JPH0229095A - Fluorescent lamp identification device and white balance adjusting device using it - Google Patents

Abstract

PURPOSE:To surely adjust the white balance by using a photodetection section having the sensitivity characteristic for a region whose wavelength is 620nm or over so as to discriminate whether or not the environment light depends on the illumination of the fluorescent lamp. CONSTITUTION:When a light source lighting an object is a fluorescent lamp, since the region where the wavelength is 620nm or over does not almost apply energy radiation, an output signal having a some degree of level is obtained from a blue sensor 16 and a red sensor 17, but the signal output is not almost obtained from the infrared ray sensor 18. A discrimination circuit 44 generates a fluorescent lamp identification and inputs it to a color temperature detection circuit 42. As a result, the color temperature detection circuit 42 is operated in the fluorescent lamp mode and the output signal from the blue filter 16 and the red filter 17 is evaluated to be the light from the fluorescent lamp and detects the color temperature and sends the color temperature signal to a white balance correction control circuit 43.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a device for identifying whether a light source illuminating a subject is a fluorescent lamp, and a white balance for automatically adjusting white balance using the same. It concerns an adjustment device.

[Conventional technology]

Electronic cameras and video cameras generally have a built-in white balance adjustment device. This white balance adjustment device detects the color temperature of a light source illuminating a subject, and corrects primary color signals output from an imaging means such as a CCD according to the color temperature.

By the way, when the light source illuminating the subject is a fluorescent lamp, the amount of illumination light generally tends to be low, and the illumination light flickers depending on the commercial frequency, so the above-mentioned white balance adjustment device is difficult to use. It becomes difficult to operate properly.

Furthermore, in order to eliminate the effects of flickering from fluorescent lights, the shutter speed must be controlled to be slower than 1/60 second, so it is possible to identify in advance that the lighting is from fluorescent lights. It is required to keep it.

Under these circumstances, as described in Japanese Patent Application Laid-Open No. 61-240790, a device has been proposed that detects that the object is under fluorescent lamp illumination based on the flashing cycle of the fluorescent lamp.

[Problem that the invention seeks to solve]

However, the fluorescent lamp identification device described in the above publication performs detection based on the fact that the fluorescent lamp changes depending on commercial frequencies of 50 Hz and 60 H2. therefore,
Regarding high-frequency flashing type fluorescent lamps with a flashing cycle of several hundred Hz and fluorescent lamps used in foreign countries with different commercial frequencies,
This cannot be detected and it is extremely difficult to properly correct the white balance.

[Purpose of the invention]

The present invention has been made to solve the above-mentioned drawbacks of the prior art, and therefore provides a fluorescent lamp identification system that can detect when an object is illuminated by fluorescent lamps without depending on the flashing cycle of the fluorescent lamps. It is an object of the present invention to provide a white balance adjustment device that can accurately adjust the white balance of a camera using this identification device.

[Means to solve the problem]

In order to achieve the above object, the fluorescent lamp identification device according to the present invention focuses on the fact that there is very little light with a wavelength of 620 nm or more in the illumination light from fluorescent lamps, and uses the light from the shooting screen or the surroundings including the shooting screen. Based on the amount of light received in a region with a wavelength of 620 nm or more, it is determined whether the illumination is a fluorescent lamp or not. In other words, in addition to the normal visible light sensor for white balance adjustment, which detects the color temperature of illumination light from a subject in the visible range, there is also an infrared sensor that receives light in the wavelength range of 620 nm or more. It is equipped with an optical sensor and a determining means for determining whether or not it is under fluorescent lamp illumination based on the output of the optical sensor.

Further, in the white balance adjustment device according to the present invention, when the fluorescent lamp identification device identifies that the subject is illuminated by a fluorescent lamp, the correction means for correcting the primary color signal from the imaging means is set to a fluorescent lamp mode. It is configured to work.

Furthermore, when the determination means identifies whether or not the illumination light is a fluorescent lamp, the determination means includes not only the output from the infrared light sensor but also the output from the visible light sensor or the photometric sensor for exposure control. By inputting the information, comparing them, and then identifying them, it becomes possible to perform good identification even when the subject brightness is low.

[Effect]

According to the above configuration, when an output of a predetermined level or higher is obtained from the infrared light sensor, it can be determined that the light source illuminating the subject is not a fluorescent lamp.

Further, in this case, normal white balance adjustment is performed according to the output from the visible light sensor.

On the other hand, when the output from the infrared light sensor does not reach a predetermined level, it is determined that the subject is illuminated by a fluorescent lamp, and the white balance adjustment is switched to the fluorescent lamp mode.

In addition, the output from the visible light sensor or the photometric sensor for exposure control is also supplied to the determination means, and this output is compared with the output from the infrared light sensor to identify the fluorescent lamp. It is now possible to determine that the output from the infrared light sensor has not reached a predetermined level because the light is low to begin with, and this can prevent the white balance adjustment device from being incorrectly set to fluorescent light mode during low illumination. It becomes like this.

An embodiment of the present invention will be described below with reference to the drawings.

(Example) In FIG. 2 showing the external appearance of an electronic camera embodying the present invention, a photographing lens 11 is provided on the front side of a camera body 10 of the electronic camera, and an image of a subject 12 can be focused manually. A sensor unit 13 is provided above the photographic lens 11.The sensor unit 13 includes a diffuser plate 14, a blue sensor 16, a red sensor 17, and an infrared sensor 18 arranged behind the diffuser plate 14. It consists of

As shown in FIG.
A blue transmission filter 16b, a red transmission filter 17b, and an infrared transmission filter 18b are arranged in front of the filter 18a, respectively. In this case, each color filter has a spectral transmittance characteristic as shown in FIG. 4, where the solid line is the blue transmission filter 16b, the broken line is the red transmission filter 17b, and the dashed line is the infrared transmission filter. The characteristics of 18b are shown respectively.

Furthermore, infrared light cut filters 16c and 17c having spectral transmittance characteristics as shown in FIG. 5 are provided in front of the blue transmission filter 16b and the red transmission filter 17b, respectively. This is because, as shown in FIG. 4, the blue filter and red transmission filter 17b absorb almost no infrared light, so that accurate detection can be performed by cutting off the infrared light.

These sensors 16 to 18 receive light from the shadow range including the subject 12 and its surroundings through the diffuser plate 14, and output signals proportional to the amount of received blue light, red light, and infrared light, respectively. The viewing angle of the shadow lens 11 is usually about 15° to 60″ depending on its focal length, whereas the receiving angle of the sensor unit 13 is about 9° to prevent color balance.
It is set to about 0°.

As shown in FIG. 1, the optical axis 1 behind the photographic lens 11
A diaphragm 21 and a beam splinter 22 are provided on the aperture 9 . The light that has passed through the photographic lens 11 passes through the aperture 21 in the open state, and then enters the beam splitter 22.
A part of the light is incident on the AE light receiving section 24 via the lens 23. The AE light receiving section 24 sends a photoelectric signal according to the amount of incident light to the exposure control device 26. The exposure control device 26 determines the exposure at the time of sharp contrast based on this photoelectric signal, and determines the aperture diameter of the diaphragm 21 and the opening time of the shutter 27.

The light passing through the beam splitter 22 passes through the lens 28
is sent to the movable mirror 29 via. The movable mirror 29 in the illustrated lowered position forms an image of the incident light on the focusing glass 3. The subject image formed on the focusing glass 31 is formed by a well-known pentaprism 32. Eyepiece lens 3
3 through the viewfinder. When the shutter 27 is opened after the movable mirror 29 is moved to the raised position by operating the shutter button, a subject image is formed on the photocathode of the imaging unit 34 and imaging is performed.

A shutter 27 is provided between the movable mirror 29 and the imaging unit 340. The shutter 27 opens and closes in response to a control signal from the exposure control device 26 when the shutter button is operated. The imaging unit 34 consists of a filter face plate in which filters that transmit blue, green, and red are arranged in a mosaic pattern, and a COD image sensor placed behind the filter face plate.The photoelectric signal obtained by photoelectric conversion here is processed. is supplied to circuit 36. The process circuit 36 performs processing such as amplification, nine-color demodulation, and gamma correction on the photoelectric signal from the imaging unit 34, and outputs primary color signals R, B and a luminance signal Y. Primary color signals R and B are each sent to amplifier 3.
7.38, the luminance signal Y is directly supplied to the video signal processing circuit 39, where matrix calculation and color encoding are performed, and the luminance signal Y is sent to the recording device 41 as a standard color video signal such as the NTSC system. supplied to The recording device 41 records the sent video signal on a video floppy.

On the other hand, the blue sensor 16 of the sensor section 13. red sensor 17
The output signal from the color temperature detection circuit 42 is supplied to the color temperature detection circuit 42. The color temperature detection circuit 42 includes a blue sensor 16 and a red sensor 17.
It is for calculating a color temperature signal based on each output signal from the determination circuit 44, and operates in either the normal mode or the fluorescent lamp mode depending on the presence or absence of an identification signal from the determination circuit 44, which will be described later. When this color temperature detection circuit 42 operates in the normal mode, the blue sensor 16 and the red sensor 1
The levels of the output signals from 7 are immediately compared to calculate a color temperature signal. In addition, when operating in the fluorescent lamp mode, in response to temporal fluctuations in the output signals from the blue sensor 16 and the red sensor I7, each output signal is integrated for a certain period of time and then compared to obtain a color temperature signal. Calculate.

The color temperature signal thus obtained is sent to the white balance correction control circuit 43. The white balance correction control circuit 43 supplies correction control signals for blue and red to the amplifiers 37 and 38, respectively, in response to the color temperature signal. Amplifier 37.3
8 adjusts each gain in accordance with the correction control signal, for example, when the color temperature is low, the gain of the primary color signal B is increased and the gain of the primary color signal R is decreased. Therefore, the video signal processing circuit 39 is supplied with a primary color signal corrected according to the color temperature of the illumination light, and a standard color balanced video signal is output to the recording device W41.

The output signal from the infrared sensor 18 is input to the discrimination circuit 44 together with the output signal from the red sensor 17. The discrimination circuit 44 sends a fluorescent lamp discrimination signal to the color temperature detection circuit 42 when the output signal from the red sensor 17 is above a predetermined level and the output signal from the infrared sensor 18 is below a predetermined level. Note that when the output signal from the red sensor 17 is below a predetermined level, the fluorescent lamp identification signal is not output.

The operation of the embodiment configured as described above will be explained below.

When the main switch is turned on, the sensor unit 13 is activated during the framing stage through the eyepiece lens 33, and the blue sensor 16. Red sensor 17. The infrared sensor 18 receives light from the shadow screen and its surroundings through the diffuser plate 14. These output signals are then sent to each color temperature detection circuit 4.
21 discrimination circuit 44.

If the subject is illuminated by daylight (natural light),
Since its spectral energy distribution has the characteristics shown in FIG. 6, the blue sensor 16. Red sensor 17. The output signals from the infrared sensor 18 are each at a predetermined level or higher, and the infrared sensor's daily signal output input to the discrimination circuit 44 is also at a predetermined level or higher. Therefore, in this case, no fluorescent lamp identification signal is output, and the color temperature detection circuit 42 directly compares the signal outputs of the blue sensor 16 and red sensor 17 to detect the color temperature of the illumination light, and detects the color temperature corresponding to this. Outputs temperature signal. The white balance correction control circuit 43 then adjusts the gains of the amplifiers 37 and 38 in response to this color temperature signal.

When the shutter button is pressed, the exposure control device 26
calculates the aperture diameter of the diaphragm 21 and the opening/closing time of the shutter 27 so as to provide an appropriate amount of light according to the output from the AE light receiving section 24. When the movable mirror 29 rises, the aperture 21 is narrowed down to the aperture diameter calculated by the exposure control device 26.
The shutter 27 opens and closes. By opening and closing the shutter 27, the image of the subject is formed on the imaging unit 34, and the imaging unit 34 outputs a photoelectric signal of the subject image. This photoelectric signal forms primary color signals R and B and a luminance signal Y by passing through a process circuit 36. The luminance signal Y is sent as is, and the primary color signals R and B are sent to a video signal processing circuit 39 via amplifiers 37 and 38. Supplied.

At this time, since the gains of the amplifiers 37 and 38 are adjusted according to the color temperature of the illumination light as described above, primary color signals with standard color balance are input to the video signal processing circuit 39. Therefore, the video signal processing circuit 39 outputs a video signal whose color balance has been favorably corrected, and the recording device 41 writes this video signal onto the video floppy.

On the other hand, if the light source illuminating the subject is a fluorescent lamp,
Its spectral energy distribution has characteristics as shown in FIG. That is, energy is radiated in the visible region, but almost no energy is radiated in the wavelength region of 620 nm or more.

In such a case, the blue sensor 16. red sensor 17
Although an output signal with a certain level can be obtained from the infrared sensor 18, almost no signal output can be obtained from the infrared sensor 18. Therefore, while the red sensor 17 supplies a certain level of output signal to the discrimination circuit 44, the infrared sensor 18 supplies almost no output signal.

In this way, when there is an output signal of a predetermined level from the red sensor 17 but no output signal is supplied from the infrared sensor 18, the discrimination circuit 44 generates a fluorescent lamp identification signal and inputs this to the color temperature detection circuit 42. do. As a result, the color temperature detection circuit 42 operates in fluorescent lamp mode, and the blue filter 1
6. After evaluating the output signal from the red filter 17 as being due to light from a fluorescent lamp, the color temperature is detected, and the color temperature signal is sent to the white balance correction control circuit 43.

The white balance correction control circuit 43 supplies the amplifiers 37 and 38 with a correction control signal for adjusting the bluish illumination light of the fluorescent lamp to light with a standard color temperature. Therefore, even in this case, recording can be performed using a video signal with standard color balance. It is also possible to supply the thus generated fluorescent lamp identification signal to the exposure control circuit 26, thereby opening and closing the shutter 27 at a shutter speed for fluorescent lamps that is slower than 1150 seconds, for example. It is.

Note that if the red sensor 17 does not supply a signal output of a predetermined level or higher to the discrimination circuit 44, it means that the amount of light on the subject is low. No identification signal is output. In such a state, it is often impossible to obtain a high-quality image due to insufficient light quantity, so it is preferable to issue a warning regarding insufficient light quantity.

The illustrated embodiment has been described above, but in addition to providing the infrared sensor 18 on the same chip as the visible light receiving sensor consisting of the blue sensor 1G and the red sensor I7, the infrared sensor 18 is provided on a separate chip. It may be formed on top. Further, one or both of the visible light sensor and the infrared sensor may be placed not at a position where external light is received, but at a position where the light passing through the photographing lens II is received, such as a position where the AE light receiving section 24 is provided. It is also possible to provide the

In addition, in the above example, to identify light from a fluorescent lamp, infrared light with a wavelength of 700 nm or more is compared with visible light, but the amount of light before and after 620 nm is compared. It is also possible to identify that the light is from a fluorescent lamp based on the ratio of .

That is, as shown in FIG. 8, a sensor section is composed of a blue sensor 50, a yellow sensor 51, and a red sensor 52,
Photoreceptors 50a and 51 of the blue sensor 50 and yellow sensor 51
Transmission filters 50b and 51b of each color are placed in front of the sensor 52, while a red and infrared transmission filter 52b that transmits only light with a wavelength of 620 nm or more is placed in front of the photoreceptor 52a of the red sensor 52. Deploy. Then, an infrared light cut filter 53 is integrally attached to the front surface of each of these filters 50b to 52b.

As a result, the red sensor 52 has a wavelength of 620 nm or more.
Only light of nm or less is received, and the total spectral sensitivity characteristics of each sensor are as shown in FIG.

In this case, the solid line in the figure indicates the blue sensor 50. The broken line is the red sensor 52. - The dashed dotted lines indicate the characteristics of the yellow sensor 51, respectively.

Then, the color temperature of the object is detected from the output values of the blue sensor 50 and yellow sensor 51, and it is determined whether the light is from a fluorescent lamp or not from the ratio of the output values of the yellow sensor 51 and red sensor 52.

The configuration as described above has the advantage that manufacturing of the sensor section is easier than in the case of the embodiment shown above.

〔Effect of the invention〕

As explained in detail above, the fluorescent lamp identification device of the present invention uses a light receiving section that has sensitivity characteristics in a wavelength region of 620 nm or more to determine whether or not environmental light is caused by fluorescent lamp illumination. It makes it possible to distinguish. therefore,
Highly reliable detection can be performed not only for ordinary fluorescent lamps but also for high frequency type fluorescent lamps.

4. Furthermore, since the white balance is adjusted based on this detection, there is a special effect in that a high-quality reproduced image with good color reproducibility can always be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram schematically showing an electronic camera according to the present invention. FIG. 2 is an external view of the electronic camera shown in FIG. 1. FIG. 3 is a configuration diagram showing details of the sensor section according to the embodiment. FIG. 4 is a graph showing the spectral transmittance characteristics of the color filters used in the examples. FIG. 5 is a graph showing the spectral transmittance characteristics of the infrared light cut filter. FIG. 6 is a graph showing the energy distribution of natural light. FIG. 7 is a graph showing the energy distribution of fluorescent lamps. FIG. 8 is a configuration diagram showing details of a sensor section according to another embodiment. FIG. 9 is a graph showing the total spectral sensitivity characteristics of each sensor according to another example. 10 ・ 11 ・ 16 ・ l 7 ・ 18 ・ 21 ・ 24 ・ 26 ・ 27 ・ 29 ・ 32 ・ 43 ・ 44 ・ Camera body I Darkest lens Blue sensor Red sensor Red sensor Infrared sensor Aperture AE light receiving unit Exposure control device Shutter Movable mirror Pentaprism white balance correction circuit discrimination circuit. Fig. 5 (nm) Fig. 3 (nm) Fig. 4 (nm) Fig. 6 (nm) Fig. 6 (nm)

Claims (3)

[Claims] (1) A visible light sensor that receives visible light contained in the shooting screen or light from the surroundings including the shooting screen, an infrared light sensor that receives light with a wavelength of 620 nm or more among the above light, and this infrared light A fluorescent lamp identification device characterized by comprising: a determination unit for determining whether or not the light is caused by illumination of a fluorescent lamp based on an output from a sensor. (2) a visible light sensor that receives visible light contained in the shooting screen or light from the surroundings including the shooting screen, an infrared light sensor that receives light with a wavelength of 620 nm or more among the light, and the visible light sensor a correction means for detecting a color temperature based on the output of the infrared light sensor and outputting a color balance correction signal according to the color temperature; and a determining means for identifying the light, and when the determining means identifies that the light is caused by illumination of a fluorescent lamp, the correcting means is operated in a fluorescent lamp mode. Balance adjustment device. (3) The determining means compares the output from the visible light sensor or the photometric sensor for exposure control with the output from the infrared light sensor to determine whether the light is due to illumination from a fluorescent lamp. A white balance adjusting device according to claim 1 or 2, characterized in that the white balance adjusting device identifies: