to the distance measurement area is generated. Then, the AF area sensor 12 outputs a peak signal within the range of the designated distance measuring area to the microcomputer 11.
[0036]
The microcomputer 11 is controlled so that the integration amount becomes a predetermined level with reference to the monitor signal (see FIG. 6).
[0037]
In this way, the influence of the subject outside the shooting screen is prevented.
[0038]
Even when sensor data is read, the correction data of the distance measuring area corresponding to the shooting screen is referred to so that unnecessary sensor data outside the shooting screen is skipped and not stored in the RAM 11c.
[0039]
Alternatively, a readout range setting signal is output to the AF area sensor 12 so that only necessary sensor data is output.
[0040]
Next, the main routine of the camera in the present embodiment will be described with reference to the flowchart of FIG.
[0041]
When a power switch (not shown) is turned on or a battery is loaded in the camera, the operation of the microcomputer 11 is started and the sequence program stored in the ROM 11b is executed.
[0042]
That is, first, in step S1, each block in the camera is initialized. Then, the data stored in the EEPROM 11e is expanded in the RAM 11c.
[0043]
Next, in step S2, the state of the first release switch 26 is detected. If the first release switch 26 is not turned on, the process proceeds to step S8.
[0044]
When the first release switch 26 is turned on in step S2, the process proceeds to the subsequent step S3 and the AF operation is executed. Next, in step S4, photometry and exposure calculation are performed.
[0045]
In step S5, the state of the second release switch 27 is detected. If the second release switch 27 is not turned on, the process proceeds to step S2.
[0046]
On the other hand, when the second release switch 27 is turned on, the process proceeds to step S6, and the film is exposed by the shutter operation. Next, in step S7, one frame of the film is wound up. Thereafter, the process proceeds to step S2.
[0047]
In step S8, the input state of switches other than the first release switch 26 and the second release switch 27 is detected.
[0048]
In step S8, if there is no other switch input, the process proceeds to step S2. On the other hand, if there is a switch input other than the first release switch 26 and the second release switch 27, the process proceeds to step S9, and processing corresponding to the switch input is executed. For example, zoom-up / down processing is performed in response to a zoom switch up / down input. Thereafter, the process proceeds to step S2.
[0049]
Next, the AF operation will be described with reference to the flowchart of FIG. 5 and the timing chart of FIG.
[0050]
First, in step S11, an integration control signal is output from the AF area sensor 12, and an integration operation is performed. The AF area sensor 12 outputs a monitor signal corresponding to a peak (brightest pixel) output within a predetermined range. While referring to this monitor signal, the integration time is adjusted so that the amount of light received by the light receiving portion of the AF area sensor 12 is appropriate (see FIGS. 6A and 6B).
[0051]
Next, in step S <b> 12, the read clock CLK is output to the AF area sensor 12. Thereby, sensor data (pixel data) is output to the A / D converter 11d, A / D converted, read out, and stored in the RAM 11c (see FIGS. 6C and 6D).
[0052]
In step S3, a night view determination routine is started. In a succeeding step S14, it is determined whether or not it is a night scene. If the scene is a night scene, the process proceeds to step S15 to execute night scene processing. On the other hand, if it is not a night scene, the process proceeds to step S16 and normal processing is executed.
[0053]
Thereafter, when the focus lens 13 is driven in step S17, the routine is exited.
[0054]
The above-described steps S13 to S16 constitute a subroutine “night scene determination process”.
[0055]
Next, the night view determination / processing routine will be described with reference to FIGS.
[0056]
FIG. 7 is a flowchart (corresponding to steps S13 to S16 in FIG. 5) for explaining the operation of the subroutine “night scene determination process”.
[0057]
First, in step S21, it is determined whether or not the brightness is low. This is because the average value of the luminance data of each pixel is obtained from the sensor data of all the imaging areas of the AF area sensor 12 and the integration time, and whether or not the luminance is low is determined by whether or not it is smaller than a predetermined value. It is.
[0058]
In step S22, the distribution of high-luminance pixels is examined. Here, pixels of sensor data showing a value larger than a predetermined level are picked up. Then, it is determined whether or not there are many areas where the distribution continues are smaller than a predetermined value.
[0059]
If both of the above steps S21 and S22 satisfy the conditions, it is determined that the scene is a night scene, and the process proceeds to step S23 in the night scene mode. On the other hand, if any one of the conditions is not satisfied, it is determined that the normal mode is set, and the process proceeds to step S31.
[0060]
In step S <b> 23, the strobe 23 is pre-flashed from the strobe circuit unit 24. At that timing, the AF area sensor 12 is integrated, and the reflected light from the subject due to the strobe pre-emission is detected (see FIGS. 6A, 6B, and 6E).
[0061]
Next, in step S24, sensor data is read from the AF area sensor 12 (see FIG. 6C). In step S25, the difference between the sensor data at the time of normal integration without pre-emission and the sensor data at the time of pre-emission integration is obtained.
[0062]
Then, in step S26, it is determined whether or not there is a difference greater than or equal to a predetermined value for each predetermined distance measurement area. Here, for an area where the difference in sensor data is large, the process proceeds to step S27 and a known distance measurement calculation is performed (see FIG. 14). On the other hand, if it is not more than the predetermined value, the process proceeds to step S30.
[0063]
Next, in step S28, it is determined whether or not the distance measurement result is a short distance. Here, in the case of a short distance, the process proceeds to step S29, and a so-called night view portrait mode in which a person is photographed against a night view is set as the exposure mode. In the night view portrait mode, the strobe light is irradiated so that the main subject at a short distance is appropriately exposed, and the exposure time is set to be long for the shutter so that the background night scene is also properly exposed.
[0064]
If it is not a short distance in step S28 and if there is no difference greater than a predetermined value in step S26, the process proceeds to step S30, and the normal night view mode for shooting the night view of the normal landscape is set.
[0065]
In the normal night view mode, as the exposure mode, the flash 23 does not emit light, and the exposure time of the shutter is lengthened so that the night view is properly exposed.
[0066]
When the mode is not the night view mode, the normal mode is selected, and in step S31, a predetermined distance measurement calculation is performed for each predetermined area, and the distance measurement result on the closer side is selected.
[0067]
Next, a night scene determination method will be described.
[0068]
FIG. 8 shows a typical scene in which a person is photographed against a night view. In this case, street lamps 38a to 38d, a neon sign 39, and the like are arranged behind the main subject 40.
[0069]
FIG. 9 is a diagram three-dimensionally showing sensor data of the AF area sensor 12 in such a shooting scene.
[0070]
Therefore, the night scene scene determination has the following characteristics.
That is,
(A) The overall brightness is low.
The luminance for each pixel or each predetermined area is obtained, the average value is calculated, and compared with the predetermined value.
(B) The high luminance portions are small in area and scattered.
(C) The low luminance portion occupies a large area.
[0071]
FIG. 10 is a distribution diagram showing the relationship between luminance and area by calculating the areas of continuous high-luminance portions and low-luminance portions.
[0072]
As shown in FIG. 10, the night scene is determined based on the ratio of the areas of the high luminance portion and the low luminance portion.
[0073]
Next, another operation example of the subroutine “night scene determination process” will be described with reference to the flowchart of FIG.
[0074]
First, in step S41, the average brightness and the predetermined threshold B _th Are compared. Next, in step S42, the number of portions where pixels having higher luminance than the predetermined value are continued is counted (Sa), and in the subsequent step S43, the number of portions where pixels having lower luminance than the predetermined value are consecutive is counted. (Sb).
[0075]
In step S44, the number of areas Sa is compared with a predetermined determination value m. Subsequently, in step S45, the number of areas Sb is compared with a predetermined determination value n.
[0076]
In steps S44 and S45, when Sa> m and Sb <n are satisfied, the night scene is determined and the night scene mode is set. Otherwise, it is determined that the scene is not a night scene, and the normal mode is entered.
[0077]
The subsequent processing operations of steps S46 to S53 and step S54 for executing the night view mode and the normal mode are the same as steps S23 to S30 and step S31 in the flowchart of FIG. .
[0078]
Here, the night view portrait mode and the normal night view mode described above will be described.
[0079]
FIG. 12 is a diagram three-dimensionally showing AF area sensor data when the flash area is pre-flashed and the AF area sensor 12 integrates in the shooting scene of FIG.
[0080]
FIG. 13 is a diagram three-dimensionally showing data obtained by comparing the data without pre-light emission and the data with pre-light emission and extracting a portion having a difference.
[0081]
After standardizing both data with the luminance peak value, a difference is taken for each corresponding sensor data or area.
[0082]
As described above, when a subject such as a person is present at a short distance, a difference occurs in the image, and therefore it is determined that the main subject is present in this portion (night scene portrait mode).
[0083]
Then, ranging calculation is performed only for the area where the difference occurs (see FIG. 14).
[0084]
Next explained is the second embodiment of the invention.
[0085]
The second embodiment is a modification of the night scene determination method in the first embodiment described above.
[0086]
FIG. 15 is a diagram showing the contrast distribution of AF area sensor data.
[0087]
As a specific contrast value, the sum of absolute values of differences between the sensor data of one pixel and the sensor data of the surrounding pixels is calculated for each pixel, and the above contrast values are summed for the area corresponding to the shooting screen. The
[0088]
In the case of a night scene, the brightness difference between the high brightness part and the low brightness part is large, and thus the contrast becomes large.
That is,
(D) The average brightness is low. Same as (a) above.
(E) The sum of contrasts in the shooting screen is greater than a predetermined value.
[0089]
The sum of the contrast for each predetermined area is obtained, and the contrast is added to all the areas corresponding to the photographing screen and compared with a predetermined value.
[0090]
Next, the operation of the subroutine “night scene determination processing” in the second embodiment will be described with reference to the flowchart of FIG.
[0091]
First, in step S61, the average brightness and the predetermined value B _th Are compared. Next, in step S62, the overall photographing screen contrast and the predetermined threshold C _th Are compared.
[0092]
In steps S61 and S62, the average luminance <B _th , Contrast> C _th When the above condition is satisfied, it is determined that the scene is a night scene. Otherwise, the normal mode is set.
[0093]
The subsequent processing operations of Steps S63 to 70 and Step S71 for executing the night view mode and the normal mode are the same as Steps S23 to S30 and Step S31 in the flowchart of FIG.
[0094]
Next explained is the third embodiment of the invention.
[0095]
The third embodiment differs from the first embodiment described above in the determination of the night view portrait mode and the normal night view mode.
[0096]
FIG. 17 is a graph showing the relationship between the luminance and the number of pixels (or the number of areas) of the corresponding luminance.
[0097]
As shown in FIG. 17, in the night scene, the distribution is biased between the low luminance part and the high luminance part, and the distribution of the medium luminance part is small (the solid line part in the figure).
[0098]
When the main subject exists at a short distance, the distribution is different between the case without pre-light emission and the case with pre-light emission, and the medium luminance portion increases when there is pre-light emission (the broken line portion in the figure).
[0099]
When the subject is not close, there is almost no change in the distribution.
[0100]
From the above,
(F) When the distribution is biased between the high luminance portion and the low luminance portion and the distribution is small in the middle luminance portion, the night scene is determined.
(G) When there is a change in the distribution between the absence of pre-light emission and the presence of pre-light emission, it is determined that a person is photographed against a night scene.
(H) If there is no change in distribution between pre-emission and pre-emission, it is determined as a normal night scene that captures a night scene of a normal landscape.
[0101]
Next, the operation of the subroutine “night scene determination process” in the third embodiment will be described with reference to the flowchart of FIG.
[0102]
In step S81, first, the number of pixels having a luminance higher than a predetermined value in the distance measurement area corresponding to the shooting screen is counted to be BHC. Next, in step S82, the number of pixels included in the predetermined medium luminance range is similarly counted and set as BMC. Further, in step S83, the number of pixels having a luminance lower than a predetermined value is similarly counted and set as BLC.
[0103]
In steps S84, S85, and S86, the BMC, BMC, and BLC are respectively compared with predetermined determination values a, b, and c.
[0104]
In steps S84 to S86, when BHC> a, BMC <b, and BMC <c are satisfied, the night scene is determined and the night scene mode is entered. Therefore, in step S87, integration of the AF area sensor 12 is performed while strobe pre-flash is being performed.
[0105]
Next, sensor data is read from the AF area sensor 12 in step S88. Further, in step S89, the number of pixels with medium luminance is counted from the distance measuring area corresponding to the shooting screen and set to BMC ′.
[0106]
In step S90, the BMC 'is compared with a predetermined value b'. Here, in the case of BMC ′> b ′, it is determined that there is a main subject in front of the night view, the process proceeds to step S91, and distance measurement calculation is performed in the area where the medium luminance pixel is increased.
[0107]
In step S92, it is determined whether or not the subject exists at a short distance based on the result of the distance measurement calculation. As a result, when the subject is at a short distance, the process proceeds to step S93 to set the night view portrait mode.
[0108]
If BMC ′> b ′ is not satisfied in step S90, and if it is not a short distance in step S92, the process proceeds to step S94, and the normal night view mode is set.
[0109]
If any of the conditions is not satisfied in steps S84 to S86, the normal mode is assumed and the process proceeds to step S95. Then, ranging calculation for each predetermined area is performed.
[0110]
Here, a new autofocus technique called super combination AF will be described with reference to FIG.
[0111]
Note that the super combination AF is not a combination of the active method and the passive method in a hybrid manner, but the main subject detection is performed using two methods.
[0112]
FIG. 19A is a block diagram showing the configuration of the main part, showing that the subject is being measured by this type of AF.
[0113]
In the figure, a CPU 50 is constituted by a microcomputer for camera control and has a pattern control unit 51 inside. The CPU 50 is connected to the photometry unit 52.
[0114]
The photometry unit 52 includes two light receiving lenses 54 a and 54 b that guide light from the subject 53, two area sensors 55 a and 55 b that receive light from the subject 53, and an A / D converter (ADC) 56. And a stationary light removal circuit 57.
[0115]
Furthermore, a light emitting unit 60 for controlling light emission of the light source 59 and an audio signal generating unit 61 are connected to the CPU 50.
[0116]
In FIG. 19A, light from a subject 53 that has entered from two light receiving lenses 54a and 54b is incident on two area sensors 55a and 55b. In these area sensors 55a and 55b, a subject image is received and subjected to photoelectric conversion. The output is converted into a digital value of each pixel by the A / D converter 56 and supplied to the CPU 50.
[0117]
In addition, when the steady light removal circuit 57 connected to the area sensors 55a and 55b is controlled, a DC light signal that is steadily incident from the subject 53 is removed. Thereby, only pulsed light from the light source 59 is obtained as an output signal.
[0118]
Accordingly, when the CPU 50 controls the light emitting unit 60 and irradiates the light source 59 or the like with the steady light removal circuit 57 activated, the reflected signal light returns from the subject 53 and is displayed on, for example, the area sensor 55a. An image as shown in 19 (b) is formed.
[0119]
FIG. 19B is a diagram illustrating a state where light is incident on a black portion. If such software for analyzing the pattern of the image on the area sensor is incorporated in the CPU 50 and it is determined that the image has a human shape, it can be considered as the main subject.
[0120]
Therefore, distance measurement according to a flowchart as shown in FIG. 20 can be considered.
[0121]
First, in step S101, the light source 59 is irradiated prior to ranging, and only the reflected signal light pattern is extracted by the steady light removal circuit 57 as shown in FIG. Next, in step S102, the pattern of the reflected signal light is determined, and in step S103, the night scene portion is excluded.
[0122]
Then, in step S104, it is determined whether or not this pattern is the main subject from the shape of the person.
[0123]
Here, if the main subject is not detected, the process proceeds to step S105, where brightness information and the like are taken into account, and after the active method or the passive method is selected, the central portion of the screen with a high subject existence probability is emphasized. The distance is measured. Next, in step S106, a sound corresponding to the center distance measurement is generated by the sound signal generator 61.
[0124]
On the other hand, if the main subject is detected in step S104, the process proceeds to step S107 to determine whether the optical signal forming the pattern is weak or whether there is sufficient contrast. That is, in step S107, the distance measuring method projects the signal light from the camera side and measures the distance using the reflected signal light, and the so-called passive that measures the distance based on the image signal of the subject. A selection of which type of method to use is made.
[0125]
That is, if it is determined that the reflected signal light is weak, it is determined that the passive AF is more suitable, and the process proceeds to step S108. Then, in this step S108, the distance measurement is performed by the passive method in which the image signal of the main subject position that has already been obtained is preferentially used. Thereafter, in step S109, a sound corresponding to the passive AF is generated from the sound signal generator 61.
[0126]
On the other hand, when the contrast of the image signal is weak in step S107, the process proceeds to step S110. In steps S110 and S111, the distance measuring light is irradiated again, and active AF based on the reflected signal light is focused on the previously determined main subject position. Thereafter, in step S112, a sound corresponding to the active AF is generated by the sound signal generator 61.
[0127]
If the CPU 50 selects and outputs an audio signal in accordance with these distance measurement methods or whether or not the main subject can be determined, it is easy for the user to understand, and it is possible to perform distance measurement with a sense of security while appealing the features of this super combination AF. It becomes possible.
[0128]
FIG. 21 is an external view of a camera to which the above-described super combination AF is applied as the fourth embodiment of the present invention.
[0129]
Even in a camera to which the above-described super combination AF is applied, the screen in the scene as shown in FIG. 22 is complicated, and the camera may be lost without being able to determine which is the main subject.
[0130]
Basically, as shown in FIG. 22 (a), if priority is given to the pattern of the shape of the person 65 in the middle, focusing is achieved with a considerable probability. However, depending on the conditions, the bin 66 may be mistakenly focused as shown in FIG. 22 (b), or the photographer may focus on the surrounding person 67 as shown in FIG. 22 (c). Sometimes you want to match.
[0131]
In this case, if the CPU determines the next focus candidate by operating the next candidate switch 64 provided on the camera 63 and indicates it by the dot matrix LCD in the finder, the user can understand it. The dissatisfaction of is eliminated.
[0132]
In addition, when applied to a single-lens reflex camera in this way, it is possible to determine whether or not the camera is in focus through the taking lens, so that it becomes easier for the user to check the focus position and provide a camera without failure. be able to.
[0133]
Furthermore, in addition to the above-described embodiment, the following modifications can be considered.
[0134]
When it is determined that the scene is a night scene, the display unit 25 may display a warning for prompting the use of a tripod when the calculated shutter speed is a long time that causes camera shake.
[0135]
In addition, a blinking display may be displayed on the LCD display, or a voice warning may be issued using PCV or the like.
[0136]
Further, when using a film with a magnetic recording unit, a warning display may be performed so that a higher ISO film that does not require a tripod is used. In this case, the ISO sensitivity at the shutter speed at which no camera shake occurs may be displayed on the LCD display.
[0137]
As a result, the photographer can rewind and take out the film currently in the camera with the MRC function, and replace it with a high ISO film, and shoot without using a tripod. It can be carried out.
[0138]
Next explained is the fifth embodiment of the invention.
[0139]
In the fifth embodiment, a case will be described in which the present invention is applied to a digital camera that captures an image with an image sensor.
[0140]
In the case of night scene photography, the digital camera has a problem in that an image becomes unnatural due to a color jump in a high-luminance portion, S / N degradation, and the like. Therefore, it is desired to eliminate the unnaturalness of images in night scene photography.
[0141]
FIG. 23 is a block diagram showing a configuration of a digital camera according to the fifth embodiment.
[0142]
In FIG. 23, the subject light that has passed through the photographing lens 71 is imaged on an image sensor 73 constituted by a CCD or the like via a diaphragm 72. The output of the image sensor 73 is digitally transmitted through a CDS unit 74 that performs correlated double sampling and removes reset noise from the image signal, an S / H unit 75 that constitutes a sample hold circuit, and an A / D converter (ADC) 76. The image signal is supplied to a process processing unit 77 that performs various processes on the image signal. The process processing unit 77 includes an AGC / γ correction unit 77a that performs auto gain control, and a night scene determination unit 77b that determines a night scene from an image signal.
[0143]
The process processing unit 77 controls the aperture 72 through the photometry unit 79 and the aperture control unit 80 to regulate the amount of light incident on the image sensor. The process processing unit 77 is connected to a recording medium 83 for recording compressed still image data via a DRAM 81 for storing an image signal and a compression / decompression unit 82 for compressing the image signal to reduce the amount of data. Yes.
[0144]
Next, the operation of the digital camera configured as described above will be described.
[0145]
The light beam that has passed through the photographing lens 71 and the diaphragm 72 is incident on the image sensor 73. The light incident on the image sensor 73 is photoelectrically converted and then A / D converted by the A / D converter 76 through the CDS unit 74 and S / H unit 75 to be converted into a digital signal. Is done.
[0146]
The process processing unit 77 receives the digital signal and performs processing such as gain control processing and γ conversion processing by the AGC / γ correction unit 77a. In the night scene determination unit 77b, the image data is processed to determine the night scene.
[0147]
In the photometry unit 79, photometric exposure calculation is performed based on the output of the process processing unit 77, and the aperture value of the diaphragm 72 and the electronic shutter speed of the image sensor 73 are calculated. In the aperture controller 80, the aperture 72 is controlled based on the output of the photometry unit 79.
[0148]
The image signal processed by the process processing unit 77 is temporarily stored in the DRAM 81 and then compressed by the compression / decompression unit 82 to reduce the data amount. Then, the still image data compressed by the compression / decompression unit 82 is recorded on the recording medium 83.
[0149]
Next, the night scene determination operation will be described with reference to the flowchart of FIG.
[0150]
First, in step S <b> 121, an image sensor integration operation is performed by the image sensor 73 with respect to the subject light beam captured through the photographing lens 71 and the diaphragm 72. In step S122, the CDS unit 74, the S / H unit 75, and the analog-digital converter 76 read out the image signal.
[0151]
Further, in step S123, the night scene determination unit 77b in the process processing unit 77 calculates the luminance for each divided area (hereinafter referred to as processing by the night scene determination unit 77b).
[0152]
In step S124, the average luminance value and the predetermined value B _th Are compared. Next, in step S125, the divided area contrast and the predetermined value C _th Are compared.
[0153]
In steps S124 and S125, the luminance average value <B _th And divided area contrast> C _th In this case, the scene is determined to be a night scene and the process proceeds to step S126. Further, if any of the conditions is not satisfied in steps S124 and S125, the routine is exited as the normal mode.
[0154]
In step S126, the gain of the AGC / γ correction unit is reduced as the night view mode.
[0155]
In the night view determination unit 77b, the light receiving area of the image sensor 73 is divided into a plurality of divided areas as shown in FIG.
[0156]
The above-mentioned divided area contrast represents a value obtained by calculating a difference in luminance value with respect to each divided area for each divided area, obtaining a sum of absolute values thereof, and further adding the above values of all divided areas.
[0157]
At a low luminance such as a night scene, the gain of the AGC / γ correction unit 77a is set very high, so that the noise in the dark part of the night scene becomes conspicuous. Therefore, it is possible to suppress the occurrence of noise by automatically determining the night scene and reducing the gain.
[0158]
Further, as a modification of the above-described fifth embodiment, the process of step S126 in the flowchart in FIG. 24 can be performed as follows.
[0159]
That is, when the night scene mode is determined, the color is improved by changing the compression characteristics of the high-luminance portion.
[0160]
The high luminance portion compression characteristics of the AGC / γ correction unit 77a are changed as shown in FIG. 26 to improve the latitude, prevent over-whitening and improve the color.
[0161]
As described above, in the night scene, the noise reduction in the low luminance part, the latitude and the color in the high luminance part are improved, and a natural image can be obtained even in the night scene.
[0162]
In addition, according to the said embodiment of this invention, the following structures can be obtained.
[0163]
(1) A camera that distinguishes a night scene based on an imaging output of an image sensor and sets a shooting mode suitable for the night scene.
[0164]
(2) an image sensor for imaging a subject;
Discriminating means for discriminating a night scene based on the output of the image sensor;
Shooting mode setting means for setting a shooting mode based on the output of the discrimination means;
A camera comprising:
[0165]
(3) The camera according to (1) or (2), wherein the imaging element is an AF area sensor.
[0166]
(4) image detection means for detecting the luminance distribution in the shooting screen;
From the output result of the image detection means, a discrimination means for discriminating a region where the luminance within a predetermined range is continuous,
Area determining means for determining the area of the determined region;
A camera characterized by comprising:
[0167]
(5) image detection means for detecting the luminance distribution in the shooting screen;
From the output result of the image detection means, a determination means for determining the shooting mode based on the average brightness information and the area determination result of the area that continuously outputs the predetermined brightness,
A camera characterized by comprising:
[0168]
(6) The discrimination means discriminates the night scene based on the average of the output of the image sensor, the area of the portion higher than the predetermined luminance, and the area of the portion lower than the predetermined luminance. The camera according to (1).
[0169]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a camera that is easy to use because a shooting scene such as a night view is discriminated based on the imaging signal of the area sensor and the camera operation is performed accordingly.
[Brief description of the 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 diagram showing an arrangement of the optical system and AF area sensor 12 in FIG.
FIG. 3 is a diagram showing a relationship between a photographing screen (wide and tele) and a distance measuring area.
FIG. 4 is a flowchart illustrating a main routine of the camera in the first embodiment.
FIG. 5 is a flowchart for explaining an AF operation;
FIG. 6 is a timing chart for explaining an AF operation.
FIG. 7 is a flowchart for explaining an operation of a subroutine “night scene determination process”;
FIG. 8 is a diagram showing a typical scene in which a person is photographed against a night view.
9 is a diagram three-dimensionally showing sensor data of the AF area sensor 12 in a shooting scene as shown in FIG.
FIG. 10 is a distribution diagram showing the relationship between luminance and area by calculating the areas of continuous high-luminance portions and low-luminance portions.
FIG. 11 is a flowchart illustrating another operation example of the subroutine “night scene determination processing”.
12 is a diagram three-dimensionally showing AF area sensor data when the AF area sensor 12 integrates by pre-flashing the strobe in the shooting scene of FIG. 9;
FIG. 13 is a diagram three-dimensionally showing data obtained by comparing the data without pre-light emission and the data with pre-light emission and extracting a portion having a difference.
FIG. 14 is a diagram showing a selected ranging area for a shooting screen when a subject such as a person exists at a short distance;
FIG. 15 is a diagram illustrating a contrast distribution of AF area sensor data for explaining a second embodiment of the present invention.
FIG. 16 is a flowchart for explaining the operation of a subroutine “night scene determination process” in the second embodiment;
FIG. 17 is a graph for explaining the third embodiment of the present invention and showing the relationship between the luminance and the number of pixels (or the number of areas) of the corresponding luminance.
FIG. 18 is a flowchart illustrating an operation of a subroutine “night scene determination process” in the third embodiment.
FIG. 19 is a diagram for explaining a new autofocus technique referred to as super combination AF.
FIG. 20 is a flowchart for explaining a distance measuring operation in the super combination AF.
FIG. 21 is an external view of a camera to which the above-described super combination AF is applied as a fourth embodiment of the present invention.
FIG. 22 is a diagram for explaining focusing by a camera in the fourth embodiment.
FIG. 23 is a block diagram showing a configuration of a digital camera according to a fifth embodiment of the present invention.
FIG. 24 is a flowchart for explaining operation of night scene determination according to the fifth embodiment;
FIG. 25 is a diagram illustrating an example in which a light receiving area of an image sensor 73 is divided into a plurality of divided areas.
FIG. 26 is a diagram showing a high luminance portion compression characteristic of the AGC / γ correction unit 77a.
[Explanation of symbols]
11 Microcomputer,
11a CPU (central processing unit),
11b ROM,
11c RAM,
11d analog-to-digital (A / D) converter (ADC),
11e EEPROM,
12 AF area sensor,
12a imaging area,
12b processing circuit,
13 Focus lens,
14 Focus lens drive unit,
15 focus lens encoder,
16 Zoom lens drive unit,
17 Light-receiving element for photometry,
18 Metering unit,
19 shutter drive unit,
20 film drive unit,
23 Strobe,
24 Strobe circuit section,
25 Display section,
26 First release switch (1RSW),
27 Second release switch (2RSW),
30 subject,
31a, 31b light receiving lens,
33 Detection area (ranging area) of the AF area sensor 12.

Claims (3)

Imaging means;
A luminance distribution detecting means for detecting a luminance distribution in the photographing screen based on the output result of the imaging means;
A luminance region discriminating unit that discriminates a region where predetermined luminance continues based on the output result of the luminance distribution detecting unit;
Calculating means for calculating the surface product of the region in which the predetermined luminance based on the output of the luminance area discriminating means is continuous,
Based on the output of the calculation means, the result of the determination as to whether or not the area of the region where the distribution of pixels having higher luminance than the predetermined luminance is equal to or less than the predetermined value, and the photographing screen based on the output of the luminance distribution detection means A shooting mode determining means for determining a shooting mode based on the result of the determination as to whether or not the brightness is lower than a predetermined value ;
A camera comprising: The photographing mode determining means is further configured to take a photographing mode based on a determination result of whether or not the area of a region where the distribution of pixels having a luminance lower than the predetermined luminance based on the output of the calculating means is equal to or larger than a predetermined value. the camera according to claim 1, characterized in that to determine.   3. The camera according to claim 1, wherein the shooting mode determination unit selectively determines at least a normal shooting mode and a night scene shooting mode. 4.

Images