JPH1155478A - Image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the quality of photographing a moving body and to extend the permissible illuminance range of photographing a still object. SOLUTION: The image pickup device 1 provided with a line sensor 11 and a subscanning means deflecting an object light to scan an object image in line sequence is provided with a rotary polygon mirror device 14 as the subscanning means, with a means 51 that measures the illuminance of the object, a means 90 that controls the line sensor 11 and the rotary polygon mirror device 14 for pluralities of number of scanning when the measured illuminance is a set value or below, and a means 85 that calculates a mean value of photographing data obtained by pluralities of number of scanning as output information.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a line sensor (1).
A two-dimensional optical image is converted into an image signal by a two-dimensional image sensor.

[0002]

2. Description of the Related Art An apparatus that performs two-dimensional imaging using a line sensor and a mechanical sub-scanning mechanism can perform imaging at a higher resolution than an apparatus that performs imaging using an area sensor, and mainly reads various documents. It is used for Among these types of devices, particularly small devices such as digital cameras and film scanners incorporate a mirror rotation mechanism as a sub-scanning mechanism. The mirror rotation mechanism is easier to reduce in size and simpler in electric wiring than the mechanism for moving the line sensor, and is excellent in high-speed operation.

[0003]

By the way, the photographing by the line sensor is one time smaller than the photographing by the area sensor.
Since the photoelectric conversion time (exposure time) per pixel is short, there is a problem that when the subject is dark, the S / N ratio deteriorates and the image quality deteriorates. The speed of scanning for capturing fast-moving objects and moving images further reduces the image quality. In addition, since the time required for imaging is long, there is also a problem that the influence of luminance fluctuation of a pulsating illumination light source represented by a fluorescent lamp appears in a captured image mainly in indoor photography. That is, the exposure condition changes during the photographing in accordance with the fluctuation of the commercial AC voltage, so that stripe-like unevenness occurs.

As a measure for improving the S / N ratio, there has been proposed a method of increasing the sensor sensitivity by cooling a line sensor and mounting a micro lens. However, the improvement effect is small at present (less than twice the SN ratio). As a measure against the pulsating illumination, there is a method of driving a plurality of line sensors at an appropriate timing (Japanese Patent Application Laid-Open No. H7-111556). In this method, high accuracy is required for the arrangement of the line sensors, and it is difficult to reduce the cost of the apparatus.

SUMMARY OF THE INVENTION It is an object of the present invention to improve the quality of moving image shooting and expand the allowable illuminance range of still image shooting. Another object is to reduce the influence of illuminance fluctuation of the subject.

[0006]

According to a first aspect of the present invention, there is provided a photographing apparatus which includes a line sensor and a sub-scanning means for deflecting subject light, and scans a subject image in a line-sequential manner. A rotating polygon mirror mechanism is provided as a means, a means for measuring the illuminance of the subject, and the line sensor and the line sensor for performing a plurality of scans on the subject when the measured illuminance is equal to or less than a set value. Means for controlling a rotating polygon mirror mechanism; and means for calculating, as output information, an average value of photographing data obtained by performing a plurality of scans on the subject.

According to a second aspect of the present invention, there is provided an apparatus comprising: means for measuring a variation cycle of the illuminance of the subject; and means for setting a cycle of a plurality of scans of the subject in accordance with the measured variation cycle. Have.

[0008]

FIG. 1 is a diagram showing a configuration of a line sensor camera 1 to which the present invention is applied, and FIG. 2 is a schematic diagram of an imaging optical system.

The line sensor camera 1 is a hand-held type photographing device, and is used as high-resolution digital image input means. A window 10a for guiding subject light to the inside is provided on the front surface of the housing 10, and a lens 12 for imaging is arranged behind the window 10a. Lens 12
Is reflected by the surface of the polygon mirror 15 and enters the line sensor 11. Housing 10
A photometric sensor 51 is mounted on the front surface of the device, and a release switch 63 is disposed on the upper surface.

The lens 12 has a focusing actuator (not shown). Line sensor 11 is CC
A D imaging device, which is fixed at a position where a subject image is formed. Another imaging device (for example, a MOS imaging device) can be used as the line sensor 11.

The polygon mirror 15 is an optical member in the form of a square prism having four side surfaces serving as reflection surfaces 151 to 154, respectively, and is connected concentrically with the rotation axis of the motor 16. This rotation axis is parallel to the pixel array direction (main scanning direction) of the line sensor 11. As the polygon mirror 15 rotates, the subject light is deflected in the sub-scanning direction as shown in FIG.
Are projected on the light-receiving surface of. That is, the polygon mirror 15 and the motor 16 constitute the rotating mirror mechanism 14 as a sub-scanning unit. One photographing (scanning for one frame) involves one reflecting surface. In other words, by rotating the polygon mirror 15 by 360 °, 4
You can take multiple shots. The motor 16 is provided with a rotation sensor 55 for detecting a rotation angle and a rotation speed.

FIG. 3 is a functional block diagram of the line sensor camera 1. As described above, the line sensor camera 1 includes an imaging system 1a for scanning a subject image line-sequentially by the line sensor 11 and the rotating mirror mechanism 14, a signal processing system 1b for outputting photographing data of a predetermined format, and a microprocessor. And a control system 1c composed mainly of a CPU 90 having

The CPU 90 includes a CCD driving circuit 91, a lens driving circuit 92, and a mirror driving circuit 94 in accordance with operation information from the switch group 60 and detection information from various sensors.
And other appropriate instructions. A control memory 98 is used as a work area for this control. In response to a start request from the CPU 90, the CCD drive circuit 91 outputs a signal that defines the timing of CCD integration (charge accumulation) to the line sensor 11. Line sensor 11
Latches the charge of each pixel in response to the integration end signal,
The signal processing system 1 as the photoelectric conversion signal S11 in the pixel arrangement order.
Output to b. This main scanning is repeated at a constant cycle (= imaging time T / number of lines n).

In the signal processing system 1b, the photoelectric conversion signal S
Reference numeral 11 denotes an AD converter 81, which is sampled and held in synchronization with a pixel clock, and has a predetermined number of bits (for example, 8 bits).
Is converted to shooting data DG. The photographing data DG is sequentially stored in the image memory 82, and is transferred to the image processing circuit 83 in the order of pixel arrangement after photographing the number of times set according to the illuminance of the subject as described later. When the photographing is performed a plurality of times, the addition arithmetic circuit 85 calculates the average value DG ′ of the photographing data DG for the plurality of times for each pixel, and transfers the average value DG ′ to the image processing circuit 83 as the photographing data DG to be processed. The image processing circuit 83 performs predetermined image processing including image quality correction on the input photographing data DG regardless of whether photographing is performed only once or plural times. The processed image data is transferred to interface 8
4 to an external device. As an external device,
Image editing device represented by computer system, IC
There are storage media including cards, and image output devices such as printers and displays. It should be noted that a storage medium may be built in and the line sensor camera 1 may store shooting information. In this case, the stored information is transferred to the external device by data communication or transfer of the recording medium as appropriate.

The line sensor camera 1 having the above configuration has a function unique to the present invention for changing the number of times of photographing according to the illuminance of the subject. Hereinafter, this function will be described. FIG. 4 is a diagram illustrating an example of setting of the number of times of photographing according to the illuminance of a subject.

When the subject is sufficiently bright, such as when photographing outdoors on a sunny day, the average illuminance of the subject measured by the photometric sensor 51 is the set value Lth 2000.
lx or more, 1 in response to one release operation
Only a single shooting is performed. The shooting time in this case is 1/60 s, which is the same as that of a general video camera, and the rotation of the polygon mirror 15 is controlled so that sub-scanning of a predetermined angle of view is performed in this time. Since sub-scanning is faster than before,
It is possible to obtain a shot-free image of not only a stationary subject such as a document or a film, but also a moving object or a moving image displayed on a display. If the illuminance fluctuates, shading of the image occurs in the sub-scanning direction. It is desirable to correct this. For example, based on the data value at the maximum illuminance, the data value of the line with low illuminance is multiplied by a predetermined coefficient to make a uniform correction. That is, the conventionally known shading correction in the main scanning direction is applied in the sub-scanning (time axis) direction. Since the amount of incident light on the line sensor 11 is large and the SN ratio is large, sufficient correction can be performed by the coefficient multiplication operation.

On the other hand, when the illuminance is smaller than 2000 lx, the integration time per pixel is increased to increase the SN ratio. However, this does not slow down the rotation of the polygon mirror 15. That is, the time T of one photographing is set to 1/60 s, which is the same as the above case, and photographing at this speed is repeated a number of times according to the illuminance. Then, as described above, a plurality of times of imaging data DG are averaged to obtain one output image. Although the number of repetitions N can be set arbitrarily, in the present embodiment, the smallest integer equal to or larger than a value obtained by dividing the minimum allowable illuminance (here, 2000 lx) in the device specifications by the measured illuminance is set. For example, if the measured illuminance is 7
In the case of 00lx, 2.85 (= 2000 ÷ 700)
Since the smallest integer mentioned above is 3, three shootings are performed continuously. When performing continuous shooting in this way,
Although the imaging quality of a moving object or a moving image is reduced, it is possible to prevent the image quality of a stationary subject from being deteriorated due to insufficient illuminance.

FIG. 5 is a diagram showing the relationship between the illuminance fluctuation and the photographing timing. When the illuminance is smaller than 2000 lx and the illuminance fluctuates, the cycle Ts of the continuous shooting is changed according to the fluctuation cycle Tx. In the example of FIG. 5, the measured illuminance is 6
00lx, and the variation cycle Tx of the illuminance is 1/45 s. 2
Since 000 ÷ 600 ≒ 3.33, the number of repetitions N of photographing is 4. Further, as described above, one shooting time T is 1/60 s.

The period Ts is represented by the following equation. Ts = Tx + Tx / N When the imaging is repeated at the cycle Ts, the phase of the illuminance variation at the start of each imaging shifts by N divisions of the variation cycle Tx. Therefore, by averaging the photographing data of each time, the same photographing data as when illuminating with the average value of the illuminance fluctuation amplitude is obtained, and the influence of the illuminance fluctuation is reduced. When the waveform of the illuminance change has a simple shape such as a rectangular wave or a triangular wave, the average value of the illuminance of each line can be made substantially constant. However, when the waveform is complicated as in some fluorescent lamps, the illuminance may possibly fluctuate.
In such a case, just like when the subject is bright,
The illuminance change during each photographing is monitored, and correction is performed according to the remaining illuminance change. By the addition, the value of the minimum illuminance in each line is increased, so that the S / N ratio is improved and a high-quality image without unevenness can be obtained.

FIG. 6 is a flowchart showing a schematic operation of the line sensor camera 1. When the start of shooting is instructed by operating the release switch 63, the photometric sensor 5
The illuminance of the subject is determined based on the output of # 1 (# 1, # 1).
2) If the illuminance of the subject is equal to or greater than the set value Lth, only one shooting is performed (# 3). At this time, first, the motor 16
Start and wait for the rotation to stabilize. Then, the line sensor 11 is driven so that imaging is started from the time when the rotation position of the polygon mirror 15 reaches the scanning start position. The obtained photographing data DG is corrected for illuminance fluctuation as necessary (# 4), and data is output to the outside (#
5).

If the illuminance of the object is less than the set value Lth, it is checked whether or not the illuminance has changed (# 6). If the illuminance is constant, the imaging system 1a is operated in a manner similar to that of one-time shooting.
Is driven, and N shootings are performed (# 7). At this time, the photographing data DG of each time is stored in the image memory 82, and the average value DG 'of the photographing data DG for N times is calculated. On the other hand, when there is illuminance fluctuation, a timing setting process for calculating the photographing cycle Ts is performed (# 9). The output of the photometric sensor 51 is monitored over a certain period of time, and the fluctuation period Tx is obtained. Specifically, the time when a predetermined light amount value is straddled in a predetermined direction (for example, when 200 lx has passed from the dark side) is stored, and the elapsed time from the closest time point at which the same illuminance change is observed is measured. In the case of a special light source in which the amount of light repeatedly changes during one cycle, a fluctuation waveform of a predetermined period is sampled, the closest one showing a similar pattern is determined by matching, and the elapsed time from this is measured. Such a method is widely used in the field of waveform analysis of voice and the like. The operation of step # 9 corresponds to the function of the unit for measuring the fluctuation period and the unit for setting the period of a plurality of scans of the present invention. When the cycle Ts is obtained, the photographing is performed a plurality of times with the start timing shifted (# 7), and the photographed data is averaged (# 8), as described with reference to FIG.

In the above embodiment, when the lens 12 is a zoom lens, the mirror rotation angle per frame may be changed in accordance with zooming. When unevenness of the focus position and magnification due to the rotation of the mirror is conspicuous in short-range shooting, control of optical means (such as a lens) according to the rotation position of the polygon mirror 15 and shooting data DG
By performing the geometric correction on, the reproducibility of the image can be improved. The set value Lth of the illuminance, the photographing time T of one frame, and the number of reflection surfaces of the polygon mirror 15 are not limited to the illustrated values. The present invention is applicable not only to a portable type but also to a stationary type photographing apparatus.

[0023]

According to the first or second aspect of the present invention,
The speed of sub-scanning can be increased to improve the quality of moving image shooting, and the allowable illuminance range of still image shooting can be expanded.

According to the second aspect of the present invention, even when the illuminance of the subject changes, it is possible to output a photographed image without unevenness.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a line sensor camera to which the present invention is applied.

FIG. 2 is a schematic diagram of an imaging optical system.

FIG. 3 is a functional block diagram of the line sensor camera.

FIG. 4 is a diagram showing an example of setting of the number of times of photographing according to the illuminance of a subject.

FIG. 5 is a diagram illustrating a relationship between illuminance fluctuation and shooting timing.

FIG. 6 is a flowchart showing a schematic operation of the line sensor camera.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 line sensor camera (photographing device) 11 line sensor 14 rotating mirror mechanism (rotating polygon mirror mechanism) 51 photometric sensor (means for measuring illuminance) 85 addition arithmetic circuit (calculating means) 90 CPU (control means) DG photographing data DG ' Average value L Subject light Lth Set value Tx Fluctuation cycle Ts Imaging cycle (scanning cycle)

Claims (2)

[Claims] 1. A photographing apparatus comprising a line sensor and a sub-scanning means for deflecting subject light, and scanning a subject image in a line-sequential manner, wherein a rotating polygon mirror mechanism is provided as the sub-scanning means. Means for measuring the illuminance of the object, means for controlling the line sensor and the rotating polygon mirror mechanism so as to scan the subject a plurality of times when the measured illuminance is equal to or less than a set value, and Means for calculating, as output information, an average value of photographing data obtained by performing a plurality of scans on the photographing apparatus. 2. The apparatus according to claim 1, further comprising: means for measuring a variation cycle of the illuminance of the subject; and means for setting a cycle of a plurality of scans of the subject in accordance with the measured variation cycle. Shooting equipment.