JP3961656B2 - Light amount adjusting device and image input device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light amount adjusting device that adjusts the amount of light incident on an image sensor and an image input device such as a camera equipped with the same.
[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 means for reciprocatingly driving the light amount adjusting member, there are proposed a method in which only the electromagnetic action is driven and a method in which the spring action is used in combination with the electromagnetic action shown in FIG.
[0003]
The reciprocating drive means of the light quantity adjusting device shown in FIG. 4 has a ground slope 136 having a throttle opening 135, a Magnet rotor 131 whose output shaft is rotatably supported on each bearing portion of the cap 137, and a gap on the outer periphery. A drive unit is configured by the yoke 132 fixed to the outer base plate 136, the drive coil 133 and the brake coil 134 disposed between the magnet rotor 131 and the yoke 132, and is used as an output shaft of the magnet rotor 131. The drive lever 138 is fixed.
[0004]
A pair of light amount adjusting members 139 and 140 are provided between the base plate 136 and the case 141 having the aperture opening 141a. The pair of light amount adjusting members 139 and 140 are guides (not shown) provided on the base plate 136. The moving direction is guided by a guide hole engaged with the pin. Engagement holes 139a and 140a formed in the end groups are engaged with engagement pins 138a and 138b at both ends of the drive lever 138, respectively, to transmit the rotational force from the drive unit.
[0005]
The return spring 142 is incorporated to urge the drive lever 138 in the closing direction. The ND filter 143 is fixed to the light amount adjusting member 139 and increases or decreases the amount of light passing through a part or the whole of the opening formed by the light amount adjusting members 139 and 140.
[0006]
In such a configuration, when the drive coil 133 is energized, the magnet rotor 131 and the drive lever 138 rotate against the return spring 142 so that the light flux passing through the aperture opening 135 increases. The adjustment members 139 and 140 are moved. On the other hand, when the energization amount to the drive coil 133 is decreased, the remagnet rotor 131 and the drive lever 138 are rotated by the urging force of the return spring 142 so that the light flux passing through the aperture opening 135 is decreased. The light quantity adjusting members 139 and 140 are moved.
[0007]
Japanese Patent Laid-Open No. 2-114246 proposes a method using a stepping motor as a drive source of the light amount adjusting device. In the light quantity adjusting device proposed in this publication, the stepping motor is pulse-driven and stopped until the driving is completed for the number of steps (target number of steps) obtained by converting the difference (light quantity error) between the incident light quantity to the imaging means and the target light quantity. A series of operations are repeated.
[0008]
[Problems to be solved by the invention]
However, in the device proposed in the above publication, the target number of steps is not changed unless the above series of operations is completed, so even if the amount of incident light on the image sensor changes during this series of operations, Has the disadvantage of not being able to follow.
[0009]
In order to perform fine light amount adjustment, it is necessary to increase the resolution (number of steps) of the stepping motor. However, if the resolution is increased, the time required to complete the above series of operations increases. When the above series of operations is completed, there is a possibility that the target appropriate light amount has already fluctuated. In this case, the captured image does not become a picture. In particular, there is a concern about the practicality of an apparatus that captures high-speed continuous images.
[0010]
If the resolution of the stepping motor that can complete the above-described series of operations in a short time is limited, only coarse adjustment of the light amount can be performed.
[0011]
Accordingly, the present invention has an object to provide a light amount adjusting device capable of appropriately and finely adjusting the amount of light incident on the image pickup means corresponding to an imaging scene that changes every moment, and an image input device including the same. To do.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, in the present invention, a light amount adjusting member that is driven to adjust the amount of incident light to the imaging means, and a light amount according to the difference between the actual incident light amount and the target incident light amount to the imaging means. In a light amount adjusting apparatus having an information setting unit for setting driving information for an adjusting member and a driving unit for driving the light amount adjusting member based on the driving information, in order to cause the information setting unit to set driving information. A signal output unit that outputs a signal synchronized with the image capturing period of the imaging unit is provided, and the information setting unit includes a signal output unit regardless of whether or not the driving according to the driving information of the light amount adjusting member is completed. When receiving a signal, that is, when receiving a signal from the signal output means before the completion of driving according to the driving information of the light amount adjusting member, the driving information is newly set without waiting for the driving to be completed. It is.
[0014]
As a result, the light amount adjusting member is driven according to the newly set driving information without waiting until the driving is completed when the synchronization signal is output before the driving according to the driving information is completed. Therefore, it is possible to always adjust the amount of incident light to the imaging means appropriately and finely for an imaging scene that changes every moment.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
In FIG. 3, the light quantity adjusting device which is 1st Embodiment of this invention is shown in the decomposition | disassembly state. In this figure, reference numeral 1 denotes a stepping motor which is a drive source fixed to a base plate 11 by a cover 8.
[0016]
2, 3, 4, and 10 are members (hereinafter collectively referred to as a transmission member 29) for transmitting the driving force of the stepping motor 1 to the light amount adjusting members 12 and 13. Among these, 2 is a gear that is press-fitted into the output shaft of the stepping motor 1 and transmits the driving force of the stepping motor 1 to the gear 3. The gear 3 is fixed to the feed screw 4 and transmits the driving force of the gear 2 to the feed screw 4. The feed screw 4 is rotatably supported by a cover 8 and a bearing 9, is fixed to the gear 3 and rotates integrally, and transmits a driving force to the rack gear 10. Reference numeral 5 denotes a screw for fixing the holding spring 6 to the cover 8. The holding spring 6 presses one end of the feed screw 4 against the bearing 9 to suppress thrust backlash.
[0017]
A photo interrupter 7 has a detection gap 7a, and detects a position where the light shielding portion 10a of the rack gear 10 shields the detection gap 7a. The photo interrupter 7 constitutes an aperture value detection circuit 30 described later. The cover 8 supports the stepping motor 1, the transmission members 2, 3, 4, 10, the photo interrupter 7, and the like and is fixed to the base plate 11.
[0018]
The rack gear 10 is engaged with the guide hole 11 a of the ground slope 11 and the long holes 12 a and 13 a of the light amount adjusting members 12 and 13, and transmits the driving force of the feed screw 4 to the light amount adjusting members 12 and 13. Further, the rack gear 10 shields the detection gap 7 a of the photo interrupter 7 at the closed position of the light quantity adjusting members 12 and 13.
[0019]
The base plate 11 has an opening 11f and a guide hole 11a, and supports the light quantity adjusting members 12 and 13 movably and supports the members. The light quantity adjusting members 12 and 13 have openings 12f and 13f and elongated holes 12a and 13a, and move so as to change the light quantity passing through the openings 12f and 13f as the rack gear 10 moves.
[0020]
The holding plate 14 has an opening 14f and is locked to the base plate 11 to support the light amount adjusting members 12 and 13 so as to be movable. Reference numeral 15 denotes an optical axis of incident light.
[0021]
FIG. 1 is a block diagram of an image input apparatus provided with the light amount adjusting device of the present embodiment. Reference numeral 21 denotes an imaging lens that forms an incident light on the image sensor 22, and 22 denotes an image formed by the incident light whose light amount is determined by the light amount adjusting members 12 and 13, according to the image sensor control circuit 27, and outputs the light amount comparison circuit. 24 and an image sensor output to the image processing circuit 32.
[0022]
A light amount setting circuit 23 sets a target incident light amount that is an appropriate light amount of incident light to the image sensor 22 and outputs the target incident light amount to the light amount comparison circuit 24.
[0023]
The light quantity comparison circuit 24 compares and calculates the actual incident light quantity and the target incident light quantity based on the output of the image sensor 22 proportional to the actual incident light quantity, and sends a light quantity error signal Ey corresponding to the difference to the step number conversion circuit 25 . Output.
[0024]
Reference numeral 25 is synchronized with the output of the synchronizing circuit 31 and, based on the aperture value information of the aperture value detection circuit 30, the light quantity error signal Ey is obtained as step number information including the driving direction of the stepping motor 1 and the number of driving steps (driving in the claims). This is a step number conversion circuit that converts the information into a step number correction circuit 26.
[0025]
When the step number correction circuit 26 receives the step number information from the step number conversion circuit 25, the step number correction circuit 26 replaces this step number information with the previously received step number information to obtain new step number information. The drive pulse train information including the drive frequency, the drive direction, and the number of steps is converted and output to the aperture control circuit 28 and the aperture value detection circuit 30.
[0026]
The image sensor control circuit 27 drives and controls the image sensor 22 in synchronization with the output of the synchronization circuit 31. The aperture control circuit 28 controls the drive of the stepping motor 1 by converting the drive pulse train information of the step number correction circuit 26 into an excitation pulse for driving the stepping motor 1.
[0027]
As described above, the transmission member 29 is the gears 2, 3, the feed screw 4 and the rack gear 10 of FIG. 3 that transmit the driving force of the stepping motor 1 to the light amount adjustment members 12, 13.
[0028]
The aperture value detection circuit 30 adds and subtracts the drive pulse train information to form aperture value information and outputs it to the step number conversion circuit 25. The aperture value detection circuit 30 detects the position of the rack gear 10 as initial position information through the photo interrupter 7 when the light quantity adjustment members 12 and 13 are in the closed position, and initializes the aperture value information. Thus, the absolute position of the aperture value information is corrected to maintain accuracy.
[0029]
A synchronization circuit (signal output means in the claims) 31 sets and measures an image capture period and outputs a synchronization signal to the step number conversion circuit 25, the image sensor control circuit 27, and the image processing circuit 32.
[0030]
The image processing circuit 32 processes the output of the image sensor 22 into image information in synchronization with the output of the synchronization circuit 31.
[0031]
The light amount setting circuit 23, the light amount comparison circuit 24, the step number conversion circuit 25, and the step number correction circuit 26 in the present embodiment correspond to “information setting means” in the claims.
[0032]
FIG. 2 shows a control flowchart for optimally setting the amount of light incident on the image sensor 22 in the present embodiment. 41 is a step of setting a target light amount that is an optimal incident light amount, 42 is a step of measuring the incident light amount based on a signal from the image sensor 22, and 43 is calculating a light amount error signal Ey that is a difference between the incident light amount and the target light amount. Step 44 is a step for measuring aperture value information from the aperture value detection circuit 30, and 45 is a step for converting the light quantity error signal Ey into an appropriate number of steps for the stepping motor 1 based on the aperture value information.
[0033]
46 is a step of driving the stepping motor 1 with an appropriate driving direction and pulse rate, 47 is a step of measuring the number of steps driven by the stepping motor 1 from the driving pulse train, and 48 is an image capturing time (in the image sensor 22) This is a step of measuring a time required for accumulating charges necessary to form one screen.
[0034]
49 branches to step 53 when the image capture time has elapsed, and branches to step 50 when it has not elapsed. 50 branches to step 51 when the stepping motor 1 is driven by the appropriate number of steps. Step to shift to step 46 when not driven, step 51 to end the drive pulse train and stop the step operation of the stepping motor 1, and step 52 to branch to step 53 when the image capture time has passed. If not, the process proceeds to step 52, and 53 is a step to capture an image and proceed to step. In the light amount adjusting device configured in the image input apparatus as described above, the light amount setting circuit 23 sets the target light amount that is the optimum incident light amount (step 41 ), and repeats the following loop for capturing a continuous image. .
[0035]
First, the amount of incident light that passes through the imaging lens 21 is determined by the aperture opening formed by the light amount adjusting members 12 and 13, and forms an image on the imaging element 22. An output proportional to the incident light amount of the image sensor 22 is output to the light amount comparison circuit 24, and the light amount comparison circuit 24 compares and calculates the difference from the target light amount set in step 41 to convert the light amount error signal Ey into the step number conversion circuit 25. (Step 43).
[0036]
Next, the aperture value detection circuit 30 detects the aperture value and outputs aperture value information to the step number conversion circuit 25 (step 44). Next, the step number conversion circuit 25 converts the light amount error signal Ey into positive / negative step number information including the driving direction of the stepping motor 1 and the number of steps based on the aperture value information, and outputs it to the step number correction circuit 26.
[0037]
The step number correction circuit 26 converts the step number information into a drive pulse train including the drive frequency, drive direction, and step number of the stepping motor 1 and outputs it to the aperture control circuit 28 and the aperture value detection circuit 30 (step 45). ).
[0038]
Then, the aperture control circuit 28 converts the drive pulse train into an excitation pulse for driving the stepping motor 1, and drives and controls the stepping motor 1 (step 46).
[0039]
When the stepping motor 1 is driven, the light quantity adjusting members 12 and 13 are driven via the transmission member 29, and the aperture opening formed by the openings 12f and 13f is changed, so that the openings 11f and 11f of the base plate 11 and the holding plate 14 are changed. The amount of incident light passing through 14f is adjusted. At this time, the number of driven steps of the stepping motor 1 is measured (step 47).
[0040]
Further, the image capturing time is measured in the synchronizing circuit 31 (step 48), and when the synchronizing signal is not yet output from the synchronizing circuit 31 (step 49), the number of driven steps of the stepping motor 1 is set in step 45. It is determined whether or not the drive step number in the step number information has been reached (step 50).
[0041]
When the number of driven steps reaches the number of driving steps set in step 45, the driving of the stepping motor 1 is stopped. Subsequently, it is determined again whether or not the image capture time has elapsed (step 52). When the image capture time has elapsed, the next image capture is started (step 53).
[0042]
On the other hand, when the synchronization signal is output in step 49 (that is, the number of driven steps of the stepping motor 1 does not reach the number of driving steps set in step 45, but the synchronization signal is output), The next image capture is started as it is (step 53). Thereby, Step 42 to Step 45 are executed again, new step number information is set in the step number correction circuit 26, and the stepping motor 1 is driven according to the new step number information (Step 46).
[0043]
Then, Step 47 to Step 49 are executed. In Step 49, the number of driven steps of the stepping motor 1 is synchronized even though the number of driving steps (step number information) newly set in Step 45 has not been reached. When the signal is output, the next image capture is further performed (step 53).
[0044]
As described above, in this embodiment, the step number conversion circuit 25 sets new step number information corresponding to the latest aperture value information and the latest light amount error signal Ey for each image capture period. Then, the step number correcting circuit 26 discards the previous drive pulse train and generates a new drive pulse train based on the new step number information. Therefore, even for an imaging scene that changes every moment, it is possible to always set an appropriate and fine amount of incident light to the image sensor 22, and to obtain a continuous image having an optimum light amount for an image input device including the image sensor 22. An image can be taken.
[0045]
In the present embodiment, the light amount adjusting device using the stepping motor as the driving source has been described. However, the present invention can also be applied to a light amount adjusting device having a driving source other than the stepping motor.
[0046]
【The invention's effect】
As described above, according to the present invention, the drive information can be newly set according to the input of the signal synchronized with the image capture cycle before the completion of the drive according to the drive information of the light amount adjusting member. It is possible to always adjust the amount of incident light to the imaging unit appropriately and finely for an imaging scene that changes every moment, and the imaging unit can capture a continuous image with an appropriate amount of light.
[Brief description of the drawings]
FIG. 1 is a block diagram of a light amount adjusting device and an image input device according to a first embodiment of the present invention.
FIG. 2 is a system flowchart of the light amount adjusting device.
FIG. 3 is an exploded perspective view of the light amount adjusting device.
FIG. 4 is an exploded perspective view of a conventional light amount adjusting device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Stepping motor 12, 13 Light quantity adjustment member 23 Light quantity setting circuit 25 Step number conversion circuit 30 Aperture value detection circuit 29 Transmission member 22 Image sensor 24 Light quantity comparison circuit 26 Step number correction circuit 28 Aperture control circuit

Claims (6)

An information setting for setting information for driving the light amount adjusting member according to the difference between the actual incident light amount and the target incident light amount to the imaging means, and a light amount adjusting member driven to adjust the incident light amount to the imaging means A light amount adjusting device comprising: means and driving means for driving the light amount adjusting member based on the driving information;
A signal output means for outputting a signal synchronized with an image capturing period of the imaging means in order to cause the information setting means to set the drive information;
When the information setting means receives a signal from the signal output means before completion of driving according to the driving information of the light amount adjusting member, the information setting means newly sets driving information without waiting for the completion of driving. A light quantity adjusting device characterized by that. An information setting for setting information for driving the light amount adjusting member according to the difference between the actual incident light amount and the target incident light amount to the imaging means, and a light amount adjusting member driven to adjust the incident light amount to the imaging means A light amount adjusting device comprising: means and driving means for driving the light amount adjusting member based on the driving information;
A signal output means for outputting a signal synchronized with an image capturing period of the imaging means in order to cause the information setting means to set the drive information;
The information setting means newly sets driving information when receiving a signal from the signal output means, regardless of whether driving according to the driving information of the light amount adjusting member is completed. A light quantity adjusting device characterized.   When the information setting unit newly sets driving information without waiting for the completion of driving, the light amount adjusting member according to the newly set driving information in the driving unit without waiting for the driving completion. The light amount adjusting device according to claim 1, wherein the light amount adjusting device is driven. The driving information, the light quantity adjusting device according to any one of claims 1 to 3, characterized in that it comprises a target drive amount of the drive before the position of the light amount adjustment member. The drive means uses a stepping motor as a drive source,
The light amount adjusting device according to claim 4 , wherein the target drive amount is the number of drive steps of the stepping motor. An image input device comprising the light amount adjusting device according to any one of claims 1 to 5 .

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