JPS6286992A - Video camera and exchange lens - Google Patents

Abstract

PURPOSE:To adjust completely a white balance at every lens to be used by controlling the white balance based upon two pieces of information stored by the first and second memory means. CONSTITUTION:A ROM 9 accommodates data CR/G and CB/G to show the photographing system spectral characteristic in a camera main body. A photographing lens 1 stores the color information equivalent to the spectral characteristics of the photographing lens 1. A sensor 5 is the one detecting the color temperature, and arranged so as to make average and receive the light around the photographing device through an achromatic color filter. A system controller 6 outputs control voltage values DR/G and DB/G of the digital value to control the gain of an R amplifier 3 and a B amplifier 4 based upon the data sent from the lens 1, the ROM 9 in the camera and a sensor 5 for the white balance. A signal processing system 8 makes signals R', G and B' in which the color balance is adjusted by the R amplifier and the B amplifier into the prescribed signal.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a video camera equipped with an adjustment means for adjusting the white balance of a color imaging signal, and an interchangeable lens that is detachable from the video camera.

<Conventional technology> Conventionally, in video cameras and the like, the white balance of a color image signal is determined by setting the most standard spectral characteristics of a commonly used lens, and then adjusting the white balance based on the set spectral characteristics and the subject. The color temperature has been adjusted based on the color temperature information of the light.

<Problems to be solved by the invention> However, in conventional video cameras with interchangeable lenses, the spectral characteristics differ depending on the lens used. Even when adjusted, the spectral characteristics differ greatly from the standard lens depending on the interchangeable lens actually used, and the white balance cannot be properly adjusted even for the same subject.

By the way, in the imaging system of a video camera, for example, I
In the output of the R lot filter or image sensor,
Although an optical low-pass filter and a color filter are provided in front of the image sensor to prevent the occurrence of folding distortion, the spectral characteristics of such filters are not ideal. For example, it is necessary to compensate for the spectral characteristics of the video camera's imaging system due to reasons such as an IR cut filter cutting out not only the infrared light component but also the red light component of the incident light. Ta.

The present invention eliminates the above-mentioned drawbacks and provides an interchangeable lens (video camera) and such (
The aim is to provide interchangeable lenses suitable for video cameras.

<Means for Solving the Problems> In order to achieve such an object, the first invention of the present application is such that the photographing lens is replaceable, and the light flux incident through the photographing lens and the imaging system of the camera body is In a video camera that converts into an electrical signal, the photographing lens has a first storage means for storing information according to the spectral characteristics peculiar to the lens, and the camera body stores information according to the spectral characteristics of the imaging system of the camera body. a second storage means for storing the first . The present invention is characterized by comprising means for reading information stored in the second storage means, and controlling white balance based on the two pieces of read information.

Further, the second invention of the present application is an interchangeable lens that can be attached to and removed from a video camera, and is provided with a storage means capable of reading out information according to spectral characteristics specific to only the imaging lens, which does not depend on the imaging system of the camera body. It is characterized by

<Function> A first storage means for storing information corresponding to the spectral characteristics of the lens provided on the interchangeable lens side, and a second storage means for storing information corresponding to the spectral characteristics of the imaging system of the camera body provided on the camera body side.
The storage means is read out, and the white balance of the color imaging signal is controlled by the white balance control means in accordance with the read output. Therefore, regardless of the type of interchangeable lens used or the imaging system of the camera body,
Good white balance adjustment can be performed.

<Embodiment> FIG. 1 is a block diagram of a video camera according to an embodiment of the present invention. In FIG. 1, 1 is a photographing lens that stores color information corresponding to the spectral characteristics of the photographic lens, 20 is an image sensor that converts an image incident through the photographic lens 1 into an electrical signal, and 3 and 4 are image sensors 2, respectively. Red light output from
The R amplifier and B amplifier that amplify the blue signal, and 5 are automatic tracking white balance sensors that detect the color temperature of the light source, and this sensor averages the light surrounding the imaging device through an achromatic filter. BE is arranged to receive light. 6 is a digital control voltage value D R/G・D' that controls the gain of the R amplifier 3B amplifier 4 based on the data sent from the lens 1, the ROM 9 in the camera, and the white balance sensor 5. System controller that outputs B7a. 7 represents the digital control voltage values DR/G and DB/G obtained by the system controller 6 as an analog voltage yR7e.

■DD/A converter that converts to B/G. 8 is the signal R' whose color balance has been adjusted by ~R amplifier and B amplifier,
This is a signal processing system that converts G and B' into predetermined signals. 9
is data cR/ that indicates the spectral characteristics of the imaging system within the camera body.
This is a ROM that stores G and CB7a.

Next, FIG. 2 is a block diagram of the photographing lens 1 and the camera body 2 for explaining a communication method between the photographing lens 1 and the camera body 2 in the embodiment shown in FIG. In the figure, C1 is the camera's microcomputer, C2 is the main interface, C21 is the power output terminal, and C22 is the main interface.
is the data terminal, C23 is the PG terminal, and C24 is the G terminal.
This is an ND terminal. C3 is a ROM that stores the main microcomputer program and information indicating the spectral characteristics of the imaging system of the camera body, which will be described later.C4 is a power supply unit, and C5 drives a disk provided in the camera body 2 for recording images. C6 is a photometry system, and C7 is a distance measurement system. Further, the photographing lens 1 is removably attached to the camera body 2. Ll is the lens microcomputer, L2 is the lens interface, L21 is the power supply terminal, L22 is the data terminal, L23 is the bus terminal, L24 is the GND terminal, L3 stores various information of the lens 1, which will be described later, and the program of the sub-microcomputer. ROM that is being used.

L4 is an aperture drive system, L5 is a focus drive system, and L6 is a zoom drive system.

Next, detailed information about the lens 1 stored in the ROML 3 of the photographic lens 1 will be explained using FIG. 3. Third
In the figure, data terminal C2 is connected from camera 2 to photographing lens 1.
2, the command sent via L22, the code of the command, the content of the command, the number of bytes of data sent from the photographing lens 1, and the type of data assigned to the byte. Note that the data indicated by 1←'' in the data content column indicates that the data is the same as the content shown in the content column.The content read by the command indicated as Te5t color is the spectral spectrum of the photographing lens. It is composed of 2-byte data indicating L/G, LB/(B from the ratio of R1G and B of the amount of light transmitted through the lens. Also, the content read by the data command is shown as Te5t Loss. This data indicates the transmittance of the lens.The contents read by the command shown as Treat ID include the lens manufacturer, type,
This is data indicating a function, and consists of seven bytes in total, with several bytes appropriately allocated to each.

Here, the data read by Treat color will be described in more detail.

The data read by 'Te5t color' is shown below. That is, here, cr, cg, and cb are ■ (S): Spectral intensity of standard light source τL (λ): Spectral transmittance of photographing lens 1 τ'; (λ):
The spectral transmittance of the photographing lens 1 defined as a standard is the transmittance of a red filter, the transmittance of a green filter when j is set to g, and the transmittance of a blue filter when jvb is set.

When (j=r+Lb) It is.

In other words, such data cr, cg, and cb are determined as standards for the color separation filters provided on the photographic lens l and the camera body 2 when the luminous flux emitted from a standard white light source is observed through the photographic lens l. This is data showing the energy m of light obtained through a filter with spectral characteristics having a transmittance as a spectral transmittance.

Further, data Cr/, cg/, and cb/ are spectral transmittances when a standard lens is used instead of the above-mentioned photographic lens 1.

Therefore, the data LR/G, LB/G obtained by executing Te5t color can be expressed as the transmittance ratio R7G, B7a when using the standard lens. The data does not take into account the spectral characteristics of the camera body, but only the spectral characteristics of the photographic lens 1.

Next, information on the spectral characteristics of the camera body imaging system stored in the ROM 9 of the camera body 2 will be explained.

Using the data LR//G and LB/G indicating the spectral characteristics of the photographing lens l, which are not stored in the photographic lens 1 described above, the spectral characteristics of the photographic lens 1 and the sensitivity of the imaging system of the camera body and the image sensor are included. Data showing the overall pore spectral characteristics described below </Q>',<B/
In order to obtain e >', data C/G and CB/G shown by the following formulas are stored in the ROM 9 of the camera body 2, and the spectral characteristics of the photographing lens 1 and the imaging system of the camera body and The comprehensive spectral characteristics </G>' and <B/(3>') including the sensitivity of the image sensor are expressed as follows.

Here, "r + Cg + Cb is R (λ): Spectral reflectance factor of the subject defined as standard (λ
): Spectral intensity of standard light source τL (λ): Spectral transmittance of photographing lens 1 τ′I, (λ)
: Spectral transmittance τ of the lens defined as standard? (λ)::
Spectral transmittance τj (λ) of various filters attached to the camera body, excluding color separation filters such as IR clot filters and low-pass filters: Spectral transmittance of RGB color separation filters (red if j is r) When j is set to g, the transmittance of the green filter is 1, and when j is set to b, the transmittance of the blue filter is 1.

When S(λ) is the spectral sensitivity of the image sensor (e.g., image sensor tube, solid-state image sensor) in the camera body, then 7A. (j=゛・g・b) That is, such data cr, Cg, c4. C8 When a white object defined as a standard is illuminated with a light beam emitted from a white light source defined as a standard, the photographing lens 1, the imaging system of the camera body 2, that is, the IR set filter,
This is the RGB output obtained from the image sensor through various filters such as a low-pass filter and an RGB color separation filter.

Furthermore, the data Cr' + C'g', Cb' are the R, G,
This is the B output.

Therefore, the overall spectral characteristic <R/G><''/G>' including lens 1 and camera body 2 is the RGB IOB power /G obtained when using the standard lens.

B obtained when using photographic lens 1 for B<a This is the ratio of RGB output.

I G As mentioned above, such data 〈/G〉'〈B/G〉' is data that takes into consideration the spectral characteristics including the photographic lens 1 and the imaging system and image sensor in the camera body 1.

By the way, when storing the information C/G, C/(3) indicating the spectral characteristics of the imaging system and the image sensor of the camera body 2 in the ROM 9 of the camera body 2, it will be understood from the above explanation. It is necessary to store information corresponding to each lens used.

Therefore, in this embodiment, C/(3, CB/G corresponding to several types of photographic lenses 2 are stored in the ROM 9 of the camera body 2 in advance, and the type of photographic lens is determined from the photographic lens 1 on the camera body 2 side. The data shown in the above Te5
t ID and RO for such data.
Several types of RB R stored in M9
CB/G is selected from similar C/G, C/(3 to 1 type of C/(3°).

In this way, several types of C/G and CB/(3 to 1 type of C/G) are stored in the ROM 9 depending on the type of lens.
, C"/(3), the information on the comprehensive spectral characteristics described above is stored in the ROM 9 in the camera body.
The storage capacity can be reduced compared to the case of storing <B/Q>'. In other words, <R/G>'<''/(3>' varies greatly depending on the type of lens, so <R/Q>
If you try to memorize '<''/G>', it is necessary to memorize the data for all interchangeable lenses, so you will inevitably need a large memory capacity, but C
70. Since the value of CB/G is represented by one value for multiple types of interchangeable lenses, it does not require a very large storage capacity.

Next, the commands and data shown in Figure 3 are sent to the camera body 2.
The order in which data is exchanged between the camera and the lens 1 will be explained using FIGS. 4 and 5. FIG. 4 is a flowchart executed by the microcomputer C1 of the camera body 2, and FIG. 5 is a flowchart executed by the microcomputer L1 of the lens I.

First, the operation of the camera body 2 starts, and when the flow starts from the step shown in Figure 4 +0, Figure 4 +1 is executed and one of the commands shown in Figure 3 is sent to the camera body 2 sent from to the lens.

On the other hand, when the operation of the lens 1 is started, the flow starts from step 0 shown in FIG. 5, and ≠1 is executed. The step shown in Figure 5 +1 determines whether a command is sent from the camera body 2 to the lens 1, repeats the loop when no command is sent, and goes to +2 when a command is sent. move on. Therefore, when the operation of the camera body 2 is started and the process 111-1 in FIG. Proceed to. Lens 2 determines whether the transmitted command is an executable command in Figure 5+2, and if it is an executable command, it goes to Figure 5+3, and if it is not an executable command, it goes to Figure 5+4. move on.

Here, FIG. 5-4+3 is a step in which the command sent from the camera body 2 to the lens 1 is sent as is (return command) from the lens 1 to the camera body 2. Here the fifth
After executing step 3 in Figure 3, lens 1 executes the command (
(Fig. 5, S5) Next, the operation proceeds as in sending the data specified by the command to the camera 2 (Fig. 51, S5). Further, +4 in FIG. 5 is a step of transmitting data indicating a "command error" to the camera 2. In other words, if the command sent from camera body 2 to lens 1 is an executable command, lens 1 transmits the transmitted command from lens 1 to camera body 2 as is. If the command that was not sent from the camera body 2 to the lens 1 is a command that cannot be executed, the lens 1 sends a "command error" to the camera 2 indicating that the transmitted command cannot be executed. It shows the flow. In this state, as shown in FIG. 4, the camera body 2 is in a state to receive commands transmitted from the lens 1 as shown in FIG. By executing the steps in Figure 4, data transmitted from the lens 1 to the camera body 2 is received.

Next, as shown in FIG. 4 413, the camera body 2 transmits data from the lens 1 to the camera body 2 as shown in FIG.
It is determined whether the command matches the command sent to lens 1. If they match, the camera body 2 receives the next transmitted data and performs the operation corresponding to the data, as shown in Figure 4+4, and the flow ends; however, if they do not match, The flow moves from 43 to 45 in FIG.
At +3 in Figure 4, it is determined whether the data sent from lens 1 to camera 2 is data indicating "6 command error".If the sent data is determined to be "0 command error", the flow The program returns to FIG. 4+1 and the same command is selected. If a "command error" cannot be clearly determined in Figure 4-5, either the command sent from camera 2 to lens 1 was sent to lens 1 by mistake, or the data sent from lens 1 to camera 2 was incorrectly sent to camera 2. Either way, it is an error on the transmission path, so the flow stops there.

Here, the data of L/(3,LB/G, which represents the spectral characteristics of the lens transmitted from lens 1 to camera 2 by the method explained using FIGS. 2 to 5, is shown in FIG. 1. The data sent to the system controller 6 is further multiplied by data C/G and CB/G read out from the ROM 9 according to the data ID indicating the type of lens 1, and then sent from the white balance sensor 5. Data W1/G, WB/
The control voltage value V/
G.

(2) The image is converted to R//G, and the white balance is corrected taking into account the spectral characteristics of the lens.

Therefore, according to this embodiment, the white balance can always be adjusted appropriately regardless of the spectral characteristics of the lens.

By the way, in the method shown in FIG. 1 described above, the R amplifier 3,
If the control voltage value that controls the gain of the B amplifier 4 is varied over a wide range, the gain of the R amplifier 3°B7'4 loses linearity with respect to the control voltage value, that is, as shown in FIG. As shown in , R with respect to the control voltage
The gains of the amplifiers and B amplifiers tend to saturate with respect to the control voltage value, and due to this saturation, the gains of the R amplifiers and B amplifiers differ from the gains for adjusting a proper white balance and begin to contain errors. As a result, the disadvantage is that the white balance is disrupted.

In order to eliminate this drawback, the system controller 6 must transmit lens spectral characteristic information L from the lens 1.
R
Amplifier 3. Calculate the gain in the B amplifier 4 and obtain the calculated gain R/G'.

B/G' to R amplifier 3. The control voltage value V/(3, VR/(3) may be converted by considering the characteristics shown in FIG. 6 of the B amplifier 4. The configuration of the system controller 6 having such a function will be explained using FIG. 7. In Fig. 7, 6-A is the information L/(3
, LB/G and information CR/G read from ROM9
, CB10 and data WR/WB/Qt transmitted from the white balance sensor 5, respectively. 6-B is adder circuit 6
- From the data calculated at A, R amplifier 3°B amplifier 4
This is a converter that converts a control voltage value into a digital value corresponding to the control voltage-gain characteristic of the control voltage.

As described above, the R amplifier 3. A control voltage value that takes into consideration the control voltage-gain characteristics of the B amplifier 4 can be obtained.

By the way, according to the above embodiment, it is possible to perform white balance adjustment that is not affected by the spectral characteristics of the lens, but depending on the lens, the amount of correction that supplements the spectral characteristics of the lens can be adjusted depending on the color temperature of the light source. It has to change.

This will be explained using FIG. 8. In FIG. 8, light source≠1. ≠2 indicates the spectrum distribution of light sources with different color temperatures, R filter and G filter indicate the transmission characteristics of the red filter and green filter provided in front of the sensor for white balance, and reference lens A, lens +1.
≠2 indicates the spectral characteristics of the lens. For example,
A lens with spectral characteristics having almost the same distribution as the reference lens A, such as Lens +1 shown in Figure 8, requires a different amount of correction depending on the light source compared to the reference lens (a lens that does not require correction of the spectral characteristics of the lens). I don't.

In other words, the correction amount for light source +1 and light source 1 shown in FIG.
The amount of correction for ll12 does not change much. However, in the case of lens≠2, the sensitivity on the short wavelength side is extremely low compared to the reference lens, so the amount of correction differs depending on the light source +1 or 4N2. In other words, for a light source +1 with a low color temperature, the amount of correction of the red component R with respect to the green component G may be small, but for a light source ≠2 with a high color temperature, the amount of correction must be increased.

My suggestion is that the lens +2 shown in Figure 8 has a low color temperature.
Light source 1, which is a reddish light source, has lower sensitivity to light source 4-2, which is a bluish light source with a high color temperature. It is necessary to increase the value of the red light for .

Therefore, an embodiment of correcting the white balance adjustment for the lens shown at +2 in FIG. 8 will be described with reference to FIG. 9.

In the embodiment shown in FIG. 9, along with the data LR/LB/G from the lens 1, a correction coefficient α for correcting the data from the lens 1 is sent to the camera body 2 according to the color temperature of the light source. transmitting the data LR/G,
Proper whiteness can be achieved under any color temperature light source using LB/G, correction coefficient α, data WR/WB/GG= sent from the white balance sensor, and data CR/CB/Gt read from ROM9. The system controller 6 that performs balance adjustment will be explained. Figure 9 shows the system controller shown in Figure 7.
6 is a block diagram of another embodiment of the controller 6. FIG.

In FIG. 9, 6-C indicates the spectral characteristic information LR/G, LB/(data CR/G, CB/G that can be read out from the 3SROM 9) from the lens 1, the correction coefficient α, and the white balance sensor. This block derives the control voltage of the R amplifier from the output WR7WB/Gt of 5.The control signal R/G'ν obtained in this block
The value of B/G' is corrected depending on the difference in color temperature of the light source, and is expressed by the following (6).

Here, as mentioned above, WR/WB/G is the color temperature data of the light source obtained from the sensor for white balance T. For example, W"/G=4 dB, LR/G, C"/G= 1
If dB α=0.05, the part in parentheses in equation (6) is W/G・α+LR/G−CB
/G=4X0.05+1 =1.2 dB, so G' becomes 5.2 dB.

In other words, in this case, R//G', which is the color temperature correction amount including lens correction, is in addition to the original lens correction amount of 1 dB.
A G correction amount (WR//GXα = 0.2 dB) that depends on the color temperature expressed by WR/WB/G is added, and from this, the correction amount depends on the color temperature of the light source at the time of shooting. It can be seen that further adjustments have been made.

6-B is an exchanger similar to the converter shown in FIG. With the correction blocks 6-C and 6-B, it is possible to correct the color of the lens according to the difference in color temperature of the light source at the time of photographing, as described above.

According to the above-described embodiment, the white balance can always be adjusted appropriately even if the color temperature of the photographing light source is different.

In this embodiment, the MLL flat means ROMC5 is used for electrically storing the spectral characteristics of the photographing lens, and the ROM9 is used as the storage means for electrically storing the spectral characteristics of the imaging system on the camera side. It may also be a magnetic memory. Furthermore, although the microcomputer C1 and interface C2 shown in FIG. 2 which operate according to the flow shown in FIG. 4 are used as means for reading data stored in the storage means, other hardware logic may be used.

Memorize LB/G, CR/G, CB on camera body 2
/G is stored, but all such data is expressed as an integral value as shown in the above explanation.

Instead of storing the data as such an integral value (2)
The data may be stored as a function to be integrated as shown in equation (5), and then integrated after being multiplied by this function when controlling the white balance on the camera body side. In this case, the white balance can be controlled more accurately.

<Effects of the Invention> As explained above, according to the first invention of the present application, in a video camera using an interchangeable lens, the interchangeable lens has a first lens that electrically stores information corresponding to the spectral characteristics specific to the lens. The video camera has a second storage means for storing information corresponding to the spectral characteristics of the imaging system of the camera body, and the first. A readout means for electrically reading out the information stored in the second storage means and a means for adjusting the white balance based on the two pieces of read information are provided, so that a perfect white balance can be achieved for each lens used. Adjustments can be made. According to the second invention of the present application, the means for adjusting the white balance within the video camera includes a memory that stores information indicating spectral characteristics unique to an interchangeable lens that is independent of the imaging system of the camera body. Since the means is provided, there is no need to re-adjust the white balance inside the video camera every time the lens is replaced, and the operability is improved.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a video camera according to an embodiment of the present invention, and Fig. 2 shows a photographic lens 1 for explaining a communication method between the photographic lens 1 and the camera body 2 in the embodiment shown in Fig. 1.
A block diagram of the camera body 2 and the camera body 2, and Figure 3 shows the photographing lens 1.
, a diagram showing commands and data exchanged with the camera body 2, FIG. 4 is a flowchart executed by the microcomputer C1 in the camera body 2, and FIG. 5 is a flowchart executed by the microcomputer L1 in the photographic lens 1. FIG. 6 is a diagram showing the relationship between the gain and control voltage of the R amplifier 3 and B amplifier 4 shown in FIG. 1, and FIG. FIG. 8 is a block diagram showing the configuration of the system controller 6 that performs control taking into account the characteristics of the light sources 4-1, +2 and the R, G color filter lenses 4P1. +2 spectral characteristics, FIG. 9 is a block diagram showing the configuration of the system controller 6 that performs control in consideration of the spectral characteristics of the filter/lens shown in FIG. 8. 1... Shooting lens 2... Camera body

Claims (2)

[Claims] (1) In a video camera in which the photographing lens is replaceable and converts the incident light flux through the photographing lens and the imaging system of the camera body into an electrical signal, the photographing lens receives information according to the spectral characteristics specific to the lens. The camera body has a first storage means for storing information corresponding to the spectral characteristics of the imaging system of the camera body, and a second storage means for storing information corresponding to the spectral characteristics of the imaging system of the camera body;
A video camera comprising: means for reading information stored in the second storage means; and means for controlling white balance based on the two pieces of read information. (2) An interchangeable lens characterized by comprising a storage means that readably stores information corresponding to spectral characteristics specific to the photographic lens alone, which does not depend on the imaging system of the camera body.