JP2989658B2 - Automatic exposure determination method and apparatus and camera using the same - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates generally to an automatic exposure control device for an electronic flash camera, and more particularly to an electronic flash camera in such a camera prior to exposing an electronic flash. The present invention relates to a technique used for determining field characteristics.

[Conventional technology]

To control one or more camera functions,
Automatic exposure controls for electronic flash cameras that illuminate the scene with artificial light using an electronic flash prior to exposure and determine certain field characteristics are known in the photographic art. For example, U.S. Pat.
No. 3,173,347 discloses an automatic camera light source which illuminates an object scene by activating an artificial light source before exposure, and sets a camera aperture using a signal generated by detecting reflection of the illumination from a subject. An exposure control device is disclosed.

U.S. Pat. No. 4,302,084 to Grinwald et al. Discloses a focusing device for a photographic camera that also uses a pre-exposure flash. This focusing device utilizes an electronic flash that sends light to the subject before exposure. The electronic flash light reflected from the subject in the scene is detected and integrated. When the amount of reflected flash light reaches a predetermined level, a suppression circuit is activated to generate a signal to suppress the light emitted from the light source. A timer measures the elapsed time between the start of the electronic flash and the generation of the suppression signal. Using the conversion means, the measured time interval is translated into a distance signal having a functional relationship with the distance between the focusing device and the subject. Thus, this distance signal can be used to adjust the moving elements of the adjustable focus lens system, ie for focusing.

A major advantage of the above described ranging part in Grinwald and other focusing devices is that the distance to the object can be determined over a relatively wide range of object distances. However, this advantage has the major disadvantage that relatively close subject distances cannot be accurately determined. More importantly, however, this type of ranging device consumes a relatively large amount of energy in the ranging process. This is because the light from the electronic flash must continue to illuminate the scene, including the distant subject present, until a predetermined reflected light level that is primarily dependent on subject distance is detected and integrated. Because it does not become. In general, the farther the subject, the higher the energy consumption level.

The high energy consumption in the pre-exposure flash is provided by two separate flash energizations, a main discharge, a capacitor, as provided in the electronic flash device disclosed in U.S. Pat. No. 4,256,995 to Ishida. This is not a problem in the distance measuring device. But,
As in the ranging device disclosed in the aforementioned Grinwald et al. Patent, an electron including a single main discharge capacitor for storing the total charge required to fire an electronic flash both before and during exposure. In flash-based exposure controllers, this excessive consumption of stored charge prior to exposure will excessively limit the amount of charge that can be used to fire the electronic flash during the required time during exposure.

[Problems to be solved by the invention]

The present invention is therefore an electronic flash device having a single main discharge capacitor, wherein the electronic flash device can completely fire the electronic flash both before and during exposure due to the charge of the single capacitor. The main purpose is to provide

Another object of the present invention is to provide an electronic flash camera automatic exposure control device using a pre-exposure flash type object reflectance measurement technique, which can accurately determine the distance to a relatively close subject.

It is yet another object of the present invention to provide an automatic exposure control device for an electronic flash camera that uses an economical and simplified pre-exposure flash subject reflectometry technique.

Other objects, features and / or advantages of the present invention will become apparent from the following detailed description of embodiments which is made with reference to the accompanying drawings.

[Means for solving the problem]

Means are provided for illuminating the scene with light pulses for a very short fixed time period by triggering the electronic flash and for integrating this reflected light from the object. The final integral of the reflected light is a measure of the reflectivity of the subject. There is also provided a means for obtaining a certain field characteristic from the final integrated value, which is used for controlling the photographic exposure later. Illuminating the scene in this way for a fixed period of time with a light pulse from an electronic flash using energy from a single main discharge capacitor will ignite the flash immediately on later exposure with energy from the same main discharge capacitor. To do so, more energy can be used.

〔Example〕

FIG. 1 shows an automatic development type single lens flex type (SLR) photographic camera 10 using an embodiment of a pre-exposure reflectance measuring type exposure control apparatus of the present invention. Camera 10
It has a fixed focus objective or photographic lens 12, which, for example, directs imaged rays from the subject 14 through a shutter blade mechanism or aperture formed in the structure 18 to the film surface.
One or more elements (only one is shown) for focusing on 16 may be included.

Next, in FIG. 2A and FIG. 2B, the blade mechanism 18 disposed between the lens 12 and the film surface 16
A pair of overlapping shaped shutter blade elements 20A and 20B
including. The primary apertures 22A and 22B of the field light are provided in the blade elements 20A and 20B, respectively, so that the simultaneous displacement of one blade element with respect to the other blade element in the vertical and horizontal directions causes them to cooperate. To define an effective aperture that makes a gradual and predictable change. In addition, since the movement of this blade element is described more fully in U.S. Pat.
The reference is replaced with the description. The aperture of the blade element is selectively formed so as to overlap the central optical axis of the lens 12,
This defines an aperture of varying size as a function of the position of the blades of the blade mechanism 18. Shutter drive
24 includes an electromagnetic traction device in the form of a solenoid (not shown) used to displace the shutter blade elements from one another as detailed in the aforementioned Whiteside patent.

Each blade element 20A and 20B of the blade mechanism 18 has a secondary opening 26A, 28A and 26B, 28B, respectively. Feather 20
The opening 26A of A forms a hole 30 penetrating the shutter assembly 18 in cooperation with the opening 26B of the blade 20B, and the opening 28A of the blade 20A cooperates with the opening 28B of the blade 20B to form a similar hole 32. Form. These cooperating secondary apertures may be configured to track the field light incident primary apertures 22A and 22B with a predetermined correspondence thereto. Since the primary and secondary openings are formed in the same blade element and are mechanically connected to each other, when the blade elements 20A and 20B are displaced from each other as described above, the secondary opening is Obviously, it can move as well. The amount of artificial light incident on the film surface 16 through the primary openings 22A and 22B is detected by an infrared light sensitive element in an infrared light sensor 36, which detects and integrates a corresponding amount of infrared field energy passing through the hole 30. It is controlled by a signal produced by the combination of 34 and integrator 38. The combination of the visible light-sensitive element 40 and the integrator 43 in the visible light sensor 42 is used to detect and integrate the corresponding amount of visible natural light that has passed through the hole 32 and to enter the film surface 16 through the primary aperture. Controlled by the signal produced by An example of a scanning vane element having primary and secondary apertures that cooperate to control the amount of field incident on the film surface is described in the aforementioned US Pat. No. 3,942,183.
No.

The camera 10 has a blade position sensor / encoder 44. Sensor / encoder 44 detects the position between blade elements 20A and 20B and generates a signal 46 indicative of the relative position of the blade elements. Sensor / encoder 44 includes a light emitting diode 48, a light sensor 50 spaced therefrom, and a plurality of slots or holes 52 and 54 formed in each of blade elements 20A and 20B. The slots 52, 54 form a rectangle of uniform size, and are arranged at regular intervals along a straight line in each of the blade elements 20A and 20B. The slots 52 and 54 are for the light emitting diode 48 and the optical sensor 50.
, Thereby alternately blocking and allowing the transmission of light between the two elements, and providing light sensor 50 with one or more pulses 46 indicative of the relative position of blade elements 20A and 20B. Generate. The position of blade element 20A relative to blade element 20B defines the size of the effective or photographic aperture formed by primary openings 22A and 22B in blade mechanism 18. Accordingly, the relative position of blade elements 20A and 20B represented by pulse or pulse group 46 also
It measures the size of the effective or photographic aperture formed by the secondary apertures 22A and 22B. The width of the slots 52, 54 of the respective blade elements 20A and 20B in the direction of movement of the blade elements is minimized, whereby the actual dimensions of the effective aperture formed by the primary openings 22A and 22B and this Blade position errors with respect to the relative blade position pulse signal 46, which is indicative of a particular aperture, are minimized.

The camera 10 also includes an electronic flash device 56 and a device that determines the reflectivity of the subject and controls its activation to provide a portion of the exposure value required to illuminate the scene. The electronic flash device 56 is a DC-DC voltage converter
A main storage capacitor 58 is charged to the operating voltage by any conventional voltage conversion circuit (not shown) contained within 60. The DC-DC voltage converter 60 operates normally and operates on the order of 6 volts obtained from the battery 62 of the camera 10.
The DC voltage is converted to a suitable operating voltage, for example, 280 volts. The flash tube 64 and the thyristor connected in series are connected in parallel to the main storage capacitor 58 as a whole. The flash tube 64 is energized by a suitable trigger signal on a path 68 from a normal trigger circuit (not shown) in the exposure control electronics module 70, and the thyristor 66 is also activated in the exposure control electronics module 70. Is opened by an appropriate trigger signal on path 71 from another normal trigger circuit (not shown) included in the circuit. When activated, the flash tube 64 illuminates the scene and the objects contained therein with both visible and infrared light.

The camera 10 further includes a look-up table 72 obtained empirically. The primary purpose of look-up table 72 is as a function of natural field light and object reflectivity.
The purpose is to control the amount of image field light that is focused on the film surface 16 by the lens 12 through the effective or photographic aperture of the blade mechanism formed by the secondary apertures 22A and 22B.

As described above, the amount of artificial and natural field light sent to the film surface 16 is determined by the part of the artificial and natural field light passing through the holes 30 and 32 of the blade mechanism 18 and the infrared light sensor 36. It is measured indirectly by detection by a light sensor 34 and its associated integrator 38 within, and a light sensor 40 and its associated integrator 43 within the visible light sensor 42. The signal produced by the infrared light sensor 36 and its associated integrator 38 represents the amount of reflected infrared field light, is sent via a path 74 to a look-up table 72, and The associated signal produced by the integrator 43 represents the amount of natural field light and is sent to the look-up table 72 via path 76.

Look-up table 72 is responsive to these two signals to produce a plurality of different signals for controlling the amount of imaged light rays transmitted to film surface 16 through the primary aperture of blade mechanism 18. These different signals are obtained before the exposure time for each exposure cycle. Alternatively, these signals may be obtained early in the exposure time.

The signals obtained from the lookup table 72 include 1)
Primary openings 22A and 22B when flash tube 64 is ignited
Output path that controls the size of the photographic aperture formed by the
An aperture size signal on 78; 2) an artificial light percentage signal on an output path 80 that controls the amount of artificial light to be added from the flash tube 64 to the scene; and 3) the primary aperture 22A and The natural light percentage signal on output path 82, which controls the amount of image light incident on film surface 16 through 22B; 4) if the exposure time did not end earlier, input paths 74 and There is a signal on output path 84 for terminating the exposure time at the time due to artificial and natural light signals appearing on each of 76.

As described above, the camera 10 includes an electronic flash device 56, the light output of which is used to determine the reflectivity of the subject and to provide some of the exposure values required to illuminate the scene. . The light output of the electronic flash device 56 is used during the exposure cycle to determine subject reflectivity before the exposure time.

The reflectance of the subject in the scene is determined as follows. 3A, 3B, and 3C, when an exposure cycle is initiated, a normal trigger circuit (not shown) in the exposure control electronics module 70 causes a trigger signal 86 (third signal) on path 68 to appear. FIG. A) is supplied to energize or start the firing of the flash tube 64. After an inherent delay of about 5 microseconds, flash tube 64 begins illuminating the field with visible and infrared light as shown in FIG. 3B. After a delay of about 2 microseconds from the trigger of the flash tube 64, the integrator 38 connected to the output of the infrared light sensor 36 is enabled by an enable signal on the path 87 from the exposure control electronics module 70. . This 2 microsecond delay is caused by the flash tube
The triggering of 64 and the detection of natural infrared light that already illuminated the field before the field was illuminated by the light from the flash tube 64 eliminates the possibility of integration error noise that could be generated. Minimize. FIG. 3C is a graph of the integration of the output current from infrared light sensor 36 by integrator 38 as a function of time.

35 microseconds after the exposure control electronics module 70 triggers the flash tube 64 for field illumination, another trigger circuit (not shown) in the exposure control electronics module 70 is routed 71. Trigger signal 88 on (3A
(FIG. 3) to trigger the thyristor 66 to open, thereby starting to extinguish the light output to the flash tube 64. At the same time as the thyristor 66 is triggered to start extinguishing the light output of the flash tube 64, the exposure control electronic module 70
Disables integrator 88 via path 87 and
The integration of the output current of is terminated. Note that, as shown in FIG. 3B, the flash tube 64 continues to illuminate the scene with light for a significant amount of time even if it is triggered to de-energize or turn off at a particular time. Should.

In some applications, disabling integrator 38 simultaneously with the onset of extinction of the light output from flash tube 64 introduces an unacceptably large thyristor emission noise integration error into the exposure controller. . If this were to occur, the integrator 38 could be disabled for a few tenths of microseconds of triggering the thyristor 66 to avoid such errors. In other exposure control applications, disabling the integrator 38 at or before the start of the flash tube's light output may produce an integral signal of insufficient magnitude for proper operation of the exposure controller. Close. In such cases, the integrator
By disabling 38 after the thyristor 66 has been triggered off or open, the amount of integrated light is increased.
However, when the integrator 38 integrates all the noise generated by turning the thyristor 66 off or open, if integration errors that would normally occur cannot be tolerated,
To compensate for the integration error, additional circuitry must be added. Regardless of when the integrator 38 is disabled, the final level of the integration forms a signal representative of the object reflectivity.

Before the aforementioned look-up table 72 generates output signals on paths 78, 80, 82, 84, it is created by visible light sensor 42, integrated by integrator 43, and passed to path look-up table 72 via path 76. The applied natural visible light signal is
It is sent to the microcontroller 90 via 92 and is temporarily stored. After this natural visible light signal is stored in the microcontroller 90 and before the start of the exposure time, in response to the flash light of the pre-exposure period from the flash tube 64 including the infrared light component reflected from the subject. The infrared light signal generated by the infrared light sensor 36 and the integrator 38 is sent to a look-up table 72 via a path 74. Next, the natural visible light signal already stored in the microcontroller 90 is
The data is sent to the lookup table 72 via 94. The stored natural visible light signal and the infrared light signal that is later generated by the infrared light sensor 36 and integrated by the integrator 38 are used together in the look-up table 72, so that the look-up table 72 is used. The aforementioned signals appearing on the output paths 78, 80, 82, 84 are produced.

Each signal appearing on output paths 78, 80, 82, 84 of look-up table 72 in response to infrared and natural visible field light signals produced by sensors 36 and 42 and respective integrators 38 and 43, Determined empirically. Look-up tables 72 are used to generate the output signals of these look-up tables, a number of photographs having a range of reflectivities at various subject distances and occurring under a wide range of artificial and natural field light conditions. It is constructed according to the substantive analysis of the image.

In general, when forming a photographic image on the film surface 16 of the camera 10, the smaller the shooting aperture formed by the primary openings 22A and 22B, the deeper the depth of field of the fixed focus lens 12, and the larger the shooting aperture. Because the size is reduced, the image field light quantity is reduced, and the image resulting from the natural field light is darkened. Look-up table 72 is configured to provide a compromise between sharpness of the subject image in the scene and exposure to the entire scene. In making this compromise, the look-up table 72 fires the flash tube 64 at the smallest possible aperture, thus providing the maximum depth of field that provides optimal subject image sharpness and overall field exposure. To achieve. Look-up table 72 further includes sensor 36 and
In response to the infrared and visible light level signals generated by 42, control the artificial light emitted by flash tube 64 during the exposure time, and also control the maximum size of the photographic aperture formed by primary apertures 22A and 22B. Doing so improves the overall field exposure.

As mentioned above, since the camera 10 is of the SLR type,
It includes a conventional reflector 96 operated via a path 98 by the exposure control electronics module 70. The mirror 96 prevents the field light from being transmitted to the film surface 16 and allows the camera operator to observe the field to be photographed through the lens 12, and the mirror 96 covers the film surface 16 during the exposure time. The first to make the scene light incident
It operates normally between the illustrated or unblocked position shown.

Camera 10 is preferably designed to use a self-developing film unit (not shown) similar to that disclosed in Rand U.S. Pat. No. 3,415,644, which is commonly owned with the present application. I have. This self-developing film unit is a light-shielding film cassette 100 shown immediately after it is completely inserted into the camera 10.
Housed within. Cassette 100 may include a 6 VDC battery 62.

Provided within the camera 10 is a film advancement device 102 similar to that described in Land's U.S. Pat.No. 3,753,392, which is coupled to the film advancement device 102 to remove the exposed film unit. It includes a motor (not shown) that operates a gear train that continuously moves from the exposure position inside the camera 10 to the outside of the camera. Film advancer 102 further includes a film engaging arm member (not shown) driven by the motor and gear train described above. This arm member is inserted into the slot of the cassette 100, engages with or near the rear edge of the uppermost film unit disposed inside, and then moves the film unit out of the cassette 100,
It feeds into the engagement of a pair of conventional processing rollers (not shown) mounted adjacent the leading edge of the top film unit. The processing roller is rotated by the above-described motor and gear train, so that the movement of the exposed film unit out of the camera 10 is continued without interruption, and at the same time, the processing liquid container at the front end of the exposed film unit is torn. . The processing roller spreads the contents of the torn container between the elements of the film unit and initiates the formation of a visible image within the film unit, as is known in the art.

Next, a typical exposure cycle will be described in detail. For purposes of this description, that the imaging aperture of the blade mechanism 18 is in the fully open position, that the holes 30 and 32 formed by the secondary apertures of the blade mechanism 18 are also fully open,
With the mirror 96 in the viewing or light blocking position, the flash device 56 has already made the switch closed coupling the battery 62 to the DC-DC voltage converter 60 via the exposure control electronics module 70 and the path 105. Is being energized by
Assume that main storage capacitor 58 is fully charged and ready to begin an exposure cycle. FIG.
FIG. 4 is a graph showing the change in primary and secondary blade aperture size during a typical exposure cycle as a function of time. Fig. 1, Fig. 2A, Fig. 2B, Fig. 3A, Fig. 3B, 3C
4 and 4, when the camera operator operates the switch 106 to the closed position, an exposure cycle is started. When switch 106 is closed, battery 62 couples to exposure control electronics module 70 via path 108. Secondary openings 28A and 28B
When the aperture 32 of the wing mechanism formed by the wing mechanism assumes a fully open position adjacent to the visible light sensor 42, the exposure control electronic module 70 and the microcontroller 90 coupled thereto via the path 110 are visible. Optical sensor 42 and visible light sensor 42
Is activated via path 112. When activated, the integrator 43 is activated to integrate the natural field light over a fixed period of time and the final integral is
Via 76 to look-up table 72, then route 92
Is sent to the microcontroller 90 and temporarily stored.

After the natural field light information is stored in the microcontroller 90, the exposure control electronics module 70 activates the shutter drive to activate the blade mechanism 18, thereby causing the photographic aperture and the secondary apertures 26A and 26B. Hole formed by 30
And the hole 32 formed by the secondary openings 28A and 28B are moved to a completely closed position. Hole 30 of shutter mechanism 18
After closing the shutter and before the start of the exposure time, the shutter driver 24 increases the size of the hole 30 toward the fully open position. While the hole 30 is being moved toward the fully open position, the exposure control electronics module 70 exposes the mirror 96 from the viewing or light blocking position, which blocks the imaging light from reaching the film surface 16. Film surface 16 of light rays mapped during time
To reach Means (not shown) for moving to a non-light blocking position (shown in FIG. 1)
Is actuated via path 98. When the hole 30 assumes the fully open position adjacent to the infrared light sensor 36, the exposure control electronics module 70 triggers the flash tube 64 via the path 68, thereby clearing the scene before the start of the exposure time. Illuminate with visible and infrared light. Next, the exposure control electronic module 70
35 microseconds after turning on the flash tube 64,
The thyristor 66 is opened or turned off via the line 71, and the light output of the flash tube 64 starts to disappear. This triggering on and off of the flash tube 64 forms the first light pulse sent towards the scene.

The exposure control electronics module 70 also triggers the infrared light sensor 36 and its associated integrator 38 via path 87 for 33 microseconds, i.e., the strobe 64 is on or the field illumination condition. Run for 2 microseconds less than the time set. Next, the exposure control electronic module 70
Sends the final integration value of the integrator 38, which measures the reflectivity of the subject, to the lookup table 72 via a path 74. When the look-up table 72 receives the subject reflectance signal, it combines it with the natural visible light signal previously stored in the microphone controller 90. Next, these combined signals are later output to look-up table output paths 78,80,
82, 84 are used to generate an aperture size flash firing signal, an artificial light percentage signal, a natural light percentage signal, and an exposure end signal, which are applied to the exposure control electronics module 70. You. Exposure control electronics module 70, upon receiving these signals generated by the look-up table, activates shutter drive 24 and blade mechanism 18 associated therewith to activate the secondary aperture.
The hole 30 formed by 26A and 26B is placed in the completely closed position, and the exposure time is started by operating the shutter driving device 24 and the blade mechanism 18. Exposure control electronic module 70
Includes four conventional comparators (not shown),
These comparators determine when the four conditions used to generate the exposure time, represented by the look-up table output signals on paths 78, 80, 82 and 84, have been realized. As used herein, the term exposure time is defined as the time during which the image light rays collected by the lens 12 pass through the shutter mechanism 18 to the film surface 16.

The first of the above comparators is a reference on the look-up table output path 78, the desired aperture size flash firing signal and the blade signal position represented by the pulse 46 from the blade position sensor / encoder 44, and thus the blade signal position. Compare with the size of the shooting aperture. When the first comparator determines that these two signals are equal, the exposure control electronics module 70
Again triggers the flash tube 64 via path 68, thereby illuminating the scene being photographed by visible and infrared light during the exposure time.

The second of the comparators described above is a reference on the output path 80 of the look-up table, i.e. the artificial light desired percentage signal, and the path integrated by the integrator 38 detected by the infrared light sensor 36 and associated therewith. The actual level of the artificial illumination of the field illumination sent to the exposure control electronic module 70 via 114 is compared. When the second comparator determines that the two signals are equal, the exposure control electronics module
70 triggers the thyristor 66 to the open state via the path 71, thereby extinguishing the artificial light generated from the flash tube 64. This illumination of the field by artificial light constitutes a second light pulse directed towards the field.

The third of the aforementioned comparators is a reference on the output path 82 of the look-up table, i.e., the visible light desired percentage signal, after being detected by the visible light sensor 42 and integrated by the associated integrator 43. The actual level of the field illumination visible light amount sent to the exposure control electronic module 70 via the path 112 is compared. The third comparator calculates these two
Upon determining that the two signals are equal, the exposure control electronics module 70 activates the shutter driver 24 to close the photographic aperture of the blade mechanism 18 and thereby end the exposure time.

Under certain field illumination and subject reflectivity conditions, a signal from the infrared light sensor 36 and / or the visible light sensor 42 such that the exposure control electronics module 70 can terminate the exposure time within a reasonable amount of time. There may be insufficient natural and / or artificial field light reflected from the field, which is insufficient to cause The fourth comparator is
A signal representing the actual level of natural or reflected field light on output path 84 of the look-up table is compared with a predetermined reference signal stored in exposure control electronics module 70. If the signal on path 84 is equal to or greater than the reference signal, the exposure time is limited to a relatively short time, for example, 40 milliseconds, but if this signal is less than the reference signal. Exposure time may be relatively long, e.g., 400 times, unless terminated earlier with sufficient exposure levels of natural and / or artificial field light.
Limited to milliseconds.

When the exposure time is completed, the exposure control electronic module 70
Is operated by moving the mirror 96 toward the light blocking position and by operating the film advancement device 102 and the drive motor (not shown) included therein via the path 116 to thereby expose the exposed automatic The transport and processing of the developing type film unit are started. The film advancer feeds the exposed film unit in cassette 100 via path 118 into the engagement of a pair of adjacent processing rollers (not shown) as described above, and between the film layers, the processing liquid. And also expose this exposed film unit to
It is fed into a discharge slot (not shown) in the housing 120 of the self-developing camera 10. Mirror 96, film surface 16
After being actuated to the light blocking position, which blocks the passage of light to the exposure control electronics module 70, the shutter drive 24
And the shutter mechanism 18 coupled thereto is actuated to place its primary or photographic aperture in the fully open position.
When the film advancer 102 has moved the exposed film unit through the aforementioned roller pair, a film movement complete signal is sent via path 122 to the exposure control electronics module 70 and the microcomputer 90 coupled thereto.
Upon receiving the film movement completion signal, the exposure control electronic module 70 starts charging the electronic flash device 56 via the path 105. The path 105 indicates that the main storage or discharge capacitor 58 of the electronic flash device 56 is fully charged.
, The exposure control electronics module 70 sets the exposure control device of the camera 10 ready to start the next exposure cycle.

In the above-described exposure control device, the artificial light source constituted by the flash tube 64 was used to illuminate the scene with both infrared light and visible light. Flash tube 64
Is two times during one exposure cycle, ie one before the exposure time.
The field was illuminated once and during the exposure time. All energy required by flash tube 64 to illuminate the scene both before and during the exposure time is:
Here, the power is supplied from a single storage capacitor described as the main discharge capacitor 58. Main discharge capacitor 58 before exposure
The length of time during which energy is supplied to the flash tube 64 is limited to a predetermined length. In the example, the length of this time was limited to 35 microseconds. Limiting the length of time energy is supplied to the flash tube 64 before the exposure time, and thus the amount of energy, reduces the distance range over which the reflectivity of the subject can be determined. However, by limiting the length of time that energy is supplied to the flash tube 64 for reflectance determination before the exposure time, the main discharge capacitor 58
Can store enough energy to power the flash tube 64 both before and during the exposure time due to the charge on the single capacitor.

From the above description of the invention, those skilled in the art will recognize that various modifications may be made to the embodiments described above without departing from the scope of the invention. The embodiments described herein are illustrative only and should not be construed as the only implementation that encompasses all of the present invention.

〔The invention's effect〕

In accordance with the present invention, a simplified, low energy consumption means for measuring the reflectivity of a field illuminated by an electronic flash prior to exposure is incorporated, and certain field characteristics used for subsequent exposure control are provided. An automatic exposure control for an electronic flash camera configured to determine is provided.

[Brief description of the drawings]

FIG. 1 is a schematic view of a photographic camera incorporating an embodiment of a pre-exposure reflectance measurement exposure control apparatus of the present invention, and FIG. 2A is a scanning shutter blade also schematically shown in FIG. Exploded perspective view of the mechanism, FIG. 2B is a plan view including a partial cross section of the shutter blade mechanism of FIG. 2A, and FIG. 3A is the time of the activation and deactivation signals of the electronic flash before the exposure time in the exposure cycle FIG. 3B shows a graph as a function, FIG. 3B shows a graph of the light output of the electronic flash of the invention as a function of time before the exposure time in the exposure cycle, and FIG. 3C shows the graph before the exposure time in the exposure cycle. FIG. 4 is a graph showing the time integration of the output current of the infrared light sensor used in the exposure control device of the present invention, and FIG. 4 shows the change in the size of the primary and secondary blade openings in the exposure cycle. 4 is a graph shown as a function of time. Explanation of reference numeral 10: electronic flash camera, 12: photographing lens, 14:
... Subject, 16 ... Film surface, 18 ... Shutter blade mechanism, 34 ... Infrared light sensitive element, 36 ... Infrared light sensor, 38 ...
... Integrator, 40 ... Visible light sensitive element, 42 ... Visible light sensor, 43 ... Integrator, 58 ... Main discharge capacitor, 64 ... Flash tube, 70 ... Exposure control electronic module.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Jeffrey Tea. Gray 221 Massachusetts Avenue, Boston, Mass., United States (56) References JP-A-4-90519 (JP, A) JP-A-56-142408 (JP, A) JP-A-62-90633 (JP, A) JP-A-61-156239 (JP, A) JP-A-4-159526 (JP, A) JP-A-2-253124 (JP, A) JP-A-1-304435 (JP, A) JP-A-58-63927 (JP JP-A-59-123826 (JP, A) JP-A-58-108443 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03B 7/16

Claims (12)

(57) [Claims] An apparatus for measuring the reflectivity of an object in an object scene, comprising: a light source illuminating the object scene that can be energized for a fixed period of time; Detecting light reflected from the light source, and generating a signal in response to the reflected light; coupled to the photosensitive means, after a specific delay time has elapsed after the light source is activated, the light source is to illuminate the field Integrating means for integrating the reflected light response signal for a predetermined time until the end of the fixed time being energized to illuminate, and providing a final integrated value which is a measurement signal of subject reflectance; and Means for generating the subject reflectivity signal by energizing the light source to illuminate the scene. 2. Apparatus according to claim 1, wherein said specific delay time is equal to 2 microseconds. 3. An apparatus for measuring the reflectivity of a subject in an object scene, comprising: a light source capable of being energized for a fixed time for illuminating the object scene; Detecting light reflected from the light source, and generating a signal in response to the reflected light; coupled to the photosensitive means, after a specific delay time has elapsed after the light source is activated, the light source is to illuminate the field Integrating means for integrating the reflected light response signal for a predetermined time before the end of the fixed time being energized to illuminate, and providing a final integrated value serving as a measurement signal of subject reflectance; and Means for generating the subject reflectivity signal by energizing the light source to illuminate the scene. 4. An apparatus for measuring the reflectivity of a subject in a scene, comprising: a light source illuminating the scene that can be energized for a fixed time; Detecting light reflected from the light source, and generating a signal in response to the reflected light; coupled to the photosensitive means, after a specific delay time has elapsed after the light source is activated, the light source is to illuminate the field Integrating means for integrating the reflected light response signal for a predetermined time until after the end of the fixed time being energized to illuminate, and providing a final integrated value serving as a measurement signal of subject reflectance; and Means for generating the subject reflectivity signal by energizing the light source to illuminate the scene. 5. An apparatus for measuring the reflectivity of a subject within a scene, comprising: a light source illuminating the scene that can be energized for a fixed time; A photosensitive means for detecting light reflected from the light source and generating a signal in response to the reflected light; and integrating the reflected light response signal for a time equal to the fixed time, the subject being coupled to the photosensitive means. Integrating means for providing a final integral value serving as a reflectance measurement signal; and means for generating the subject reflectance signal by energizing the light source to illuminate the object scene. apparatus. 6. An apparatus for measuring the reflectivity of a subject in a scene, comprising: a light source illuminating the scene that can be energized for a time of approximately 35 microseconds; and a light source emitted from the light source. A photosensitive means for detecting light reflected from the subject and generating a signal in response to the reflected light; and coupled to the photosensitive means, integrating the reflected light response signal for a predetermined time length to obtain an object reflectance. And a means for generating the subject reflectance signal by energizing the light source to illuminate the object scene. 7. An electronic flash camera, comprising: a film surface; and a lens structure for transmitting an image light beam on a photosensitive material disposed in the film surface along a fixed optical path from an object scene. A vane mechanism, wherein the vane mechanism is in a light blocking relationship with respect to the optical path to prevent the scene light from being sent to the film surface along the optical path; and A non-blocking arrangement that is non-blocking with respect to the optical path is mounted for movement of the field light through the exposure aperture to the film surface, the blocking arrangement and the non-blocking arrangement. Said vane mechanism forming an exposure opening that changes size in a predetermined operation when moved between the blocking arrangement and the exposure time to generate an exposure time; a fixed time before the exposure time and a variable time during the exposure time Energized and over A light source for illuminating the object scene with artificial light; detecting light emitted from the light source before and during the exposure time and reflected from the object scene, and generating first and second signals representing the light, respectively. Integrating means coupled to the photosensitive means for integrating the first signal over a fixed time length and generating a third signal representative thereof; and before and during the exposure time Means for detecting ambient field light and generating fourth and fifth signals respectively representing them, and control means for illuminating the field for said fixed time before the exposure time Energizing the light source and operating the light source to illuminate the scene for a period during the exposure time in response to the third signal, the second signal, and the fourth signal. , The fifth signal and the third signal Control means for activating said blade mechanism to generate an exposure time correspondingly. 8. The light source includes a single main discharge capacitor for storing a charge for energizing the light source, the capacitor illuminating the scene both before and during a photographic exposure time. The electronic flash camera according to claim 7, wherein energy for performing the operation is supplied to the light source. 9. A method for measuring the reflectance of a subject in a scene, comprising: activating a light source for illuminating the subject in the scene for a fixed length of time; Detecting light emitted and reflected from the subject, generating a signal in response to the reflected light, and illuminating the scene with the light source after a lapse of a specific delay time after activation of the light source. Integrating the reflected light response signal for a predetermined period of time up to the end of the fixed time being energized to provide a final integrated value that is a measure of object reflectance. 10. The method of claim 9, wherein the step of integrating the reflected light response signal integrates the reflected light response signal two microseconds after activating the light source. 11. A method for measuring the reflectivity of a subject in a scene, comprising the steps of: energizing a light source for illuminating the subject in the scene for a fixed length of time; Detecting light emitted and reflected from the subject, generating a signal in response to the reflected light, and illuminating the scene with the light source after a lapse of a specific delay time after activation of the light source. Integrating the reflected light response signal for a predetermined time period prior to the end of the fixed time being energized to provide a final integrated value that is a measure of object reflectance. 12. A method for measuring the reflectivity of a subject in a scene, comprising: activating a light source for illuminating the subject in the scene for a fixed time length; Detecting light emitted and reflected from the subject, generating a signal in response to the reflected light, and illuminating the scene with the light source after a lapse of a specific delay time after activation of the light source. Integrating said reflected light response signal for a predetermined period of time up to the end of said fixed time being energized to provide a final integrated value that is a measure of object reflectance.