JPH0244879A - Digital electronic camera - Google Patents

Abstract

PURPOSE:To efficiently use a memory by making the data bit number ot a video signal to be written in a memory card variable by switching a low resolution mode switch. CONSTITUTION:At the time of photographing by an electronic camera, a luminance signal coming from an image pickup signal processing circuit or an image pickup signal processing circuit output is turned into a digital luminance signal by an analog-digital converter or by passing through the analog-digital converter and a digital signal processing circuit respectively. Low resolution data is generated by comparing or operating this digital luminance signal and reference data generated previously. Besides, the reference data is the maximum value and the minimum value or the mean value of the digital luminance signal or the output of a ROM to be controlled by a light receiving element output, etc. Thus, by providing a low resolution mode, storage capacity can be reduced for a picture not necessitating resolution.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an electronic camera that converts a photographed image into a digital still image signal and stores it in a memory card using a semiconductor memory.

(Prior Art) A digital electronic camera is being considered in which a still image signal is recorded on a memory card equipped with a semiconductor memory and a backup battery. In this process, a video signal is converted into an electric signal by a solid-state image element such as a COD, and then processed as an image signal, digitized, and stored in a memory card through digital signal processing.The digital image signal is read out from the memory card in a playback machine and is then reproduced as a playback signal. This system outputs data to a monitor after processing.

A large amount of memory is required to digitally record this image.For example, the number of images of the currently commonly used CCD is approximately 400,000 pixels, and the resolution required for the image is 8.
Approximately 3.2 megabits of memory is required for one picture, and in order to eliminate this large amount of memory, improvements have been made to the signal processing system and the storage format on the memory card.

In ordinary photography such as landscape photographs and snapshots, it is desirable to memorize and reproduce the information in as much detail and fidelity as possible, but when photographing and memorizing maps, documents, black and white illustrations, etc., it may not be necessary to be so detailed and faithful. In such a case, if only the luminance signal is used and the resolution is reduced, the amount of memory required can be reduced.

Furthermore, although facsimiles have spread to ordinary households, they have the inconvenience of being able to send and receive only specified paper and specified sizes. If a memory card input/output device is attached to this facsimile communication device, it will be possible to reduce or enlarge the size that cannot be sent with current fiximeter by taking pictures with an electronic camera, or it will be possible to send and receive documents written on objects. Dew.

(Problem to be solved by the invention) In this way, with conventional technology, electronic cameras using memory cards perform the same signal processing as normal images even for images that do not require that much resolution, and require the same amount of storage capacity. An object of the present invention is to provide an electronic camera that has a low resolution mode and can reduce the storage capacity for images that do not require resolution.

[Structure of the invention]

(Means for Solving the Problems) An electronic camera according to the present invention detects the digital luminance signal by means for determining the maximum value and minimum value, means for determining the average value, or photometric means of the effective pixel area of the image sensor. Means for reading ROM data corresponding to the amount of light input to the camera Generates effectively quantized data of n bits per sample from the reference pig and digital luminance signal obtained by any of these methods,
n (AD resolution), and is characterized by having means for storing this in a memory card.

(Function) When an image is taken with an electronic camera, the luminance signal output from the imaging signal processing circuit is converted into an analog-to-digital converter.
Alternatively, the output of the imaging signal processing circuit becomes a digital luminance signal by passing through an analog-digital converter and a digital signal processing circuit. Low-resolution data is generated by comparing or calculating this digital luminance signal with reference data prepared in advance.

The reference data is the maximum value and minimum value of the digital luminance signal, the average value, or the ROM output controlled by the light receiving element output.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of a digital electronic camera according to the present invention. An analog image signal obtained from a solid-state image sensor such as a CCD is processed by an image signal processing circuit, A.
It passes through a D circuit and a digital signal processing circuit to become a digital image signal. This digital image signal can be considered in various ways, such as a composite signal, YIQ signal, Y, RY, BY signal, etc., but here, the Y signal is used. This Y signal enters the low resolution data generation circuit,
In this circuit, when shooting in low resolution mode,
A low-resolution image is generated by comparison or calculation with reference data that has been created in advance, and is stored in a memory card through a card interface circuit.

This low-resolution pig has a resolution of n<AD, assuming n pips 1- per sample.

There is a method of using the maximum and minimum values of the brightness levels of effective pixels as reference data, and a low-resolution data generation circuit in this case is shown in FIG.

At this time, it is necessary for the luminance signal to enter this circuit twice from the digital signal processing. The first time, the maximum and minimum values in the effective pixels are determined. This can be obtained by using a comparator and memory to compare the maximum and minimum values each time sampling data comes in. Low-resolution storage data is calculated and generated by a low-resolution data generator using the maximum value and minimum value obtained the second time and the incoming luminance signal. This calculation can be performed by comparing the intermediate value between the maximum value and the minimum value with the luminance signal, and storing the result as data. At this time, n=1. The situation at this time is shown in Figure 3. If you want to increase the number of bits n, for example if n = 2, divide the area between the maximum and minimum values into 4,
The threshold value is set in three comparators and compared with the luminance signal. This output can be combined into 2 bits. However, in this method, when n becomes large, the number of comparators increases exponentially.

The low-resolution data generator shown in FIG. 4 has been improved with this point in mind.

Here, the minimum value data is subtracted from the maximum value data using a subtracter to obtain the difference, and this is entered into the shift calculation circuit. This circuit checks how many pieces of data are 110" from the MSB of the difference data, and sends the result to the shift circuit to shift the luminance signal with the minimum value data subtracted. The MSB of the difference data is 111". Do not shift when . When the MSB is 0'' and the next pips 1 to 1 are It I II, the shift circuit input signal is shifted by 1 in the MSB direction.

In other words, it is doubled. If two bits from the MSB of the difference data are “O” and the third bit is II I II, the shift is M
It is multiplied by 2, that is, by 4, in the SB direction. This configuration effectively quantizes the signal. A specific example of this circuit is shown in FIG.

When the photographer predetermines the value of n representing the resolution when photographing in the low resolution mode, n-bit data starting from the MSB of the shift circuit output is stored in the memory card.

There is a method of using the average value of effective pixels as the reference data.

The low-resolution data generation circuit at this time is shown in FIG. At this time as well, it is necessary to input the luminance signal data twice, and the data is added the first time in the average value circuit, which is the number of samples n. The circuit can be simplified by setting m to a power of 2.

At the second time, this average value and the luminance signal are compared by a comparator in the low-resolution pig generator, and the output is used as stored data. In this method, only n=1.

There is also a method of using reference data as output data of the ROM. This method is shown in FIG. The data in this ROM is output by a ROM control controlled by the amount of light detected by a photometric element included in the camera. R data corresponding to the amount of light input to the camera
The stored data is generated by storing the data in the OM and comparing this data with the luminance signal. In this method, the luminance signal is read out once, n=1.

When using the maximum value, minimum value, or average value as reference data, it is necessary to read the luminance signal twice as described above. As this method of double reading, two CCDs are used.
(Figure 7)
, a method of using a memory card as a buffer memory (FIG. 8), etc. can be considered.

The maximum value, minimum value, or average value varies greatly depending on whether the object to be photographed occupies all of the effective pixels or only a part of them, and this greatly influences the effectiveness of the stored data. It would be convenient to have a switch for using all effective pixels or only some, for example only the center, in calculating the maximum, minimum or average value.

When using only the part, only the pixels at a predetermined position of the effective pixels are calculated or compared.

〔Effect of the invention〕

According to the present invention, in a digital electronic camera using a memory card, memory can be used efficiently by selectively using images that require resolution and images that do not require resolution, depending on the situation.

Furthermore, by connecting to a facsimile communication device, it is possible to send and receive images of a size that cannot be sent and received by current facsimile machines, as well as images written on objects other than those specified.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a schematic configuration of a digital electronic camera according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a low-resolution data generation circuit of a digital electronic camera according to an embodiment of the present invention. Figure 3 is a block diagram showing one embodiment of the low resolution data generator shown in Figure 2;
5 and 6 are block diagrams showing another embodiment, and FIGS. 7 and 8 are respectively different implementations] A block diagram showing a schematic configuration of an example, FIG. 9 is a diagram showing a specific circuit example of the block diagram shown in FIG. 4. Agent Patent Attorney Ken Nori Chika Yudo Mitsuyuki Matsuyama

Claims (1)

[Claims] (1) In a digital electronic camera that stores a digital still image signal obtained based on a shooting command from a shutter button in a predetermined memory area of a memory card equipped with a semiconductor memory and a backup battery. A digital electronic camera comprising a low resolution mode switch, and by switching this switch, the number of data bits of a video signal written to a memory card can be varied. (2) When the low-resolution mode switch is turned on, the maximum and minimum values of the luminance signal are stored in advance, and these are used to generate data to be stored in the memory card. The electronic digital camera described. (3) The digital electronic camera according to claim 1, wherein when the low-resolution mode switch is turned on, an average value of the luminance signal is taken in advance, and this is used to generate data to be stored in the memory card. (4) When the low-resolution mode switch is turned on, the data stored in the ROM corresponding to the amount of light detected by the photometric element included in the digital electronic camera is read out and used to store it on the memory card. 2. The digital electronic camera according to claim 1, wherein the digital electronic camera generates data that corresponds to the digital camera. (5) A claim characterized in that the image signal is read out twice from the imaging unit, a maximum value and a minimum value or an average value are created in the first readout, and these are used to generate data to be stored in the memory card in the second readout. The electronic digital camera according to item 1, 2 or 3. (5) Store the signal-processed data that has become a digital luminance signal in the buffer memory, and at the same time create a maximum value, minimum value, or average value. After one screen has been stored, read the data in the buffer memory, and use this and the maximum value. 4. The digital electronic camera according to claim 1, wherein the data to be stored in the memory card is generated using the value and the minimum value or the average value. (7) At the same time as storing the digital luminance signal data in the memory card, create the maximum value, minimum value or average value, and
A claim characterized in that after the screen has been stored, the data on the memory card is read out, and n-bit data is generated using this and the maximum value, minimum value, or average value, and this is stored on the memory card. The digital electronic camera according to 1, 2 or 3. (8) The digital electronic camera according to claim 1, wherein the maximum value, minimum value, or average value is created using an effective pixel area. (9) The digital electronic camera according to claim 1, wherein the maximum value, the minimum value, or the average value are created using a part of the effective pixel area.