JP2797339B2 - Electronic camera - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The electronic camera of the present invention will be described according to the following items.

A. Industrial application fields B. Summary of the invention C. Prior art D. Problems to be solved by the invention E. Means to solve the problems F. Embodiment [FIGS. 1 to 4] a. Camera appearance [Fig.1, Fig.2] b. Circuit configuration [Fig.3] b-1. Imaging unit b-2. Recording unit b-3. Strobe light emission circuit b-4. Control unit c. Operation example [FIGS. 4 and 5] G. Effects of the Invention (A. Industrial Applications) The present invention relates to a novel electronic camera. More specifically, an object of the present invention is to provide a novel electronic camera capable of preventing the occurrence of a smear phenomenon peculiar to an electronic camera using a solid-state imaging device without taking complicated means.

(B. Summary of the Invention) An electronic camera according to the present invention includes a solid-state image sensor that functions as an image input element and a photometer disposed behind an aperture means, and an electronic shutter that controls the electric storage time of the solid-state image sensor and varies a shutter speed. Means and an exposure control means for controlling the exposure by controlling the aperture means and the electronic shutter means, wherein the exposure control means first fixes the aperture value of the aperture means and varies the electronic shutter speed. After performing the photometry, by controlling the exposure by changing the aperture value of the aperture means fixed to an electronic shutter speed defined based on the photometry result,
The present invention is intended to prevent the smear phenomenon inherent in shooting a high-luminance subject without complicating the drive system of the aperture mechanism.

(C. Prior Art) In general, in a camera using a magnetic disk, a magneto-optical disk, or the like as a recording medium, the imaging means is generally used as
In many cases, a solid-state image sensor such as a MOS or CCD area image sensor is used.

And, as the exposure control method in such a camera, the charge accumulation time of the solid-state imaging device was fixed to 1/60 seconds or 1/30 seconds in the initial stage,
Exposure control was performed by controlling the aperture. However, as the sensitivity of solid-state imaging devices has improved due to advances in semiconductor technology, the aperture diameter is small when shooting a high-luminance subject in such a method. Various inconveniences such as deterioration in image quality due to diffraction and hunting in aperture control have become noticeable.

Therefore, taking advantage of the development of a so-called electronic shutter system for arbitrarily controlling the charge accumulation time of the solid-state imaging device, when the brightness of the subject is higher than a certain value, the aperture diameter of the aperture is fixed to correspond to the brightness of the subject. A method of controlling exposure with an electronic shutter speed has been used.

(D. Problems to be Solved by the Invention) However, in the above-described exposure control using only the electronic shutter speed, when shooting a high-luminance object, smear development due to leakage of carriers into adjacent pixels in a solid-state imaging device or the like occurs. There is a problem that it is easy to occur.

Therefore, it is conceivable to use an aperture mechanism that can stop at an arbitrary F-number in order to enable continuous variation of the F-number with respect to the shutter speed, as in a camera using a normal film. The drive system of the mechanism becomes complicated, which is not preferable in terms of cost and the like.

(E. Means for Solving the Problems) In order to solve the above-described problems, the electronic camera of the present invention measures the light with a fixed aperture value and variable electronic shutter speed during photometry, and uses this measurement result when photographing. Based on this, the electronic shutter speed is fixed at a predetermined value, and the aperture value is varied to perform exposure control.

Therefore, according to the present invention, the aperture value is fixed at the time of photometry, and the electronic shutter speed is varied to adjust the exposure until the smear phenomenon is not noticeable, and then the shutter speed is fixed and the aperture value is controlled. Therefore, the smear phenomenon can be sufficiently suppressed as compared with the conventional exposure control using only an electronic shutter, and it is not necessary to be able to stop at an arbitrary aperture value, and the drive system of the iris is simplified. It is possible.

(F. Embodiment) [FIGS. 1 to 4] Hereinafter, details of the electronic camera of the present invention will be described with reference to the embodiment shown in the accompanying drawings.

(A. Appearance of electronic camera) [FIGS. 1 and 2] In FIG. 1, reference numeral 1 denotes an electronic camera, which converts image information captured by a photographing lens into an electric signal by an image pickup device and magnetically records the electric signal on a magnetic disk. It is like that.

Reference numeral 2 denotes an outer case of the electronic camera 1, and a photographing lens 3, a strobe light emitting unit 4, an objective lens 5 of a finder, and the like are arranged on a front portion of the outer case 2.

Reference numeral 6 denotes a light receiving element which forms a part of a photometry circuit described later,
It is arranged on the front surface of the outer casing 2 and is provided so as to stop strobe light emission when the strobe light amount becomes appropriate. As the light receiving element 6, for example, a phototransistor having good responsiveness is used.

Reference numeral 7 denotes a shutter button provided on the upper surface of the outer casing 2, and a switch opened and closed by pressing the shutter button 7 has a second switch structure. In other words, the first and second states that are sequentially turned on by pressing the button 7
When the first switch is closed, a power supply voltage is supplied to an image pickup unit, a recording unit, and the like, which will be described later, or a photometric operation is performed. When the button 7 is further pressed, the second switch is closed, and a required switch is closed. Image information can be recorded on a magnetic disk. The shutter button 7 is urged by a resilient means (not shown) to move in a direction to protrude from the outer casing.

Reference numeral 8 denotes a cassette insertion opening formed on the rear surface of the outer casing 2. A magnetic disk cassette 10 in which a magnetic disk 9 is rotatably housed is inserted from the cassette insertion opening 8 into the outer casing 2.
It is designed to be inserted inside.

Reference numeral 11 denotes a connector including a DC input terminal, which is provided on the rear surface of the outer casing 2. The connector 11 is connected to a connector plug provided in a playback device (not shown) so as to receive supply of a power supply voltage.

(B. Circuit Configuration) [FIG. 3] FIG. 3 shows an outline of a circuit configuration of the electronic camera 1. The main part of the circuit of the electronic camera 1 is an imaging device that receives and processes light from a subject. Unit 12, a recording unit 13 that processes a signal from the imaging unit and converts the signal into a signal recordable on the magnetic disk 9, a strobe light emitting circuit 14, and a control on these signal processing and a power supply control. And a control unit 15 that performs overall control.

(B-1. Imaging Unit) Reference numeral 16 denotes an imaging element disposed behind the imaging lens 3 described above. For example, a MOS-type or CCD-type area image sensor is used, and the imaging element 16 is an image input element. And a photometric sensor.

Reference numeral 17 denotes an electronic shutter control circuit that performs drive control including electronic shutter control of the image sensor 16, and is capable of controlling the charge accumulation time of the image sensor 16. For example, when a CCD type area image sensor is used as the image sensor 16, the charge accumulated in the light receiving element is changed by applying a charge sweeping pulse to an overflow drain gate to vary a substantial charge accumulation time. The electronic shutter speed can be controlled, for example, in a range of about 1/60 to 1/1000 second.

Reference numeral 18 denotes an iris, which is arranged between the photographing lens 3 and the image sensor 16.

Reference numeral 19 denotes an iris drive circuit, which opens the iris 18 immediately after the start of the photometric operation by a signal from the control unit 15, and determines the electronic shutter speed after the photometric operation mainly based on the electronic shutter speed, according to the subject brightness. So-called auto iris control for automatically adjusting the opening diameter of the iris 18 is performed.

Reference numeral 20 denotes a light amount detection circuit, the input terminal of which is
And receives a signal from the image sensor 16 and sends a signal corresponding to the amount of received light to the control unit 15. For example, in the case of average photometry, average detection of all images of the image sensor 16 is performed, and this is A / D converted and transmitted to the control unit 15.

(B-2. Recording Unit) Reference numeral 21 denotes a recording circuit, which performs necessary processing such as modulation of a signal transmitted from the imaging device 16 via the video processing circuit 22 to obtain a magnetically recordable recording signal. Is provided.

Reference numeral 23 denotes a magnetic head.
When the second switch 7b is closed by pressing the signal, a signal transmitted from the recording circuit 21 at a predetermined timing is recorded on the magnetic disk 9. In this case, the control unit 15 sends the control signal to the magnetic head 23 by the control signal.
Is performed via a tracking servo circuit 24 and a lead screw mechanism 25 including a stepping motor. Further, a rotation drive control of a spindle motor 26 for holding and rotating the magnetic disk 9 is performed by a servo circuit 27.
Is performed via

(B-3. Strobe Lighting Circuit) Reference numeral 28 denotes a charging circuit.
When it is necessary to take a picture with a predetermined ED, for example, EV9 or less, the main capacitor is charged by a signal from the control unit 15 so that strobe light emission can be performed. When the charging of the main capacitor is completed, the charging circuit 28 sends a signal notifying the end of the charging to the control unit 15.

Thereafter, when the second switch 7b is closed by pressing the shutter button 7, the sync contact 29
Is closed, whereby a trigger pulse by the trigger circuit 30 is applied to a discharge 31 such as a xenon lamp, etc.
Discharge lamp 31 by the electric charge stored in the main condenser
Is started.

Then, a signal corresponding to the reflected light from the subject is output from the light receiving element 6, which is integrated by the photometric circuit 32, digitized and sent to the control unit 15, and when the integrated amount reaches a predetermined value, the control is performed. The circuit between the main capacitor of the charging circuit 28 and the discharge lamp 31 is cut off by a signal sent from the unit 15 to the trigger circuit 30, and the discharge lamp 31 stops emitting light.

(B-4. Control Unit) Reference numeral 33 denotes a system controller that controls the entire system of the electronic camera 1. Regarding the photometric operation control of the electronic camera 1, the system controller 33 sends a control signal to the electronic shutter control circuit 17 to control the electronic shutter speed to a predetermined value or to make the above-described open aperture mode and auto iris mode appear. Then, a signal corresponding to each mode is sent to the iris drive circuit 19. And
The system controller 33 controls the charging operation of the charging circuit 28 by judging the necessity of the strobe light emission operation from the photometry information, and controls the stop timing of the strobe light emission based on a signal from the photometry circuit 32.

An operation unit 34 includes the shutter button 7 and other operation button switches. And the operation unit
When various signals from 43 are sent to the system controller 33, the imaging unit 12 and the recording unit are sent from the system controller 33.
Since a predetermined control signal including a synchronization signal and the like is sent to 13 and the like, the signal processing operation of each unit and power supply from a power supply unit (not shown) to each unit are controlled.

(C. Operation Example) [FIGS. 4 and 5] Next, photometry and exposure control in the electronic camera 1 will be described with reference to an operation flowchart shown in FIG. 4 and a program diagram shown in FIG.

The range indicated by the thick line segment in FIG. 5 indicates the auto iris control range for each electronic shutter speed (how to take the F value shown in FIG. 5 is opposite to the normal EV conversion diagram). Note that.) For example, when the electronic shutter speed is represented by T (second) and the F value is represented by F, in the range of EV = [9,11), T = 1/60 and F = [2.8,5.
6), EV = [11,12), T = 1/125, F = [4,5.
6), EV = [12,13), T = 1/250, F = [4,5.
6), EV = [13,17], T = 1/500, F = [4,1]
6]. (Note that x = [4, b) means a ≦ x <b, or x = [a, b] means a ≦ x ≦ b. A) "Start" First, when the shutter button 7 is half-pressed, the first switch 7a is turned on, and a signal at this time is input to the system controller 33. In response to this, the system controller 33 permits the supply of the power supply voltage to each unit and starts up the system.

b) “Open aperture” The system controller 33 sends a control signal to the iris drive circuit 19 to perform open metering, and
Open 18 fully.

c) "Measure photometry at T = 1/60 second" That is, the electronic shutter speed T is controlled to 1/60 second by a control signal from the system controller 33 to the electronic shutter control circuit 17. The light from the subject at this time is received by the image sensor 16, and the light amount detection circuit 20 digitizes a signal corresponding to the received light amount and sends it to the system controller 33.
In step (1), an EV that provides an appropriate exposure is determined from the information on the subject luminance and the sensitivity of the image sensor 16.

d) "Determination of brightness". That is, it is determined whether or not the EV obtained in step c) is a predetermined value, for example, EV9 or less. Then, the process proceeds to step e). If the value is EV9 or more, it is determined that the image is bright, and the process proceeds to step f).

e) "Charging for strobe light emission is performed." That is, when the potential of the main capacitor of the charging circuit 28 of the strobe light emission circuit 14 is equal to or lower than a predetermined value, this is judged by the system controller 33. The main capacitor is charged by a command from the system controller 33.

As described above, at the time of photographing, after the strobe light is emitted, the digitized integrated output value from the photometry circuit 32 is input to the system controller 33, and when this value exceeds a predetermined value, the trigger signal is sent from the system controller 33 to the trigger circuit.
The light emission stop timing of the discharge lamp 31 is controlled by a signal sent to 30, thereby controlling the exposure amount.

f) "Measure photometry at T = 1/1000 sec." The photometry operation is performed with the electronic shutter speed set to T = 1/1000 sec. by the electronic shutter control. Brightness is measured and EV is required.

g) “Determine brightness”. It is determined whether or not the EV obtained in the above step is a predetermined value, that is, EV13 or more. If it is EV13 or more, it is determined that it is bright, and the process proceeds to step h). It is determined to be dark, and the process proceeds to step i).

h) “Automatic iris control is performed with T = 1/500 second fixed.” The electronic shutter speed is fixed at 1/500 second by a control signal sent from the system controller 33 to the electronic shutter control circuit 17, and the system controller is controlled. By the auto iris mode signal and the control signal sent to the iris drive circuit 19 from the iris 33, the iris 18 which has been in the open state until then is within a predetermined range, that is, F = 4 to
In the range of 16, control is performed according to the light amount from the subject.

i) "Measure photometry at T = 1/500 sec." That is, if it is determined that the image is dark in step g), photometry is performed at an electronic shutter speed of 1500 sec.
EV is required.

j) “Determination of light and darkness.” The comparison between EV and EV12 in the above step i) is performed. If it is equal to or more than EV12, it is determined that the image is bright, and the process proceeds to step k). Proceed to l).

k) “Automatic iris control is performed with T = 1/250 sec.” When it is determined that the image is bright in step j), the electronic shutter speed is fixed at 1/250 sec. = 4 to 5.6.

l) "Measure photometry at T = 1/250 sec." Since it was determined to be dark in step k), the metering was performed with the electronic shutter speed set to 1/250 sec.
Ask for.

m) "Determine brightness". That is, it is determined whether or not the EV obtained in step l) is equal to or greater than EV11. If it is equal to or greater than EV11, it is determined that the vehicle is bright, and the process proceeds to step n). And proceed to step o).

n) "Automatic iris control is performed by fixing T to 1/125 sec." When it is determined that the image is bright in step m), the electronic shutter speed is fixed to 1/125 sec and the iris 18 is set to F = 4 to Control within 5.6.

o) "Auto iris control is performed with T = 1/60 second fixed." That is, when it is determined in step m) that the image is dark, the auto iris is fixed with the electronic shutter speed fixed at T = 1/60 second. Transition to mode.

In the photometric operation described above, the brightness of the subject is constant,
For example, if EV = 12.5 (see point P in FIG. 5) as a result of the photometry in step c), it is clearly EV9 or more, no strobe is required, and step g) is dark ( EV = 12.5 ≦ 13), and photometry is performed at T = 1/500 second. Then, in step j), it is bright (EV = 12.5)
> 12), the process proceeds to step k), and T = 1/250, F
= 4.8 (see point P 'in FIG. 5).

Further, it is possible to follow a slight change in the subject brightness in the auto iris control range.

(G. Effects of the Invention) As is apparent from the above description, the electronic camera of the present invention includes a stop means, a solid-state imaging device located behind the stop means and provided for image input and photometry, and a solid-state imaging device. Electronic shutter means for controlling the charge storage time of the element;
In an electronic camera comprising an exposure control means for controlling exposure by controlling an aperture value of the aperture means and an electronic shutter speed by the electronic shutter means, the exposure control means first fixes the aperture value of the aperture means and sets the electronic shutter speed. After performing variable photometry, the exposure is controlled by varying the aperture value of the aperture means while fixing the electronic shutter speed specified based on the photometric result.

Therefore, according to the present invention, the aperture value is fixed at the time of photometry, and the electronic shutter speed is varied to adjust the exposure until the smear phenomenon is not noticeable, and then the shutter speed is fixed and the aperture value is controlled. Therefore, the smear phenomenon can be sufficiently suppressed compared to the conventional exposure control using only an electronic shutter, and it is not necessary to be able to stop at an arbitrary aperture value, and the drive system of the iris is simplified. It is possible.

Further, in the above-described embodiment, in auto iris control, F
Because the value control has a certain range, even if the brightness of the subject changes slightly between metering and actual shooting, the auto iris can control the aperture value to respond to changes in exposure, making exposure control stable. Can be achieved.

In the operation example described above, open metering is used, but this is merely an example, and the technical scope of the present invention is not limited to this, and aperture metering may be used.
Also, various modes of program control are possible for the specific values of the F value and the shutter speed.

[Brief description of the drawings]

The drawings show an embodiment of the electronic camera of the present invention, and FIGS. 1 and 2 show the appearance of the electronic camera.
FIG. 2 is a perspective view of the electronic camera as viewed from the upper front, FIG. 2 is a perspective view of the electronic camera with the magnetic disk cassette removed, as viewed from the rear, FIG. 3 is a block diagram of essential parts, and FIG. 5 is a diagram for explaining an operation example, FIG. 4 is an operation flowchart, and FIG. 5 is a program diagram. DESCRIPTION OF SYMBOLS 1 ... Electronic camera, 15, 20 ... Exposure control means, 16 ... Solid-state image sensor, 17 ... Electronic shutter means, 18, 19 ... Aperture means

Claims (1)

(57) [Claims] A stop means, a solid-state image pickup device located behind the stop means for image input and photometry, an electronic shutter means for controlling a charge accumulation time of the solid-state image pickup element, and an aperture value of the stop means And an exposure control means for controlling exposure by controlling an electronic shutter speed by an electronic shutter means, wherein the exposure control means first fixes the aperture value of the aperture means and varies the electronic shutter speed to perform photometry. After doing,
An electronic camera characterized in that the exposure is controlled by varying the aperture value of aperture means while fixing the electronic shutter speed specified based on the photometric result.