JPH01216325A - Exposure determining device for camera or the like - Google Patents

Abstract

PURPOSE:To prevent the occurrence of improper exposure and to perform photographing through only one framing by analyzing photometric distribution in a photographic screen with the position of a main object as a center and determining an optimum weight function. CONSTITUTION:The title device is provided with a means SE for selecting an optional area in the photographic screen, a means CPU for determining the optimum weight function to all the area of the photographic screen based on the photometric distribution or the range finding distribution concerning a selected area and an unselected area and a means for CKT for performing a photometric operation based on the optimum weight function and the photometric result concerning all the area of the photographic screen and determining the optimum exposure. Therefore, the photometric operation is performed by considering the position of the main object and the luminance distribution of the entire screen in whatever position in the photographic screen the main object is set. Thus, the improper exposure can be prevented and a photograph in proper exposure can be taken even if the main object is not set in the center part of the photographic screen.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an exposure amount determining device installed in an optical device such as a camera.

[Prior Art] Currently, most of the cameras sold in Japan are equipped with an automatic focusing device (hereinafter abbreviated as AF) and an automatic exposure control device (hereinafter abbreviated as AF).
The camera is equipped with an AE (hereinafter abbreviated as AE), so all operations such as distance measurement, focusing, photometry, and exposure determination can be performed automatically.

The known AP installed in the camera includes a distance measuring device that measures the distance to the subject within the shooting screen, and a focusing device that moves the photographing lens to the in-focus position based on the measurement result by the distance measuring device. The known distance measuring device was constructed as a center-point distance measuring device that measures only the distance to the subject located at the center of the photographic screen.

On the other hand, the AE installed in the camera includes a photometry device for measuring the brightness of a subject within the shooting screen, and the photometry device may include a partial photometry method, an average photometry method,
2. Description of the Related Art Apparatuses configured based on various photometry methods, such as a center-weighted photometry method and an evaluative photometry method, are known. At present, it is believed that among the various photometry methods described above, the evaluation photometry method determines the most well-balanced exposure for the entire photographic screen and provides a smooth photometry result.

The evaluation photometry method is a method that eliminates the drawbacks of the known center-weighted photometry method, and is constructed based on the following principle. In other words, in this photometry method, the photometry results at the center of the shooting screen where the main subject is expected to be present are compared with the photometry results at the periphery of the shooting screen where the secondary subject is expected to be present, and the difference between the two photometry results is calculated. By performing evaluation based on a predetermined evaluation standard and calculating the photometry distribution within the photographic field using both photometry results and a predetermined evaluation function, the final photometry result that serves as the basis for determining the exposure amount can be obtained.

[Problems to be Solved by the Invention] In a photometry device configured based on a known evaluation photometry method, an evaluation standard is used in which the photometry results at the center of the shooting screen are evaluated with a larger contribution rate than the photometry results at the periphery of the shooting screen. On the other hand, the AF installed in conventional cameras has a center-point distance measuring device as described above.

The main subject was placed at the periphery of the photographic screen using a known camera having an AE with a built-in evaluative metering device as described above and an AF with a built-in center-point distance metering device. When trying to take a photo, first frame the shot so that the main subject is located in the center of the screen, focus on the main subject, then shift the framing so that the main subject is located at the periphery of the screen. Either adopt a shooting method that performs metering and exposure control, or ■ Frame the main subject so that it is located in the center of the screen, focus on the main subject, and perform AE lock to control metering and exposure. After that, it was necessary to adopt a shooting method that frames the main subject so that it is located at the periphery of the screen.

However, if the photograph is taken using the photographing method described in ■ above,
Even though the main subject exists at the periphery of the screen, the known evaluation metering method calculates the photometry results at the center of the screen with a higher contribution rate than the photometry results at the periphery of the screen. In many cases, the exposure amount for the subject becomes significantly worse, resulting in photographs with low clarity of the main subject.

In addition, when shooting using method ① above, objects and backgrounds other than the screen that is actually being photographed are also metered, so not only the exposure for the main subject but also the exposure for the entire shooting screen is significantly degraded. It often ended up being correct.

The reason why the above phenomenon occurs is that both known evaluative metering photometers and known distance measuring devices are designed on the assumption that the main subject will be positioned at the center of the screen. . Therefore, even if the main subject is not positioned at the center of the screen, in order to prevent inappropriate exposure for the main subject or the entire screen, at least use a metering device that does not use center-weighted evaluative metering. It was necessary to have a structure based on an arbitrary point type evaluation photometry method.

Therefore, it is an object of the present invention to eliminate the risk of inappropriate exposure for the main subject and the entire photographic screen, no matter where the main subject is positioned within the shadow screen, and to allow only one framing. An object of the present invention is to provide a novel exposure amount determining device that can configure a camera capable of taking pictures.

[Means for Solving the Problems] The exposure amount determining device according to the present invention includes a photometry means that separately measures the light of a plurality of divided regions obtained by dividing a photographing screen into a plurality of regions, and selects an arbitrary region from among the divided regions. and determining an optimal weighting function for all the divided regions within the photographic screen based on the photometric distribution of the regions selected by the divided region selection means and the regions not selected by the selection means. Weighting function determining means, and means for calculating a photometry result for the entire photographing screen and determining an exposure amount based on the optimal weighting function determined by the weighting function determining means and the photometry results for all divided areas. It is characterized by the fact that

[Function] In the device of the present invention, the position where the main subject is present can be arbitrarily specified by the divided area selection means, and the photometric distribution within the shooting screen is analyzed centering on the position of the main subject, and each division An optimal weighting function for the region is determined.

[Example] Below, a case will be described in which the exposure amount determination device of the present invention is installed in a single-lens reflex camera.

do.

FIG. 1 is a diagram showing the main parts of the electrical configuration of a single-lens reflex camera equipped with an exposure amount determining device and a multi-point distance measuring device according to a first embodiment of the present invention.

In FIG. 1, SPI to SP9 are photometering elements that separately measure the light of nine divided areas obtained by dividing the shooting screen into nine equal parts, OPI to OP9 are operational amplifiers, and L[11 to Ll19
is a logarithmic conversion element, and the photometric element, operational amplifier, and logarithmic conversion element constitute a detection end of the photometry device. R.E.
is the bias reference power supply that serves as the power source for the detection terminal, MP is the multiplexer consisting of analog gates, etc., AE is the AD conversion circuit, CPU is the evaluation calculation circuit with built-in memory and calculation section, etc., IF is information on the shutter, aperture, etc. cpu
CKT is an exposure control circuit,
Sl#1-5W9 is a divided area selection switch that is closed when the camera user selects an arbitrary area among the nine divided areas that make up the shooting screen, and SE is the switch Sw1.
~A divided area selection circuit, EA, which generates a signal representing the selected area to the CPU when SW9 is closed, and also generates the same signal to the distance measuring element of the distance measuring device described later.
and EB are ranging elements constituting the detection end of the multi-point ranging device mounted on the camera of this embodiment, and AK is the ranging element E.
A focus control circuit performs focus detection and focus control based on the outputs of A and EB, and LN is a photographic lens controlled by the output of the focus control circuit AK.

Among the above-mentioned configurations, the exposure amount determining device of the present invention has a portion that becomes a detection end of the photometric device (i.e., photometric elements SPI to SP).
9 and logarithmic conversion elements LDI to LD9 and operational amplifier O
0 division area selection switches 511~, which are composed of PI~0P9), a multiplexer MP, an AD exchange circuit AE, an evaluation calculation circuit CPU, a division area selection switch SWt~519, and a division area selection circuit SE. The SW9 is disposed, for example, on the back cover of the camera, and is operated by the camera user in response to setting the main subject at an arbitrary position within the shooting screen when the camera user performs framing. It is configured as follows.

The CPU also includes a memory that stores the photometric element output digitized by the AD conversion circuit AE, and a memory that analyzes the distribution of the photometric element output within the photographic screen according to the input signal from the divided area selection circuit SE. a calculation unit that determines the optimal weighting function and calculates the optimal exposure amount based on input from the exposure information input circuit IF, the optimal weighting function, and data such as the photometric element output distribution; and the multiplexer MP and AD.
A sequence control circuit unit that controls the conversion circuit AE and the like is provided.

On the other hand, the multi-point distance measuring device installed in the camera of this embodiment has complete distance measuring elements EA and EB from a CCD area sensor, etc., and the elements EA and EB are arranged in divided areas of the photographing screen. It has a corresponding address. When the address of the ranging element is specified by the input signal from the division area selection circuit SE, the output of the ranging element at that address is input to the focusing control circuit AK, and the shooting screen is divided according to the address. Focus control for the area is performed.

FIG. 2 shows a schematic arrangement of the optical system of the camera of this embodiment. In Figure 2, LN is the above-mentioned photographic lens, QM is a quick return mirror, and S)
I is a shutter, PG is a focusing plate, CL is a condenser lens, PR is a pentaprism, EL is an eyepiece lens, ML is a photometric imaging lens, SP is the photometric element mentioned above,
HN and HM are light splitting blocks with built-in semi-transparent mirrors, A
L is a distance-measuring re-imaging lens for re-forming the image formed on the focus plate PG, and EA and EB are the aforementioned distance-measuring elements. Note that in order to perform highly accurate ranging and focusing using an area type sensor as a ranging element, it is desirable to leave the ranging field of focus plate PG transparent.

FIG. 3(a) shows divided areas At (in this example, i=1 to 9
), and FIG. 3(b) shows the output Si of the photometric element arranged corresponding to the divided area At. In addition,
Photometric elements SPI to SP9 and division area selection switch SW
I to SW9 have their respective serial numbers corresponding to the divided area A1.
The brightness of the divided area A is detected by the photometric element SP5 placed in the divided area As, and when the camera user wants to specify the divided area As, the divided area selection switch SW5 is activated. Injected.

In Fig. 4(a), the main subject is divided area A in Fig. 3(a).
s (i.e., the center of the screen), the divided area selection switch SW5 is turned on by the camera user, and the weighting function Wi(i
=1 to 9). In this case, the photometric output S of the photometric element SP5 in the divided area AS at the center of the screen is evaluated as a photometric distribution output 55w5 multiplied by a weighting function W5 (=16).

FIG. 4(b) shows the weighting function determined by the CPU when the main subject is located in divided area A and the divided area selection switch SWS is turned on, as in the case of FIG. 4(a). Here's another example. In this case, divided area A
The weighting function 8 is selected for the photometric element output S at .

The final photometric output M, which is the basis for determining the exposure rate in the CPU, is expressed as M=Σ5iWi, and +=+ This calculation is performed within the CPU.

The weighting function is based on the output distribution of the photometric elements 5PI-5P9, the usage status of the camera (when the camera is used horizontally and vertically), and which divided area is selected.
Various distributions are prepared in consideration of various factors such as weight functions, and these weight functions are stored in advance in the memory within the CPU. The CPU is used to monitor the usage status of the camera and the photometry element SP.
Output distribution of I to SP9 and the switches SWI to SW
The weighting function to be selected is determined based on various human factors such as the division area selected by 9. For example, when shooting with the camera horizontally, the output SS of the element SP5, which measures the divided area A at the center of the screen, and the output S of the element SP2, which measures the divided area A2 at the sky of the screen, are compared ( S2-3s) If >K (constant value), it is determined that ``the brightness difference between the center of the screen and the top of the screen is large, so there is sky at the top of the screen'', and the contribution of the photometric output at the periphery of the screen is calculated. The evaluation calculation is performed by lowering the ratio and selecting a weighting function as shown in FIG. 4(a).

On the other hand, if (S+-3s)<K, the brightness difference between the center of the screen and the top of the screen is small, so by selecting the weighting function shown in Figure 4(b), the main subject (center of the screen) and the screen The exposure device is set so that the photograph can be taken with a good balance of brightness.

The ranging elements EA and EB constituting the detection end of the multi-point ranging device have a ranging field of view B+-Be (see FIG. 5) divided corresponding to each divided area Ai (FIG. 3) of the shooting screen. ),
The pixels E1 to Es (see FIG. 6) of the distance measuring elements EA and EB correspond to the distance measuring field. Each pixel E, ~E
The position 9 is searched as an address in the X and Y coordinate systems.

Next, the operation of the configuration of the embodiment shown in FIG. 1 will be explained.

In the following, a case will be described in which a camera user wishes to take a photograph in which the main subject is shifted to the left side of the photographic screen.

The camera user holds the camera facing the subject, frames the main subject X on the left side of the shooting screen as shown in Figure 7, and then presses the camera release button halfway to take the picture. It is assumed that photometry and distance measurement have started. In this case, the main subject X is divided into divided areas A+, A4, A? of the photographic screen as shown in FIG. The camera user recognizes that the camera is arranged across three areas, so the camera user selects the switches SWI, SW4, and SW7 among the divided area selection switches SWt to SW9 provided on the back cover of the camera. Input operation. When the divided area selection switches SW1, SW4, and SW7 are turned on, a signal indicating that the divided areas AI, A4, and A7 have been selected is generated from the divided area selection circuit SE, and this signal is sent to the CPU and the ranging elements EA and EB. and the address circuit separately. When the signal is applied to the CPU,
The CPU accepts the signal as one element for determining a weighting function to be used in the evaluation photometry calculation, and enters a preparation state for determining the weighting function.

On the other hand, when the signal is applied from the divided area selection circuit SE to the address circuits of the distance measuring elements EA and EB, the distance measuring elements EA
The distance measuring element is set so that the outputs of pixels E1, E4 and E of EB and EB are applied to the focus control circuit AK.

When the photometry device and the distance measurement device are activated in response to a half-press of the release button, a photocurrent is applied to each photometry element SPI to SP9 in the photometer according to the brightness of each divided area A, to A9 of the shooting screen. A voltage output (that is, a photometric output 31 to S9) having a value obtained by logarithmically compressing the photocurrent is generated at the output terminal of each operational amplifier OPI to OP9. Further, the photometric outputs 81 to S9 are sequentially input to the AD conversion circuit AE by the multiplexer MP, digitized by the AD conversion circuit AE, and stored in the memory in the CPU. The photometric element output distribution of all divided areas A1-80 of the shooting screen is c
When inputted manually by pu, CPt1 becomes the exposure information input circuit I.
After determining the optimal weighting function based on the input data from F and the input signal from the divided area selection circuit SE, the evaluation photometry calculation described above is performed, and the calculation result is applied as a photometry value to the exposure control circuit CKT, The conditions of exposure devices such as an aperture and a shutter are optimally adjusted via the exposure control circuit IJT.

In this case, the weighting function determined by CPU has a distribution as shown in FIG. 8, for example.

The weighting functions shown in FIGS. 8(a) and (B) are both
This is adopted when framing is performed in which the main subject X is placed biased to the left side of the photographic screen as shown in FIG.

On the other hand, on the ranging device side, as described above, each pixel E, E4, and E7 of the ranging elements EA and EB is controlled by the signal applied from the divided area selection circuit SE to the address circuits of the ranging elements EA and EB. Only the output of the focus control circuit AK
Therefore, distance measurement is performed for all divided areas A1 to A of the shooting screen, but focusing is performed only for divided areas A1, A4, and Aγ, and the focus control circuit AK outputs The photographic lens LN focuses on the main subject X on the left side of the photographic screen.
The camera is moved to focus on the subject.

Note that the three selected divided areas A I + A 4 ,
A? If the distance measurement results are different, focusing is performed on the center value of the distance measurement results, and the distance measurement results for two areas are almost the same, but the distance measurement results for one area are different. In such a case, a photograph with good focus and exposure can be obtained over the entire main subject by configuring the camera to focus on the one whose distance measurement results are approximately the same value.

In the embodiment shown in Fig. 1, even if the main subject is not set at the center of the shooting screen, evaluation metering is performed centered on the subject, resulting in significant inappropriate exposure of the subject. This eliminates the risk of the entire frame being exposed incorrectly, and since the main subject, which is not in the center of the frame, is also in focus, only one framing is required. be able to.

In the embodiment shown in FIG. 1, the exposure amount determining device is configured so that the photometry result influences the evaluation photometry calculation, but the exposure amount determination device is configured so that the evaluation photometry calculation is performed based on the output distribution of the distance measuring element. A quantity determining device may also be configured.

FIG. 9 shows an exposure amount determining device according to a second embodiment of the present invention configured to perform evaluation photometry calculations based on the output distribution of the distance measuring element, that is, the brightness and contrast of the subject, and a device equipped with the device. 1 is a diagram illustrating a camera, and parts indicated with the same reference numerals as in FIG. 1 are the same as the constituent parts in FIG. 1.

The exposure amount determination device of this embodiment differs from the device of the first embodiment in that a multi-point distance measuring device is incorporated as a component. That is, in the device of this embodiment, all outputs of the ranging elements EA and EB are input to the CPU, and cp
u is configured to determine an appropriate weighting function according to the output of the divided area selection circuit SE and the output distribution of the ranging element.

In other words, in this embodiment, the contrast of the image of the subject can be directly detected using a CCD area sensor, etc., so for example, if the image output of the selected divided area is evaluated and determined, and the required image output ratio is 1:1000, In order to do this, it is necessary to select a weighting function that places a significant weight on this selected segmented area, otherwise it is difficult to fit this image within the latitude of the film.

Furthermore, if the image output ratio is about 1:1Q, the image of this selected divided area can be reproduced no matter where it is placed within the latitude of the film. All you have to do is decide.

In addition to the weighting functions Wi determined in CPt1 of this embodiment, for example, those shown in FIGS. 10(a) and 10(b), there are many other types of weighting functions available.

The two types of weighting functions shown in FIGS. 10(a) and (b) are for the case where the main subject X is placed to the left of the shooting screen as shown in FIG. is placed at the center of the photographic screen, a weighting function as shown in FIG. 4 is selected.

However, in both the embodiments shown in FIGS. 1 and 9, when the difference in brightness of all objects within the photographic screen is small, which of the weighting functions Wi shown in FIGS. 4 and 8 and the weighting function Wi shown in FIG. 10 is selected. In such a case, no matter which of the weighting functions Wt in FIGS. 4 and 8 or the weighting function Wt in FIG. 10 is selected, the same evaluation photometry value is obtained and the same exposure determination is performed. It is necessary to set a correlation coefficient between the weighting function Wi in FIG. 4 and the weighting functions Wt and Wi in FIGS. 8 and 10. This correlation coefficient can be determined, for example, by the following theory.

The sum ΣWi of the weighting functions Wl shown in FIG. 4(a) is 40,
The sum ΣWi of the weighting functions Wi shown in FIG. 4(b) is also 40,
The sum Σwi of the weighting functions Wi shown in FIG. 10(a) is 33
, the sum ΣWi of the 1@1 weighting functions Wi shown in FIG. 10(b) is 301 (since the weighting function W1 shown in FIG. 8 is the same as the weighting function shown in FIG. Description of the weighting functions in the figure will be omitted.

). Therefore, when performing evaluation photometry calculation using the weighting function shown in FIG. 10(a), it is necessary to set the value multiplied by the correlation coefficient □ as the final evaluation photometry value. That is,
Evaluation side when using the weighting function shown in FIG. 10(a) Note that also in the embodiment shown in FIG. Then, the output of the pixel corresponding to the specified divided area from the ranging elements EA and EB is input to the focus control circuit AK, and the focus control circuit AK performs focus control for the specified divided area. This is the same as the first embodiment.

In the embodiment shown above, the weighting function is determined and selected within the evaluation calculation circuit CPU, but the weighting function selection and determination are configured within the divided area selection circuit SE. Good too. Alternatively, the weighting function may be determined by inputting only the output of a designated pixel of the ranging element to the CPU.

[Effects of the Invention] As explained above, the exposure amount determination device of the present invention includes a means for selecting an arbitrary area within the photographic screen, and a photometry method for the area selected by the means and the area not selected. means for determining an optimal weighting function for all areas within the photographing screen based on the distribution or distance measurement distribution; and performing photometry calculation based on the optimal weighting function and photometry results for all areas within the photographing screen. and a means for determining the optimum exposure amount.In the device of the present invention, no matter where the main subject is set within the shooting screen, the photometry calculation takes into account the main subject position and the brightness distribution of the entire screen. Therefore, there is no risk of improper exposure, and it is possible to take a photograph with proper exposure without setting the main subject in the center of the photographic screen.

It is clear that the present invention is not limited to cameras, but can be applied to various optical devices.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a part of the electrical configuration of a single-lens reflex camera equipped with an exposure amount determining device and a multi-point distance measuring device according to the present invention, and FIG. 2 is a diagram showing the optical structure of the camera shown in FIG. FIG. 3(a) is a diagram showing a schematic structure of the system, FIG. 3(a) is a diagram showing an example of dividing the photographing screen, and FIG. 3(b) is a diagram showing the arrangement of photometric elements that separately measure each divided area of the photographing screen. FIGS. 4(a) and 4(b) are diagrams showing the photometric output of the photometric element corresponding to the photographing screen, and FIGS. Figure 5 is a diagram showing an example of division of the distance measuring field of the multi-point distance measuring device;
Figure 6 is a diagram showing the pixels in the distance measuring element of the multi-point distance measuring device in correspondence with the photographing screen and distance measuring field of view, and Figure 7 is the photographing screen when the main subject is positioned on the left side of the photographing screen. Figures 8(a) and 8(b) show examples of weighting functions determined by the exposure amount determining device when the main subject is positioned as shown in Figure 7, corresponding to the photographic screen. FIG. 9 is a diagram showing the electrical configuration of an exposure amount determining device according to a second embodiment of the present invention, and FIG. 10(a). (b) is a diagram showing an example of a weighting function used in the apparatus shown in FIG. 9. RE...Reference power supply for bias, SPI~SP9...Photometering element needle...Multiplexer-1^E...AD conversion circuit,
cpu...Evaluation calculation circuit, SE...Divided area selection circuit, 5WI-5W9...Divided area selection switch, E^ and Et...Distance measuring element, A...Focusing control circuit, CK-D・
...Exposure control circuit. Figure 2 L - Figure 3 (α) Figure 3 (b) Ai, SL Figure 4 (α) Figure 4 (b) Figure 5
Figure 6 Figure 7

Claims (1)

[Scope of Claims] 1. Photometry means for separately measuring the light of a plurality of divided regions obtained by dividing a screen for photographing or observation into a plurality of parts, and divided region selection means for selecting an arbitrary region from among the divided regions; weighting function determining means for determining an optimal weighting function for all divided regions in the screen based on photometric distributions regarding the regions selected by the divided region selecting means and the regions not selected by the selecting means; Exposure amount of a camera, etc., comprising means for calculating the photometry result for the entire screen based on the optimal weighting function determined by the function determining means and the photometry result for the entire divided area, and determining the exposure amount. decision device. 2. A photometry means that separately measures the light of a plurality of divided areas obtained by dividing a photographing or observation screen into a plurality of parts, a distance measuring means that separately measures the distance of each of the divided areas, and a distance measuring means that measures the distance of each of the divided areas separately, and A divided area selection means for selecting a divided area, and an optimal weight for all divided areas in the screen based on the distance measurement output distribution of the distance measuring means for the screen and the divided area selected by the divided area selection means. weighting function determining means for determining a function; and means for calculating a photometry result for the entire screen and determining an exposure amount based on the optimal weighting function determined by the weighting function determining means and the photometry results for all the divided areas. An exposure amount determination device for a camera, etc., comprising: