JP5645497B2 - Imaging apparatus and control method thereof - Google Patents

Description

  The present invention relates to an imaging device including an ND filter and a control method thereof.

  A solid-state imaging device used for recording a moving image or a still image with a video camera or a digital camera as an imaging device has been reduced in size with the progress of semiconductor microfabrication. For this reason, an optical system for projecting a subject image on a solid-state image sensor has been miniaturized, and lenses of 1/5 inch and 1/6 inch optical sizes are used.

  In addition, with such a miniaturized video camera, the aperture becomes very small when the subject is extremely bright. May be damaged. In order to prevent this, in some video cameras, the photographer inserts an ND filter (achromatic color reduction filter) between the lens and the diaphragm as necessary so that the diaphragm diameter does not become smaller than a certain degree. It has been proposed (see, for example, Patent Document 1). This patent document 1 discloses that the aperture mechanism and the electronic shutter are controlled in accordance with the ND filter insertion state in order to eliminate the change in brightness of the photographed image before and after the ND filter insertion.

  In addition, in a conventional imaging device, it has been proposed to change the density of the ND filter stepwise to avoid luminance unevenness due to insertion of the ND filter (see, for example, Patent Document 2).

JP 2003-283923 A JP 2000-214514 A

  However, the technique related to the video camera disclosed in Patent Document 1 described above is for eliminating the fluctuation of the average level of the luminance change caused by the ND filter. For this reason, since such a video camera does not consider correcting luminance unevenness in the same screen, luminance unevenness may occur depending on the position of the ND filter that is inserted or removed.

  In addition, in the video camera disclosed in Patent Document 2, it is possible to reduce luminance unevenness when the ND filter is turned on or off, but a member that changes the density of the ND filter stepwise is essential. The mechanical structure becomes complicated, the production cost increases, and the product becomes expensive.

  An object of the present invention is to reduce luminance unevenness in the same screen that occurs in accordance with the insertion position of the ND filter with a simple configuration.

In order to achieve the above object, an image pickup apparatus according to the present invention is capable of entering and retracting a sequential readout type image pickup device that photoelectrically converts an incident light beam and an optical path of the light beam incident on the image pickup device. An image pickup apparatus having a filter for reducing the amount of light of the light beam, the position detecting means for detecting information relating to the position of the filter and information relating to the moving direction during the insertion operation or retraction operation of the filter, and in the optical path Storage means for storing a plurality of correction data corresponding to information relating to the position of the filter and information relating to the moving direction, and of the plurality of correction data stored in the storage means, the filter detected by the position detection means. based on the correction data corresponding to the information on the information and the moving direction related to the position, Shedin the signal output from the imaging device And having a correction means for correcting.

  According to the present invention, it is possible to reduce luminance unevenness in the same screen that occurs in accordance with the insertion position of the ND filter with a simple configuration.

It is a block diagram which shows schematic structure of the control system of the imaging device concerning 1st Embodiment of this invention. It is explanatory drawing explaining operation | movement of the ND filter in the imaging device concerning 1st Embodiment of this invention. It is explanatory drawing which shows the level of the imaging signal in each state in ND filter injection | throwing-in operation | movement in the imaging device concerning 1st Embodiment of this invention. It is explanatory drawing which shows the level of the image pick-up signal in each state in ND filter evacuation operation | movement in the image pick-up device concerning 1st Embodiment of this invention. It is explanatory drawing which shows the correction table for correct | amending the shading which generate | occur | produced with the ND filter in the imaging device concerning 1st Embodiment of this invention by the method of adding the inverse waveform of a shading waveform. It is explanatory drawing which shows the correction table for correct | amending the shading which generate | occur | produced with the ND filter in the imaging device concerning 1st Embodiment of this invention by the method of correct | amending by changing a gain. It is a flowchart which shows the operation | movement procedure of the microcomputer at the time of correct | amending the shading which generate | occur | produced with the ND filter in the imaging device concerning 1st Embodiment of this invention. It is a block diagram which shows schematic structure of the control system of the imaging device concerning the imaging device concerning 2nd Embodiment of this invention. It is explanatory drawing explaining the injection | throwing-in operation | movement of ND filter in the imaging device concerning 2nd Embodiment of this invention. It is explanatory drawing which shows the brightness | luminance shading in each state during ND filter injection | throwing-in operation | movement in the imaging device concerning 2nd Embodiment of this invention. It is explanatory drawing explaining the evacuation operation | movement of ND filter in the imaging device concerning 2nd Embodiment of this invention. It is explanatory drawing which shows the brightness | luminance shading in each state in ND filter evacuation operation | movement in the imaging device concerning 2nd Embodiment of this invention.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a diagram showing a schematic configuration of a control system of an image pickup apparatus according to the present embodiment, in which 1 is a photographing lens, 2 is a diaphragm blade, 3 is an image sensor, 4 is an analog front end circuit (hereinafter referred to as AFE), 6 is a signal processing circuit, and 18 is a microcomputer. The aperture blade 2 constitutes an aperture mechanism that limits the amount of incident light.

  Further, the image sensor 3 is driven by a TG 8 controlled by the microcomputer 18. 7 is an output circuit, 9 is an IG meter, 10 is a Hall element, 11 is an iris encoder, 12 is an iris drive circuit, and 13 is an ND filter that operates in conjunction with the diaphragm blade 2. The ND filter 13 is a filter that reduces the light amount of a light beam incident on the image sensor 3 and is provided so as to be able to enter and retract with respect to the optical path of the light beam incident on the image sensor 3.

  In the imaging apparatus configured as described above, a subject image formed through the photographing lens 1 is photoelectrically converted by the imaging element 3 and converted into an electrical signal. This signal is transmitted to the AFE 4 including the CDS / AGC circuit controlled by the microcomputer 18, correlated double sampling, and amplified to an appropriate level. Further, the output signal of the AFE 4 is output to the signal processing circuit 6 and converted into a digital signal, digitally processed and converted into a standardized video signal such as NTSC, etc., converted into an analog signal by the output circuit 7 and output. .

  On the other hand, the rotation position of the IG frame 9 driving the diaphragm blade 2 and the ND filter 13 operating in conjunction with the diaphragm blade 2 is detected by the Hall element 10. The detection result is amplified to an appropriate level by the iris encoder 11 and then output to the microcomputer 18. The microcomputer 18 A / D converts the received detection result and takes it as data. That is, the microcomputer 18 detects the state of the moving position when the end of the ND filter 13 crosses the optical path by the position detecting means of the filter end constituted by the IG mailer 9, the Hall element 10 and the iris encoder 11. To do.

  The microcomputer 18 reads information on the video signal level from the signal processing circuit 6. At the same time, the microcomputer 18 reads information on the open / close state of the aperture blade 2 from the iris encoder 11. The microcomputer 18 generates a control signal so that the video signal level becomes an appropriate level, and outputs the control signal to the iris drive circuit 12.

  The iris drive circuit 12 drives the IG meter 9 according to the received control signal, and the aperture blade 2, the IG meter 9, the hall element 10, so that the brightness of the subject image formed on the image sensor 3 becomes appropriate. And a mechanism composed of the ND filter 13 is operated.

  Next, the operation when the ND filter 13 is turned on will be described with reference to FIGS. 1, 2, 3 and 4. FIG.

  FIG. 2 is a diagram showing the positional relationship between the diaphragm blades 2 and the ND filter 13. (n1) is a state in which the ND filter 13 is slightly inserted in the optical path, and (n2) is a state in which the ND filter 13 is substantially in the center of the optical path. It represents the state that has been inserted. Further, (n3) represents a state in which the ND filter 13 is put in most of the optical path.

  FIG. 3 is a diagram showing the level of the imaging signal in the states (n1), (n2), and (n3) of FIG. 2 described above. In FIG. 3, the luminance signal levels on the de line of the substantially central portion of the screen A corresponding to the output signal are indicated by (n1A), (n2A), and (n3A).

  In (n1A), the luminance level in the vicinity of e is lowered, and in (n2A), the luminance level is shifted to the center of the screen, and the luminance level on the e side is lowered from the center. In (n3A), the brightness level is shifted to the d side of the screen, and the brightness level is lowered except in the vicinity of d. Each brightness level shading corresponds to the optical position of the ND filter 13.

  In this imaging apparatus, position information of the ND filter 13 when the ND filter 13 is inserted is output from the iris encoder 11 via the Hall element 10 and sent to the microcomputer 18. Based on the position information of the ND filter 13 obtained in this way, the microcomputer 18 selects (n1B) correction data shown in FIG. 4 in the case of (n1). In the case of (n2), correction data (n2B) is selected, and in the case of (n3), correction data (n3B) is selected.

  Then, the microcomputer 18 extracts a correction waveform based on the correction data at each position from the correction table block 20 and transmits it to the correction circuit 21. In the correction circuit 21, the received correction waveform is added to the imaging signal and transmitted to the output circuit 7. That is, the microcomputer 18 extracts correction data corresponding to the state of the movement position of the filter end detected from the iris encoder 11 or the like as the position detection means. Further, the microcomputer 18 transmits the extracted correction data to the correction circuit 21 to execute a correction operation.

  As a result, the output circuit 7 outputs an output image in which luminance unevenness within the same screen (hereinafter also referred to as shading or luminance shading) is reduced.

  Further, when the diaphragm blade 2 and the ND filter 13 are retracted, an operation opposite to that described above is performed. For example, as described above, the order of (n1), (n2), and (n3) in the case of charging is the order of (n3), (n2), and (n1) in the case of saving. Even when the ND filter 13 is withdrawn, the correction data and the correction table itself are the same as when the ND filter 13 is turned on.

  Next, the correction table will be described with reference to FIGS.

  A correction method for correcting the shading generated in the ND filter 13 includes a method of adding an inverse waveform of the shading waveform and a method of changing the gain in the screen in accordance with the shading portion.

  First, a method of adding the inverse waveform of the shading waveform will be described with reference to FIG. In FIG. 5 showing one screen divided for each sampling pixel of the imaging signal, the numerical value described in each pixel indicates the signal level.

  The correction table block 20 stores a correction table in which the numerical value of the signal level changes for each input position of the ND filter 13. The microcomputer 18 corrects the shading generated by the ND filter 13 by adding the reverse correction signal by the correction circuit 21 according to the correction table.

  Next, a correction method for correcting the shading generated in the ND filter 13 by changing the gain will be described with reference to FIG.

  In FIG. 6 showing one screen divided for each sampling pixel of the imaging signal, the numerical value described in each pixel indicates a gain.

  In this case, the correction table block 20 is provided with a correction table in which the value of the gain changes for each input position of the ND filter 13. The microcomputer 18 corrects the shading generated by the ND filter 13 by correcting the gain of the reverse correction signal by the correction circuit 21 in accordance with the correction table.

  Note that the values in the correction table shown in FIGS. 5 and 6 are values exemplified for explanation, and the actual values in the correction table are not limited to the exemplified values.

  Next, the operation of the microcomputer when correcting the shading generated by the ND filter 13 will be described with reference to the flowchart of FIG.

  When the shooting operation is started, the luminance level of the subject is detected (step S1).

  Next, the microcomputer 18 compares the detected luminance level with the target value, and when it is determined that the luminance level is the same as the target value (YES in step S2), the microcomputer 18 proceeds to step S8. If the microcomputer 18 determines that the luminance level is different from the target value (NO in step S2), the microcomputer 18 proceeds to step S3.

  Next, the microcomputer 18 compares the brightness level with the target value, and if it is determined that the brightness level is greater than the target value (YES in step S3), the microcomputer 18 proceeds to step S4 to close the iris by a predetermined amount. Repeat until the target value is reached. If the microcomputer 18 determines that the luminance level is smaller than the target value (NO in step S3), the microcomputer 18 proceeds to step S5.

  Next, the microcomputer 18 compares the luminance level with the target value, and when it is determined that the luminance level is smaller than the target value (YES in step S5), the microcomputer 18 proceeds to step S6 and performs an operation for opening the iris by a predetermined amount. Repeat until the target value is exceeded. If the microcomputer 18 determines that the luminance level is equal to or higher than the target value (NO in step S5), the microcomputer 18 proceeds to step S7.

  Next, the microcomputer 18 determines whether or not the luminance level matches the target value. If the microcomputer 18 determines that the luminance level does not match the target value (NO in step S7), the microcomputer 18 returns to step S3, and from step S3 to step S7. Repeat the routine up to.

  If the microcomputer 18 determines that the brightness level matches the target value (YES in step S7), the microcomputer 18 proceeds to step S8 and corresponds to the iris opening when the brightness level matches the target value. Is read (step S8).

  Next, the microcomputer 18 reads correction data corresponding to the read iris encoder value from the correction table block 20. Then, the microcomputer 18 transfers the read correction data to the correction circuit 21 and ends the shading correction processing.

  As described above, the correction process is performed using the correction data corresponding to the input state of the ND filter 13 (how much the ND filter 13 is input in the optical path), so that the ND filter can be input with a simple configuration. It is possible to reduce luminance unevenness in the same screen that occurs according to the position.

(Second Embodiment)
Next, an imaging apparatus according to the second embodiment of the present invention will be described with reference to FIGS. 8, 9, 10, 11, and 12. FIG. In the description of the present embodiment, the same reference numerals are given to the members equivalent to those described in the first embodiment, and the detailed description thereof is omitted.

  In the imaging apparatus according to the present embodiment, the ND filter 13 is driven by a driving unit having a configuration different from the configuration driven by the diaphragm blades, and the imaging device 3 is an element that performs sequential readout driving such as a CMOS. It consists of That is, in the image pickup apparatus according to the present embodiment, an aperture mechanism that limits the amount of incident light and an ND filter that can be turned on or retracted are independently arranged on the optical path of the image pickup optical system. The image sensor 3 is configured as a sequential readout type image sensor that photoelectrically converts an incident subject image into a video signal.

  In FIG. 8 showing a schematic configuration of a control system of the imaging apparatus according to the present embodiment, the imaging element 3 is constituted by a CMOS element. In FIG. 8, 14 is an IG meter for ND driving, 15 is a hall element for ND encoder, 16 is an ND encoder, and 17 is a driving circuit for the ND filter 13. The position detection unit configured by the IG meter 14, the Hall element 15, the ND encoder 16, and the like detects the position and moving direction when the end of the ND filter 13 crosses the optical path.

  In this imaging apparatus, it is assumed that the positional relationship when the ND filter 13 is turned on changes as shown in FIG. In order to facilitate understanding, the case where the aperture of the aperture blade is constant will be described.

  As shown in FIG. 9, the position of the ND filter 13 is closed via (n4), (n5), and (n6), respectively. The closing operation at this time operates independently of the aperture blade 2, and here, it is assumed that the entire retreating state with respect to the optical path is shifted from the fully retracted state to about the full closing state in about 1/60 seconds.

  (N4) shown in FIG. 9 shows the positional relationship before and after the state (t = 4) in which the ND filter 13 enters the throwing operation from the outside of the optical path and enters about 1/4. In this state, the ND filter 13 moves by the arrow Δn4 shown in the figure during Δt.

  Next, (n5) shows the positional relationship before and after the state (t = 5) in which the ND filter 13 enters almost the center of the optical path. In this state, the ND filter 13 moves by an arrow Δn5 shown in the figure during Δt.

  Next, (n6) shows the positional relationship before and after the state in which the ND filter 13 is in almost the entire optical path (t = 6). In this state, the ND filter 13 moves by the arrow Δn6 shown in the figure during Δt.

  First, in the case of (n4), while the ND filter 13 moves during Δt, the CMOS sensor that is the image sensor 3 is sequentially read out, so that luminance shading occurs obliquely. The correction data is a pattern of (h4) in FIG.

  In the case of (n5) and (n6), the luminance shading is similarly inclined, so that the correction data has the patterns (h5) and (h6).

  The microcomputer 18 collates each correction data with the correction table and generates a correction signal. Since this correction signal is added to the original signal by the correction circuit 21, an imaging signal without luminance shading is output from the output circuit 7.

  In short, in the present invention, when shooting a moving image with an imaging device such as a video camera, luminance unevenness occurs during the operation of setting the ND filter 13 to the use state or retracting to the standby position to stop using the ND filter 13. Alleviate that.

  For this reason, in the imaging apparatus according to the present embodiment, the shading correction value corresponds to the amount that the ND filter 13 covers the aperture for passing the light confined by the diaphragm blades 2 arranged in the photographing optical system. Note the differences.

  Then, the end of the ND filter 13 corresponds to a plurality of predetermined positions when passing through the aperture of the diaphragm blade 2 (when traversing the optical path) and whether the ND filter 13 is in the retracted state or the retracted state. In advance, a shading correction value is obtained. The obtained shading correction value is stored in the correction table block 20 corresponding to the position of the ND filter 13 and the condition of whether it is in the input or withdrawn state.

  The microcomputer 18 of the imaging apparatus detects the position of the ND filter 13 and the condition of whether the ND filter 13 is in the retracted state or not from the information of the ND encoder 16 when the ND filter 13 is turned on or retracted. . Then, the microcomputer 18 reads correction data corresponding to the position and state conditions of the ND filter 13 from the correction table block 20.

  Based on the read correction data, the correction circuit 21 corrects the original signal of the video signal sent from the image sensor 3 side, so that an image signal without luminance shading is output from the output circuit 7.

  Next, in the imaging apparatus according to the second embodiment, a case where the ND filter 13 is retracted will be described with reference to FIG.

  In the imaging apparatus according to the present embodiment, the position of the ND filter 13 is retracted via (n7), (n8), and (n9), respectively. At this time, as in the case of turning on, the operation of the ND filter 13 operates independently of the diaphragm blades, and here, the operation from the fully turned-on state to the fully retracted state with respect to the optical path takes approximately 1/60 seconds. .

  First, in the case of (n7), the positional relationship before and after the state (t = 7) in which the ND filter 13 enters the retracting operation from the outside of the optical path and retracts to about 1/4 is shown. In this state, the ND filter 13 moves by the arrow Δn7 shown in the figure during Δt.

  Next, (n8) shows the positional relationship before and after the state in which the ND filter 13 is retracted to substantially the center of the optical path (t = 8). In this state, the ND filter 13 moves by an arrow Δn8 shown in the figure during Δt.

  Next, (n9) shows the positional relationship before and after the state in which the ND filter 13 is almost completely retracted from the optical path (t = 9). In this state, the ND filter 13 moves by an arrow Δn9 shown in the figure during Δt.

  First, in the case of (n7), while the ND filter 13 moves during Δt, the CMOS sensor as the image pickup device 3 sequentially reads out, so that luminance shading occurs diagonally, and the correction data is shown in FIG. The pattern is 12 (h7).

  Similarly, in the case of (n8) and (n9), since the luminance shading is oblique, the correction data has the patterns (h8) and (h9).

  Thereby, the microcomputer 18 generates a correction signal for each correction data using the correction table. Since this correction signal is added to the original signal by the correction circuit 21, an imaging signal without luminance shading is output from the output circuit 7.

  As described above, in the imaging apparatus according to the present embodiment, it is possible to correct in real time the luminance shading that occurs depending on whether the ND filter 13 is turned on or retracted and its position. Furthermore, since this imaging device has a small number of parts and a simple configuration, an inexpensive imaging device can be provided.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications and changes can be made without departing from the scope of the present invention.

11 Iris Encoder 13 ND Filter 16 ND Encoder 18 Microcomputer 20 Correction Table Block 21 Correction Circuit

Claims (2)

An image pickup apparatus having a sequential readout type image sensor that photoelectrically converts an incident light beam, and a filter that reduces a light amount of the light beam that can be turned on and off with respect to an optical path of the light beam incident on the image sensor,
Position detecting means for detecting information on the position of the filter and information on the moving direction during the insertion operation or the retraction operation of the filter;
Storage means for storing a plurality of correction data corresponding to information about the position of the filter in the optical path and information about the moving direction;
Of the plurality of correction data stored in the storage means, based on the correction data corresponding to the information related to the position of the filter and the information related to the movement direction detected by the position detection means, the signal output from the image sensor Correction means for correcting shading;
An imaging device comprising: A control method for an imaging apparatus, comprising: a sequential readout type image sensor that photoelectrically converts an incident light beam; and a filter that reduces a light amount of the light beam that can be turned on and off with respect to an optical path of the light beam incident on the image sensor. ,
A position detecting step for detecting information related to the position of the filter and information related to the moving direction during the insertion operation or the retraction operation of the filter;
Among the plurality of correction data corresponding to the information about the position of the filter in the optical path and the information about the movement direction stored in the storage means, the information about the position of the filter and the movement direction detected in the position detection step. An extraction step for extracting the correction data corresponding to the information;
A correction step for correcting shading of a signal output from the image sensor based on the correction data extracted in the extraction step;
A method for controlling an imaging apparatus, comprising:

Images