JP3957850B2 - Image input device having light amount adjusting device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light amount adjusting device that adjusts the light amount of a photographing light beam and an image input device such as a camera having the light amount adjusting device.
[0002]
[Prior art]
For example, a light amount adjustment device mounted on a video camera is designed to change the aperture opening diameter by smoothly reciprocating the light amount adjustment member in order to perform automatic exposure control in response to shooting conditions and brightness that change from moment to moment. As a reciprocating drive device for reciprocatingly driving the light amount adjusting member, there are proposed a method of driving only by an electromagnetic action and a method of using a spring action in combination with the electromagnetic action shown in FIG.
[0003]
The reciprocating drive device of the light quantity adjusting device shown in FIG. 4 has a base plate 36 having a diaphragm opening 35 and a Magnet rotor 31 in which an output shaft is rotatably supported on each bearing portion of a cap 37 and a gap on the outer periphery. A yoke 32 fixed to the outer base plate 36, a drive coil 33 and a brake coil 34 disposed between the magnet rotor 31 and the yoke 32 constitute a drive unit, and a drive lever 38 is provided on the output shaft of the magnet rotor 31. Is fixed. A pair of light amount adjusting members 39, 40 are provided between the base plate 36 and the case 41 having the aperture opening 41a, and the pair of light amount adjusting members 39, 40 are not shown provided on the base plate 36. The movement direction is guided by guide holes 39c, 39d, 40c, and 40d that engage with the guide pins. Engagement holes 39a and 40a formed at the ends are engaged with engagement pins 38a and 38b at both ends of the drive lever 38 to transmit the rotational force from the drive unit. The return spring 42 is incorporated so as to bias the drive lever 38 in the closing direction. The ND filter 43 is fixed to the light amount adjusting member 39 and attenuates the amount of light passing through or covering part or the whole of the opening formed by the light amount adjusting members 39 and 40.
[0004]
With such a configuration, by energizing the drive coil 33, the magnet rotor 31 and the drive lever 38 rotate against the return spring 42, and a pair of light quantity adjustments are performed so that the light flux passing through the aperture opening 35 increases. The members 39 and 40 are moved. On the other hand, when the energization amount to the drive coil 33 is decreased, the magnet rotor 31 and the drive lever 38 are rotated by the biasing force of the return spring 42 so that the light flux passing through the aperture opening 35 is decreased. Move 39,40.
[0005]
Japanese Patent Laid-Open No. 2-114246 proposes a method using a stepping motor as a drive source of the light amount adjusting device.
[0006]
[Problems to be solved by the invention]
By using a stepping motor as a drive source of the light amount adjusting device as in the invention described in Japanese Patent Laid-Open No. 2-114246,
1. Suitable for digital control.
2. Easy to stop and hold.
3. There are few malfunctions such as oscillation, and control is simple and open-loop control is possible.
While having the following effects, it has the following drawbacks.
1. It can be stopped only at the step position, resulting in a stepwise rough light amount adjustment.
2. Looking at the continuous images during the step operation, the amount of light appears to change.
3. If a mechanical shutter is used for adjusting the shutter speed, high-speed continuous images and fine adjustment are difficult.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, an image input device of the present invention includes a light amount adjusting device that adjusts the light amount of a light beam by moving a light amount adjusting member using a stepping motor as a drive source, and the light amount adjusting device has a desired aperture. and diaphragm control means for providing a driving pulse to the stepping motor so as to obtain a value, and an imaging device for imaging the light beam modulated by the light amount adjusting device, and the electronic shutter control means for controlling the charge accumulation time of the image sensor, wherein outputs the target aperture value information to the aperture control means, such amount of light caused by the change of the aperture value associated with the output becomes gentle, the change in the opposite direction of the imaging light amount of changes in the imaging light amount by the light amount adjusting device Exposure control means for outputting a corresponding shutter speed to the electronic shutter control means.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIGS.
[0013]
FIG. 1 is a block diagram showing the main part of a camera using the present invention, FIG. 2 is a flowchart for explaining the light amount adjustment operation of the camera shown in FIG. 1, and FIG. 3 is a diagram of a light amount adjustment device provided in the camera of this embodiment. It is a disassembled perspective view.
[0014]
In FIG. 3, 1 is a stepping motor which is a drive source fixed to the base plate 11 by a cover 8, 2 is a gear which press-fits into the output shaft of the stepping motor 1, and transmits the driving force of the stepping motor 1 to the gear 3. A gear 4 that is fixed to the feed screw 4 and transmits the driving force of the gear 2 to the feed screw 4 is rotatably supported by a cover 8 and a bearing 9 and is fixed to the gear 3 so as to rotate integrally with the rack gear 10. It is a feed screw that transmits. Therefore, when the stepping motor 1 rotates, the rack gear 10 reciprocates.
[0015]
Reference numeral 6 denotes a pressing spring that presses one end of the feed screw 4 against the bearing 9 and presses the thrust backlash. The pressing spring 6 is fixed to the cover 8 by a screw 5. 7 is a photo interrupter that detects whether or not the rack gear 10 is in a predetermined position, and whether or not the rack gear 10 is in a predetermined position by detecting whether or not the light shielding portion 10a of the rack gear 10 is positioned in the detection gap 7a. Is detected. A cover 8 supports the stepping motor 1, the feed screw 4, the photo interrupter 7, and the like and is fixed to the base plate 11, and a bearing 9 that rotatably supports one end of the feed screw 4 is fixed to the cover 8.
[0016]
10 is a rack gear that reciprocates along the guide hole 11a of the base plate 11 as a drive source of the stepping motor 1, and is a pin 10b that is inserted through the guide hole 11a and engages with the elongated holes 12b and 13b of the light quantity adjusting members 12 and 13. And the above-mentioned light shielding part 10a is formed. Therefore, when the rack gear 10 reciprocates in the guide hole 11a, the light amount adjusting members 12 and 13 move in opposite directions to adjust the light amount of the photographing light flux that passes through the opening 11f.
[0017]
When the light shielding portion 10a of the rack gear 10 is positioned in the detection gap 7a of the photo interrupter 7, the light amount adjusting members 12 and 13 completely close the opening portion 11f.
[0018]
Reference numeral 11 denotes a base plate that supports the light amount adjusting members 12 and 13 and to which the cover 8 is fixed. An opening 11f and a guide hole 11a are formed. Reference numerals 12 and 13 denote light amount adjusting members that adjust the light amount of the photographic light beam that passes through the opening 11f of the base plate 11 by moving, and are formed with long holes 12a and 13a with which the pins 10b of the rack gear 10 are engaged. Reference numeral 14 denotes an opening 14f, which is a pressing plate that is locked to the base plate 11 and presses the light amount adjusting members 12 and 13, and 15 is an optical axis of the imaging light flux.
[0019]
Next, the configuration of the camera provided with the light amount adjusting device as shown in FIG. 3 will be described.
[0020]
FIG. 1 is a block diagram of an embodiment of the present invention.
[0021]
In FIG. 1, 15 represents an optical axis of a photographing light beam, and 21 represents an imaging lens for forming an image of the imaging light beam on the image sensor 22. Reference numeral 22 denotes an image pickup device that picks up the image pickup light beam adjusted by the light amount adjusting members 12 and 13, reference numeral 23 denotes an exposure control circuit that controls exposure so that the light amount of the image pickup light beam incident on the image pickup device 22 is appropriate, and reference numeral 24 denotes image pickup. This is an electronic shutter control circuit that adjusts the shutter speed by controlling the charge accumulation time of the element 22.
[0022]
Reference numeral 25 denotes an aperture control circuit that gives drive pulses to the stepping motor 1, and 27 denotes an aperture detection circuit that forms aperture value information by adding and subtracting drive pulses supplied to the stepping motor 1 and outputs the aperture value information to the exposure control circuit 23. An image processing circuit 28 processes the output of the image sensor 22 into image information.
[0023]
In the above configuration, the imaging light passing through the imaging lens 21 is adjusted by the light amount adjusting members 12 and 13 and forms an image on the imaging element 22.
[0024]
The image sensor 22 measures the amount of incident imaging light, and outputs the result to the exposure control circuit 23 as imaging light quantity information. The aperture detection circuit 27 detects the current aperture value and outputs the result to the exposure control circuit 23 as aperture value information.
[0025]
The exposure control circuit 23 sets a target aperture value from the aperture value information and the imaging light amount information so that the imaging light amount becomes an appropriate light amount, and outputs the target aperture value to the aperture control circuit 25. Further, a shutter speed that compensates for the difference between the photographing light amount and the appropriate light amount at the target aperture value is obtained and output to the electronic shutter control circuit 24.
[0026]
Here, the exposure control circuit 23 detects the direction and amount of change of the aperture value from the aperture value information formed by the aperture detection circuit 27 so that the change in the amount of light accompanying the change in aperture value becomes gradual. The shutter speed corresponding to the change in the amount of light in the direction opposite to the direction of change of the aperture value and corresponding to ½ of the change amount is output to the electronic shutter control circuit 24 as the shutter speed correction value. The shutter speed correction value stops outputting to the electronic shutter control circuit 24 after a time ½ of the drive pulse period of the stepping motor 1 has elapsed.
[0027]
The electronic shutter control circuit 24 adjusts the shutter speed by varying the charge accumulation time of the image sensor 22 according to the shutter speed correction value so that the change in the amount of imaged light becomes gradual.
[0028]
Further, the aperture value range from the maximum aperture value to the minimum aperture value is detected from the aperture value information from the aperture detection circuit 27, and it is determined that an excessive or too small imaging light beam exceeding an appropriate aperture value range is incident on the image sensor 22. Then, the minimum aperture value or the maximum aperture value is output to the aperture control circuit 25, and a shutter speed that compensates for the difference between the light amount of the imaging light flux at the minimum aperture value or the maximum aperture value and the appropriate light amount is supplied to the electronic shutter control circuit 24. Output.
[0029]
The aperture control circuit 25 applies a drive pulse to the stepping motor 1 to drive the light quantity adjusting members 12 and 13 so as to obtain a target aperture value, and outputs this drive pulse to the aperture detection circuit 27 as well.
[0030]
The aperture detection circuit 27 detects the aperture value information by performing a reset operation and adding / subtracting the drive pulse applied to the stepping motor 1 when the light shielding portion 10a of the rack gear 10 is positioned in the detection gap 7a of the photo interrupter 7.
[0031]
After obtaining the target aperture value, the aperture control circuit 25 stops the stepping motor 1 and turns off the power to the stepping motor 1 to hold the target aperture value.
[0032]
After the stepping motor 1 is stopped, the electronic shutter control circuit 24 adjusts the shutter speed by changing the charge accumulation time of the image sensor 22, and controls the image sensor 22 so that the imaging light quantity becomes optimum.
[0033]
When the power is turned off, the stepping motor 1 is preferably stopped after moving the light amount adjusting members 12 and 13 until the light amount adjusting members 12 and 13 completely close the opening 11f of the base plate 11.
[0034]
In the present embodiment, the light amount adjusting members 12 and 13 perform the reset operation of the aperture detection circuit 27 in a state where the opening 11f of the base plate 11 is completely closed. It is the same if it arrange | positions so that the position which makes the part 11f fully open can be detected, and may exist in both a closed position and a full open position.
[0035]
In this embodiment, the shutter speed corresponding to a light amount change corresponding to 1/2 of the change amount of the aperture value is set as the shutter speed correction value, but the present invention is not limited to this. For example, the same effect can be obtained even with a shutter speed corresponding to a light amount change corresponding to 3/4 of the change amount of the aperture value.
[0036]
In addition, the time for giving the shutter speed correction value is not limited to 1/2 of the drive pulse period of the stepping motor 1, but the shutter speed correction is performed every 1/4 hour of the drive pulse period for driving the stepping motor 1. If the value is decreased by a factor of 1/4, the amount of light changes more smoothly.
[0037]
Furthermore, the cycle for changing the shutter speed correction value may be a cycle for the image processing circuit 28 to capture a continuous image.
[0038]
Next, the light quantity adjustment operation of the camera of this embodiment will be described.
[0039]
FIG. 2 is a flowchart for explaining the light amount adjustment operation of the camera according to the present embodiment. After measuring the imaging light amount from the image sensor 22 in step 41, the current aperture value is detected from the aperture detection circuit 27 in step. .
[0040]
Thereafter, in step 43, it is determined whether or not the current aperture value detected by the aperture detection circuit 27 is an appropriate aperture value with respect to the imaging light amount measured in step 41. If the current aperture value is an appropriate aperture value, the process branches to step 50;
[0041]
In step 44, a pulse is given to the stepping motor 1 so as to obtain an appropriate aperture value with respect to the imaged light quantity measured in step 41. In step 45, the current aperture value is detected from the aperture detection circuit 27.
[0042]
Step 46 is a step of determining whether or not there is a change in the aperture value. If there is a change in the aperture value, the process branches to step 47, and if there is no change, the process branches to step 48.
[0043]
Step 47 is a step of outputting the shutter speed correction value so that the change in the amount of light due to the change in the aperture value becomes gradual, and is in a direction opposite to the direction of change in the aperture value and 1 / of the amount of change. The shutter speed corresponding to the change in the amount of light corresponding to 2 is output as a shutter speed correction value to the electronic shutter control circuit 24, and after the time of half the cycle of the drive pulse of the stepping motor 1 has elapsed, the electronic shutter The output to the control circuit 24 is stopped.
[0044]
Step 48 is a step of determining whether or not an appropriate aperture value has been reached. If the aperture is appropriate, the process branches to step 49, and if not, returns to step 44.
[0045]
In step 49, the stepping motor is stopped and the energization is turned off.
[0046]
In step 50, it is determined whether or not the light amount of the photographing light flux at an appropriate aperture value is an appropriate light amount. That is, it is determined whether or not an appropriate amount of light can be obtained only by controlling the diaphragm. If it is determined that the light amount is appropriate, the process proceeds to step 41, and if not, the process branches to step 51.
[0047]
In step 51, the shutter speed is controlled so as to interpolate the difference between the light amount of the photographing light flux and the appropriate light amount at an appropriate aperture value.
[0048]
【The invention's effect】
According to the present invention, it is possible to moderate the light amount change by controlling the shutter speed so as to correspond to the change in the imaged light amount in the direction opposite to the change in the imaged light amount.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a main part of a camera using the present invention.
FIG. 2 is a flowchart for explaining a light amount adjustment operation of the camera shown in FIG. 1;
FIG. 3 is an exploded perspective view of a light amount adjusting device provided in the camera of the present embodiment.
FIG. 4 is a diagram illustrating a conventional light amount adjusting device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Stepping motor 12, 13 Light quantity adjustment member 22 Image pick-up element 23 Exposure control circuit 24 Electronic shutter control circuit 25 Aperture control circuit

Claims (3)

A light amount adjusting device that adjusts the light amount of the light beam by moving the light amount adjusting member using the stepping motor as a drive source;
A diaphragm control means for giving a drive pulse to the stepping motor so that the light quantity adjusting device obtains a desired diaphragm value;
An image sensor for imaging the light flux adjusted by the light amount adjusting device;
Electronic shutter control means for controlling the charge accumulation time of the image sensor;
The target aperture value information is output to the aperture control means, and the change in the imaging light amount in the direction opposite to the change in the imaging light amount by the light amount adjusting device is made so that the change in the light amount due to the change in the aperture value accompanying the output becomes gentle. And an exposure control means for outputting a shutter speed corresponding to the above to the electronic shutter control means.   2. The exposure control means according to claim 1, wherein the exposure control means sets a shutter speed corresponding to a change in the imaging light amount in a direction opposite to a change in the imaging light amount by the light amount adjustment device for a time that is ½ of the cycle of the drive pulse. An image input apparatus that outputs to a shutter control means.   3. The change in imaging light quantity according to claim 1 or 2, wherein the exposure control means is in a direction opposite to a change in imaging light quantity by the light quantity adjusting device and is ½ of a change amount of imaging light quantity by the light quantity adjusting device. An image input apparatus which outputs a shutter speed corresponding to the electronic shutter control means.

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