JP2012145862A - Ettl photometry system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that, when using a linear sensor as a photometric sensor, since a dynamic range is narrow, without performing pre-emission twice in performing ETTL, an accurate photometric value may not be obtained occasionally and if pre-emission is performed twice, since it takes time relative to one-time of pre-emission, a release time lug may occur or if pre-emission is performed twice together with optical wireless communication in multi-lamp strobo photographing, charged power may be exhausted.SOLUTION: An imaging apparatus includes an optical system (200) which forms a subject image on an imaging plane, a sensor (106), a processing circuit (111) which processes the output of the sensor, and an illuminator (300) for lighting up a subject. The imaging apparatus further includes means for mixing signal charges generated by pixels of the same color in the sensor (106) just for a predetermined number in exposure of pre-emission of the illuminator (300) and means for changing the number of signal charges to be mixed at an interval of predetermined lines, and calculates the quantity of main emission light from image data obtained through such a method.

Description

  The present invention relates to a photometric system for performing ETTL using a linear output type sensor.

  In recent years, with single-lens reflex cameras, a system has been found in which an image signal is obtained by a photometric sensor in the penta portion immediately before shooting, tracking is performed by processing the image signal, and photometry is performed based on the image signal. It has become.

  When subject tracking is performed, a photometric sensor having at least several hundred pixels is required, and therefore, it is necessary to use a linear output type sensor such as a CCD or CMOS.

  Since the linear output type sensor has a narrow dynamic range that can be obtained in a certain accumulation time, it is necessary to perform photometry while appropriately changing the accumulation time according to the brightness of external light during photometry.

  In addition, when performing ETTL using a linear output type sensor, the reliability of the photometric value may not be sufficiently obtained due to insufficient or too much light emission in one pre-emission.

  Therefore, a method of determining whether or not to perform pre-flash again from the photometric result of the reflected light of the first pre-flash and calculating the actual flash amount at the time of shooting by performing the second pre-flash if necessary is conceivable. ing. (Patent Document 1).

JP 2000-187266 A JP 2005-117192 A

  However, in the above method, if the pre-flash is performed twice, it takes longer time than the case of the pre-flash once, so there is a problem that a release time lag occurs. When the pre-emission is performed twice, there is a problem that the battery is fully charged.

The ETTL photometric system according to claim 1 of the present invention comprises:
An optical system (200) for forming a subject image on the imaging surface;
A sensor (106);
A processing circuit (111) for processing the output;
In an imaging apparatus having an illumination device (300) for illuminating a subject,
Means for mixing a predetermined number of signal charges generated by pixels of the same color of the sensor (106) during the pre-emission exposure of the illumination device (300);
Means for changing the number of mixed signal charges for each predetermined row;
The main light emission amount is calculated from the image data obtained by the above method.

  The ETTL photometric system according to claim 1, wherein a sensor in which each color pixel is arranged in a stripe shape in the vertical direction is used as the sensor (106).

  3. The ETTL photometric system according to claim 1, wherein the ETTL photometric system according to claim 1 divides image data of different numbers of mixtures for each number of mixes, and performs calculation with the same number of blocks.

  The ETTL photometry system according to claim 4, wherein the pre-emission light amount and the accumulation time of the sensor (106) are changed from the distance information to the subject and the luminance value at the time of real-time photometry. system.

  The ETTL photometric system according to claim 5 performs normal readout at the time of natural light metering, and performs readout in which the number of mixtures is changed every predetermined row only during pre-precharge accumulation and pre-light emission accumulation. The ETTL photometric system described.

  The ETTL photometric system according to claim 6 is a system in which there are a plurality of sub illumination devices in addition to the main illumination device (300), and the sub illumination devices in each group determine the main light emission amount by one pre-emission. The ETTL photometric system according to claim 1.

  By changing the pixel mixture number in each row, the dynamic range is expanded, and the main light emission amount can be determined by one pre-light emission. This reduces the release time lag. In addition, the multi-flash strobe is less likely to be fully charged.

Camera system configuration diagram A diagram showing how signal charges are mixed into a pixel Flowchart for explaining the operation of the imaging apparatus and illumination apparatus of the present invention. Table that calculates the pre-photometry and pre-time metering accumulation time from subject distance and external light brightness The figure for demonstrating a mode that the image obtained by the readout method of this photometry system is isolate | separated for every mixing number The figure for demonstrating the division | segmentation of the photometry area | region of this photometry system Control flowchart for multi-flash

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[Example 1]
Examples of the present invention will be described below.

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

  Reference numeral 100 denotes a camera body, 200 denotes a lens, and 300 denotes a strobe. First, the configuration within the camera body 100 and the lens 200 will be described. A microcomputer CPU (hereinafter referred to as a camera microcomputer) 101 controls each part of the camera 100. Reference numeral 102 denotes an image sensor such as a CCD or CMOS including an infrared cut filter, a low-pass filter, and the like, and an image of a subject is formed by the lens 200 at the time of photographing. Reference numeral 103 denotes a shutter that shields the image sensor 102 when not photographing, and opens when photographing to guide the light beam to the image sensor 102. A half mirror 104 reflects a part of light incident from the lens 200 when not photographing, and forms an image on a focusing plate 105. A photometric sensor 106 performs photometry and tracking by using an image sensor such as a CCD or a COMS. In this embodiment, an example in which a striped CCD is used as a photometric sensor will be introduced. The CCD has M × N pixels of vertical M pixels and horizontal N pixels. In addition, the photometric sensor expects a subject image formed on the focus plate 105 from a position of a glare through a pentaprism 107 described later. A pentaprism 107 guides the subject image on the focusing plate 105 to the photometric sensor 106 and an optical viewfinder (not shown). Reference numeral 108 denotes a memory such as a RAM or a ROM connected to the CPU 101. Reference numeral 109 denotes a focus detection circuit, which is an AF mirror 110, and performs distance measurement by guiding a part of the light incident from the lens and passing through the half mirror 104 to a distance measurement sensor in the focus detection circuit. Reference numeral 111 denotes a CPU (hereinafter referred to as ICPU) for image processing / calculation of the photometric sensor 106, which calculates the main flash emission amount. Reference numeral 112 denotes a memory such as a RAM or a ROM connected to the ICPU 111. This time, a CPU dedicated to the photometric sensor is prepared as in 111, but the processing may be performed by the camera microcomputer 101. Reference numeral 201 denotes a CPU (hereinafter referred to as LPU) in the lens, which sends distance information to the camera microcomputer to the camera microcomputer.

  Next, the configuration of the strobe 300 will be described.

  Reference numeral 301 denotes a microcomputer SCPU (hereinafter referred to as a strobe microcomputer) that controls the operation of each unit of the strobe 300. Reference numeral 302 denotes a light quantity control device, which includes a booster circuit for boosting the battery voltage and lighting a light source 305 described later, a current control circuit for controlling start and stop of light emission, and the like. A zoom optical system 303 includes a panel such as a Fresnel lens and the like, and changes the irradiation angle of the strobe 300. Reference numeral 304 denotes a reflector, which collects the luminous flux of the light source and irradiates the subject. Reference numeral 305 denotes a light source such as a xenon tube or a white LED.

  Next, pixel mixing will be described with reference to FIG. 2 showing a state where signal charges are mixed.

  In this embodiment, an example in which a stripe CCD in which R (red), G (green), and B (blue) pixels are arranged in a stripe shape as shown in FIG. 2 will be described. By using a stripe type CCD in this way, it is possible to perform pixel mixing in the vertical direction in the vertical transfer path in an analog manner. In the present embodiment, consider a case where a mixture of one pixel and four pixels is alternately read for each row as shown in FIG. As shown in FIG. 2, the four-pixel mixing is a process of mixing pixels of the same color for four pixels and outputting this as one signal charge. Therefore, in this case, the vertical size of the image data is (2N / 5) pixels. Thus, by acquiring an image of one pixel and four pixels mixed, the dynamic range can be expanded by two stages on the low luminance side as compared with an image without mixing (an image having only one pixel). Here, for example, if the number of mixed pixels is 8 pixels, the dynamic range can be expanded by 3 steps on the lower luminance side and 16 pixels if compared with the case of reading all pixels.

  Next, the sequence of the present invention will be described with reference to the flowchart of FIG.

  First, when ETTL control is started, it is determined in S102 whether or not SW1, which is a half-pressed state of the shutter button, is ON. If ON, the process proceeds to S103.

  In S103, the focus detection circuit 109 is driven to perform a focus detection operation. At this time, lens distance information is obtained, and the LPU 201 transmits it to the camera microcomputer 101 and further transmits it to the ICPU 111 that performs photometric calculation. With this information, the distance (D) from the main subject can be estimated.

  Next, in S104, the brightness value of external light is measured by the photometric sensor 106 (real-time photometry). The real-time photometry at this time is preferably normal readout (not a readout method in which the number of pixel mixtures is changed every predetermined row) in order to determine the accumulation time by repeating photometry many times. Here, the luminance (BV) of external light can be calculated.

  In S105, the pre-photometry & pre-emission accumulation time is calculated from the distance (D) to the main subject obtained in S103 and the external light luminance (BV) obtained in S104 as shown in FIG. Here, the pre-photometry & pre-emission accumulation time is determined from the distance (D) to the main subject and the brightness (BV) of the external light, but either one of them or the other may be determined. It is also possible to always perform photometry with the same accumulation time.

  Next, in S106, it is determined whether or not SW2 which is a photographing start switch is ON. If it is ON, the process proceeds to S107.

  In step S107, the subject luminance immediately before the pre-flash is obtained by the photometric sensor 106. In this pre-photometry, the accumulation time obtained from FIG. 4 is used, and readout is performed by changing the number of pixel mixtures every predetermined row.

  Then, pre-emission is performed in S108, reflected light of the pre-emission is measured in S109, and A / D conversion is performed in S110. In pre-emission photometry, as in pre-emission photometry, the accumulation time obtained from FIG. 4 is used, and readout is performed by changing the number of pixel mixtures every predetermined row.

  Next, in S111, the light emission amount of the main light emission is calculated from the pre-pre-photometry image data obtained above and the image data at the time of pre-light emission.

  An example of the calculation method will be described below.

First, pre-pre-photometry image data is subtracted from image data at the time of pre-emission in each of M × N pixels. As a result, image data of only strobe light excluding the influence of external light can be obtained. Subsequently, the image data obtained from the above (image data at the time of pre-emission)-(image data of pre-pre-photometry) is converted into data without pixel mixing and image data with pixel mixing (4-pixel mixing) as shown in FIG. And to separate. The following calculation is performed on each of the image data of “unmixed image” and “4-pixel mixed image” obtained here. First, the luminance value for each block is calculated by dividing it into I horizontal blocks and J vertical blocks (photometric areas) as shown in FIG. The block size may be determined so that the same number of R, G, and B pixels are included in one block. Each block has a total of m × n pixels of horizontal m pixels and vertical n pixels. If the block size is determined so that the same number of R, G, and B pixels are included in one block, each block has m × n / 3 pixels. An average value Rij of R pixels, an average value Gij of G pixels, and an average value Bij of B pixels in each block are obtained. The luminance value (Yij) of each block is obtained from these Rij, Gij and Bij.
Yij is obtained by the following equation, for example.

Yij = Ra * Rij + Ga * Gij + Ba * Bij
The luminance value Yij for each block can be obtained by entering appropriate values for the mixing ratios Ra, Ga, Ba of the R pixel, G pixel, and B pixel. (For example, Ra = 0.299, Ga = 0.587, Ba = 0.114). Through the above calculation, the luminance value Y1ij of each block of the “non-mixed image” and the luminance Y4ij of each block of the “4-pixel mixed image” are obtained.

Further, each block of the “non-mixed image” and each block of the “4-pixel mixed image” look at substantially the same position, and if both Y1ij and Y4ij are within the dynamic range in a certain block, it can be said that Y4ij≈4 × Y1ij. Next, the pre-emission reflected light luminance value Ys of the entire block is calculated from the values of Y1ij and Y4ij. An example of the method will be described below.

  It is determined whether or not Y4ij exceeds the threshold Ymax in each block, and if it exceeds, the block is considered to be saturated (out of the dynamic range) in the “4-pixel mixed image”. Then, the luminance value Y1ij of the “non-mixed image” at the same position as the block determined to be saturated is used, and the luminance value of the block is set to 4 × Y1ij. By this operation, a block saturated in the “4-pixel mixed image” can be supplemented with an “unmixed image” that can be measured to a higher luminance. This time, it is determined whether to use the value of Y4ij as it is or to use 4 × Y1ij depending on whether or not the luminance value Y4ij for each block is saturated. However, it is determined whether the average value R4ij of the R pixel, the average value G4ij of the G pixel, and the average value B4ij of the B pixel of each block of the “4-pixel mixed image” are saturated. It may be replaced with four times the data R1ij, G1ij, B1ij of “image without mixing”. Further, this time, if the luminance value Y4ij for each block is not saturated, Y4ij is used as it is, and if it is saturated, 4 × Y1ij is used, but when Y4ij is not saturated, Y4ij and 4 × Y1ij An average may be taken.

  The pre-emission reflected light luminance value Ys of the entire block is calculated using the luminance value of each block consisting of Y4ij and 4 × Y1ij generated as described above. The pre-emission reflected light luminance value Ys of the entire block is calculated by weighting the luminance value of each block in accordance with a photometric mode such as evaluation photometry or spot photometry. Alternatively, Ys may be obtained by simply taking the average of all.

  Subsequently, the pre-emission reflected light luminance value Ys is logarithmically converted based on a logarithmic conversion table prepared in advance, and the pre-emission reflected light luminance value Yslog after logarithmic conversion is obtained. A difference DF = Yslog−Yt from the appropriate luminance value Yt (logarithm) is obtained from the obtained pre-emission reflected light luminance value Yslog. The light emission amount Answer of the main light emission is determined from the difference DF (the number of steps different from the appropriate light amount at the time of pre-light emission) and the light emission amount A0 of the pre-light emission.

Answer = A0-DF
This light emission amount Answer is sent to the camera microcomputer, and the light emission amount is sent from the camera microcomputer to the flash microcomputer.

  Finally, in step S112, the camera microcomputer issues a light emission command to the flash microcomputer, and the flash microcomputer controls the light quantity control device 302 to execute the main light emission and perform the main photographing.

  Next, an example of multi-flash strobe control will be described as a second embodiment with reference to the control flowchart of FIG.

  Consider controlling the slave strobes of the three groups A group, B group, and C group from the master strobe.

  S101 to S106 are as described in the first embodiment.

  In S113, the master strobe issues a command such as the amount of pre-emission to the slave strobes of group A by optical wireless communication.

  S114 to S118 are similar to the method (S107 to S111) described in the first embodiment, and the main emission amount AnswerA of the A group slave strobe is determined from the pre-emission reflected light of the A group slave strobe.

  In S119, it is determined whether or not there is a pre-light emission (a group for which the main light emission amount is not determined). Next, as with the A group, the master strobe issues a command such as the amount of pre-emission to the slave strobe of the B group by optical wireless communication. The main light emission amount AnswerB of the B group slave strobe is determined from the pre-flash reflected light of the B group slave strobe. Subsequently, similarly, the master strobe issues a command such as the amount of pre-emission to the C-loop slave strobe by optical wireless communication. The main emission amount AnswerC of the B group slave strobe is determined from the pre-emission reflected light of the C group slave strobe.

  Finally, in S120 to S124, the master strobe pre-flashes and determines the main light emission amount AnswerM of the master strobe itself.

  In S125, each group and the master strobe emit light with the light emission amounts of Answer A, Answer B, Answer C, and Answer M obtained above.

  As described above, by performing readout by changing the number of pixel mixtures in each row, the dynamic range is expanded, and the main light emission amount can be determined by one pre-light emission. This reduces the release time lag. In addition, in the method of performing the pre-flash twice in the case of the multi-flash, the optical wireless communication has to be performed every time the pre-flash is commanded twice, and the battery is fully charged. In this method, photometry can be performed with one pre-emission, so that it becomes difficult for the battery to be fully charged.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

DESCRIPTION OF SYMBOLS 100 Camera 101 Camera microcomputer 102 Image pick-up element 104 Mirror 105 Focus board 106 Photometric sensor 107 Penta prism 111 CPU for image processing and calculation
200 Lens 201 Lens microcomputer 300 Illumination device (strobe)

Claims (6)

An optical system (200) for forming a subject image on the imaging surface;
A sensor (106);
A processing circuit (111) for processing the output;
In an imaging apparatus having an illumination device (300) for illuminating a subject,
Means for mixing a predetermined number of signal charges generated by pixels of the same color of the sensor (106) during the pre-emission exposure of the illumination device (300);
Means for changing the number of mixed signal charges for each predetermined row;
An ETTL photometric system characterized by calculating a main light emission amount from image data obtained by the above method.   2. The ETTL photometric system according to claim 1, wherein a sensor in which each color pixel is arranged in a stripe shape in the vertical direction is used as the sensor (106).   2. The ETTL photometric system according to claim 1, wherein image data of different numbers of mixtures is separated for each number of mixtures, and calculation is performed with the same number of blocks.   2. The ETTL photometric system according to claim 1, wherein the amount of pre-emission and the accumulation time of the sensor (106) are changed from distance information to the subject and a luminance value during real-time photometry.   2. The ETTL photometric system according to claim 1, wherein normal reading is performed during metering of natural light, and reading is performed by changing the number of mixtures every predetermined row only during pre-preliminary accumulation and pre-emission accumulation. 2. The system according to claim 1, wherein, in a system having a plurality of groups of sub illumination devices in addition to the main illumination device (300), the sub illumination devices of each group determine the main light emission amount by one pre-emission. The ETTL photometric system described.