JP4595231B2 - Electronic camera - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electronic camera that records a subject image as electronic data.
[0002]
[Prior art]
There is known an electronic camera that captures a subject image with an imaging device and records image data output from the imaging device on a recording medium. In such an electronic camera, image data is read from the imaging device according to the data size to be recorded on the recording medium, that is, the number of data to be recorded. In general, since the number of pixels of the imaging device is larger than the number of data to be recorded on the recording medium, the image data is thinned out at a predetermined ratio and read from the imaging device. On the other hand, there is known an electronic zoom that electronically changes a zoom magnification by changing a thinning ratio when image data is read from an imaging device. The electronic zoom changes the readout thinning ratio without changing the number of image data read from the imaging device. For example, if the thinning ratio at the time of image data reading is changed around the pixel at the center of the imaging device, the image data reading area changes around the center of the captured image, and electronic zooming is performed.
[0003]
[Problems to be solved by the invention]
In the electronic camera described above, when the number of pixels in the readout area of the imaging device is smaller than the number of pixels recorded on the recording medium, data corresponding to a larger number of pixels than the number of pixels read from the imaging device is recorded on the recording medium. It will be. In this case, even if the number of pixels read from the imaging device is apparently increased by performing data interpolation or the like, the image is deteriorated. In addition, when data corresponding to pixels output from the imaging device is compressed and recorded on a recording medium, if the number of pixels to be recorded on the recording medium is small and the compression rate at the time of data compression is increased, the image is compressed and processed. Degradation occurs.
[0004]
An object of the present invention is to provide an electronic camera that prevents image deterioration caused by the number of data to be recorded.
[0005]
[Means for Solving the Problems]
  An electronic camera according to the present invention includes an imaging device that captures a subject image, a data reading circuit that reads image data from the imaging device, and image data corresponding to a predetermined region from the imaging region of the imaging device in response to a zoom command. An electronic zoom circuit for instructing the data reading circuit to read out the data to be read out, a data recording circuit for recording the image data read out by the data reading circuit on a recording medium, and an image data read out from the imaging device Depending on the number of pixels and the number of pixels of the image data to be recorded on the recording medium, the number of read pixels corresponding to the vertical side of the image data <the number of recorded pixels on the vertical side, or the horizontal side of the image data When the number of read pixels <the number of recorded pixels on the horizontal side is established, a determination circuit that determines that the image data recorded on the recording medium has deteriorated image quality, A notification circuit for notifying that There has been determined,
It is characterized by providing.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
-First embodiment-
FIG. 1 is a circuit block diagram of an electronic camera according to a first embodiment of the present invention. In FIG. 1, a photographing lens 1 is a zoom lens, and can perform a zooming operation optically. The subject light that has passed through the photographing lens 1 passes through the shutter plate 204 and the diaphragm plate 215 and forms an image on the imaging surface of the CCD 214. The shutter plate 204 is provided with a complete light-shielding portion that shields all light beams that have passed through the lens 1 and an opening that allows all light beams to pass therethrough. When the CCD 214 is exposed, the opening of the shutter plate 204 is set on the optical path, and the complete light-shielding portion is set on the optical path upon completion of exposure. The diaphragm plate 215 is provided with a plurality of diaphragm openings having different opening areas. When the CCD 214 is exposed, a predetermined opening of the diaphragm plate 215 is set on the optical path.
[0008]
When a power switch (not shown) is turned on and the power of the electronic camera is turned on, a control program stored in the ROM 443 is activated by the CPU 439. The aperture drive circuit 453 controls the drive of the step motor 415 according to a command from the CPU 439. The shutter drive circuit 454 drives and controls the step motor 408 according to a command from the CPU 439. The diaphragm plate 215 and the shutter plate 204 are formed in a disc shape, and are respectively driven to rotate by step motors 415 and 408 provided at the rotation centers of the disc.
[0009]
The CPU 439 receives a half-press signal and a full-press signal from a half-press switch and a full-press switch (not shown) that are linked to the shutter button 461, respectively. When a half-press signal is input to the CPU 439, the CPU 439 sets the opening of the shutter plate 204 on the optical path and performs a predetermined photographing preparation operation. When the full-press signal is input to the CPU 439 following the half-press signal, the CPU 439 discharges the electric charge accumulated in the CCD 214 and sets a predetermined opening of the aperture plate 215 on the optical path. Thereby, the subject light is imaged on the imaging surface of the CCD 214 through the photographing lens 1. The time from when the electric charge is discharged until the light path is again blocked by the complete light blocking portion of the shutter plate 204 corresponds to the exposure time of the CCD 214.
[0010]
The CCD 214 accumulates signal charges according to the intensity of light of the subject image formed on the imaging surface. The CCD 214 is supplied with a horizontal drive signal from a digital signal processor (hereinafter referred to as a DSP) 433 and a vertical drive signal from a CCD drive circuit 434 controlled by the DSP 433. That is, the timing of the CCD 214 is controlled by the DSP 433 and the CCD drive circuit 434. The signal charge accumulated in the CCD 214 is swept out by the timing signal and sent to the image processing unit 431 as an image signal.
[0011]
The image processing unit 431 includes a noise removal circuit, a DC reproduction circuit, and the like, and after performing analog processing such as noise removal and gain control on the image signal output from the CCD 214, an analog / digital conversion circuit (hereinafter referred to as an analog / digital conversion circuit). , Called an A / D conversion circuit) 432. The A / D conversion circuit 432 converts the image signal output from the image processing unit 431 into a digital signal, and outputs the converted image data to the DSP 433 described above.
[0012]
The DSP 433 performs image processing such as contour compensation, gamma correction, and white balance adjustment on the image data output from the A / D conversion circuit 432. In the white balance adjustment, the CPU 439 calculates a white balance adjustment value based on data sent from a colorimetric circuit 452 described later, and the DSP 433 uses the calculated adjustment value. Further, the DSP 433 controls the data bus connected to the buffer memory 436 and the memory card 424 to temporarily store the image data subjected to various image processing in the buffer memory 436, and then receives the image data from the buffer memory 436. The data is read, compressed in a predetermined compression format (for example, JPEG method), and recorded on the memory card 424.
[0013]
In addition, the DSP 433 processes the image data captured by the CCD 214 and subjected to the above image processing into image data to be displayed on the display LCD 420 and writes it into the frame memory 435. As a result, a captured image called a freeze image is displayed on the display LCD 420. Further, the DSP 433 also performs data input / output timing management in the above-described recording of the image data in the memory card 424 and recording of the expanded captured image data in the buffer memory 436.
[0014]
The buffer memory 436 in which image data based on the output of the CCD 214 is temporarily stored is used to alleviate the difference in the input / output speed of image data with respect to the memory card 424 and the processing speed in the CPU 439, DSP 433, and the like. The The timer 445 has a built-in clock circuit, outputs time data corresponding to the current time to the CPU 439, and is also used as a counter during timer operation to be described later. The time data is recorded on the memory card 424 together with the image data described above.
[0015]
The color measuring element 417 detects the color temperature of the main subject and its surroundings, and outputs the detected color temperature data to the color measuring circuit 452. The color measurement circuit 452 performs predetermined processing on the analog signal output from the color measurement element 417 to convert it into a digital value, and outputs the converted digital signal to the CPU 439. The in-finder display circuit 440 is a display circuit that controls the in-finder display element 410 on which setting contents in the photographing operation are displayed.
[0016]
An operation signal is input from the zoom operation button 462 to the CPU 439. When the zoom operation button 462 is operated to the tele (T) side, a T operation signal is input to the CPU 439. The zoom operation is performed by optical zoom and electronic zoom. When the T operation signal is input from the zoom operation button 462, the CPU 439 sends a command to the zoom lens driving circuit 430 to drive the photographing lens 1 to the zoom-up side. When the T operation signal is further input after the photographing lens 1 is driven to the telephoto end, the CPU 439 reduces the number of read pixels of the image signal picked up by the CCD 214 and performs electronic zoom-up.
[0017]
FIG. 2 is a diagram for explaining the electronic zoom. In FIG. 2, the effective imaging area 21 of the CCD 214 has 2048 pixels in the horizontal direction and 1536 pixels in the vertical direction. In this case, the maximum number of pixels read from the CCD 214 is 2048 × 1536 pixels. When the electronic zoom magnification is x1, the effective imaging area 21 of the CCD 214 and the readout area for reading out image signals from the CCD 214 coincide. That is, an image signal is read from the entire effective imaging area 21 of the CCD 214.
[0018]
In the case of electronic zoom-up, a readout area 22 centered on the central point O is extracted from the effective imaging area 21 of the CCD 214, and an image signal is read out from the readout area 22. For example, if the readout area 22 is an area composed of 1000 pixels in the horizontal direction and 750 pixels in the vertical direction, the readout area 22 is reduced to 1 / 2.048 in both the vertical and horizontal directions with respect to the effective imaging area 21. Thus, electronic zooming is performed by reading out the image signal from the narrow readout region 22 at the center of the CCD 214 and performing the vertical and horizontal enlargement processing on the read image signal (2.048 times in the above example). . In this case, narrowing the image signal readout region 22 from the CCD 214 is equivalent to reducing the number of readout pixels from the CCD 214. The number of pixels read from the CCD 214 is controlled by the DSP 433 according to a command from the CPU 439.
[0019]
On the other hand, when the zoom operation button 462 is operated to the wide (W) side, a W operation signal is input to the CPU 439. When the W operation signal is input from the zoom operation button 462, the CPU 439 increases the number of pixels of the image signal read by the CCD 215 and performs electronic zoom down. In this case, increasing the number of pixels read from the CCD 214 is equivalent to widening the image signal readout area 22 from the CCD 214. When a W operation signal is further input after zooming down the electronic zoom magnification to x1, the CPU 439 sends a command to the zoom lens driving circuit 430 to drive the photographing lens 1 to the zoom down side. As described above, the electronic zoom operation is used in the case of further zooming up after zooming up to the telephoto end by optical zoom.
[0020]
An operation signal is input to the CPU 439 from the recording pixel number changeover switch 463. Each time an operation signal is input from the recording pixel number changeover switch 463, the CPU 439 changes the recording pixel number when recording an image on the memory card 424, for example, 640 × 480 (VGA size) → 1024 × 768 (XGA size). ) → 1600 × 1200 (SVGA size) → 2048 × 1536 (full size) → 640 × 480 (VGA size) →... The number of pixels described above is the number of horizontal pixels constituting the screen × the number of vertical pixels.
[0021]
The number of pixels recorded on the memory card 424 is smaller than the number of pixels captured by the CCD 214 except in the case of the full size described above. Therefore, the CPU 439 sends a command to the DSP 433 to perform read control so that the image signal is read according to the number of recorded pixels. That is, the DSP 433 reads out the image signal from the CCD 214 at a predetermined ratio according to the number of recording pixels. Unlike the electronic zoom described above, the number of read pixels read from the CCD 214 is changed by the thinning-out reading accompanying the change in the number of recorded pixels, but the image signal read area is not changed. That is, when the electronic zoom magnification is x1, the range of the readout area 22 is the same as the effective imaging area 21 regardless of the number of recording pixels recorded on the memory card 424.
[0022]
As described above, in the electronic camera according to the first embodiment, the number of readout pixels read from the CCD 214 changes according to the electronic zoom magnification and the number of recording pixels. If the number of pixels read from the CCD 214 is N and the number of recording pixels to be recorded on the memory card 424 is represented by P, the number of data to be recorded on the memory card 424 is insufficient under the condition of N <P. In order to increase the number of recorded data, for example, when data interpolation is performed on data for N pixels, the number of data after data interpolation can be made equal to the number of recorded data P. At this time, degradation of image quality occurs due to data interpolation. The present invention is characterized in that a photographer detects that a setting of N ≦ P is performed, and notifies (warns) the photographer of the possibility of image quality deterioration before the image quality deterioration occurs.
[0023]
FIG. 3 is a flowchart for explaining a flow of notification processing performed by the CPU 439 for each image capturing by the electronic camera according to the first embodiment. When a main switch (not shown) of the camera is turned on and a predetermined initial setting is performed on the electronic camera, the processing program shown in FIG. 3 is activated. In step S1 of FIG. 3, the CPU 439 sets the recording pixel number P in accordance with the operation signal from the recording pixel number changeover switch 463, and proceeds to step S2. In step S2, the CPU 439 sets the number N of pixels read from the CCD 214 according to the recording pixel number P, and proceeds to step S3.
[0024]
In step S3, the CPU 439 determines whether or not the shutter button 461, that is, the release button has been pressed. If an operation signal is input from the release button, the CPU 439 makes a positive determination in step S3 and proceeds to step 11. If an operation signal is not input from the release button, the CPU 439 makes a negative determination in step S3 and proceeds to step S4. In step S11, the CPU 439 performs predetermined photographing and recording operation on the memory card 424, and ends the processing of FIG.
[0025]
In step S4, the CPU 439 determines whether or not the zoom operation button 462 has been operated to the T side. When a T operation signal is input from the zoom operation button 462, the CPU 439 makes an affirmative determination in step S4 and proceeds to step 5. When a T operation signal is not input from the zoom operation button 462, a negative determination is made in step S4. Return to S3. In step S5, the CPU 439 issues a command to the zoom lens driving circuit 430 to drive the photographing lens 1 to the zoom-up side. Thereby, optical zoom-up is performed.
[0026]
In step S <b> 6, the CPU 439 determines whether the photographing lens 1 has been driven to the telephoto end based on a signal indicating the lens position from the zoom lens driving circuit 430. The CPU 439 makes an affirmative decision in step S6 when the optical lens, that is, the photographing lens 1 is driven to the telephoto end, and proceeds to step S7. If the photographing lens 1 is not driven to the telephoto end, the CPU 439 negates step S6. Determine and return to step S3. When returning to step S3, the above processing is repeated.
[0027]
In step S <b> 7, the CPU 439 determines whether N × 0.9 ≦ P is satisfied. If N × 0.9 ≦ P holds, the CPU 439 makes a positive determination in step S7 and proceeds to step S8. If N × 0.9 ≦ P does not hold, the CPU 439 makes a negative determination in step S7 and proceeds to step S9. move on. Here, the reason why N × 0.9 is compared with P is that, as will be described later, N is multiplied by × 0.9 in order to increase the electronic zoom magnification by one step. Increasing the read pixel number N by × 0.9 is equivalent to increasing the electronic zoom-up magnification by × 1.1. If it is determined in step S7 that there is a possibility that image quality deterioration may occur when zooming up further from the current electronic zoom magnification, this can be detected before zooming up. That is, the determination in step S7 is affirmative when there is a risk of image quality deterioration due to the next zoom-up, and the negative determination is made in step S7 when there is no possibility of image quality deterioration due to the next zoom-up. is there.
[0028]
In step S8, the CPU 439 issues a command to the in-finder display circuit 440 to cause the in-finder display element 410 to display a warning. As a result, the photographer is notified of the image deterioration determination. Further, the CPU 439 stops the electronic zoom operation for one second by the timer operation by the timer 445. The electronic zoom operation is stopped by ignoring the T operation signal from the zoom operation button 462. When 1 second has elapsed, the CPU 439 resumes the electronic zoom operation and proceeds to step S9.
[0029]
In step S9, the CPU 439 determines whether or not the read pixel number N is equal to or less than a predetermined value. Here, the predetermined value is determined according to the recording pixel number P and the effective pixel number of the CCD 214. For example, when the number of effective pixels of the CCD 214 is 2048 × 1536 and the number of recording pixels P is 640 × 480 (VGA size), the predetermined value is 512 × 384. In this case, the electronic zoom magnification is limited to x4. When the number N of read pixels becomes equal to or smaller than the predetermined value, the CPU 439 makes a positive determination in step S9 and returns to step S3. In this case, further electronic zoom-up is not performed. On the other hand, if the read pixel number N is not less than or equal to the predetermined value, the CPU 439 makes a negative determination in step S9 and proceeds to step S10. In this case, further electronic zoom-up is performed.
[0030]
In step S10, the CPU 439 reduces the number of readout pixels by multiplying the current readout pixel number N by × 0.9, and returns to step S3. As a result, the number of readout pixels of the image signal picked up by the CCD 214 is reduced, and electronic zoom up is performed.
[0031]
As described above, according to the first embodiment, when the electronic zoom magnification is increased, the number of read pixels after the electronic zoom is increased, that is, the current read pixel number N × 0.9 times is added to the memory card 424. When the number of recorded pixels is equal to or less than P (affirmative determination in step S7), a warning is displayed on the in-finder display element 410. This notifies the photographer that there is a risk of image quality degradation after the electronic zoom-up. As a result, the photographer can stop the operation of the zoom operation button 462 so as not to perform further electronic zoom-up, so that the image quality can be prevented from deteriorating. In addition, since the electronic zoom operation is stopped for one second in accordance with the warning display, even if the photographer is delayed in noticing the warning display and a time lag occurs until the operation of the zoom operation button 462 is stopped, the electronic zoom is performed. The up operation is not continuously performed, and image quality deterioration due to the electronic zoom up can be prevented.
[0032]
In step S10 described above, in one stage of electronic zoom-up, the number of read pixels of the image signal from the CCD 214 is set to 0.9 times the current read pixel number N (× 1.1 times in terms of zoom-up magnification). However, this value may be set as appropriate. However, the numerical value of the formula used for the determination in step S7 is changed in conjunction with the zoom-up rate in step S10. For example, if the zoom-up rate is N = 0.85 × N in step S10, the determination formula in step S7 is set to N × 0.85 ≦ P.
[0033]
In step S8 described above, both the warning operation and the operation for stopping the zoom operation for one second are performed when there is a possibility that image quality deterioration may occur if the zoom magnification is further increased from the current electronic zoom magnification. Instead of performing both operations, only one of the operations may be performed.
[0034]
In the above description, the warning operation is visually performed using the in-finder display element 410. However, the warning operation may be performed acoustically using a sound source such as a buzzer.
[0035]
The recording pixel number is switched by operating the recording pixel number switch 463. However, instead of the switching operation by the switch 463, it may be switched by menu setting.
[0036]
-Second embodiment-
In the second embodiment, it is detected that the number of pixels read from the CCD 214 is set to be smaller than the number of pixels recorded on the memory card 424 in the electronic camera, and the image quality may be deteriorated after the electronic zoom-up. It is characterized in that different electronic zoom magnifications are displayed depending on the case and the case where there is no risk of image quality deterioration. FIG. 4 and FIG. 5 are flowcharts for explaining the flow of display processing performed for each image taking by the CPU 439 of the electronic camera of the second embodiment. When a main switch (not shown) of the camera is turned on and a predetermined setting is performed on the electronic camera, the processing program shown in FIGS. 4 and 5 is activated. In step S21 of FIG. 4, the CPU 439 performs an initialization operation on the electronic camera and proceeds to step S22. In the initialization operation, when the maximum number of readout pixels of the CCD 214 is 2048 × 1536 pixels, the maximum number of readout pixels in the horizontal direction N0 = 2048. Also, during the initialization operation, a command is issued to the zoom lens driving circuit 430 to drive the photographing lens 1 to the zoom down side. After the photographic lens 1 is driven to the wide end, the optical zoom magnification Z = 1 is set. The optical zoom magnification Z can be set in the range of 1 ≦ Z ≦ Z0. In this embodiment, Z0 = 3. That is, the optical zoom magnification Z can be set in the range of x1 to x3.
[0037]
In step S22, the CPU 439 determines whether or not the shutter button 461, that is, the release button has been pressed. If an operation signal is input from the release button, the CPU 439 makes an affirmative determination in step S22 and proceeds to step S29. If an operation signal is not input from the release button, the CPU 439 makes a negative determination in step S22 and proceeds to step S23. In step S29, the CPU 439 performs predetermined photographing and recording operation on the memory card 424, and returns to step S22.
[0038]
In step S23, the CPU 439 determines whether or not the zoom operation button 462 has been operated to the T side. When a T operation signal is input from the zoom operation button 462, the CPU 439 makes a positive determination in step S23 and proceeds to step 24. When no T operation signal is input from the zoom operation button 462, a negative determination is made in step S23. The process proceeds to step S31 of 5. In step S24, the CPU 439 determines whether or not Na <Pa / 4 is satisfied. Here, Na is the number of pixels in the horizontal direction read from the CCD 214 during electronic zooming, and Pa is the number of pixels recorded in the horizontal direction when image data is recorded on the memory card 424. When Na <Pa / 4 is satisfied, the CPU 439 makes a positive determination in step S24 to proceed to step S36 in FIG. 5, and does not further increase the electronic zoom. On the other hand, if Na <Pa / 4 is not satisfied, the CPU 439 makes a negative determination in step S24 and proceeds to step S25. The reason for comparing Na with Pa / 4 is that when the number of horizontal pixels Na read from the CCD 214 during electronic zoom operation is smaller than 1/4 of the number of recorded pixels Pa in the horizontal direction, data interpolation during electronic zooming is performed. This is because the image is significantly deteriorated after the electronic zoom-up.
[0039]
In step S25, the CPU 439 determines whether or not Z ≦ Z0 / 1.1, that is, whether or not Z ≦ 3 / 1.1 is satisfied for the current optical zoom magnification Z. Here, the reason for comparison with Z0 / 1.1 is that, as will be described later, Z is multiplied by x1.1 in order to increase the optical zoom magnification by one step. When Z ≦ 3 / 1.1 is established, the CPU 439 regards that the optical zoom up is possible, makes an affirmative determination in step S25, proceeds to step S30, and performs an optical zoom up operation. If Z ≦ 3 / 1.1 is not satisfied, the CPU 439 regards that the optical zoom up is not possible, makes a negative determination in step S25, and proceeds to step S26.
[0040]
In step S26, the CPU 439 determines whether or not Na ≧ Pa and Na × 0.9 ≦ Pa. If the above relationship is not established, the CPU 439 performs data interpolation and regards that electronic zoom up is being performed, and makes a negative determination in step S26 to proceed to step S27. On the other hand, if the above relationship is established, the CPU 439 considers that there is a possibility that the image quality may be deteriorated when zooming up further from the current electronic zoom magnification, makes an affirmative decision in step S26, and proceeds to step S28. The determination in step S26 is affirmative when there is a risk of image quality deterioration due to the next zoom-up, and the negative determination is made in step S26 when there is no possibility of image quality deterioration due to the next zoom-up.
[0041]
In step S27, the CPU 439 reduces the number of readout pixels by multiplying the current readout pixel number Na by × 0.9, and proceeds to step S31 in FIG. As a result, the number of readout pixels of the image signal picked up by the CCD 214 is reduced, and electronic zoom up is performed. Note that increasing the readout pixel number Na by × 0.9 times is equivalent to increasing the electronic zoom-up magnification by × 1.1 times.
[0042]
In step S28, the CPU 439 stops the electronic zoom operation for 1 second by the timer operation by the timer 445. This notifies the photographer that there is a risk of image degradation. The electronic zoom operation is stopped by ignoring the T operation signal from the zoom operation button 462. When one second has elapsed, the CPU 439 multiplies the current readout pixel number Na by × 0.9 to reduce the readout pixel number, and proceeds to step S31 in FIG. As a result, the number of readout pixels of the image signal picked up by the CCD 214 is reduced, and electronic zoom up is performed.
[0043]
In step S30, the CPU 439 issues a command to the zoom lens driving circuit 430 to drive the photographing lens 1 to the zoom-up side, and the optical zoom magnification is 1.1 times, and the process proceeds to step S31 in FIG.
[0044]
In step S31 of FIG. 5, the CPU 439 determines whether or not the zoom operation button 462 has been operated to the W side. When the W operation signal is input from the zoom operation button 462, the CPU 439 makes a positive determination in step S31 and proceeds to step 32. When the W operation signal is not input from the zoom operation button 462, the CPU 439 makes a negative determination in step S31. Proceed to S36.
[0045]
In step S32, the CPU 439 determines whether or not the optical zoom magnification Z = 1. When the CPU 439 detects that the photographing lens 1 is at the wide end from the signal indicating the lens position from the zoom lens driving circuit 430, that is, when the optical zoom magnification Z = 1, the CPU 439 makes an affirmative determination in step S32. Proceed to S36. On the other hand, if the optical zoom magnification Z is not 1, the determination in step S32 is negative and the process proceeds to step S33.
[0046]
In step S33, the CPU 439 determines whether or not the optical zoom magnification Z <Z0. When the CPU 439 detects from the signal indicating the lens position from the zoom lens driving circuit 430 that the photographing lens 1 is not at the tele end, that is, when the optical zoom magnification Z <Z0 (in this case Z <3), An affirmative decision is made in step S33 and the process proceeds to step S37. On the other hand, if the optical zoom magnification Z is 3 (the photographic lens 1 is at the telephoto end), a negative determination is made in step S33 and the process proceeds to step S34. The negative determination in step S33 includes the case where the electronic zoom is up.
[0047]
In step S34, the CPU 439 determines whether or not Na = N0 is satisfied. If Na = N0 is satisfied, the CPU 439 makes a positive determination in step S34 and proceeds to step S37. If Na = N0 is not satisfied, the CPU 439 makes a negative determination in step S34 and proceeds to step S35. The affirmative determination is made in step S34 when the readout pixel number Na is not reduced, that is, when electronic zoom-up is not performed. Further, the negative determination in step S34 is when the number of readout pixels Na is reduced, that is, when electronic zoom-up is being performed.
[0048]
In step S35, the CPU 439 increases the number of readout pixels by multiplying the current readout pixel number Na by x1.1, and proceeds to step S36. As a result, the number of readout pixels of the image signal picked up by the CCD 214 is increased, and electronic zoom down is performed. Note that increasing the readout pixel number Na by × 1.1 times is equivalent to increasing the electronic zoom-up magnification by × 0.9 times.
[0049]
On the other hand, in step S37, the CPU 439 issues a command to the zoom lens driving circuit 430 to drive the photographing lens 1 to the zoom down side, and the optical zoom magnification is 0.9 times, and the process proceeds to step S36.
[0050]
In step S36, the CPU 439 determines whether or not Na ≦ Pa is satisfied. If Na ≦ Pa is satisfied, the CPU 439 makes an affirmative determination in step S36 and proceeds to step S38. If Na ≦ Pa is not satisfied, the CPU 439 makes a negative determination in step S36 and proceeds to step S39. In the determination process in step S36, when there is a possibility that the image quality is deteriorated as the electronic zoom is increased, this can be detected. That is, the determination in step S36 is affirmative when there is a risk that image quality will be deteriorated by zooming up, and the negative determination is made in step S36 when there is no possibility that image quality will be deteriorated by zooming up.
[0051]
In step S38, the CPU 439 issues a command to the in-finder display circuit 440 to cause the in-finder display element 410 to display the zoom magnification Zt in red. The zoom magnification Zt is the overall zoom magnification that combines the optical zoom and the electronic zoom, and is expressed as Zt = Z × N0 / Na. The zoom magnification Zt is displayed in red, so that the photographer is notified of the image deterioration determination. When the CPU 439 displays the zoom magnification Zt, the process of FIG. 5 ends.
[0052]
In step S39, the CPU 439 issues a command to the in-finder display circuit 440 to cause the in-finder display element 410 to display the zoom magnification Zt in green. The zoom magnification Zt is expressed by Zt = Z × N0 / Na. When the zoom magnification Zt is displayed in green, the photographer is notified that the image deterioration has not been determined. When the CPU 439 displays the zoom magnification Zt, the process of FIG. 5 ends.
[0053]
According to the second embodiment described above, the following operational effects are obtained.
(1) When the number of read pixels Na after electronic zoom-up is less than or equal to the number of recorded pixels Pa on the memory card 424 (affirmative determination in step S36), the zoom magnification Zt is displayed in red on the in-finder display element 410. Do. On the other hand, when the number of read pixels Na after the electronic zoom-up is larger than the number of recorded pixels Pa on the memory card 424 (No determination in step S36), the zoom magnification Zt is displayed in green on the in-finder display element 410. I tried to go. As a result, the photographer is notified by a red display that there is a possibility that the image quality is likely to deteriorate with the electronic zoom-up.
(2) The electronic zoom operation is stopped for one second (step S28) when there is a possibility that the image quality deterioration may occur after the electronic zoom up when further electronic zoom up is performed (step S26). The photographer can be notified of the image deterioration determination before the electronic zoom-up. Thereby, it is possible to prevent image quality deterioration due to electronic zoom-up.
[0054]
In the example described above, the magnification change in one step of zooming up and zooming down is 0.1 step, but this value may be set as appropriate. However, the numerical value of the formula used for the determination in steps S25 and S26 is changed in conjunction with the zoom magnification change.
[0055]
In the first embodiment and the second embodiment described above, the case where the aspect ratio of the read area 22 is the same as the aspect ratio of the image recorded on the memory card 424 has been described as an example. Therefore, when the number of read pixels N (Na) and the number of recorded pixels P (Pa) are in a relationship of N <P (Na <Pa), there is a similar relationship with each side constituting the image. That is, the number of readout pixels corresponding to the vertical side is Nv, the number of readout pixels corresponding to the horizontal side is Nh, the number of recording pixels corresponding to the vertical side is Pv, and the number of recording pixels corresponding to the horizontal side is Ph. In this case, Nv <Pv and Nh <Ph. However, when the aspect ratio of the read area 22 and the aspect ratio of the image recorded on the memory card 424 are not the same, the above relationship is not established. In this case, when at least one of the number of pixels corresponding to the vertical side and the horizontal side is small, that is, when at least one of Nv <Pv and Nh <Ph is satisfied, data interpolation is performed. It is determined that there is a risk of image quality degradation.
[0056]
-Third embodiment-
The third embodiment is characterized in that the compression rate at the time of compression processing is changed according to the number of recording pixels that the DSP 433 records on the memory card 424. The electronic camera performs processing such as JPEG compression on the image data in order to efficiently record the image data on the memory card 424. The image compression process is executed, for example, according to the following procedures (1) to (6).
(1) The DSP 433 determines the target compression rate of the image data in accordance with the compression image quality setting (for example, switching between FINE / NORMAL / BASIC, etc.) by the photographer.
(2) The DSP 433 divides the image data composed of the luminance Y and the color differences Cb and Cr into blocks each having about 8 × 8 pixels. The DSP 433 further performs DCT (Discrete Cosine Transform) on each of these divided blocks to obtain transform coefficients corresponding to 8 × 8 discrete spatial frequencies.
(3) The DSP 433 prepares a reference quantization table in which quantization steps are defined corresponding to each of 8 × 8 transform coefficients. The DSP 433 multiplies the reference quantization table by the scale factor SF to obtain a quantization table that is actually used.
(4) The DSP 433 quantizes each of the 8 × 8 transform coefficients using the quantization table obtained in (3).
(5) The DSP 433 compresses the quantized data by performing coding such as variable length coding or run length coding.
{Circle around (6)} The DSP 433 returns the operation to the above {circle around (3)} after adjusting the value of the scale factor SF when the compression size is out of the target compression rate range. On the other hand, when the compression size falls within the target compression rate range, the image compression is terminated.
Through the above processing, the image data is compressed at the target compression rate.
[0057]
FIG. 6 is a diagram illustrating divided blocks performed in the above-described compression processing. 6A, when the number of pixels P recorded on the memory card 424 is 2048 × 1536 pixels (full size), FIG. 6B is when the number of pixels recorded on the memory card 424 is 640 × 480 (VGA size). Is the case. As described above, the number of pixels constituting the image data is switched by operating the recording pixel number switching switch 463. A block 61 in FIG. 6A and a block 62 in FIG. 6B each represent one block of 8 × 8 pixels at the time of compression processing. When the recording pixel number P is 2048 × 1536 pixels, one block 61 is 1/256 of one image. On the other hand, when the recording pixel number P is 640 × 480 pixels, one block 62 is 1/80 of one image. That is, the ratio per block with respect to one image increases as the recording pixel number P decreases.
[0058]
In general, when the ratio per block with respect to one image increases, the high-frequency component contained in the block increases. When the compression ratio at the time of compression processing is increased in this state, the quantization step is expanded, and a large quantization noise is generated after quantization. The generated quantization noise appears as block noise on the decompressed image. Block noise degrades image quality. The electronic camera according to the third embodiment determines the compression rate according to the recording pixel count P in order to prevent such block noise.
[0059]
FIG. 7 is a diagram illustrating an example of the compression rate determined by the image quality setting and the recording pixel number P. The image quality setting is to set how much block noise is allowed, and is switched by the photographer according to the menu setting of the camera. The image quality setting of the electronic camera according to the present embodiment can be switched to three stages of FINE / NORMAL / BASIC. Of these, FINE has high image quality, BASIC has low image quality, and NORMAL has intermediate image quality. As for the data size (code amount) after compression processing, when the number of recording pixels P is the same, the image quality setting is the highest when the setting is FINE, and the data size (code amount) is the lowest when it is BASIC. As shown in FIG. 7, the compression rate is higher as the number P of recorded pixels is larger, and is lower as the image quality setting is higher.
[0060]
FIG. 8 is a flowchart for explaining the flow of the compression rate setting process performed by the DSP 433 of the electronic camera according to the third embodiment. When either the camera image quality setting or the recording pixel count P is set, the processing program shown in FIG. In step S <b> 101, the CPU 439 sends the contents of the image quality setting by compression (FINE / NORMAL / BASIC) and the setting contents of the recording pixel number P to the DSP 433. Thus, the DSP 433 sets the compression rate to 1 / M according to FIG.
[0061]
In step S102, the DSP 433 determines whether or not the recording pixel number P has been changed. If the DSP 433 determines that the recording pixel number P has been changed by the signal sent from the CPU 439, the DSP 433 makes an affirmative determination in step S102 and proceeds to step S103. If it is determined that the recording pixel number P is not changed, a negative determination is made in step S102, and the processing in FIG.
[0062]
In step S103, the DSP 433 changes the compression rate according to FIG. 7 according to the image quality setting of the camera and the setting contents of the recording pixel number P. When the compression rate is changed, the process shown in FIG. 8 ends.
[0063]
As described above, according to the third embodiment, when the number P of image recording pixels to be recorded on the memory card 424 is changed, the DSP 433 sets the image quality setting by compression (FINE / NORMAL / BASIC) and the recording pixels. The compression rate at the time of compression processing is changed according to the number P. Therefore, an appropriate compression rate is determined so that block noise caused by quantization noise caused by quantization at the time of compression is reduced to a necessary minimum, and compression processing is performed at this compression rate. As a result, for example, if the number of pixels to be recorded in the memory card 424 is reduced, the compression rate at the time of data compression is changed to low compression, so that it is possible to reduce image degradation due to block noise caused by compression processing.
[0065]
【The invention's effect】
  With the electronic camera according to the present invention, it is possible to appropriately determine image quality degradation due to the magnitude relationship between the number of readout pixels and the number of recording pixels.
[Brief description of the drawings]
FIG. 1 is a circuit block diagram of an electronic camera according to a first embodiment of the present invention.
FIG. 2 is a diagram illustrating electronic zoom.
FIG. 3 is a flowchart illustrating a flow of notification processing performed by the electronic camera of the first embodiment.
FIG. 4 is a flowchart for explaining a flow of display processing performed by the electronic camera of the second embodiment.
FIG. 5 is a flowchart illustrating a flow of display processing performed by the electronic camera according to the second embodiment.
6A and 6B are diagrams illustrating divided blocks performed in compression processing. FIG. 6A illustrates a case where the number of recording pixels is 2048 × 1536 pixels (full size), and FIG. ).
FIG. 7 is a diagram illustrating a compression rate determined by image quality setting and the number of recording pixels.
FIG. 8 is a flowchart for explaining the flow of compression rate setting processing performed by the electronic camera of the third embodiment.
[Explanation of symbols]
1 ... photographic lens, 214 ... CCD,
410: Display element in viewfinder, 424: Memory card,
430 ... zoom lens drive circuit, 433 ... DSP,
434: CCD drive circuit 434, 439 ... CPU,
440 ... finder display circuit, 445 ... timer,
461 ... Shutter button, 462 ... Zoom operation button,
463 ... Recording pixel number selection switch

Claims (3)

An imaging device for imaging a subject image;
A data read circuit for reading image data from the imaging device;
An electronic zoom circuit for instructing the reading area to the data reading circuit so as to extract and read out image data corresponding to a predetermined area from the imaging area of the imaging device in response to a zoom command ;
A data recording circuit for recording image data read by the data reading circuit on a recording medium;
Depending on the number of pixels of the image data to be recorded in the number of pixels and the recording medium of the image data read from the image pickup apparatus, a recording of the number of reading pixels corresponding to the vertical sides of the image data <longitudinal sides When the number of pixels or the number of read pixels corresponding to the horizontal side of the image data <the number of recorded pixels on the horizontal side is satisfied, it is determined that the image data recorded on the recording medium has a deterioration in image quality. A determination circuit to
A notification circuit for notifying that the image quality degradation is determined by the determination circuit,
An electronic camera comprising: The electronic camera according to claim 1,
When said deterioration in image quality in the image data by determining circuit is determined that there, an electronic camera, characterized by further comprising a control circuit to temporarily disable the zoom command. The electronic camera according to claim 1 or 2,
A display device for performing a first display indicating an electronic zoom magnification by the electronic zoom circuit and a second display indicating an electronic zoom magnification causing image degradation;
A display control circuit that switches between the first display and the second display according to a determination result by the determination circuit ;
An electronic camera , further comprising:

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